Longitudinal and lateral-directional aerodynamic characteristics … · 2020. 8. 6. · Longitudinal and lateral-directional aerodynamic characteristics were obtained for various

LONGITUDINAL A N D LATERAL-DIRECTIONAL AERODYNAMIC CHARACTERISTICS OF

FOUR TILTING DUCTED FANS ARRANGED I N A DUAL TANDEM CONFIGURATION

A LARGE-SCALE, V/STOL MODEL WITH

by Demo J. Gidiunetti, Jumes C. Biggers, und Ra&h L. Muki T I

Ames Reseurch Center I \

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Moffett Field, CuZ$ .c

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, ' @ ', , C. , .

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TECH LIBRARY KAFB, "l

LCINGITUDINAL AND LATERAL- DIRECTIONAL AERODYNAMIC

CHARACTERISTICS OF A LARGE-SCALE, V/STOL MODEL

WITH FOUR TILTING DUCTED FANS ARRANGED IN A

DUAL TANDEM CONFIGURATION

By Demo J. Giulianett i , J a m e s C. B igge r s , and Ralph L. Maki

A m e s R e s e a r c h Cen te r Moffett F ie ld , Calif.

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

For sale by the Clearinghouse for Federal Scientific and Technical Information Springfield, Virginia 22151 - Price $3.00

LONGITUDINAL AND LATERALDIRECTIONAL AERODYNAMIC

WITH FOUR TILTING DUCTED FANS ARRANGED I N A CHARACTERISTICS OF A LARGE-SCALE, V/STOL MODEL

DUAL TANDEM CONFIGURATION

By Demo J. Giu l iane t t i , James C . Biggers, and Ralph L. Maki A m e s Research Center

SUMMARY

Dif fe ren t ia l fore-af t duct e x i t vane def lect ion and d i f f e r e n t i a l fore-af t t h r u s t were e f fec t ive f o r pitching-moment trim a t t h e low and high duct incidences, respectively. Proper phasing of these controls would be necessary f o r longi tudinal t r i m i n t h e intermediate duct incidence range from 40' t o TO0 where t h e trim requirements reached a maximum. Thrust vectoring by t h e use of d i f f e r e n t i a l fore-aft duct incidence w a s e f fec t ive i n reducing these t r i m requirements .

INTRODUCTION

There has been much recent i n t e r e s t i n t h e use of tandem arrangements of t i l t i n g ducted fans as both propulsive u n i t s and l i f t i n g devices f o r v e r t i c a l and short takeoff and landing (V/STOL) a i r c r a f t . ment would provide an a i r c r a f t with powerful longi tudinal and l a t e r a l - d i rec t iona l cont ro lyespec ia l ly a t low-speed and hovering f l i g h t conditions. Other advantages of ducted fans a r e t h e i r compactness, compared t o the s i z e of f r e e propel lers and ro tors required f o r the same t h r u s t , and the contr ibut ion of shroud l i f t t o t o t a l l i f t a t forward speed. However, a tandem ducted fan arrangement can cause several problems such as duct s ta l l , t r i m changes with changes i n duct incidence a t t r a n s i t i o n forward speeds, aerodynamic i n t e r f e r - ence due t o fore-af t duct placement and la te ra l -d i rec t iona l cross-coupling e f f e c t s a t s i d e s l i p with t h e ducts a t high incidence angles.

Such a ducted fan arrange-

Early small-scale s tud ies of t h i s concept have been reported i n reference 1 where t h e e f f e c t s of duct placement, an a f t wing, and wing t i p s were investigated. I n a l a t e r invest igat ion of a small-scale model with dual tandem ducted fans ( r e f . 2 ) , using duct e x i t vanes as a primary yaw cont ro l i n hover caused cross-coupling e f f e c t s t h a t resu l ted i n adverse r o l l i n g moments. It was a l s o shown t h a t s t a l l on t h e upper outs ide duct surfaces i n t r a n s i t i o n contributed t o poor la te ra l -d i rec t iona l behavior of t h e model, espec ia l ly i n t h e approach speed range. However, it was noted t h a t t h e duct s t a l l character- i s t i c s could be subject t o sca le e f f e c t s . A need f o r invest igat ing basic aerodynamic c h a r a c t e r i s t i c s and performance parameters of fu l l - sca le ducted fans was pointed out i n references 3 and 4 and no known addi t iona l fu l l - sca le information has s ince been obtained; hence such information i s s t i l l scarce.

The present invest igat ion was therefore made of a large-scale, complete model of a t y p i c a l V/STOL a i r c r a f t having four t i l t i n g ducted fans arranged i n tandem p a i r s . General longi tudinal and la te ra l -d i rec t iona l aerodynamic charac- t e r i s t i c s were determined. Performance, s t a b i l i t y , control , and t h e e f f e c t s of duct s t a l l were invest igated through a speed range from hovering t o cruis ing f l i g h t . The e f f e c t s of fuselage angle of a t tack , d i f f e r e n t i a l fore-af t duct incidence and f a n speed s e t t i n g s , d i f f e r e n t i a l fore-af t and l e f t - r i g h t duct e x i t vane def lect ion, and s i d e s l i p were determined. V e r t i c a l - t a i l effect iveness w a s b r i e f l y invest igated.

Tests were conducted a t forward speeds ranging from 0 t o about 94 knots. Duct incidences t e s t e d ranged from 80° on t h e four ducts (near hover configura- t i o n ) t o 5' on t h e f r o n t and 0' on t h e r e a r ducts (c ru ise configuration).

NOTATION

b

C

- C

cD

cL

Cm

Cn

d

D

i

J

span of wing, f t

reference length, wing chord, f t

v e r t i c a l - t a i l mean aerodynamic chord, i n .

D drag coef f ic ien t , - qs

L l i f t coef f ic ien t , - qS

rolling-moment coef f ic ien t , r o l l i n g moment qSb

M pitching-moment coef f ic ien t , - qsc

awing moment qSb

yawing-moment coef f ic ien t , Y

side force qs

side-force coef f ic ien t ,

fan diameter, f t

drag, l b

incidence, deg

v fan advance r a t i o , - nd

L l i f t , l b

M pitching moment , f t - lb

2

moment c e n t e r me

N

n

Y

CL

P

n

6

‘D

‘e

‘a

e

fan r o t a t i o n a l speed, rpm

fan r o t a t i o n a l speed adjusted t o standard sea l e v e l temperature, N

6 0 6 ’ rps

standard atmospheric pressure , 2116 lb/sq f t

tes t - sec t ion s t a t i c pressure, lb/sq f t

free-stream dynamic pressure, lb/sq f t

reference area, area of wing, sq f t

t h r u s t along f a n a x i s , l b

t h r u s t coef f ic ien t , - maximum measured reference s t a t i c t h r u s t of t h e model, 5400 l b

T qs

free-stream veloci ty adjusted t o sea-level, standard conditions, fps or knots

s ide force, lb

fuselage angle of a t tack , deg

s i d e s l i p angle, deg

increment from average value

r e l a t i v e s t a t i c pressure, - PS P O

duct incidence r e l a t i v e t o fuselage, deg

fore-af t duct e x i t vane def lec t ion r e l a t i v e t o fan t h r u s t axis, deg

l e f t - r i g h t duct e x i t vane def lect ion r e l a t i v e t o f a n t h r u s t axis, deg

0 r e l a t i v e temperature r a t i o , ambient temperature (absolute)/460 F

Subscripts

a a f t

f forward

3

2 l e f t

r r igh t

t wing t i p s

U untrimmed

1,2 moment centers 5 percent of t h e dis tance between t h e duct r o t a t i o n points , respect ively, ahead of and behind t h e model moment center located midway between t h e duct ro t a t ion points .

Examples of Duct Incidence and Exit Vane Deflection Notation

0 a l l four ducts a t 40 incidence

?5' fore-af t d i f f e r e n t i a l duct incidence; forward ducts a t

0 6D = 40

6Df/6Da = 35O/45' 35' and a f t ducts a t 45'

0 6ef/6ea = -2Oo/2O0 rtr20 fore-af t d i f f e r e n t i a l duct e x i t vane def lec t ion ( t o t a l of 40' def lec t ion) ; pos i t ive t o t a l def lec t ion when vane t r a i l i n g edges are up on t h e forward vanes and down on t h e rear vanes

0 6a2/6ar = 20°/-20 +20° lef t - r ight d i f f e r e n t i a l duct ex i t vane def lec t ion ( t o t a l of 40 def lec t ion) ; pos i t ive t o t a l def lec t ion when vane t r a i l i n g edges are down on t h e l e f t vanes and up on t h e r igh t vanes

MODEL DESCRIPTION

Photographs of t h e model i n s t a l l e d i n t h e t e s t sect ion of t h e Ames 40- by 80-foot wind tunnel a r e shown i n f igure 1. data are given i n f igu re 2 . Additional per t inent dimensional data of t h e model are given i n t a b l e I.

Model geometry and dimensional

Wing Geometry

Front f a i r ings . - The model had short span f a i r i n g s between t h e fuselage and the f r o n t ducts t h a t housed t h e f ron t duct dr ive sha f t s and trunnion tubes. These f a i r ings had NACA 64A420 sect ions t h a t were modified by removal of t he art lower surface concavity with a s t r a i g h t l i n e from the t r a i l i n g edge tangent t o the lower surface.

0 Wing.- The wing incidence w a s 3 with respect t o t h e fuselage. Aspect r a t i o w a s 2.5 based on wing area with allowances f o r cutouts t o accommodate the rear duct attachments and ro ta t ion . The rear duct ro t a t ion point w a s 1.1 inches above t h e wing chord a t t h a t s t a t i o n . R e a r duct drive sha f t s and

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I II

trunnion tubes were contained i n t h e wing. The a i r f o i l w a s an NACA 64A420 sec- t i o n modified by increasing the chord 19 percent a t t h e t r a i l i n g edge. The modified upper and lower surfaces were s t r a i g h t l i n e s from t h e o r i g i n a l 60 percent chord t o t h e extended t r a i l i n g edge.

Wing t i p s . - Variable incidence wing t i p s having NACA 64A415 sections were located outboard of t h e r e a r ducts. the fan t h r u s t axis and w a s 0' f o r t h i s invest igat ion except f o r b r i e f s tud ies with t h e wing t i p s removed and a t -10' incidence.

Incidence w a s measured with respect t o

Ducted Fans

The ducted fans used i n t h i s invest igat ion a r e described i n reference 3 and a r e the same type as those used i n references 3 and 4, except t h a t t h e blade angle w a s increased t o 23' a t the t i p and t h e i n l e t guide vanes were undeflected. For convenience, t h e shroud and centerbody coordinates from reference 3 a r e l i s t e d i n t a b l e 11.

Duct e x i t vanes.- The duct e x i t vanes a r e described i n t a b l e I: and f i g - ure 2 ( a ) . They were capable of +20° of def lect ion about t h e fan t h r u s t axis. The vanes were mounted with t h e i r leading edges extending i n t o the duct e x i t and were pivoted a t t h e quarter chord l i n e which w a s located 0.75 inch behind t h e duct t r a i l i n g edge.

Fan drive system.- Each p a i r of f r o n t and r e a r ducted fans w a s indepen- dently powered by a 1000 horsepower e l e c t r i c motor mounted i n the fuselage. Motor power w a s t ransmit ted through c e n t r a l t e e gear boxes and appropriate shaf t ing t o transmissions i n t h e fan centerbodies t h a t ro ta ted with t h e ducts. Input power t o the motors was measured on wattmeters.

Simulated Engine Nacelles

Simulated turbojet-engine nacelles were mounted on the wing between t h e fuselage and t h e r e a r ducts. The nacelles were ducted f o r through-cold flow which exi ted a t the bottom r e a r of each nacel le . Details of the nacelles a r e given i n f igure 2 ( b ) .

TESTS AND PROCEDURE

Longitudinal and l a t e r a l - d i r e c t i o n a l aerodynamic charac te r i s t ics were obtained f o r various duct incidences a t forward speeds ranging from 0 t o about 94 knots. Forward speeds were chosen t o represent approximately zero drag a t Oo angle of a t tack , as w e l l as climb and descent conditions, f o r a f ixed duct incidence and f a n speed. The general method of t e s t i n g w a s t o vary fuselage a t t i t u d e while duct incidence, fan speed, and forward speed remained f ixed. Angle of a t t a c k was varied from -8' t o 22' a t s i d e s l i p angles from Oo t o 12O. The method and procedure f o r obtaining i s o l a t e d ducted f a n data were the same as those of reference 2.

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Differen t ia l fore-af t t h r u s t w a s obtained by varying f r o n t duct f a n speed with t h e r e a r duct fan speed constant. Thrust vectoring w a s obtained by d i f - f e r e n t i a l fore-af t s e t t i n g s of duct incidence and e x i t vane def lect ion. Duct incidences t e s t e d ranged from 20' t o 80° on a l l four ducts f o r equal duct inc i - dence s e t t i n g s and from 5' t o 6 5 O on t h e f r o n t ducts and 0' t o 75' on t h e r e a r ducts with 5' and 10' d i f f e r e n t i a l duct incidences. car r ied t o 90' because of problems with rec i rcu la t ing duct e x i t flow. d i f f e r e n t i a l fore-af t and l e f t - r i g h t duct e x i t vane def lect ions t e s t e d ranged from 0' t o 40'. t h e majority of t e s t i n g done a t about 2200 rpm. with t h e wing t i p s and v e r t i c a l t a i l removed.

Duct incidence w a s not Total

Fan speeds were varied from about 1100 t o about 3600 rpm with Limited data were obtained

Duct s t a l l w a s invest igated a t duct incidences of bo, 4 5 O Y 50°, and 60° and w a s indicated by f luc tua t ions i n f ront duct f a n speed with no change i n power input. The procedure f o r s t a l l i n g t h e ducts w a s t o simultaneously decrease f ront and r e a r duct fan speeds i n equal increments u n t i l t h e ducts s t a l l e d and then t o gradually increase t h e f r o n t and r e a r duct fan speeds t o rea t tach t h e flow. No attempt w a s made t o invest igate duct s t a l l a t duct incidences greater than 60° because of t h e low r e l a t i v e crossflow v e l o c i t i e s involved.

C O M CT I ONS

No corrections were applied t o t h e force and moment data t o compensate f o r wind-tunnel w a l l in terference e f f e c t s as t h e magnitude of such correct ions w a s not known. A drag correct ion of 3.4 lb/ lb/sq f t of dynamic pressure w a s estimated and applied t o t h e drag and pitching-moment data t o compensate f o r free-stream e f f e c t s on t h e exposed horizontal model support tube and t h e exposed s t r u t t i p s . This drag correct ion did not account f o r any e f f e c t s of the f ront duct sl ipstream impinging on t h e horizontal model support tube as t h e f r o n t duct incidence was changed.

RESULTS

The s t a t i c t h r u s t of t h e model and t h a t of four i so la ted ducted fans a r e

Longitudinal aerodynamic c h a r a c t e r i s t i c s compared i n f igure 3. I so la ted ducted fan t h r u s t coef f ic ien t as a function of advance r a t i o i s shown on f igure 4. of the model a r e presented i n f igures 5 through 11. Lateral-direct ional aerodynamic charac te r i s t ics of t h e model a r e presented i n f igures 12 through 15. The r e s u l t s of f igures 8 ( d ) , 14(b) , and l > ( e ) were made.dimensionless by divid- ing the absolute forces and moments by t h e m a x i m u m measured model s t a t i c t h r u s t of 5400 pounds ( f i g . 3 ) . Estimated performance of a 6500 pound gross weight a i rplane having t h e same configuration as t h e model investigated i s shown i n f igures 16 through 22. These f igures a r e indexed i n t a b l e I11 f o r convenient reference.

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DISCUSSION

Thrust

The s t a t i c t h r u s t of t h e model and four times t h a t of an i so la ted ducted fan of t h e same type as those i n s t a l l e d on t h e model i s shown i n f igure 3. The r e s u l t s show l i t t l e or no s t a t i c t h r u s t difference between t h e model and the i so la ted ducted fans, ind ica t ing negl igible interference e f f e c t s a t zero forward speed. To a i d i n t h e i n t e r p r e t a t i o n and u s a b i l i t y of t h e t e s t r e s u l t s , i s o l a t e d ducted f a n t h r u s t coef f ic ien t , T,, is shown as a function of advance r a t i o i n f i g u r e 4. The i s o l a t e d ducted fan t h r u s t w a s obtained from measure- ments with s t r a i n gages located on t h e ducted f a n trunnion tube mount.

Longitudinal Aerodynamic Character is t ics

- L i f t . - L i f t coef f ic ien t generally increased with angle of a t t a c k t o high angles of a t t a c k f o r configurations with equal and d i f f e r e n t i a l fore-af t duct incidences ( f i g s . 5 and 6 ) . There were no la rge , sudden losses of l i f t or increases i n drag (duct incidence f i x e d ) , indicat ing no abrupt duct or wing s t a l l . However, var ia t ions of pitching-moment coef f ic ien t f o r these data indicated some degree of flow disturbance a t t h e higher duct incidences a t moderate angles of a t tack .

Longitudinal s t a b i l i t y . - The pitching-moment r e s u l t s of f igures 5 and 6 indicate some var ia t ions i n s t a t i c s t a b i l i t y t h a t o f ten occurred within a s m a l l angle-of-attack range. For duct configurations with pitching-moment curves t h a t remained l i n e a r through portions of an angle-of-attack range, the s t a b i l i t y w a s e i t h e r near ly neut ra l , such as a t t h e c ru ise and near c ru ise duct incidences ( f i g s . 5(a) , ( b ) and 6 ( a ) , ( b ) ) , o r unstable a t t h e higher duct incidences. The s t a t i c s t a b i l i t y f o r t h i s model a t c ru ise conditions w a s l e s s than what would have been expected f o r a moment center midway between p a i r s of f o r e and a f t ducted fans . A fore-af t s h i f t of t h i s moment center of 5 percent of t h e dis tance between duct r o t a t i o n points (mc, and m c 2 , respec- t i v e l y ) resu l ted i n a change i n s t a t i c s t a b i l i t y a t t h e low duct incidence, c ru ise configuration ( f i g . 7 ) . dence. This i s t o be expected since, a t c ru ise conditions, pi tching moment i s la rge ly t h e r e s u l t of aerodynamic forces produced by t h e wing, and changing t h e moment center changes C%. However, .at t h e low forward speeds associated with high duct incidences, t h e wing forces a r e s m a l l or negl igible and pitching moment changes a r e la rge ly t h e d i r e c t r e s u l t of changing t h e moment a r m s t o t h e f r o n t and r e a r ducted fan t h r u s t l i n e s .

This e f f e c t decreased with increased duct inci-

Longitudinal s t a b i l i t y a t low duct incidences i s f u r t h e r a f fec ted by t h e countereffects of t h e sl ipstream dynamic pressure and downwash from t h e f r o n t ducted fans which respect ively increase and decrease CLoL of t h e wing and r e a r ducts.

Longitudinal control.- Longitudinal control for maneuvering and t r i m can be accomplished by t h e use of d i f f e r e n t i a l l y def lected fore-af t duct e x i t

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I

vanes a t low duct incidences (c ru ise conditions) and by d i f f e r e n t i a l fore-af t t h r u s t o r t h r u s t vectoring a t high duct incidences (low forward speed condi- t i o n s ) .

Longitudinal t r i m requirements a t equal and d i f f e r e n t i a l fore-af t duct incidences generally increased with increases i n duct incidence ( f i g s . 5 and 6 ) . ACm, of k 2 O o of d i f f e r e n t i a l fore-af t duct e x i t vane def lec t ion a t CL = 0' remained r e l a t i v e l y constant t o about 60° of duct incidence. A s a r e s u l t , t h e duct e x i t vanes became inadequate as t r i m devices beyond about bo of duct incidence although p i t c h control effect iveness w a s maintained over a s izable angle-of-attack range t o about 60° duct incidence. Hence, t o maintain longi tudinal cont ro l throughout the t r a n s i t i o n duct incidence range, d i f f e r e n t i a l fore-af t t h r u s t could be phased i n a t t h e intermediate duct incidence range of 40° t o 60°. w a s obtained f o r these t e s t s by varying f r o n t duct f a n speed with the r e a r duct fan speed constant. The model c h a r a c t e r i s t i c s f o r these conditions a r e shown i n f igure 8. Variable fan speed ra ther than blade angle changes w a s used t o vary t h r u s t because of t h e greater d i f f i c u l t y involved i n blade angle changes.

The effect iveness , i n terms of

D i f f e r e n t i a l fore-aft t h r u s t

The var iable incidence wing t i p s outboard of t h e r e a r ducts were intended t o function as horizontal s t a b i l i z e r s i n c ru is ing f l i g h t . The wing t i p s had l i t t l e e f f e c t on t h e model c h a r a c t e r i s t i c s a t t h e c r u i s e duct configuration ( f i g . g ( a ) ) , but resu l ted i n reduced pitching-moment coef f ic ien ts over a large angle-of-attack range a t 50' duct incidence f o r a wing t i p incidence of 0' ( f i g . g ( b ) ) . Changing t h e wing t i p incidence t o -10' had l i t t l e e f f e c t on pitching-moment coef f ic ien t both a t the c ru ise duct configuration and a t 50' of duct incidence.

Duct s ta l l . - Duct s t a l l w a s measured a t duct incidences from 40' t o 60'. Incipient duct s t a l l w a s in te rmi t ten t and w a s recognized by f luctuat ions i n fan speed with no change i n input power ( f i g . 10 ) . It w a s not severe and had l i t t l e e f f e c t on t h e model aerodynamic c h a r a c t e r i s t i c s ( f i g . 11); thus it w a s a conservative indicat ion of duct s t a l l . A more meaningful measure of duct s t a l l i n terms of a s t a l l boundary f o r f l i g h t would be based on f a c t o r s found i n duct s ta l ls more severe than encountered i n these t e s t s . They would r e s u l t i n high vibrat ion, high blade s t r e s s e s , and s igni f icant changes i n aerodynamic c h a r a c t e r i s t i c s . Duct s t a l l occurred only on t h e f r o n t ducts suggesting t h a t t h e downwash of t h e f r o n t ducts on t h e r e a r ducts delayed r e a r duct s t a l l . Outer surface duct s t a l l as noted i n reference 2 w a s not encountered i n t h i s invest igat ion. Descent conditions as af fec ted by duct s t a l l a r e discussed with performance.

Lateral-Direct iona l Aerodynamic Character is t ics

Directional s t a b i l i t y . - Directional s t a b i l i t y w a s determined from the model l a t e r a l - d i r e c t i o n a l aerodynamic c h a r a c t e r i s t i c s a t s i d e s l i p presented i n f igure 12. The v e r t i c a l - t a i l volume was s u f f i c i e n t for d i r e c t i o n a l s t a b i l i t y t o high s i d e s l i p angles f o r t h e c ru ise duct configuration; however, t h e model was d i rec t iona l ly unstable a t low s i d e s l i p angles a t 30' and 50' duct incidence ( f i g . 13) . Similar e f f e c t s a r e discussed i n reference 2 where it w a s

8

shown t h a t increasing t h e v e r t i c a l t a i l area made l i t t l e difference i n model d i r e c t i o n a l s t a b i l i t y u n t i l t r a n s i t i o n f l i g h t speeds, corresponding t o 30' duct incidence or l e s s , were reached.

Lateral-direct ional control.- Lateral-direct ional control throughout a t r a n s i t i o n duct angle range would require t h e use of both d i f f e r e n t i a l l e f t - right duct e x i t vane def lect ion and d i f f e r e n t i a l l e f t - r i g h t blade angle changes. Adverse roll and yaw cross-coupling e f f e c t s occurred when d i f fe ren t i - a l l y def lected vanes were used as a roll cont ro l a t low duct incidence (c ru ise conditions) and as a yaw control a t high duct incidence (hover conditions) ( f i g . 14). The roll and yaw control with +20° of d i f f e r e n t i a l l e f t - r i g h t duct e x i t vane def lec t ion a t c ru ise and 80° duct incidences, respectively, w a s main- ta ined over a la rge angle-of-attack range a t 0' and 8' of s i d e s l i p ( f i g s . l 5 ( a ) , l 5 ( b ) , and 15(e) ) . The roll cont ro l a t the c ru ise duct configura t ion w a s accompanied by yaw cross coupling t h a t was favorable a t negative angles of a t t a c k but became adverse a t pos i t ive angles of a t tack ( f i g s . U ( a ) and l 5 ( b ) ) . A s expected, l a rge adverse roll-yaw cross coupling occurred a t t h e intermediate duct incidence of 50° ( f i g s . l 5 ( c ) and l 5 ( d ) ) . Although not t e s t e d , d i f f e r e n t i a l l e f t - r i g h t t h r u s t as a roll control a t high duct incidences would be accompanied by favorable yaw cross coupling. Thus t h e need f o r carefu l phasing of these controls f o r properly separating roll and yaw a t t h e midtransi t ion speeds becomes apparent. H i g h values of C a t high

angles of a t t a c k accompanied by adverse yaw as shown i n f igure 12 indicate t h e tendency f o r Dutch r o l l o s c i l l a t i o n s reported i n reference 2. noted t h a t s i d e s l i p grea t ly changed t h e r o l l cont ro l effectiveness of t h e e x i t vanes with changes i n angle of a t t a c k a t 50° duct incidence ( f i g s . l 5 ( c ) and

l P

It should be

15(d) 1

Transi t ion Performance

General t r a n s i t i o n charac te r i s t ics . - The t e s t r e s u l t s were used t o derive a t r a n s i t i o n from hover t o cruis ing f l i g h t f o r an airplane having t i l t i n g , dual tandem, ducted fans. grammed s e r i e s of changes i n duct incidence and power with changes i n forward speed. The required var ia t ion of duct incidence with forward speed from hover t o c ru ise f l i g h t f o r a 6500 pound gross weight a i rplane having t h i s configura- t i o n is shown i n f igure 16 f o r 0' angle of a t t a c k and pi tching moments trimmed. The power required f o r t h i s t r a n s i t i o n i s shown i n f igure 17. The differences i n forward speed r e s u l t i n g from pitching-moment trim were s m a l l and were neg- l i g i b l e f o r a k5' d i f f e r e n t i a l duct incidence compared t o those f o r equal duct incidence s e t t i n g s . Only r e s u l t s f o r d i f f e r e n t i a l duct incidence s e t t i n g s were avai lable where such s e t t i n g s a r e noted i n f igure 16 a t the higher forward speeds.

Such a t r a n s i t i o n would be accomplished by a pro-

Pitching-moment var ia t ion with duct incidence.- The untrimmed pi tching moments f o r zero cont ro l def lec t ion increased with increases i n duct incidence ~-

and reached a maxi" a t about 60° duct incidence (approximately 45 knots forward speed) ( f i g . 18). resu l ted i n reduced pitching-moment trim requirements. A forward s h i f t of t h e moment center of 5 percent of t h e dis tance between duct r o t a t i o n points (me1)

Fore-aft d i f f e r e n t i a l duct incidence s e t t i n g s of k5'

9

was even more e f f e c t i v e i n reducing t r im requirements than t h e d i f f e r e n t i a l duct incidence s e t t i n g s i n t h e duct incidence range of maximum pi tch ing moments .

Control power var ia t ion with duct incidence.- A d i f f e r e n t i a l duct exit vane s e t t i n g of 220" was ef fec t ive f o r trim t o about 44' of duct incidence - ( f i g . 19) . D i f f e r e n t i a l duct incidence s e t t i n g s of 25O extended t h e u s a b i l i t y of t h i s e x i t vane def lect ion f o r trim t o about 50' of duct incidence (approximately an 8 knot reduction i n forward speed).

Longitudinal trim through t r a n s i t i o n w a s obtained with d i f f e r e n t i a l fore- a f t duct e x i t vane def lec t ion from cru ise t o 40° of duct incidence and with d i f f e r e n t i a l fore-af t t h r u s t a t duct incidences greater than 50'. A differen- t i a l vane def lec t ion of 40° (assumed t o be a l i m i t f o r l i n e a r response) and d i f f e r e n t i a l t h r u s t as l imited by f r o n t duct s t a l l prbvided s u f f i c i e n t cont ro l f o r trim and res idua l control avai lable f o r maneuvering, espec ia l ly i n t h e duct incidence range of 60° t o TO0 where untrimmed pi tching moments were larg- e s t ( f i g . 20). A 25' fore-aft duct incidence d i f f e r e n t i a l and a forward s h i f t of t h e moment center of 5 percent of t h e dis tance between t h e duct r o t a t i o n points resulte-d i n o v e r a l l decreased t r i m requirements and increased t h e mini- mum control power ava i lab le f o r maneuvering which occurred a t about 40° of duct incidence.

Effects of duct s t a l l on performance.- The estimated maximum descent r a t e of t h e airplane would be l imi ted by f r o n t duct s t a l l t o about 600 ft/min a t a duct incidence of about 60° ( f i g . 21). measure of inc ip ien t duct s t a l l w a s obtained, and t h e duct s t a l l w a s not severe and had l i t t l e e f f e c t on t h e model longi tudinal aerodynamic character- i s t i c s . For these reasons it appeared t h a t the maneuvering a b i l i t y of t h e airplane was not ser iously r e s t r i c t e d by f ront duct s t a l l . This is f u r t h e r i l l u s t r a t e d i n f igure 22 where estimated f r o n t and r e a r duct fan speed changes, i n terms of advance r a t i o , required f o r longi tudinal t r im by d i f f e r e n t i a l t h r u s t a r e shown r e l a t i v e t o duct s t a l l boundaries. A s i s shown i n f i g u r e 22, model interference e f f e c t s reduced t h e duct s t a l l boundary of t h i s configura- t i o n over t h a t of t h e i so la ted ducts.

A s was noted e a r l i e r , a conservative

CONCLUSIONS

A longi tudinal trimmed t r a n s i t i o n from hover t o c ru is ing f l i g h t w a s e s t i - mated f o r a 6500 pound gross weight a i rp lane having t i l t i n g , dual tandem ducted fans. Duct incidence and forward speed were var ied t o provide l e v e l , unaccelerated f l i g h t conditions through t h e t r a n s i t i o n .

Untrimmed pi tching moments increased with duct incidence and were a maximum a t about 60° of duct incidence, Longitudinal t r i m through t r a n s i t i o n w a s accomplished with d i f f e r e n t i a l fore-aft duct e x i t vane def lec t ion a t low duct incidences and with d i f f e r e n t i a l fore-aft t h r u s t a t high duct incidences. I n addition, these controls provided res idua l cont ro l avai lable f o r maneuvering especial ly i n t h e duct incidence range of maximum untrimmed pi tching moments.

10

I

Duct stall did not appear to seriously restrict the descent capabilities of the airplane at high duct incidences. Duct stall was encountered on the front ducts only and indicated that front duct downwash effects on the rear ducts delayed rear duct stall.

The model was directionally stable to high sideslip angles at the cruise duct configuration, but was directionally unstable at low sideslip angles at the higher transition duct incidences.

Ames Research Center National Aeronautics and Space Administration

Moffett Field, Calif., Mar. 30, 1966

REFERENCES

1. Newsom, William A., Jr.: Aerodynamic Characteristics of Four-Duct Tandem VTOL-Aircraft Configurations. NASA TN D-1481, 1963.

2. Newsom, William A., Jr.; and Freeman, Delma C., Jr.: Flight Investigation of Stability and Control Characteristics of a 0.18-Scale Model of a Four- Duct Tandem V/STOL Transport. NASA TN D-3035, 1965.

3. Yaggy, Paul F.; and Mort, Kenneth W.: A Wind-Tunnel Investigation of a 4-Foot-Diameter Ducted Fan Mounted on the Tip of a Semispan Wing. TN D-776, 1961

NASA

4. Mort, Kenneth W.; and Yaggy, Paul F.: Aerodynamic Characteristics of a 4-Foot-Diameter Ducted Fan Mounted on the Tip of a Semispan Wing. TN E-1301, 1962.

NASA

11

II l l l l l l l I

TABLE I .. MODEL DIMENSIONAL DATA . . ..

ring Area, sq ft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.30 Chord, f t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.62 Span. f t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.63 Aspect r a t i o . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Taper r a t i o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0 A i r f o i l section:

Max . thickness r a t i o . percent chord . . . . . . . . . . . . . . . . 16.8 Posi t ion of m a x . thickness. percent chord . . . . . . . . . . . . . 33.6

Area f o r one t i p . sq f t . . . . . . . . . . . . . . . . . . . . . . . 5.53 2ing t i p s

Aspect r a t i o . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.4 Taper r a t i o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7 A i r f o i l sec t ion . . . . . . . . . . . . . . . . . . . . . . . . NACA 64A415

Inside diameter. ft . . . . . . . . . . . . . . . . . . . . . . . . . 4.00 Outside diameter. f t . . . . . . . . . . . . . . . . . . . . . . . . 4.87 Exit diameter. f t . . . . . . . . . . . . . . . . . . . . . . . . . . 4.512 Ch0rd.f-L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.75

h c t s

. . . . . . . . . . . . . . . . . . . . . . . . . Diffuser angle. deg 11 Xzct e x i t vanes

Area f o r one vane. sq ft . . . . . . . . . . . . . . . . . . . . . . 10.3 Aspect r a t i o . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 Taper r a t i o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.8 A i r f o i l sec t ion . . . . . . . . . . . . . . . . . . . . . . . NACA 0012-64

Fandiameter. f t . . . . . . . . . . . . . . . . . . . . . . . . . . 4.00 Number of blades 8 Blade angle a t t i p . deg . . . . . . . . . . . . . . . . . . . . . . . 23

Area. s q f t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.7 Aspect r a t i o . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Taper r a t i o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.4 T a i l volume. cu f t . . . . . . . . . . . . . . . . . . . . . . . . . 256

‘an

. . . . . . . . . . . . . . . . . . . . . . . . . . ‘ e r t i c a l t a i l

. . . - _ _ ~~ -

12

I

TABLE 11.- SHROUD AND CENTERBODY COORDINATES

”

Shroud coordinates tabulated i n percent of shroud chord

(33.00 in.) :hor dwi s e length

0 -5 75

1.25 2 -5 5 -0 7.5 10.0

20.0 15 .o

25 .o 30.0 35 -0 40 .O 45 .O 50 .o 55 -0 60.0 65 .o 70 .o

80 .o 85 .o go .o 95 -0 100 .o

75 -0

Ins i d € radius

81.5 79 *6 79 90 78.4 77.2 75 -8 74.9 74.2 73 -3 72 -9 72.7

1 73 92 74.1 75 -1 76.1 77 *1 78.1 79 -1 80.1 81.1 82 .o

2ent erbo dy coordinates Labulated i n percent of

centerbody length (71.

Length

0 -5 1.25 2.50 5 .o 7 95 10 .o 15 .o 20 .o 25 .o 25.875l 30 .o 32 .572

50 .o 60 .o 70 .o 80 .o 83.20 go .o 95 *o 100 .o

40 .O

72 .053

i n . 1 Radius

0 2.07 3.20 4.46 6.17 7.40 8.31 9.68 10.54 11.01 11.06 11.19

10.49 10.14 7-97 6-77 4.03 2.01 0

ige posi t ior ‘Shroud leading- 21nlet guide vane c/4 l i n e posi t ion 3Shroud trail ing-edge pos i t ion

TABU 111.- INDEX TO FIGURES

Lateral-directional aerodvnamic character is t ics

Figure

1 Model photographs 2 Model geometry 3 4

Sta t ic thrust of the four ducted fans Isolated ducted fan thrust coeff ic ient as a function of advance r a t i o

Effects of

5 Q u a l fore-af t duct incidence changes

6 Different ia l fore-aft duct incidence changes

7 Moment center on s t a t i c s t a b i l i t y

8 Variable f ront duct thrust

9

10

11 Duct s t a l l on model character is t ics

Wing t i p s outboard of the rear ducts

Duct s ta l l on input power

Longitudinal aerodynamic character is t ics

30, 60

50, 60, 70, 80

50

40, 45, 50, 60

40, 45, 50, 60

5/0, 15/10> 25/35,

55/65, 65/75 35/45, 45/55,

5/0

5/0

Effects of

12 Sideslip

13 Sideslip with the ver t ica l t a i l instal led and removed

14 Different ia l l e f t - r igh t duct exit vane deflection

15 Different ia l l e f t - r igh t duct ex i t vane deflection a t s ides l ip

21 22

80

50, 80

Performar

5/0

5/0

5/0

a, de8

var.

V a r .

var.

0

var.

0

0

$ 9

deg

0

0

0

0

0

0

0

P 9

6 %

0, -2, -4, - 6 , -a, -12

var .

0

0, -8

Duct incidence required for t ransi t ion from hover t o cruise f l i g h t ; pitching moment trimmed Power required f o r t ransi t ion from hover to cruise f l igh t ; pitching moment trimmed Pitching moment variations with duct incidence changes a t unaccelerated f l i g h t conditions Different ia l fore-af t ex i t vane deflection required for trim Longitudinal t r i m requirements and pitching moment available a t unaccelerated f l i g h t conditions Descent veloci t ies as affected by duct stall ; pitching moment trimmed Duct s ta l l margins

6ef/6ea>

0, -20120

0, -20120

deg

0

0

0, -20/20

0, -20/20

0, -20/20

6a2/6ar deg

_ _

0

0

var .

0, 20/20

14

( a ) Hover duct configuration; SD = go0, 6ef/6ea = Oo/Oo.

Figure 1.- Model mounted in test section of Ames 40- by &)-foot wind tunnel.

A-33527

A-33529

( b ) Transit ion duct configuration; S, = 45', 8ef/8ea. = -2Oo/2O0.

Figure 1. - Continued.

16

A-33530

( e ) Cruise duct configuration; FDf/ka = 5 O / O o , 6ef/6ea = Oo/Oo.

Figure 1.- Concluded.

17

I-' a3

Al l dimensions in irches

(a) Geometric characteristics of t he model.

Figure 2.- Model dimensions and geometry.

,Fillet level /Wing contour

Flat , variable chord plane

A- ! --- R

R A

/ \ I

I

Profile at B-B

Section at A-A

(b) Details of simulated engine nacelles.

Figure 2. - Concluaea.

700C

600C

500C

4000 e mi

I- 3000 \

2000

1000

0

I I I 6 D ~ deg

0 Isolated ducts 0 80 Complete mode

30 70 Complete mode

I

400 800 1200 1600 2000 2400 2800 3200 3600 4000

N / 4 I rpm

7000

6000

5000

n 4000 - I

m \

I- 3000

/

0 2 4 6 8 14 16 IO 12 (N/&)*, rpm2

17 18 x IO6

Figure 3.- Thrust a t zero forward speed; blade angle = 2 3 O , a = Oo, 6ef/6ea = oO/OO.

20

5.2

4.8

4.4

4.0

3.6

3.2

2.8

Tc 2.4

2.0

I .6

I .2

.8

.4

0

0

8 D, ' I deg

I

\

\ Y \

\ Y \

.I .2 .3 .4 .5 .6 .7 .8 .9 1.0 1 . 1 J

Figure 4.- Thrust coef f ic ien t as a funct ion of advance r a t i o f o r the i s o l a t e d ducted fan; blade angle = 23'.

21

8

7

6

5

4 CL

3

2

I

- -.8 -9 0 .4 .8 1.2 1.6

Figure 3 . - Longitudinal aerodynamic characteristics of the model with equal fore-aft duct incidence settings; p = oO.

IO 7

7-

6 c cL 5k 4F 3

I

0 1 -6 -4

I I 1

-2 CD

0 2 - 8

0 0 0 0 0 0 + -20120 A 0

1- -4

.38

.56 .63 .64 .75

f

33 49 55

0 4 Q l deg

8 12 16

32

28

24

20

16

-0 12 .. U

8

4

0

-4

-8

[u w

Cm

Figure 5 . - Continued.

9

8

7

6

5

4 CL

3

24

1 2

--I, -02 -I 0 I 2

C D

Sef/ae., deg J V, knots - 0 0 .45 39

0 0 .52 53 0 0 .52 45

-20120 .52 45 - -

n 0 .57 49

-8 -4 0 4 8 12 16 QI, deg

16

12

8

4

0

-4

-*2 -4- I 0 -I

cnl

( e ) SD = 40'


IO

CL

8

6

4

2

2 0 -6 -4 -2 0

CD -8 -4 0 4 8 12 16

a, deg

28

24

20

16

12

8

4

0

-4

-8

I I I

6,J8ea, deg J V, knots -0 0 .27 24 - 0 0 .40 48 0 0 .40 35

n 0 .48 42 -+ -20/20 .41 35 -


16

14

12

10

8

0 .31 27 .32 27 - .35 30

W -20/20 .35 31 0 0 .40 34

-

~A-. A 0 .48 42

-8 -4 0 4 a 12 16 20 24 6 4 2 0 -8-

a, deg

( e ) S, = 60°


'7 30

26

24

CL 22

20

Sef/Sea, deg J V, knots - 0 0 .22 22

-4 0 4 8 12 W

CD

16 24


32v-- 28 V, knots J

I-- 44 --Id- I I

oL----1-------- -8 -4 0 4 8 12 16 20

CD

0 18 .I4 0 17 .20 ae,/sea = OYO"

0

( g ) SD = 80'

Figure 3 . - Concluded.

5-7----- 4

3

2

CL I

0

-I

L

-$ -.2 0 .2 .4 .6 .8 CD

0 -20120 .80 70

-8 -4 0 4 8 12 16 20 .4 0 -.4 -.8 -1.2 a, deg Cm

( a ) Cruise duct configuration.

Figure 6. - Longitudinal aerodynamic character is t ics of t he model with d i f fe ren t ia l fore-aft duct incidence sett ings; P = 0'.

w 0

9

a

7

6

5

C L 4

3

-- 2

- I -I 0 I 2 3

CD a , deg

( b ) Transit ion duct configurations.


0 8

c 1 4

a -0

aDf/aDa,deg 0 deg J V, knots

0 .23 20 0 65/75 0 55/65 0 .31 26 -I 55/65

8 -

4 -20120 .31 26 - -4

I I 1 I -8 6 8 IO -8 -4 0 4 8 12 16

0 - 2 0 2 4

CD a 1 deg

( e) Near-hover duct configurations.

Figure 6. - Concluded.

W [u

6 ~ , / 6 ~ ~ = 5 " / 0 ~ , J z.92

20

16 I 1 /

17- 1

12 -j- / / I

I cn g 8 ,. It U

4

0 i

1'

A

I

-4 -7 -8

.8 .4 0 -4 -.8 C m

I .2 .8 .4 0 -.4 -. 8 Cm

6 4 2 0 Cm

Figure 7.- S t a t i c s t a b i l i t y of the model for a l te rna te moment centers a t several duct incidences; p = oO, 6ef/6ea = Oo/Oo.

I

I

12

10

CL a

6

d

.8

4

0

-4 CD

-.8

-1.2

-1.6

-2.0

8

6

4

ClTl

2

C

-2 )

.3 .4 .5 .6 -7 .8 .9 1.0 Jfront ducts

Figure 8.- Effect of variable front duct thrust on the longitudinal aerodynamic characteristics of the model with the rear duct thrust constant; a = Oo7 /3 = Oo7 6ef/6ea = Qo/Oo.

33

.5 Jfront ducts

34

--- -I 1 1 1 1 . 1 1 . - 1 1 1 1 11111111111.111 1 1 1 1 1 1 1

2

I

cD 0

- I

-2

'0 .I .2 .3 .4 Jfront ducts

35

.8

.6

Lift .4 - TS

.2

0

.4

.2 Pitching moment

0 TSXC +-

800 1200 1600 2000 2400 2800 3200 3600 4000 -. 2

0 Front duct fan speed, N/&, rpm

(a) S, = 80°, V = 0 knots


0 .4 .8 L

18 -.4 C D

0 -10 -20/20 .82

tl off -20/20 .82

-8 -4 0 4 8 12 16 Q , deg

( a ) kf/8j-ja. = 5O/Oo, V = 70 knots

Figure 9.- Effect on the model longitudinal aerodynamic charac te r i s t ics of wing t i p s outboard of the rear ducts; /3 = 0'.

IO

9

8

7

6

CL 5

-- --r- --

-- CD

X D - l -- Ill- ii- 0 -10 0

0 off 0 -20120 -- . A - I O

f

Figure 9 . - Concluded.

140

I20

100 Q r - L

80 Q

0 c

60 + c

LL 2

40

20

0

140

I20

100

5 80 Q L

0 Q

0 c

60 c c

LL 2

40

20

0

Symbols

Open - Decreasing fan speed Flagged - Increasing fan speed

Solid - Intermittent duct stall

v 44 knots

I I .2 4 .6 -8 1.0

Jfront ducts

6, 50" V = 35 knots

V = 27 knots , 0 .2 .4 .6 .8

Jfront d u c t s

Figure 10.- Variation of input power with f ront duct f an speed showing f ron t duct stall ; a = oO, p = oO, 6ef/Eea = Oo/oO.

39

I

6

5

4

CL 3

2

I

0

1.2

.a CD

.4

0

-.4

Symbols Open - Decreasing fan speed

- Solid - Duct stall

+ I I I I

1.2

.8

cnl .4

0 v.4 .5 .6 .7 .8 .9 Jfront ducts

(a) SD = 40°, V = 44 knots

Figure 11.- Effect of front duct stall on the model longitudinal aerodynamic characteristics. Front and rear duct fan speeds varied simultaneously until front ducts stalled; CL = Oo, p = Oo, 6ef/6ea = Oo/Oo.

40

6

5

4

CL 3

2

I

0

I .6

1.2

CD .8

.4

0

I .2

.8

crn

.4

0

I

p, . .

I

f Symbols

- Decreasing fan speed Flagged- Increasing fan speed Solid - Intermittent duct stall

- Open

.4 .5 .6 .7 .8 .9 I .o Jfront ducts

( b ) = 45O, V = 44 knots

Figure 11.- Continued.

41

8

7

6

CL 5

4

7

0

. .. ~.

Symbols - Decreasing fan speed

Flagged- Increasing fan speed Solid - Intermittent duct stall

- Open

1.6

.4

0 .I .2 .3 .4 .5 .6 .7 Jf ront ducts

( c ) = 50°, V = 35 knots

Figure 11.- Continued.

42

13

12

I I

IO

CL 9

8

7

6

\

0

3

2

CD I

0

4

3

c m 2

I ur

0

Sy m bok Open - Decreasing fan speed

- Flagged- Increasing fan speed Solid - Intermittent duct stall L

.I

'

\

.2 .3 .4 .5 .6 -7 Jfront ducts

(d) 81) = 60°, V = 27 knots


43

CY

4 8 12 16 20 24 .. - -8 -4 0

a, deg

(a) 6 ~ ~ / 6 ~ ~ = 5 O / O o , J = 0.94, V = 80 knots

Figure 12.- Lateral-directional aerodynamic characteristics of the model at sideslip; 6a-J6ar = Oo/Oo.

44

.5

.4

.3

C2 .2

. I

0

.04

0

C" -.04

4 8 12 16 20 -.O 8 -8 -4 0

a, deg

( b ) 6~ = 30°, J = 0.64, V = 55 knots

Figure 12 - - Continued.

45

C Y

.08

.04

0

C” -.04

-.08

-.I2 -8 -4 0 4 8 12 16

Q, deg

( c ) SD = 50°, J = 0.40, V = 33 knots


46

.I6

.I 2

.08

Cn .04'

I

I 0

-.04

-. 08

.I 6

.I 2

-08

Cn .04!

0'

-.04,

-.08

- 0 3 0 .64 8o 55 I 0 5 / 0 .94

0 50 .40 3 5

Figure 1 3 . - V e r t i c a l - t a i l contribution t o d i r e c t i o n a l s t a b i l i t y ; 6a2/6ar = oo/oo.

47

111111111111111.11 111 111l.111. I ,I I..I.III.I, 111111.11 111 I I .,,.,.-

'IO 51- 5 151-15 201- 20

(a) 6Df/8Da = 3O/Oo, J = 0.93, v = 80 knots

Figure 14.- Effect of differential left-right duct exit vane deflection on the model lateral-directional aerodynamic characteristics; a = Oo, p = 00.

Yawing moment Ts x b

.04

Rolling moment 0 .

71 t-1

Ts x b 0 C)

-.04

7

0

I I I ~~ - .04 ' I

( b ) = 80°, V = 0, N = 2190 r p m


49

I 111 I ll 1 1 1 1 1 1 1 1 -I-

.08

-04 0 201-20 .95

CY

0

-.O 4

-8 -4 0 4 8 12 . I

Q ,deg

( a )

Figure 13. - Lateral-d

16 20

r ec t iona l aerodynamic cha rac t e r i s t i c s f the model with the duct e x i t vanes undeflected and d i f f e r e n t i a l l y def lected l e f t and r i g h t .

50

C Y

0

[

-.04

C" -.O 8

-.I 2

Ct

b

.4

.3

.2

0 -8 -4 0 4 8 12 16 20

a, deg

(b) %If/%, = 50/0°, V = 80 knots, p = - 8 O


4 8 12 16 a, deg

( c ) % = 50°, v = 35 knots, p = o0


I

CY

.2

0

C" -. 2

-.4

-.61

.7

I .6

.5

.4

Cl .3

.2

. I

7

I l l 0 -8 -4 0 4 8 12 16

(a) = 50°, V = 35 knots, J = 0.41, p = -8'


53

*02 0 L- Yawing moment

-.04

?- Rolling moment

-.o I

-.02 - 12 0 4 a -12 -8 -4

a deg

(e) = 8oo, v = 0 , P = Oo, N = 2168 rpm, 6a2/6ar = 2oo/-2o0


54

cn W -0

0 C 0

n

0

\ \ \

\

I 43

I

\ \ \

I

I

\

\ \ I

~

I

\

I

I

80 I20 I60 200 240 280 320 V, knots

Figure 16.- Duct incidence required for transition from hover to cruising flight at level, unaccelerated flight conditions; pitching moments trimmed, lift = 6500 lb, a = 0'.

55

1600

I200

hp 800 I

400

0 20 40 60 80 100 I20 140 V, knots

Figure 17.- Power required f o r t r a n s i t i o n from hover t o cruising f l i g h t at level , unaccelerated f l i g h t conditions; pitching moments trimmed, l i f t = 6500 lb, CL = 0'.

Model mc

9

Duct 40

angle, so, deg 50 60 70

Figure 18. - Variation of pitching moment with duct incidence a t level, unaccelerated t r ans i t i on f l i g h t conditions; l i f t = 6500 l b , a = 0'.

Figure 19.

I IO 20 30 40 50 60

210 0

Duct angle, So, deg

Differen t ia l fore-af t duct e x i t vane deflection required for longitudinal t r i m a t level , unaccelerated t r a n s i t i o n f l i g h t conditions; l i f t = 6500 lb, CL = 0'.

-24,000

-20,000

-16,000

A2 c Y-

,. - I2,OOO + c a)

k 0

L 0 .E -8000 c ._ a

-4000

Available

0

I I I h I / /

E 4000

0 IO 20 30 40 50 60 70 Duct angle, 6,, deg

Figure 20.- Longitudinal t r i m requirements and ava i lab le longitudinal control with d i f f e r e n t i a l f o r e - a f t duct e x i t vane and t h r u s t s e t t i n g s a t leve l , unaccelerated t r a n s i t i o n f l i g h t conditions; l i f t = 6500 lb, CL = Oo.

59

m 0

60

50

40

30

20

0 +O 50 60 70 80 90 100 110 120 2

V, knots

Figure 21.- Maximum descent ve loc i t i e s as l imited by f ront duct s t a l l ; pitching moments trimned, l i f t = 6300 l b , CL = 0'.

0, 0)

ZI 60 A a

0)

cp C 0

- - -

n w “u 3 40 n with differential fore-aft thurst

Longitudinal t r im in transition

- -

exit vane deflect ion 20

- -

I I I I I I I I I

Figure 22.- Estimated duct stall margins at level, unaccelerated transition flight conditions; lift = 6500 lb, a, = 0’.

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Longitudinal and lateral-directional aerodynamic characteristics … · 2020. 8. 6. · Longitudinal and lateral-directional aerodynamic characteristics were obtained for various