,,aeroplane                             
,,construction                     ,a   
,handbook on the various ,methods and   
,details of ,construction employed in   
the ,building of ,aeroplanes            
,,by                                    
,,sydney ,,camm                         
,,associate ,,fellow ,,royal            
,,aeronautical ,,society                
,illustration                           
,,london                                
,,crosby ,,lockwood ,,and ,,son         
#g1 ,,stationers' ,,hall ,,court1       
,,ludgate ,,hill                        
#aiai                                   
,,printed ,,by                          
,,william ,,clowes ,,and ,,sons1        
,,limited1                              
,,london ,,and ,,beccles4               
,,preface      ,the articles embodied   
with other matter in this book1 were    
intended  as a broad survey of the      
principles and details of modern        
aeroplane  construction1 concerning     
which there is a noticeable deficit     

amongst  existing aeronautical          
literature4    ,they were written at a  
time when specific references to modern 
,british  aircraft were forbidden1 and  
although from a comparative point of    
view this is to be regretted1 the       
details and methods dealt with are1  in 
the author's opinion1 representative of 
those most generally used  in machines  
of present-day design4 ,it is hoped that
 the book will  appeal not only to those
 engaged on the manufacture1 but also to
 those  concerned with the uses of      
aircraft4                               
,s4 ,c4          ,,table ,,of ,,contents
        ,,chapter ,i4                   
,,page    ,,introduction                
#a      ,,chapter ,,ii4      ,,materials
                                  #f    
,,chapter ,,iii4      ,,spars ,,and     
,,struts                          #ah   
,,chapter ,,iv4      ,,plane            
,,construction                          
#cj      ,,chapter ,v4      ,,details   
,,of ,,plane ,,construction             

#dj      ,,chapter ,,vi4                
,,interplane ,,strut ,,connections      
#ea      ,,chapter ,,vii4               
,,wing-,,trussing ,,systems             
#ei      ,,chapter ,,viii4              
,,fuselage ,,construction               
#fg      ,,chapter ,,ix4      ,,fuselage
 ,,fittings                         #gg 
,,chapter ,x4      ,,undercarriage      
,,types                       #hf       
,,chapter ,,xi4      ,,undercarriage    
,,details                     #ic       
,,chapter ,,xii4      ,,control         
,,systems                          #aja 
,,chapter ,,xiii4      ,,wires ,,and    
,,connections                    #ajh   
,,chapter ,,xiv4      ,,engine          
,,mountings                         #aaf
      ,,chapter ,,xv4      ,,erection   
,,and ,,alignment                   #abc
      ,,index                           
#ace          ,,aeroplane ,,construction
          ,,chapter ,i4                 
,,introduction4      ,the purpose of    
this book is to give some indication of 

the principles  and methods of          
construction of modern aeroplanes1 as   
distinct from  those considerations     
pertaining purely to design1 although   
occasional  references to various       
elementary principles of aerodynamics   
have  been found necessary to illustrate
 the why and wherefore of certain       
constructional details4    ,to many the 
aeroplane is a structure of appalling   
flimsiness1 yet the  principle which it 
exemplifies1 that of obtaining the      
maximum strength  for a minimum of      
weight1 constitutes a problem of which  
the solving  is not only an unceasing   
labour1 but one demanding the observance
  of the best engineering procedure4    
,the whole future of aviation1          
commercially or otherwise1 may be said  
to be indissolubly bound up with  the   
development of efficiency2 and whether  
this is to be attained in  improvements 
in aerodynamical qualities1 by the      
discovery of a material  giving a       
greatly enhanced strength to weight     

ratio1 or by progress in  the           
arrangement of the various members of   
the complete structure of the           
aeroplane1 is a matter upon which some  
diversity of opinion exists4  ,however1 
it is certain that the very great       
developments of the last few  years are 
due more to refinements in design rather
 than construction2  and it is          
questionable whether the constructional 
work of the modern  aeroplane has       
developed equally with design1 so that1 
even taking for  granted the            
oft-repeated1 but very doubtful1        
statement that we are  approaching the  
limitations of design1 there is         
certainly plenty of  scope for          
experiment and improvement in the       
constructional principles  of the modern
 aeroplane4      ,standardization of    
,details4    ,whatever may be said for  
the standardization of aeroplane types1 
a scheme which should effect a          
considerable saving in labour and       
material1 and which offers chances of   

success1 would consist in the           
standardization of metal fittings and   
wood components generally1 for in  this 
direction there is certainly great need 
for improvement4 ,taking  as a          
hypothesis the various makes of scouting
 machines1 we find hardly  any two      
details the same4 ,this means that if in
 this country there are  six firms      
producing machines of their own design  
7these figures1 of  course1 being purely
 suppositionary71 there will be six sets
 of detail  drawings1 six sets of jigs1 
templates1 and press tools1 and sundry  
special machine tools4 ,there seems no  
valid reason why many of the  fittings  
for all machines within certain         
dimensions should not be of  standard   
design1 and a brief review of the       
various details which could  be         
standardized without detracting in the  
least from aerodynamical  efficiency    
will indicate the extent to which the   
conserving of labour  could be carried4 
,in the construction of the fuselage1   

the clips  fastening the longerons and  
cross struts could easily be of one     
design1  whatever the make of the       
machine4 ,at present we find some clips 
are  bent up from a stamping and        
attached to the longeron without the    
drilling of the latter2 some built up   
from various parts1 such as             
washer-plates1 duralumin pressings1 and 
bolted through the longeron2  while some
 combine advantages and others the      
disadvantages of both4 ,in  some cases  
the longerons of spruce are spindled out
 for lightening2  in others no spindling
 occurs2 while in a few instances       
hickory or  ash1 with or without        
channelling1 is used4 ,there are the    
interplane  strut attachments1          
stern-post fittings1 control-surface    
hinges1 and  undercarriage attachments1 
all showing great variations1 and in all
  of which the design could be brought  
within reasonable limits4 ,as           
indicating how unnecessary a good deal  
of the variation is1 one may  instance  

the fact that for the swaged streamline1
 or ,r4,a4,f4 wires1  there are at least
 three different terminals in use4      
,although more  difficult of            
achievement1 there is scope for         
improvement in the  different           
arrangements for the fixed gun mounting1
 while a standard  instrument board     
would benefit the pilot4      ,methods  
of ,manufacture4    ,it is fairly well  
known that the output of some firms is  
considerably  better than others1       
although the machines are of the same   
design4  ,although a good many factors  
may contribute to this result1 it  seems
 fairly certain that in some cases the  
methods of manufacture  must be         
superior1 which calls for some system of
 standardizing the  broad principles    
pertaining to manufacturing procedure4  
,under this  arrangement a much better  
estimate of probable output could be    
made4  ,it is also necessary by the fact
 that some firms have been developed    
through the exigencies of war1 and not  

as a result of any great  manufacturing 
ability1 whereas in peace time the spur 
of competition  would force the adoption
 of the most rapid methods of           
production4  ,the creation of a central 
or universal office for the design of   
the  various jigs used in the           
manufacture of aircraft1 with power to  
decide the process of manufacture1      
although a somewhat far-reaching        
reform1 would certainly eliminate a     
number of useless experiments made  by  
the individual constructors1 and would  
also greatly improve the                
interchangeability of the various       
components4 ,in addition1 fresh firms   
to the aviation industry would be at    
once acquainted with the general        
methods of manufacture1 which should be 
of considerable assistance in           
expediting initial output4 ,of course1  
this system would tend rather to        
destroy individual initiative1 in that  
much that is now left to the  skill and 
experience of the workman would be      

predetermined1 although  this would be  
more than compensated for by the        
increased benefits  accruing to the     
,state4 ,jigs designed to produce the   
same work in  different works often     
differ in detail considerably1 and this1
 of  course1 often influences the rate  
of production4 ,as an instance1 in  some
 works elaborate benches are considered 
necessary for the erection  of          
fuselages1 while in others a pair of    
trestles suffices4 ,with this  system of
 unified manufacturing procedure extreme
 regard would have to  be paid1 in the  
design of various jigs and fixtures1 to 
adaptability  for modifications in      
design4 ,otherwise the various          
alterations which  are bound to occur   
would result in an unnecessary          
expenditure on  fresh jigs4 ,it is      
somewhat unfortunate that in the general
 design  of an aeroplane1 in numerous   
cases1 far too little regard is paid  to
 considerations of ease of manufacture1 
and this is frequently  responsible for 

the many changes in design after a      
contract has been  started4 ,under an   
ideal system of standardization1 the    
requirements  of manufacture would      
necessitate consideration in the design 
of the  constructional details4         
,metal ,construction4    ,the question  
of the aircraft materials of the future 
is not so much  a problem as a matter of
 gradual evolution4 ,in view of the     
dwindling  supplies of suitable timber1 
it certainly seems more than probable   
that  some form of metal construction   
will one day constitute the structure   
of the aeroplane4 ,the manufacture of   
the various components in wood  does not
 necessitate an extensive plant1 the    
labour necessary is  comparatively cheap
 and easily available1 and moreover the 
transitory  nature of the whole         
business1 and the ease with which       
essential changes  in type can be made  
without the wholesale scrapping of the  
expensive  jigs associated with the use 
of steel1 all strengthen the case in    

favour of wood4 ,the conclusion of      
hostilities would introduce another     
state of affairs1 and it is conceivable 
that the various types will  then be    
standardized for different purposes1    
which may necessitate  the greater use  
of steel4 ,certainly the advantage of   
steel would be  better realized under   
some system of standardized design1 but 
this  unfortunately is not possible     
while present conditions obtain4 ,the   
advantages of metal as a material       
considered briefly1 are that it  permits
 of design to close limits without the  
allowance of so-called  factors of      
safety1 which are now necessary through 
the great variation  in the strengths of
 wood1 manufacturing procedure would be 
expedited1  while one can reasonably    
expect a greater degree of precision in 
the  finished machine1 due largely to   
the increased facilities for accurate   
manufacture of components which metal   
affords4 ,it is quite possible1 of      
course1 given a uniform grade of steel1 

to design to extremely close  limits    
without fear of collapse2 but the human 
factor in the shape of  fitter1 welder1 
or operator introduces the unknown      
element1 and one  for which some        
allowance must always be made4 ,one     
cannot assert that  any very decided    
indication exists of a trend in modern  
design towards  metal construction1 and 
it is quite possible that this will not 
arrive  until it is rendered imperative 
by reason of the scarcity of timber4    
,the precise composition of the metal is
 rather a controversial matter1  some   
authorities favouring steel1 and others 
some alloy of aluminium1  such as1 for  
instance1 8duralumin40 ,the production  
of a suitable alloy  constitutes a real 
problem and one upon which the ,advisory
 ,committee  for ,aeronautics have      
already made investigations and         
experiments4 ,a  disadvantage with steel
 is that1 although it is quite possible 
to  produce1 say1 a fuselage entirely of
 this material to withstand easily  the 

greatest stress encountered in flying1  
such a structure1 owing to  the thin    
nature of the various components1 would 
suffer damage through  shocks induced by
 rolling over rough ground1 and also by 
handling4 ,in  addition the effects of  
crystallization would require some      
considerable  study4 ,these and other   
reasons indicate that an alloy of       
aluminium1  which for a given weight    
would be considerably more rigid than   
steel1  offers possibilities as a       
material4 ,it might prove advantageous  
to  combine both metals1 using steel for
 the more highly stressed parts1  such  
as1 for instance1 wing spar attachments1
 interplane bracing lugs1  and indeed   
any part where the load to be carried is
 one induced by  tension4    ,the       
foregoing is indicative of some of the  
more important directions  in which     
improvement and development are         
possible1 and certainly ample  scope yet
 exists for the attention of the        
student1 or indeed any one  interested  

in the future of the aviation industry4 
,,chapter ,,ii4    ,,materials4         
,seeing that wood constitutes the       
material for the greater part of  the   
structure of the aeroplane1 that is with
 very few exceptions1  some notes on the
 characteristics and qualities of those 
woods most  commonly used may prove of  
interest4 ,the choice of a suitable wood
  for aircraft construction is a matter 
of some difficulty1 engendered  by the  
variety of considerations of which at   
least some observance is  essential4    
,the fundamental principle of aircraft  
construction1 that of  obtaining the    
maximum strength for a minimum of       
weight1 affords one  standpoint from    
which a particular wood may be regarded1
 but this does  not constitute in itself
 a sufficient reason for its choice4 ,of
 almost  equal importance are such      
considerations as the length and size of
 the  balks obtainable from the log1 the
 total stock available1 the relative    
straightness of grain and freedom from  

knots as well as the durability  of the 
wood4      ,variable ,qualities of      
,wood4    ,the choice is additionally   
complicated by the very great variation 
found in the strength and               
characteristics of trees of exactly the 
same species1 and also of different     
portions cut from the same tree4  ,the  
nature of the site upon which a tree is 
grown exercises a marked  influence upon
 its properties1 while as a general     
rule1 it may be taken  that the greater 
number of annual growth rings per inch1 
the greater  the strength4 ,it is also a
 general rule that up to certain        
diameters1  the timber contained in that
 part of the tree the greatest distance 
from the pith1 or centre1 is the        
stronger4    ,the wood obtained from the
 base of a tree is heavier than that at 
the  top1 and one finds the influence of
 this in the necessity for balancing    
and alternating the different lamin of  
air-screws before gluing4               
,shrinkage4    ,another point1 and one  

which is intimately concerned with the  
proper  seasoning of timber1 is the     
amount of moisture contained in a       
specimen1  and this latter point is of  
some considerable importance1 as not    
only  is a large amount of moisture     
detrimental to the strength values of   
the timber1 but it also renders useless 
any attempt at precision of             
workmanship4 ,it is this very point of  
shrinkage1 which constitutes  the       
greatest bar to the achievement of a    
measure of component  standardization1  
and it is also one of the most serious  
disabilities of  wood as a material for 
aircraft construction4 ,it is now       
necessary in  the production of finished
 parts to make some allowance for       
resultant  shrinkage1 which is a matter 
of guesswork1 and only practicable where
  some time will elapse between the     
finishing of the part and its  erection 
in the complete machine4 ,under present 
conditions1 more often  than not the    
parts are assembled almost immediately  

they are made1  which means that no     
allowance over the actual size is       
possible1 this  being due to the various
 fittings which in the majority of      
machines are  of set dimensions and clip
 or surround the material4    ,as a     
natural sequence shrinkage occurs       
subsequent to the attachment  of the    
fitting1 followed by looseness and loss 
of alignment in the  structure4 ,until  
the proper period for seasoning can     
elapse1 between  the cutting of the tree
 and its conversion into aeroplane      
parts1 it is  difficult to see how this 
disability can be obviated1 although    
latterly  some considerable advances    
have been made with artificial methods  
of  seasoning4 ,the prejudice against   
kiln drying is founded on the belief    
that the strength of the timber is      
reduced1 and that extraneous defects    
are induced4 ,a method which is a       
distinct improvement on those systems1  
using superheated steam and hot air1 is 
now being used with apparently  good    

results4 ,in this system1 steam under   
very low compression is  constantly     
circulated through the timber1 drying   
being effected by a  gradual reduction  
in the humidity of the atmosphere4      
,unreliability of ,tabulated ,tests4    
,the various tables which exist         
indicating the strength1 weight1 and    
characteristics of various woods are of 
very doubtful utility1 in  some cases   
fallacious1 and in nearly all cases far 
too specific4 ,the  foregoing           
enumeration of some of the variations   
existing with wood will  indicate the   
enormous difficulty of obtaining with   
any exactitude a  result representative 
of the species of wood tested1 and which
 could  be regarded as reliable data for
 the calculation of stresses1 or for    
general design4 ,the moisture content of
 timber1 an extremely variable          
quantity1 greatly affects the figures   
relating to the strength and  weight of 
timber1 so that tables indicating the   
properties of woods  should include the 

percentage of moisture contained in the 
examples  tested4 ,again1 certain woods 
possessing relatively high strength     
values1 are frequently short-grained and
 brittle1 and therefore not  so suitable
 as other woods of lower strength       
values1 but of greater  elasticity and  
resiliency4      ,,woods ,,in ,,use4    
,silver ,spruce4    ,the wood most      
extensively used for the main items of  
construction is  silver spruce1 or      
,sitka spruce1 found in great quantities
 in ,british  ,columbia4 ,experience has
 proved this wood pre-eminently suitable
 for  aeroplane construction1 its       
strength-weight ratio is particularly   
good1 it can be 7at least until         
recently7 obtained in long lengths up   
to #cj ft41 and1 moreover1 is           
particularly straight grained and free  
from knots and other defects4 ,there are
 other woods possessing higher  strength
 qualities1 but in most cases their     
value is greatly diminished  by reason  
of the greater weight1 and that only a  

limited portion  straight of grain and  
free from knots is obtainable4 ,the     
weight of  ,sitka spruce varies from #bf
 to #cc lbs4 per cubic foot1 and        
although it  is difficult to give a     
precise figure1 a good average specimen 
fairly  dry would weigh about #bh lbs4  
per cubic foot4 ,some impression of the 
extent to which it enters into the      
construction of the aeroplane will  be  
gathered if the components usually of   
spruce are detailed4 ,for the  main     
spars of the planes spruce is almost    
universally used1 as here  great        
strength for the least weight is of     
extreme importance1 while a             
consideration almost as important is the
 necessity of a good average  length1   
straight grained and free from defects4 
,it is also used for  the webs and      
flanges of the wing ribs1 the leading   
and trailing edges  and wing structure  
generally4 ,the longerons or rails of   
the fuselage  of many machines are      
spruce1 although in this instance ash   

and hickory  are used to a moderate     
extent4 ,the growing practice is to make
 the  front portion of the fuselage of  
ash1 as this is subject to the greater  
stress1 while the tail portion is of    
spruce2 but in a number of cases  the   
latter material is used throughout4 ,the
 cross struts of the  fuselage are      
invariably of spruce1 as well as such   
items as interplane  and undercarriage  
struts and streamline fairings4         
,virginia ,spruce4    ,this is of a     
lower weight per cubic foot than ,sitka 
spruce1 but does  not possess such a    
good strength value1 cannot be obtained 
in such  large pieces1 and is generally 
subject to small knots1 which limit the 
straight-grained lengths procurable4    
,it is distinguishable from ,sitka      
spruce by its whiteness of colour and   
general closeness of grain4             
,norwegian ,spruce4    ,this wood is    
also known as spruce fir and white deal1
 and is grown  principally in ,north    
,europe4 ,selected balks can be obtained

 to weigh no  more than #cj lbs4 per    
cubic foot1 which compares very         
favourably with  silver spruce4 ,it can 
be obtained in average lengths1 but it  
is subject  to the presence of small    
hard knots and streaks of resin1        
although the  writer has seen           
consignments with very few knots4 ,a    
material known  as ,baltic yellow deal  
and ,northern pine is procured from the 
same  source1 and is more durable than  
,norwegian spruce4 ,it is inclined to   
brittleness when dry1 and is heavier    
than white deal1 weighing about  #cf    
lbs4 per cubic foot4 ,the recent        
shortage of silver spruce has led  to   
the employment of ,norwegian spruce for 
items such as fuselage  struts1 hollow  
fairings to tubular struts1 the webs and
 flanges of  the plane ribs1 and        
generally for those components for which
 long  straight-grained lengths are not 
absolutely essential4    ,for fuselage  
struts1 where the chief consideration is
 stiffness1 to  resist the bending      

strain produced by inequalities of      
wiring1 fittings1  etc41 it may actually
 give better results1 being slightly    
more rigid  than silver spruce--at least
 that is the writer's experience of it4 
,in  addition1 very little increase in  
weight would result1 as this wood  can  
be obtained of almost the same weight   
per cubic foot as silver  spruce4 ,the  
defect usually met with in this wood1 of
 knots occurring  at intervals1 would be
 of no great detriment1 the lengths     
needed for  the fuselage struts being   
approximately #c feet and less1 and it  
would  therefore be easily possible to  
procure wood of this length free from   
knots4 ,the other items enumerated are  
of varying lengths1 which1 with  care in
 selection and conversion1 could be     
arranged for4 ,the practical            
application of this would be the        
increased amount of silver spruce       
available for such highly stressed items
 as wing spars1 interplane  struts1 and 
longerons4      ,ash4    ,this wood is  

one of the most valuable of those       
employed1 being  extremely tough and    
resilient4 ,there are two varieties in  
use1 ,english  and ,american1 the former
 being considered the better material4  
,it is  used mainly for longerons1      
undercarriage struts1 and for all kinds 
of bent work4 ,it possesses the quality 
of being readily steamed to             
comparatively sharp curves1 and will    
retain the bend for a considerable      
period4 ,the strength and               
characteristics of ash vary greatly with
 the  climate under which it is grown1  
and it is also much heavier than        
spruce1 the weight per cubic foot       
ranging between #dj and #ej lbs4        
,difficulty is also experienced in      
obtaining lengths greater than #bj  ft41
 and even in lengths up to that figure1 
continuity of grain is  somewhat rare4  
,it is notable that on various ,german  
machines1 ash in  conjunction with a    
species of mahogany is used for the     
lamin of the  air-screw4      ,hickory4 

,hickory1 a species of walnut1 is       
imported from ,new ,zealand and         
,america1  and possesses characteristics
 similar to those of ash4 ,it is        
obtainable  in about the same lengths as
 ash1 but in the writer's experience is 
of greater weight4 ,its chief property  
is extreme resiliency1 which  makes it  
especially suitable for skids1 and it   
has also been used to  a limited extent 
for longerons4 ,it is subject to        
excessive warping in  drying1 is not so 
durable as ash1 and the great difficulty
 experienced  in obtaining              
straight-grained lengths is responsible 
for its waning  popularity4             
,walnut4    ,this wood is almost        
entirely devoted to the making of       
air-screws1  although the dwindling     
supplies and the very short lengths     
obtainable  has practically enforced the
 employment of other woods for this     
purpose4      ,mahogany4    ,the term   
8mahogany0 covers an infinite variety of
 woods1 possessing  widely different    

characteristics1 many of the species    
being quite  unsuitable for the         
requirements of aircraft work4 ,that    
known as  ,honduras mahogany possesses  
the best strength values1 is of medium  
weight1 about #ce lbs4 per cubic foot1  
and is in general use for  airs-crews   
and seaplane floats4 ,it has been used  
on some ,german  machines for such parts
 as rib webs1 but is not really suitable
 for  parts of comparatively small      
section1 such as longerons1 as it is    
inclined to brittleness4 ,it is of      
particular value for seaplane floats    
and the hulls of the flying-boat type of
 machine1 as it is not affected  by     
water4 ,a defect peculiar to ,honduras  
mahogany is the occurrence of  irregular
 fractures across the grain known as    
thunder shakes4 ,although  other        
so-called mahoganies are similar in     
appearance to the ,honduras  variety1 a 
species quite distinct in appearance is 
that known as ,cuban  or ,spanish       
mahogany1 which is of darker colour1 and

 much heavier in  weight1 averaging     
about #ej lbs4 per cubic foot1 which    
latter factor  almost precludes its use 
for aeroplane construction4      ,birch4
    ,one finds very few instances of the
 use of this wood for aeroplane         
details1 although it is used fairly     
extensively in ,america for  air-screw  
construction1 for which it is only      
moderately suited4 ,it  possesses a high
 value of compressive strength across   
the grain1 but is  much affected by     
climatic changes1 and does not take glue
 well4 ,it is  useful for bent work1 and
 might conceivably be used instead of   
ash for  small bent work details4 ,its  
weight is about #dd lbs4 per cubic foot4
      ,poplar4    ,under this name is   
included such woods as ,american        
whitewood1 cotton  wood1 bass wood1 etc4
 ,the wood sold under one or other of   
these names  is generally very soft and 
brittle1 and although of a light nature1
  weighing about #cj lbs4 per cubic foot
 and less1 it is of very little  utility

 for the work under discussion4 ,it has 
been used for minor parts  such as rib  
webs1 and fairings to tubular struts4   
,oregon ,pine4    ,the scarcity of      
silver spruce has led to the adoption of
 the wood known  as ,oregon pine for    
most of the components for which the    
former wood has  hitherto been used4    
,the term 8,oregon pine0 is applied to  
the ,douglas  fir1 one of the largest of
 the fir species1 a length of #bjj ft4  
being  an average4 ,it is altogether    
heavier than silver spruce1 weighing    
about #cd lbs4 per cubic foot1 and also 
differs greatly in appearance1          
possessing a reddish-brown grain1 with  
very distinct annual rings4 ,its        
strength to weight ratios are           
practically equal to those of silver    
spruce1 although in the writer's        
experience it has a tendency towards    
brittleness1 and is not so suitable as  
,sitka spruce for components of  small  
scantling4 ,with some specimens of this 
wood it is noticeable  that the effect  

of drying on freshly sawn lengths for   
longerons1 etc41  is the appearance of  
8shakes0 or cracks1 not previously      
discernible4  ,its appearance generally 
is reminiscent of pitch pine1 for which 
wood  it is sometimes substituted in    
connection with building4      ,other   
,woods4    ,the foregoing constitute    
woods which are in fairly general use   
for one  purpose or another1 there      
being1 of course1 very many other       
varieties1  some of which may be called 
into use with the progress of the       
industry4  ,of the conifer species1     
silver spruce is easily the most        
suitable  timber for aeroplane          
construction1 and one realizes this more
 as the  various substitutes are tried4 
,as an instance1 cypress is straight of 
grain with no very great increase over  
the weight of spruce1 being also  well  
up the table of strengths4 ,it is1      
however1 much too brittle for  the      
various members of small section of     
which an aeroplane is composed1  and    

does not seem to have any extensive     
future for aircraft work4  ,another1 at 
one time much-advertised wood1 is       
,parang1 a species of  mahogany4 ,it has
 been reputed to bend well1 but it      
certainly does not  enter into the      
construction of modern aeroplanes4 ,a   
consignment handled  by the writer some 
years ago and intended for bending1 was 
found to  be exceedingly brittle1 and   
although standing a good load1 fractured
  almost square across the grain1 in a  
manner known colloquially in  the       
workshop as 8carrot-like40 ,the latter  
term is indicative of a  characteristic 
which precludes the use of many woods   
possessing other  physical properties   
especially suitable for aircraft work4  
,multi-ply ,wood4    ,this term is      
applied to the sheets of wood composed  
of a number of  thin layers glued       
together with the grain reversed4 ,as   
the layers are  obtained by rotating the
 tree against cutters in such a manner  
that a  continuous cut is taken from the

 outside almost to the centre1 it is    
possible to get very great widths1 which
 makes it particularly suitable  for    
aircraft work4 ,it is made in varying   
widths up to #d ft41 and in  thickness  
from #a_/bj in4 up to  in41 consisting  
of three1 five1 and  seven layers1      
although the three-ply variety in       
thicknesses up to #c_/af  in4 is more   
commonly used4 ,it is made up in nearly 
all woods1 but those  mostly utilized in
 the aeroplane industry are birch1 ash1 
poplar1 and  satin-walnut1 birch being  
superior by reason of its closeness of  
grain4  ,ash ply-wood in some instances 
tends towards brittleness1 while poplar1
  although exceptionally light1 is very 
soft and only used for minor  parts4    
,satin-walnut is very even in quality   
but is apt to warp4      ,defects in    
,timber4    ,illustration3 ,,fig4       
#a4--;,heart shake4    ,illustration3   
,,fig4 #b4--,star shake4                
,illustration3 ,,fig4 #c4--;,cup shake4 
,perhaps the most common and prolific   

defect encountered with the  use of     
timber is the presence of cracks or     
shakes of different  character1 which   
are due to different causes4 ,fig4 #a   
indicates  a very common form1 known as 
a 8heart shake10 dividing the  timber at
 the centre2 while ,fig4 #b1 a 8star    
shake10 is really a  number of heart    
shakes diverging from the centre4 ,the  
process of  seasoning sometimes results 
in the separation of the annual rings1  
forming cup shakes1 as shown in ,fig4   
#c4 ,it should be understood  that the  
presence of shakes may render useless an
 otherwise  perfect specimen of timber1 
as it frequently happens that in the    
conversion of timber so affected the    
usable portions do not permit  of the   
sizes necessary for such items as wing  
spars and struts4 ,the    ,illustration3
 ,,fig4 #d4--,twisted grain4    defect  
of twisted grain 7,fig4 #d7 is often    
found in ash1 and is caused  by the     
action of the wind when the tree is     
growing1 and renders such  wood of      

limited utility4 ,shrinkage affects all 
timber in varying  degrees1 and its     
effect on boards due to their position  
in the log  is shown by ,fig4 #e1 while 
,fig4 #f indicates the effect of drying 
on a  squared-up section4 ,incidentally 
one may point out that the annual       
rings1 viewed from the end of the       
section1 should be as straight as       
possible1 which would obviate to an     
extent the distortion due to drying  in 
a component subsequent to its finishing4
 ,another defect1 and one  somewhat     
difficult to detect1 is the presence of 
a brownish speckled  tint in the grain4 
,any evidence of this in a specimen     
indicates the  beginning of decay1 and  
is caused by insufficient seasoning and 
lengthy  exposure in a stagnant         
situation4    ,illustration3 ,,fig4     
#e4--,shrinkage of boards due to        
position in log4    ,illustration3      
,,fig4 #f4--;,effect of drying on a     
squared-up section4      ,steel4    ,the
 greater proportion of the various      

fittings employed in the  construction  
of the aeroplane are built up from sheet
 nickel steel1  usually of a low tensile
 strength1 to permit of working in a    
cold  state1 as1 with a higher grade    
steel1 the process of bending to        
template by hand1 in many cases a none  
too careful procedure1 would  result in 
a considerable weakening of the material
 at the bend4  ,in addition1 the        
operation of welding1 which now enters  
into the  construction of a number of   
fittings1 also necessitates a moderate  
grade of steel4 ,a higher class of sheet
 steel1 from #ce to #ej tons  tensile1  
is used for parts subject to stress1    
such as interplane  strut-fittings1     
wiring-lugs1 etc4 ,as a higher grade of 
steel is better  from a                 
strength-for-weight point of view1 its  
employment for bent-up  clips is        
desirable1 although where such a steel  
is used it is almost  necessary1 if the 
original strength of the material is to 
be retained  in the finished fitting1 to

 effect the various bends in a machine1 
in  conjunction with bending jigs4      
,careful heat-treatment after bending   
to shape is an important factor in      
removing the stresses set up by         
working1 and in rendering the structure 
of the material more uniform4           
,steel ,tube4    ,steel1 in the form of 
tubing of various sections1 enters      
largely into  aeroplane construction1   
and may be said to contribute largely to
 the  efficiency of the structure4 ,it  
is now being used for the different     
items of the undercarriage1 for struts  
in the fuselage1 interplane  struts1 and
 in many cases control surfaces1 such as
 the ailerons1  elevators1 and rudder1  
are being built of this material        
entirely4 ,in  the early days of        
aviation steel tubing attained some     
considerable  popularity1 many machines 
being built almost entirely of tubing2  
but  difficulties in its manipulation1  
and the fact that very often the        
methods of attachment reduced its       

strength considerably1 gradually  led to
 the general employment of wood4 ,the   
great advances lately made  in the      
production of a high-grade nickel-chrome
 steel1 with a high  ultimate tensile   
stress1 are responsible for its present 
increasing use4      ,aluminium4    ,the
 present use of aluminium is restricted 
to the cowling of the  engine1 and      
occasionally as a body covering4        
,although it is light in  weight1 its   
extremely low strength values render it 
of very little  use for other purposes4 
,it attained some measure of popularity 
in  the early days of aviation1         
particularly for the manufacture of     
different strut-sockets1 which were cast
 from aluminium2 but the  general       
bulkiness of the fittings1 in addition  
to the fact that it  was generally      
necessary to incorporate a steel lug to 
form the wire  anchorage1 caused it to  
gradually fall into disuse4 ,the        
tendency of  aluminium to flake and     
corrode1 which is intensified by the    

action  of salt water1 also limits its  
use for seaplane construction4 ,many    
attempts have been made through various 
alloys to impart greater  strength to   
the material1 and although progress has 
resulted1 the  characteristics of most  
of the products are unreliable4         
,duralumin4    ,of the different alloys1
 duralumin is probably the best1        
although one  believes that its         
qualities are principally the result of 
special  heat treatment4 ,its use is at 
present restricted to those parts not   
subjected to any great tensile strain4  
,it is considerably less than  half the 
weight of steel1 bulk for bulk1 and1    
properly used1 may effect  a            
considerable saving in weight4 ,the fact
 that it has not achieved the           
popularity it deserves may be ascribed  
to the difficulties experienced  in     
working it1 especially for such parts as
 body clips1 where several  bends are   
necessary1 and to the rather arbitrary  
methods in use4 ,if  properly annealed1 

no difficulty should occur in obtaining 
a reasonably  sharp bend4 ,the process  
recommended by the makers consists in   
heating  the metal in a muffled furnace 
to a temperature of approximately #cej  
,c41 and the necessary work done as soon
 as possible after cooling4 ,the        
importance of this is due to the fact   
that the process of annealing  imparts  
to the metal a tendency to become       
brittle with time4 ,the writer  has     
often contended that1 where duralumin is
 used1 it should be with  a real desire 
to reduce weight4 ,too often one sees a 
fitting of such  lavish dimensions as to
 entirely nullify the advantage of the  
lighter  metal4          ,,chapter      
,,iii4    ,,spars ,,and ,,struts4       
,having thus considered generally the   
chief materials of aircraft             
construction1 we will proceed to examine
 the various types of spars  and struts 
in present use4 ,the main spars of the  
wings are by far the  most important    
items of the complete structure1 and    

very great care is  always taken to     
ensure that only the best of materials  
and workmanship  are concerned with     
their manufacture4 ,looking back at the 
days one  usually associates with the   
aero shows at ,olympia1 multitudinous   
methods of building wing spars can be   
recalled4 ,some composed of  three-ply  
and ash2 others1 less common1 of channel
 steel2 and a few of  steel tubing1     
either plain or wood filled4 ,various   
reasons and causes  have combined to    
eliminate these methods of construction4
 ,for instance1  the spar of channel    
steel proved much too flexible1 although
 this  characteristic was no great      
disadvantage in those machines employing
  wing-warping for lateral control1 for 
with this arrangement a certain  amount 
of flexibility in the wing structure is 
essential4 ,while steel  tubing is      
excellent for many details it can hardly
 be said to be really  suitable for wing
 spars1 which are stressed essentially  
as beams4  ,now1 the strength of a beam 

varies as the square of the depth of the
  beam1 and it is obvious that in the   
case of a circular steel tube the       
material is evenly distributed about the
 neutral axis1 and therefore  its       
strength in both horizontal and vertical
 directions is equal2  although employed
 as a strut1 this feature becomes of    
real value4 ,one1  however1 still       
encounters its use on modern machines2  
indeed1 it must  not be supposed that   
the progress made in construction       
generally since  #aiad has tended       
greatly towards a reduction in the      
number of different  methods employed1  
and this will be realized from a        
consideration of  the accompanying spar 
sections which are in use to-day on one 
make of  machine or another4      ,spar 
,sections4    ,illustration3 ,,fig4     
#g4--,solid spar4    ,the ,i section    
form of wing spar1 shown by ,fig4 #g1 is
 in general  use1 being spindled from   
the solid4 ,it is comparatively easy to 
produce1 which in a measure explains its

 popularity1 and it also  disposes the  
material in probably the best manner for
 the stresses  involved4 ,the laminated 
spar1 ,fig4 #h1 is an improvement on the
  solid channelled spar2 it is stronger1
 will withstand distortion  to a greater
 degree without injury1 and the strength
 is also more  uniform than with the    
solid spar4 ,an additional point in its 
favour is that it is much easier to     
procure three pieces of small  section  
timber free from defects than one large 
piece1 which1 in  view of the increasing
 scarcity of perfect timber1 is an      
important  consideration4 ,in order to  
minimize the risk of the glue between   
,illustration3 ,,fig4 #h4--,laminated   
spar4    the laminations failing1 the   
usual practice is to copper rivet or    
bolt  the flange portion1 while both    
spars are left solid at the point of    
attachment of the interplane strut      
fittings and wire anchorages4 ,the  spar
 shown by ,fig4 #i is of the hollow box 
variety1 chiefly used for  machines of  

large wing surface1 where weight        
reduction is an important  factor4 ,the 
two halves of channel section are       
spindled from the solid  and glued      
together4 ,the joint is strengthened by 
the provision of small    ,illustration3
 ,,fig4 #i4--;,hollow box-spar4         
fillets or tongues of hard wood1 and in 
some instances the complete  spar is    
bound with glued fabric4 ,comparing the 
hollow spar with  the solid1 and        
neglecting the cost factor1 the writer  
contends that  the advantage is         
indisputably with the former4 ,the      
tendency of the  ,i-section spar to     
buckle laterally is of much lesser      
moment in a hollow  spar of the type    
shown by ,fig4 #i1 while for a given    
weight it shows  an increase in         
strength1 and for equal strength it is  
much lighter4 ,a  different version of  
the hollow spar system is that indicated
 by ,fig4  #aj1 consisting of two       
channelled sections1 tongued together at
 the  joint1 the sides being stiffened  

with three-ply4 ,the disposition of the 
joint in a vertical plane is a distinct 
improvement on the hollow spar          
previously considered1 mainly in that   
better resistance to a shearing  stress 
is afforded4    ,illustration3 ,,fig4   
#aj4--;,hollow spar with stiffened      
sides4    ,illustration3 ,,fig4         
#aa4--;,hollow spar with multi-ply      
sides4    ,the principle underlying the 
construction of the spar shown by ,fig4 
#aa1  is that in its manufacture the    
lengths of wood necessary are of small  
section4 ,the sides of this spar are    
built up with a centre of spruce  about 
in4 thick1 to each side of which is     
glued thin three-ply1  these being      
glued1 screwed1 and bradded to the      
flanges4 ,the wing spar  shown in       
section by ,fig4 #ab is unique in that  
it really constitutes  two spars placed 
closed together1 the connection being   
formed by the  top and bottom flanges of
 three-ply4 ,this spar was used in a    
machine  with planes of small chord1 but

 of very deep section1 and in which no  
interplane wiring occurred1 the wings   
functioning as cantilevers4 ,its  chief 
advantage is great rigidity for a low   
weight1 but such a spar  necessitates a 
deep wing section1 and is not in general
 use4    ,illustration3 ,,fig4          
#ab4--,twin box spar4      ,hollow ,spar
 ,construction4    ,the advantages of   
the hollow type of spar summarized are  
7#a7 greater  strength for a given      
weight2 7#b7 it can be produced from    
wood of small  section1 and is therefore
 a better manufacturing proposition4 ,on
  the other hand1 the strength of a     
hollow spar is greatly and almost       
entirely dependent on the glue used4    
,now1 however well the joint may be     
made1 the glue is susceptible to a damp 
atmosphere1 and if so affected  is of   
greatly reduced strength1 while possible
 depreciation in the glue  due to age   
renders the life of the spar a          
problematic quantity4 ,where  the       
various fittings occur it is also       

necessary to place blocks before  the   
spar is glued up1 which is rather an    
unmechanical job4 ,the practice  of     
forming vertical sides of a hollow spar 
from three-ply is not to be  commended1 
by reason of the doubtful character of  
the glue used in its  manufacture4      
,however1 in spite of these             
disabilities1 there is a future  for    
hollow spar construction in the         
manufacture of the big commercial       
machines of the future1 for with these  
the question of maximum strength  for   
minimum weight1 to permit the carrying  
of the greatest possible  useful load1  
will be a primary consideration4 ,this1 
of course1 assuming  that the era of the
 all-steel machine has not arrived4     
,strut ,sections4    ,in the            
construction of the interplane and      
undercarriage struts1 one  does not find
 a very decided preference for any one  
particular method1  although the        
interplane strut spindled from the solid
 to a streamline  section is common to  

many types of modern aircraft4 ,the     
strut shown  in section by ,fig4 #ac is 
in use for both interplane and          
undercarriage  struts4 ,this consists of
 ordinary round section steel tubing1 to
 which  is attached a tail piece or     
fairing of wood1 this being bound to    
,illustration3 ,,fig4 #ac4--,steel tube 
strut with fairing bound on4            
,illustration3 ,,figs4 #ad1             
#ae4--;,interplane struts spindled from 
the  solid4    the tube by linen tape or
 fabric1 doped and varnished4 ,this     
strut is of  practically equal strength 
in both lateral and longitudinal        
directions1  and from this point of view
 is superior to the solid spindled      
strut1  which is usually of great       
strength in the fore and aft direction1 
but  always possesses a tendency to     
buckle laterally4 ,fig4 #ad indicates a 
hollow plane strut1 in which the sides  
of spruce are spindled from the  solid1 
and glued to a central stiffening piece 
of ash2 while ,fig4 #ae is  arranged so 

that a stiffening web is formed in the  
spindling process4  ,owing to the rather
 extensive nature of the latter         
operation1 one does  not find many      
instances of its use4 ,where the hollow 
wood struts used  are not completely    
bound with tape or fabric1 they should  
at least be  bound at intervals with    
tape or fine twine1 as there is always  
the  possibility of the glued joint     
failing under the combined attentions of
  rain and heat4    ,a type of strut    
which is now being widely used is that  
of streamline  section steel tubing1    
drawn or rolled from the round section4 
,it is  employed for both the interplane
 and undercarriage struts1 but for  the 
latter has not given entirely           
satisfactory results1 owing to the      
tendency to buckle under extra heavy    
landing shocks4 ,this would be  more    
pronounced with a tube of fine section  
than with one possessing a  bluff       
contour2 but in any case1 a strut of    
parallel section1 whatever  the         

material1 is not well suited to         
withstand sudden shocks4 ,this point  is
 referred to later4 ,seeing that        
progress is being made with the         
production of a seamless streamline     
tapered strut this defect should  soon  
disappear4    ,illustration3 ,,fig4     
#af4--;,interplane support from body4   
,illustration3 ,,fig4 #ag4--,section of 
built-up strut4    ,in some machines the
 top plane is supported from the        
fuselage by struts  which are formed    
integrally with a horizontal compression
 member1 as  in ,fig4 #af2 the section  
of the vertical struts being shown by   
,fig4 #ag4  ,the ply-wood is cut to the 
shape of the complete component1 and    
forms  a tie for the spruce layers1     
which are jointed at the junction of the
  vertical and horizontal members4      
,strut ,materials4    ,referring again  
to the material generally employed for  
struts1 i4e4  silver spruce1 it is      
perhaps necessary to explain further the
 reasons  for its predominance over ash1

 as on a strength-for-weight ratio  the 
latter wood is slightly the better      
material4 ,the points already  detailed1
 indicate that an interplane strut is   
stressed essentially  in compression1   
and therefore the chief characteristic  
of ash1 great  tensile strength1 is of  
but secondary importance4 ,there is also
  the fact that1 for the same weight1   
spruce would be thicker1 and            
correspondingly more able to resist     
collapse4 ,however1 in machines of  the 
flying-boat class1 where the engine is  
invariably mounted between  the four    
central plane struts1 and consequently  
subjected to an amount  of vibration    
varying with the type of engine used1   
ash forms the  material4      ,tapering 
of ,interplane ,struts4    ,the correct 
shaping of struts longitudinally1       
particularly those for  interplane use1 
is apparently a rather controversial    
subject4 ,taking  the case of an        
untapered strut1 it is evident that the 
greatest  stress will be located at or  

near the centre1 so that if at this     
point the section is strong enough1     
clearly there must be an amount  of     
superfluous material at the ends4 ,by   
suitably reducing or tapering  the strut
 from the centre one can obtain the same
 degree of strength  for less weight4   
,conversely1 for the same weight a much 
stronger  strut is possible4 ,so it has 
always appeared to the writer4 ,it is1  
however1 admittedly possible that unless
 carefully done1 the operation  of      
tapering a strut may actually diminish  
the strength4 ,one method  of tapering1 
that of making the maximum cross-section
 at the centre1  and from this point    
diminishing in a straight line to the   
ends1 is  undoubtedly open to criticism1
 and a way more nearly approximating  to
 the correct method of shaping is to    
reduce the cross-section at  various    
points so that the finished contour is  
curvilinear1 as in ,fig4  #ah4 ,in this 
connection it is pertinent to emphasize 
the importance of  ensuring that all    

strut ends are cut to the correct       
bevels1 and this  is particularly       
applicable to those struts which seat   
directly in a  socket4 ,the slightest   
irregularity will cause considerable    
distortion  when assembled under the    
tension of the bracing wires1 and       
frequently  the writer has seen an      
ostensibly perfect strut assume the most
  hopeless lines directly the operation 
of truing up is commenced4              
,illustration3 ,,fig4 #ah4--,tapering of
 interplane struts4      ,design of     
,strut ,sections4    ,although1 strictly
 speaking1 the design of strut shapes is
 outside  the scope of this book1 a few 
remarks anent the development of        
streamline may emphasize the advances   
made1 and also the need  for careful    
construction4 ,the resistance of a body 
is generally  considered to increase as 
the square of the speed1 i4e4 double    
the speed and head resistance is        
doubled1 and while this is true  for a  
moderate range of speeds1 experiment has

 proved that for high  speeds1 exceeding
 say #ajj miles per hour1 resistance    
increases at  rather less than as the   
square of the speed4 ,however1 it is    
certain  that the correct shaping or    
otherwise of the struts and other       
exposed members1 affects generally the  
performance in flight of the  aeroplane4
 ,the accepted feature of all streamline
 forms is an easy  curve1 having a      
fairly bluff entrance and gradually     
tapering to a  fine edge4 ,the ratio of 
length to diameter1 called the fineness 
ratio1 varies in modern machines1 being 
in some instances #c to #a and  in      
others #e to #a1 a good average being #d
 to #a4 ,considering only the  point of 
head resistance1 it would be better to  
choose a section of  high fineness      
ratio1 but constructionally such a strut
 would buckle  sideways under a moderate
 load1 and therefore the cross section  
must be sufficient to resist this4 ,the 
strut section used on the  earliest     
aeroplanes1 such as the ,wright biplane1

 shown by ,fig4 #ai1 is                 
,illustration3 ,,fig4 #ai4    ,,fig4    
#bj4    ,,fig4 #ba4    ,,fig4 #bb4      
,,figs4 #ai-bb4--,strut sections4       
nothing more than a rectangle with the  
corners rounded off4 ,fig4 #bj  shows a 
development of ,fig4 #ai consisting of a
 semi-circular head with  a cone-shaped 
tail1 which by gradual evolution has    
resulted in the  section ,fig4 #ba4     
,some experiments carried out a         
considerable time ago  by ,lieut4-,col4 
,alec ,ogilvy1 revealed the rather      
interesting point  that a strut shaped  
as in ,fig4 #bb gave the same results as
 a similar  strut taken to a fine edge4 
,the reasons for the non-suitability of 
a  sharp-pointed section are apparent   
from a consideration of ,fig4 #bc1      
showing the action of a side wind with  
the resultant dead air region4          
,illustration3 ,,fig4 #bc4--,showing    
inefficiency of pointed section in a    
side wind4      ,fuselage ,struts4      
,illustration3 ,,fig4                   

#bd4--;,channel-section fuselage strut4 
,illustration3 ,,fig4 #be4--,t section  
fuselage strut4    ,in the general      
features of those struts associated with
 the  construction of the fuselage and  
nacelle1 there is very little  diversity
 of practice1 the majority of           
constructors favouring a square  spruce 
strut1 ,fig4 #bd1 channelled out for    
lightness4 ,a defect with  this type of 
strut is the tendency1 engendered by    
irregularities in  the fittings and     
wiring1 to buckle laterally1 although   
this can be  obviated by the provision  
of a strut of larger section at the     
centre  and diminishing in width to the 
ends4 ,a strut not nearly so popular    
but nevertheless in use is that         
indicated by ,fig4 #be1 consisting of   
spruce spindled to a ,t section the web 
being of considerable width at  the     
centre4 ,it would seem that the piece of
 wood necessary to obtain  such a strut 
is out of proportion to its actual      
finished dimensions1  and from the      

standpoint of economy in both labour and
 material is not  justified4 ,the       
circular turned and tapered strut       
noticeable on a number  of machines     
disposes the material in probably the   
best manner for the  conditions         
applicable to this component1 although  
it necessitates the  provision of       
tubular ferrules in the fuselage clip4  
,on one modern  machine the fuselage    
struts are circular1 but of hollow      
section1 built  up of two pieces glued  
together4 ,an obsolescent method is that
 in which  the strut is shaped to       
something approaching a streamline      
section1 as  the fact that all aeroplane
 bodies are now fabric covered renders  
it  unnecessary4          ,,chapter     
,,iv4    ,,plane ,,construction4        
,of the various components which        
comprise the complete machine1 the      
wings1 aerofoils1 or planes1 as these   
items are variously designated1  may be 
said to contribute the greater part of  
the ultimate success of  the complete   

machine4 ,the aerodynamical properties  
of a wing are now  fairly well          
determined1 and have been the subject of
 a great number  of experiments1        
resulting in the clearing away of many  
hazy ideas and  notions1 so that the    
actual design of the wing section for   
machines of  given purpose is almost    
standardized4 ,from this it might be    
deduced  that the methods of            
construction were equally well          
determined1 and  although absolute      
uniformity of practice does not exist1  
the wing  construction of most machines 
is similar1 as far as the main assembly 
is concerned4      ,effects of          
,standardization4    ,incidentally1 one 
may point out the detrimental effects of
 undue  standardization as applied to an
 industry in its preliminary stages4    
,these effects are well exemplified by  
certain machines1 in which              
standardization has been studied to an  
almost meticulous extent1 with  the     
logical result that their performance is

 considerably inferior to  that of other
 machines of contemporary design1 but in
 which desirable  improvements are      
incorporated as they occur4 ,although at
 present one  cannot give actual        
figures1 the average performance of     
modern ,british  aircraft in range of   
speeds1 rate and extent of climb is     
superior  to the products of any other  
country1 and one certainly cannot cite  
the construction of the average ,british
 machine as an example of               
standardization4 ,seeing that1 as a     
typical instance1 wing sections  are    
frequently altered in minor detail1 the 
impracticability of  standardization is 
apparent1 for this would entail1 to a   
firm wishing  to keep pace with         
developments1 a considerable loss1      
through scrapping  of jigs1 etc41       
consequent upon the new design4 ,when   
the principles of  aeroplane design are 
as well defined as those pertaining to  
internal  combustion engines1 one may   
expect the various manufacturers to     

produce  one type of machine per year1  
and the various improvements adduced    
from the year's experience would be     
incorporated in the type of the         
succeeding year4    ,illustration3      
,,fig4 #bf4--,plan view of wing         
assembly4    ,however1 leaving the      
realms of vaticination for the more     
prosaic  subject of wing construction1  
it will be realized that the process  of
 producing the full-sized wing1         
accurately conforming to the            
measurements1 etc41 deduced from        
experiment1 and so constructed that  the
 chief characteristic of the section    
will permanently remain1 is of          
importance4 ,as one or two of the spar  
sections in use were dealt with  in the 
first chapter1 it will be unnecessary   
again to consider them in  detail4      
,fig4 #bf shows diagrammatically the    
plan view of a wing assembly typical  of
 modern practice1 so far as the         
disposition of the various components   
is concerned4      ,shaping of ,main    

,spars4    ,illustration3 ,,fig4        
#bg4--,shaping of main spars4    ,taking
 in greater detail the different parts1 
it is apparent that  the spars form the 
nucleus of the general arrangement4     
,there are two  methods of shaping the  
spar longitudinally1 and1 as shown by   
,fig4 #bg1  the one consists of leaving 
it parallel for the greater part of its 
length1 while the end forming the tip of
 the wing is gradually tapered  to a    
comparatively fine edge4 ,this may be   
said to constitute prevailing  practice4
 ,the other method which is illustrative
 of monoplane practice  is not used to  
anything like the same extent1 and      
differs in that  it is constantly       
tapering from root to tip4 ,the         
advantage of this  spar construction is 
the improved distribution of the        
material for  the stresses involved1 and
 also that a wing built with this spar  
may possibly possess a greater degree of
 lateral stability owing to  the weight 
of the complete wing being located      

nearer the centre of  gravity4 ,against 
this one must balance the fact that each
 rib must  necessarily be different in  
contour1 entailing a greater number of  
jigs1 an increase in the time taken in  
building1 with a consequent  increase in
 cost4 ,in addition1 all strut fittings 
would differ in size1  so that1 taking  
all things into consideration1 this     
construction is  hardly justified4 ,it  
will be noted that at the point of      
attachment of  the interplane strut     
fittings1 or1 in the case of the        
monoplane wing1  the anchorage for the  
wires1 the spar is left solid4 ,it is   
possible to  channel the spar right     
through1 from root to tip1 and to glue  
blocks  where fittings occur2 and       
although there is a possible saving of  
labour thereby1 it hardly conforms to   
the standards of modern workshop        
practice4      ,defects of ,glue in     
,wing ,spars4    ,although gluing is a  
most necessary operation in modern wing 
construction1 it is not what one would  

call an engineering proposition4  ,it   
has a tendency to deteriorate with time1
 especially if exposed to  a humid      
atmosphere4 ,a great deal depends on the
 method of making the  joint1 and an    
operation such as gluing a laminated    
wing spar is usually  carried out in a  
special room of certain temperature4    
,such spars are  generally additionally 
fixed by rivets1 bolts1 or screws       
through  the flanges4 ,the material     
should always be dry1 and as straight   
and  close-grained as can be procured4  
,the straightness and closeness of      
grain affect the strength to a          
remarkable degree2 and here it may be   
remarked that the use of the best       
material is a most important factor  for
 ensuring sound construction1 and one   
that in the end pays4 ,if a  spar should
 happen to be cut from a wet log1 it may
 in the interval  between its finishing 
as a part and subsequent assembly in the
 wing  cast or warp1 which may cause    
trouble in assembling1 and is more      

likely to result in eventually being    
sawn up as scrap4 ,the resultant        
section of any wing is really dependent 
upon the spar being of correct  section1
 and should the spar be out of 8truth10 
the section will vary  at different     
points4 ,this may not be eradicated even
 in the erection  of the machine1 so    
that finally the actual flying          
properties of the  machine will be      
affected--another illustration of the   
importance of  thorough construction in 
ensuring a good and lasting performance4
 ,to  secure uniformity and             
interchangeability the wing spars are   
set out for  the wing positions1 and the
 necessary holes for the fittings       
drilled to  jig1 before being handed    
over to the wing erectors4              
,arrangement of ,planes4    ,the usual  
arrangement on machines of the scout    
type is for the lower  plane to butt    
against the lower members of the        
fuselage1 and the top  planes being the 
same span1 the width of the body is made

 up by a  centre plane4 ,another method 
is to make the top plane in two portions
  only1 thus obviating the centre plane2
 and occasionally the spars of  the top 
plane run through1 from wing-tip to     
wing-tip1 although this  is only        
possible in machines of small span4     
,apart from the fact that  such a wing  
requires extra room1 it is difficult to 
procure timber  of length exceeding #bj 
ft4 sufficiently straight in the grain2 
and a  minor detail would be the        
difficulty of repair1 as a damaged      
wing-tip  would practically entail a new
 spar1 as splicing1 although permissible
  in some parts of the machine1 should  
not be tolerated as a means of          
repairing wing spars4    ,the difficulty
 of obtaining timber will necessitate   
the wings of large  machines being made 
in sections2 and there are several      
instances where  this form of           
construction has been adopted1 in one   
case the sections  being only five feet 
in length4 ,this construction seems     

eminently  suited to the post-war       
sporting machine1 as chance damage would
 be  confined to a smaller area1        
transport simplified1 and1 providing the
  joints are well made1 no appreciable  
loss in efficiency should ensue4        
,types of ,wing ,ribs in ,use4    ,from 
a survey of the plane diagram1 ,fig4    
#bf1 it will be noticed that  the chief 
components1 in addition to the main     
spars1 are the ribs1  box-ribs1         
stringers1 and leading and trailing     
edges4    ,illustration3 ,,fig4         
#bh4--;,construction of ribs4    ,the   
ribs1 which is the term applied to the  
very light framework built  over the    
spars to maintain the correct curvature1
 are variously  constructed2 one of the 
most popular methods in vogue is that   
shown  by ,fig4 #bh4 ,the central       
portion1 or web1 which includes the nose
 and  trailing edge formers1 may be cut 
from either spruce1 whitewood1 cotton   
wood1 which can be bent to a surprising 
degree without fracture1 and  three-ply4

 ,three-ply1 while excellent for some   
items1 is hardly suited  for this       
purpose1 as the laminations have a      
tendency to come apart1  especially in  
the lower grades1 which is aggravated by
 the screws or  brads necessary for the 
attachment of the flange4 ,a rib1       
fretted out  as in ,fig4 #bh1 with the  
web of cotton wood and a spruce flange1 
can be  made extremely light4 ,a rib for
 a chord of from #d ft4 #f in4 to #e ft4
  would weigh about #e oz4 ,as it is    
very necessary that every rib should    
correspond1 these parts should be made  
to a metal jig1 which is about  the only
 way to ensure exactitude4 ,this should 
be made from mild sheet  steel1 about   
#af ,b4,w4,g41 and need only be shaped  
to the outer curve1  as the lightening  
holes are of but secondary importance1  
these being  usually marked out in the  
saw mill1 and cut to the line with a    
fine  jig saw4 ,for production in       
quantity a box jig1 between which a     
dozen  ribs might be clamped and shaped1

 is preferable4 ,templates of wood  are 
of doubtful accuracy1 for not only do   
corners wear1 but gradual  shrinkage    
soon renders them useless4 ,the         
incorrect shaping of the  most          
insignificant piece of wood may have    
far-reaching effects when  assembled1   
and any extra trouble taken in the      
preparation of parts is  more than      
repaid by the subsequent ease and       
precision of erection4    ,while the    
method of rib building previously       
described constitutes  general practice1
 there are1 of course1 other            
arrangements in vogue4  ,fig4 #bi       
illustrates a system in which the front 
spar forms the leading  edge1 a         
procedure which is somewhat rare now1   
owing to the features  of modern wing   
sections1 but at one time quite common4 
,in this case  the web is of three-ply  
lightened with a series of graduated    
holes1  according to the width of the   
web1 and the flanges of spruce4    ,the 
rib assembly1 ,fig4 #cj1 is extremely   

simple and light1 as in this  case the  
web proper is superseded by thin strips 
of three-ply1 glued  and bradded each   
side of the spruce flange4 ,the amount  
of woodwork  between the spars is       
reduced to a minimum1 although one can  
hardly  imagine such a system answering 
for a chord over five feet4 ,even then  
the wing curvature would require to be  
fairly simple1 as a pronounced  curve   
would flatten out4 ,as a point of fact1 
this assembly is rarely  used for chords
 exceeding #d ft4 #f in4 ,in another    
arrangement as shown  in ,fig4 #ca1 the 
connection between the top and bottom   
flanges is  formed by blocks1 a method  
which is certainly economical of        
material4    ,illustration3 ,,fig4 #bi4 
,illustration3 ,,fig4 #cj4              
,illustration3 ,,fig4 #ca4              
,illustration3 ,a ,,fig4 #cb4    ,,figs4
 #bi-cb4--;,construction of ribs4    ,an
 interesting form of rib design is that 
shown by ,fig4 #cb1 and in this         
instance the fretting is specially      

designed to prevent any flattening  out 
of the camber4 ,the rib section is shown
 at ,a1 ,fig4 #cb1 and it will  be      
noticed that the flange of chamfered    
section is grooved to take the          
three-ply web4 ,the vertical parts of   
the web are stiffened by small          
semi-circular fillets4      ,ribs under 
,compression4    ,for those ribs        
contiguous to the interstrut joints1 a  
different  construction is necessary to 
withstand the tension of the            
cross-bracing of the planes and1 to a   
lesser degree1 the internal  plane      
wiring1 so that at this point the rib   
performs two functions1  that of        
maintaining the wing curve1 and also    
taking the strains due  to compression4 
,where such provision is not made1 the  
tension of the  wiring will result in   
either or possibly both of the          
following3 7#a7 the  rib will buckle    
laterally2 7#b7 the camber will increase
 to an extent  varying with the pressure
 on the wires1 both results being       

extremely  detrimental to efficiency4   
,in this respect the old box-kites of   
varying  origin used to offer some      
interesting studies in variable camber1 
and  when it is remembered that the wing
 ribs were commonly composed of a       
single ash lath1 steamed to shape1 and  
the fabric attached on the top  side    
only1 the wonder is that extended flying
 was possible at all4  ,for all that1   
some comparatively classic cross-country
 flights were  accomplished4 ,one       
popular system is to incorporate a      
box-rib at these  points1 sometimes made
 by placing two ordinary ribs close     
together and  connecting them with      
three-ply or thin spruce1 so that1      
although the  overall width of the      
finished box-rib would be approximately 
#b in41 it  is exceptionally rigid and  
withal light4    ,illustration3 ,,fig4  
#cc4--;,compression rib4    ,another    
solution is to use a solid web1 lightly 
channelled out1 as in  ,fig4 #cc4    ,in
 some wing structures the ribs are      

uniform throughout1 a strut of  either  
steel tube or wood being inserted and to
 which the internal  wiring is attached4
 ,this latter method is possibly more   
desirable1  that is1 if the joint       
between the compression strut and spar  
can be  combined with the interstrut    
fitting4 ,this may necessitate a little 
extra work in the latter1 but this is   
preferable to the use of a  separate    
fitting1 involving additional piercing  
of the spar4      ,importance of ,even  
,contour4    ,whilst on the subject of  
rib building1 one cannot over emphasize 
the  desirability of even contour1 and  
the template1 illustrated by ,fig4  #cd1
 serves as an admirable check4 ,it is   
cut from very dry material to  the      
outside curve of the section1 and if    
this is tried on as each rib  is fixed1 
one may be sure of comparative          
uniformity4 ,the root rib is  generally 
of stouter construction1 and usually    
follows the same lines  as the          
compression ribs4 ,at this point the    

pull of the fabric has to be  contended 
with1 which is not infrequently a       
considerable strain4 ,the  same         
conditions prevail at the wing tip1     
which is one reason against  excessive  
reduction of material at this point4    
,instances occur where  the tension of  
the fabric after doping has considerably
 deformed the  tip curve1 which is at   
least unsightly1 and may entail         
reconstruction4    ,illustration3       
,,shaped ,,to ,,under ,,surface         
,,fig4 #cd4--,template for testing rib  
contours4      ,wing ,tip ,details4     
,the actual shape of the wing tip varies
 with the make of machine1 and  forms   
one of the distinctive features of the  
complete assembly4 ,there  is a general 
tendency to rake the ends1 making the   
back spar longer  than the front1 on the
 score that increased efficiency due to 
reduction  of end losses is attained4   
,while this is somewhat problematic1    
seeing  that several notable machines   
have square tips1 and some actually     

constructed with the longest edge       
leading1 it undoubtedly imparts a       
pleasing and distinctive appearance4    
,the actual construction is largely a   
matter for individual preference1  as   
there are several ways of forming it4   
,for instance1 a single piece  of ash   
may be bent to shape1 or it may be cut  
out in sections from  spruce boards and 
glued together with a long splice1 while
 in another  instance oval steel tube is
 the material4 ,this small section steel
  tubing seems admirably suited for such
 items as wing tips1 trailing  edges1   
and the various components of the       
empennage1 such as the fixed            
stabilizer1 elevators1 fin1 and rudder4 
,another method of construction used for
 the wing tips of some machines         
consists of a number of strips1 about   
six for a wing tip #a in4 wide by   in4 
thick1 the joints between which are     
disposed vertically1 forming  a         
laminated wing tip4 ,in manufacture1    
each piece is bent round bending  jigs  

or blocks of the required shape1 the    
edges of the strips having  previously  
been glued4 ,it is apparent that the    
smaller the section of  strip used1 the 
easier it can be bent1 and with this    
arrangement quite  sharp bends can be   
successfully formed in spruce4 ,the     
alternative  method of steaming a solid 
piece is often wasteful1 apart from the 
fact  that it enforces the use of ash4  
,,chapter ,v4    ,,details ,,of ,,plane 
,,construction4      ,the tendency to   
lose lift1 pronounced in some machines1 
hardly  noticeable in others1 may be    
directly traced and attributed to the   
manner in which the wings are built1    
which is largely dependent upon  the    
design4 ,in the preliminary stages of   
design it is usual to take  as a basis  
the figures for lift and drift of a     
known tested section1  that is if       
facilities are not available for testing
 an exact scale  model of the section it
 is intended to use4 ,anyway1 the whole 
design  is dependent upon these figures1

 in respect of both the maximum and     
minimum speeds1 and also the rate of    
climb1 and the extent to which  the     
actual performance of the machine       
complies with these calculations  is    
determined solely by the exactitude and 
precision with which the  full-size wing
 conforms to the scale model4 ,by this  
means only is it  possible to design    
with any degree of accuracy4      ,the  
,sagging of ,fabric4    ,the sagging of 
the fabric between the ribs is one of   
the principal  reasons for the failure  
of the finished machine to satisfy      
expectation  and also of the tendency to
 lose lift4 ,one or two causes          
contribute to  this result4 ,one is the 
spacing of the ribs1 which in some cases
 is  not nearly close enough4 ,a rough  
average spacing is from #aj ins4 to  #a 
ft41 but in modern high-speed machines1 
loaded to anything from #e  lbs4 to #h  
lbs4 per square foot1 the spacing should
 be much closer4 ,in  addition1 the ribs
 near the wing root should be closer    

than those at  the tip1 for at this     
point the stresses are greater1 a       
certain amount  of vibration from the   
engine having to be contended with1 in  
addition  to the effects of the         
slip-stream of the air-screw4           
,particularly  noticeable is the        
tendency for the fabric to sag down on  
the top  surface of the leading edge1 a 
feature which imparts to the machine1   
especially when viewed from the front1 a
 not unpleasing corrugated  appearance4 
,at this part of the section the curve  
is somewhat sharp1  and naturally the   
fabric tends to conform to the          
definition of the  shortest distance    
between two points1 a straight line4    
,this1 of course1  is aggravated in     
flight1 when the planes are under load1 
and by far the  greatest amount of      
pressure is located at the front        
portion1 or leading  edge1 of the wing4 
,false ,ribs4    ,illustration3 ,,false 
,,ribs    ,,fig4 #ce4--;,arrangement of 
ribs at leading edge4    ,in some wing  

constructions the forces are minimized  
by the provision  of subsidiary or false
 nose-ribs1 ,fig4 #ce1 which extend     
usually from  the leading edge as far   
back as the front spar and occasionally 
to the  longitudinal stringer4 ,while   
this prevents1 to a certain extent1 the 
sagging in of the fabric1 it does not   
entirely eradicate it4 ,the only        
successful way in which the             
characteristics of the wing contour may 
be  preserved is by covering the leading
 edge with thin veneer1 spruce1  or1    
still better1 three-ply1 as ,fig4 #cf4  
,despite the great advantages  attending
 this constructional feature1 its use   
cannot be said to be  really extended4  
,illustration3 ,,fig4 #cf4--,three-ply  
covering for leading edge4              
,pressure at ,leading ,edge4    ,the    
pressure at the leading edge produced by
 the enormous speed at  which the modern
 machines fly 7and the maximum diving   
speed of which1  owing to the reduction 
of resistance1 is correspondingly       

increased7  must be abnormal1 and calls 
for different methods of construction   
from  those which at present obtain4    
,there is at least one case on record   
where the fabric has burst at this point
 with fatal results4 ,it is  interesting
 to note that in the report of the      
,n4,p4,l4 for the year  #aiaf-ag mention
 is made of the deformation of the wing 
form1 due to  the sagging of the fabric1
 which has been reproduced in model     
form1  so that the allowances to be made
 and the resultant effects have been    
determined4      ,effect of ,lateral    
,control4    ,the system adopted for the
 lateral control is a decisive factor in
  deciding the general lines of         
construction4 ,the arrangement of plane 
warping1 whereby the wing was twisted or
 warped from root to tip1 or  the outer 
section only1 has given place to the    
almost universal use  of aileron        
control4 ,with the old warping system   
the ribs1 spars1 and  the whole wing    
collectively was subjected to a         

torsional strain1 which  could only have
 had a deleterious effect upon it4 ,this
 fact was almost  entirely responsible  
for the practice of using steel tube for
 wing  spars1 for by its use it was a   
fairly easy matter to arrange the ribs  
to slide or hinge upon the tube1 which1 
at least1 relieved some of the          
torsional stress4      ,leading and     
,trailing ,edges4    ,illustration3     
,,fig4 #cg4--,leading edges4    ,the    
average practice concerning the         
formation of the leading and  trailing  
edges is shown by ,figs4 #cg and #ch4   
,where the section in use  requires a   
bluff entry the spindled-out nose-piece 
is applicable1 while  for a sharp entry 
a fillet let into the nose-formers      
suffices4 ,as  previously mentioned1    
steel tubing makes a satisfactory       
trailing edge1  although somewhat       
heavier than the spruce strip1 while an 
extremely  fine leading edge can be     
formed by steel wire4 ,the edge1 under  
pressure  of the fabric1 assumes a      

variegated shape1 a distinctive feature 
of  some types1 but1 nevertheless1 a    
wire trailing edge is somewhat flabby   
and undulating1 and as a method is      
obsolescent4 ,longitudinal stringers    
are employed to preserve the wing       
contour and also for a stiffening       
medium for the ribs in a lateral        
direction4 ,about the only variation  of
 the small spruce strip for the purpose 
is linen tape1 crossed  alternately4    
,illustration3 ,,fig4 #ch4--,trailing   
edges4      ,efficiency of the ,raked   
,wing ,tip4    ,in the previous chapter 
mention was made of the probable gain in
  efficiency resulting from the raked   
wing tip1 and that this has some        
foundation in fact will be apparent from
 a consideration of ,fig4  #ci1 which   
illustrates the flow of air across a    
plane1 as generally  accepted4 ,where   
the plane surface is continuous from    
wing tip to wing  tip1 the provision of 
the shaped tip would appear to          
compensate for any  slight loss1 but    

there are instances where the extent of 
the pilot's  range of view is of the    
utmost importance1 and this may         
necessitate  the cutting away of a      
portion of the centre section 7which    
sometimes  affords the only means of    
ingress and egress71 or the root of the 
lower  plane1 as in ,fig4 #dj4          
,illustration3 ,,fig4 #ci4--;,diagram   
showing flow of air across plane4       
,illustration3 ,,centre ,,section ,,cut 
,,away    ,,spar ,,roots ,,cut ,,away   
,,fig4 #dj4      ,wing ,baffles4    ,an 
attempt to prevent air leakage caused by
 this is occasionally  observed in the  
employment of vertical vanes1 or wing   
baffles4 ,in the  case of a machine with
 the lower plane abutting against the   
side of  the fuselage1 these would not  
be necessary1 the fuselage acting in    
the same manner4 ,the baffles are       
usually of three-ply or spruce1 and     
shaped to project above the top and     
bottom surfaces1 this projection  rarely
 exceeding six inches4 ,a typical       

arrangement is illustrated by  ,fig4    
#da1 which also shows the exposed spars 
streamlined with a fairing  of          
three-ply4 ,it is typical of the varied 
opinions which still exist1  that on    
some machines the wing roots are merely 
washed out somewhat  abruptly4 ,if this 
air leakage is of any moment1 it is     
apparent that  it must detrimentally    
affect the lift-drift ratio4 ,as a proof
 of the  existence of pressure at the   
openings in the wing1 the writer        
remembers  the case of a well-known     
seaplane1 where the wing baffles on the 
centre  section were made of somewhat   
thin three-ply4 ,in flight it was       
noticed  by the pilot that these were   
being forced away from the wing1 and    
subsequently these were replaced by     
baffles of stouter construction4        
,illustration3 ,,fig4 #da4--,wing       
baffle4      ,metal ,wing ,construction4
    ,of two machines1 equal in air      
performance1 the one which can be most  
easily produced has an obvious and1     

especially at the present time1 a  very 
important superiority4 ,rapidity of     
production is a most cogent  argument in
 favour of metal construction1 for once 
the necessary  machines are set up1 and 
the jigs and dies made1 and given a     
constant  supply of material1 output is 
only limited by the speed of the        
machine4  ,in addition1 there are the   
very exacting demands of                
interchangeability4  ,now1 it is        
infinitely more easy to obtain          
exactitude in metal than in  wood1 and1 
moreover1 assuming that it is possible  
to produce woodwork  to the nearest #ja 
of an inch1 what preventive is there    
against  shrinkage1 which occurs even   
when using the dryest of timber4 ,by the
  more extensive use of metal there     
should be a considerably reduced        
proportion of scrapped parts1 and       
erection would be accelerated4 ,it is   
significant that the planes of some of  
the most recent ,german machines  are   
constructed largely of steel tubing1    

which is at present the most            
practicable form in which steel can be  
used4 ,of course1 steel tube spars  are 
quite an old detail1 although the more  
general ,english practice is  to core   
them with spruce or ash1 as in ,fig4    
#db4 ,one remembers a    ,illustration3 
,,fig4 #db4--,steel tube spar with wood 
filling4    monoplane1 built some time  
before the war1 in which the spars and  
ribs  were of steel and the covering of 
thin aluminium sheet4 ,in flight  this  
machine was particularly fast1 which may
 be accounted for by the  reduction of  
skin friction1 which a smooth surface   
such as aluminium  would afford4 ,in    
addition1 the tendency of a fabric      
covering to sag was  also obviated4     
,another example of metal construction  
is afforded by  the ,clement-,bayard    
monoplane1 exhibited at ,olympia in     
#aiad4 ,the plane  construction of this 
machine1 as shown by ,fig4 #dc1         
consisted of channel  steel spars1 steel
 leading and trailing edges1 and thin   

steel strips  replacing the usual wooden
 stringers4 ,however1 steel construction
 in  modern ,english machines is        
restricted to the various organs of the 
empennage1 and occasionally one finds   
ailerons so built4 ,there seems  no     
valid reason for the continued use of   
wood as the material for  the           
construction of such items as the fin1  
rudder1 and elevators1  as a            
considerable saving of labour and time  
can be effected by using  the various   
forms of steel tubing2 moreover1 the    
tendency which most  controlling organs 
built of wood have to warp and twist    
with variations  in temperature is      
prevented by the steel frame4 ,one      
frequently sees  such items as the      
ailerons and elevators distorted1 which 
must result  in excessive drift1 if not 
erratic flying4 ,at the present time it 
is  difficult to obtain aluminium alloy 
in any large quantity1 and this1  in    
conjunction with the present high       
prices1 precludes its extensive  use4   

,when this material is procurable in    
quantity1 and when design is  reasonably
 standardized1 rolled or lattice spars  
and stamped ribs may  come into vogue4  
,illustration3 ,,steel ,,spars    ,,fig4
 #dc4--,rib construction with metal     
spars4      ,fabric ,attachment4        
,fabric and its attachment is a matter  
requiring considerable attention1  with 
the great pressure to which modern wings
 are subjected4 ,in the old  days any   
fabric which was light with a moderate  
degree of strength was  utilized4       
,nowadays1 it is required to stand a    
certain strain in warp  and weft1 and   
rightly so1 since the bursting of fabric
 in flight can  only have one result4   
,it is interesting to note that the     
fabric used  on the ,deperdussin        
hydro-monoplane was specially woven with
 threads  running at right angles1      
forming innumerable squares4 ,the       
purpose of  this was that1 should a     
bullet or any object pierce any one of  
the  squares1 damage would be confined  

to that square1 and thereby prevented   
from developing2 but the writer cannot  
recall any instance of its use  to-day4 
,in covering1 the fabric should be      
tightly and evenly stretched from end   
to end of the wing1 and only            
comparatively lightly pulled from       
leading  to trailing edge4 ,if too much 
strain is applied to the fabric         
crosswise  it will result in undulations
 between each rib4 ,the tendency of     
fabric  to sag between the ribs is      
accentuated by this1 and1 of course1    
matters  are not improved upon the      
application of the dope4 ,it should be  
remembered that the efficiency of any   
machine is greatly dependent upon  the  
tautness of the fabric4 ,it should not  
be stretched too tightly1 as  the       
application of the specified coats of   
dope may result in the fibres  or       
threads of the material being           
overstrained4    ,illustration3 ,,cane  
,,strips ,,screwed ,,to ,,ribs    ,,fig4
 #dd4--;,attachment of fabric to ribs by

 cane strips4    ,with regard to the    
actual attachment of the covering to the
 wing  framework modern practice is     
restricted to two methods4 ,the older   
method is illustrated by ,fig4 #dd1 and 
consists of strips of spruce1  or more  
usually cane1 tacked or screwed to the  
ribs4 ,it is usual1 and  certainly      
preferable1 to affix this beading to    
every rib of those  sections of the     
planes adjacent to the fuselage1 as the 
fabric on  these portions is subjected  
to the slip stream of the propeller1    
which meets it in a succession of small 
blows4 ,the fabric in the  outer        
sections need only be affixed to        
alternate ribs4 ,the alternate  method  
is shown by ,fig4 #de4 ,in this case the
 fabric is sewn to the    ,illustration3
 ,,fig4 #de4--;,fabric sewn to ribs4    
ribs with twine or cord1 the stitches   
occurring about every three  inches4 ,it
 will be noted that every loop or stitch
 is locked with  a species of half-hitch
 knot4 ,this stitching is then covered  

with  bands of fabric1 the edges being  
frayed to ensure perfect adhesion  and  
doped to the main cover4 ,it is largely 
a matter of opinion  which system       
ensures the most even wing contour1     
although it would  seem that the drift  
or resistance is slightly lessened by   
the  sewing method4 ,an obsolete method 
is that in which the fabric was  tacked 
to the ribs with brass pins and taped   
with linen tape4 ,all  sewn joints in   
wing covers should be1 and generally    
are1 of the  double lapped variety      
7,fig4 #df71 and arranged to run        
diagonally  across the wing4 ,a minor   
and somewhat insignificant detail of    
wing    ,illustration3 ,,fig4           
#df4--;,double-lapped joint in fabric4  
covering is the provision of small      
eyelet holes in the under surface  of   
the trailing edge1 allowing water       
accumulated through condensation  to    
drain away1 and although not general    
practice1 would appear to be  necessary4
 ,a refinement which may be necessary on

 the post-war sporting  machine is the  
attachment of small blocks1 or 8domes of
 silence10 to  the leading edge1 as a   
protection for the fabric against wear4 
,when  planes are dissembled more often 
than not they are stacked leading edge  
downwards on a concrete floor1 and any  
movement or friction is likely  to      
result in the rubbing away of the       
fabric1 which1 if unnoticed1 may  result
 in the bursting of the covering4 ,such 
fitments would hardly  constitute an    
innovation1 as the writer has distinct  
recollections of  seeing such fittings  
on the ,d4,f4,w4 biplane at ,brooklands 
just prior to  the outbreak of war4     
,these consisted of brass balls1 free to
 rotate  in a socket1 screwed to the    
leading edge4 ,a narrow strip of        
aluminium  screwed along the entering   
edge would be quite sufficient1 and     
would  not add appreciably to the       
weight4          ,,chapter ,,vi4        
,,interplane ,,strut ,,connections4     
,it may be taken as fairly conclusive   

that for war purposes the biplane  has  
proved its superiority1 and it appears  
also that for the commercial            
requirements of the future it is suited 
still better1 and therefore1 in  view of
 the huge possibilities thus opened up1 
is likely to maintain  this             
predominance4    ,as the arrangement of 
planes in a biplane forms the extremely 
simple  yet enormously efficient        
box-girder1 it is generally considered  
superior in strength to weight          
requirements1 although for monoplanes   
of small span it is doubtful if this is 
so1 which affords some  indication of   
the possibilities of the small monoplane
 as the sporting  machine of the days to
 come4 ,seeing that the principal       
difference  between the biplane and     
monoplane consists essentially in the   
type  of truss employed1 the arrangement
 and attachment of the various  members 
peculiar to the biplane truss becomes of
 interest1 certainly  of importance4 ,it
 is intended to deal with the various   

trusses in a  later chapter1 confining  
the present remarks to the interplane   
strut  fittings in use1 and commencing  
by detailing the chief requirements  and
 desirable features4 ,the most desirable
 requirement is that  the attachment of 
the fitting to the wing spars does not  
involve  the drilling of the spar4 ,in  
practice this is most difficult of      
accomplishment1 for while no great      
trouble would be experienced in  making 
a fitting fulfilling this requirement1  
it would be quite another  matter to    
keep it in place under the tension of   
the bracing wires1  and in the case of  
the outer strut fitting1 to which any   
strain is  ultimately transmitted1      
practically impossible4 ,in spite of    
this1 it  must be remembered that the   
machine may occasionally1 when landing  
or  getting off1 pitch over on to the   
wing-tip skid1 and if severe1 the  shock
 transmitted to the spar may cause a    
fracture to develop which1  starting at 
the hole due to the strut fitting1 and  

owing to the fabric  covering1 would be 
difficult to detect4 ,one or two similar
 mishaps1  with a consequent increase in
 the extent of the fracture1 give       
distinct  possibilities of collapse in  
the air4 ,although one cannot give      
specific  instances1 it is a feasible   
contingency1 and one that should be     
eliminated from the region of           
possibility4    ,additional important   
features are the provision for rapid    
assembly and  detachment1 ease of       
manufacture1 and the absence of brazing1
 welding  and soldering as mediums for  
forming connections1 at least for those 
parts subject to any stress4    ,the    
qualities of strong construction and    
good design are paramount               
considerations in the manufacture of    
these fittings1 as the purpose  of an   
interstrut joint is not merely to form a
 connection between the  upper and lower
 planes1 but also to distribute the     
intricate stresses  encountered in      
flight4      ,brazing and ,welding4     

,it is somewhat amazing that brazing as 
an essential operation in the  making of
 a joint should still be employed1 as it
 is difficult to  imagine anything less 
suited to the conditions under which    
aircraft  operate4 ,the advantages of a 
uniform high-grade steel possessing a   
high  ultimate tensile strength are     
dissipated by the intense heat necessary
  for the action of brazing1 resulting  
in the strength of the finished  joint  
becoming an extremely problematic       
quantity1 indeed this is  rendered the  
more so by the individuality of the     
workmen4    ,welding properly performed 
is less objectionable1 indeed1 its use  
may  be said to be constantly           
increasing1 although it is well to      
recognize  its limitations4 ,it should  
not be used for parts subject to any    
great  tensile stress1 such as the      
fittings forming the subject of this    
chapter4 ,the efficiency of any welded  
joint is hard to determine1 as  apparent
 soundness on the surface is no         

indication of the internal  nature of   
the weld4 ,regarded from the aphoristic 
8maximum strength for  minimum weight0  
view point1 and taking into account the 
advantages in  this direction which can 
be obtained by the use of a high-grade  
steel1  brazing and welding are not to  
be commended4    ,the operation of soft 
soldering1 requiring only a moderate    
heat1 does  not weaken the material to  
any great extent1 and for some items a  
properly pegged and soldered joint is   
superior to the two methods of  jointing
 previously described4      ,connections
 in ,use4    ,illustration3 ,,fig4      
#dg4--;,interplane strut attachment4    
,the illustrations given indicate the   
varying degrees of practice1  taking as 
the standard for comparison the early   
,wright socket1 ,fig4  #dg4 ,although   
somewhat crude it was quite suitable for
 the purpose1  especially as the wing   
warping system in the ,wright machines  
necessitated a fair amount of           
flexibility in the joints4 ,it serves   

also  to illustrate that some           
advancement has been made in            
constructional  work4 ,the advantages of
 rapid erection and dismantling have    
been  realized and provided for in most 
machines since the early days of  the   
industry1 and it is not surprising1     
therefore1 that the salient             
characteristic of the joint 7,fig4 #dh7 
used by ,s4 ,f4 ,cody on his famous     
biplane was portability4 ,the interstrut
 terminates in a kind of fork1  which in
 turn is pinned to the head of a special
 bolt slotted to  receive it4 ,the fact 
that the wiring lugs were improvised    
from chain  links is interesting4       
,illustration3 ,,fig4 #dh4--;,interplane
 strut attachment4    ,the method of    
packing the wings for transport         
consisted in detaching  the two outer   
cellules from the central structure1    
when the removal  of one set of wires   
enabled the planes to be folded one     
against the  other4 ,it is possibly of  
interest to record the fact that in the 

military trials of #aiab this machine   
was taken down and re-erected in  #ea   
minutes1 quite a good performance taking
 into account its large  dimensions4    
,although this attribute is scarcely    
necessary at the  present time1 it will 
be undoubtedly required by the sporting 
owner of  the future with limited       
storage facilities4 ,the fitting shown  
by    ,illustration3 ,,fig4             
#di4--;,interplane strut attachment4    
,fig4 #di is only suitable for machines 
with light wing loading4 ,the plate     
forming the anchorage for the wires is  
pressed out1 the lugs bent to the       
different angles1 and then attached to  
the spar by an eyebolt1 to which  is    
fixed the plane strut1 the ends of the  
latter being capped with steel  tube of 
streamline section4 ,a similar          
arrangement is that shown by            
,illustration3 ,,fig4 #ej4--;,interplane
 strut attachment4    ,fig4 #ej1 the lug
 plate being pressed out and bent1 but  
in this example  the strut terminates in

 a socket of oval steel tube welded to  
the  plate4 ,it is connected to the spar
 by a bolt passing through the centre   
of the socket1 the strut end fitting    
over this4    ,illustration3 ,,fig4     
#ea4--;,interplane strut attachment4    
,the practice of anchoring wires to     
eyebolts1 as in ,fig4 #ea1 forms  the   
nucleus of many strut connections1 but  
as a method cannot be  recommended4     
,continual strain on the wire has a     
resultant in the  bending over of the   
head of the eyebolt as in ,fig4 #eb4 ,as
 a point  of fact the use of the eyebolt
 is distinctly elementary1 and gives    
the impression of a makeshift4 ,the     
fitting illustrated by ,fig4 #ec        
constitutes an advance on the previous  
arrangements dealt with1 and is  also   
indicative of modern practice4          
,illustration3 ,,fig4 #eb4--;,interplane
 strut attachment4    ,illustration3    
,,fig4 #ec4--;,interplane strut         
attachment4    ,the main body of this   
clip is a stamping from heavy           

sheet-steel1 bent  up to the section of 
the spar1 the bolts1 it will be noticed1
 passing  horizontally through it4 ,the 
anchorage for the wires is formed by    
lugs1  which have a direct pull on the  
bolts1 and is so arranged that a slight 
clearance exists between lug and spar4  
,illustration3 ,,fig4 #ed4--,plane strut
 attachment4    ,the plane-strut is shod
 with steel tubing1 and connected to the
 fitting  by a bolt1 as shown4 ,of the  
strut connections described so far1     
hardly  one can be said to conform to   
the leading principle of the ideal      
fitting1 i4e4 the secure attachment to  
the spar without piercing the  latter   
for bolts4 ,fig4 #ed gives a fitting    
which is as good a solution  of the     
problem as is constructionally possible4
 ,the basis of this  connection is the  
lug-plate1 to which is welded the       
strut-socket1  the whole being fastened 
to the spar by four bolts1 which are let
 in  the flange of the spar just half   
their diameter1 and tighten on a        

washer-plate on the opposite side4      
,lateral movement along the spars  is   
thus adequately prevented1 although the 
outer strut-socket might  conveniently  
be bolted right through the spar1       
without materially  reducing the        
strength thereof4 ,this is made possible
 by the fact that  the wing spars1      
disregarding the small wash-out at the  
extreme tip1 are  generally parallel in 
depth from root to tip1 the amount of   
material at  the point of intersection  
of the plane-strut being in excess of   
that  necessary for the stresses        
concerned4 ,another attachment achieving
  similar results is shown in the       
diagram 7,fig4 #ee71 forming an example 
of the fitting employed on the pre-war  
,avro biplane4 ,it will be noticed  that
 in this case two bolts only are used   
for the connection1 the pull  of the    
flying or lift-wires being counteracted 
by the duplicated wires  taken from the 
washer-plate to a fitting located on the
 single central  skid of the            

undercarriage4    ,illustration3 ,,fig4 
#ee4--;,interplane strut attachment4    
,head ,resistance of ,strut ,sockets4   
,a point calling for comment is the     
apparent oversight or neglect of  the   
amount of head resistance offered by the
 average strut fitting1  although great 
care is taken to ensure the strut and   
wing sections  being of correct form4   
,it seems probable that some difference 
must  occur1 especially at the high     
speeds now prevalent1 between the air   
flow across the plane and that which    
meets the strut terminal4 ,anyway1  some
 discontinuity of flow exists1 and      
whether or no the aggregate  resistance 
of all the fittings is of any great     
moment provides matter  for discussion4 
,it is quite possible to fair off any   
irregularities  in air-flow due to the  
strut connections by the attachment of  
sheet-aluminium fairings1 which could be
 beaten1 pressed1 or spun with  little  
difficulty4 ,although examples of this  
practice are very little  in evidence1  

the writer inclines to the belief that  
the additional  weight would be         
negligible compared with the ensuing    
reduction in head  resistance4    ,the  
foregoing examples cannot be said to    
constitute the latest  practice1 nor is 
it possible under present conditions to 
give such  details1 but sufficient has  
been said to indicate the progress and  
trend of design4          ,,chapter     
,,vii4    ,,wing-,,trussing ,,systems4  
,although the trussing of aeroplanes is 
carried out along certain  well-defined 
lines1 there are occasional divergences 
from the orthodox4  ,the differences now
 existing are not nearly so great as    
those of  former days1 this being       
explained by the fact that the progress 
of  any science or industry tends       
towards uniformity of method1 while     
practical experience eliminates the     
undesirable systems4 ,this does  not    
necessarily mean that the present       
methods in vogue are incapable  of      
improvement1 but merely denotes their   

suitability for present  requirements4  
,the ,pratt ,truss4    ,illustration3   
,,fig4 #ef4--,the ,pratt truss4    ,the 
basis of all modern trussing systems1   
with modifications1 is  the ,pratt truss
 7,fig4 #ef71 familiar in               
bridge-building circles1 the  basic     
principle of which is that the          
compression members are disposed        
vertically1 and while of minimum length 
are most favourably placed for          
obtaining the maximum efficiency4 ,there
 are other types of trusses  used in    
structural engineering1 as1 for         
instance1 the ,howe truss1 in  which the
 compression members are arranged       
diagonally1 and the ,warren             
lattice-type girder2 but for various    
reasons these are not applicable  to the
 needs of aeronautical engineering4 ,but
 a brief consideration  of the chief    
features of the ,pratt or box-girder    
system of trussing  will suffice to     
illustrate its great advantages for     
aircraft work1  particularly for        

machines exceeding a certain span2 and  
it is this  limiting span to which a    
monoplane can safely and efficiently be 
built  which is largely responsible for 
its present spell of unpopularity4      
,monoplane ,trussing4    ,from the      
standpoint of simplicity1 the monoplane 
equals the biplane4  ,as each wing of   
the former may be considered as a       
cantilever1 it  is the difficulty of    
adequately staying the wings above a    
certain  span which forms the deterrent 
feature1 for it is obvious that1 as  the
 span increases1 in order to obtain a   
reasonable angle for the  wires1 the    
king post1 or cabane1 must be increased 
in height4 ,this  would necessitate an  
ungainly undercarriage1 less able to    
withstand  rough landings1 with a       
consequent increase in both weight and  
head  resistance4 ,however1 it seems    
that the monoplane will have a future   
for sporting purposes1 where the span   
will not exceed #cj ft41 and will       
probably be nearer #bj ft4              

,illustration3 ,,fig4 #eg4--,monoplane  
wing bracing4    ,various attempts have 
been made to obviate this inherent      
defect of the  monoplane system of      
trussing1 the first and most popular    
being the  king-post system 7,fig4 #eg71
 in which short masts are incorporated  
in  the wing structure and wire-braced  
to the spars4 ,from the points formed   
by the crossing of the mast and spar the
 main bracing-wires are taken4  ,that   
this system is of real use is           
demonstrated by the fact that1  amongst 
others1 the ,antoinette1 ,flanders1 and 
,martinsyde monoplanes  incorporated    
this system4 ,it is worthy of note that 
this system also  characterized the huge
 ,martinsyde trans-,atlantic 'bus1 the  
wing-spread  being in the neighbourhood 
of #gj ft4 ,another original attempt at 
improvement1 the wing-bracing of the    
,deperdussin hydro-monoplane1 is of     
interest 7,fig4 #eh74 ,as regards the   
bracing1 the machine was virtually a    
biplane1 the wings being stayed by a    

steel tube running parallel with  the   
wings1 and connected to it at intervals 
by steel tubular struts1  with          
cross-bracing between1 as in a biplane4 
,the abolition of the top  wires        
rendered the machine of greater value   
for war purposes than other  tractor    
machines of that period4 ,the logical   
conclusion of this system  is           
exemplified by the ,nieuport scouting   
biplane1 the lower plane of  which      
corresponds to the streamlined steel    
boom of the ,dep4    ,illustration3     
,,fig4 #eh4--;,deperdussin monoplane    
bracing4      ,wireless ,wing           
,structure4    ,superficially1 it would 
appear that the abolition of external   
trussing  and wiring would make for     
greater aerodynamical efficiency2 and1  
constructionally1 it would be quite     
possible to build wings devoid of       
external staying1 and at the same time  
of sufficient strength4 ,but when  it is
 considered that this would entail an   
excessive depth of spar at  the root of 

the wing1 with a resultant increase of  
head resistance1  it is doubtful whether
 any appreciable advantage would accrue4
 ,in the  event of the wing becoming    
deformed or out of alignment1 re-truing 
up  would be almost impossible1 and     
would certainly require the uncovering  
of the wing and partial reconstruction4 
,contrast this with the orthodox  wire  
bracing4 ,it is simple of attachment1 of
 relatively low cost1 and  offers the   
utmost facility for truing up4 ,a       
monoplane of note1 built  without       
external trussing1 was the special      
,antoinette1 produced for the  ,french  
military trials of #aiaa4 ,this had a   
span of approximately #df  ft41 and the 
depth of spar at the root was about #b  
ft4 #c ins41 and at  the tip #i ins41   
the consequent weight alone being       
abnormal4      ,anchorage of ,lift      
,wires4    ,the one-time practice of    
anchoring lift wires to various parts of
 the  undercarriage is bad in principle1
 as there is a distinct possibility     

that a rough landing may damage the wire
 or its attachment1 and  ultimately     
cause failure in flight4 ,this practice 
undoubtedly arose  from a desire to     
obtain a good angle for the lift wires1 
a subsequent  improvement being the     
addition of a separate pylon or cabane4 
,biplane ,trussing4    ,illustration3   
,,fig4 #ei4--;,biplane ,truss4    ,the  
most common form of biplane truss is    
shown by the diagram 7,fig4  #ei71      
sometimes1 as in the case of various    
pusher types1 or those for              
long-distance work where a large wing   
area is necessary1 extended to  three   
bays each side1 which probably explains 
the partiality of ,german  designers for
 multiplicity of interplane struts1 as1 
prior to the  outbreak of the war1 the  
majority of ,german machines were       
designed and  built entirely for long   
distance and duration flying4 ,by this  
means  light wing loading1 which entails
 large wing area1 was possible without  
prohibitive weight1 for by the addition 

of a pair of struts to the  two-bay     
type1 a lighter wing spar for the same  
strength is possible4  ,in this type of 
truss the bays adjacent to the fuselage 
are varied  in width1 in order more     
easily to apportion the stresses1 which 
are  greater at the centre of the wing  
structure4 ,a modification of ,fig4  #ei
 is indicated by ,fig4 #fj1 which       
illustrates diagrammatically the        
arrangement of the ,maurice ,farman     
biplane1 the improvement consisting  of 
the method of strengthening the         
interplane struts4 ,the outer strut  is 
braced with a small king-post1 and from 
this a wire is taken through  each side 
of the strut4 ,on this machine the      
struts are of the light1  hollow-spar   
type1 and this arrangement must         
therefore materially reduce  their      
tendency to buckling4    ,illustration3 
,,fig4 #fj4--;,farman wing structure4   
,another version of this system is that 
in which the top plane is of  greater   
span than the bottom1 the extension thus

 formed being stayed  with lift and     
counter-lift wiring1 or by means of a   
strut acting in  tension and            
compression4      ,single ,strut        
,systems4    ,the almost universal      
arrangement for the small single-seater 
scout  is the single bay1 and from this 
method the progress of design has       
inclined towards the elimination of as  
many struts and wires as  possible1     
which has its culminant in the type of  
truss embodying one  strut and one pair 
of wires1 lift and counter-lift1 each   
side of  the body4 ,quite a number of   
machines have incorporated the single   
strut assembly1 the earliest perhaps    
being the ,brequet1 and one also        
remembers a small ,avro scout1 the strut
 in this case being built up  with spars
 and stringers1 covered with fabric4    
,the single-lift truss  is particularly 
suited to multiplane construction1 where
 the chord of  the wings is narrow1 and 
the bending moment1 due to the movement 
of the  centre of pressure1 is          

correspondingly reduced4 ,a disadvantage
 exists  with this form of truss similar
 to that experienced with the wireless  
monoplane truss1 i4e4 the difficulty of 
maintaining the correct  incidence from 
root to tip4 ,however1 some             
extraordinary machines of  recent       
construction embodying this feature1    
stand up to active service  demands1 so 
that this defect can be of no great     
moment4 ,a minor detail  consists in the
 circumstance of1 for example1 a lift   
wire coming adrift  or perhaps being    
shot away4 ,with the single-lift truss  
total collapse  would ensue1 but it is  
conceivable that the ordinary           
double-lift truss  offers more chances  
of escape4    ,illustration3 ,,fig4     
#fa4--,wireless wing structure4         
,another system which obviates the need 
for wires is illustrated by  ,fig4 #fa1 
which was the particular system used on 
the ,albatross 8,arrow  biplane0 of     
#aiab4 ,a drawback is the difficulty of 
readjustment1 which  is the probable    

explanation of its failure to come into 
extensive use4  ,the direct antithesis  
of this arrangement1 the elimination of 
struts1  is indicated by ,fig4 #fb2 but 
as this embodies all the defects of the 
monoplane system of trussing1 even of   
the attachment of wires to the          
undercarriage1 it must be considered of 
no practical utility4    ,illustration3 
,,fig4 #fb4--;,biplane truss without    
interplane struts4      #a ,strut       
,machines4    ,the arrangement shown by 
,fig4 #fc is responsible for the        
designation of  machines so built as 8#a
 strutters40 ,a later development of    
this system  consists of but four centre
 plane struts1 the two struts forming an
  inverted ,v between the fuselage      
longerons and centre being dispensed    
with4    ,illustration3 ,,fig4 #fc4--a  
strut wing structure4    ,the system    
7,fig4 #fd7 is illustrative of the form 
of staying in use on  a modern          
high-speed scout1 and in respect of     
which a patent is held4  ,as this       

machine is designed with a very small   
gap1 the lift wires  are consequently at
 a somewhat flat angle4 ,the strut1     
about halfway  along each wing1 is      
hinged at the point of intersection of  
the wires1  which1 incidentally1 do not 
run through from corner to corner1 but  
are  attached in the centre to a fitting
 which also forms the anchorage  for the
 struts4 ,by this method there is an    
apparent reduction in the  tendency of  
the wing spars to buckle under load     
between the points of  support4         
,illustration3 ,,fig4 #fd4--;,a patented
 wing bracing4      ,drift ,bracing4    
,so far the methods dealt with denote   
the methods of staying in a  vertical   
dimension1 and it remains to consider   
the provision for  trussing in the      
fore-and-aft direction4 ,there are two  
methods in use1  one being to brace the 
wings internally1 which is the more     
general  practice1 as by this           
arrangement the resistance of exposed   
wiring is  obviated1 while the          

alternative method consists in taking   
wires from  various points along the    
wing to the nose and rear part of the   
fuselage4      ,properties of the       
,various ,types4    ,the necessity for  
increased size1 with its inevitable     
sequence1  increased weight1 must be    
realized without a very great addition  
to  the landing speed1 the figure for   
the latter standing at approximately    
#de-ej m4p4h4 ,this factor greatly      
influences the maximum wing loading     
possible1 without detrimentally         
affecting this1 so that in the  design  
of the large machine a considerable     
increase in wing area is  unavoidable4  
,this fact practically rules out the    
monoplane system for  the large         
aeroplane1 as1 although this arrangement
 possesses a superior  ratio of lift to 
drag to that of the biplane or          
multiplane1 the great  span necessary to
 obtain the wing area is impracticable4 
,it is quite  obvious that to brace     
adequately a monoplane structure of #ajj

 ft4 span  or so1 a very complex system 
would be required1 in addition to which 
the spars would essentially be of larger
 and heavier section4 ,the  biplane     
arrangement can be used successfully for
 spans up to #ajj ft41  and1 assuming   
that the future commercial machine will 
necessitate still  greater wing area1 it
 is a feasible supposition that the     
triplane1 or  even quadruplane systems  
will be used4 ,certain modern triplanes 
have a  reputed excellent performance1  
the carrying capacity and engine power  
being colossal4 ,against this we have   
the fact that the advantage of  the     
triplane system is purely structural1 as
 aerodynamically it is not  nearly so   
efficient as the biplane1 and it is at  
this stage that the  question of the    
limiting size of aeroplanes is          
encountered4 ,various  tests1 both in   
model form and full size1 have shown    
that the lift of  the middle plane of   
the triplane system is greatly inferior 
to that of  the top or bottom planes1   

this being due to the interference of   
the  free air flow by the upper and     
lower planes4 ,this circumstance is an  
indication that the biplane arrangement1
 viewed from the standpoints of  modern 
design1 is the most economical form for 
future commercial use4                  
,,chapter ,,viii4    ,,fuselage         
,,construction4      ,the body1 or      
fuselage as it is generally described1  
constitutes the  nucleus of the         
completed machine1 and at the same time 
offers the  most interesting examples of
 constructional detail4 ,it may be as   
well  to point out that the term        
8fuselage0 is ordinarily applicable to a
  body of a machine of the tractor type2
 the short body of the average  8pusher0
 or propeller aeroplane is termed the   
8nacelle40    ,the material chiefly used
 in the construction of this component  
is  wood1 and there are but very few    
instances where metal is used4          
,fuselage ,types4    ,the different     
types or methods of construction may be 

classified in the  following order3--   
#a4 ,box-girder of four longerons or    
rails1 with cross-struts and wire       
bracing 7,fig4 #fe74    ,illustration3  
,,fig4 #fe4--;,arrangement of fuselage  
members4    #b4 ,tail portion of        
longerons1 struts and wiring2 in the    
front portion  the wire bracing is      
dispensed with1 being replaced by       
diagonal wood  bracing1 to which is     
screwed either three-ply or sheet       
aluminium alloy  7,fig4 #ff74    #c4 ,in
 this case wire bracing is entirely     
dispensed with1 the four1  and          
occasionally six1 longitudinals being   
connected together by cross  struts or  
formers cut to the required shape1 the  
whole body being  covered with          
three-ply4    #d4 ,laminated or         
monocoque type1 formed by layers of wood
 and fabric1  crossed alternately and   
glued together4    ,illustration3 ,,fig4
 #ff4--;,arrangement of fuselage        
members4      ,box-,girder ,type4       
,dealing with each type in greater      

detail1 and in order of  classification1
 the details and methods of manufacture 
of type #a may  be considered4 ,the     
longerons are usually of ash or hickory1
 although  latterly silver spruce has   
come into use for this purpose1 this    
being  due to the desire to reduce      
weight to the absolute minimum4    ,in  
the opinion of the writer1 a spruce     
longeron should be of larger  section   
than one of hard wood1 for one or two   
reasons4 ,spruce is a  soft wood1 and   
the outside fibres are far more apt to  
get damaged by  a fitting which has been
 bolted home with too much pressure1    
also the  corners may get rubbed or     
knocked off1 which all means a reduction
 in  strength4 ,the use of a spruce     
longeron precludes any sharp bends in   
the  contour of the fuselage1 as this   
wood does not lend itself to bending1   
although it may be sprung to an easy    
curve4 ,by disposing joints in  the     
longerons1 it is possible to arrange the
 lengths so that the bend  is contained 

in one portion4 ,this portion can then  
be of laminated  construction1 i4e4 it  
can be built up of a number of layers   
glued  together1 and clamped to a block 
of the required shape until the glue    
has set4 ,in some cases the longerons   
from the engine mounting to the  rear   
cockpit1 where additional strength is   
necessary1 are of ash1 while  aft of    
that1 to the stern post1 spruce is the  
material4    ,illustration3 ,,fig4      
#fg4--,longeron sections4    ,it is     
usual1 in this country at least1 to     
spindle the rails to one of  the        
sections illustrated by ,fig4 #fg1 this 
spindling or channelling  running       
through from nose to stern post1 or the 
front portion1  extending as far as the 
rear cockpit1 is left solid1 the tail   
part only  being spindled4 ,this        
channelling is always stopped at the    
intersection  of the cross-struts with  
the rails1 to provide the abutment for  
the  struts1 and the extra material to  
compensate for any holes necessary  for 

the attachment of the fitting4 ,in the  
shaping of the rails  longitudinally1   
two methods are available3 they may be  
tapered or  gradually diminished from   
the front to the stern post1 or the     
overall  section may be parallel to a   
point somewhere in the neighbourhood of 
the pilot's seat1 and from that point   
diminished to the stern post4 ,the      
first method is obsolete1 as all the    
fittings vary in size1 which makes  for 
undue complication as well as increasing
 the number of jigs and  dies necessary 
to produce the stampings4 ,the second   
method only partly  obviates this1 and  
the only system which permits of the    
same size  fitting being used right     
through is that in which the rails are  
of the  same overall section throughout1
 but this is very rarely used4          
,another arrangement consists of keeping
 the rail of equal thickness  for       
approximately #aj ft4 from the engine   
bearers1 and then diminishing  in a     
series of steps to the stern post4 ,by  

this method only three or  four sizes of
 fittings are necessary4 ,some fittings 
are not affected by  the taper of the   
rails1 and are made the same size       
throughout1 but in  nearly every case   
the attachment to the rails is          
accomplished either by  bolts or screws4
 ,the piercing of the longeron1         
particularly when this  is of spruce1 is
 hardly commendable practice1 and       
certainly in view  of the many forms of 
clip fittings in use appears to be      
unnecessary4  ,a point which apparently 
escapes the notice of some designers1 is
 the  necessity of some allowance being 
made for unfair stresses induced by     
landing shocks and rough handling4      
,there is a tendency to make the  tail  
portion separate from the front1 the    
joint occurring just aft  of the rear   
cockpit1 so that in the event of damage 
due to strains  transmitted by the tail 
skid1 this portion can be detached and a
 new  portion substituted1 which seems  
infinitely better than dismantling the  

whole machine and returning the whole   
body to the works or dept4 ,in  the     
design of the body under consideration  
due regard should be given  to the      
necessity of occasional replacement of a
 damaged rail4 ,some  fittings afford   
the utmost facility for this1 while     
others render this  procedure a lengthy 
and difficult operation4      ,jointing 
of ,longerons4    ,a popular method of  
jointing longerons consists usually of a
 plain butt  joint1 clipped with some   
form of steel tube socket1 or by        
fish-plates  flanged to clip the edges  
of the longerons and bolted through4 ,a 
spliced joint is sometimes used when    
timber is not procurable in  any great  
length1 this consisting of an ordinary  
splice from #ab to  #ah ins4 long1 glued
 and riveted1 and afterwards1 when the  
joint is  thoroughly set1 bound with    
tape soaked in glue and subsequently    
doped  and varnished4 ,as this is a     
somewhat lengthy operation the socket   
method predominates4 ,in modern         

aeroplanes the size of a longeron rarely
  exceeds #a ins4 square1 and it will   
therefore be realized that this         
construction is all that is possible1   
as1 owing to the slightness of          
material1 no advantage would accrue from
 the employment of a joint of  the      
halved or scarfed variety4              
,diagonal ,wood ,bracing4    ,a great   
deal of the foregoing applies to the    
second type1 so far as the  longerons   
and tail portion are concerned4 ,the    
diagonal wood bracing  is usually of    
spruce1 and is1 of course1 heavier than 
wiring4 ,the  aluminium or duralumin    
sheeting has latterly given place to    
three-ply  for the outside covering1    
which may be ascribed to the saving in  
weight  effected by its use1 as a square
 foot of #bj ,b4,w4,g4 aluminium1 which 
is  the general thickness for this      
purpose1 weighs #h ozs41 while a square 
foot of #c_/cb in4 birch three-ply      
weighs approximately #e ozs4 ,this      
gives a saving of #c ozs4 for every     

square foot of surface covered1 and     
moreover three-ply1 properly glued and  
screwed or copper1 nailed to  the       
framework1 constitutes by far the better
 stiffening medium4 ,the  disadvantages 
of this method of construction are3 7#a7
 the difficulty of  re-truing the front 
portion should distortion occur2 7#b7   
erection is  somewhat involved2 and 7#c7
 it is heavier than the first type1     
although  it affords a more solid       
mounting for the engine1 with a         
consequent  reduction of vibration4     
,three-ply ,fuselage4    ,the third     
system is typical of the method adopted 
for the series of  ,german ,albatross   
machines4 ,there are few1 if any1       
examples of its use  in this country1   
although prior to the war a few         
constructors favoured  its use1 and one 
successful monoplane of note was so     
built4 ,the writer  is acquainted with  
one pioneer designer who very strongly  
believes  in this form of construction1 
and certain later developments in the   

use of three-ply confirm this view4 ,the
 advantages of this form of             
construction are3 7#a7 quickness of     
production2 7#b7 great strength in  a   
vertical and horizontal direction2 7#c7 
the result of the longeron  being shot  
through would not endanger the structure
 to the same extent  as with a          
wire-braced system4 ,against this must  
be balanced the fact  that3 7#a7 it     
entails a considerable increase in      
weight2 7#b7 is weak  under a torsional 
strain1 such as that produced by the    
combined actions  of elevator and       
rudder2 and 7#c7 cannot be trued up in  
the event of  distortion4 ,examples of  
this system in pre-war machines are     
afforded by  the ,martinsyde and        
,blackburn monoplanes1 although the     
framework in both  cases was so formed  
as to constitute a lattice girder4 ,the 
tail portion  of the ,martinsyde was    
lightened by cutting away diamond-shaped
 pieces  from each bay4    ,the formers 
of the ,albatross are extremely simple4 

,in the fore part  they are cut from    
three-ply1 while at the rear they are   
just simple  frames composed of laths1  
reinforced where the longerons occur by 
three-ply stiffeners4 ,there are six    
longerons1 the two middle ones  being   
fixed slightly more than halfway up each
 side1 which are really  longitudinal   
stringers to prevent the three-ply      
buckling between the  points of         
attachment4      ,the ,monocoque ,type4 
,the monocoque system originated in     
,france1 several constructors having    
produced machines incorporating this    
feature4 ,the most successful  machine  
produced on these lines was the         
,deperdussin1 and many will  recall the 
excellent streamline form of the machine
 exhibited at  the #aiac ,aero ,show4   
,these bodies were built over formers of
 various  sections1 which were removed  
when the glue joining the different     
layers  had set4 ,the resultant shell1  
which was about four millimetres thick1 
was then covered with fabric and        

varnished4 ,several factors militate    
against its extensive adoption as a     
method4 ,it is rather costly1 and  does 
not seem to be suited to rapid          
production4 ,in addition1 the           
attachment of such members as the       
chassis1 wings1 and interplane  struts1 
is more complicated4 ,it should be      
noted1 however1 that various  modern    
machines are similarly built4 ,the      
,borel firm produced a machine  with    
monocoque body1 this being composed of  
three-ply covering on  ribs running     
diagonally the length of the body1 and  
although this is  not such a lengthy    
operation as the ,dep4 system1 it has   
not survived1  unless one considers     
flying-boat construction as its modern  
version4  ,a slight variation of the    
monocoque system is used for the bodies 
of  some modern aeroplanes4 ,the        
framework consists of very small        
stringers  arranged at various points on
 light formers cut to the fuselage      
section4 ,to this structure is applied  

two thicknesses of three-ply in  the    
form of strips about #c ins4 wide1 each 
thickness being disposed  diagonally in 
opposite directions1 as shown by ,fig4  
#fh4 ,this is covered  with fabric1 the 
total thickness being no more than #a   
mm41 and as this  is made up of six     
layers of wood and one of fabric1 the   
fineness of the  ply-wood will be       
realized4    ,illustration3 ,,fig4      
#fh4--;,arrangement of three-ply bands  
in monocoque  fuselage4    ,it should be
 noted that the ply-wood strips do not  
completely encircle  the formers1 but   
are jointed at the top and bottom1 a    
light longeron  being arranged at these 
points4    ,a detail which would appear 
to be of great utility at the present   
time is the arrangement wherein the nose
 of the body containing the  engine and 
accessories is a separate unit1 and in  
the event of engine  breakdown can be   
detached and another substituted4       
,fuselage ,contours4    ,in the design  
of the contour of the fuselage the type 

of the motor  used is the determining   
influence4 ,with the vertical 8in line0 
engine1  it is possible to design a slim
 narrow body1 while a rotary or radial  
engine necessitates an increase in      
width1 which also means increased  air  
resistance4 ,with the ,vee type engine1 
the popular practice is to  allow the   
tops of the cylinders to project through
 the cowling1 which  permits of a       
narrower body than if the width of the  
body equalled the  overall width of the 
engine4 ,where a rotary engine is       
employed and  the mounting is of the    
overhung type1 the width of the fuselage
 may  be reduced by allowing the engine 
to project over the sides1 and the      
cowling carried on an arrangement of    
formers and stringers1 which  gradually 
merges into the main structure1 as in   
,fig4 #fi4 ,it is apparent  that the    
line of the body and that of the fairing
 should converge as  gradually as       
possible1 as1 should this be at all     
abrupt1 there is a  distinct possibility

 that the air flow will take the course 
indicated  in ,fig4 #gj1 resulting in a 
dead air region and inefficiency4       
,illustration3 ,,fig4 #fi4--;,fuselage  
outline4    ,illustration3 ,,fig4       
#gj4--;,fuselage outline4    ,it may be 
taken generally that the wider the body 
the greater the  weight1 for the struts 
have not only to be made longer but also
 of  greater overall section4 ,the      
practice in this country is to keep the 
longerons parallel to the centre line on
 plan1 as far as the rear  cockpit1     
tapering from that point to the stern   
post in a straight or  slightly curved  
line1 as ,fig4 #ga4    ,illustration3   
,,fig4 #ga4--;,fuselage outline4        
,this simplifies the fittings1 the      
sockets for the centre plane struts  are
 in line1 and the different lengths of  
fuselage struts necessary  reduced to a 
minimum4    ,illustration3 ,,fig4       
#gb4--;,fuselage outline4    ,the plan  
outline of several ,german machines is  
shown diagrammatically  by ,fig4 #gb4   

,it will be seen that from the nose the 
body gradually  widens out until the    
maximum width1 generally in the vicinity
 of the  front seat1 is reached1 from   
where it tapers to the tail4 ,this shape
  appears to satisfy aero-dynamic       
requirements more closely than either   
of the foregoing examples2 but in       
practice the difference is not          
appreciable1 and in any case the        
reduction of head resistance does not   
compensate for the additional work4     
,illustration3 ,,fig4 #gc4--;,fuselage  
outline4    ,illustration3 ,,fig4       
#gd4--;,fuselage outline4    ,in side   
elevation the general practice1 with    
exceptions1 is to arrange  the top      
longerons parallel to the line of       
thrust1 i4e4 the axis  of the motor1 as 
in ,fig4 #gc4 ,this simplifies erection 
and affords a  convenient datum line for
 truing up4    ,illustration3 ,,fig4    
#ge4--;,fuselage outline4    ,on the    
,german ,rumpler and early ,albatross   
biplanes1 the upper longerons  are      

curved1 as in ,fig4 #gd1 but in the most
 recent versions of the  ,albatross they
 are level with the line of thrust4     
,fig4 #ge illustrates  an arrangement   
where the top rails1 from a point some  
distance along1  slope down to the nose4
 ,by this method the body weight is kept
 as low  as possible and the engine and 
accessories rendered more accessible4   
,although it is usual to terminate the  
body in a vertical knife-edge1  formed  
generally by the rudder post1 another   
arrangement1 typical  of the ,morane    
monoplane1 finishes in a horizontal     
edge4 ,the ,german  ,fokker1 obviously  
inspired by the ,french ,morane1 and the
 ,albatross  ,,di1 are similarly        
terminated4 ,this system of tapering to 
a horizontal  knife-edge is not         
considered the best arrangement from a  
strength point  of view1 the flat angle 
of the bracing wires permitting a       
certain  amount of movement1 eventually 
resulting in slackness and loss of      
alignment4          ,,chapter ,,ix4     

,,fuselage ,,fittings4      ,the design 
and type of fitting employed for        
connecting the longerons1  cross and    
vertical struts of the fuselage1 varies 
greatly1 being  usually one of the      
distinctive constructional details of a 
machine4  ,this position renders        
uniformity of practice a comparatively  
unattainable quantity1 which1 in view of
 present requirements1 and  the absolute
 need of rapidity of output 7which must 
commence as soon  as possible after a   
successful design is produced71 can only
 be  considered as regrettable4 ,this   
diversity of design is mainly the       
result of the desire for originality of 
each individual designer1  and however  
commendable from this standpoint1 is a  
position which is  almost certain to    
disappear with the progress of the      
industry4 ,take as  a hypothesis the    
case of1 say1 ten makes of scouting     
biplanes in use1  each with             
approximately the same arrangement of   
longerons and struts1  and with a       

similar overall size of fuselage4 ,each 
of these machines  will incorporate a   
different fuselage clip1 which means    
that somewhere  highly skilled labour is
 being unnecessarily expended in the    
making  of jigs and press tools1 whereas
 a suitably standardized clip for all   
scout machines of certain dimensions    
would involve the making of one  set of 
press and bending tools only for the    
machines of the one type  built4        
,another aspect1 quite as important1 is 
the simplification of  the supply of    
spares4 ,acceleration of aircraft       
output1 if achieved  only through the   
medium of small part production1 is one 
of the most  important contributary     
factors towards ultimate success in the 
field4      ,types in ,use4    ,the     
sketches1 explained in detail hereafter1
 are illustrative of some  of the many  
systems in use1 and taken collectively  
fall under two  categories3 7#a7 those  
in which attachment to the longeron     
involves  drilling1 and 7#b7 those in   

which the fitting clips or encircles the
  longeron1 friction only keeping it in 
position4 ,the first method  permits of 
a clip of comparatively simple design1  
but it has the  serious disadvantage of 
weakening the material1 and assuming the
  longeron section is sufficient to     
account for this1 then clearly a        
fitting which is attached without the   
use of bolts would allow a  reduction in
 the size of a longeron 7which means a  
saving in weight7  without depreciating 
the factor of safety4 ,in the second    
method the  attachment is usually       
accomplished by the pressure of bolts1  
with  practically no weakening effect2  
but in this case the disadvantage lies  
in the fact that at each point of       
attachment a differently dimensioned    
clip will be necessary1 this being due1 
as explained in the previous  chapter1  
to the longeron tapering towards the    
stern post4 7,a method  of reducing the 
number of different clips by suitably   
shaping the  longeron was also dealt    

with47 ,it is evident that most fittings
 must  inevitably form a compromise     
between the demands of production and   
design1 although it must be admitted    
that in some cases the fittings         
collectively very successfully evade the
 requirements of both4    ,illustration3
 ,,fig4 #gf4--;,fuselage fitting4       
,the clip indicated by ,fig4 #gf is the 
particular form of construction         
associated with the various versions of 
the ,bleriot monoplane1 and  favoured by
 the early pioneers generally4 ,it was  
retained in the  ,bleriot construction  
until some time after the outbreak of   
the war--as  a matter of fact1 until the
 type was deleted for war purposes4     
,it is composed1 as will be seen from   
the sketch1 of simply two ,u-bolts1  the
 attachment to the longeron involving   
the drilling of four holes1  which      
constitutes the chief objection to this 
particular form of  clip1 and has been  
the subject of criticism from the time  
of its  first appearance as an aircraft 

detail4 ,the struts are slotted over    
the bolt1 and although this does not    
conform to the best principles1  it is  
simple1 and may have been sufficient for
 a lightly loaded  machine4 ,a point    
about this clip1 which undoubtedly was  
the cause  of its popularity amongst the
 pioneers1 with whom economy was an     
evil necessity1 is that the wires can be
 strained or tensioned by an  adjustment
 of the nuts on the longerons1 thus     
rendering turnbuckles    ,illustration3 
,,fig4 #gg4--;,fuselage fitting4        
unnecessary4 ,fig4 #gg shows the form of
 clip used on the ,hanriot  monoplanes1 
and is a good example of the class of   
fitting bent up  from sheet metal4 ,this
 is usually made to be slightly smaller 
than  the longeron1 the pressure        
resulting from the tightening of the    
bolts  on the ends forming the          
cross-bracing lug1 keeping it in place4 
,the  defect of this arrangement is that
 any slight shrinkage of the longeron   
will permit movement1 and for this      

reason provision should be made for  the
 subsequent adjustment of the bolts4    
,the struts are taken by the  lugs      
punched up from the body of the clip4   
,this leaves very little  material to   
resist the tension of the bracing wires 
or tierods1 but a  modification of this 
clip surmounts this difficulty4         
,illustration3 ,,fig4 #gh4--;,fuselage  
fitting4    ,a similar clip is used by  
the ,german ,aviatik firm1 but it is    
certainly  inferior owing to the very   
poor connection of the struts4 ,instead 
of  the four lugs gripping the sides of 
the struts1 they are punched up to  form
 a square or tenon1 over which the      
cross-struts are mortised4 ,in  any case
 it would not satisfy the standards     
maintained by our leading  constructors1
 and certainly not the technical        
advisers to the ,air  ,board4 ,the clip 
indicated in ,fig4 #gh does not encircle
 the longeron1  but abuts against the   
two inner sides of the longeron only4   
,the body  of this clip is a stamping1  

bent to a right angle1 to which the     
square  sockets for the struts are      
welded4 ,attachment to the longeron is  
effected by an eyebolt1 which passes    
diagonally through it1 this also        
providing the anchorage for the         
cross-bracing wire4 ,a form of this     
clip has been used on a certain make of 
machine for a considerable  period1 so  
that it has advantages that are not     
readily apparent4 ,one  outstanding     
defect is existent in that the pull of  
the wires would tend  to lift the socket
 on the side opposite to the eye bolt1  
and this in  turn would cause distortion
 of the struts4 ,a connection favoured  
by an  ,american firm is shown by ,fig4 
#gi1 and possesses the merit of extreme 
simplicity4 ,the longerons are not      
drilled1 the attachment being through   
the agency of an ,l bolt1 which also    
provides the anchorage for the          
cross-bracing wire4 ,to prevent movement
 the clip is additionally fixed  to the 
longeron by wood screws4                

,illustration3 ,,fig4 #gi4--;,fuselage  
fitting4    ,illustration3 ,,fig4       
#hj4--;,fuselage fitting4    ,the method
 shown by ,fig4 #hj is that used on the 
,deperdussin monoplanes1  being patented
 by that firm as far back as #aiab1 and 
consists of two  cast aluminium sockets1
 bolted to the longeron4 ,the struts1 in
 this  case oval in section1 are        
fastened in place by steel bushes1 which
  are driven through in the form of     
steel tube1 and expanded and burred     
round the socket1 at the same time      
forming the anchorage for the  wires4   
,this system has been used in the       
construction of a fast scout  of        
comparatively recent origin1 but it     
embodies the same defects as  the       
,bleriot clip1 i4e4 four holes are      
needed in the longeron for  every joint2
 but it has the advantage over the      
latter in that a better  terminal is    
provided for the struts4                
,illustration3 ,,fig4 #ha4--;,fuselage  
fitting4    ,fig4 #ha indicates the     

arrangement on the ,german ,l4,v4,g4    
7,luft-,verkehrs-,gesellschaft7 fighting
 biplane4 ,this is an aluminium  alloy  
casting1 fastened to the longeron by    
screws1 and as it is not  affected by   
the taper of the longeron1 all the      
fittings1 or at any  rate1 those in the 
tail portion1 can be of the same        
dimensions4 ,a  point which is often    
overlooked when using a fitting of this 
type is  that any strain on the wires is
 transmitted to the longeron by the     
fastening screws only1 or1 in other     
words1 the tendency of the wires  when  
tensioned to pull the fitting from the  
longeron is resisted by the  screws     
only4 ,this does not impress one as     
being well suited to perform  the       
functions demanded of the average joint1
 and about the only detail  upon which  
its existence is justified is its ease  
of production4 ,in the  writer's opinion
 the clip1 ,fig4 #hb1 is by far the     
finest connection  yet devised1 and one 
that should be standardized4 ,its       

attachment is  accomplished without     
objectionable drilling2 it provides an  
excellent  housing for the cross-struts2
 can be tightened up should shrinkage   
occur in the longerons2 and can be      
produced at an absurdly low figure4     
,this clip has been used on machines    
which have accomplished some  meteoric  
performances during the war1 and1       
moreover1 was designed and  in use a    
considerable period before the war4     
,illustration3 ,,fig4 #hb4--;,fuselage  
fitting4    ,illustration3 ,,fig4       
#hc4--;,fuselage fitting4    ,the clip1 
,fig4 #hc1 is simple and quite easily   
manufactured1 being  stamped out of     
sheet metal1 and bent up to shape4 ,the 
lugs forming the  anchorage for the     
wires would have a tendency to          
straighten out at  the bends2 but the   
amount of this1 whether serious or      
otherwise1 in  the absence of actual    
experience1 is largely conjectural4     
,however1 a  fitting of this kind was   
used in the construction of the nacelle 

of a  seaplane exhibited at ,olympia in 
#aiad4      ,steel ,tube ,fuselage      
,construction4    ,illustration3        
,,welded      ,,wires #ah ,,bwc         
,,fig4 #hd4--,welded joint in steel tube
 fuselage4    ,in certain isolated      
instances1 the fuselage is built up of  
steel  tubing1 and on one machine of    
recent design the joints throughout are 
effected by welding3 a detail of the    
attachment of the vertical and  cross   
struts to the longerons is shown by     
,fig4 #hd4 ,it will be noticed  that a  
small quadrant-shaped piece of tube or  
rod is welded to the  struts1 and from  
this are taken the bracing wires4 ,as   
the welded joints  impart a certain     
rigidity to the structure1 the fact that
 the wires  are exerting a side pull on 
the struts may be of little consequence1
  although this method could hardly be  
used in conjunction with the  fuselage  
construction of average ,english        
machines4 ,a rather unusual  feature may
 be noticed in the attachment of the    

bracing wires1 which  are not finished  
off with the orthodox wire ferrule1 but 
are arranged  as a loop1 the turnbuckle 
forming the anchorage for the two ends4 
,the trend of design in this country    
seems to incline towards the clip       
stamped out from sheet steel and bent   
up4 ,this class of fitting can be       
produced accurately and quickly1 and1 in
 the writer's opinion1 is by  far the   
best manufacturing proposition4         
,aluminium castings are quite  obsolete1
 and the built-up fitting1 involving    
welding or brazing1 does  not seem      
greatly in vogue4          ,,chapter ,x4
    ,,undercarriage ,,types4      ,the  
present chapter deals with the general  
arrangement of the different  types of  
undercarriages1 as distinct from the    
details of construction4  ,the          
principles of design embodied in the    
undercarriage are necessarily  a        
compromise1 this position being due to  
the fact that its construction  has to  
be considered from two distinctly       

opposed view-points1 and  undue         
attention to the requirements of either 
does not produce the  best results4     
,thus1 on the one hand1 we have the     
desirability of great  strength to      
withstand landings on very rough ground1
 ploughed fields1  and the like2 and on 
the other hand1 we have the             
considerations of  aerodynamical        
efficiency in flight1 which1 taken to   
one extreme1 would  be best satisfied if
 the undercarriage did not exist1 and at
 most calls  for a system in which the  
head resistance is brought to an        
irreducible  minimum4 ,by the ordinary  
process of evolution the agglomeration  
of  ideas existing in the early days of 
flying with regard to the most  suitable
 form of landing gear1 have given place 
to something which1  for machines of    
modern attainments1 approaches finality4
 ,this has  resulted from improvements  
along the line of 7#a7 simplification of
  general design1 7#b7 the reduction of 
head resistance and weight without  a   

consequent diminution in its powers as  
an alighting gear4 ,a better  impression
 of the distinguishing points of the    
various types will be  gathered if we   
consider the desiderata of an ideal     
undercarriage4      ,principles of      
,design4    ,one of the most important  
points is that rolling shocks should be 
completely absorbed1 and the least      
possible strain transmitted to  the     
fuselage or main structure1 this calling
 for a good system of  wheel suspension4
 ,it must be capable of standing the    
considerable  strains sustained in      
alighting1 not the least of which are   
those  attendant upon landing in a side 
wind2 should offer the least possible   
head resistance1 while the weight must  
be reduced to a minimum4  ,cross-country
 flying1 which more often than not means
 8getting off0 in  a restricted space1  
requires that the machine shall attain  
flying speed  in the shortest time1 and 
conversely in alighting the machine     
should  come to rest in the quickest    

time4 ,innumerable smashes have been    
caused  after a perfectly good landing  
by failure to pull up before a hedge1   
fence1 or ditch4 ,these are the main    
principles involved1 and at least  they 
indicate how and why the undercarriage  
is necessarily a compromise4            
,illustration3 ,,fig4 #he4    ,it is    
clear that in landing the speed of the  
machine relative to  the ground should  
be as low as possible1 without          
developing into  the operation generally
 known as 8pancaking10 or stalling1 and 
the  usual method of accomplishing this 
is to bring the machine into the  wind1 
which1 if of a moderate velocity1       
materially reduces the speed  relative  
to the earth4 ,in ordinary              
circumstances1 landing would be         
accomplished by gradually increasing the
 angle of incidence until the  maximum1 
or angle of no lift1 is reached1 which  
is practically stalling  point4 ,to     
satisfy this consideration1 the heights 
of the main rolling  wheels and tail    

skid should be arranged to allow the    
wings to lie at  an angle a little in   
excess of this4 ,with modern wing       
sections the  angle of maximum lift is  
between #ad and #af1 so that the angle  
of  #ah1 as shown in ,fig4 #he1 is      
usually sufficient4 ,this has additional
  value in restricting the length of run
 after contact with the ground1  the    
wings acting as air-brakes4 ,it will be 
realized that reduction  in height of   
the undercarriage1 desirable as it is   
from the aspect  of head resistance1    
cannot be carried beyond a certain point
 without  the sacrifice to some extent  
of the foregoing qualities4 ,so far we  
have taken the principles of design as  
affecting the disposition  of the       
undercarriage members in a longitudinal 
direction1 but1 of  course1 there are   
several details to be considered in its 
arrangement  laterally4 ,a fundamental  
point is that the track of the wheels1  
i4e4  the distance1 centre to centre1   
should be of ample width1 but several   

constructional difficulties tend to     
restrict this to certain limits4  ,where
 the undercarriage is of the type in    
which the main rolling  wheels are      
mounted on a single axle1 it is clear   
that the wheel base  is limited to the  
greatest length the steel or duralumin  
tube can be  used without buckling under
 landing shocks4 ,if this is to be      
exceeded a  bigger diameter tube of     
thicker gauge will be necessary1 and    
this means  additional weight4 ,again1  
the fuselage width for the tractor      
machines  now in vogue does not greatly 
exceed #c ft41 being more usually under 
that figure1 so that a very wide base   
would mean raking the struts  at a flat 
angle1 which would therefore require to 
be made of larger  section than would be
 the case if the wheel base was         
narrower2 or1 if  the same section strut
 is used1 the strength is reduced4 ,a   
wide wheel  base therefore means an     
undesirable increase in weight and      
resistance4  ,to make up for the        

deficiencies of the almost unavoidable  
narrow wheel  base1 it is usual to make 
use of the wing tips by fitting skids of
  malacca cane or laminated ash1 which  
are brought into action when the        
machine is excessively canted over      
sideways4 ,at one time the wing tips    
were almost invariably used to assist   
the undercarriage1 the wing tips  of the
 ,nieuport monoplane being specially    
constructed for the purpose1  and no    
skids were fitted4 ,earlier still the   
,r4,e4,p4 monoplane had only  one       
central rolling wheel1 a smaller wheel  
being attached to each  wing tip4 ,the  
wing tip wheels of the ,cody biplane    
performed similar  functions1 although  
these were used in conjunction with two 
main  wheels4      ,undercarriage       
,types4    ,the type of landing gear in 
use to-day does not vary in principle to
  any great extent1 the differences     
usually occurring in the choice  of     
material1 the system being that usually 
known as the ,vee type1  from the fact  

that viewed in side elevation1 the      
struts form a  ,v4 ,while this type has 
much to commend it from the points of   
low  head resistance and great strength 
for weight1 there are other  systems1   
some of which have been tried-out1 while
 others still  exist1 incorporating     
features designed for some specific     
purpose4 ,of  these the ,farman type is 
an example of a landing gear designed   
for  the requirements of school work1   
consisting of two long ash skids1       
which1 extended from the rear end of the
 nacelle1 being gradually  bent upwards 
to carry the front elevator4 ,this was  
the arrangement  on the 8,longhorn0     
machine1 but on the 8,shorthorn10       
produced at    ,illustration3 ,,fig4    
#hf4--,side view of ,farman landing     
gear4    a later date1 the skids1 as    
shown by ,fig4 #hf1 terminated in short 
bends4 ,each skid carried a pair of     
rolling wheels1 attached to a  short    
axle1 this being bound to the skids by  
rubber bands4 ,the  wheel base being    

almost #i ft41 this type gave excellent 
results4  ,in the case of big machines1 
where it is desired to keep the load  on
 the tail skid as light as possible1    
three wheels are sometimes  used1 two   
main rolling wheels and a light pilot   
wheel in the front4  ,this enables the  
main rolling wheels to be placed under  
the centre  of gravity1 the pilot wheel 
preventing the consequent tendency to   
pitch forward when rolling4 ,a further  
development of this system  dispenses   
with the tail skid1 two main wheels     
being placed under  the centre of       
gravity1 and two smaller wheels a little
 forward of    ,illustration3 ,,fig4    
#hg4--,side view of four-wheeled landing
 gear4    the propeller1 as in ,fig4    
#hg4 ,the skids were sometimes continued
 back  behind the rear struts1 and      
saw-kerfed to increase the resiliency4  
,the base of support was formed by the  
rear wheels and the ends of the  skids1 
the machine being pulled on to the front
 wheels by the thrust  of the propeller4

 ,the short wheel base is bad for       
rolling on bumpy  ground1 and frequent  
skid replacements are necessary with    
this system4  ,a similar type with no   
tail skid has the wheels disposed       
forward of the  ,c4,g41 while a single  
central skid1 connected to the fuselage 
by    ,illustration3 ,,fig4 #hh4--,side 
view of ,nieuport undercarriage4    a   
series of ,v struts1 replaced the double
 skids1 as in ,fig4 #hh4 ,this  type was
 used on the original ,nieuport         
monoplane1 and with minor  modifications
 on the ,avro #hj h4p4 ,gnome tractor   
biplane4 ,its chief  advantage is low   
head resistance1 but unfortunately with 
this system  a narrow wheel base1 with  
the attendant defects1 is inevitable4 ,a
  very distinctive system was that      
favoured by ,bleriot1 and used with     
minor alterations on all the ,bleriot   
monoplanes4 ,this is shown1             
diagrammatically1 in side elevation1 by 
,fig4 #hi1 and was unusual in  that the 
wheels were arranged to swivel1 this    

being an attempt to  counteract the side
 strains set up when landing in a side  
wind4  ,although in the hands of some of
 our most famous exhibition pilots this 
has functioned excellently1 it is       
complicated and somewhat heavy4         
,illustration3 ,,fig4 #hi4--;,bleriot   
undercarriage4      ,recent             
,developments4    ,during the last three
 years the vital necessity of speed and 
climb1 and  more speed and climb1 has   
resulted in the gradual elimination of  
skids1  struts1 and wires1 until to-day 
the chassis for machines of average     
dimensions is almost invariably the ,v  
type 7,fig4 #ij74 ,the wheels are       
placed about a foot in front of the     
,c4,g41 as1 owing to the absence of  any
 forward skid1 no other provision exists
 to counteract the tendency  to pitch   
over4 ,in the actual construction of the
 ,vee undercarriage1  some diversity of 
practice exists with regard to the      
material chosen4  ,in some cases the    
struts forming the ,vees are constructed

 of a  streamline section steel tubing1 
in others round tubing1 the streamline  
section being obtained by a wooden      
fairing bound on1 while a number of     
constructors use wood for the struts4   
,illustration3 ,,fig4 #ij4--,vee type   
undercarriage4          ,,chapter ,,xi4 
,,undercarriage ,,details4      ,the    
details of construction associated with 
the undercarriage are  those concerned  
with the forming of the struts and main 
members1 and  the suspension of the     
axle4 ,as noted in the previous chapter 
the ,vee  undercarriage is greatly in   
favour at present1 but the fact that    
with  this type no forward support      
exists to prevent pitching over when    
obstructions are met in rolling1 will   
almost certainly result in  some        
arrangement of wheels and skids for the 
touring machines of the  post-war       
period4 ,machines are now designed for  
air performance pure and  simple1 so    
that an undercarriage of the simple ,vee
 type is all that is  permissible2 but  

in the post-war machine general utility 
will be the  desideratum sought for by  
designers4 ,at one time the majority of 
the  undercarriage arrangements         
incorporated one or more skids4 ,the    
material  most suited for this purpose  
is hickory1 although some designers     
prefer  ash1 steamed to the desired     
curve1 and generally channelled out     
between  the points of intersection of  
the struts1 fittings1 etc41 in a similar
  manner to longerons and wing spars4   
,where the bend is sharp1 and therefore 
difficult to obtain by steaming1  it is 
usual to form the skid from a number of 
strips1 or laminations1  glued together4
 ,quite a good method of stream-lining  
the curved toe of  the skid is shown by 
,fig4 #ia1 consisting of a spruce block 
attached to  the skid by screws1 and it 
has additional value in ensuring        
permanency  of curve4 ,where the design 
is such that the rear end of the skid   
performs the functions of a tail skid it
 is saw-kerfed1 as in ,fig4  #ib1 the   

laminations so formed being stepped     
back1 and the bottom  layer shod with a 
plate1 or claw fitting1 acting as a     
brake1 and also  preventing wear        
produced by contact with the ground4 ,at
 one time this  constituted popular     
practice1 but it is a matter of some    
difficulty  to prevent the saw-cuts from
 developing into fractures4 ,as a matter
  of fact1 on one type of machine       
replacements were so frequent that      
eventually the skid end was left solid4 
,illustration3 ,,fig4                   
#ia4--,streamlining curved toe of skid4 
,illustration3 ,,fig4 #ib4--,laminated  
skid end4      ,methods of ,suspension4 
,in the preliminaries of design referred
 to in the last chapter1 it was         
observed that the action of rolling and 
alighting called for a good  system of  
suspension and shock absorption1 and    
this is accomplished  on modern machines
 by binding the axle to the main members
 of the  structure with either rubber   
cord 7this being a number of strands  of

 rubber about #a_/af in4 square1        
compressed and bound together with  a   
woven twine casing7 or plain rubber     
rings4 ,the latter are more or  less    
obsolescent1 at least in this country1  
the reason being found in  the better   
lasting qualities of the cord1 which    
will also withstand a  much higher      
ultimate stress1 the fabric covering    
contributing largely  to this4 ,in a    
number of cases1 and generally for heavy
 machines1  steel helical springs are   
fitted4 ,various attempts right from the
  beginning of successful flight have   
been made to utilize steel springs  for 
suspension1 but hitherto very few       
machines have successfully  incorporated
 them1 and but a brief examination will 
show that their  use on machines of the 
average modern type is attended with    
some  unsatisfactory features4 ,firstly1
 they are much heavier than rubber1  but
 this in itself is no great             
disadvantage1 as ease of attachment     
probably compensates for this2 but what 

is of moment is the fact that  steel    
springs are not nearly so efficient     
shock-absorbers as the  rubber variety1 
while even the efficiency of the latter 
is capable of  considerable improvement4
 ,if we take the case of a machine      
rolling  over bumpy ground1 all that is 
required of the suspension is that  the 
wheel movement over the inequalities    
shall not be transmitted to  the whole  
machine4 ,so far both steel springs and 
rubber cord satisfy  these conditions1  
but in the operation of alighting the   
machine not  infrequently strikes the   
ground with some force1 sometimes the   
result  of gusts or pancaking4 ,with    
steel springs1 and to a lesser degree   
those of rubber1 the energy of landing  
is not absorbed1 but is stored  up1     
being given out again in the form of a  
rebound4 ,with rubber1  elongation and  
its consequent depreciation of ultimate 
tensile strength  prevents any energy of
 moment being returned to the aeroplane1
 which is  why1 for light machines of   

modern design1 say1 up to #bejj lbs4    
total  weight1 rubber is the better     
material4 ,steel springs being deficient
  in the power to damp out shocks1 it   
becomes necessary to use these  in      
conjunction with some other medium      
possessing this quality1 and  one of the
 most suitable arrangements extant is   
that known as the  oleo-pneumatic gear1 
consisting of a combination of helical  
coil spring  and oil plunger4 ,it is    
usual to arrange the main compression   
members in  two halves1 the upper half  
forming a piston1 and the lower1        
attached to  the wheels1 constituting   
the cylinder1 is filled with oil4 ,the  
weight  of the machine is taken normally
 during rolling by the helical spring1  
wound round the upper half of the       
telescopic tube4 ,excessive shocks      
cause the oil to be forced through a    
spring valve1 adjusted to open at  a    
certain pressure1 into the upper half1 a
 back-pressure valve enabling  the oil  
to gradually return to the cylinder4    

,the ,breguet biplane1 a  pre-war       
machine of original design1 embodied in 
the undercarriage  arrangement a system 
analogous to the foregoing4      ,shock 
,absorbing ,effect of ,tyres4    ,the   
assistance rendered by tyres of large   
diameter must not be  overlooked4 ,the  
merits of the large tread are quite well
 known in  the sphere of the motor-car1 
and they are no less beneficial to the  
aeroplane4 ,it is of interest to record 
that a pre-war racing machine  had no   
other suspension and shock-absorbing    
medium than that provided  by the very  
large tyres fitted to the wheels1 the   
axle being fixed  rigidly to the        
undercarriage struts4 ,a similar        
arrangement existed on  a machine of    
much more recent date4 ,one does not    
advocate this system1  as it can be of  
very little use for rough ground1 the   
instance being  cited to emphasize the  
assistance so rendered to the ordinary  
type of  suspension4      ,connections4 
,various methods exist for connecting   

the rubber to the main members1 a       
typical arrangement with the ,vee       
undercarriage of steel being shown by   
,illustration3 ,,fig4                   
#ic4--;,arrangement of suspension on    
steel tube  undercarriage4    ,fig4 #ic1
 and a variation of this1 when wood is  
the material1  is indicated by ,fig4    
#id4 ,the web plate in ,fig4 #ic forms  
a means for guiding the axle in its     
upward travel1 and is  another version  
of the one-time popular                 
,illustration3 ,,fig4                   
#id4--;,arrangement of suspension on    
wood  undercarriage4    radius rod4 ,it 
is not considered necessary1 in many    
instances1 to  fit either web plate or  
radius rod1 the movement of the axle    
,illustration3 ,,fig4 #ie4--;,farman    
type axle suspension4    being of no    
great extent4 ,another system is shown  
by ,fig4 #ie1  this being the method of 
suspension adopted for the ,farman      
,illustration3 ,,fig4 #if4--,rubber cord
 suspension4    machines4 ,in this case 

rubber bands are attached to the main   
skids1 the  short axle passing between  
the two4 ,a similar arrangement in      
general  outline is shown by ,fig4 #if1 
although in this case the rubber takes  
the  form of cord4    ,illustration3    
,,fig4 #ig4--;,bridge type suspension4  
,a method greatly in vogue in ,america  
is that indicated by ,fig4 #ig1  known  
as the bridge type1 and a characteristic
 ,wright detail1 the rings  being       
approximately two inches wide by two    
inches long4 ,the fact that  very few   
examples of this system exist in this   
country may be ascribed  to the         
inferiority of rubber bands compared    
with the rubber cable4      ,axle       
,fairings4    ,illustration3 ,,fig4     
#ih4--;,axle fairing4    ,it is now the 
practice to streamline the compression  
tubes between the  vees of the          
undercarriage with a fairing of         
aluminium or three-ply4  ,this is so    
arranged that in flight the axle lies in
 a slot formed in  the fairing1 which   

appreciably reduces head resistance4 ,a 
typical  arrangement is indicated by    
,fig4 #ih4 ,the axle is usually formed  
of steel or duralumin tube1 and in the  
majority of undercarriage  arrangements 
is divided and hinged in the centre1 a  
wire or wires from  this point to the   
fuselage accounting for any strain4     
,duralumin tube is  especially suited   
for this item1 as a much stiffer axle is
 possible for  a given weight1 although1
 unfortunately1 this is slightly        
discounted by  the fact that duralumin  
does not form a good bearing surface for
 the  wheel hubs1 and it therefore      
becomes necessary to fit either sleeves 
or  stub-axles of steel4                
,undercarriage ,brakes4    ,additional  
means for restricting the length of     
travel after contact  with the ground is
 sometimes found in the employment of   
brakes of  various types4 ,a very simple
 and widely used arrangement is to      
terminate the tail skid in a claw       
fitting1 as ,fig4 #ii1 so that in       

alighting the tail is shoved hard down1 
bringing the skid into contact  with the
 ground4 ,the disadvantage is that      
undesirable strains may be  carried to  
the fuselage members4    ,illustration3 
,,fig4 #ii4--,tail skid with claw       
fitting4    ,another version recently   
patented is to construct small planes to
  conform to the wing curve1 and hinged 
so that by a system of wires and        
pulleys1 actuated from the pilot's seat1
 they could be adjusted to  offer a     
normal surface to the direction of      
flight4 ,the efficiency of  this        
arrangement at low speeds is not very   
great1 moreover a landing  with the wind
 renders them quite useless4 ,the best  
form of brake is  undoubtedly one acting
 direct on the main wheels1 either of   
the rim or  band type1 a good example of
 the latter being the system used on the
 #gj  h4p4 ,bristol biplane4 ,closely   
allied to the question of brakes is that
  of steering1 and the requirements of  
this latter item are fairly well        

satisfied by pivoting the tail skid and 
working it in conjunction with  the     
rudder from the foot-bar or wheel4      
,housing of ,undercarriage during       
,flight4    ,numerous suggestions1      
ideas1 and patents exist1 having as     
their object  the housing of the        
undercarriage in the fuselage during    
flight1 with  a resultant reduction in  
resistance2 and excellent as the        
principle  is1 its practical application
 is difficult of achievement--at least1 
for machines of the present4 ,in flight 
the undercarriage is a useless          
encumbrance1 adding weight and head     
resistance1 so that an arrangement      
whereby this component could be folded  
into the main structure would           
apparently effect a saving in           
resistance4 ,this would mean that the   
fuselage would be of larger             
cross-sectional area1 the natural       
sequence  being extra weight and        
resistance4 ,it does not appear that the
 saving  effected in resistance1 when   

the undercarriage is folded during      
flight1  would account for the          
additional weight of the operating      
mechanism and  the increased head       
resistance of the fuselage1 so that     
altogether the  advantages of any       
so-called disappearing landing gear are 
very much  more apparent than real4     
,there is also the very great           
possibility of  the undercarriage       
folding up or disappearing when it would
 be least  required to do so4 ,in the   
construction of the problematic         
air-liners of  the future it may be     
possible to economically effect the     
housing of the  undercarriage4          
,,chapter ,,xii4    ,,control ,,systems4
      ,the mechanism by which the       
aeroplane is controlled in flight forms 
the connecting link between the pilot   
and machine1 and constitutes  a vitally 
important and somewhat vulnerable item  
of the complete  structure4      ,main  
,principles4    ,the control of all     
modern aeroplanes is effected in a      

lateral direction  by small planes      
hinged to the rear spar of the outer    
ends of the  wings1 and known as        
8ailerons02 in a longitudinal or        
8fore-and-aft0  direction by the        
elevator planes2 and for steering by the
 rudder4  ,although these functions are 
alluded to separately1 they are more    
often than not combined in their        
actions4 ,the correct proportion of  the
 controlling surfaces is an important   
factor in determining the  ease or      
otherwise with which a machine can be   
handled in flight1  and faults in this  
direction are responsible for the terms 
8heavy0  or 8stiff0 on the controls     
being applied to a machine4 ,the use of 
subsidiary flaps or ailerons for lateral
 control is a comparatively  modern     
innovation4 ,at one time it was usual to
 warp the entire plane1  or in some     
cases the outer section only1 and       
although the principle  is the          
same--that of forming a negative or     
positive surface to the  line of        

flight--structural considerations are   
wholly in favour of  ailerons4 ,with    
warping1 the whole plane is subjected to
 continuous  torsional movement1 and to 
obtain this some of the trussing wires  
have  necessarily to be arranged as     
control wires1 the result being that the
  plane curvature loses its uniformity1 
and the whole girder system  of the     
planes is less efficient under load than
 if the wires were  permanently fixed2  
and the latter item is only possible    
with aileron  control4 ,although it is  
usual to attach ailerons to both top and
 bottom  planes of a biplane1 there are 
occasions when sufficient control can be
  obtained with ailerons to the upper   
plane only1 usually when the span  of   
this plane is greater than that of the  
bottom4      ,control by ,inherent      
,stability4    ,with machines of the    
inherent stability class the lateral    
control  is effected by additional      
means1 the planes being designed to     
automatically right the effects of      

gusts4 ,this element of inherent        
stability is obtained by suitably       
grading the camber and incidence of  the
 wings1 until at the wing tips the chord
 of the plane section forms  a negative 
angle to the line of flight4 ,although  
this arrangement is  undoubtedly of     
value1 especially for the touring       
machine of moderate  power1 its chief   
fault lies in the relatively slow       
righting movements1  which1 although of 
no great consequence at a reasonable    
altitude1  becomes a source of danger   
when alighting1 and certainly entail the
 use  of ailerons1 or warp1 to          
counteract it4 ,the type was well       
exemplified  in this country by the     
,handley-,page monoplane and biplane1   
while in  ,germany it achieved great    
popularity1 surviving in some makes     
until  the latter part of #aiaf4 ,in the
 matter of control-surface design it is 
interesting to note the contrast between
 the preferences of ,english  and       
,german designers4 ,in almost all       

,german machines the ailerons1          
elevators1 and rudder are balanced1 i4e4
 surface is disposed each  side of the  
hinge-axis1 this applying to the small  
,albatross scouts  and to the large     
machines of the ,gotha class2 while in  
this country  few examples of this      
practice occur4 ,the reason for the     
balancing of  controls lies in the      
desire to reduce the manual strain on   
the pilot to  a minimum2 and it appears 
that with large machines balanced       
surfaces  will be imperative4 ,several  
automatic controls have been produced1  
the most notable perhaps being the      
,sperry gyroscopic1 this being a        
combination of servo-motor and          
gyroscope4 ,this apparatus has been well
  tried4    ,so far as the arrangement  
of the control surfaces is concerned1   
little  variation occurs1 which         
condition has obtained from the early   
days of  aviation1 but the mechanism    
governing or directing these movements  
varied at one time considerably1 and    

although in this country one type  of   
control is used1 there are still        
instances of the use of widely          
different systems4 ,in former days the  
practice of individual makers  fitting  
different controls resulted in some     
arrangements being in exact             
contradistinction to others1 which not  
infrequently meant1 to a pilot  taking  
on a new type1 the unlearning of a great
 deal which practice had  rendered      
instinctive4      ,the ,instinctive     
,principle4    ,all modern controls are 
based on the instinctive principle1 i4e4
  the movements of the control lever    
coincide in direction with the          
promptings of natural instinct4 ,thus1  
to change the course of a  machine      
flying level into an upward one1 the    
column is pulled towards  the pilot1 and
 for descent1 the reverse1 while to     
correct a bank1  the column is moved in 
a direction opposed to that of the bank4
 ,for  steering1 a foot-bar is employed1
 so arranged that for a turn to the     

left the left foot is pushed forward1   
and the reverse for a right turn4  ,on  
one well known machine of former days1  
the foot-bar actuated the  lateral      
control1 which is sufficient indication 
of the great diversity  of opinion then 
existing4      ,vertical ,column        
,control4    ,illustration3 ,,fig4      
#ajj4--;,arrangement of vertical column 
control4    ,a typical control of the   
immensely popular 8joy-stick0 type is   
shown  by ,fig4 #ajj4 ,this consists of 
a vertical column pivoted through the   
medium of a fork-joint to a rocking     
shaft4 ,the elevator wires are  taken   
round pulleys mounted under the seat1   
and the aileron wires  from a form of   
bell-crank1 flanged and welded to the   
steel tube4 ,a  disadvantage with this  
system1 in addition to the complication 
of the  wires1 is that lateral movement 
also affects the elevator1 although  the
 extent of this is of no great moment4  
,it is obvious1 although  somewhat      
paradoxical1 that if the elevator is to 

be depressed by a  forward movement of  
the column1 the control wires will      
required to  be crossed1 i4e4 the wire  
running from the base of the tube to the
  pulleys will be attached to the arm on
 the top side of the elevator1  and vice
 vers4 ,on single-seater machines it is 
sometimes necessary  for the pilot to   
have both hands free of the controls1 so
 that it  becomes necessary to install  
some form of locking device for the     
elevator control1 there being many      
simple ways of accomplishing this4  ,the
 locking of the control lever fixes the 
flight path of the machine1  but1 of    
course1 lateral equilibrium can be      
maintained by movements of  the lever   
sideways1 and steering by the rudder    
bar4 ,the ,german machines  of the      
,fokker and ,albatross types are both   
fitted with the single lever  control   
with a locking arrangement4 ,another    
method which achieves the  same purpose 
consists of bracing the lever in a      
normal flying position1  with rubber    

cable or coil springs anchored to       
various parts of the  fuselage1 and     
although this permits of movement1 the  
control column  always tends to return  
to the normal position4      ,wheel     
,controls4    ,illustration3 ,,fig4     
#aja4--;,arrangement of wheel control4  
,while the 8joy-stick0 type of control  
is greatly in favour1 there are  various
 forms of wheel control in use4         
,american machines are almost  entirely 
fitted with wheel controls1 and all     
things considered1 it  appears that     
modern practice is evenly divided       
between the two types4  ,the sequence of
 movements of the wheel type may be     
varied in a number  of ways1 the general
 arrangement shown by ,fig4 #aja being  
typical of an  average system4 ,in this 
case the hand-wheel is mounted on a     
central  column1 which in turn is       
rigidly fixed by some form of ,tee joint
 to  a transverse rocking shaft4 ,a     
sprocket attached to the wheel centre   
engages with a short length of chain1   

which connects to the aileron  control1 
while the elevator wires are connected  
to short tillers1  arranged to work on  
the outer side of the fuselage4 ,with   
this system  the hand-wheel is rotated  
for the aileron movements1 a            
fore-and-aft  rocking motion for the    
elevation1 and the rudder is actuated by
 an  outward movement1 with either foot 
on the rudder bar4 ,a development       
designated 8three in one0 embodies all  
these movements in the wheel  column1   
which in this case is pivoted at its    
base3 a to-and-fro motion  in the column
 for the elevators1 sideways for the    
ailerons1 while the  rudder control is  
effected by the rotation of the wheel4  
,this system is  fitted to a number of  
,american machines1 but it is a moot    
point whether  the rotation of the wheel
 for warping or steering is quite such  
an  instinctive action1 as the sideways 
movement of the lever combined with  the
 movements of the foot on the           
rudder-bar2 in any case1 there is just  

a suspicion of complication in its      
working which is undesirable1 that  is1 
for machines intended for popular use4  
,the 8,dep0 ,control4    ,illustration3 
,,fig4 #ajb4--8;,dep0 type control4     
,the type of control used on the        
,deperdussin monoplanes of #aiaj and    
onwards has survived until the present  
day1 and forms a distinctive            
arrangement4 ,its chief attribute is    
that1 compared with other systems1  much
 greater room and freedom is afforded   
the pilot1 which is evident  by a       
consideration of the diagrammatic       
sketch1 ,fig4 #ajb4 ,the inverted       
,u-shaped lever is composed of either   
ash1 bent to shape1 or steel1 or        
duralumin tube1 the general system of   
its working being the same as the  wheel
 control shown by ,fig4 #aja4           
,incidentally1 passing reference may  be
 made to the fact that the usual close  
proximity of the compass to  the        
controls precludes the use of steel in  
any great quantity for the  construction

 of the lever1 as the various movements 
adversely affect  the compass readings4 
,the ,wright ,system4    ,another       
variant of the wheel control is         
instanced by the ,wright system1  this  
consisting of a general lay out similar 
to that shown by ,fig4  #aja1 but no    
rudder-bar is fitted4 ,the rudder       
control is provided by a  small lever1  
mounted concentric with the wheel1 the  
latter carrying  a rigidly attached     
sprocket4 ,the hand-lever is also       
connected to a  sprocket1 this running  
free on the wheel shaft1 so that by     
gripping  both hand-lever and wheel it  
is possible to operate the ailerons and 
rudder simultaneously1 this action being
 a characteristic feature of  all the   
,wright productions4 ,although there are
 many types of control  in use1 those   
described in the foregoing chapter are  
illustrative of  general practice4      
,,chapter ,,xiii4    ,,wires ,,and      
,,connections4      ,in all aeroplanes  
the question of wires and the terminal  

connections  associated therewith is a  
matter of some importance1 and while    
this may  vary in degree1 there is      
little doubt that the efficiency of     
modern  wiring systems is largely       
responsible for the structural          
efficiency of  the aeroplane as a whole4
    ,aeroplane construction consists    
almost exclusively of a framework of    
wood braced by wires1 a condition of    
things which has obtained since  the    
inception of flight2 as may be judged by
 the various engravings  of ,henson's   
projected monoplane of #ahdb4 ,this     
machine incorporated  an arrangement of 
king-posts and wires approximating very 
closely to  modern practice1 and the    
natural sequence of improvements have   
tended  towards the gradual elimination 
of exposed wiring4      ,various ,wires 
used4    ,the various wires used in     
construction may be classified into four
  distinct types3 the solid wire stay1  
the straining cord or cable used  for   
stay wires1 the extra flexible cable    

used for controls1 and the  swaged tie  
rods in plain or streamline form4 ,the  
earliest form of  bracing was of the    
solid piano wire variety1 this having   
been used  on most aeroplanes from the  
days of the ,wrights onward4 ,from the  
view-point of the early pioneers1 this  
wire was eminently satisfactory1  being 
cheap 7a vital consideration7 and simple
 to attach and replace4  ,although the  
tensile strength of this wire cannot    
probably be excelled1  its hardness     
renders somewhat difficult the forming  
of the end loop  without fracture of the
 wire4 ,for this reason piano wire      
gradually  gave place to a softer grade 
of wire which1 while being strong1 was  
tough and ductile1 enabling bends to be 
made with a lesser danger of  fracture4 
,the original connection used for the   
piano wire stay is shown  by ,fig4 #ajc1
 this consisting of a loop or eye1 the  
free end being  turned round a ferrule  
of soft copper tube1 this being         
sometimes varied  by the use of a flat  

strip of tinned iron1 wrapped round and 
soldered4  ,while this was fairly       
satisfactory for short stays1 it was    
hardly  suitable for the main lift wires
 of the interplane bracing1 owing to    
the comparative ease with which1 under  
load1 the free end pulled or  cut       
through the ferrule1 so that after a    
while the oval spring-wire  ferrule1    
,fig4 #ajd1 came into use4 ,this is made
 of the same gauge wire  as the stay1   
and is from seven to nine convolutions  
in length4 ,the eye  should be formed as
 an easy bend1 and not kinked1 the      
ferrule being  pushed tight against the 
shoulders1 and the free end turned back4
      ,result of ,tests4    ,tests      
undertaken at the instance of the       
,american ,advisory ,committee  for     
,aeronautics showed that #hj per cent4  
of the wires tested failed by  the free 
end pulling through the ferrule1 the    
remaining #bj per cent4  failing by     
fracture1 the stays possessing an       
average efficiency of  #fh per cent4 of 

the maximum strength of the wire4       
,although various  modifications1 such  
as tying the free end to the ferrule    
with fine  wire1 as in ,fig4 #aje1      
resulted in an increase in total        
efficiency1  average ,european practice 
consists of that shown by ,fig4 #ajd4   
,at the  present time the solid wire    
stay of the form dealt with is used     
mainly  for the bracing of the fuselage 
frame1 and the internal wiring of the   
tail planes4      ,stranded ,cable4     
,the gradual increase in engine power   
and total weight of aeroplanes led  to  
the adoption of stranded cable for all  
important loaded wires1 this  being made
 in two distinct ways4    ,the cable    
employed for interplane bracing is      
composed of a number of  fine wires1    
varying from nineteen to thirty-seven   
according to the  different diameters1  
the end section being indicated by ,fig4
 #ajf4    ,illustration3 ,,figs4        
#ajc-aab4--,methods of forming wire     
connections4    ,where extra flexibility

 is required1 such as for control wires 
running  round pulleys1 the cable is    
composed of a number of strands1        
generally  seven1 which in turn consists
 of a number of fine wires1 usually     
nineteen1 the end section being shown by
 ,fig4 #ajg4 ,english practice          
designates this form of cable as extra  
flexible1 and the single rope  of       
nineteen wires as straining cord4       
,american classification is  practically
 the reverse1 in that the single rope is
 known as stranded  cable1 and the      
multi-strand as cord4 ,although the     
factor of strength  is an important one 
it does not entirely govern the         
selection of a  wire1 as other          
considerations1 such as flexibility and 
fatigue strain1  influence greatly the  
efficiency of a stay under active       
service  conditions4 ,under test the    
solid wire possesses the greatest       
ultimate  breaking weight1 the next best
 being the single rope4 ,it must be     
understood that in flight a wire is     

subjected to constant and intensive     
vibration1 which must have a deleterious
 effect on the material1 and  for this  
reason a flaw or slight fracture in a   
solid wire may escape  notice until     
complete failure in the air2 whereas the
 cable1 by the  unstranding of the      
damaged wires1 would give warning of    
wear4 ,chiefly  owing to the difficulty 
of forming a satisfactory splice in the 
single-strand cable1 modern practice    
inclines toward the use of the          
multi-strand cable for all purposes1 as 
the construction of this wire  lends    
itself to the forming of a successful   
splice4      ,cable ,connections4       
,the earliest form of terminal          
connection for stranded cable consisted 
of a loop1 the free end being bound to  
the main part of the wire and  soldered4
 ,with the addition of a binding or     
serving of wire round the  loop to      
prevent injury1 due to contact with the 
wiring lug1 or strainer  eye1 this wire1
 in a recent test1 gave an efficiency of

 #ajj per cent4  for all diameters up to
  in4    ,this result1 considering the  
elementary nature of the joint1 is      
surprising4 ,unfortunately the effect of
 corrosion due to acid and  solder is a 
somewhat doubtful quantity2 moreover1   
the appearance of  the joint is far from
 neat4 ,an attachment which at one time 
achieved  some popularity is shown by   
,fig4 #ajh1 and is especially suitable  
for  the single-strand wire4 ,this      
consists of a cone-shaped forked end    
with  a taper hole1 into which the cable
 is inserted1 the free end being        
unstranded1 spread out and soldered4    
,the attachment has been used on  what  
was at one time one of our best         
products4 ,the efficiency obtained  with
 this fitting is in the neighbourhood of
 #ajj per cent4    ,in the method       
indicated by ,fig4 #aji a piece of flat 
copper tube is  passed over the wire1   
the free end of the latter being bent   
round a  brass thimble1 and then passed 
through the copper tube1 in a similar   

manner to the connection for the solid  
wire in ,fig4 #ajb4 ,the tube is  then  
given several turns1 and the complete   
joint well soldered4 ,this  system is   
reliable1 and has given good results4   
,a distinctive terminal is indicated by 
,fig4 #aaj1 consisting of a brass       
ferrule just sufficiently wide to       
accommodate the two thicknesses of      
wire4 ,the bolts are of the counter-sunk
 head variety1 so that the  operation of
 screwing a bolt home also forces the   
wires into the  protuberances in the    
sides of the ferrule4 ,although the     
foregoing  methods have all been        
extensively used1 they have now given   
place to  the thimble splice1 ,fig4     
#aaa1 which1 as a general proposition1  
is  undoubtedly the better terminal     
connection4 ,the brass thimble protects 
the strands from the wearing effect     
produced by contact with the  turnbuckle
 or wiring lug4 ,it is the usual        
practice to wrap the splice  with a     
binding or serving of fine copper wire1 

or waxed twine4 ,the  efficiency of this
 joint with a properly made splice may  
be safely  taken as #he per cent4 of the
 total strength of the wire4 ,with this 
joint the point of failure1 as evidenced
 by numerous tests1 always  occurs at1  
or near1 the last tuck in the splice1 at
 which point the  extra thickness of the
 splice is just merging into the normal 
thickness  of the wire4 ,the            
disadvantage with all terminal          
connections which  necessitate the use  
of solder is the impossibility of       
determining just  how much the heating  
operation affects the strength of the   
wire1 and  also the effects of          
corrosion1 set up by the various species
 of flux  used in the process of        
soldering4      ,relative ,strengths4   
,for a given diameter the solid-wire    
stay possesses the greatest  strength1  
the next best being the single-stranded 
cable1 as the  following comparison of  
stay strength1 taken from the ,report of
 the  ,national ,advisory ,committee for

 ,aeronautics1 #aiae1 of ,america1 will 
show3--                                 
----------------------------------------
-------------         ,material4        
,diameter4  ,strength of  ,strength     
material4   of stay4                    
----------------------------------------
-------------                           
inch4        lbs4        lbs4    ,wire1 
solid            #c_/af         #eejj   
#eajj    ,strand1 single         #c_/af 
#dfjj        #dajj    #g  #ai           
multi-strand    #c_/af         #dbjj    
#cejj                                   
----------------------------------------
-------------      ,streamline ,wires4  
,although in the quest for increased    
speed the number of exposed wires  were 
reduced to a minimum1 the aggregate     
resistance still remained  considerable1
 this leading to the development of the 
swaged streamline  wire1 the            
introduction of which is generally      
ascribed to the ,royal  ,aircraft       
,factory2 and these wires are now       

generally used for all  exposed wiring4 
,the points in favour of them are that1 
properly fitted1  a considerable        
reduction in resistance is obtained1    
there is a lessened  liability to       
slacken after some use1 this rendering  
rigging a more  certain operation1 and  
the nature of its connection obviates   
the use of  turnbuckles4                
,illustration3 ,,figs4                  
#aac-aaf4--,methods of forming wire     
connections4    ,they have been         
variously criticized as being expensive 
to produce1 that  the resistance may be 
increased if improperly aligned in the  
machine1  and also that any fracture or 
flaw is less liable to be detected      
before  complete failure during flight4 
,in manufacture the solid rod is rolled 
to the section shown by ,fig4 #aab1 a   
certain length each end being left  for 
the right- and left-hand thread4 ,two of
 the connections mostly used  are shown 
by ,figs4 #aac and #aad1 the latter     
being preferable1 as the  universal     

joint permits of movement in two        
directions1 which reduces  the tendency 
of the wire to crystallize as a result  
of excessive  vibration4 ,to prevent    
wear at the points of intersection it is
 usual to  fit acorns of fibre or       
aluminium1 a popular form being shown by
 ,fig4  #aae4 ,some designers still     
prefer to use the wire cable for        
interplane  bracing1 a fairing of wood  
being bound to the cables by tape at    
intervals1 this also preventing         
excessive vibration4    ,some years ago 
various attempts were made1 mostly on   
,french monoplanes1  to utilize flat    
steel ribbon for exposed wiring1 but1   
owing to the  difficulty of successfully
 forming a terminal1 its use never      
became  extensive1 although it may      
possibly be regarded as the precursor of
 the  modern streamline wire4    ,it is 
notable that1 so far1 the wiring of all 
,german aeroplanes is  effected by      
cable1 so that apparently the merits of 
the streamline wire  are not recognized4

 ,it is also surprising that no attempt 
has been made  to streamline the cable4 
,a device for tying the wires and       
preventing  friction at the point of    
intersection1 found on nearly all enemy 
aeroplanes1 is indicated by ,fig4 #aaf1 
and there are also instances of  quick  
release devices1 these being popular in 
this country about #aiab1  and now      
obsolete4    ,although determined       
attempts have been made of late to      
entirely  eliminate exposed wiring1     
examples of this occurring in the recent
  ,german ,fokker triplane1 it appears  
that the various alterations  engendered
 by this procedure in the structure of  
the machine more than  counteract the   
saving in head resistance4    ,moreover1
 with modern methods of construction the
 ultimate strength of  a wireless wing  
structure leaves considerable room for  
improvement1 and  the price paid for the
 saving is too great4    ,the arrival of
 the all-steel aeroplane would entirely 
alter the  condition of things1 as with 

this construction much better chances   
exist for the production of a reasonably
 strong wing structure without  exposed 
wing bracing4          ,,chapter ,,xiv4 
,,engine ,,mountings4      ,the mounting
 of the engine and the general          
arrangement constitute  one of the most 
important and interesting sections of   
aeroplane  construction1 and perhaps a  
brief outline of the various engines in 
use will suitably preface a             
consideration of the mountings of the   
different types4 ,although there are    
signs that certain revolutionary        
engines may eventually come into use1   
the types in use on modern  aircraft are
 the stationary air and water-cooled1   
the radial air and  water-cooled1 and   
the air-cooled rotary4 ,the greater     
variety occurs  with the stationary type
 of engine1 which may be sub-divided    
into those  in which the cylinders are  
arranged vertically in line1 and those  
where  the cylinders viewed from the    
front form a ,v4 ,engines typical of    

the former class are the ,beardmore1    
,green1 ,mercedes1 and ,benz1 all of    
which are water-cooled2 and of the      
latter class1 ,rolls-,royce1 ,sunbeam1  
,hispano-,suiza water-cooled1 and the   
,renault and ,r4,a4,f4 air-cooled4 ,the 
types of radial engines which have been 
extensively used are confined  to two1  
these being the air-cooled ,anzani and  
the water-cooled ,salmson4  ,there is   
another radial engine of comparatively  
recent production2 but  mention of this 
while present conditions obtain is not  
permissible4  ,rotary engines of note   
are the ,gnome1 ,le ,rhone1 and         
,clerget1 all of  which are necessarily 
air-cooled4      ,essential             
,requirements of an ,engine ,mounting4  
,the essential features of any mounting 
are absolute rigidity1  accessibility to
 permit ease of erection and            
dismounting2 and it  should also be of a
 moderately low weight4 ,moreover1 the  
general  arrangement must offer a       
minimum of head resistance1 although in 

this  direction the type of engine used 
is a determining factor4 ,rigidity is  a
 paramount consideration1 for the       
slightest tendency to slackness or      
8play10 under the effect of engine      
vibration1 speedily develops1 until     
either serious stresses are induced in  
the fore part of the fuselage or  the   
engine loses its correct alignment1 with
 a consequent detrimental  effect on the
 flying qualities of the aeroplane4     
,this1 of course1  should be provided   
against in the general design2 but it is
 also a  contingency which should be    
kept in mind during the actual          
construction  of the various components 
of the complete mounting4    ,a detail  
which does not always receive sufficient
 attention is the  provision of adequate
 bracing against the thrust of the      
engine4 ,where  the construction is such
 that the engine-bearers form an        
integral part  of the fuselage          
structure1 there is generally little    
fault to find1 but  with some sheet     

steel mountings1 particularly those     
employed for the  rotary type of engine1
 the only bracing in a fore-and-aft     
direction  is that provided by the      
flanged edges of the plate1 which are   
usually  much too narrow to be of real  
use4 ,further1 the construction of both 
the engine mounting and the fore part of
 the fuselage should be of the          
necessary strength to ensure that the   
bearers supporting the engine  are      
always correctly in alignment and dead  
level4 ,with some methods  of           
construction the weight of the engine   
and various landing shocks1  result     
after a time in the lowering of the     
bearers at the front1 which  means that 
the angle of thrust is not in its       
correct position relative  to the centre
 of gravity and the incidence of the    
wings1 this being  extremely detrimental
 to the flying properties of the        
machine4      ,materials4    ,wood1 on  
account of its property of absorbing    
vibration1 is  particularly well suited 

for the construction of the engine      
mounting1  and one finds examples of its
 use in a variety of ways4 ,perhaps  the
 most common form is that in which a    
bearer of ash or spruce1  channelled out
 between the fastening-down bolt holes  
for lightness1  is attached to steel    
brackets which in turn are bolted to the
 various  fuselage members4 ,a          
development of this method consists of  
mounting  the bearers on either         
multi-ply formers of wood1 or built-up  
wood  brackets stiffened with a         
three-ply covering on each side1 and    
both  of these arrangements are being   
extensively used4 ,sheet steel is used  
for the mountings of various machines1  
but it does not possess the             
characteristic of absorbing vibration4  
,in some instances one finds that  the  
engine has been specifically designed to
 be supported on bearers  of the tubular
 variety1 in either steel or duralumin2 
but here again  rigidity is difficult of
 attainment4 ,although the use of       

welding1  that is to any extent1 is not 
advisable in the construction of the    
engine mounting1 one finds this process 
very extensively used for the  mountings
 of some modern machines4 ,in one       
particular instance1 the  tubular       
bearers are supported from the steel    
tube fuselage by various  tubes1 the    
whole structure being welded1 and       
although every joint  successfully      
survived a smash which resulted in a    
considerable bending  and distortion of 
the fuselage1 its use does not engender 
a sense of  security or reliability4    
,rotary ,engine ,mountings4             
,illustration3 ,,fig4 #aag4--,rotary    
engine mounting1 in which engine is     
supported between two plates4    ,the   
mountings associated with the rotary    
type of engine fall under two           
categories3 those where the motor is    
supported between two or more  plates1  
and those in which the motor itself is  
overhung4 ,the method  of mounting      
adopted for the first case is generally 

the type shown  by ,fig4 #aag4 ,the     
plates are pressed or bent up from sheet
 steel1 and  all edges flanged to       
prevent buckling4 ,the front plate      
embodies a ball  race1 through which the
 propeller shaft runs1 while to the rear
 bearer  is bolted the back plate of the
 engine4 ,this arrangement with minor   
variations has been extensively used for
 the different makes of small  scouting 
biplanes engined with the #hj h4p4 and  
#ajj h4p4 ,gnome motors4    ,where the  
weight of the rotary engine used is     
excessive1 as in the case  of the #afj  
h4p4 ,gnome with #bj cylinders1 which is
 now out of date1 a  mounting           
incorporating three bearers is used4    
,the arrangement would be  similar to   
that indicated by ,fig4 #aag1 with the  
addition of an extra  bearer for the    
support of the crank-shaft extension4   
,overhung ,mounting4    ,illustration3  
,,fig4 #aah4--,overhung rotary engine   
mounting4    ,the overhung type of      
engine mounting which is used for both  

propeller  and tractor aeroplanes1 is   
shown by ,fig4 #aah4 ,in this case the  
back  plate of the motor is bolted to   
the capping plate1 while an extension   
of the hollow crank shaft is supported  
by a smaller rear plate4  ,this system  
has been very widely used1 chiefly by   
reason of its  extreme lightness1 and   
the great facility afforded for the     
operation  of dismounting the engine2   
indeed1 it would be difficult to find   
an arrangement in which the demands of  
accessibility are so well  satisfied4   
,another form of overhung mounting1     
which has been used for  a radial       
,anzani motor1 is shown by ,fig4 #aai4  
,in this case the four  longerons of the
 fuselage are capped by a single flanged
 steel plate1  to which the engine is   
attached by long bolts through the crank
 case4  ,additional support is provided 
by light steel tube stays1 which are    
taken from various points on the front  
of the crank case to the centre  section
 of the upper plane1 or other parts of  

the machine4    ,illustration3 ,,fig4   
#aai4--;,anzani type engine mounting4   
,illustration3      ,,front ,,elevation 
,,side ,,elevation    ,,fig4 #abj4--;,an
 overhung mounting built up of steel    
tubes4    ,a distinctly original type of
 overhung mounting is shown by ,fig4    
#abj  in front and side elevation1 this 
being used on a machine incorporating   
an all-steel fuselage4 ,the ring to     
which the back plate of the engine  is  
bolted1 is supported from the four      
corners of the fuselage by steel        
tubing1 while the bearing for the       
crank-shaft extension is formed by  a   
pyramid of tubes welded to a pressing of
 sheet steel1 to which in  turn is      
bolted a ball-race housing4 ,at each    
corner the three converging  tubes are  
welded together1 and bolted to small    
angle plates1 which are  also welded to 
the framework of the fuselage4 ,it will 
be seen that the  strength of this      
mounting is entirely dependent upon the 
welding2 but  such reliance1 in view of 

the generally uncertain nature of this  
latter  process1 is not to be           
recommended4      ,a ,stationary ,engine
 ,mounting4    ,illustration3 ,,fig4    
#aba4--,stationary engine mounting4     
,a mounting used for a #gj h4p4         
air-cooled ,renault1 which is designed  
to  be supported by short lengths of    
steel tube projecting from the crank    
case1 is shown by ,fig4 #aba1 this      
particular arrangement being used on a  
propeller biplane4 ,the four ash        
longerons of the nacelle are built up   
in the form of a box girder1 the struts 
immediately under the engine  bearers   
being reinforced with steel plates4 ,the
 steel tubes from the  crank case       
embedded in a steel bearing1 composed of
 two semi-circular  clips1 which are let
 into the upper longerons1 and are      
prevented from  moving sideways by steel
 collars sweated to the tubes and       
abutting  against the fixing clips4 ,in 
this case1 by the removal of the four   
fixing clips and the necessary pipe     

connections1 the engine can be  lifted  
bodily out4      ,multi-,engine         
,mountings4    ,several versions of the 
type of machine employing two or more   
engines1  and which1 by the way1 is     
regarded as being the type most suitable
  for the commercial purposes of the    
future1 are existent4 ,the usual        
arrangement with the twin-engined       
machine is to support the engines       
between the planes on either side of the
 body1 the bearers being  mounted on a  
structure of struts1 which also serve as
 interplane  supports4    ,with regard  
to the flying-boat type of machine1 a   
favourite practice  is to mount the     
motor on the four struts supporting the 
centre section  of the upper plane1     
which is braced by struts and wires from
 different  points on the hull or body4 
,although the modern aircraft engine is 
of greatly increased power1  compared   
with the engine of the period           
#aiab-aiad1 one does not find any  great
 difference in the structural features  

of the mounting employed1  and in view  
of the very diverse arrangements for    
mounting the same type  of engine which 
now exist1 there is need for greater    
uniformity4 ,with  regard to the        
materials employed1 there is a very     
pronounced trend  towards the greater   
use of wood1 which circumstance is      
certainly at  variance with the         
oft-portended approaching era of steel4 
,as indicated  in previous chapters1    
wood possesses remarkable powers of     
resistance to  sudden shock1 which1     
combined with its quality of absorbing  
vibration1  renders it peculiarly       
suitable for the structure of the       
aeroplane1  and despite its numerous    
defects1 will undoubtedly continue in   
use  until either the available supplies
 of suitable timber are exhausted1  or  
until the production of a remarkably    
light alloy possessing high  strength   
values4          ,,chapter ,,xv4        
,,erection ,,and ,,alignment4      ,the 
accurate erection and alignment or      

truing up of the aeroplane1 is  a cogent
 factor in ensuring that the best       
performance is obtained1  and it is     
almost platitudinous to emphasize the   
fact that a machine  incorrectly aligned
 gives inferior results in flight1      
entails greater  attention on the part  
of the pilot1 and may possibly seriously
  interfere with the general stability  
of the aeroplane4 ,the degree of        
precision attained in the manufacture of
 the various components is  reflected in
 the ease or otherwise with which the   
complete assembly  is aligned2 indeed1  
accuracy of erection is impossible      
without the  close observance of limits 
and general trueness in the production  
of  the different parts4 ,for this      
reason the erection of the principal    
components is surveyed as a necessary   
preliminary to a consideration of  their
 assembly in the complete structure4    
,accurate ,part ,production4    ,in the 
production of the various struts1       
longerons and fittings of  the fuselage1

 the wing spars1 compression and        
interplane struts of  the planes1 the   
utmost accuracy must be observed4       
,although tolerances  are permissible   
with regard to the overall dimensions of
 the struts1  spars1 longerons1 etc41   
the lengths particularly of the fuselage
  struts should be absolutely correct to
 drawing4 ,the bad effects of a  strut1 
say #a millimetre short1 are not        
restricted to the particular  component 
of which it forms a part1 but are       
noticeable in one way or  another in the
 complete structure4 ,similarly the ends
 of struts which  are required to be    
square should be dead square1 and those 
which are  cut to a bevel should        
correspond with the correct angle4 ,the 
result of  the slightest discrepancy in 
this respect becomes speedily apparent  
when the defective struts are assembled1
 as the tension of the bracing  wires   
will result in the strut becoming bowed 
or bent1 this being  due to the bedding 
down of the strut end in the socket or  

clip4 ,it  is also advisable to trim the
 ends in a machine after being sawn to  
something approaching the correct       
length1 and the practice of sawing  to  
dead length should not be permitted4    
,the surface of a sawn strut  end is    
formed of a number of more or less      
ragged fibres1 which in  position in the
 machine and under pressure of the      
bracing wires tend  to gradually flatten
 down1 this resulting in slack wires and
 loss of  alignment4 ,absolute accuracy 
and uniformity of part production can   
only  be obtained by the use of jigs1   
preferably of metal1 and some form of   
jig should certainly be used for cutting
 the various struts to length4          
,referring again to the necessity of the
 strut ends being of the correct  angle1
 it is surprising to note the effect of 
the smallest inaccuracy4  ,the writer   
has frequently noticed fuselage struts  
considerably out  of straight1 the grain
 of the timber being sometimes advanced 
as the  reason4 ,however1 the removal of

 the defective strut always resulted  in
 its return to a straight condition4 ,it
 should be realized that the  effect of 
an initially bent strut is a reduction  
of strength1 and as  this may prove a   
source of danger1 it is in itself       
sufficient reason  for the rigid        
observance of length limits4            
,drilling of ,bolt ,holes4    ,of equal 
importance is the drilling of the       
various bolt holes for the  attachment  
of the fittings4 ,it is not always      
advisable to drill the  holes in the    
spars and longerons before the fittings 
are applied1 but  in numerous instances 
this is possible1 and where             
interchangeability is  an important     
consideration it is imperative4 ,the    
practice of setting  out the positions  
of the various holes from a drawing and 
then drilling  with a hand brace1 is a  
procedure only justified when a small   
number  of machines of a certain type   
are to be produced1 and ought by now  to
 be obsolete4 ,under such a system no   

two spars would be exactly  the same1 as
 owing to the influence of grain in the 
wood1 the drill  or bit always tends to 
8run0 from the correct angle4 ,viewed   
from the  aspect of quantity production 
such a practice is very deficient4 ,it  
is only by the use of metal drilling    
jigs of suitable design that  anything  
approaching absolute accuracy is        
possible4 ,such jigs should  not only   
locate the hole1 but should also form a 
guide for the drill4  ,in the attachment
 of the fittings to a properly          
jig-drilled spar1 it  should not be     
necessary to again drill through1       
although this often  occurs4 ,where this
 is done1 there is a distinct           
possibility of the  brace not being held
 true1 which means that the hole becomes
 larger  than necessary and not         
infrequently oval in shape4 ,an         
additional bad  point is the            
impossibility of detecting such a fault 
after the fitting  is bolted on1 and it 
may not be realized until a noticeably  

slack  wire in the complete machine     
indicates the movement of the fitting4  
,in the foregoing1 absolute accuracy in 
the various fittings has been  assumed1 
but unfortunately in practice almost the
 reverse is true4  ,variation generally 
occurs in built- or bent-up fittings1   
and is  usually the result of jigs of   
either incorrect or bad design4 ,where  
the variation includes a hole out of    
position1 the use of this fitting  on a 
previously drilled wood part is only    
possible by the bad practice  of        
drilling through with the results       
explained above4 ,it will thus be       
realized that the uniformity and        
accuracy of component production is     
only attainable by the utmost precision 
in the manufacture of both wood  and    
metal parts4      ,locking of ,bolts4   
,throughout the complete machine it is  
necessary to lock the nuts of  the      
bolts1 to prevent their gradual         
loosening under the vibration of  the   
engine1 and different methods of        

accomplishing this are in use4          
,undoubtedly the best form of lock is by
 the use of a castellated nut  and split
 pin4 ,by this method one can readily   
ascertain whether or no  a bolt is      
locked1 while by the withdrawal of the  
split pin the bolt  may be taken out4 ,a
 disadvantage is that its use entails   
considerable  drilling1 so that a       
modification consists of fitting        
castellated nuts  to all bolts liable to
 removal for minor adjustments2 while   
elsewhere  the threaded portion of the  
bolt is left a little longer than the   
nut1  and then riveted over4 ,although  
this reduces labour1 it is a somewhat   
destructive method2 and it is also      
difficult to determine the adequacy  of 
the riveting4 ,another method consists  
of filing the bolt end flush  with the  
nut1 and then centre punching three or  
four dots in the joint  between nut and 
bolt4    ,this method is neat1 the      
removal of a bolt is easily effected1   
and the  fact that it has been used in  

the construction of some fast scouting  
biplanes is proof of its effectiveness4 
,other systems include the use of two   
nuts1 of a single nut soldered  to the  
bolt end1 and the various patent        
lock-washers1 which in this  country are
 not greatly in vogue4 ,the practice of 
re-running down the  threads of bolts to
 ensure ease in the application of the  
nut is not  to be recommended--that is1 
indiscriminately done4 ,unless the die  
is  properly adjusted there is a        
possibility of too much thread being    
taken off2 the result1 an extremely     
slack nut1 being detrimental to  general
 reliability4 ,the durability of an     
aeroplane in service is  dependent upon 
the good workmanship effected in the    
smallest and most  insignificant detail4
 ,moreover1 it should be remembered that
 the  absence of a split pin may        
eventually result in disaster4          
,truing of ,main ,planes4    ,the planes
 or sections of a machine of the        
straight-wing type1 as  distinct from a 

machine possessing arrow-shaped or      
retreating wings1  should1 when erected 
on the fuselage1 form a straight line   
from tip to  tip4 ,this feature is      
dependent upon 7#a7 the trueness of the 
planes1  and 7#b7 the alignment of the  
attachments on the fuselage1 the latter 
being considered under the fuselage     
heading4 ,to ensure that the plane  is  
quite square1 it should be checked      
previous to covering by diagonal        
measurements on the wing spars1 these   
being taken from accurate set  positions
 such as are provided by the wing-root  
attachments and the  interplane strut   
fittings4 ,should a difference in the   
diagonals exist1  this can easily be    
rectified by a slight adjustment of the 
turnbuckles  incorporated in the        
internal plane wiring4 ,as the ribs of  
the plane  are built up beforehand1 and 
checked for correct contour by pattern1 
little variation should occur in the    
camber4 ,a point where differences  may 
occur is between the front spar and the 

leading edge1 as the nose  formers are  
generally inserted during the assembling
 of the plane4 ,for  the detection of   
faults in this direction the template   
illustrated by  ,fig4 #cd in ,chapter   
,,iv4 is of great utility4      ,fabric 
,covering of ,planes4    ,the evenness  
and correct tautness of the fabric      
covering contributes  largely to the    
trueness of the plane4 ,should the      
covering be stretched  unevenly or too  
tightly1 the application of the dope    
will cause  distortion of the framework1
 which can only be obviated by          
re-covering4  ,the bad effects of this  
is more noticeable with regard to the   
ailerons1  elevators and rudder1 which1 
being of very slender construction1 are 
more liable to deformation4 ,twisted or 
warped control surfaces should  never be
 used1 as such surfaces not only offer  
increased resistance1  but also         
interfere with the balance of the       
machine in flight4      ,fuselage       
,erection4    ,as the fuselage          

constitutes the nucleus of the          
aeroplane1 accuracy of  alignment in    
this component is essential1 and the    
degree of accuracy  obtained in the     
complete erection depends largely on the
 correctness  or otherwise of the       
fuselage4 ,in different individual      
designs the  methods employed for the   
construction of the body will be found  
to vary  considerably4 ,the process of  
erection adopted in many instances is to
  assemble the sides first1 upon a table
 or bench upon which the correct        
disposition of the various parts have   
previously been set out4 ,the  wires are
 adjusted until the sides conform to the
 setting out1 which  are then packed up 
on a pair of trestles and the           
cross-struts attached4  ,it now remains 
to align the body so that it is         
perfectly symmetrical  in plan2 and this
 is accomplished by marking the centre  
of each  cross-strut1 preferably before 
insertion in the fuselage1 and then     
adjusting the plan-wires until a cord   

stretched from the stern-post to  the   
nose covers each centre line4 ,the cross
 or sectional bracing-wires  are then   
tensioned until each diagonal coincides 
absolutely in length4  ,this procedure  
answers very well for a small fuselage  
of simple  construction1 and of the     
wire-braced fabric-covered type2 but    
where  the forward portion is covered   
with ply-wood1 and the top rails of the 
body are horizontal1 viewed in side     
elevation1 it is usual to true up  on a 
bench4 ,this consists of a wooden       
structure built up of strong  sides1    
with legs at short intervals1 the whole 
being well braced4 ,the  top surface1 on
 which the body lays1 is composed of    
boards placed  wherever a plan-strut    
occurs4 ,the bench should be rigidly    
fixed to a  concrete floor1 the top     
planed until it is level both           
longitudinally  and transversely1 and a 
centre line marked on each board1 while 
these  lines1 checked with a fine steel 
wire stretched from end to end1 should  

be in exact agreement with it4 ,the     
fuselage1 having been previously        
assembled1 with the wires inserted and  
the plan struts accurately  centred1 is 
placed on it in an inverted position4   
,all wires should be  then slacked off1 
and the top1 which is now underneath1   
should be wired  until the centre on    
each strut coincides with the centres on
 the bench4  ,the side wires are then   
tensioned until the stern post is       
vertical1  or until various fixed       
points1 such as wing-spar attachments1  
are in  agreement with points marked on 
the bench and squared or lined up1  and 
also until the longerons are touching   
every board4 ,the sectional  wires are  
then tightened and adjusted so that each
 diagonal is of the  same length2 and   
this will ensure the centre lines on the
 cross-struts  connecting the bottom    
rails being plumb or vertical over the  
centre  lines of the cross-struts       
connecting the top rails4 ,where the top
 rails  of the fuselage are not parallel

 to the line of flight1 but slope down  
towards the tail1 it would be necessary1
 if the bench method is used1  to       
construct it so that the boards conform 
to the slope4 ,with the  wire-braced    
fuselage minor adjustments to the       
wing-spar attachments1  which           
predetermine the angle of incidence of  
the main planes1 can be  subsequently   
made4 ,a type of fuselage which         
precludes this operation1  and which    
demands extreme accuracy in             
construction1 is that in which  the     
bracing of the forward portion is       
effected by three-ply1 all wiring  in a 
vertical dimension being eliminated1    
this system being described  in ,chapter
 ,,viii4 and illustrated by ,fig4 #ff4  
,with this construction points such as  
the wing spar attachments are  fixed1   
and cannot be altered after the fuselage
 is built1 so that  meticulous care must
 be taken in the setting of the short   
wing spars  across the body1 or the     
fittings to which the wing roots are    

anchored4    ,where a joint occurs in   
the fuselage it is usual to build the   
tail  separate from the front portion1  
and occasionally the two sections are   
trued up independently4 ,this does not  
give such good results as when  the two 
portions1 although separately built1 are
 joined together and  trued up complete4
      ,checking of ,fuselage4    ,to    
check the fuselage for alignment it     
should be placed on a pair of  trestles1
 one underneath the forward             
undercarriage strut fixing and the      
other under a vertical strut a short    
distance from the stern post4 ,the  body
 should then be levelled up             
longitudinally by a straightedge placed 
on two short straightedges of exactly   
similar widths1 one being placed  at the
 front and the other towards the tail4  
,it should then be packed  up on the    
trestles until the top longerons are    
dead level across4 ,at  this point1 if  
the body is in correct alignment1 the   
engine-bearers  would be level both     

longitudinally and transversely1 the    
incidence  of the main spar attachments 
should be correct and the stern post    
perfectly vertical in all directions4   
,other tests should include the  placing
 of a straightedge at the nose1 and     
another placed at the points  where     
struts occur1 should1 when sighted      
across the top edges1 be 8out  of wind10
 that is in agreement4 ,a point which   
should be carefully  levelled is that   
portion of the fuselage towards the     
stern post to  which is attached the    
fixed tail plane4 ,any inaccuracy here  
will result  in the tail being twisted  
in relation to the main planes4 ,each   
fitting  or attachment should also be   
equidistant from the stern post1 and the
  effect of variation here will be      
evidenced by the tail plane being  out  
of square with the centre line of the   
fuselage4 ,where the type of  machine is
 such that the engine is supported on   
bearers of wood1 it  is usual to drill  
the holes for the accommodation of the  

holding-down  bolts to jig before the   
bearer is built in the structure4 ,in   
this case  care should be taken to      
ensure that the corresponding bolt holes
 in  each bearer are square with the    
centre line4 ,any deviation will result 
in the axis of the engine forming an    
angle with the centre line4             
,alignment of ,complete ,machine4    ,in
 this connection it will be better to   
consider the alignment of a  type of    
machine in common use3 a tractor-biplane
 in which the upper  plane is composed  
of two outer planes and a centre        
section1 and the  lower plane in two    
sections1 each abutting against the side
 of the  fuselage1 this arrangement     
being shown in front elevation by ,fig4 
#abb4  ,the first operation is the      
levelling of the fuselage transversely  
by  placing the level across the engine 
bearers1 and the attachment of  the     
centre section1 which is mounted upon   
four struts which have been  previously 
cut to dead length and tested by jig4   

,this1 considered in  front elevation1  
should be centrally placed over the     
body1 and this  is assured by           
adjustments in the wires ,a-,a#a4 ,this 
can be checked by  dropping a plumb-line
 from the centre plane spar ends and    
measuring the  distance from the line to
 the side of the body1 the distances on 
either  side should1 of course1         
coincide4 ,the next point is to brace   
the outer  sections to the correct      
dihedral4 ,one method of accomplishing  
this1  as shown by ,fig4 #abb1 is by the
 use of a dihedral board1 this being    
prepared perfectly straight on one edge1
 the other being tapered to  the desired
 angle4 ,the wires are then adjusted    
until the straightedge  is level4       
,another method is to use an ordinary   
straightedge placed  along the top      
surface of the plane1 the angle being   
measured with a  protractor or          
clinometer1 the latter instrument being 
most accurate4 ,to  check the dihedral a
 line can be stretched between points   

immediately  above the top interplane   
struts on each side and then measuring  
to the  centre section1 but it would be 
difficult to detect differences in the  
angles of each wing4 ,with regard to the
 undercarriage1 the distances  between  
lines dropped from the fuselage sides   
and the wheel centres  should coincide4 
,alignment of ,machine in ,side         
,elevation4    ,considering the side    
elevation1 ,fig4 #abc1 alignment here is
 concerned  with the incidence of the   
main planes1 the distance forward of the
 top  plane from the lower plane or     
stagger1 and the level of the engine    
bearers in relation to the top longerons
 of the fuselage4    ,illustration3     
,,fig4 #abb4--,showing use of dihedral  
board and  spirit-level4    ,,fig4      
#abc4--;,checking of main-plane         
incidence and stagger4    ,,fig4        
#abd4--,template for checking incidence4
    ,the fuselage should be levelled    
longitudinally by placing the level  on 
the engine bearers1 assuming the engine 

is not in place4 ,when the  bearers are 
level1 the top longeron should also be  
level1 in any case  the incidence of the
 plane should only be adjusted in       
relation to the  engine bearers4 ,to    
check the stagger1 a plumb line should  
be dropped  from the leading edge of the
 centre plane1 and adjustments made with
  the incidence wires from the fuselage 
to the centre-plane struts1 until  the  
required distance forward from the      
leading edge of the lower plane  is     
obtained4 ,the incidence can be tested  
by a straightedge placed  under the     
plane and a clinometer1 as in ,fig4     
#abc1 and another device  sometimes used
 is shown by ,fig4 #abd4 ,this is made  
of dry wood1 the  lengths of the legs to
 the tops of the spars being obtained   
from a  drawing of the wing section1 and
 its incidence4      ,plan ,alignment of
 ,machine4    ,illustration3 ,,fig4     
#abe4--,showing points to check for     
correct alignment  on plan4    ,in the  
plan view1 ,fig4 #abe1 the distances    

,,ab and ,,ac must be equal1  the same  
applying to ,,cd and ,,bd4 ,with modern 
machines external drift  wiring is      
obsolete1 so that discrepancies in these
 measurements must  be rectified by     
alterations in the wiring of the        
fuselage1 as it is  inaccuracy at some  
point in the latter component to which  
the trouble  may be ascribed4 ,it is at 
this point that one realizes the need   
for  precision in the construction of   
the fuselage4 ,in ,fig4 #abf is shown  a
 plan view in which the main plane is   
very obviously out of square  with the  
centre line of the body1 the amount is  
not likely to occur in  actual practice1
 but it has been exaggerated in the     
drawing4 ,the cause  of this trouble can
 be traced to the short wing spars in   
the fuselage1  to which the lower plane 
is attached1 or in other cases to the   
fittings1 to which the lower plane is   
anchored1 being out of centre1  possibly
 only an insignificant amount4 ,the     
lengths of the fuselage wing  spars are 

also possible causes of trouble4        
,assuming that the rear spar  is the    
correct length1 and the front spar is   
over the length1 this  would result1    
when the outer sections were attached1  
in the latter  sloping backwards1 which 
again emphasizes the need for accurate  
part  production4    ,illustration3     
,,fig4 #abf4    ,with regard to the tail
 plane1 measurements taken from the     
extremities  of the back spar to some   
fixed point forward on the fuselage1 to 
the  strut sockets on the planes1 or to 
the rear wing spar anchorage1 as in     
,fig4 #abe1 should be equal4    ,the    
primary consideration with regard to the
 rudder and fin is that1  viewed from   
the rear1 they should be perpendicular1 
which can be  verified by a plumb-line  
dropped from the top of the rudder-post4
 ,in  plan view the fixed fin should    
correspond with the centre line of the  
fuselage although there are exceptions  
to this rule1 notably where the  fin is 
set over1 to neutralize propeller       

torque1 and in this case the            
measurements given in the general       
drawings must be adhered to4            
,tension of ,wires4    ,the correct     
tensioning of wires is a matter upon    
which some variation  of opinion occurs4
 ,although wires should not be left     
slack1 conversely  they should not be   
over-tensioned1 as this results in the  
spars1 wires1  and struts1 being        
initially stressed before any load due  
to flight is  applied4 ,in this         
connection the importance of even or    
uniform tension  in the wires may be    
emphasized4 ,the wires in one bay being 
of greater  tension than those in an    
adjacent bay1 is the frequent cause of  
bent  or deformed struts4 ,the more     
extended use of a tautness meter for the
  interplane wiring would result in     
greater uniformity and the more equal   
distribution of stresses4               
,,index4        ,aileron and warp       
control1 #aja      ,aluminium1 #af      
,anchorage of wires to eyebolts1 #ee    

,ash1 #aj      ,ash1 weight of1 #aj     
,axle fairings1 #ih        ,biplane     
trussing1 #fb      ,birch1 #ab          
,birch1 weight of1 #ab      ,brazing and
 welding1 #eb      ,bridge-type         
undercarriage suspension1 #ih           
,control systems1 #aja      ,control by 
inherent stability1 #ajb      ,control1 
vertical column1 #ajc      ,control1    
wheel type1 #ajd      ,control1 the     
8,dep10 #ajf      ,control1 the         
8,wright10 #ajg      ,control surfaces1 
balancing of1 #ajb      ,cypress1 #ac   
,drift bracing1 #fe      ,drilling of   
bolt-holes1 #abd      ,duralumin1 #ag   
,engine mountings1 #aaf      ,engine    
mountings1 rotary1 #aah      ,engine    
mountings1 overhung1 #aai      ,engine  
mountings1 stationary1 #aba      ,engine
 mounting materials1 #aag      ,erection
 and alignment1 #abc        ,fabric1    
attachment of1 #dg      ,fabric1 sagging
 of1 #dj      ,fabric1 tension of1 #dh  
,fabric1 friction blocks1 #di           
,false ribs1 #da      ,fineness ratio1  

#bf      ,fuselage construction1 #fg    
,fuselage covering1 #ga      ,fuselage  
contours1 #ge      ,fuselage erection1  
#abg      ,fuselage fittings1 #gg       
,fuselage struts1 #bh      ,fuselage    
types1 #fg        ,glue1 defects of1 in 
wing spars1 #cc        ,hickory1 #aa    
,interplane struts1 tapering of1 #bf    
,interplane strut connections1 #ea      
,leading and trailing edges1 #dc        
,lift wires1 anchorage of1 #fb          
,locking of bolts1 #abe      ,longerons1
 #fh      ,longeron sections1 #fi       
,longeron1 jointing of1 #gj             
,longeron1 shaping of1 #fi              
,mahogany1 ,honduras1 #aa               
,mahogany1 ,honduras1 weight of1 #aa    
,mahogany1 ,cuban1 weight of1 #ab       
,main planes1 truing of1 #abf      ,main
 spars1 shaping of1 #cb      ,materials1
 #f      ,maurice ,farman strut         
arrangement1 #fb      ,metal            
construction1 general1 #d      ,metal   
wing construction1 #de      ,methods of 
manufacture1 general1 #c      ,moisture 

content of timber1 #h      ,monoplane   
bracing1 #fj      ,monocoque fuselage   
construction1 #gb      ,multi-ply wood1 
#ac        ,oleo-pneumatic gear1 #ie    
,oregon pine1 #ab        ,parang1 #ac   
,piano wire bracing1 #ajh      ,piano   
wire connections1 #aji      ,plane      
construction1 #cj      ,plane           
construction1 details of1 #dj           
,planes1 arrangement of1 #cc            
,poplar1 #ab      ,pratt truss1 #ei     
,raked wing tip1 efficiency of1 #dc     
,ribs1 spacing of1 #dj      ,ribs1 types
 in use1 #cd      ,ribs under           
compression1 #cf        ,shakes1 #ad    
,shrinkage1 #g      ,silver spruce1 #h  
,silver spruce1 weight of1 #h           
,single-strut truss1 #fc      ,spar     
construction1 hollow1 #bj-bb      ,spar1
 laminated1 #ai      ,spar sections1 #ai
      ,spars and struts1 #ah            
,spruce fir1 #i      ,standardization of
 details1 general1 #b      ,steel1 #ae  
,steel tube1 #af      ,steel-tube       
fuselage construction1 #hd              

,stranded cable1 #aji                   
,stranded-cable connections1 #aaa       
,streamline wires1 #aac      ,streamline
 wires1 attachments1 #aac      ,strut   
sections1 #bc      ,strut sections1     
design of1 #bf      ,strut materials1   
#be      ,strut socket1 8,wright10 #ec  
,strut socket1 8,cody10 #ec             
,strut-socket fairings1 #eh             
,suspension springs1 steel1 #ie         
,suspension springs1 rubber1 #ig        
,tabulated tests1 unreliability of1 #h  
,three-ply fuselage construction1 #ga   
,thunder shakes1 #aa      ,timber1      
defects in1 #ad      ,trailing edge1    
wire1 #dc      ,twisted grain1 #ad      
,undercarriage brakes1 #ii              
,undercarriage details1 #ic             
,undercarriage1 principles of design1   
#hf      ,undercarriage skids1 #ic      
,undercarriage types1 #hi               
,walnut1 #aa      ,white deal1 #i       
,wing baffles1 #dd      ,wing fittings1 
attachment to spars1 #ea      ,wing-tip 
construction1 #ci      ,wing-tip        

details1 #ch      ,wing-trussing        
systems1 #ei      ,wireless wing        
structures1 #fa      ,wires and         
connections1 #ajh      ,wires1 results  
of tests on1 #aji      ,wires1 relative 
strengths of1 #aab      ,wires1 tension 
of1 #acd      ,wood1 choice of a        
suitable1 #f      ,wood1 variable       
qualities of1 #f         ,,printed ,,by 
,,william ,,clowes ,,and ,,sons1        
,,limited1 ,,london ,,and ,,beccles4    
,just ,published4 ,over #ajj pages4     
,with numerous ,diagrams4               
,fcap #hvo4 ,paper wrapper1 ,price #cs4 
#f;d4 net4                              
,the ,aircraft                          
,identification ,book                   
,a ,,concise ,,guide ,,to ,,the         
,,recognition ,,of                      
,,different ,,types ,,and ,,makes ,,of  
,,all ,,kinds                           
,,of ,,aeroplanes ,,and ,,airships      
,,by                            ,r4     
,,borlase ,,matthews     ,associate     
,member of the ,institution of ,civil   

,engineers1 ,member of the              
,institution of ,electrical ,engineers1 
,fellow of the ,royal                   
,aeronautical ,society1 ,whitworth      
,exhibitioner1                 ,author  
of the 8,aviation ,pocket-,book10 etc4  
,,and                               ,g4 
,t4 ,,clarkson      ,,extract ,,from    
,,preface    ,just as one make of motor 
car can be distinguished from another by
  noting some characteristic detail1    
such as the radiator1 the trade  mark1  
the hubs1 etc41 so can the main types of
 aeroplanes and airships  be readily    
differentiated by the recognition of the
 outstanding  features of each machine4 
,it must be admitted1 nevertheless1 that
 it  needs considerable experience to be
 able definitely to classify detail     
modifications of a particular type of   
aircraft1 for the difference is  often  
very slight4 ,besides1 the machines are 
frequently only visible  at a great     
distance1 and for but short periods     
7their speed being  so high--#fj to #aej

 miles per hour74 ,there are1 moreover1 
physical  difficulties to contend with1 
in the form of clouds1 effects of winds1
  position of the sun1 etc4    ,it is   
claimed1 however1 that this book will   
enable the reader to  identify any      
aircraft1 provided it can be seen for   
sufficient time to  observe its main    
features4                               
,,london                                
,,crosby ,,lockwood ,,and ,,son1        
#g ,,stationers' ,,hall ,,court1        
,,ludgate ,,hill1 ,e4,c4 #d1 ,,and      
#e ,,broadway1 ,,westminster1 ,s4,w4 #a 
,,list ,,of ,,books ,,on ,,aviation4    
,,the ,,aviation ,,pocket ,,book4       
,a ,compendium of ,modern ,practice and 
a collection of useful ,notes1          
,formul1 ,rules and ,tables relating to 
,aeronautics4 ,by ,r4 ,,borlase         
,,matthews1 ,wh4 ,ex41                  
,a4,m4,inst4,c4,e41 ,m4,i4,e4,e41       
,f4,r4,ae4,s41 etc4      ,assisted by   
,specialists4 ,new ,edition1 revised and
 enlarged4 ,fully      illustrated4     

,fcap #hvo4 #aiah ,edition4 ,price #fs4 
net4      ,,the ,a4,b4,c4 ,,of          
,,aviation4        ,a ,complete         
,practical ,treatise outlining clearly  
the elements of      ,aeronautical      
,engineering1 with special reference to 
simplified      explanations of the     
,theory of ,flight1 ,aerodynamics1 and  
,basic      ,principles underlying the  
,action of ,balloons and ,airplanes of  
all      types4 ,by ,captain ,,victor   
,w4 ,,pag1 of the ,u4,s4 ,air ,service4 
,demy      #hvo4 #bgd pages1 with very  
numerous illustrations and #d folding   
plates4 ,price #abs4 #f;d4 net4         
,this ,work contains valuable           
instructions for all ,aviation          
,students1 ,airplane ,mechanics1        
,squadron ,engineering ,officers1       
and every one interested in             
,construction and ,up-keep of           
,airplanes4      ,,aviation ,,engines4  
,their ,design1 ,construction1          
,operation1 and ,repair4 ,a ,book for   
the      ,student1 ,engineer1 and all   

interested in ,aviation4 ,giving        
practical      instruction on repair and
 maintenance4 ,by ,captain ,,victor ,w4 
,,pag1      of the ,u4,s4 ,air ,service4
 #ehj pages1 with over #bdj             
illustrations4      ,medium #hvo1 #afs4 
net4      ,,glossary ,,of ,,aviation    
,,terms4        ,english-,french1       
,french-,english4 ,cr4 #hvo1 #ajj pages1
 with plates and      illustrations4 ,by
 ,captain ,,victor ,w4 ,,pag and ,lieut4
 ,,paul ,,montariol4      ,price #es4   
net4      ,,aviation ,,chart4        ,a 
large ,wall ,chart1 showing a typical   
,aeroplane ,power ,plant in ,part       
,section with all important components4 
,folding to pocket size4      ,price    
#bs4 #f;d4 net4      ,,observation      
,,balloons4        ,by ,,emil ,j4       
,,widmer4 #aej pages1 with #c plates and
 #ch illustrations4      ,crown #hvo4   
#afs4 net4                              
,,crosby ,,lockwood ,,and ,,son1        
#g ,,stationers' ,,hall ,,court1 ,e4,c4 
#d4          ,transcriber's ,notes      

,punctuation1 hyphenation1 and spelling 
were made consistent when a  predominant
 preference was found in the original   
book2 otherwise they  were not changed4 
,simple typographical errors were       
corrected2 unbalanced quotation  marks  
were remedied when the change was       
obvious1 and otherwise left  unbalanced4
    ,many illustrations in this e,book  
have been left near where they          
originally appeared1 even when that was 
mid-paragraph4    ,the index was not    
checked for proper alphabetization or   
correct page  references4