NASA AVSCOMTechnical Memorandum 4201 Technical Memorandum 90-B-015

Aerodynamic Performanceof a 0.27-Scale Model ofan AH-64 Helicopter WithBaseline and AlternateRotor Blade Sets

Accession For

NTIS GRA&IDTIC TABUnannounced 0Justificatio

Henry L. Kelley ByAerostructures Directorate Distribut ion/

USAARTA-AVSCOM Availability Codes

Langley Research Center Avail and/or

Hampton, Virginia Dist Special

NASANational Aeronautics andSpace Administration

Office of Management _ _ _ _ _ _ A

Scientific and Technical DISTRIBUTION STATMENT AInformation Division Approved for public release;

1990 Di3tribution Unlinmitod

D0 07 31 025

Summary design and fabrication flexibility and cost effective-ness of compositc materials.

As part of an ongoing research program to im-

prove the aerodynamic efficiency of rotors. the U.S. As part of an ongoing research program to im-Army Aerostructures Directorate (ASTD) conducted prove the aerodynamic efficiency of rotors, a ro-a rotor performance investigation in the Langley 14- tor performance investigation w-s conducted in theby 22-Foot Subsonic Tunnel using a 0.27-scale model Langley 14- by 22-Foot Subsonic Tunnel using aof the AH-64 Apache attack helicopter rotor and fuse- 0.27-scale model of the AH-64 attack helicopter ro-lage. Two sets of rotor blades were utilized and in- tor and fuselage. Two sets of rotor blades were uti-

cluded baseline blades modeled after the current op- lized and included baseline blades modeled after theerational rotor and a set of alternate blades with current AH-64 Apache rotor and alternate blades de-advanced-design airfoil sections and tapered plan- signed by the Aerostructures Directorate (ASTD) atform. The purposes of the investigation were to pro- Langley. The alternate blades were designed to im-vide experimental validation for the rotor design pro- prove performance through the use of new airfoils,cedures for the alternate blades and to provide a data derived from airfoil research. and planform taper andbas,, for evaluation of current and future rotor sys- twist distributions determined from rotor design pro-teins for the AH-64. cedures developed by ASTD engineers at Langley

Aerodvnamic forces and moments of the rotor and tref. 1).bodv were measured both in hover and at forwardspeeds from 50 knots to 130 knots. Rotor thrust The purpose of this investigation was to providecoefficient in hover was varied incrementally from experimental validation of the aforementioned design0.001 to 0.0076 both in and out of ground effect and procedures and to provide a data base for evaluationat tip Mach numbers of 0.64, 0.58. and 0.51. of current and future rotor systems for the AH-64.

The results indicated that the design of the al- Comparison testing between the baseline and alter-ternate rotor was validated in terms of power say- nate configurations and correlation of baseline dataings over most of the range of thrust and forward with flight data gave added confidence in measuredspeeds investigated. In hover, at a rotor thrust co- rotor performance differences between the two rotorefficient of 0.0064, about 6.4 percent less power was systems. A similar investigation (refs. 2 and 3) com-required for the alternate rotor than for the baseline pared a baseline rotor with another ASTD-designedrotor. The corresponding thrust increase at this rep- rotor for the UH-1 helicopter and was the initial val-resentative hover power condition was approximately idation of these design procedures.4.5 percent. which represents an equivalent full-scaleincrease in lift capability of about 660 lb. In forward In the present investigation, rotor and body forcesflight, the improvement in torque required for the al- aad moments were measured in hover and at speeds

termate rotor was 5 percent to 9 percent at advance from 50 knots to 130 knots. In hover, rotor thrust

ratios p of 0.15 and 0.20. At the highest speed tested coefficient CT was varied incrementally from 0.001(i = 0.30), the alternate rotor had a disadvantage in to 0.0076 both in and out of ground effect (IGE and

rotor torque of 1.5 percent to 2.5 percent less torque OGE) and at rotor tip Mach numbers Mtip, of 0.64.than the baseline rotor. The deficiency in perfor- 0.58, and 0.51. Performance in forward flight was

niance is probably caused by the effects of Reynolds obtained from thrust sweeps at three forward speeds.

number and by differences in elastic properties at the Rotor shaft angle of attack ns was varied at eachnarrow chord blade tips. advance ratio p to cover a range of rotor propulsive

forces.

Introduction The hover results are compared and discussed interms of rotor torque coefficient CQ and rotor figure

Research efforts are being pursued within the of merit FM as a function of CT. The forward-government and industrv to increase overall heli- flight results are given in terms of rotor lift, dragcopter efficiency and help meet increasing demands and torque coefficients, and lift-drag ratio (L/D),..for speed, maneuverability, payload, and range. Ef- The effects of Alti, and ground proximity on hoverficiencv of the main rotor is one area in which )erformance are presented and discussed. Fuselagesignificant improvement has been achieved (refs. 1 download as a function of rotor thrust for bothto 7). Improvements resulting from better air- rotors is presented and discussed and comparisons offoils. planfori variations, and twist are incorporated model rotor data with predicted and full-scale flightinto many rotors used on helicopters today. These results are made. Reynolds number effects on theadvanced designs are the results, in part, of the performance of the alternate rotor are also discussed.

Symbols T thrust, lbf

Data in this report are presented in coefficient V free-stream velocity, ft/secform and are referenced to the shaft-axis systemshown in figure 1. r. y, z Cartesian coordinates

C) rotor drag coefficient, D/pR 2 (2R) 2 Y rotor side force, lbf

CL rotor lift coefficient, L/prR2 (QR)2 k. angle of attack of rotor shaft, (leg

('Q rotor torque coefficient. Q/prR:(QR)2 WrpP angle between rotor disk and free-stream velocity (positive nose-up), deg

Cr rotor thrust coefficient. T/p7rR 2 (QR)2 It advance ratio. V/QR

C blade chord, ft v kinematic viscosity of air.1.58 x 10- 4 ft 2 /sec

thrust-weighted equivalent bladeJ ((,'1 )-d(,'R) p local density of air, slugs/ft1

chord. U , ft(j (r1 l)2d(r/?) ( T thrust-weighted solidity. 4c, /r I

D rotor drag force. lb Q rotor angular velocity. rad/sec

d rotor diameter. 12.96 ft Apparatus and Procedure

The investigation was conducted in the LangleyC'.FI figure of merit. 0.707 - 14- by 22-Foot Subsonic Tunnel. The experimental

hardware included (1) the general rotor model sys-

f equivalent flat-plate drag area, ft 2 tern (GRMS) of the Langley Research Center, (2) a0.27-scale rotor hub dynamically scaled from the AH-

H height from centerline of rotor hu~b to 64 hub, (3) a set of 0.27-scale baseline rotor blades

floor, ft scaled geometrically and dynamically from the AH-64 main rotor blade, (4) a set of 0.27-scale ASTD-

IGE ffct designed (alternate) rotor blades that were designedin-ground to be as dynamically similar to the baseline blades as

L rotor lift force. 1l) possible. and (5) a 0.27-scale model fuselage scaledfrom the AII-64. Pertinent details of the test facility.

model hardware, and rotor design considerations are(L/D), equivalent lift-drag ratio. , contained in the sections that follow.

Tunnel Description,'I ip, tip Mach number for rotor advancing The Langley 14- by 22-Foot Subsonic Tunnel is a

blale closed-circuit, single-return, atmospheric wind tun-

nel with a test section that is 14.5 ft high, 21.75 ftA'Nm Reyvnolds mnber. Vc/ wide, and 50.0 ft long. The wind speed is variable

from 0 to 200 knots and can be operated in a vari-OGE out-of-ground effect ety of configurations closed, slotted, partially open,

and open. In the partially open test-section con-(2 rotor tor(que. ft-li) figuration, the floor remains in place and the tun-

nel is open only on the sides and top. During theI? rotor radius, 6.18 ft present investigation, the open test section was used

for hover testing. The floor was lowered 6.75 ft to ob-r local radius. ft tain ground clearance for the OGE (H/d = 1.4) por-

tion of the test. Figure 2 is a plan view of a portionSIS sea-level standard atmospheric density of the floor area that was lowered during hover test-

( Oilitions at 59°F ing relative to the rotor disk area. For forward flight,

2

(dat a were obt ainied withI the test sec'tion1 closedI. blade st rains and one channel of 1 itch-lilik strainA furt her dlescript ion of thev tuninel is availabl( inl were also lnonitoredl and recordled.reference S.

The tiiodel wvas suipported 1) a v t liree-joitit sting. Rotor HubThi sin aloedpi ei iu yw ost olin t a The 1110(1( hutb (fig. 5) was iyriaIinically scaled

nnich1 ats t-45- abouit at fixed point ili thle niodel. so and has the pertinienit feat ires of ilie fulfl-sc'ale hubil.

lcint lie Th stin ors r i i i on tled t ouinl itest-se tstiol- A detailed (description1 of the (lesigni and (levelopuiieflt(eiit~ eroe h t11 i5Iillielo lollsi- f thle hill1) is p~resenited iii reference 12. The huib is

piort svst eri that allowed height variation (0.43 < flyatiua dai etlrstleiil lvrdsrl11, d < O.S7) wit i t le floor ill place ats well ats soniceaddi t oial pit ch aindl xa tr onit nl. For t he forward- retenition s 'yst en and elastonteric lead-lag (laliplers

thlit te'sts. t lie rot or center of rot at ion wa i onl either side of the pitch cases: t hese featuires areIoel ontletitte et rii.056rtr(iale r uique( to the ftill-scale huib. The pitch'I case enicloses

aboved i the tiiclciloor. .5 oordanc thle st raps anid transmnits the feathlering iipit toal~o.(,OleHoulite blade. As withI thle fuill-scale huib. thle leadI-lag

The ttiiel (lata-ac(lifisit ion svsterii recordled tt n- uniot ion of r lie blade takes place lirouigli a fit tirig thlitin I rt ii (1 i lt 01i. t uiol~ieic oi~lt lri. conntects to thle otit oirdl lid of thle pit ch case, the

Mid iio lel Jparaliieter uinstirenients. The diata re- blade. and the leadl-lag (laluulers.itt ol lprocedllire inicludeld correct ionis for wind~-tiiiuel wall effects thlit ad'j listed thle t iuinel d'vilalli Bladeslpressl ire anid flow angularity lbv t lie mect hlod describedill referenice 9. Figure 6 is at plani view thlit shows key parali-

eters of thle niodel blades. The baseline blade had

Rotor System at linear twist of -90. a 1 0.5-percemit-t hick cauuiberedHughies Helicopters (111--02) airfoil front the( root 1(

'Fie general rot or riodel svstenli (CR MS ) of the the 0.94:3 blade radhitis station. anid at 2(1-swept tip.arighlev Research (Center is at fullyv instriiient ed that included a litnear transit ion to anl NAC'A 64A0 6

rotor-drive s 'vstelii which cani be coiirel for at wide airfoil at thle blade tip. The alternate blade hadvariety' of rotors (refs. 10 to 11) and( consists of two at linear twvist of -12'. anl increased inboard chord91)-lip electric iiot ors. at t ransrinissiori. and c 'yclic and of 7.17 inl.. andl a 5-to-I plauiforrn t aper front thlecollective cont rols. A iiiiiiiiii uisable horsepower of 0.8 blade radilis station to tlhe tip. Both rotors hadabout 160 was available duiring this test ats a resuilt at t brust-weiglited solidity of 0.0928. Treer airfoilof t raninuission yearinu~ considerat ions. The rotor sect ionis developed at the ASTD) for- rotorcraft apl-and powver train are IliolintedI and susp~end~ed withiun plication were uitilized onl the alternate rotor. Thethe C S onl a giniibal that includes pitch arid roll RC(3)-08 andi~ RC(3)- 10 airfoils are dlescrib~ed inl ref-

springs anid adjuistable (lanillers. Figuire 3 is at sketch erence 13. The (data that describe the miodifiedoft 11w A i 1-64 niodel mnounted onl the CRNMS. andl fig- UC' 3)-i 0 airfoil are uipublishecd.lire I is at photograph of the miodel attached to the The blades were fabricated froni coniposite nn-GR MS arid inistalled ill the( t uiniel. tennias to mevet the (lernanlding reqmfremnerits of dy-

Two Six-colnpounit. strain-age balances wecre iiatnic sirnlilaritv anud Mach ntmrniber scaling. DetailsNted for this test. Oile sripport( -1 the fuselage shlcl of the design arnd (levelopilient of the baseline bladesalld t lie atlher siipported thle rotor systerri. in(cli(1- are available in reference 12. The alternate bladesiini- ftli act into(rs. elect ric-(lrive root ors. arid trans- were designed arid developed tisilig siniilar nuethi-miission. Based onl balance diesigni specificat ions, the( 0(15 and1 iaterials. Typical miaterials included foani.rotodr balance dat a are ncctirate to ±0.000003 for balsa. rinex honeycomb,) fiberglass. S glass. Dti Pont

C anid --0.00002 for C- and represent 0.5 per- 1Kevlar. graphite fiber. epoxy, and tinigster balance.c nit of ftill- balance load. fid wever. previouis test- Weights.irig hlas deniionst rated an acciriacv of 0I.2 p)ercenrt of The accuiracy of the contwoirs of both blade setsfrill-scale balance load. The fuiselage balance had the was hield to 0.005 inl. or less. Straini gages were ini-,sauu acctirac 'v level. Thlle ffect s oif deadweight t ares stalled inl depressionis oti the blades: t hiese dIepressioinswere p ri (we%'d inl all cases. arid] thle aerodyniamnic hitib- were then filled and~ sinloothled. Wires were ruin in-drag t aro was rcriiovecl prior to the corn puitat ions of side (orudiit thlit was miolded into t in blades t o helpI. /, 1) J,. Ii (it (or rot at i nual speed arid roit or aiinut hal iiaiti m stinooth ouiter stirface.

po si tion were ruleastired )i'v all opt ical tachiorneter arid Blade speciruieris were fabricated and evahuat ed torigA. : . Made flappinig. feathecring. and~ coritroil an -ob)taini correct lv scaled iiiass. st iffniess. inert ia. antd

glswere itiotiitdire( and recorded. Ten channels of balance propiert ies. Root specilliens for hothi blade

3

s(its were tt'stt't to Failuire to istaliisl St ruci('t at Ill hove'r. perforiiiaiite dlata were taken with val-int.. gr it v. ties of' Ii/d f'romn 0.43 to 1.4 to investigate thce ffec(ts

flie Iiiist'lt lalide Struc( tural anldv I-1liiit prop- (of' gt'touii p~roximityi onl performantice. The modelert it's are prest'ia it 'i i ref'reii('( 12. :Aii (,Fort wxas suipport st ruturie pireveintedi testing to H/d z-0.30thlat I to) presertve t11 hfill-Sciltc( lvtiaiiit l)ol icis ill withI thle wheels oil the grouiind. As dliscuIssed( prvi-1itl cl ()I* of bid l bdb'. but t liet'e w('i't iliflittltit's ottsl]. thle witiil-tiiiiel test-:,ectioti walls andiilijng

inl t lit' Itip regioti wit I1i I lt' alternai~te bladles. Thie taper'i we're' raised(. and~ tie( fltoor was lowerecl when testing

itt then tip. iii citifliliinctin with thc m i odel scale. re- ill hover for thle otit-ol-rotird-effect conitionis andtsuiltc illii ditiit'isioiis ill tile tip reg-ioi thlit Yielded ill- rtsuIltedill 11 I/d =IA. Thie petrf'oriianit( of bioth ro-siiflii''i tttie to ;ii(uiratel' v lt'dl lniass andt stiff- tot's was e'valuaitedt at r'otor' llatle tip M~ach nimib(rs

iit~>ul~iaiti'l- is.I'mtlt e roo blade weightl o)f 0.61, 0.58. and 0.51. These tip speeods r'epresetettdit. at tinct ii )t' itbldi' raiiiiis is pret'iied iii figtire 7 mlodlel irotor i'piiis of 1(070. 963. allid 856. 'eshe('t ivelY.

fmt th lit liistlitit' alt rt'iiett. andt fill-scalt' lliil(. Te Groni-effect data for hover. inc'luding fuiselagetint a illI t(i tii.-uircthalit wilt' scaled to) maitchi full scale dow~iiload. were ob~taitied with i ti witii-t unnlel testWilt' tait fin u tlit', iiiautttii'r. sect ion ill thle part mall , open t'configutiloll (Side-

Illit' preicdh'i'l u'fiiliili('t lot' thle alternlate blade walls anld ceili''g raised anm1 floor iii place). Begin-lciiti wai> al it 7 pt'rct'nt tttr liani f*(r thlie baste- thug - with thle floor' ill place anid thle itiotlel at thle

12 t i-hint itl ' ill hjtiwi't reqieit'' It ii- fotu''rd (11/d = 0.87). poxxei' wasi1 minttainied at at consltanitflight fii-. ". Thei predictiloun' hod hI liiix't't pt'i- ttri'ct cotefficienit setting ((2 z-0.00018). and thle61't1i1alii ';V wA I 1iil'-dvlptt il nt ittit blade- model was lowered iii inicr'emenits initil thle lowest

r itialvcis. and l' forwai'd-tl ig(lit pretdictioni height permilit ted by thesupr yel ws1chdt1irithl usewd wasu (NSI (1n'f. 1 1). (11/4= 0.43).

At forward speeds. 1bet ter flow (pialit ' ill tie(Fuise lage tetst sec'titon -was mintainied by' testilig iii thle t'ltist'

hl 11;11 Wi, alc fimllthefliIl cofigl- test-se't ion configutrat ion . A value of 11/d of 0.56ilit' fuisiluign was stmi ruttlt lih tigi vsuaintaitied: this valtie placetd the rotor disk

taimi t'xt't't fkr t'e tail litoi. which required at a lvtiiilvncl etrie l nhssoci ,intat dialiii't iarge enug to at't'iiitutlate the athe nelerca cneln. A ui1'ssot'torretio (t)iltun to wall A Fetts indicatetd t hat t his

itig~~~~ fi.h tcis fttllg 1 tid'isbten leight resulted ili uninintinim wall anit stipport-sv'stenliili, st itig anid tail Inaith iltririg thle test. the lior- flow itnterference. Rotor lift variations were iiatle

ti i i' le Iis'lg'fttlt'alIioi jtiiitt ilt rer at adlvaniced ratios p of (1.15. (0.201. anid 0.30. Atwat waill it mittrit' (c~icittteh toita st raili-gave bl each value oif p. thlree anigles of at tack o,. werein't') as iiilicaite ilii figutre 3. Thit hi ntaitl an ltI testetd tto prtidte a v'ariation iti rtorit proipulsiveVerii l talils wce ho(t lit ilizetIditii this test. Allnforce. Rototr lateral anti lonigit uditnal [lapping w~ithicwihin figiitttins i nilue iiH';I winig-tinltited itiodel mis- spctohehatwrminiwdt1'toehcl.v.,is. t'Xi't't dutrinig ai potion i of th li' otot'-t41' tests. l's-ttt)tesatwr iiiiav'da0 oieli~

V~~a' ros lg'siladti btit niii tttor hilb vihratorv loads. The (data wereI atialvzedTilt l isip shcv andaterilF' b 'ilgs werets tiiissrom anid plotted ili termls of rottor drag coeffitient verstus

racs. lissit'. I iiziti alari v'l' inI tailier unti torque coefficient at cotnlstanit levels of r'otor lift. Also.F~ws, is~lcs 11wiz~ta ad vrtial tablizr. nd the tdata were analyzed ill t(ermis of rotor ( LI D), a~s

Inti ~ WIN Iitg in x it llilitd flr)iiti wood and itietal. a funtction of both rotor Cy' and p,.

'rest Procedures Since the miotdel hardware was niew~ and tinpro''eiundter operating ctnintions inl thle t untnel. at coilserva-

It 1t wiet' t'uinlutid iii hiovter anid at forwvard t ive test matrix was selectetd. Thel( thrnist anth speedspi 'til fr, bht it ,csts i i' blades. Ilovir t estinig was toniditions testetd were bielow the t hist and speed en-((hiui c iiliit l iiand ituit 4i gittittit effct: the rotor shaft pability, of the( full-scale AH-(i4. Exaintat iuon of flightwas, vi'rtuni ttl ni rsuilti'd ii a 5a tiose-tih fuselage data showed that for'ward speetds to about 2(0( knottsitig.li-. Fin-wit'il-si-''id tests were conidutettd front 5(0 (diving flight) atid rotor t hruist toefficienits to 0.0092

Stt) 3 kinits fo)r bit I rtor sets. (hiover: OGE) were reathied 1w the AH-6-4.

4

Presentation of Results

T'he data are. !)reseitelias otitliniQ(l ii te tale l('ow:

Fjt i IIreP 1,11 la rtlctr 1/ .1l II/d Comiparison

C)( vs Rove~ wr o(; 1 1. 1 Baselinet vs alt ernat e

FN) I\ v,~ CI ~ Hover .6 1 Baseline %-s altertt

11 Q ' C, Hover xi .5 s Baselinet vs altriatc

1 2 FM! v U/ .~ r5s Bazwliu vst x at irmca

IA 3 x CI~ liltr Biueline vs ailternate

I 1 FM U'. IV !liatr .51 ltazlizt vs alterntate

1.5 Fitmtlagt dIm ulouitl HowIleve (i6 1 Bil ilv V.s adlteriat

vs rottor t hrilt

16i C/ If d flot Ai Vat t! I~l ied B i t'll vs alt en tate

7 C(71 %J Cy> (T 1 0. 15 tot ((.3( 0.56 Baselitne vs alternaite

L I), ~ '~~~ 0.3 t 0.3 SI Baslitte vs alternate

19) \'tltjlt t ttrqtte co effiientt fHover i 1. 1 M l~t5'ili vs fli! snale

v~s CI

2(0 VehIicle' torqueit coeftticit lit 0. 12 to (1.35 Bas('lc itvs full Scal'e~-vs ftorwardl 51pved

Results and Discussion at that vehicle weight. Specifically. the advantage inCQ for the alternate rotor as measured fronm figure 9

Hover was 5.7 percent. 6.2 percent. 5.1 percent. and 3.7 per-

The ox-r peforanc resltsforthe aseine cent at C1, = 0.0050. 0.0060, 0.0070. and 0.0073. re-"Idt r e over s ael rntaic e restlt for t heiofC ba elin spectiv('. A valtie of CT = 0.0080 corresponds to a

sustd- alenat roto'rsti Cre clare 11in t= m of6 C10 per- full-scale weight of 14 667 lb) at 4000 ft and 95'F and

(-(tit rp iati figuets 9 > a t10 Altip =064 (100 The' was close to the highest thiuist tested at 11 i, = 0.64(til rpi) n fgtirs 9an~ 10 resectvel. ~for the alternate rotor. The 4000-ft. 95'F condition

alte'rnate. rotoir re(Iiired at lowe'r CQ(less pwre- ianimportant diesigni criterion for Army helicotrqtiired ) for a givn vahtie of C-I- in thle( range ab~ove toesradqteortialefranetdr0.0i02 (fig. 9). The sea-level-standard ( SLS ) thlruist tota, hiigh-aeqalt ie oelittions.promac ie

((tilt it ion CI. for the' full-scale helicopter at a inormnal htdy ihatt odtos

operat ionial we'ight of 141667 lb) is 0.0061. As seen in As seeni in figure 10. the improvement in FMI forlhe figu re, for that t hrumst conidit ion, about 6.4 pe'r- the alt ernate rotor wa~s redtucedl from 6.4 percent at

cenit less pttwor was ticeered for the( alternate rotor SLS to 5.4 percent at C1 = 0.0073. which is nearhan ftr te basecline rotor. Flit. thrtist increase at hle peak FMI tested for thle baseline rotor. The

C 1);:;000049.corresptondinig to) the aircraft weight of calculated (designi goal of a 7-percent improvement in11I667 lb). was ttpproxiriatel'y .4.5 pe.rce.nt,. which rep- hovr powe'r reqtuiredt (fig. 7) for thle alternate rotorresents an iiicrease in lift capabilit v of about 6601lb was nearlY mret.

5

Effects of Tip Mach INumnber great er t han fromr thec liaseliie. sice the alternate

Hotver I)erforii v~ t1ltia obtt ainied byusill r i ( 'ri (lesigni calletl for rntccease(l inlboar o atting (hiigherhealtes teliri~jres~ .twvist: mrore I la(le area,, itil)oarl). At a rotor thru-lst

ti(;t tet (,cmiiic t Mil) 0.58 (90 percenlt rpiiml) o 001)(I .0-) - nrm l islanil 0(.5 1 (, 8() prcent i imi are givenii i figuires I of17Ib( ~ 006). ices nfslgto 1 . VXiiiril o f iles (iltil il c'oijlt no Wih tokvfloat(I eiivaileiit to tbotit 0.5 p)ercenit of the

liedat oftiuirs 9ari I) (.X1 = . i-I)ict' vitlt total rotor t brust wais nmasreti for the alternateWitI r iil otiVo itt s oo'tp\il itrl' otor (fig. 15). \liri t his inicreatse inl tlowiloatl is

wi ts redulced. First . t I i tr( I iuace ill I llovelI inilt for stubt rateti fromr t lie thirust gaini for thie alterniate

th ai lternaite rotor ill tenisl if, [N ; I = 0.00- is roito r (fig. 9). at iet ljerformine gatin of 1.0 1wr(Prilt

reC(lttc(i from 6. 1 pecrcent mt A ,1 = 0(.61 to 2.S Ietii tilrt ist at CI- = 0,006i1 i, reaIizedl.atl 0.51 ( coropitne figs. 10 aid~ I11). Seconi. Th'le dlowniload~ ritstr(l for tHie batseline rotor

botil rottor., aclieveti 1higher vtlties of [-',I atl rttilced wa'is rtonririll 'v 5 to (6 Itercrilt oif' roor t lutist for at

1i1 ,. TI( te peak vailie of' [-NI for lie( ahlernate ro- t ,vpieail liover tirtist coridit ion (CI- = 0.0064).Taloton was 0., 0. 0.79. arid 0.78 ;k31 = 0.51. 0.s Itootti dIowNvload~ e(tflitt ions, batsed(tn o ototr wake

i ( ().(i. r(s.'l)tt v alo it rttssover ilvel'Jvr -locit ' .vril draig coefhiero l. arol( tail boorr area.ari ivlv.:\lo. n le 1Cr iiica-ite(tlihat thec tatil-boor ((tril iti i inicreasesfortiire ctirves, it tilie lowecr t lrtist ittetfHicrtS sc te-foib mi~lltom . w-cit is( i

(tirretlc~ bl~cowk ;I tisible flighit opt'nat joltal level. ['on orlaryaiaii oil05Pri a~Ioexaritl. t ~I1~(151(fgII.tletie5rosa rietlinrienIlitsotiietl,( duirinig t his irivestigatioiu arIC ~ ((t)I. iiii~n nrosItir ()er oberedaid onnstilts frorm siriilar investit ions (refs. 15 ari

nitel i referrite-s 15 aridI 16. Sltecili(itllY. lit( 18). tle dtwilload( nesillts alre reastirililel.

ilrorease inl [.NI wvit It redtlicetl 11,j il~ arilie crossover Ground Effects

v t [ I t It w iilt i o f it i ( lt c 1 . X1 a g r e T h e ffe c t o f' li e g ro t ir id :ie se rm 'e oni tire hio v er

wit I ie ti ll~ r e rted i ef rece 15. ilw -m t l)erl'Ornimrce of hot Ii rotors is givenii i fig uire 16 inl

ai~ bktselirie llcs irs at frulict inn tif M~j itr e nt t ermts of C-1- \'Tstis 11/d ait CQ2 = 0.00048 ( riorriril((trri)ltettlv iroilerstt )t(l itt l)W-st'it. blitile cf, c of' vatlte ) . [tiselage dlownload~ vits riot stnbt ract ed frorii

rot or t lirtist inl tiese damta. Thle restilt s indicatte t haitX1l,, isI lik-!' tot be )tine of t lie fatctors. Fir exarri- goiIefc i lc1efim ieo ol oosi

J~tc tie mvime~trotr lml i bltki ti) dor~ of vtrtrrallv equial te largest dfiffei-rce is less tHam1.13 ilri. ait ;i lii t\.t till sj)teetI of 727 ft /sec(: t liese 0.5-p)ercent rottor t lirrust att 117d = 0.13 (wheiels atbouit

fitetot- rs eslteti inl it til) Bey'ntolds riiriltr of lbout 6 ft (ibove thev grotiiat fuill scaile).0.5 <l0t'. Large ciarigs inl io rr(lviariic (ianact er- roiifee'tsnfulaedw odwreri-ist ics itre kniownl to toctir. inl this ranlge. By cortipar- sicfm( mveI slcgi isr(ic( r /

isoll.~ ~ ~ ~ ~ ~ 10 al( i)levll~ iil rfr til a otorl =is I -1 to 1-1d '= 0.43. thiere wats at re(tit io inl fuse-line fiae inl hover is atitttw 2.2 x 1( ti oo til lage dlowniload (-73 lb) of alI)roxirratelv thie sarure

s itf' 727 ft 'set. .Sirrilmt restilts wecre obseve iiiiitil astl tc-aeilrtrtiist(6 1)ir 5:1 p~torlrr tlt trerf. itrotor factor tlImt liml App~roxirtiiaely one-hialf of tile total positive groitrl-

it 51 I)imfom ti) til~cr Atitlic fiator imt ms effec(t ciislioriexpenieiiceul by the iio(lel wats; therefore1wrml~ lt cei Ligr ~f(,(t il otr ;croI vl,-lli(- gelirirte(l byv chanlges ill fuiselatge vertical force: thie

1i-fttrrriiri is, blaue elitst it prop~erties (ref. i 7). One( rerriiiidr of tlie grotii ('tisliioli c-anl betttri1)tI totttrtltsittriin iftnerce 1 irdittet tht ~effcts lie( more famriliair rotor tirrist curisitiori. Sp~ecifically.

riii\ ht r i io r lit rotot r aerotly viari c test rrrg ('otl~ared.( tlie fiiselage verticali load wit Ii eitlher lie basel inc ru')-wvitl Iiv Ia'fett of Itad last it Itrt)perties (druviamni- tor or thec alternaite rotor iist illedl elIiungtu from- a

C'liv -;ealed rtttr hles ve--sti '-rigid- Itads) owiltiadat 11/d = 1.4 to anl itloath ait 11d 0.1A3.Fuselage Download Thtese effects onl hlici(opter fuiselage tlw itad ast

Atiuilrat jr-Iitti o f' hover iterfutriianl(c liss fmuictiori of hevight are( consistent withi 1)reviotislY pub-(Imti t) ftis"eliige ulowriload( is still it tliflictilt decsigni lisliedf nestilts (r('fs,. 15 aid( 19). Also. t lie groiuri ef-

Itt))( tlrt.T e istiretl friselitge tlttwriload( for luttl fects toil thec penformiice of tHie corriplete riodlel wverenot irs att I1I /(1 I.I antI atl .1!, = 0.64 is gkive inl agrertiru wheni eonrrpae(l wvit I flighit dat~ a anI

itt figui1rt VIS isi5 firict itii ul' rtitor til-ist . Th'le caltilte l slts (ref. 20).fuitiai'erlgtiat ioni irieltideul wings andl 16 w-ing- Forward Flight

roiiturtedI rriolel rmissile's. A. sriall iircase ill friselalgetw(mri iltm I was rrt ist rretI foir tHie alteriate ~Ic daeo ver Rotor lift vamiatioiis. I icrerio l ruit ir lift

it t litit riirige oif 250t to 1250 )lt. It wvas t'x1)eutt'(l vaitionis for lt( ielterrite id~ baseline rotors \%-erehlat Hte ulttwriloadl frorr tlit al~ternate rotor wvotihl be p)erforrcIl (fig. 17) at it 0.15 (65 kiits). 0.20

6

( %6 knots). and .30) ( 13(0 knots). The lift varia- At full sc:ale. these rotors also exhibit large (hf-tions wvere miadle at thlree v-aluies of (o, to vary' v ilie feretices in tip Hevnoldls inilber. aiid aerodviiainicrotor dirag forc e at each value of pi. 1)ata were not lperfornine dlifferences wouldl be expectedl as a re-olbtaiiied below p = 0.15 alec-aiise of t 1w excessively' sit. For example, at an advance ratio of 0.30 (aboutlarge t unniel wall c-orrec(t ionis that xvere reqluiredl At 130 knots forward speed). the full-scale Reynoldseach value of p. thle resuilts froin bothi rotors are min1- inumbers at the retreatinug lblade tip) would be ab~outparedl in ternis of rot or (hrag coefficient CD/al][ versus 1.4 x 10"' and 5.5 x 10(' for the alternate rotor androtor t orquie (,cethejent (' /aj for three levels of ro- biaselinie rotor. reslpect ivel. The effec-ts of Reynoldstor lift coefficient C/a.The vaiati'ionl Of CL/T iinber wouild b~e expected to be less, however. iiiinvestig-ated represents at range iii full-scale airc-raft the higher range of Re 'ynolds niumbers afforded livweight frontu approximately t)6 01) to t6000 lb at the full-sc-ale dimenions.SLS atnmiosliheric- moildit ions. Figure 17 shows cross-plots 4)f CL/) %7j vrsus,- CJ)/rnf and C1 /a-1 , versus Rotor cruise efficiency. Rotor cruise efffiiewmi'

C(2' (j-* This mnetho 101Perulits C'Q/GJ- ColiParisoils ill ternis of ( LI/D), wais c-alciilate1 for thle two rot orsb)etweeni the two rot ors to b~e made at colstalit val- using data ob~tainied (hitring rotor lilt variat ions at li =lie.s Of C1 ja-j1- and rotor propuldsiVe force. 0. 15. 0.20. and 0.30 (fig. 18). At eachi speedl. at vah ine

At = 0.15 (fig. 17(a)). the alternate rotor had of o,* was uisedl that rep~resenitedl a trimli p~roulsiveat lo wer requiiredl valueC Of C(2 1/- 1 - t han t he lmSe hue( force( equal to a fuill-sc ale flat-plate dlrag area of about11rotor4 over thel enitire range of Cj/ 1 - i:ej.ae( 1 ft 2 . The equnation iised in thle calcumlat ion was

aiid for each of thle thlree C 1 7cr- cmditiomis. Ther(dict 1011 ill C'(2/a7T requlired1 for thle alternate rotor ( )CLwas nmiimallY 6 to 8 p)ercenit over the enitire range of D = 2 ([lift ale1 propullsive forc:es inive'stigated. i

At p =0.20 (fig. I17(b)), Cc2 /aj'y required for thealt ernat e rot or w\as niominally 5 to 9 percent less thban A mieasuredl value of the rot or hill drag coeffic-ientfor thle baselinle rotor over thle ralige( of lift alid drag (0.000)1253) was subtracted froni the rotor drag termi.inivest igated. The imiprovemlenit in C(2 /a7-- for the The lift. dlrag. arid torque values were (derived fromtalte rnate rotor was 8.7 per-elit at a CLI/u- 1- = 0.073 the rotor lbalaice data. For example. at C-p/-17-anid ( 'f)11a-y -0.0033. This level (of improvement is = 0.07. the alternate rotor indicated imuprovemnitsapproxiliiatel 'v thle samie as that given irx the previons inl (L/D),. of 9.3 percent alid 10.4 percent at p =disexissioli for pi 0.15. 0.135 and 0.20, respectively (fig. 18). At it = 0.30

At p =0.3t) (fig. 17(c-)). Cc-2/aij- requiired for the andc at the s8")e CT/aTT. howvever. the alternateatcateroto)r was. 1 .5 to 2.35 perelit higher thani for rotor inolicated a 0.3-percent disadvantage in ( LID) )

thle biaseliiie otor ovemr thle range of lift arid dIrag ill The decline in performance at p = 0.30 follows thevvstiait ed. At t his value of p. the calculated design aforemxentioned trend (fig. 17(c)). where thle alternategoal for thle alterniate rotor of a p)erformlanxce adlvali- rotor dlisplayed1 a 2.5-percent disadvantage in CQ/rTT

agep of 2 percevnt miipared with lthle baseline was not required. Also. the samne reasons for the olechine inmet. A portion Of lie lperformialice disadlvanitage for perforinance offered in the previous discussion applylie alte(rna~te rotor (0111(1 have beeni c-aused l~v opera- inl this case. Results obtained at thle ASTD onl a

14)11 at si inhrit ical Re 'vnolds inibers in thle rotor tip rotor designed for a modern iititv helicopter withre'gioni. D~ifferences in elastic- properties in the blade similar blade dIesign techniques (3 to 1 tip taper)top region (o 111( have been anot her contribit ing fa( buit without the pit falls of NR, through thle usetr. The nam 4W, Hord tip ( 1.43 in.). ( reate1 by biothi of Freon 12 as a test inechililli ill the wind tililiel

sc-aliiig ahi,, design (5 to I tip taper ratio). re'suilted indicated significant 1)erforlialice impilrovements iipill a ret reatinig blade tip with Ii \' - 0.373 x 0( to p. 0.37 anid CL1 0.0107 (ref. 21).;it pi - 0.30. Large sidlirit ic:al Reynolds nuillier The forward-flight rotor perforlmance trendls alletf#'ctr .s oijuld occujr at mnmbers in this range. At point to large imlprovemxents for the alternate rotorp4 -t. 15. th lie 'evii dds nmeiiber at the retreating tip ( imp to 10 1)erc-ent ) over the speed range invest igatedl(of t liealternate rotor was 0.468 x 10" . 13v cotuparison. excclpt at t he p~ = 0.30 condhit ion, where a slmall

he haselie rotor had retreating blade tip Reynolds olefiriency' occurs for the alternate rotor. Data atiib rs Of 1..IS x 10" and 1 .86 x 10"; for p = 0.30 full-scale fieynvrolds nummber values are nieeded to get

and~ p -c 0.1I5. respectivelv. Airfoil (lata taken over a moore accurate indlication of relative performnimcehe range O f Rlc ' rilds niimrbers of interest were not between these kind( of rotors at. the high-speed. high-

;ivailab le to 4)crrect the performatce dat a. lift moidit ions.

7

Comiparison of Model Data With Flight AH-6-1 Apachc attack hlicopter mrissioni was .,ia-Data sillel in hover and( at forward sp~eeds bet ween 50 and

(Thiiparisol o4 winll-tulicte iIldl dlata t(o flighlt 1.30 kniots. A baseliiie rotor, miode~led1 after the(lilt a is If, jlt crest ats aii t her way to( inlcase ((0 1 cuirrenit AH-(i4 rotor, was also investigated to pro-lilii(e ill 1110(111 result"5. H over anid forward-speed vid coprios The purposes of the invest igat ionper-forriarice results for t lie baseline rotor ;it-(, coiii- were to validate procedre ise a 1( It the Acrostruc-

prel Iwith filighit dait a t akeii onl t lie fill-scale AxH--64 tutres Directorate (ASTD) to design rotors with in-l Iihc11)te* ill figures 19 and 20,. respect ivel. Flight creasedl performianlce potential and p~rovide a data-lati a ised inl t li comiparisoni were obt ainied fr'oiii baise against wvinch to evaluate current and futui e

iltfrelice 22. rot or s ,yst emls. The p)redIictedl performnice improve-flovelr. IHoIver d) t- tg( i -fet(at a are p~lot - inelit for- thle alt ernate blade (lesigi] was to provide

e~Iasvhcl iq i offcet esu rls about a 7-percent impllrovemniit iii power repuired ill(icli as r hic traqe Itiicl tsl trust coethiiisfoni0.01 hover and a 2- to 9-Percent imIlprovemient iiipwe

,t03fg I9 h iilIltsi~hlel(it o i reqpuiredl in forward flight over t hose required for then t(iro v.aI corcboswr ena)lelfri aseline. Fuselage (dowinloadl and( grounil effects iii

p1ml wei(m isliliipt ionl of auxiliary hydldici an clc ri hover were also invest igat ed. M odel andl flight dlat aen d evices'. gI'arhoxes. taiil r( t ( I. iail( fiseig lodwni- were coiiare(1. B~ased onl anal ,yses (If (hita obt ainedl

P~ ~ nd lefrinaue ocrette11(( ~t (Ilirilig this ilivestigatioll. tine following conclusionsfon. u lise iteiis was supJpliedI h)w the aircraft niu- are (Irawni:tact uirer Thie fuilselag'e (dowlo adl correct ion was nica- 1. Iii hover. at at thiruist coefficient C-1- of 0.006-4.ir( fcI Iilri rig this imlivest igtion, anld thiese vat uics liaI\ thle cllcuilateil (](,Sign goal of a 7-percent immprove-

I 1(1 iriclid (,d iiit liet, ciruti11(1. The correctedl niodl iiet ill power req1uiired (alternate rotor versus base-dat a are ill g(m i arenileit with hil tHlight dat a. atl- line rot or) was ricarl *iviet . SpecificallyN' the iii-li nighl thel imoel hvmpeoriaie(tahadl abouit lprovei(nt iii torque coelfh-cierit C was 3.7 percent.

2 ti I lIerI('it higher thlruist for a giveni torque (01dbi- 6.2 p~ercent . 3.1 Percent . andl 3.7 percent at at C-j-(i( lit Iver I lie rangec t ested. This result is coit rar v to 0.0050. 0.0060. 0.0070, and 0.0073. resllect ivelY. Atti II XpIrim rice of past invest igations1 ( refs. 1. 15. and~ Cy-- = 0.1)064. which correspond(s to a full-scale air-7 . wxhich have showi t hat inmihl rotor p~erformniice craft weight of 14 667 lb) at sea-level-standard (SLS)

>uiare pessim iist ic. That is. Ilerforniance is bet- atmnosphleric coniditionis, an increase in thrust capa-er with fr ii -scale aircrabt thlan with miriodels. Low bilit *v of 4.5 percent was realizedl for the alternatehtim tIIl s miimii Ir ('IFfect.-; lssocialte(d withI models havie rotor. This increase in thlruist capability' representsIleruid(ent itiell as one of the lpriliiar v factoIrs respori- an increase in lift capability of about 660 lb at thatsile 1*I i- i lu mu red l perform iian ce. Thle reasonIt for t he vehlicle \&eigh t.

9 (ilt renid ili th p reseiit invest igat ion is jprolla- 2. lIi forward flight, the re(luct ion in rot or torquehIy v Ihim II IrrII! i r to( thle mo del rot or-alone (lat a to( coefficient CQI/o--j- for the alternate rotor was non-ial'olir t fo~r lossin 5s inl t ait-rot or po~xv'r arid su bsv, stcii riallY 6 to 8 percent andl 5 to 9 percent at advancepowe(r. Also. ilit riodel ina ,.y havye experienced berie- ratios it of 0.15 arid 0.20. respectivelY, for the rangehiciall gr (uil effects fromn lie p~reence of the fuselage of Cj./u- 1 , and Cljl/u-1- investigated. At it 0.30.ari( p issilble tiuymel test-sectionl recirculat ion. the alternate rotor had a disadvantage in CQ/(TT Of

Foi-ward flight. Tlhne f Irwarll-fI ight p)(rformni( il 1.3 to 2.3 percent over the range of rotor lift coef-rvsilts for the baselinec rot or are comipared withI flight fiCient CL~/077- and( rotor drag coefficient CD/aTT inl-

(lit i arilplo te a veicl toqu cofhcen t (ti vest igated. The calculated design goal of a 2-percentdatIrarld sploted frrillsl vehicle grqu o ssen weight performuance advantage at it = 0.30 for thle alternate(If' 11 667 lb). a flat-plate (Irag area f (If 33.8 ft 2 rotor compared with the blaseline was not met. The

a n I a nl(shei ( lili on n fgr 0 h calculated performnrce advantage for the alternatemir (((l t Ilflih I rea cui was geneal fi ute goodfil rotor was mect oIr exceededl for the it = 0.15 and 0.20(wit hiii ustiat flight -test accturacy oIf 5 percent) arid cases.

h~~r Ivi el: i raIc rfllr(ei h lollr'ul .3. The redu~cedl perforniance gains for the alter-pridedI-u miit i n co)nfIirr et i h inl odel (resls.(' nat rot or at high Cy iii hover andl at anl advancedThe til-fI u I I (Iwr a)rcid t h raodiies l data1 or lostsaei rat 10 (If 0.30 are probably thle result of Reynolds nuInii-

frImii figure 5 (If refereriem' 19. her effects andl to dlifferernces in blade elastic prope--

Conlsin ties. partictilarly in the tap~eredl tip region. These ef-() ItCit iiollsfects are plresent at full scale. but would be expected

Pm rf rtiiui(- (If' a 27-per-cent. dlvranlicallY scaled to be less at the higher Iievri(IIIs niinber ranige af-rmil 4 (I Ii alttiat e rolto(r (Iesigried for ft(i forded at frill scalhe.

8

1. At it hover out-of-gronlid-efl'ect condition with 7. Mh.Veighi .ichael A.: and McHugh. Fraici:: .J.: Iflhuelce

('. = 0.006 1. the fuselage download for tie alter- of Tip Shape, Chiord. Blad , Nuiier. and Airfoil oii

nat e rotor was highcr by abou1t 0.5 percent of tie Advanced Rotor P erformance. J. A rwan lhloptr

rotor thruist: this (diference was probably caused by Soc. vol. 29. no. 1. Oct. 1981. P. 55-62.

increased iiboard loading desigied into tlihe alternate 8. Apllin. Zachary T.: F101l' hnprl t i01T i7fS h7 thu ('rcult

rotor throughr the use of higher twist and longer of t/u Luoq,"y 4-bhq 7-Aftr Tuonul. NASA T\1-85(62.m1983.inboar(t chord. W hen tlihe increase il downoad is 9. Hoso. Harry I.: Ue, of S twrpositwn i D igial or-subtracted froim tie thrust gain for the alternate 9 Hputlri 7o Obtai 14 111-TIMM I h1/,,f7VI71tlt F00(10.S f(orrotor. tiec net pcrforniance gain is reduced sligitly Arhitar (C'oljigitatons. II'th Part',a' 16 fllo-f tofromn 4.5 pcr'cnt to -4.0 percent at C'T = 0.006-4. I'/STOL Mod s. NASA TR 11-302, 1969.

5. Operating at reduc'cd rotor tip Mach inibers 10. Murrill. R(bert .l.: OpIttot Ind Mait,,mt, .lMlor

(. l/Iip = 0.58 alid 0.51 comirpared with Ii,) = 0.64) fori tit ( 'nyal Jtor Alod I SyiiVI. NASA ('I-1 15230,.rvirede Ill( hover performlance adlvantage for tlihe 1977.alt ernralte rotor in tcrrus of figure of ierit at CT = It. Wilson. John ('.: A (;e ral RotoIr Modit1 Sv.,w'm foI,

0.006-1 frori 6.1 percent at -I/i7 = 0.6-1 to 2.8 percent Wind-Tuil Invstigations. ........ vol. 11. no. 7.

at M 1ij, = 0.51. Tire reduced perform'arce increments .July 1977. pp. 639 613.

are riot 'ompletelv understood. but tIhe effect of 12. Straul. F. K.: .rohnstorn. P. A.: lhad. R. F._ and K.t-

Rriyolds rmber is probably one if the factors. 1ev. 11. L.: Design arid Development ,f a I)vilayllically

6. Irn hover with cither rotor. tie fuselage vertical Scaled Model AHI) Main Rotr. i f/I A HoII llCI-oft f07-11171 (Th, ttayo,. Pi,. A'ctlhvrlant). All',. l98 l.

fr'ie 'hanged froi a download at rotor height to pp. 63-I 63-21.rotor ihaneter ratios H/d between 0.5 aid 1.4 to 13. Biiglam, Gerte .1.: and Noonan. Kevin \''.: Two-a frsIalac Ii1)1ad at 1i'd between 0.43 and 0.5. D117usi1(/AclOoh/T (Oh 't171 .1t .1st of Thr7 Rotor-

In fact. allprxirnatelv one-half the total ground- (.'aft .4irfols (it Mach Altlriiis Front 0. ;5 to 0.90. NASAciushioin ,benefit frorm the irmodel came front fuselage TP-2000. AVRAD('O1 TR 82-13-2. 1982.ul)ad. 1I. \'ali Gaasl/1ek. .J. R.: 1?otorcraft F light .S/7 at (7t.

7. l( -rind had virtually the sanrie effe('t on ('omputr Program ('81. ol,, II 1'.%,"s . la i a S.

I'SARTI.-TF-77-51B. U.S. Arriy. Oct. 1979. (Availalh'h 1 (w r tp e f or l c e fo r t h e tw o ro t o r s a t 0 .4 3 < f o T C a D A 7 3 .f Id < 1.1. froi I)TIC as AD A079 632.)

15. Batch. )avid T.: Experimental St udyx of Main Rotor.iTail

N.\SA Lant'v Il'>',arl'h (''enter RotorAirframe Interaction in Hover. .9th A/nnal PI /

lmpt'. VA 2 I.65-.5225 Procrd (Wi s. 4 tot ri'a Jilicoptfr 5(oc.. 1983. pp. 1 11.

May !. 1990 16. Ph'lps. Arthur E.. III: an/I Althoff. Stusaln L..: Effcts .IfPlanform Gom tr o l 11 '17 Pf fora(inc( of a .2-M( N¢ r-

R eferences Dianltufr Modcl of a Four-Bladcd Rotor. NASA "'M-

g t (;it' .. : TI/he AI'ro tiia' Il/if o I/f Ro/tor 876)7. AVSCOM TH 85-B-6. 1986.

lBlac AirfoiL. wbvit. Taper aind Solidity oil Hover and 17. Yeager. William T.. Jr.: and Mantav. Vav'vne, R.: ('orr7-

Fi Fl ight Perfolrmttance'. Irocu diTs (If flti0/ 1)I itol/ of Full-Scale Hc/icop r Rotor Pcrfor/mancu t/ Air

.l/mn/ .V,"h,mpo for,' ...I t(rifn o ,' ropt r Soc.. 171c., With Aodcl-Scalc Fron Data. NASA TN D-8323. 1976.

11. pp, 37 51/. 18. Flemming, roi)lr/ .1.: and Erickson. HRvulii E.: An

2. icrrv.. llt D.: Quart'r-Scah' Testing If an Advanced Evaluatiorn of Vertical Drag and (round Effect Using

Rotor Svstetm for th' ('11-I Hl('i'opter .71h .4 rmIl till(' RSRA Rotor Balance System. .8th Annual F'orum

['b1r7m IP'i1 , , &mq . .. Ar 7/lon Ilwopt,'r Soc.. Ic.. 1981. Proc'di/gs. A m,'(an tl lclopf(r Soc.. 1982. pp. .13 51.

)). 156 162. 19. gradenitrgh. Evan A.: Aero(dy' N jnamic Design of the

3. 13-rrv. .ohn I).: P1 7forrmam- T'.sting of a Mm !otor Sikorsky S-76 Hehicopt er. Preprint No. 78-06. .41f1 .471-

Sptfl711 fm it iit/ y I /l',m(/r (t /4 Scah. NASA TNI- nual Nation l Forum. // o , '1 a Hcw7(,7r Sf'1.. Inc..s3271. \VI) A D( ' T ? '.\ I2-4-3 1982. May'v 1978.

1. K..., ('harl.s N . N'I 'ih.. Michael A.: 1)ah/ie. l.u ,: and 2). (Gessow. Alfred: and \ lvers. Garrv C.. .Jr.: Acr'odynamcs

NIluighi. Irm/iS.(: Coside('rations in the :imation (if tt/ f1'lioptcr. Frederick Ungar Pril. (o.. c.1952.of 'ul-.Sualc Rotor P'erfirmance From Mod(l' Rotor Test 21. Yeager. William T...Jr.: Mantay. \Vayn, R.: Wilrr.)/ttI., /r711,' ,l 1q, of fhl ./fI .4 11/1/11' .'o'iol of ti Mattiew .. : ('ramer. Rolert G.. Jr.: and Singleton .hf-

.1 7711 711/7H1 II1pt( 1S 7 '(e1f . May 1982. pp. 3.1 13. frey 1).: Wi d-T7/7/ Faluatio7 of a7 AdIcd Mm-5 I'radtihiirgh. /Ivan A.: .\rl' nami' Factors InfluI'cinK Rotor BladI D(1 sIgI i for a U'tiity-(ass Hlioptr'. NASA

)vrall iltvr 'erfoirman'c,. AVrodyi7r17m7s of Rotary/ TNI-89129, AVSC(OM TM-87-3-8. 1987.Uh7/.. A(;AII)-( 'I'-I11. Fei/. 1973. pp. 7-1 7-11. 22. I3,,nder. Gary L.: Diekmai. Vernin .. : Attomecer..iliohni

6i Amtner. K,'r,'th B.: and Pro/ity. [a'yllond W.: Tchlh(Ii- D.: Pi'a.,so. Rarthohlmew D.. ]I: and Higgins. Larry I.:, \anc s it tl', All-fit Ap)a I(,/ Alvand('1 Attack Hft'- Engineering )esign Testl 1 YAI[-6.1 Advanced Atta'klicltr MOPh .117a/ An rual /rn oc, (d/1fdigs. ,.71'mca [ ( .- [Helicopter. USAAEFA Project No. 80-03. U.S. Arniv.

pt, t r S'o .. 19N3. pp. 55)) 56,S. .1au. 1980).

9

xz...... ..

LID

Z

Figure 1. Axis system used for presentation of data. Arrows denote positive directions of forces, moments, and

Floor area lowered 6.75 ftfor hover testing 12.96-ft-diameter

1rotor tested

Direction of flow

in tunnel for testingat forward speeds

< 22.4 ft 20 ft0>Figure 2. Plan view of test-section floor of Langley 14- by 22-Foot Subsonic Tunnel showing size of rotor area

relative to area of floor lowered during hover testing.

10

~Pitch SwashplateMain-roto:r \spring

Figre . keth o A-64fuslae mdelintaledontegrl rtor model sytm cGMofeLage

Reieach partiger.n

II

Figare Figret 4. AH-64 moelg oe with talnaed blade inale 14-o by2od sbsonic (teL nle

Reseach Cnter

Approximate flappingand feathering hinge Flappingangle

~instrument

Lead-lag angle

Cover plate to house Pitch case

instrumentation wiresand flapping :nstrument Lead-lag

hingePitch horn .i

_ 4 Lead-lagdampers Lead-lag link _

I,-90l-3 7

Figure 5. Model hill) wi h soic major components indicated.

TransitionBaseline rotor region

Twist = -9' 0.943R "

5.67 in. HH-02 airfoil C] 0

77.76 in.

NACA 64A006 airfoil-

Alternate rotor

RC(3)-1 0 RC(3)-08Twist = -120 airfoil airfoil

Modified RC(3)-10 airfoil " b kt

7.17 in.T

1 4 in

0.8R

Figure 6. Geometric characteristics of rotor blade.

12

12x 10-2

Scaled match

10 of full scale

8 Baseline

Rotor blade

weight, 6 -lb/in.

4

2 -Alternate Tip 77.76 in.

0 ~-0120 30 60 70 80

Blade station, in.

Figure 7. Rotor blade weight as a function of blade radial station.

12 -

10 - HoverForward flight

8

AC 0 6k 73improvement

4

2

-% I I I I

0 60 80 100 120 140

Airspeed, knots

Figure 8. Analytical prediction of performance improvement of alternate rotor compared with baseline rotor.SLS atmospheric conditions; f = 33.8 ft2 ; CT = 0.0064.

13

10x 10-4

10 -

0 BaselineEl Alternate

8

7z4.5%

6 improvement

CQ z6.4% improvement

SLS hover CT3

2

0 2 4 6 8 10 x 10-3C T

Figure 9. Rotor torque coefficient versus thrust coefficient for baseline and alternate rotors in hoverat 11til, 0.64 and H/d = 1.4.

1.0

z 6.4% improvement.8

.6FM . /' -S ILS hover CT

.4

0 BaselineEl Alternate

.2

[-3I I I I 102 4 6 8 10 x 10-

C T

Figure 10. Rotor figure of merit versus thrust coefficient for baseline and alternate rotors in hover at Mtip = 0.64and H/d = 1.4.

14

10 x10-4

0 Baseline9 ] Alternate

8

* 7

6 3.6%CQ improvement

C 4.3% improvement

4

N-SLS hover CT

2

0 2 4 6 8 10 x 10-3

CT

Figure 11. Rotor torque coefficient versus thrust coefficient for baseline and alternate rotors in hover atA =tip 0.58 and H/d= 1.4.

1.0

4.3% improvement

.8

.6 SLS hover CT

FM

0 BaselineEl Alternate

.2

I I I I I

2 4 6 8 10 x 10 3

CT

Figure 12. Rotor figure of merit versus thrust coefficient for baseline and alternate rotors in hover at Mtip = 0.58and H/d = 1.4.

15

10 x 0 Baseline

9 ] Alternate

8

7

6 2.4%improvement X2.5% improvement

4

32 -SLS hover CT2

1 1 I0 2 4 6 8 10 x 10-3

CT

Figure 13. Rotor torque coefficient versus rotor thrust coefficient for baseline and alternate r 'tors in hover at,11,i p = 0.51 and H/d = 1.4.

1.0

z2.8% improvement

.8

.6 SLS hover CT

FM

.40 Baseline]I Alternate

.2

I I I I I

0 2 4 6 8 10 x 10 -3

C T

Figure 14. Rotor figure of merit versus rotor thrust coefficient for baseline and alternate rotors in hover atMti p = 0.51 and H/d = 1.4.

16

Typical hoverthrust

80 0 BaselineEl Alternate

-1.5% of total60 rotor thrust

Fuselagedownload, 40

lb

20

I I I I I I I

0 200 400 600 800 1000 1200 1400

Rotor thrust, lb

Figure 15. Fuselage download versus rotor thrust for baseline and alternate rotors in hover at A/tip 0.64 andHid = 1.4.

7.0 X1-

0 BaselineEl Alternate6.8

CT 6.6

6.4 0

6.2624 .6 .8 1.2 1.4

H/d

Figure 16. Effect of ground proximity on rotor thrust coefficient for baseline and alternate rotos in hover atltip = 0.64 and CQ = 0.00048.

17

CL! 0T Full-scaleCL/ Gr gross weight

2x 10 -3 A 0.050 10 630 lb

2B .065 13 825 Ib

-__C .073 15 520 lb

0 V

1* flft 2k

f =20ft2

CD/T -2 -* f3ft 2 ] 7.4% improvement

-4 0 BaselineU Alternate

01 2 3 4 5 6x10 "3

CO/ OT

(a) /1 0.15.

CL/ m. Full-scalegross weight

2 x10"3 A 0.050 10 630 lb

B .065 13 825 lb

C .073 15 520 IbA

0 B

f =-l0ft2 0 Baseline[ Alternate

GDOT -2 - f=20ft2

f = 30 ft 2 <- 8.7% improvement-4

-6 0 -30 1 2 3 4 5 6 x 103

CQ/;T

(b) p = 0.20.

Figure 17. Rotor drag coefficient versus rotor torque coefficient at three values of rotor lift for baseline andalternate rotors in forward flight.

18

CL/ T" Full-scalegross weight

2 x1 3 A 0.050 10 630 lb

B .065 13 825 lb

C .075 15 950 lb0 A

B0 Baseline _,

-2 E] Alternate

CDIT- %

-4 = f 2 %t

2

-6 - 2.5%deficiency

-*f -30112

-8 , I , i I I * I * I0 1 2 3 4 5 6x 10-3

(c) p = 0.30.

Figure 17. Concluded.

19

u aTPP

A 0.30 -120

B .20 -908 -C .15 -7.50

8 C0.3% deficiency

_A6-

-10.4%improvement(L~e 4- "] C

- ;z9.3% improvement

2-0 BaselineI Alternate

I II I IL

0 2 4 6 8x 10 -2

CT/;T

Figure 18. Rotor lift drag ratio versus rotor thrust coefficient at three advance ratios for baseline and alternate

rotors (hub drag removed from calculations.)

20

1.2 x 10-3

4000 ft,1.0 9'

.8 0 Model corrected.8 SLS - Flight (ref. 22)

Vehicletorque .6

coefficient

.4

.2

I I I I I

0 2 4 6 8 10x 10 3

CT

Figure 19. Comparison of baseline AH-64 model rotor performance with flight-test results in hover. tip = 0.64;hover OGE.

.x 10 -3

0.8

.7

Vehicle 6

torque 0 Model correctedcoefficient 5 (ref. 19)

- Flight (ref. 22)

.4

.3 I I I I I I40 60 80 100 120 140 160

Forward speed, knots

Figure 20. Comparison of baseline AH-64 model performance with flight-test results in forward flight.CT = 0.0064; f = 33.8 ft2 ; SLS atmospheric conditions.

21

SReport Documentation Page

Report No. 2. (overnment Accession No. 3. Recipient's Catalog No

NASA TNI-4201AVSCONI TNl-90-B-015 _

•1 vl lh and Subtitle 7,. Report Date

Aerodynamic Performance of a 0.27-Scale Model of an AH-64 July 1990With Baseline and Alternate Rotor Blade Sets

6. Performing Organization Code

7 Aot hor,,)

Henry L. Kelley S. Perforning Organization Report No.

L-167259 Pertor ng Organizat i)i Name ad Address 10. Work Unit No.

Aerost ruct ures Direct,,rateSAA RTA- AVSCOM 505-61-51-10

Langley Research Center II. Contract or Grant No.

Hampton. VA 23665-522512. Spons ring Agency Name and Address 13. Type of Report and Perio)d C'overed

National Aeronautics and Space AdministrationWashington, DC 20546-0001 Technical Meinorandunn

andl 14. Army Project No.

U.S. Army Aviation Systems Command 1L162211AH7AASt. Louis, MO 63120-1798

15. Supplemnentary Notes

Henry L. Kelley: Aerostructures Directorate, USAARTA-AVSCOM.16. Ahstract

Performance of a 0.27-scale rotor model designed for the AH-64 Apache helicopter (alternaterotor) was measured in hover and forward flight and compared with ,n AII-64 baseline rotormodel. Thrust. rotor tip Mach number, advance ratio, and ground proximity werV varied. Inhover, at a nominal thrust coefficient of 0.0064, the alternate rotor used about 6.4, 'ercent lesspower than the baseline rotor. The corresponding thrust increase at this representative hoverpower condition was approximately 4.5 pe'rcent, which represents an equivalent full-scale increasein lift capability of about 660 lb. Comparable results were noted in forward flight, except for thehigh-thrust, high-speed cases investigated (Advance ratio = 0.30), where the baseline rotor wasslightly superior. Reduced performance at the higher thrusts and speeds was probably caused byReynolds number effects and blade elasticity differences. /-

17. bey '%ords (Suggested by Authors(s)) 18. Distribution Statement

Helicopters Unclassified -- UnlimitedRotor performance

Model rotor testingTapered rotor bladesGround effects

Subject Category 021. Security Classif. (of this report) 2(0. Security Classif. (of this page) 21. No. of Pages 22. Price

Unclassified Unclassified 22 A03NASA FORM 1626 o(CT s6 NASA-Langley, 1990

For sale by the National Technical Information Service, Springfield, Virginia 22161-2171