ADL II EXAMPLE.doc

8/14/2019 ADL II EXAMPLE.doc

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1. INTRODUCTION

AN AIRCRAFT DESIGN IS BOTH AN ART AND SCIENCE

Aircraft design project-II is the continuation of the aircraft design project-I.In the ADP-I, we have determined the design parameters such as:

Empty weight, WE

ue! weight, W

"ota! ta#e-off weight, W"$

Wing !oading, W%&

Wing area, &

'o-efficient of !ift, '(

Drag estimation

Airfoi!s

)oot chord, 'r

"ip chord, 't

"hrust-weight !oading, "%W

Power p!ant

1.1 DETAILED RESULT OF THE AIRCRAFT DESIGN LAB - I

$vera!! weight *+*/.+ !0s

ue! weight +12+.3/3 !0s

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4e!ocity 31.1* ft%sec

Aspect ratio +./

&pan 2/+.22 ft

P!an form area 515.*55 s6.ft

Wing !oading +1.**/ !0s%s6.ft

"hrust !oading +./23

A!titude /23*5 ft

"hrust 5.*2 7 +8* !0s

Engine type )) ")E9"

&PE'II' E( '$9&;P"I$9 +.2+ < +8-* (=&%&E'

(E9>"? $ E9>I9E +.52/ "

WID"? $ E9>I9E .* "

9;=E) $ E9>I9E /

)eyno!ds num0er 2. 7 +8*

Dihedra! ang!e 2.15

"ip - chord ratio .+*5

)oot chord 22.+/

"ip chord 3.31+2

;ean chord +*.52

"a0!e +.+ )esu!t of Design )eport I

Aircraft design project-II dea!s with in depth design and ana!ysis of the

aircraft@s structura! and performance characteristics. In the ADP-II, we wi!! 0e

determining the fo!!owing design factors,

4-n diagram

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>ust enve!ope

!ight enve!ope

(oad estimation on wing and structura! design

Design of tai! p!ane and ai!erons

'AD drawings three view diagram

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2. V-N DIAGRAM FOR THE DESIGN STUDY

"he structura! design of the aircraft depends on the !oad imposed on the

aircraft during its mission profi!e. (oad re6uirements on aircraft are defined in

terms of the !oad factor, n.

2.1 LOAD FACTOR

"he !oad factor is defined as the ratio 0etween norma! aerodynamic force to

the aircraft weight.

n

or sma!! ang!e of attac#Bn Cdimension!ess

"raditiona!!y, its unit is referred as g, 0ecause of the re!ation 0etween n@ and

acce!eration of gravity fe!t on 0oard of the aircraft.

Aviation authorities specify the !oad factor !imits within which different

c!asses of aircraft are re6uired to operate without damage.

or commercia! transport airp!ane -+ to F.5

or !ight airp!ane -+ to F.5

or aero0atic airp!ane - to F*

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or he!icopters -+ to F.

nma7

nma7 C+./+%.1

nmax= 3.813

At steady !eve! f!ight, (W

"he various e7terna! !oads on the airp!ane are usua!!y represented on a graph of the

!imit !oad factor, n p!otted against the airspeed. "his diagram is 0etter #nown as the

4-n diagram.

"here are four important speeds used in the 4-n diagram,

+-g sta!! speed, 4&

Design cruise speed, 4'

Design driving speed, 4D

Design maneuvering speed, 4A

2.2 LOAD CONDITIONS

"here are two !oad conditions that the airp!anes must satisfy for their operation.

"hey are:

(imit !oad condition

!timate !oad condition

LIMIT LOAD

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"hese are ma7imum !oads that are e7pected in service, there shou!d not 0e

any permanent deformation at !imit !oad.

ULTIMATE LOAD

It is the va!ue of !imit !oad mu!tip!ied 0y the factor of safety. "he structure

must 0e a0!e to withstand the u!timate !oad for at !east seconds without fai!ure.

2.3 DETERMINATION OF STALL S!EED

&ta!! speed is the speed 0e!ow which the airp!ane cannot create enough !ift.

4&

V"= 3#$.1%$ &'(")*

'9ma7 G+./+82 F .25182H.

'9ma7 +./+13

'9ma7 +./+2+

2.% DETERMINATION OF CRUISE S!EED

'ruise speed is the speed of the airp!ane in steady !eve! f!ight.

4' '

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VC= 38+.33 &'(")*

' for norma! uti!ity aircraft upto CW%& 2 psi

' -25.* for 2-+

' * for aero0atic.

2., DETERMINATION OF DIVING S!EED

Diving speed is the speed of the aircraft at which it performs maneuvers.

4D +.2 4'

VD = %82.$++ &'(")*

2.+ DETERMINATION OF MANEUVERING S!EED

;aneuvering speed is the speed of the aircraft at which it performs

maneuvers.

4A 4&

VA = +#%.#13 &'(")*

2. LOAD FACTOR CALCULATIONS

n

n

Ca/ a0an) 4)a56 'an"/'7

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Positive !oad factor 2. B 9egative !oad factor -+.

4E($'I"J P$& 9E>

.2*+ .2*

+ .+/ .+/

+ .2 .2

2 ./+5 ./+5

2 .* .*

.3/+ .3/+

+.25+ +.25+

/ +.*1/ +.*1

/ 2.++3 2.++5

2.*+* 2.*+

.+* .+*

* .1*1 .1*

* /./2+ /./+3

1 .+21 .+2

1 .55* .55/

5 *.*31 *.*3/

5 1.*3 1.*

3 5./1 5./1+

3 3.// 3./3

+ +./* +./*

"a0!e 2.+ (oad factor positive and negative

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F0 2.1 4-n diagram

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3. GUST AND MANEUVERING ENVELO!E

(oads associated with vertica! gust must 0e eva!uated over the range of

speed. "he gust !oad for an aircraft are determined 0y first estimating the change in

ang!e of attac# upon enter in a sharp edged gust,

Where,

gust ve!ocity

4 aircraft speed

tan

"he change in !ift is estimated 0y change is ang!e of attac#.

K42 &

K42 &

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K42 &

V2 S

9 = #.8

L

: = 21#,.$83

ft%sec for a!titudes from sea !eve! to 2 ft.

**.*1-.5h for 2- ft.

Where,

M Density of air in !0s%ft

4 4e!ocity of the aircraft in ft%sec

&!ope of the !ift curve C9

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gust a!!evation factor

L ;ass ratio

>ust ve!ocity in ft%sec

"ota! ta#e-off weight

& Wing area, ft2

FOR LIGHT TRANS!ORT AIR!LANES

F/ ;"' 0n)

ft%sec 0etween -2 ft

**.*1-.53h, 2- ft

F/ ;"' 0n)

2 ft%s, -2 ft

./-./+1h, 2- ft

VELOCITY

F'(")*

!OSITIVE LOAD

FACTOR

NEGATIVE LOAD

FACTOR

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+ +

+.+3 .335

+ +.5 .33*

+ +.5 .33/

2 +.11 .332

2 +.3* .33+

+.+2 .355

+.+/ .351

/ +.+ .35

/ +.+1 .35

+.+3 .35+

+.2+ .313

* +.2 .311

* +.2 .31

1 +.21 .31

1 +.23 .31+

5 +.+ .3*3

5 +. .3*1

3 +. .3*

3 +.1 .3*

+ +.3 .3*+

Taust !oad positive N negative

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ig .+ >ust !oad

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%. !ERFORMANCE ESTIMATION FLIGHT ENVELO!E

THRUST RE>UIRED

"o maintain the speed and a!titude of the perpendicu!ar aircraft, enough

thrust must 0e generated to e7act!y overcome the drag and #eep the airp!ane going.

"his is the thrust re6uired to maintain these f!ight conditions,

"hrust re6uired depends on the ve!ocity, a!titude, aerodynamics,

shape, siOe and weight of airp!ane.

It is simp!y e6ua! to drag of the airp!ane it it is the ")to ocercome

aerodynamics drag.

P!ot showing the variation of the ")with free stream ve!ocity is ca!!edas the thrust re6uired curve

!O?ER RE>UIRED

Wor# done on the o0ject 0y force acting through the disp!acement dr is dr.

power is the time rate of wor# done.

Power 7 dr%dt

Power 7 4

STALL S!EED

4sta!! depends on the a!titude, wing !oading N ma7imum !ift coefficient. We

see that,

It increases with increase in a!titude, reconnect sca!e airp!ane that f!yat e7treme!y high a!titude must 0e !arge in order to generate enough

!ift to e6ua! the weight in rare fie!d air.

4e!ocity of the 4sta!! decreases with increase in the ' !ma7

It increases with increase in the wing !oading

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VSTALL = 3#$.1%$ &'(")*

RANGE

It is the tota! distance trave!!ed 0y airp!ane on the one !oad of fue!. We

denote the range in )

W gross weight of the airp!ane inc!ude everything

Wf weight of the fue!

W+ weight of an airp!ane when fue! is empty Ci.e Wf

R = %.#2, x 1#@1# &'

ENDURANCE

We want the airp!ane to have !ong endurance 0y definition it is the amount

of time ta#en 0y an airp!ane can stay in air !oad of fue! our main o0jective is

staying in air for !ong time.

E = .+21 4

GLIDING

Whenever an airp!ane is f!ying such that the power re6uired is !arge than the

power avai!a0!e.it wi!! descend rather than c!im0. In the u!timate situation, there is

no power at a!!. In this case, airp!ane wi!! 0e in the g!iding or 9 powered f!ight.

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VELOCITY

&'(")*

!OSITIVE LOAD

FACTOR

NEATIVE LOAD

FACTOR

+ +

+.25 +.2/

+ +.+5 +.+

+ +.2/ +.22/

2 +./2* +./+

2 +.**/ +.3+

+.3/ +.3

2.23 2.21

/ 2.*3 2.**

.+ .+

.* .*

/.+5 /.+/

* /.13 /.1/2

* ./ .3

1 *.+ *.3

1 *.3+ *.53

5 1.12 1.**

5 5.* 5.2

3 3.+ 3.5

3 +./5 +.

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+ ++. ++./2

TaUIRED !O?ER RE>UIRED

15+. ++53*1

+ /**32.2+ /**322+

+ 3131.3 +/*3*53.

2 +*1/+. 52++2

2 2***.// *+1**+2.

1/1+2+. ++2/+*/5

3*11+. +155*35*5

/ **/52.* 2**+32+*

5/2333.11 153//3531

+32/5.+/3 +31*2/2/

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+211/5/.+/ *3+1+*211

* +//*1**1.5/ 535*1/

* +1*11./ +./+11e+

1 21+153.*3 +./2e+

1 251.12 +.13e+

5 2**1.** 2.+25e+

5 1+5/.2 2.2e+

3 *1/1/*.52 .+e+

3 12+5.+ .*//e+

+ /+1/33.*2 /.+1e+

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ig /. Power re6uired curve

,. STRUCTURAL DESIGN STUDY-THEORY

,.1 LOADS ON STRUCTURAL COM!ONENTS

"he structure of an aircraft is re6uired to support two distinct c!asses of !oad.

>round !oads

Air !oads

GROUND LOADS

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>round !oads inc!ude a!! !oads encounter 0y the aircraft during

movement%transportation on the ground such as ta7ing and !anding !oads, towing

and hoisting !oads.

AIR LOADS

Air !oads comprises !oads imposed on the structure during f!ight 0y

maneuver and gusts.

'arrier 0orn aircraft are su0jected to catapu!t ta#e-off and arrested

!anding !oads.

(arge civi! aircraft have pressuriOed ca0ins for high a!titude f!ying.

Amphi0ious aircraft must 0e capa0!e of !anding on water and !and.

It re6uires a structure of a0ove strength to withstand the effects of

f!ight in e7treme!y tur0u!ent air.

"hese two c!asses of !oads can 0e further divided into,

&urface forces are the forces that act upon the surface of the

structure such as aerodynamic and hydrostatic forces.

=ody forces are which act over the vo!ume of structure and are

produced 0y gravitationa! and inertia! effects. "herefore, position of

the main under-carriage shou!d 0e such as to produce minimum

!oads on the wing structure, compati0!e with the sta0i!ity of theaircraft during ground maneuvers. "his may 0e achieved 0y

!ocating the under carriage just forward of the f!e7ura! a7is of the

wings and as c!ose to wing root as possi0!e.

"he 0asic structura! functions of an aircraft structure are to

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"o transmit and resist the app!ied !oads

"o provide an aerodynamic shape

"o protect passengers, pay!oad, systems.

These requirements in most aircraft result in thin shell

structure where the outer surface/skin of shell is usually

supported by longitudinal stiffening members & transverse

frames to enable it to resist bending, compressive and torsional

loads without buckling.

Wings, tai! p!ane and the fuse!age are su0jected to,

Direct 0ending !oads

&hear !oads and

"orsiona! !oads

"herefore, the structure mem0ers must 0e designed to withstand

com0ination of these !oads. Apart from the 0asic aerodynamic !oads acting on the

airp!ane. "he other !oads that act on airp!ane are,

?oop stress as car0ines are pressuriOed

=ending !oads due to weapons and e7tra fue! tan#s.

(oads acting due to the engine.

"hrust and weight of engine affect the fuse!age%wing depending on their

re!ative positions.

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>round !oads encounter in !anding and ta7ing su0ject the aircraft to

concentrated shoc# !oads through the undercarriage system. "he majority of

aircraft have their main undercarriage !ocated in the wings, nose%tai! whee! in the

vertica! p!ane symmetry.

,.2 ?INGS

"he structura! components of the wings are,

&pars

)i0s

&tringers And

in

,.2.1 RIBS

"he function of the ri0 is to maintain the shape of the cross section

which is governed 0y aerodynamic considerations and must 0e maintained for a!!

com0ination of !oad. "he dimensions of ri0s are governed 0y their span wise

position of wing. "he ri0s are re6uired to a0sor0s and transmit !arge concentrated

app!ied !oads such as those from the undercarriage, engine thrust and fuse!age

attachment point reactions.

,.2.2 S9IN

"he primary function of the wing s#in is to form an impermea0!e

surface for supporting the aerodynamic pressure distri0ution from whi!e the !ifting

capa0i!ity of the wing is derived. "hese aerodynamic forces are transmitted in to

the ri0s and stringers.

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,.2.3 STRINGERS

)esistance to the a7ia! and 0ending !oad is sustained 0y the spars andstringers on ri0s attachments for presenting co!umn action in the direction.

,.2.% S!ARS

)esistance to the shear and torsion !oad is app!ied 0y shear stress

deve!oped in the s#in.

ig .+ Wing section

,.3 FUSELAGE

"he purpose of the fuse!age is to safeguard the passengers and pay!oad.

"he shape of the fuse!age cross section is determined 0y operationa! re6uirements.

"he fuse!age supports the concentrated !oads such as,

Wing )eactions

"ai! P!ane )eactions

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nder 'arriage )eaction

"he structura! mem0ers of the fuse!age are,

rames

&tringers

=u!# ?eads

in

ee!son

ig .2 use!age structure

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+. LOAD ESTIMATION ON ?INGS

Parameters that are to 0e determined in the wing design processes are,

P!an form area, C&

9um0er of wings

4ertica! position re!ative to fuse!age

?oriOonta! position re!ative to fuse!age

'ross-section, Cairfoi!

Aspect ratio, CA)

"aper ratio, C

"ip chord, C't

)oot chord, C'r

;ean aerodynamic chord, C

Wing span, C0

"wist ang!e, CQt

&weep ang!e, C

Dihedra! ang!e, CR

Incident ang!e, Ciw

+.1 ?ING ?EIGHT ESTIMATION

CARGO A0an)"


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GD M)'4/

Wwing .5GCwnu!tW"$%Ct%cma7CCtan (E- 2C+- %AC+F 2F+. S+-

*H.3CAC+F .53C&.1/+H

w +. for fi7ed wing airp!ane

w +.+1 for varia0!e sweep wing airp!ane

(E (eading edge sweep ang!e

nu!t !timate !oad factor

W"$ "ota!-ta#e-off weight

"aper ratio

Ct%c "hic#ness-chord ratio

A) Aspect ratio

& Wing area

WWI9> C+125*+51GC+F.223 7 +8-* 7 +8-*H.3C+.1/31 7 2+.1*

??ING= 3.8,$$$ 1#@$


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If the !anding gear is not mounted under the wing, the wing weight is

reduced 0y T.

or 0raced wing, the wing weight is reduced 0y T.

or fow!er f!aps add 2T to wing weight.

+.2 ?ING LOAD DISTRIBUTION

"he !oads on the wing are made up of aerodynamic !ift, drag forces as

we!! as concentrated or distri0uted weight of wing mounted engines, stored fue!,

weapons, structura! e!ements, etc.

+.2.1 S!AN-?ISE LIFT DISTRIBUTION

As a resu!t of the finite aspect ratio of the wing, the !ift distri0ution vary

a!ong the span, from a ma7imum !ift at the root to a minimum !ift at tip. "he

span wise !ift distri0ution shou!d 0e proportiona! to the shape of the wing p!an

form. It can 0e ca!cu!ated 0y vorte7 pane! method. =y assuming the wing p!an

form as e!!iptic, ana!ytic span wise !ift distri0ution is given 0y,

(.E. Cy /(%0

Where,

(.E.Cy the tota! !ift generated 0y the wing with

the e!!iptica! p!an form

y span wise coordinate of the wing, i.e. y to y0%2

0 wing span in ft


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=y assuming the wing as trapeOoida! then the ana!ytic span wise

distri0ution is given 0y,

(.". Cy G+- H

Where,

(.". Cy trapeOoida! wing p!an form !ift distri0ution

taper ratio

?ING

S!AN67

ELLI!TICAL

LIFTDISTRIBUTION

LE67

?ING

S!AN67

TRA!EOIDAL

LIFTDISTRIBUTION

LE67

+523*.+2 *25./1

2 +31./ 2 3.*1

/ +/3+/*.3 / 12.51

* +1+/+.*2 * +//.1

5 ++5/.5* 5 /11.21

+ 551+.+/ + //./1

+2.* 1.23/ +2.* 32.*5*

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ig *.+ (ift curve

+.3 SCHREN9S A!!ROIMATION

According to c!assica! wing theory, the span wise !ift%!oad distri0ution is

proportiona! to the circu!ation at each station. A vorte7 !ifting U!ine ca!cu!ationwi!! yie!d the span wise !ift distri0ution.

or an e!!iptica! p!an form wing, the !ift N!oad distri0ution is of e!!iptica!

shape. or a non-e!!iptica! wing, a good semi-empirica! method for span wise

!oad estimation is #nown as schren#@s appro7imation. "he method assumes that

the !oad distri0ution on an untwisted wing has a shape that is the average of the

actua! p!an form shape and e!!iptica! shape of same area. "he tota! area under

the !oad curve must sum to the re6uired that !ift.

=y &chren#@s Appro7imation,

(

"he e6uation can 0e schren#@s curve is given 0y,


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y

Where,

a &emi wing spanC0%2 ft

0 Wing chord in ft

?ING S!AN IN

&'

STRUCTURAL LOAD IN


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(oad intensity at root,

(root CW"$% 2Syr%area under the curve

Where,

W"$ "a#e off gross weight

'r )oot chord in ft.

L/a a' an6 /*a'0/n n


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$n so!ving the a0ove e6uation we get va!ue at # in !0s%ft. "hus we can get the

structura! !oad of wing.

+.% SHEAR FORCE AND BENDING MOMENT DIAGRAM

"o determine the shear force and 0ending moment diagram for the wing

we assume that the wing is a canti!ever 0eam with the root and fi7ed whi!e tai!

end is free.

or a canti!ever 0eam the shear force is given as,

S4)a &/*) = Rx

or a canti!ever 0eam the 0ending moment is given 0y,

B)n0n M/m)n' = Rx2(2

R)";'an' /a R = L0&' /a /n ))m)n'" S';*';a /a /n ))m)n'

?ING S!AN

IN FTx7

RESULTANT

INTENSITY IN


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ig *. =ending moment curve

. FUSELAGE LOAD ESTIMATION

"he fundamenta! purpose of the fuse!age structure is to provide an

enve!ope o support the pay!oad, crew, e6uipment, systems and the power p!ant.

It must resist the in f!ight manoeuvres, pressuriOation and gust !oads. ina!!y, it

must 0e a0!e to transmit contro! and trimming !oads from the sta0i!ity and

contro! surface throughout the rest of the structure.

"here are two main categories of fuse!age !ayout,

;ass 0eam and (ongeron !ayout

&emi-;onoco6ue !ayout


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.1 FUSELAGE ?EIGHT ESTIMATION

Ca/ A0an)

Wf2 7 +./ GC#in!+./2 CVD %+.25CW"o%+.3C!f%hf.1+H

in! +. for 0uried engine

V( Dive dynamic pressure in !0s%s6ft

W"o "a#e-off gross weight

(f use!age !ength in ft

?t use!age !ength in ft

Wf 2.5* 7 GC. 7 .2 7 /523**2%+H.25G*+*/.+%+H.3G+3.+/%+5.H.31

Wf G23/5/.352% C+5..1+H

?&= +282.%8$


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Induced drag

.2.1 FRICTION DRAG

riction drag is direct!y proportiona! to wetted area. Wetted area is

direct!y re!ated to fuse!age !ength, perimeter of the fuse!age cross section. "o

reduce friction drag,

&hape the fuse!age so that !aminar f!ow is possi0!e.

)educe the !ength and perimeter as much as possi0!e.

.2.2 !ROFILE AND BASE DRAG

Profi!e and 0ase drag are a strong function of front and aft 0ody shape.

=ut the fore 0odies and 0!unt aft-0odies promote f!ow separation which !ead to

high profi!e and 0ase drag.

ree 0ody 0!untness is caused 0y,

Poor coc#pit window%canopy shaping

ront end !oading

"he idea! stream!ine nose can 0e achieved on!y if the wind shie!ds are

integrated smooth!y into the surface of the fuse!age.

.2.3 COM!RESSIBILITY DRAG

"he fuse!age e7periences the compressi0i!ity drag effects on!y at very

high su0sonic mach num0ers. "his drag occurs due to the e7istence of shoc#s

on the fuse!age. "he area ru!e concept must 0e used to minimiOe compressi0i!ity

drag.

.2.% INDUCED DRAG


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A fuse!age contri0utes to induced drag primari!y 0ecause of its adverse

effect on wing span !oad distri0ution. When a fuse!age is e6uipped with !eading

edge stra#es%the fuse!age is sharp!y 0!ended into the wing, there wi!! 0e

significant effect on the fuse!age induced drag.

8. EM!ENNAGE DESIGN

Empennage%tai! in a conventiona! aircraft has two components, horiOonta!

tai! and vertica! tai! and carries two primary functions.

"rim C!ongitudina!, !atera! and directiona!

&ta0i!ity C!ongitudina! and directiona!


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It has two conventiona! contro! surfaces i.e., e!evator and rudder. "he

function of thee contro! surfaces are,

'ontro! C!ongitudina! and directiona!

"he fo!!owing parameters are needed to 0e determined during design

process

"ai! configuration

?oriOonta! tai! !ocation with respect to fuse!age

8.1 HORIONTAL TAIL

P!anform area Csht

"ai! arm !ength C!t

Airfoi! section

Aspect ratio CA) t

"aper ratio C t

"ip chord Cct,tip

)oot chord Ccr,root

;ean Aerodynamic chord C;A't

&pan C0t

&weep ang!e C t

Dihedra! ang!e C t


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"ai! insta!!ation

Incidence Cit

8.2 VERTICAL TAIL

P!anform area Csvt

"ai! arm C!vt

Airfoi! section

Aspect ratio CA)vt

"aper ratio C vt

"ip chord Cct

)oot chord Ccr

;ean aerodynamic chord C;A'vt

&pan C 0vt

&weep ang!e C vt

Dihedra! ang!e C vt

Incidence Cit

8.3 AIRCRAFT TRIM RE>UIREMENTS

"rim is one of the re6uirements of a safe f!ight. When an aircraft is at

trim, the aircraft wi!! not rotate a0out its centre of gravity.

"he aircraft trim must 0e maintained a0out three a7es C7, y and O.


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(atera! trim, C7

(ongitudina! a7is Cy

Directiona! a7is CO

8.3.1 LONGITUDINAL TRIM

When the summation of a!! forces in 7-direction is Oero, and the

summation of a!! moments a0out y a7is is Oero.

i.e., B

"he horiOonta! tai! is responsi0!e to maintain !ongitudina! trim.

?oriOonta! tai! can 0e insta!!ed 0ehind the fuse!age or c!ose to the nose.

8.3.2 DIRECTIONAL TRIM

When the summation of a!! forces in y direction is Oero and the

summation of a!! moments a0out O a7is is Oero, the aircraft is said to have the

directiona! trim.

i.e., B

"he vertica! tai! is responsi0!e to maintain directiona! trim.

8.3.3 LATERAL TRIM

When the summation of a!! forces in -direction and moments a0out 7

direction is Oero, the aircraft is said to have trim.

i.e., B


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';owfF '(Ch U ho - c(t

horiOonta! tai! vo!ume coefficient

VH=

"hus the e6uation can 0e further simp!ified to,

';owfF '(Ch U ho U 4?'(

"he wing Uuse!age pitching moment co efficient Cc;owf is given 0y

';owf c;ow F .+ t

Where,

';owf is the wing pitching moment co-efficient

A) is the wing aspect ratio

is the wing sweep ang!e

tis the wing twist ang!e in degrees

Due to the effect of wing and fuse!age on the horiOonta! tai!, a new

parameter 0etween the dynamic pressure at tai! to the aircraft dynamic pressure

It is ca!!ed the Ta0 E&&0*0)n*6 '7


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t C 2

4 is the aircraft speed

4tis the effective airspeed at the ?oriOonta! tai!

"he typica! va!ue of the tai! efficiency for an aircraft with conventiona!

tai! is varied from .5 to .3

! -Distance 0etween wing A.c and horiOonta! tai! A.'

(-Aircraft overa!! !ength.

8.3.% DIRECTIONAL AND LATERAL TRIM

$ne of the primary functions of the vertica! tai! is to provide directiona!

and !atera! trim.

An aircraft is said to 0e in directiona! trim, the summation of a!! moments

a0out O-a7is wi!! 0e Oero. Ci.e.

An aircraft is said to 0e in !atera! trim, the summation of a!! moments

a0out 7-a7is wi!! 0e Oero. Ci.e.,

"o maintain the directiona! and !atera! trim, an aerodynamic force a!ong

y-a7is is needed which is created 0y the vertica! tai!.

"he Wing-use!age !ift C(wf is the wing !ift C(w when the contri0ution of

fuse!age !ift C(f is inc!uded. "he fuse!age !ift is a0out +T of the wing !ift.

or c.g 0efore A.' U;owfis negative


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or c.g after A.'-;owfis positive

;owfF ;(wf F ;(!t

;owfF (wfChc U hoc U (t!t

(wf sc(wf

(t stc(t

;owf scmac

AOA CL CM#& 4 4#

.*1+ -./

+ .++5 .*13 .++325

2 .2* .**2 .22

. .**2 ./3

/ ./1+ .* ./*1

.55 .*/+ .5/

* .1 .* .1+

1 .522 .*+ .5+5

5 .35 .5 +.

3 +./ .1 +.+*1

+ +.+1 . +.25+

++ +.25/ . +.3*


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+2 +./ . +./1

+ +./5 .2 +.

+/ +. .+ +./5

+ +./5 . +./5

+* +./ ./3 +./

+1 +. ./1 +.

+5 +.2 ./ +.2

+3 +.2 ./+ +.2

2 +.5 .5 +.5

Ta


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&ta0i!ity is defined as the tendency of an aircraft to oppose a distur0ance

and return to its initia! steady state condition is distur0ed.&ta0i!ity is divided

into,

&tatic &ta0i!ity

Dynamic &ta0i!ity

An aircraft motion has si7 degrees of freedom, one !inear and one

rotationa! a0out each three a7is 7, y and O. "herefore, sta0i!ity is measured

a0out these three a7is name!y,

(atera! &ta0i!ity

(ongitudina! &ta0i!ity

Directiona! &ta0i!ity

"he directiona! and !atera! trim e6uation are:

") J" F (4 !4

(E F (4 4

Where,

") Engine thrust

J" "he distance 0etween the thrust !ine and the '.> of the airp!ane

(E Jawing moment generated 0y prope!!er

4 "he distance 0etween the vertica! tai! A.' to '.> of the airp!ane

!4 "he distance 0etween the horiOonta! tai! A.' to '.> of the airp!ane


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"he vertica! tai! !ift is generated 0y,

LV= V2SVCLV

8.%.2 CONTROL

'ontro! is defined as the a0i!ity of an aircraft to vary the aircraft

condition. "hree types of the aircraft contro! are,

(atera! 'ontro!

(ongitudina! 'ontro!

Directiona! 'ontro!

8., TAIL CONFIGURATION

Aft tai! and one aft vertica! tai!

Aft tai! and twin aft vertica! tai!

'anard and aft vertica! tai!

'anard and twin wing vertica! tai!

"rip!ane

De!ta wing with one vertica! tai!

ighter aircraft ?oriOonta! tai! vo!ume co-efficient VH7 = #.%

4ertica! tai! vo!ume co-efficient VV7 = #.#

8.+ O!TIMUM TAIL ARM

$ne of the tai! parameters that must 0e determined during the tai! design

process is the tai! arm C!t, which is the distance 0etween tai! aerodynamic center

to the aircraft@s centre of gravity. "he two 0asic tai! parameters that interact are


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tai! arm and tai! area, if the tai! arm is increased, the tai! area must 0e decreased

and vice-versa.

or the optimum tai! arm !ength, we must !oo# into other design

re6uirements. "he most significant genera! design re6uirements are !ow weight

and !ow drag. "he common so!utions for 0oth these design re6uirements are !ow

aircraft wetted area.

As the horiOonta! tai! arm is increased, the fuse!age wetted area is

increased, the horiOonta! tai! wetted area is decreased. If the tai! arm is

decreased, the fuse!age wetted area is decreased, 0ut horiOonta! tai! wetted areais increased.

If the tota! wetted area is minimiOed, the aircraft Oero-!ift drag wi!! 0e

minimiOed. "he wetted area of the aft portion of the aircraft is the summation of

the wetted area of the aft fuse!age p!us the wetted area of the horiOonta! tai!.

&wet.aft &wet aft fuse!age F &wet ht

We assume that aft portion of the fuse!age is conic. "herefore the wetted

area of the aft portion of the fuse!age is,

&wet, aft fuse!age

Where, Dfis the minimum fuse!age diameter.

(fuse!age afthaftthe fuse!age !ength C(f

&wet ht2&t

We #now that, 4?


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&wet ht

&wet aft

"he optimum tai! arm is o0tained 0y so!ving,

"o compensate our inaccurate assumption,

Where,

'varies from + to +./

8. AIRFOIL SECTION

?oriOonta! tai! p!ane is a !ifting surface and re6uires a specia! airfoi!

section, tai! p!ane re6uires an airfoi! section that is a0!e to generate !ift with

minimum drag and minimum pitching moment.

&ince the aircraft cg moves during the cruising f!ight, the airfoi! section

must 0e a0!e to create 0oth positive and negative !ift. "he tai! p!anes shou!d

0ehave simi!ar in 0oth positive and negative ang!e of attac#.


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or this reason, a symmetric airfoi! section is a suita0!e for horiOonta! tai!.

&ome of the airfoi!s are,

9A'A 3

9A'A +

9A'A +2

9A'A *-*

9A'A *-3

9A'A *-+2

9A'A *-+5

9A'A */-*

9A'A */-+2

9A'A */A+

9A'A *-3

9A'A **-+2

9A'A **-+5

9A'A **-2+

AOA CL

+ .++5

2 .2*

.


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/ ./1+

.55

* .1

1 .522

5 .35

3 +./

+ +.+1

++ +.25/

+2 +./

+ +./5

+/ +.

+ +./5

+* +./

+1 +.

+5 +.2

+3 +.2

2 +.5

Ta


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"he tai! ang!e incidence re6uirements are:

QeffwXQefft Cconventiona! configuration

QeffeXQeffw Ccanard configuration

Due to presence of the downwash at the horiOonta! tai! !ocation, the tai!

effective ang!e of attac# is defined as,

Where,

is the fuse!age Ang!e $f Attac#

YYF

where,

Ydownwash at Oero Ang!e $f Attac#

downwash s!ope

Y

Where,


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wing !ift curve s!ope in +%rad

wing !ift co-efficient

An intermediate horiOonta! tai! parameter that must 0e determined is its

!ift curve s!opeC .

"he horiOonta! tai! !ift curve s!ope is determined as fo!!ows:

horiOonta! tai! airfoi! section

8.$ TAIL AS!ECT RATIO

"he tai! aspect ratio has inf!uence on the aircraft !atera! sta0i!ity, contro!,

aircraft performance, tai! aerodynamic efficiency.

Ta0 a")*' a'0/is defined as the ratio 0etween tai! span to the mean

aerodynamic chord.

"ai! aspect ratio C tends to have a direct effect on the tai! !ift curve

s!ope. As the tai! aspect ratio is increased, the tai! !ift curve s!ope is increased. A

!ower aspect ratio is desira0!e for tai!, compared with that of the wing. "he

reason is that the def!ection of the e!evator creates a !arge 0ending moment at

the tai! root. "he !ower the aspect ratio resu!ts in a sma!!er 0ending moment.

An initia! va!ue for the tai! aspect ratio may 0e determined as:


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A)t .**1 C+.

AR'= 1.#

8.1# TA!ER RATIO

t G*/.2+%21.25H

' = #.2,

;ean aerodynamic chord,

C = 1+.#8

8.11 VERTICAL TAIL DESIGN

"he vertica! tai! have two primary function,

Directiona! sta0i!ity

Directiona! trim

"he vertica! tai! is a major contri0utor in maintaining directiona! contro!

which is the primary function of the rudder. "o maintain the aircraft directiona!

trim, the summation of a!! moments a0out -a7is must 0e Oero.i.e., ZyB

Z9cg."he vertica! tai! parameters that are to 0e determined are,

4ertica! tai! !ocation C4


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P!anform area C&4

"ai! arm C!vt

Airfoi! section

Aspect ratio CA) v

"aper ratio C v

"ip chord C't v

)oot chord C'r v

;ean aerodynamic chord Cm.a.cv


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$. ?ING STRUCTURAL DESIGN

In this section, we wi!! 0e studying a0out the structura! design

components such as, spar, ri0s and stiffeners spacing@s.

$.1 RIBS AND S!ARS

"he ri0s of the wing are chord-wise structures which maintain the wing

shape, prevent 0uc#!ing of the s#in and a!so support shear !oads. "he spars span

the !ength of the wing and support most of the 0ending cause 0y aerodynamic

!oads. "heir resu!ts show minima! variation 0etween each aircraft and hence the

averages have 0een used for the interna! support !ayout. or a 2 spar !ayout the

spars shou!d 0e !ocated at 2T and *T from the !eading edge of the chord and,

in our design, this !ocation wi!! not vary with span. "his a!!ows for the 0estdistri0ution of !oads as the front e7periences the most aerodynamic !oading.

"he ri0s are typica!!y e6ua!!y spaced a!ong the !ength of the wing. "his is

due to maintenance access re6uirements. $ver virtua!!y a!! mode!s, and hence

inc!uded in our design the spacing is 2. ft measure a!ong the wing or

appro7imate!y 2 ft perpendicu!ar to the fuse!age.

$.1.1 TY!ICAL S!AR RIB AND STIFFER S!ACING


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"he actua! structura! arrangement of span, ri0s and s#in stiffeners depends

very much on the type of airp!ane 0eing designed and !oad to which it wi!! 0e

su0jected.

$.2 ?ING S!AR LOCATION

;ost airp!ane wings use a so ca!!ed tor6ue 0o7%wing 0o7 as the main !oad

carrying component. "he tor6ue 0o7 shou!d 0e !oaded to ta#e ma7imum

advantage of the structura! height within the airfoi! contours. "his wi!! save

weight.

$.3 ?ING(FUSELAGE INTEGRATION

Wings are norma!!y joined to a fuse!age in the fo!!owing method:

Wings are 0o!ted to a fuse!age 0y using [carry through[ section.

Wings inc!uding the carry through sections are joined to the fuse!age

0y a !arge num0er of sma!! 0o!ts.

$.% TOR>UE BO(?ING BO CONFIGURATION

&evera! 0asic wing 0o7 configurations are

;ass 0oom concept

=o7 0eam

&ing!e spar, D-nose

;u!ti-spar

"he tor6ue 0o7 is norma!!y c!osed off 0y a front spar C.&, a rear spar C).&

and upper and !ower s#in. "he spar !ocations are constrained 0y re6uirements of

high !ift devices. "ypica! spar !ocations are:

ront spar:+-T of chordB

)ear spar: *-1T of chord.


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;u!ti spar construction is app!ied in case of fighter

wings.

$., ?ING RIB LOCATION

"o sta0i!iOe tor6ue 0o7, s#ins and to serve as attachment points for !eading

edge s#ins, trai!ing edge s#ins, f!aps, ai!eron and spoi!ers, wing ri0s are used.

or !ight airp!ane:* inches

or transport airp!ane:2/ inches

or fighter aircraft: ri0 spacing vary wide!y

$.+ ?ING STIFFNER S!ACING

"hese vary wide!y and depend on the re!ative stiffness of the wing s#in.

Wing section consists of thin s#in stiffened 0y com0ination of stringers, spar

we0s, caps and ri0s.


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1#. STRUCTURAL DESIGN

rom a structura! design point view, the fuse!age is a component to which

the wing, the empennage and in some instance !anding gear and nace!!e are

attached. "he fuse!age structure must 0e designed so that the fo!!owing types of

!oad can 0e ta#en without major structura! fai!ures%without major structura!

fatigue pro0!ems.

Empennage !oads due to trim, manoeuvring, tur0u!ence and gusts.

Pressure !oads due to ca0in pressuriOation.

(anding gear !oads due to propu!sion insta!!ation when the !atter is

attached to fuse!age

During crashes, the fuse!age must provide sufficient protection to prevent

injuries to its occupants. 'a0in materia!s must 0e used for round proofing,

decorative pane! seats must generate tonic fumes when e7posed to fire.

1#.1 TY!ICAL FRAME DE!THS FRAME S!ACING LONGERON

S!ACING

1#.1.1 Fam) )'4"


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or !arge transport aircraft C.2 F df inches

or sma!! commercia! airp!anes +. inches

or fighters and trainers 2 inches

1#.1.2 Fam) "a*0n

"ransport aircraft +5.22 inches

ighters and trainers + to2 inches

1#.1.3 L/n)/n "a*0n

ighters and trainers 5 to +2 inches

1#.2 FUSELAGE FRONT CROSS-SECTIONAL LAYOUT

!ASSENGER SEATS

!ARAMETER DIMENSIONS

&eat width +*-+5 inches

&eat pitch -2 inches

Asi!e width X+ inches

Asi!e height X* inches

(avatories%passengers +%C/-

=aggage%Passengers / !0s

"A=(E +.+ Passenger seats

"he two main categories of fuse!age are:

;ass 0oom and !ongeron !ayout

&emi-;onoco6ue !ayout

1#.3 MASS BOOM AND LONGERON LAYOUT


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"his is simi!ar to the wing 0on concept. It is used when the overa!!

structured !oading is re!ative!y !ow or when there are e7tensive cut-outs in the

she!!.

"he concept comprises four%more continuous heavy 0ooms, reacting

against any direct stress caused 0y app!ied vertica! and 0ending !oads.

rames%0u!#heads are used at positions where there are distinct directions

changes and possi0!y to e!sewhere a!ong the !ength of the !ongeron mem0ers.

"he outer she!! he!ps to support the !ongerons against the app!ied compression

!oads.

1#.% SEMI MONOCO>UE LAYOUT

"his is the most common !ayout used for the transport type aircraft, with a

re!ative!y sma!! num0er and siOe of cut-outs in use. "he s#in carries most of the

!oading with the s#in thic#ness determined 0y pressuriOation, shear !oading and

fatigue. (ongitudina! stringers provide s#in sta0i!iOation and a!so contri0ute to

the overa!! !oad carrying capacity. Increased stringers cross section siOes and

s#in thic#ness are often used around edges of cut-outs. rames are used to

sta0i!iOe the resu!tant.

1#., FUSELAGE SECTION

use!age genera!!y comprises of,

&tringers%!ongerons

rames

in and =u!#head


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