design of unmanned aerial combat vehicle
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Design Of Unmanned Combat Aerial Vehicle
DESIGN OF UNMANNED COMBA AE!IA" VE#IC"E
A $!O%EC !E$O!
Submitted by
C#!ISO$#E! B#A!A#&M
D#INES# 'UMA!&U
in partial fulfillment for the award of the degree
of
BAC#E"O! OF ENGINEE!ING
in
AE!ONAUICA" ENGINEE!ING
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!A%A"A'S#MI ENGINEE!ING
CO""EGE(#ANDA"AM)*+,-+.
ANNA UNIVE!SI/00
C#ENNAI *++ +,.NOVEMBE! ,+-,
!A%A"A'S#MI ENGINEE!ING
CO""EGE
#ANDA"AM 1 *+, -+.
BONAFIDE CE!IFICAE
This is to certify that this is a bonafide record of work done by the student ,
,III year Aeronautical Engineering in the AIRCRAFT DESIG !R"#ECT $% &aboratory
during the acade'ic year ()%%$()%(.
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UNIVERSITY REGISTER No.
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Signat2re of Fac2lt3)in)Charge
S2bmitted for the $ractical E4amination held on 5555555555&&
Internal E4aminer E4ternal E4aminer
AC'NO6"EDGEMEN
*e would like to e+tend our heartfelt thanks to $rof& /ogesh '2mar Sinha for
giing us his able su--ort and encourage'ent. At this /uncture we 'ust e'-hasis
the -oint that this design -ro/ect would not hae been -ossible without the highly
infor'atie and aluable guidance of Mr& S2rendra Bogadi0Asst. !rofessor of
Aeronautical De-art'ent1, whose ast knowledge and e+-erience has greatly
hel-ed us in this -ro/ect. *e hae great -leasure in e+-ressing our sincere and
whole hearted gratitude to the'.
It is worth 'entioning about 'y friends and colleagues of the Aeronautical
de-art'ent for e+tending their kind hel- wheneer the necessity arose. I thank one
and all who hae directly or indirectly hel-ed us in 'aking this design.
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INDE7
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Serial no& Content $age no
%. Introduction
(. Data Fro' AD!$I
2. Ai' 3 "b/ectie
4. Three 5iew Diagra'
6. 5$n Diagra'
7. Gust Enelo-e
8. Schrenk9s Cure
:. &oad Esti'ation "n *ing
;.
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S/MBO"S AND NOAIONS USED
A.R. $ As-ect Ratio
= $ *ing S-an 0'1C $ Chord of the Airfoil 0'1
C $ ero &ift Drag Co$efficient
C-$ S-ecific fuel consu'-tion 0lbs?h-?hr1
C&$ &ift Co$efficient
D $ Drag 01E $ Endurance 0hr1
e $ "swald efficiency
& $ &ift 01
0&?D1 loiter $ &ift$to$drag ratio at loiter
0&?D1 cruise $ &ift$to$drag ratio at cruise
R $ Range 0k'1
Re $ Reynolds u'ber
S $ *ing Area 0'@1
Sref$ Reference surface area
Swet$ *etted surface area
Sa$ A--roach distance 0'1
Sf$ Flare Distance 0'1
Sfr$ Free roll Distance 0'1
Sg$ Ground roll Distance 0'1
Ttake$off $ Thrust at take$off 015cruise$ 5elocity at cruise 0'?s1
5stall $ 5elocity at stall 0'?s1
*e'-ty$ E'-ty weight of aircraft 0kg1
*fuel $ *eight of fuel 0kg1
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*-ayload$ !ayload of aircraft 0kg1
*) $ "erall weight of aircraft 0kg1
*?S $ *ing loading 0kg?'@1
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-&IN!ODUCION
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IN!ODUCION
The structural design of an air-lane actually begins with the flight enelo-e or 5$
n diagra', which clearly li'its the 'a+i'u' load factors that the air-lane can withstand at any-articular flight elocity. oweer in nor'al -ractice the air-lane 'ight e+-erience loads thatare 'uch higher than the design loads. So'e of the factors that lead to the structural oerload ofan air-lane are high gust elocities, sudden 'oe'ents of the controls, fatigue load in so'ecases, bird strikes or lightning strikes. So to add so'e inherent ability to withstand these rare butlarge loads, a safety factor of %.6 is -roided during the structural design.
The two 'a/or 'e'bers that need to be considered for the structural design of anair-lane are wings and the fuselage. As far as the wing design is concerned, the 'ost significantload is the bending load. So the -ri'ary load carrying 'e'ber in the wing structure is the s-ar0the front and rear s-ars1 whose cross section is an BI9 section. A-art fro' the s-ars to take thebending loads, suitable stringers need to take the shear loads acting on the wings.
nlike the wing, which is sub/ected to 'ainly unsy''etrical load, the fuselage is 'uchsi'-ler for structural analysis due to its sy''etrical crossing and sy''etrical loading. The'ain load in the case of fuselage is the shear load because the load acting on the wing istransferred to the fuselage skin in the for' of shear only. The structural design of both wing andfuselage begin with shear force and bending 'o'ent diagra's for the res-ectie 'e'bers. The'a+i'u' bending stress -roduced in each of the' is checked to be less than the yield stress ofthe 'aterial chosen for the res-ectie 'e'ber.
The Structural design inoles
Deter'ination of loads acting on aircraft
a1 5$n diagra' for the design studyb1 Gust and 'aneuerability enelo-es
c1 Schrenk9s Cure
d1 Critical loading -erfor'ance and final 5$n gra-h calculation
Deter'ination of loads acting on indiidual structures
a1 Structural design study Theory a--roach
b1 &oad esti'ation of wings
c1 &oad esti'ation of fuselage.
d1
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f1 Design of so'e co'-onents of wings, fuselage
DAA F!OM AD$)II
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Airfoil Thickness7J
Stall Angle:.6 deg
Ca'ber 6J
AIM 8 OB%ECIVE
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AIM 8 OB%ECIVE
The ob/ectie is to design the su-erior un'anned co'bat aerial ehicle and it has all kind
of wea-ons which satisfies the 'ission as well as 'ilitary reKuire'ents. This design entangles
with
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hree Vie9 Diagram
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O$ VIE6
F!ON VIE6
SIDE VIE6
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the structural 0'a+i'u' load factor1 and aerodyna'ic 0'a+i'u' C&1 boundaries for a
-articular flight condition.
This enelo-e de'onstrates the ariations of airs-eed ersus load factor 05 n1. In
another word, it de-icts the aircraft li'it load factor as a function of airs-eed. "ne of the -ri'aryreasons that this diagra' is highly i'-ortant is that, the 'a+i'u' load factorL that is e+tracted
fro' this gra-hL is a reference nu'ber in aircraft structural design. If the 'a+i'u' load factor is
under$calculated, the aircraft cannot withstand flight load safely. For this reason, it is
reco''ended to structural engineers to recalculate the 5$n diagra' on their own as a safety
factor.
!eal :al2es of load factor for se:eral aircraft
Fro' the table the li'it load factor for our CA5 ranges between
Mli'0Ne1 ;Mli'0$e1 2
First of all we need to find thea. Design
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Design
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Calc2lation Of he Negati:e C2r:e Of V)N Diagram0 Design
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0 0 0 0
25 0.65 25 -0.3253
30 0.9371 30 -0.4685
40 1.6659 40 -0.833
60 3.748 50.23 -1.31
87 7.88 175 -1.31
175 7.88 192.5 -1
192.5 6.88 192.5 6.88
The 5$n -lot is shown below, which clearly e+-lains the load factor behaior of the n'annedAerial 5ehicle
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This 5$n diagra' hel-s in -redicting the -ositie load li'it, negatie load li'it, !ositieaccelerated stall, negatie accelerated stall, s-eed li'it, Caution range, Safety li'it, structuralda'age, etc.,
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@& GUS ENVE"O$E
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Gust is a sudden, brief increase in the s-eed of the wind. Generally, winds are least gusty
oer large water surfaces and 'ost gusty oer rough land and near high buildings. *ith res-ect
to aircraft turbulence, a shar- change in wind s-eed relatie to the aircraftL a sudden increase in
airs-eed due to fluctuations in the airflow, resulting in increased structural stresses u-on the
aircraft.
Shar-$edged gust 0u1 is a wind gust that results in an instantaneous change in direction or
s-eed.
Deried gust elocity 0 or 'a+1 is the 'a+i'u' elocity of a shar-$edged gust that
would -roduce a gien acceleration on a -articular air-lane flown in leel flight at the design
cruising s-eed of the aircraft and at a gien air density. As a result a (6J increase is seen in liftfor a longitudinally disturbing gust.
The effect of turbulence gust is to -roduce a short ti'e change in the effectie angle of
attack. These changes -roduce a ariation in lift and thereby load factor
For elocities u- to 5'a+, cruise, a gust elocity of %6 '?s at sea leel is assu'ed. For
5di, a gust elocity of %) '?s is assu'ed.
Effectie gust elocity The ertical co'-onent of the elocity of a shar-$edged gust that
would -roduce a gien acceleration on a -articular air-lane flown in leel flight at the design
cruising s-eed of the aircraft and at a gien air density.
Reference Gust 5elocity 0ref1at sea leel %6'?s.
Design Gust 5elocity 0ds1 ref .
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Constructon
The increase in the load factor due to the gust can be calculated by
For cure aboe 5$a+is
*here ,
Gust Alleiation Factor.
'a+
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ct Chord at ti- < m
cr Chord at root ,&-.* m ; .&*
a9 lift cure slo-e for airfoil
Swee- angle at leading Edge of *ing
a ; +&+=
Therefore we obtain,
;@=&
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=y using the eKuations and for arious s-eeds of 'a+ we get the following gust lines
Calc2lation Of he $ositi:e And Negati:e C2r:e Of G2st Diagram0
V!"oct# $o%& '%ctor V!"oct# $o%& '%ctor
0 1 0 1
25 0.3125 25 0.3125
30 0.432 30 0.175
40 0.702 40 -0.1
60 1.894 50.23 -0.38
87 5.785 175 -3.81
192.5 3.156 192.5 -0.434
The load factors at the arious -oints can be found using the for'ula using the corres-onding
alues of 'a+and the gust enelo-e is found to be,
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&SC#!EN'S CU!VE
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SchrenHs C2r:e
&ift aries along the wing s-an due to the ariation in chord length, angle of attack and swee-
along the s-an. Schrenk9s cure defines this lift distribution oer the wing s-an of an aircraft,also called si'-ly as &ift Distribution Cure. Schrenk9s Cure is gien by
*here
y%is &inear 5ariation of lift along se'i wing s-an also na'ed as &%.
y(is Elli-tic &ift Distribution along the wing s-an also na'ed as &(.
a ;.
"inear "ift Distrib2tion0
"ift at root
"root;,@
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"ift intermediate
"-;--+,
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Ellitic "ift Distrib2tion0
Twice the area under the cure or line will gie the lift which will be reKuired to
oerco'e weight
Considering an elli-tic lift distribution we get
*here
b%is Actual lift at root
a is wing se'i s-an
&ift at ti-
b-;*
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Substituting different alues for + we can get the lift distribution for the wing se'i s-an
"ift distrib2tion table along semi san
4 linear ellitic Combined
+ 24:822 7:7;.84 %88:)%.4+&. 2%77)( 7:26.2)6 %7%8%:.8
- (:448% 782).;42 %467)%
-&. (6(24) 7662.2%4 %(;447.8
, (()(); 7(;7.((% %%2(6(.7
,&. %::)8: 6;4;.27; ;8)%2.7:
@ %66;48 64;6.8;( :)8(%.4@&. %(2:%7 4;)6.;87 7427).;;
;%7:6 4%(%.:44 48;)2.4(
&. 6;664 (;;4.46 2%(84.(2
. (84(2 ) %28%%.6
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.& "OAD ESIMAION ON 6ING
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The solution 'ethods which follow Euler9s bea' bending theory 0U?y
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/,>, ; *
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Self)6eight 3@0 Self)9eight of the 9ing(
**ing ).(6W *E'-ty
).(6W2)))W;.:%
66ing; =@.=&. N
6$ort; )@*=
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';)
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3,>, (7;88.4 (.%((
6ing 27:2 %.:86
F2el 2);2.72 %.;66
!eaction force and Bending moment calc2lations
VA; +5A$;42668.6$(7;88.4N27:2N2);2.72 )
VA; ?*@=.
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Shear Force0
=y using the corres-onding alues of + in a--ro-riate eKuations we get the -lot of shear force
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% (20 1
(BC Ay ySF y dx V += +
% (20 1 0 1
(DC A fuel
y ySF y dx V y dx
+= + +
% (20 1 2);4
(AD A
y ySF y dx V
+= + +
2( ( % (74(7( 24:822 %284 (6 (6sin ::.2 6
( 6 2
;7286:.(4
BC
x xSF x x x x x
= + + + +
((().;86 %:8:.2DC BCSF SF x x= +
((().;86 %:8:.2 2);2.72AD BCSF SF x x x= + +
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Bending moment
=y substituting the alues of + for the aboe eKuations of bending 'o'ents obtained we can get
a continuous bending 'o'ent cure for the -ort wing.
Note0if we re-lace the + by $+ in each ter' we get the distribution of starboard wing
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( )( )
2 ( %
(
4%.6
( 2 (
%)8%) %84277.6 7:8 (6 (6 sin6
28.6 (6 ::.2 %.77 %(.6 ;7286:.(4 ()%)%;4.4(%(
BC
xBM x x x x x
xx x x x
= + + +
+ + +
(% (
2(
BC A A
y yBM y V dx M
+ = + +
DC BC fuelBM BM y dx= +2 ((().;86 ;2;.%6DC BCBM BM x x= +
2);4AD DCBM BM x=
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Shear force and bending moment diagrams d2e to loads along chord9isedirection at cr2ise condition0
Aerod3namic center)This is a -oint on the chord of an airfoil section where the bending
'o'ent due to the co'-onents of resultant aerodyna'ic force 0&ift and Drag1 is constant
irres-ectie of the angle of attack. ence the forces are transferred to this -oint for obtaining
constant
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Co$efficient of 'o'ent about aerodyna'ic centre $).%6
&ocation of aerodyna'ic centre
4ac>c;+&,.
&ocation of shear centre
4sc>c;+&@
&ift and drag are the co'-onents of resultant aerodyna'ic force acting nor'al to and along the
direction of relatie wind res-ectiely. As a result, co'-onents of the' act in the chordwise
direction also which -roduce a bending 'o'ent about the nor'al 0V1 a+is.5
Co$efficient of force along the nor'al direction,
Cn;C"Cos JCD Sin
Cn 0).)6 W Cos $41 N 0).)%(6 W Sin $41
Cn).)6
Cc ;C"Sin JCD Cos
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Cc 0).)6 W Sin $41 N 0).)%(6 W Cos $41
Cc ).%(%(
Chord wise force at root,
FR 0).6W).%(%(W%.((6W%86(W:1
F!; -m
Chord wise force at inter'ediate length,
F- ; m
F,; ?+-&.. NKm
=y using y '+ Nc again we get the eKuation as
3 ; ),.*.&.4 J -.,-?
The aboe eKuation gies the -rofile of load acting chordwise, by integrating this aboe eKuation
we get a co'-onent of Shear force and again by integrating the sa'e we get the co'-onent of
=ending
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To find fi+ing 'o'ent and the reaction force,
VA ; +
VA ; +@?&@, N
MA; +
MA ;
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Bending Moment0
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(
2 (4(8.6: 87);.6 4)2;4.2( :27%7.(4
A ABM ydx V x M
BM x x x
= +
= + +
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TorKue due to nor'al forces and constant -itching 'o'ent at cruise condition
The lift and drag forces -roduce a 'o'ent on the surface of cross$section of the wing, otherwise
called a torKue, about the shear center.
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or2e at cr2ise condition0
or2e d2e to normal force0
*herec chordThe eKuation for chord can also be re-resented in ter's of + by taking c '+Nk
c ; )-&-,
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or2e d2e to chord 9ise force0
or2e d2e to moment0
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(
(
W )
)
cT F
T
=
=
( (
2
( (
2
(
2
2 (
2
%
(
).%6W ).6W%.((6W%86 W
(:%2.78
(:%2.78 ).4(4 8.66 44.:(
acMT C V c
T c
T cT x x x
=
=
= = +
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Then the different torKue co'-onents are brought together in a sa'e gra-h to 'ake aco'-arison
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The net torKue will be su' of all the aboe torKues i.e. torKue due to nor'al force, chordwise
force, -ower-lant and aerodyna'ic 'o'ent
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=& MAE!IA" SE"ECION
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Aircraft Metals
nowledge and understanding of the uses, strengths,li'itations, and other characteristics ofstructural'etals is ital to -ro-erly construct and 'aintain any eKui-'ent, es-ecially airfra'es.
In aircraft 'aintenance and re-air, een a slight deiation fro' design s-ecification, or the
substitution of inferior 'aterials,'ay result in the loss of both lies and eKui-'ent. The use of
unsuitable 'aterials can readily erase the finestcrafts'anshi-. The selection of the correct
'aterial fora s-ecific re-air /ob de'ands fa'iliarity with the 'ost co''on -hysical -ro-erties
of arious 'etals.
$roerties of Metals
"f -ri'ary concern in aircraft 'aintenance are suchgeneral -ro-erties of 'etals and their alloys
as hardness,'alleability, ductility, elasticity, toughness, density, brittleness, fusibility,
conductiity contractionand e+-ansion, and so forth. These ter's are e+-lainedto establish a
basis for further discussion of structural'etals.
#ardness
ardness refers to the ability of a 'aterial to resistabrasion, -enetration, cutting action, or
-er'anentdistortion. ardness 'ay be increased by cold working the 'etal and, in the case of
steel and certain alu'inu'alloys, by heat treat'ent. Structural -arts are often
for'ed fro' 'etals in their soft state and are then heattreated to harden the' so that the finished
sha-e will beretained. ardness and strength are closely associated -ro-erties of 'etals.
Strength
"ne of the 'ost i'-ortant -ro-erties of a 'aterial isstrength. Strength is the ability of a 'aterial
to resistdefor'ation. Strength is also the ability of a 'aterial to resist stress without breaking.
The ty-e of load orstress on the 'aterial affects the strength it e+hibits.
Densit3
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Density is the weight of a unit olu'e of a 'aterial.In aircraft work, the s-ecified weight of a
'aterial -ercubic inch is -referred since this figure can be used indeter'ining the weight of a
-art before actual 'anufacture.Density is an i'-ortant consideration whenchoosing a 'aterial to
be used in the design of a -artin order to 'aintain the -ro-er weight and balance ofthe aircraft.
Malleabilit3
A 'etal which can be ha''ered, rolled, or -ressedinto arious sha-es without cracking,
breaking, orleaing so'e other detri'ental effect, is said to be'alleable. This -ro-erty is
necessary in sheet 'etalthat is worked into cured sha-es, such as cowlings,fairings, or wingti-s.
Co--er is an e+a'-le of a 'alleable'etal.
D2ctilit3
Ductility is the -ro-erty of a 'etal which -er'its it tobe -er'anently drawn, bent, or twisted
into arioussha-es without breaking. This -ro-erty is essential for'etals used in 'aking wire
and tubing. Ductile 'etalsare greatly -referred for aircraft use because of theirease of for'ing
and resistance to failure under shockloads. For this reason, alu'inu' alloys are used for
cowl rings, fuselage and wing skin, and for'ed ore+truded -arts, such as ribs, s-ars, and
bulkheads.Chro'e 'olybdenu' steel is also easily for'ed intodesired sha-es. Ductility is
si'ilar to 'alleability.
Elasticit3
Elasticity is that -ro-erty that enables a 'etal to returnto its original siVe and sha-e when the
force whichcauses the change of sha-e is re'oed. This -ro-ertyis e+tre'ely aluable because it
would be highlyundesirable to hae a -art -er'anently distorted afteran a--lied load was
re'oed. Each 'etal has a -ointknown as the elastic li'it, beyond which it cannot be
loaded without causing -er'anent distortion. In aircraftconstruction, 'e'bers and -arts are so
designed that the 'a+i'u' loads to which they are sub/ected willnot stress the' beyond their
elastic li'its. This desirable-ro-erty is -resent in s-ring steel.
o2ghness
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A 'aterial which -ossesses toughness will withstandtearing or shearing and 'ay be stretched or
otherwisedefor'ed without breaking. Toughness is a desirable-ro-erty in aircraft 'etals.
Brittleness=rittleness is the -ro-erty of a 'etal which allows littlebending or defor'ation without
shattering. A brittle'etal is a-t to break or crack without change of sha-e.=ecause structural
'etals are often sub/ected to shockloads, brittleness is not a ery desirable -ro-erty. Cast
iron, cast alu'inu', and ery hard steel are e+a'-lesof brittle 'etals.
F2sibilit3
Fusibility is the ability of a 'etal to beco'e liKuid bythe a--lication of heat.
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tail s-ars is 'uch longer than their width and de-thL the ribs hae a 'uch larger chord length
than height and?or widthL a whole wing has a s-an that is larger than its chords or thicknessL and
the fuselage is 'uch longer than it is wide or high. Een a -ro-eller has a dia'eter 'uch larger
than its blade width and thickness, etc.... For this si'-le reason, a designer chooses to use
unidirectional 'aterial when designing for an efficient strength to weight structure.
nidirectional 'aterials are basically co'-osed of thin, relatiely fle+ible, long fibers which are
ery strong in tension 0like a thread, a ro-e, a stranded steel wire cable, etc.1
An aircraft structure is also ery close to asymmetrical structure. That 'eans the u- and
down loads is al'ost eKual to each other. The tail loads 'ay be down or u- de-ending on the
-ilot raising or di--ing the nose of the aircraft by -ulling or -ushing the -itch controlL the rudder
'ay be deflected to the right as well as to the left 0side loads on the fuselage1. The gusts hitting
the wing 'ay be -ositie or negatie, giing the u- or down loads which the occu-ante+-eriences by being -ushed down in the seat ... or hanging in the belt.
=ecause of these factors, the designer has to use a 84 structural 'aterial that can
withstand both tension and co'-ression. nidirectional fibers 'ay be e+cellent in tension, but
due to their s'all cross section, they hae ery little inertia 0we will e+-lain inertia another ti'e1
and cannot take 'uch co'-ression. They will esca-e the load by bucking away. As in the
illustration, you cannot load a string, or wire, or chain in co'-ression.
In order to 'ake thin fibers strong in co'-ression, they are Zglued togetherZ with so'e
kind of an Ze'beddingZ. In this way we can take adantage of their tension strength and are no
longer -enaliVed by their indiidual co'-ression weakness because, as a whole, they beco'e
co'-ression resistant as they hel- each other to not buckle away. The e'bedding is usually a
lighter, softer ZresinZ holding the fibers together and enabling the' to take the reKuired
co'-ression loads. This is a ery good structural 'aterial.
*+*- Al2mini2m Allo3
*+*-is a -reci-itation hardening alu'iniu' alloy, containing 'agnesiu' and silicon as its
'a/or alloying ele'ents. It has good 'echanical -ro-erties and e+hibits good weldability. It is
one of the 'ost co''on alloys of alu'iniu' for general -ur-ose use.
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It is co''only aailable in -re$te'-ered grades such as, 7)7%$" 0solutioniVed1, 7)7%$T7
0solutioniVed and artificially aged1, 7)7%$T76% 0eKuialent to T7 in rolled stock1.
Basic roerties
7)7% has a density of (.8) g?c'[ 0).);86 lb?in[1.
Chemical comosition
The alloy co'-osition of 7)7% is
Silicon 'ini'u' ).4J, 'a+i'u' ).:J by weight
Iron no 'ini'u', 'a+i'u' ).8J
Co--er 'ini'u' ).%6J, 'a+i'u' ).4)J
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b *+*-)
T4 te'-er 7)7% has an ulti'ate tensile strength of at least 2),))) -si 0()8
strength of at least %7,))) -si 0%%)
c *+*-)*
T7te'-er 7)7% has an ulti'ate tensile strength of at least 4(,))) -si 0(;)
strength of at least 26,))) -si 0(4%
elongation of :J or 'oreL in thicker sections, it has elongation of %)J. T76% te'-er has si'ilar
'echanical -ro-erties. The fa'ous !ioneer -laKue was 'ade of this -articular alloy.
Uses
7)7% is widely used for construction of aircraft structures, such as wings and fuselages, 'ore
co''only in ho'ebuilt aircraft than co''ercial or 'ilitary aircraft.
7)7% is used for yacht construction, including s'all utility boats.
7)7% is co''only used in the construction of bicycle fra'es and co'-onents.
6elding
7)7% is highly weldable, for e+a'-le using tungsten inert gas welding 0TIG1 or 'etal inert gaswelding 0
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Forgings
7)7% is also an alloy that is co''only used in a hot forging. The billet is heated through an
induction furnace and forged using a closed die -rocess. Auto'otie -arts, AT5 -arts, and
industrial -arts are /ust so'e of the uses as a forging.
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Sar design0
S-ars are 'e'bers which are basically used to carry the bending and shear loads acting
on the wing during flight. There are two s-ars, one located at %6$()J of the chord known as the
front s-ar, the other located at 7)$8)J of the chord known as the rear s-ar. So'e of the
functions of the s-ar include
They for' the boundary to the fuel tank located in the wing.
The s-ar flange takes u- the bending loads whereas the web carries the shear loads.
The rear s-ar -roides a 'eans of attaching the control surfaces on the wing.
Considering these functions, the locations of the front and rear s-ar are fi+ed at ).%8c and
).76c res-ectiely. The ARA$D 7J airfoil is drawn to scale using any design software and the
chord thickness at the front and rear s-ar locations are found to be 0).:4 ' and ).7( '1, 0).28 '
and ).2)1, 0).(28 ' and ).%66 ' 1 for three sections res-ectiely.
The s-ar design for the wing root has been taken because the 'a+i'u' bending 'o'ent
and shear force are at the root. It is assu'ed that the flanges take u- all the bending and the web
takes all the shear effect. The 'a+i'u' bending 'o'ent for high angle of attack condition is
()%)%;4.4( '. the ratio in which the s-ars take u- the bending 'o'ent is gien as
*here
h% height of front s-ar
h( height of rear s-ar
FI!S SECION
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The yield tensile stress Uyfor 7)7% Al Alloy is (87
=oth the flanges are connected by a ertical stiffener through s-ot welding
Fro' the buckling eKuation,
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the thickness to width ratio of web is found to be ).%)%7. Also fro' \AA&]SIS AD
DESIG "F F&IGT 5EIC&E STRCTRES by =R^, the flange to web width ratio of
the T section .
=y eKuating all the three alues of the ratio in area of the section eKuation, the di'ensions of the
s-ar can be found.
Secification For Front Sar0
t( %.)(7%7W%)$2
t ; +&+@,+ m
bf; +&,+=? m
b9; +&@-. m
Secification For !ear Sar0
t( 8.6862W%)$4
t ; +&+,=. m
bf; +&-=< m
b9; +&,=+ m
SECOND SECION
The yield tensile stress Uyfor 7)7% Al Alloy is (87
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*here
U is yield strength0(87
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t( (.%22W%)$2
t ; +&+*, m
bf; +&@+ m
b9; +&.= m
Secification For !ear Sar0
t( %.8%8W%)$2
t ; +&+- m
bf; +&,*? m
b9; +&+=. m
#I!D SECION
The yield tensile stress Uyfor 7)7% Al Alloy is (87
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Afs; +&+*,
Area of the rear s-ar
Ars; +&+.,
Ass2mtions0
T sections are chosen for to- and botto' flanges of front and rear s-ars.
=oth the flanges are connected by a ertical stiffener through s-ot welding
Fro' the buckling eKuation,
the thickness to width ratio of web is found to be ).%)%7. Also fro' \AA&]SIS AD
DESIG "F F&IGT 5EIC&E STRCTRES by =R^, the flange to web width ratio of
the T section .
=y eKuating all the three alues of the ratio in area of the section eKuation, the di'ensions of thes-ar can be found.
Secification For Front Sar0
t( 4.%%4:W%)$2
t ; +&+*, m
bf; +&-*m
b9; +&*@- m
Secification For !ear Sar0
t( (.7:(W%)$2
t ; +&+., m
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bf; +&@@. m
b9; +&.+< m
FI!S SECION
SECOND SECION
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CONC"USION
The structural design \-art (^ of the
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BIB"IOG!A$#/
%. Ray'er, D.!, Aircraft Design ) a Concet2al Aroach (AIAA educational series second
edition %;;(.
(. T..G.
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