Hybrid upper surface blown flap propulsive-lift concept for the quiet short-haul research aircraft

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NASA TECHNICAL

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r -OP r f FLAF AI,rw4 X (4A5A) Al"_'L AFT Sli0f 1-HAUL QUIFT Uncl^:^ csCL 01C p 53.25 NC 1 n 35825 (:3/C5 HYBRID UPPER SURFACE BLOWN FLAP PROPULSIVF - LIFT CONCEPT FOR THE QUIET SHORT - HAUL RESEARCH AIRCRAFT John A. Cochrane, and Robert J. Carros Ames Research Center Moffett Field. California 94035 T September 1975 dJ^ .

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I , Report No. 2. Government Accession No, 3, Recipient's Catalog No, Tr y x-6z 477 Title end Subtitle 1, 6, Report Date HYBRID UPPER SURFACE BLOWN F 4,AP PROPULSIVE-LIFT s, Performing organisation Cade CONCEPT FOR THE QUIET SHORT-HAUL RESEARCH AIRCRAFT 7, Author(s) 0. Performing Organization Report No.

John A. Cochrane and A-6224 Robert J. Ca'rros 10. Work Unit No.

Performing Oryenintion Name and Address 769-02-02 g.

NASA Ames Research Center 11. Contact or Grant No, Moffett Field, Calif. 94035 13. Type of Report and Period Covered 12, Sponsoring Agency Name and Addrou Technical Memorandum National Aeronautics and Space Administration Sponsoring Agency Coda n, 20546 Washington, D. C.

— 16. Supplementery Not" 1e. Abstract, The hybrid upper surface blowing concept consists of wing-mounted turbofa engines with a major portion of the fan exhaust directed over the wing upper surface to provide high levels of propulsive lift,'but with a portion of the fan airflow directed over selected portions of the airframe to provide boundary layer control. NASA-sponsored preliminary design studies identified the hybrid upper surface blowing concept as the best propulsive lift concept to be applied to the Quiet Short-Haul Research Aircraft (QSRA) that is planned as a flight facility to conduct flight research at low noise levels high approach lift coefficients, and steep approaches. Data from NASA in-house and NASA-sponsored small and large-scale wind tunnel tests of various configurations using this conept are presented.

1e. Distribution Statement 17, Key Wade ISuggasted by Author(s)) Aeronautics Unclassified - Unlimited Aerodynamics Aircraft design i control Aircraft stabiltiy 3 STAR Categories 01, 02, 05, 08 - 21. No, of Pages 1 22. Rice 20. Security Clarif. (of this page) 19, Security Clam}. lof this report) $3.25 Unclassified Unclassified 10 "For sale by the National Technical Information Service, Springfield, Virg

IIYURID UPPER SURFACE BLOWN FLAP PROPULSIVE-LIFT CONCLPT FOR THE QUIET SIIORT HAUL RESEARCH AIRCRAFT John A Cochrane* and Robert J. Curros* Ames Rescarch Center, NASA, Moffett Plaid ^'Xifnrnla 94035 Introduction Abstract lady sitAles of low cost propulsive-lift research aircraft led The hybrid upper surfuee biowing concept consists of wing- to bile conceal critic hybrid uppursurface blowingsyslcnl. In mounted turbofan engines with a junior portion of file fan exhaust Mils concept, the major portion of file turborun exhaust air Is directed over the wing upper surface to provide high levels of blown over the upper surface of the flops to provide lift uuguen- propulsive lift, but with a portion of file fan airflow directed over tution, but a portion of the turbofan olr Is used for boundary selected portions of the airframe to provide boundary layer con- layer control, In the various applications of the concept, the trol. NASA-sponsoned preliminary design studies Identified llte blowing for the boundary layer control may be applied to the hybrid upper surface blowing concept as file best propulsive lift leading edge, (lie nap knee, me nap trailing edge, the ullerot, or ^omccpt to be applied to the Quiet Short-f laul Beseure" Aircraft to combinations of these locations. Figure I shows the arrange- (QSRA) that is planned as a night facility to conduct night ment of this type of hybrid upper surface blowing system rcscat.h ;d )ov., noise levels, bigin approach lift coefficients, and schematically.

steep approaches. Data from NASA in-house and NASA-sponsored small and large-scale wind tunnel tests of various configurations The Quiet Short-Ilaul Research Aircraft (QSRA) is a using this concept are presented, propulsive-lift aircraft intended to be used as a facility for terminal area operations night research directed toward the Nomenclature developnnenl of design and cerlincation criteria. It is a modifi- cation of the C-8A Buffalo and uses four YF-102 turbofan engines b - wingspan and an advanced propulsive-lift wing. Features of the QSRA include a steep approach capability at high lift coefficients and = boundary layer control BLC at low noise levels with margins for safe engine-out operation.

CL = lift coefficient, qS L Preliminary design studies, summarized in references i and 2, identified file hybrid upper surface blowing system as the pre- = lift caefticicnt at zero angle of attack CLa=O ferred propulsive-lift concept for the QSRA.

ct=_2 o CL = lift coefficient at an angle of attack of-2° Small and large-scale experimental progrnns were initiated to study the aerodynamics of lbcse concepts for application to rnax = maximum lift coefficient CL the QSRA. This paper reports some of the results of these rolling moment experimental programs.

= rolling-moment coefficient, C f qsb yawing moment Small-Scale Hybrid Upper Surface Blowing Tests Cn = ynwing-moment cocfncient, qSb gross thrust A series of small-scale wind tunnel tests of the trailing edge CT = lhnst coefficient, qS blowing version of file upper surface blowing (USB) concept was conducted by file Lockheed-Georgia Company. The tests were = blowing momentum coefficlent, Cp conducted under contract to Ames Research Center and are gross thrust from BLC nozzle reported in reference 3. Figure 2 is a photograph of the model qS used in these tests and Fig. ? presents the principal dimensions of file model. Significant data concerning the effects of nacelle = lift L chordwise location, nacelle nozzle configuration, Bap knee Pt /P„ = pressure ratio, total pressure at engine nacelle exit blowing, and nap trailing edge deflection were obtained.

tunnel static pressure E Figure 4 summarizes the results of a series of tests to study q = free-stream dynamic pressure the effect that USB exhaust nozzle chordwise position has on lift coefficient. For the three positions tested, the effect was S = wing area small but showed that a forward location resulted in a higher lift coefficient. Configuration studies showed that structural and = velocity V balance considerations limited how far forward the nacelle/ engine could be located, and, since the aerodynamic effect is W/S = wingloading small, these factors would predominate in the selection or chiordwise location. All other factors being equal, however, a a = angle of attack forward location would be preferred. Figure 5 shows the results of a study of the effect of various nozzle configurations. The = deflection angle of the trailing edge nap SF basic nozzles were rectangular in cross section with an aspect ratio

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*Aerospace Engineers. Members AIAA AT ^

The objective of file Loge-scal y lash, was to evaluate Ibe of 4.0. A deflector plate was attached to the top surface or tine effect of various configurations on purloin voce. with partiodar exit nozzle and tested at deflections ol0°, 10°, unit 20°. 'these Jeiluelons resulted hl "kickdown" angles of 20 0 . 300, and 400, ealphasi%oil enghw -ot perfornin". Iniln) t esting was dfrcLU ruspeetvely. In addition, the nozzle was tested with the auricular at determining file uplhnum nozzle dellectu , plate position. I it'.

set at 10° and with side plates added to Inhibit spanwise now, are 10 shows tile result of this evaluation will, the nunllicr 4 angiuc inoperative. 'these data show that inrreiscd delleeur plate The data showed that fhe plates used to Inldbll spanwise spreod- deflection imftened the available lift coe lracill mill also reduced I ng were detrimental to performance unit that the higher nozzle the engine-out rolling moment, With all eiiian s operative, Own: deflector plate delectlons Inprovud perfunnacc. This Is believed was a similar inervow in lift coefficient bd6 of course. there were to be due to spreading or the jet croux which results In a more Invorable ratio of jet height to nap radius. I.ow values of this no asymmetric lift forces iv generate a ollmn moment. As dis- parameter have been shown to Improve turning orthe jet ofllux. cussed earlier in connection with the sm,alli,caic lusts, the higher deflector plate deflections appear to provide a more favorable The effect of vitriois ladling edge flap blowing arrangements ratio of jet height to nap radius, thus improving now turning; improved now turning results in the higher lift cocfficienl. The is sununarized In Fig. 6.

sprecding of the flow (which reduces the jet height) also improves Variation number I was a conventional tipper surface blow- spanwise distribution In the engine-out case snd thereby reduces ing arrangement ;mid variations 2, 3, and 4 consisted of USB in the engine-out rolling Ilno ivni, combbadon with internal blowing at the flap knee, at the flap An investigation wasmade to determine tile effectiveness or trailing edge, and at both of these locations simultaneously.

Data were taken for nozzle pressure ratios ranging front 12 to flop-knee BLC. Figure 11 piesutls the results of this investigation I.G. The effect of pressure ratio at a constant value of thrust for the oliwngines-operative case of a thrust coefficient of 2.0 and for two main flap deflections, Al the low Bop deflection (repre- coefficient was found to be negligible. As shown In Fig. 6, the sentative of a takeoff not) selling), the effect of BLC (Cp = 0.14) greatest improvement In lift coefficient occurred its a result of on lift coerncienl was negligible. Ilowever, at the high flap internal blowing at the flop knee. Data presented later in this paper, and the results of other studies, indicate that this phenom- deflection (representative of a landing nap selling), a substantial enon Is configuration-swnsilive and ([lot nar-knee blowing would improvement fn lift coefficient was observed at Cp = 0.13. Fig- not result In large Increases in lift coefficient for USB systems In ure 12 shows the effect of BLC (Cp - 0.17) for the same nap deflection and thrust cocffacle,t, but with the number 4 engine which the ratio of jet height to flap radius is small. An advantage of flop-knee blowing is that smaller radius flaps may be used in Inoperative. In this case the improvement In lift coefficient is less but the stalling angle of attack has been Increased and both order to simplify structural and mechanical design. As will be rolling and yawing moments have been reduced. Figure 13 Is shown later, other techniques are also avallablr to permit file similar to Fig. 12 except that thrust coefficient has been reduced use of smaller nap radii.

to a value of 1.0, C = 0.084, and the trailing edge control flap pp Figure 7 shows the effect of deflection of a small control has been deflected 20°. This is the equivalent of a greater main flap, located at the trailing edge of the main nap, for various flap deflection and a more severe turning requirement. In this thrust coefficients at on angle of attack of 0°. A nap of this sort case, a greater improvement In lift coefficient occurs bill of more yaw- Is useful as a flight path control device because it has relatively importance are the relatively large reductions fn rolling and Ing monenls. These data show that flap-knee BLC can be bene- low hinge moments and can be actuated at high rtes.

ficial, but that the benents to be derived are highly configuration- dependent.

A comparison of the slopes of the lines for the three thrust coefficients in Fig. 7 shows that the effectiveness of the control As with the small-scale model, the use of a trailing edge nap flap increases with increasing thrust coefficient. The basic data for flight path control was investigated, Figure 14 shows the from which Fig. 7 was derived showed that at a thrust coefficient of zero (no USB blowing) the control nap was almost com. variation in night path angle as a function of control flap deflec- tion for a thrust coefficient of 1.0 at an angle of attack or 0". A pletely ineffective. Thus, the mechanism by which the control comparison of these data with the data presented in Fig. 7 shows flap provides flight path control Is primarily one of variation in that for the same thrust coefficient (CT - 1.0), the control flap the flow turning angle and is thus equivalent to thrust vectoring.

was more effective on the small-scale model than on the large- Large-Scale Hybrid USB Tests scale model. This Is probably due to die differences in configura- tion, particularly nap denection (60° vs 82°). It should be noted that the "nominal" flight paths shown in Figs. 7 and 14 are not Based an the above results, an existing 42-ft ruing span as steep as those normally envisioned for STOL aircraft during model was modified for a large-scale test of the flair-knee, approach. This is because of the fact that the models were not boundary-layer-control (BLC) version of the hybrid USB configured as complete aircraft and, therefore, did not have all caucep6 of the sources of drag that would be present In an actual aircraft.

In the large-scale model, for example, there was no landing gear A photograph of this model is shown in Fig. 8 and the principal dimensions arc given in Fig. 9. The model was powered or horizontal tail and the model was untrimmed longitudinally.

by five 1TI5D-I engines. Four of the engines were used to pro- no QSRA studies l,2 showed that steep approaches can be vide for conventional upper surface blowing and the fifth engine achieved at approach speeds that are compatible with short field was used to provide for independently variable flap-knce BLC. operation (60 to 70 knots) when the drag of an appropriately The aileron was undrooped and was not blown. Fixed leading configured airplane is accounted for.

edge slats were provided as was a variable control flap at the Small-Scale Seri-Span hybrid USB Test trailing:dge of the main flap. The USB engine nozzles weu>r configured to represent a nozzle using a separate core exhaust (split flow) that was not turned with the main "fan" flow; a A small-scale wind tunnel test program was conducted by special nozzle was required to accomplish this since the JT15D-1 Tlne Boeing Company to determine the effectiveness of vortex engine is a mixed flow engine. The results of this test program generators and irfernal blowing BLC to improve the engine are presented in reference 4.

exhaust jet. fuming over the USB flap system. Results of the Ian UgIGTNAL FAGS OF POOR 4U'

in oil where lac boundary lest, which was conducted under contract lu Ames Research adds momentum to flu: jet now Center, are raporicd In tolerance S. Figure 15 Is a photograph layer is close to separation.

unit Fig. 16 Is a sketch of the model used in this lest. The jet Presented In Figs. 21 and 22 arc outboard coginc ,out data exhaust nozzle was it low aspect ratio cruise type.

that show USB blowing to le mare effective in improving the III lift than vortex generators. 9"hls Is due mainly to the BLC blow- Installation of vortex generalors engine exhaust just ing enhancing the now qualities in the Bap region located behind forward of the USB flap knee resulted In a significant Increase in lift coefficient as shown In Fig. 17 for a flap setting representative tine inoperative engine. The combined use of vortex generators of a typical approach;Ianding configuration. The effectiveness and blowing at the flap knee furthur Improves Ilia lift, as shown of the vortex generators Improves with Increasingjet energy. For in Fig. 22.

example, vortex generators Increase CL by 1.0 at approach thrust and, at high thrust levels (CT .3.0), the CL improvement Concluding Remarks Is 2.3. The lift coefficient levels are compared at a=-2° to avoid nonlincarilles In CL vs a and to represent the higher Three series of wind lunnel tests were completed to provide geonietric angles of attack of interest since angle of attack, in characteristics of several variations of the hybrid basic data oil this quasi-two-dimensional test configuration, represents much upper surface blowing concept. These data show Ihal the hybrid- higher angles of attack for a three-dimensional case because vortex III and USB concept call provide improvements effects oil are minimal with this model tunnel conRgu- reductions in engine•out rolling and yawing moments. However.

ration. The Increased CL is partly due to Improved now attach- the characteristics observed are highly configuration-sensitive.

ment over the USB nap and partly due to spreading of the Jet configum- Accurate prediction of the r mracteristics of it exhaust by the vortex generators. Both the jet spreading effect lion will require wind tur,eel tests of a representative powered and the bnproved jet turning call seen in the oil now photo.

model, graphs of reference 5, Compared to vortex generators, BLC blowing at the knee References of the USB nap was less effective except at low engine power settings, Figure 18 shows that CL. increased. by about the same I "Quiet Propulsive Lift Research Aircraft Design Study," amount at approach thrust for both methods of boundary layer NASA CR-137557, Oct. 1974, control; however, 0„ Improvement was only 0,6 at CT n 3 for BLC blowing at the nap knee.

2 "Quiet Short Haul Research Aircraft Design Study," NASA CR-137554, Sept. 1974, A comparison of boundary layer control when using vortex generators and when using blowing at the USB flnp knee is shown 3 Wailes, W. L. and Chin, Y. T., "Small Scale Wind Tunnel in Fig. 19 for a Bap setting of 35°/600. The VA- tethods show Investigation of Hybrid High Lift Systems Combining Upper Surface Blowing With the Internally Blown Flap," NASA an equivalent improvement In CL at approach brtust and show an advantage In using vortex generators at the higher engine thrust CR-114758, June 1974.

levels, Blowing BLCat the aft USB Bap segment was also investi- gated. The results, presented in Fig. 20, show that blowing at this 4Carros, R.1„ Bolssevain, A. O„ and Aoyagl, K., "Acro- location was more effective than blowing at the Bap knee and was dynamic Characteristics of a Large-Scale Ilybrid-Upper Surface more effective than vortex generators at approach thrust power Blown Flap Model Having Four Engines," NASA Thl X-62460, settings; vortex generators are shown to be superior BLC devices July 1975.

at high power settings. It should be noted, however, that ducting S Fcifel, Winfred M., "Small Scale Wind Tunnel Test of air to achieve blowing at this aft flap segment is very difficult in an actual aircraft, Blowing at the aft Bap location is superior Internal Blowing for a Swept Wing Modified Buffalo Aircraft, to blowing at the nap knee because blowing at the aft flap segment NASA CR-137564, Oct, 1974,

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