Diagnostic Investigation of Aircraft Performance at Different Winglet Cant Angles

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World Academy of Science, Engineering and Technology

International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering Vol:8, No:12, 2014

Diagnostic Investigation of Aircraft Performance atDifferent Winglet Cant Angles

Dinesh M., Kenny Mark V., Dharni Vasudhevan Venkatesan, Santhosh Kumar B., Sree Radesh R., V. R. Sanal Kumar

The induced drag is a different type of drag. It is caused by the

AbstractÐComprehensive numerical studies have been carriedpressure imbalance at the tip of a finite wing between its upper

out to examine the best aerodynamic performance of subsonic aircraft(pressure side) and lower (suction side) surfaces. That

at different winglet cant angles using a validated 3D k-w SST model.imbalance is necessary in order to produce a positive lift force.

In the parametric analytical studies NACA series of airfoils are Ho

ever, near the tip the high pressure air from the lo

er sideselected. Basic design of the inglet is selected from the lite

rature4 and flo features of the entire ing including the inglet tip effects

tends to move up ards, here the pressure is lo er, causing60 have been examined ith different cant angles varying from 150 to the streamlines to curl (see Fig. 1). This three-dimensional00 0 00 60 at different angles of attack up to 14 . We have observed, among

motion leads to the formation of a vortex, hich alters the

01 0/ the cases considered in this study that a case, ith 15 cant angle the

flo

field and induces a velocity component in the do

n

ardnoi aerodynamics performance of the subsonic aircraft during takeofft

direction at the ing, called do n ash [2]-[4]. The induceda 0c as found better up to an angle of attack of 2.8 and further itsi

lflo pattern causes the relative velocity to cant do n ards at

b performance got diminished at higher angles of attack. AnalysesuP 00 each airfoil section of the ing, thus reducing the apparent/ further revealed that increasing the

inglet cant angle from 15 to 60gr

angle of attack. The lift vector is tilted back ards and a force


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o. at higher angles of attack could negate the performance deteriorationtes and additionally it could enhance the peak C /C on the orderof component in the direction of the drag appears, called induceda L D 3.5%. The investigated concept of variable-cant-angle inglets drag. Reducing the size of this tip vortex and minimizing the41 appears to be a promising alternative for improving the aerodynamic0

induced drag is of great importance for the modern aircraft2, efficiency of aircraft.2

designers. For this purpose designers developed the

inglet1:o

concept. Winglets are specially designed extensions adjustedN, Key

ordsÐAerodynamic efficiency, Cant-angle, Drag8

to the

ingtip that alter the velocity and pressure field and

: reduction, Flexible Winglets.lo

reduce the induced drag term, thus increasing aerodynamicV

gefficiency.

ni I. INTRODUCTIONree

n HE main purpose of any inglet is to improve the aircraftign Tperformance by reducing its drag [1]-[25]. The termE

la inglet as previously used to describe an additional liftingcina surface on an aircraft. Wingtip devices are usually intended to

hce improve the efficiency of fixed-

ing aircraft [1]. There areM

d several types of ingtip devices, and although they function innae different manners, the intended effect is al ays to reduce thec


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a aircraft's drag by partial recovery of the tip vortex energy.psor Wingtip devices can also improve aircraft handling

eA, characteristics and enhance safety. Such devices increase thexed effective aspect ratio of a

ing

ithout materially increasing

nIe the ingspan. Note that an extension of span ould reduce the

Fig. 1 Demonstrating the tip vortex of a fixed

ing aircraftcne lift-induced drag, but ould increase parasitic drag and ould

ic

S require boosting the strength and

eight of the

ing.Bourdin et al. [5] reported that the investigated concept oflan It is ell kno n that any sort of body exposed in a viscous

variable-cant-angle inglets appears to be a promisingoita flo experiences profile drag, hether it produces lift or not.

alternative to conventional control surfaces such as ailerons,nr

etelevators, and rudders as far as basic maneuvers are

nI

Dinesh as an undergraduate student of Aeronautical Engineering, concerned. The concept consists of a pair of

inglets

ithKumaraguru College of Technology, Coimbatore ± 641 049, Tamil Nadu,

adjustable cant angle, independently actuated and mounted atIndia; (e-mail: [email protected]).

Kenny Mark, Dharni Vasudhevan, Santhosh Kumar, and Sree Radesh arethe tips of a baseline flying ing. A potential application for

Undergraduate Students of Mechanical Engineering, Kumaraguru College ofthe adjustable inglets ould be for surveillance aircraft, forTechnology, Coimbatore ± 641 049, India (Phone: +91-9894467086, e-

hich enhanced lo -speed maneuverability is required. Notemail:[email protected],[email protected],[email protected], [email protected]).

that deflecting a

inglet

hen the

ing is flying near its stallSanal Kumar is Professor and Aerospace Scientist and currently ith th

e angle is unlikely to cause the ing to stall (in contrast to thedepartment of Aeronautical Engineering, Kumaraguru College of Technology,


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effect of an aileron). Hence, variable cant-angle inglets canCoimbatore ± 641 049, Tamil Nadu, India; (Corresponding Author, ph

one: be used for effective lo -speed roll control (instead of spoilers+91 ± 938 867 9565; + 91 ± 875 420 0501, e-mail:[email protected]).

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hich are traditionally preferred to ailerons in that flightbe close to its optimal efficiency. Fig. 3 found in literature isregime).

reproduced here

ith for a critical revie

. It sho

s that lo

est

total drag is at a particular airspeed. Note that Pilots ill use

this speed to maximize the gliding range in case of an engine

failure. Ho ever, to maximize gliding endurance, aircraft's

speed should be at the point of minimum power, which occurs

at lower speeds than minimum drag.

Fig. 2 Front view of a fixed wing aircraft with fixed winglet460 Fig. 2 shows the front view of a typical aircraft with winglet000 at fixed cant angle. Numerical and experimental studies01/n conducted by the earlier investigators on a flying wing

oit configuration showed that adjustable winglets enable controlacil moments about multiple axes, forming a highly coupled flightbuP


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Md patented the first functional winglets in 1910. Somerville

vortex to an apparent thrust. This small contribution can benae installed the devices on his early biplane and monoplane

worthwhile over the aircraft s lifetime, provided the benefitcap designs. Wingtip devices increase the lift generated at the

offsets the cost of installing and maintaining the winglets.so wingtip (by smoothing the airflow across the upper wing nearr

Another potential benefit of winglets is that they reduce theeA, the tip) and reduce the lift-induced drag caused by wingtip

strength of wingtip vortices, which trail behind the plane andxe vortices, improving lift-to-drag ratio. This increases fuel

pose a hazard to other aircraft. Minimum spacing requirementsdn

Ie efficiency in powered aircraft and increases cross-countrybetween aircraft operations at airports is largely dictated by

cn speed in gliders, in both cases increasing range [1].

these factors. Aircraft are generally classified by weighteic The literature review reveals that the United States AirS

because the vortex strength grows with the aircraft lift

l

a Force studies could come up with the improvement in fuelncoefficient, and thus, the associated turbulence is greatest at

oit efficiency, which correlates directly with the causal increase ina

low speed and high weight.nre the aircraft s lift-to-drag ratio. In flight, induced drag resultst

The drag reduction permitted by winglets can also reduce

nI from the need to maintain lift. It is greater at lower speeds

the required takeoff distance [8]. Winglets and wing fences

where a high angle of attack is required. As speed increases,also increase efficiency by reducing vortex interference withthe induced drag decreases, but parasitic drag increases

laminar airflow near the tips of the wing [7], by moving thebecause the fluid is striking the object with greater force, and

confluence of low-pressure (over wing) and high-pressure


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is moving across the object s surfaces at higher speed. As(under wing) air away from the surface of the wing. Wingtip

speed continues to increase into the transonic and supersonicvortices create turbulence, originating at the leading edge ofregimes, wave drag enters the picture. Each of these drag

the wingtip and propagating backwards and inboard. Thiscomponents changes in proportion to the others based on the

turbulence delaminates the airflow over a small triangularspeed. The combined overall drag curve therefore shows a

section of the outboard wing, which destroys lift in that area.minimum at some airspeed; an aircraft flying at this speed will

The fence/winglet drives the area where the vortex forms

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International Journal of Mechanical, Aerospace, Industria

l, Mechatronic and Manufacturing Engineering Vol:8, No:12, 2014

uppward away ffrom the wingg surface, sinnce the centerr of the benefits for corrporate travell. In addition to factory-innstalled

reesulting vortexx is now at tthe tip of thee winglet. Thheseare wiinglets on neew aircraft, aftermarket vendors devveloped

suuccinctly reported in the opeen literature [ 1]-[25].rettrofit kits, forr popular jets and turboprops, to improvve both

aerrodynamics annd appearancee. Winglets beecame so popuular on

TTABLE ISPECIFICAATIONS OF WINGthiis class of airrcraft that thee Dassault Grroup, whose FFrenc

h

designers resistted applying them on theeir Falcon linee untilSl. No. Description Dimension

reccently, were fforced to run aa contrarian mmarketing cammpaign.1 Airfoil Type NACA 0012

Off late Cessna disclosed to ttest a new wingtip device called

2 Wing Type Swept Back0

Ellliptical Wingllets, which arre designed too increase rannge and3 Sweep Angle 32.434 Wing Span 22 cm

inccrease payloaad on hot annd high depaartures. It hass been5 Taper Ratio 0.292553

revvealed througgh this literatture review thhat winglet ddesigns

6 Aspect Ratio 3.62139


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muust be optimizzed to be ablee to get maximmum benefits during

27 Wing Area 133.65 cm

cruuise and non-ccruise flight cconditions; and for that 3D design8. Maximum Chordd 9.4 cm

opptimization is inevitable. TTherefore, 3DD numerical studies9. Minimum Chordd 2.75 cm

4haave been carrried out for examining the possibilitties

of600 TABLE II

inccreasing the aaerodynamics efficiency off a typical winng with000 SPECIFICATTIONS OF WINGLEET

vaariable-cant-anngle winglets.1/no Sl. No. Descripption Dimenssion

ita 1 Winglet Type Blended WWingletcilb 2 Winglet Span 3 cmmuP/ 3 Winglet HHeight 3 cmmgr

o 2

t. 4 Winglet Area 9.255 cmce

0 s 0

Fig. 4 Physical model of a wwing with wingllet Cant-Angle 15a 5 Winglet Sweeep Angle 47.299w

4 6 Winglet Tapper Ratio 0.109

10 7 Maximumm Chord 2.75 ccm2

, 8 Minimumm Chord 0.3 cmm21:o


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N

, Aircraft suchh as the Airbuus A340 and the Boeing 7747-4008:l usse winglets. OOther designs such as soome versions of theoVg Boeing 777 andd the Boeing 7747-8 omit thhem in favor oof rakednir wwingtips. Largee winglets suuch as those seen on Boeiing 737eeni aiircraft equippeed with blendeed winglets arre most usefull duringgnE shhort-distance flights, wherre increased climb perfoormance

lac offfsets increaseed drag. Notte that the raaked wingtipss are a

ina feeature on somee Boeing airlinners, where thhe tip of the wwing hashce a higher degreee of sweep thaan the rest of the wing. Thee statedM

d puurpose of this additional feaature is to impprove fuel effficiencyna

e annd climb perfoformance, andd to shorten taakeoff field length. It

ca

p dooes this in much the saame way thaat winglets do,byso

Fig. 5 3-D grid system iin the computattional domainr inncreasing thee effective aspect ratio of the winng andeA

, innterrupting haarmful wingttip vortices. This decreasses the xe

IIII. NUMERICAL METHODOOLOGYd ammount of lift--induced dragg experiencedd by the aircraft. InnIe testing by Boeeing and NAASA, raked wwingtips havve been


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Numerical simmulations havve been carrieed out with thhe helpcne shhown to reduuce drag by aas much as 55.5%, as oppoosed to

of f a steady 3DD, double precision, pressuure-based, SSST k-wicS immprovements of 3.5% to 44.5% from coonventional

ingletsturrbulence moddel. This moddel uses a coontrol-volume based

lan [99]. While an eequivalent incrrease in

inggspan

ould bbe moretecchnique to coonvert the gooverning equuations to alggebraic

oita efffective than aa inglet of thhe same lengtth, the bendinng force

eqquations. The viscosity is determined ffrom the Suthherlandnret beecomes a greaater factor. AA three-foot

inglet has thhe same forrmula. The iing geometricc variables andd material proopertiesn

I beending force as a one-foot increase in span, yet givves thearee kno n a priori . Initiial all temmperature andd

inletsaame performannce gain as a t o-foot ingg span increasse [10].temmperature aree specified. AAt the exit, far field bouundary

Foor this reason,, the short-rannge Boeing 7887-3 design caalled forcondition is preescribed. At tthe solid allls no-slip bouundary

inglets insteaad of the rakeed ingtips ffeatured on alll othe

r condition is impposed. The Coourant-Friedricchs-Le y nummber is7887 variants.chhosen as 1.0 inn all of the computations. TThe turbulent kinetic

Winglets aree also appliedd to several oother business jets to ennergy and the specific dissippation rate aree taken as 0.88. Idealreeduce take-offff distance, ennabling operaation out of smallergaas

as selectedd as the

orkiing fluid. Inlett velocity is taaken asseecondary airports, and alloo ing higher cruise altituudes for55.55 m/s, ithh turbulence iintensity of 5 %. Tables I and I

Iovverflying bad

eather, bothh of

hich are valuable operrationalshoo the geommetric detailss of the inng and the inglet

considered in thhis study. Fig. 4 sho s the pphysical modeel of an

International Scholarly and Scientific Research & Innovation 8(12) 20142054 scholar. aset.org/1999.8/10000064

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International Journal of Mechanical, Aerospace, Industria


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l, Mechatronic and Manufacturing Engineering Vol:8, No:12, 2014

0aircraft

ing

ith 15

inglet cant angle. Fig. 5 sho

s the 3Dgrid system in the computational domain. Grid are selectedafter a detailed grid refinement history (Cells: 140144, Faces:929653, Nodes: 780461). The grids are clustered near the solid

alls using suitable stretching functions. Orthogonal Qualityranges from 0 to 1, here values close to 0 correspond to lo quality. Minimum orthogonal quality

as 7.28711 E-01 andmaximum aspect ratio as 2.60710 E+01.

IV. RESULTS AND DISCUSSION

It is

ell kno

n that

inglets application is one of the mostFig. 8 Comparison of aerodynamic performance (C /C ) at different

L D

noticeable fuel economic technologies on aircraft. The angles of attack

ithout and

ith

inglet at different cant anglesdiagnostic investigation reveals that the inglet designs must

Fig. 6 sho s the comparison of lift coefficient (C ) atbe optimized to be able to get maximum benefits during cruise

L4

different angles of attack ithout and ith inglet orienting at6 and non-cruise flight conditions. In this paper comprehensive0

0 0 0 0

0 four different cant angles viz., 15 , 30 , 45 and 60 . It is0 numerical studies have been carried out to examine the best0

00

evident from Fig. 6 that a case

ith cant angle 60 is giving the1 aerodynamic performance of subsonic aircraft at different/n

highest coefficient of lift at various angles of attack (0-14).

o

inglet cant angles using a validated 3D k-w SST model. Inita

Nevertheless, as evident in Fig. 7, this trend is not seen hileci the parametric analytical studies NACA series of airfoils arelb

comparing the drag coefficient (C ) at different angles of


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u selected. Basic design of the inglet is selected from theD

P0

/g literature and flo

features of the entire

ing including the tipattack. One can discern from Fig. 7 that a case ith 60 c

antro.

0 0t effects have been examined

ith different cant angles varyingangle CD is relatively high up to 2.8 than a case ith 15 c

antes

0a 0 0 0

angle and further it diminishes up to 12 angle of attack and

from 15 to 60 at different angles of attack up to 14 .4

again it increases due to change in flo

features. These10

2

variations are corroborated ith C /C curves, hich are,

L D21

sho n in Fig. 8. It is evident from Fig. 8 that aerodynamic:oN

0

, performance of an aircraft ith inglet at a cant angle of 158

0

:l

is giving better performance up to an angle of attack 2.8andoV

0g

further a case

ith

inglet cant angle of 60 is giving betterni

performance due to the change in overall flo features and thereen

corresponding drag coefficient variation as discussed in the


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ign

previous session. Fig. 9 sho s the reference plane taken forE

la

generating numerical results for comparison. Figs. 10-17 sho cin

the pressure and velocity contours corresponding to theahce

reference plane sho

n in Fig. 9 at t

o different cant anglesMd

and various angles of attack.nae Fig. 6 Comparison of lift coefficient (CL) at different angles of attack

In the parametric analytical studies NACA series of airfoilsca ithout and ith inglet at four different cant angles

are selected. Basic design of the inglet is selected from thepsor

literature and flo features of the entire ing including the tipeA,

effects have been examined ith different cant angles varying

x 0 0 0e

from 15 to 60 at different angles of attack up to 14 . We havednIe

observed, among the cases considered in this study that a casec

0n

ith 15 cant angle the aerodynamics performance of the

eic

0S

subsonic aircraft during takeoff

as found better up to 2.8lan


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angles of attack and further its performance got diminished atoita

higher angles of attack. Analyses further revealed thatnr

0 0e

increasing the

inglet cant angle from 15 to 60 at highertnI

angles of attack could negate the performance deterioration

and additionally it could enhance the peak value of C /C on

L D

the order of 3.5 %. A

inglet's main purpose is to improve

performance by reducing drag. To understand how this is

done, it is first necessary to understand the distinction betweenFig. 7 Comparison of drag coefficient (CD) at different angles of

attack without and with winglet at four different cant anglesprofile drag and induced drag. Profile drags is a consequence

of the viscosity, or stickiness, of the air moving along the

surface of the airfoil, as well as due to pressure drag (pressure

forces acting over the front of a body not being balanced by

those acting over its rear). As a wing moves through viscous


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aiir, it pulls somme of the air along with it,, and leaves ssome ofthhis air in motioon. Clearly, it takes energy to set air in mmotion.

0

(d) Anglee of attack = 6

Fig. 9 The selected refereence plane for reesults generatioon

46000001

/noitacilbuP/

gro.tesaw

4

102

,21


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:o

0N

(e) Anglee of attack = 8, 0

8 (a) Anglee of attack = 0:

00l

Fig. 10 (a)-(ee) Pressure conttours (Pascal) aat cant angle 15 atoVg

symmmetry plane withh different anglees of attacknir

een

ignE

lacinahc

eM

dna

ecapso

re

A

,x


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ed

n

I00

e (b) Anglee of attack = 20

c(a) Anglee of attack = 0

neic

S

lanoi

tanretnI

0(c) Anglee of attack = 4

0

(b) Anglee of attack = 2


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00

(c) Anglee of attack = 4(b) Anglee of attack = 2

4600

0001/noitacil

buP/gro.tesaw

410

2

,


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21 00: (d) Anglee of attack = 6

oN

0

,(c) Anglee of attack = 4

8:lo

V

gniree

nignE

lacinah

ceM

dna

ecaps

ore

Ax, (e) Anglee of attack = 80

0e

(d) Anglee of attack = 6d


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n 0I Fig. 11 (a)-(e) Pressure conntours (Pascal) aat cant angle 155 at

ec refereence plane withh different anglees of attackneicS

lanoitanretnI

0

(e) Anglee of attack = 8

00

Fig. 12 (a)-(ee) Pressure conttours (Pascal) aat cant angle 60at

(a) Anglee of attack = 00symmmetry plane withh different anglees of attack

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(a) Anglee of attack = 000

(e) Anglee of attack = 8

004

Fig. 13 (a)-(ee) Pressure conttours (Pascal) aat cant angle 60 at60

refereence plane with different anglees of attack

000

01/noitac

ilbuP/gro.tes

aw

4102

,2


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1

:oN, (b) Anglee of attack = 2008:loV

g0

n(a) Anglee of attack = 0

ire

enig

nE

lacinahceM

dna

ecapsore

A

,

x

ed (c) Anglee of attack = 40


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nI

e

cn

0e

(b) Anglee of attack = 2icS

lanoitan

retnI


0

(c) Anglee of attack = 4

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(d) Angle of attack = 600

(c) Angle of attack = 4

460000

01/noitacilbu

P/gro.tesaw

4

1

0

2

, 021 (e) Angle of attack = 8


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nI

eFig. 15 (a)-(e) Velocity contours (meters per second) at cant angl

ec (a) Angle of attack = 00

0n

15 at reference plane with different angles of attackeicS

lanoitan

retnI

0(b) Angle of attack = 20

(a) Angle of attack = 0


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00(b) Anglee of attack = 2

0

(a) Anglee of attack = 0

460000

01/noitacilbu

P/gro.tesaw

4

102

,2 01 (c) Anglee of attack = 4


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:oN

0,

(b) Anglee of attack = 28:lo

V

gnireenig

nE

lacinahceM

dna

ecap

so

re

A

, 00x (d) Anglee of attack = 6

0e


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(c) Anglee of attack = 4dnI

ecneicS

lanoitanre

tnI

0(e) Anglee of attack = 8

0Fig. 16 (a)-(e) VVelocity contouurs (meters per second) at cantt angle


060 at syymmetry plane wwith different aangles of attack


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:o

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sIndustrial annd Commerciall Applications of

Smart Sttructuresor coould give bettter performaance during ttakeoff and landing.e

Technologies, Proceedings of SSPIE Vol. 5388, International Society forA

, WWinglet cant anngle optimizaation needs too be carried oout caseOptical Engineeering, Bellinghaam, WA, 2004, ppp. 213±224.

xe

[200] Sanders, B., EEastep, F. E., annd Forster, E., ªªAerodynamic annd Aero-d byy case. The sstructural techhnologies avaiilable to achieve the n

elastic Characcteristics of Wings with Conformmal Control Surffaces forI

e shhape and/or caant angle chaanges in a moorphing aircraaft is anMorphing Aircraft,º Journal off Aircraft, Vol. 400, No. 1,Jan.±Feeb. 2003,cne arrea that is tto be addresssed separatelly for meetiingthe pp. 94±99.

icS obbjective of thhe variable-ccant-angle wiinglets for ppractical

[211] Raymer, D. P., Aircraft Deesign: A Conceeptual Approach, AIAAl

a Education Series, AIAA, Restoon, VA, 2006, p. 5506.n appplications. WWe concludedd that the investigated conncept ofo

[222] Bae, J. S., Seigler, T. M., andd Inman, D. J.,ªªAerodynamic annd Staticita vaariable-cant-anngle wingletts appears tto be a proomising Aero-elastic Characteristics oof a Variable-SSpanMorphing Wing,ºnr

eJournal of Airccraft, Vol. 42, Noo. 2, 2005, pp. 5228±534.

t allternative forr improving the aerodynnamic efficienncyof

nI

[233] A.E. Von Dooenhoff, ªInvestiigation of the bboundary layer about a

aiircraft.


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symmetrical aairfoil in a winnd tunnel of lo

w turbulenceº, Langley

Memorial Aerronautical Laboraatory, W.R. No. LL.507, NACA, 1940.

ACKNOOWLEDGMENT[244] Henry, J. J., BBlondeau, J. E., and Pines, D. J

., ªStability Anaalysis for

UAVs with a Variable Aspecct Ratio Wing,º AAIAA Paper 20005-2044,

The authors would like tto thank the JJoint Correspondent,April 2005.

Shhankar Vanavvarayar of Kummaraguru Colllege of Technnology,[255] Phil Croucherr, Jar Professioonal Pilot Studiees.

Electrocutionn. 2005,Coimbatore, Inndia for his eextensive suppport of this rresearch

pp. 2±11. ISBNN 978-0-96819288-2-5.

wwork.


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Diagnostic Investigation of Aircraft Performance at Different Winglet Cant Angles