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suvTAarTRa» C©NTF « RESTRICTED REPORT No: AERO. 2165

AT! No HSBS&13S-S3 343003

. ROYAL AIRCRAFT ESTABLIS Farnboroudh. Hants.

^

NT

EFFECT OF A CHORDWISE GAP ON THE TIP STALL OF A SWEPT BACK WING

D. J. KETTLE

, ATTENTION IS CALLED TO THE PENALTIES ATTACHING

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Class No. 533.691.11.001.5

.Report No. Aero.2165 October, 194-6»

ROYAL AIRCRAFT ESTABLISH: iSirr. PASNaOROIEH

The effect of a chordwise gap on the tip stall of a swept back wing.

by

D.J. Xettle

R.A.B.Ref . Aero 148W169 M.O.S.Ref. 3.B.50158/R.D.T.l(c)

SUMMARY

During previous tests on a 12 ft. span model of a tailless glider with 36.4° of sweepback, a preliminary run made over the tiigher ran^e of (V indicated that chordwise gaps £" wide between the variable incidence ">ving tips and the main wing had a considerable stabilizing effect (flaps and elevons 0°).

.-These tests ware made to investigate this effect, more fully.

The gap removes most of the reduction in stability which is due to the tip stall, while having little other effect.

LIST OF CONTENTS

1 2 3 4

Introduction Description of test rig Range of investigations Results 4*1 Presentation of results 4.2 Discussion of results Conclusions References circulation.

r

\

Liar OP AJVBKDICE3

Model data (Soalo 3/3.78) Definitions

App.

II

\

"•**•*- !W ! ,^'Uin.

Report Ho. Aero.2165

LIST (v asa Lift, drag and pitching moment coefficients. Effect of sealing gaps between main v/ing and tips. Variable incidence tips set at 0°. Flips and elevons 0°.

Lift, drag and pitching moment coefficients. Effect cf sealing gaps between main wing and tips. Variable incidence tips set at 0°. Flaps 60° and elevons -10°.

LIST. OF FIGURES

O.A. Tailless wing. 36.4° sweopbaok Pi, vs a , and Cm- vs 0^. The effect of sealing the gaps

between the main wing and variable incidence tips. Flaps and elevons 0°. CT VS a , and Cm- vs Cj. The offset of sealing the gaps

X betveun the main läng and variable incidence tips. Flaps (3 0°, elevons -10°. Op vs C. • The effect of sealing tho gaps betireen the main wing and -variable incidence tips. Flaps and olevons 0°. C_ vs C . Tho offoct of sealing the gaps between the main wing and variable incidence tips. Flaps 60° and elevons -10°.

T*blM

I

Fig.

1

2*3

44 5

6

7

- \

r Report Ho. Aero. 2165

Introduction

During previous traata1 on a 12ft apan modal of a talUoaa glider with 36.4° of aweepback a preliminary run made over the higher range of Or, indicated that chordwiae gap» V* wide between the variable incidence tips und the main wing had a öonaiderable stabilizing effect: (Flapa, elevona and variable incidence tips set at 0°). It was decided to investigate t'.to effect of the gaps over the lover range of 0^, and in addition ever the whole range of 0^ with flaps 60° and elevona -10°'

Thu to'ts wore rrad'-" in the B.A.E. JUly and stojVtjr-1 -sr, ?-9')b-.

2 Deacrir/: Ion uf te&t ri«

24 ft. Wind Tunnel during

Details of tho n.odel (which i£ the same aa that used for the testa | describe'.1 in rcf.l) are given in Appendix I and in fig.l. •

! 3 BSBES °^ investigations

I Lift, drag and pitching moment measurements were made with the

chordwiae gaps sealed and unsealed (flaps and elevons 0°, and flapa 60°, elevona -10u). The variable incidence wing tips were set at 0° throughout. The toats wore made at a constant windapeed of 120 ft./sec. giving a Reynold'a Number of 1.55 * 10° baaed on mean wing chord.

4 Results

4.1 Presentation of results

Definitions of the conventions used are given in Appendix II.

4*2 Discussion of results

Lift ari'l pitching moment curves are given in figs. 2,3, and 4,5 for the tiro ca3es of flues and elevona 0°, and flaps 60° and elevona -10° respectively. The stabilizing effect of the chordwiae gaps found in the oase of tho plain winjp is shown in fig.3 to be present only above a {V of 0.75, below which value the gaps have little effect. With flapa 60** and elevona -10° the gaps have little effect up to the stall, but cause a reduction in 0^ max of C.C4

Values of Cp are plotted against 0^ in i?iga. 6 and 7. On .

remains unaffected by tho presence of the gaps in the two cases tested.

5 Conclusions /

The general conclusions drawn from these tests may be summarized as follows:-

(i) There is a pronounced instability of the wing above a Or of 0.75. which is much improved by opening chordwiae gaps between the main wing and thu variable incidence tips;(flaps and elevona-100).

(ii) With flaps o0° and elevona -10° tho gaps have little effect on the stability below tho stall, but cause a reduction in 0. of 0.04

\

\

•paj

Report No. Aero.2165

LIST OP REFERENCES

l

Author

D.J. Kettle

Title eto.

24ft. Ä'inä Tunnel Tests on the G.A. V wing taille* glidor. Part 1: Lift, drag and pitohing fflomont measurements. A.B.C. 9704 H.A.E. Report No. Aero.2124. March, 194.6.

Attached i 19604S - 19603 Appendices I and II Tables I and II

circulation

N-

C.S. (A ) D.G.S.R.(A) D.3.R.(A) A.D.A.R.D. (Res.) A. D.S.R.Records D.A.R.D. P.D.T.D. R.T.P./T.I.B. D.T.R.D. A.D.R.D.L. 1 A.D.R.D.L.2 General Aircraft Ltd.(per R.T.O.) 2 N.P.L. (Mr.FagQ.Mr.Falkuer) 2 T.A.A.C. (per ii~D.«uR.D. (ROB.)) 25.

1+25 Action Copy

200

2 2

-fs—i«^s=?»c-.t-:-. ••• ••ZZ&tt J

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Hoport No. A«ro.ZL65

Appendix I

Model data (Seile 1/3*73)

WIMB gross area S > 24.60 ft.2

•P*» b » 12.0 ft. mean chord —: V •= 2.05 ft.

• aspect ratio _. A = 5.35 root chord 9B - 3.00 ft tip chord

%% = 0.965 ft.

root section R.A.F.34 tip section 152 B.~.F. 34 dihedral angle Y - 2.9° geometric washout 5° mean 1/4 chord point position

behind L.iä. root ohord 2.408 ft. abova »HM 0.1049 ft.

Elevens- __ _ span (oach) 3.34 ft. area aft of hinge 1.51 ft.2

ohord aft of hinge iOji local chord

«££• type split angle v/hen open span from C/t of aircraft

60° 2.7 ft. ,

area 1.42 ft.2

ohord 20f0 local chord i.e. root 7.20 ins. tip 4*31 ins.

Variable incidence tins; span (each) 30J{ seoispan hinge line on 25$ chord.

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. Report No. Aoro.2165

Appendix II

8B*anb*ok anales measured from cA of aircraft

Tho angle between tht. y axis and tho projection of line .'tC (see f iC«l) on the; xy plMiu.

Dihedral angle • mc-asurod jr. the- 3.rt.-ptb.ck portion only

The angle bofr./oen thp y axis ;ind tho projection of tho line BC (see fig.l) on thu yz piano.

A,B and c ore sectional 1/4 chord joints. (The xyz axes aro defined as in till 3 £ ?''3; for thoao models tho x axis is token to bo parallel to tho r:ot chord).

Moan omxrtcr chord Koint:

Tho position of the moan quarter ohord point is dofinod as x, z, whoro

+b

/ ox djr- Z m

-b 7

l +b S

os dy+ S

-b 2

where S =

+b

/ ody a gross wing area.

-b

Elevon angle

n ; positive v/hon elevon is deflected downwards; measured as the angle botwoun the. olcvon chord normal to the hinge line and tho xy plane.

Variable incidence wing tip anglo

The angle of the variable incidence wing tip is defined as positive when the trailing edgu of tho tip moves downwards.

Tho vcluos of a have been corrected for tunnel constraint.

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Report No. Aero.2165

Jfift. drag and pitching moment oooffiolont«

Bffoct of sealing gaps betv.-een main v/ins and tips* Variable incidence tips set at 0 .

?laps 0° Elevons 0°

Gap unsealed Gap sealed

0 a °L CD c a0 °L CD Crag

4"

- 0.43 -0.063 0.033 +0.025 + 0.53 +0.007 0.031 +0.018 + 1.60 • +0.078- 0.030 +0.015 + 3.64 +0.239 0.035 +0.003 + 4.23 +0.261- 0.033 +0.001- + 6.27 +0.418 0.038 -0.009 • 6.46 • +0.446- 0.041 -0.010- + 8.41 +0.567 0.047 -0.019 * 9.00 +0.596 0.051 -0.017 +11.24 +0.745 O.O64 -0.027 +11.45 • +0.743 O.O65 -0.027- +13.19 +0.365 0.080 -0.021 +13.88 +0.898- 0.091 -0.030 +14.00 +0.947 0.037 -0.016 +15.65 +C.980 0.110 -0.032- +15.60 +1.030 0.112 +0.001 +16.10 - +1.062 0.124 -O.O24 +17.60 +1.110 0.14C +0.025 +18.30 +1.169 0.159 -0.021 +19.80 +1.194 0.165 +0.040 +20.50 +I.267- 0.202 -0.G20- +21.60 +1.267 0.230 +0.052 +22.70 +1.317 0.i:47 -0.013 +23.90 +1.305 0.281 +0.075 +23.70 +1.320 0.258 -0.010 +26.10 +1.315 0.335 +0.081 +25.20 +1.336 0.299 +0.001 +28.30 +1.306 0.389 +0.085 +27.10 +1.371 0.353 -0.007 +30.00 +1.3IB 0.439 +O.O9I +29.60 +1-339 0.421 -0.019 1

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m^m VL. ,...•..» .->!

Report No. Aero 2165

TABLE II

Iflff. drag and pitching moment coefficients

Bffact of aealing gaps between main wing and tip«. Variable incidence tips set at 0 .

Flaps 60° , Elevons -10°

Gap Unsealed Gap sealed

<x° °L °D a° °L % % 4

- 1*46 + 0.77 + 3.40 + 5.85 + 8.57 +10.93 +13.18 +14.16 +16.52 +18.68 +20.38 +22.17

0.252 0.412 0.588 0.728 0.917 1.035 1.160 1.213 1.311 1.145 1.151 1.157

0.144 0.145 0.149 0.157 0.170 0.188 0.213 0.228 0.260 0.302 0.331 0.358

0.114 0.102 0.037' 0.074 0.053 0.041' 0.025

0.019 0,052 0.054 0.054

- 0.49 + 2.43 + 5.35 + 3.28 +11.21 +14.14 +17.10 +19.18 +21.19 +23.1?

0.313 0.507 0.705 0.904' 1.081 I.246 1.366 1.144 1.136 1.148.

0.146 0.148 0.152 0.161 0.175 0.196

. 0.235 0.308 0.^36 0.378

0.117 0.095 0.078 0.056 0.034 0.019 0.027 0.091 0.104 0.107

\

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-ji ,. ,w ,.i.^f

, -W~

No BGQ4.5

REPORT AERO 2)65.

FIG. |.

% OF MODEL

HINGE LINE: or V.l. TIP. 25% CHORD LINE.

SCALE- 12.

\

G.A. TAILLESS WING.

36-4* SWEEPBACK.

S> •

mä

\z

06

0-4)

02

REPORT AERO 2)65

FIG. 2 £3.

» GAP SCALED.

• GAP UNSEALED.

«3 o

1 . im

-oos

0 "^><o 50 " 0" M to f c •• is rJ i-S

FIG. i CMJ VS CL

THE EFFECT OF SEALING THE GAPS BETWEEN THE MAIN WING AND VARIABLE INCIDENCE TIPS.

FLAPS AND ELEVONS 0° •• g • , '"•—T=

NO....J86Q6.S

••4

REPORT AERO »65.

FIG.465.

"TO 5*5 friTT Fo FIG.5. c^|vsCL *

THE EFFECT OF SEALING GAPS BETWEEN THE MAIN WING AND VARIABLE INCIDENCE

TIPS. FLAPS 6O0 ELEVONS -IO* —//-

IA—»

.Ö&Q7.S

045

REPORT AERO 2SS

FIG 6.

TP5Ö" OTS cu l0 l2S IS0

C0vs CL

THE EFFECT OF SEALING THE GAPS BETWEEN THE MAIN WING AND V.l. TIPS.

FLAPS AND ELEVONS O*.

No I9608,S

0 4Si .

005

RCPORT ACftO 365 FIG. 7

Co vs Cj

^rEJZErL°F SEAUNG THE GAPS BETWEEN THE MAIN WING AND VI TIP* FLAPS 6or ELEVONS-IO-

ISO

r RESTRICTED TITLE: Effect of a Chordwise Gap on the Tip Stall of a Swept Back Wing

AUTHOR(S) : Kettle, D. J. ORIG. AGENCY : Royal Aircraft Establishment. Farnborough, Hants PUBLISHED BY : (Same)

ATI-10123 (IVtSION

(None) OCIC. AOIHCT NO.

Aero-2165 PUIUSHtNO AGENCY NO.

(Samel DAT*

Oct ' 46 DOC CUSS.

Restr. COUNTRY

Gt. Brit. LANGUAGE

English FAGIS ILLUSTRATIONS

13 I tables, eraphs. drwgs ABSTRACT:

Investigation was conducted on effect of gaps over the lower whole range of lift coefficients with flaps at 60* and elevons at -10°. Results show pronounced instability of wing above lift coefficient of 0.75 which was much improved by opening chordwise gaps between main wing and variable incidence tips (flaps and elevons at -10°). With flaps at 60° and elevons at -10°, gaps have little effect on stability below stall, but cause reduction in maximum lift coefficient of 0.04.

DISTRIBUTION: Copies of this report obtainable f rn m CAPO. DIVISION: Aerodynamics (2) SECTION: Wines and Airfoils (6)

ATI SHEET NO.: R-2-6-177

SUBJECT HEADINGS: wings - Aerodynamics (99150); Wings • Lift distribution (99170); Wings, Swept-back (99305)

Central Air Document« Office Wrighi-Pertoreen Air Force Bate, Dayton, Ohio

AIR TECHNICAL INDCX

RESTRICTED

TITLE: Effect of a Chordwise Gap on the Tip Stall of a Swept Back Wing

AUTHOR(S) : KetUe, O. J. ORIG. AGENCY : Royal Aircraft Establishment, Farnborough, Hants PUBLISHED BY : (Same)

^ ATI-10123 «VISION

(Nope) ORIS. AOfNOr NO.

Aero-2165 njlllSHlMO AOCNCT NO.

(Same)

Oct' 46 Restr. Gt. Brit. English 13 IUUSTRATTONS

tables, graphs, drwgs ABSTRACT: 10501 dd B 11^3

Investigation was conducted on effect of gaps over the lower whole range of lift coefficients with flaps at 60° and elevons at -10°. Results show pronounced instability of wing above lift coefficient of 0.75 which was much improved by opening chordwise gaps between main wing and variable incidence tips (flaps and elevons at -10°). With flaps at 60° and elevons at -10°, gaps have little effect on stability below stall, but cause reduction in maximum lift coefficient of 0.04.

DISTRIBUTION: Copies of this report obtainable f re P3 CAPO. DIVISION: Aerodynamics (2) SECTION: Wings an(l Airfoils (6)

ATI SHEET NO.: R-2-6-177

SUBJECT HEADINGS: wings - Aerodynamics (99150); Wings Lift distributional 70); Wings, Swept-back (99305)

Central Air Documants Oftlco

Wrigtit-Pattorion Aif ForCO BOM, Dayton. Ohio AIR TECHNICAL INDEX

RESTRICTED