FILE COPY o. l-W

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MR Oct. 1941

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

"Tll lrl'I)II~ Ill~I)()Ilrl' ORIGINALl Y ISSUED

October 1941 as Memorandum Report

ADDITIONAL POWER.-DN WII'ID-rruNNEL mrrB OF

THE J./S-scAm MODEL OF THE BREWSTER F2A AIRPLANE

WITH :roLL-BPAN SLCYI'I'ED FLAIB

By John G. I.J::Nry

Langley Memorial Aeronautical Laboratory langley Field" Va.

NACA WASHINGTON

Ell COP~" To returned to tiI~1) ot me National

AdvIsory Gtmnttf8e for Aeror rautics

Washington O. C.

NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were pre­viously held under a security status but are now unclassified. Some of these reports were not tech­nically edited. All have been reproduced without change in order to expedite general distribution.

L - 708

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co o t­I

H

NATIONAL ADVISORY COlvttlTl'EE FOR AERONAUTICS

MEMORANDUM REPORT ,

for the

Bureau of Aeronautics, Navy Department

ADDI'rIONAL POWER -ON vIIND-TUNNEL TESTS OF

TEE 1/8-SCALE MODEL OF THE BllEWSTER F2A AIRPLANE

"WITH FUL:L-SPAN SLarrED -FLAPS

By J ohn· G. Lowry

INTRODUCTION

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Additional tests as recoDitnended in reference 1 were made in the 7- by' lO-foot Ivind tunnel of the liB-scale model of the Bre'vster F2A airplane to determine the angle of attack of horizontal tail and the elevator angles requir ed " for 'trim with flaps dOiyn.

MODEL

The l/8-scale model of the Brewster F2A airplane with the modified wing and full-span slotted flaps is the same as was used for the tests reported in reference 1. Three-view drawings for the complete model and the modi fied wing vTith "full-span flaps may be found in references 1 or 2. All the surfaces vTore set in the maImer described in references 1 and 2 .

The same electric motor was used as in the previous tests. The propeller used in the subject tests, however, had two blades instead of three or s ix, and had a 13 per cent larger diameter than in the preceding tests . Since the propellers used in the previous tests were 6 percent larger in dia,meter than the Beale size for the prototype, the two -blade propeller was 20-percent oversize in diameter. These larger blades were used since the blades used in the previous tests wei'e no longer avai lab;J,.e at t he 7- by lO-foot vrind tunnel.

2

TESTS ' AND RESULTS

The test conditions in this series 01' tests w'ere the same as descri 'bed in reference 2.

Co.§f.fic,ients.· The results are 131 ven in at ndard coefficients as described in ref er ence 1. The propeller advance diamoter ratio V frill io based on the t"10-blade proIlel1er diameter D of 1·5)1- feet . The same correction,o "lel'e apT)lied to tbe test results as ~"ere applied j.n the previous investj.gation.

Test....1rtQ.9..Eldur~. · As in the pre'liou8 tests, propeller calibrations \'lere fir-s t made " The two -blade propeller characteristics 81'e presented i n fignre 1 for ~ = 200. The same procedur.e "TaS used as described in reference 1 to obtain t he operating charts f or the model . Fig -ure 3( a ) of ref erence 1 "las again used to obtaln the prototype thrust coe.fficients .

For convenj,ence in locating resnlts , a resume of the tests is gi ven in the foll o"rinS table:

~~--------------------~--~---------.-----~~--~----~----------~----___ ~f

L-708

Test POi-Ter No· prop . p of ° or iT 'Ijr Type of

Model condition Figure No. condition blades e · t est

27 ----------- 2 20 0 0 0 -0·9 0 Thrust Complete model 1 .. calib . 1 28 '2 Rated 2 20 '1-0 0 o . -.9- 0 Pitch -----do------- 2,3, 5,6 . . 29 ----do- ---- 2 20 40 0 0 -2 .1 0 --do-- -----do---- --- 5 30 ----do----- 2 20 !J·O I . -5 0 -·9 0 --c1o- - - - ---do-- - --- - 3 3l ----do----- 2 20 40 -10 0 -· 9 0 --do-- -- ---QO------- 3 32 ----do----- 2 20 40 0 0 ·7 0 --do-- --- - -do--- - --- 5 33 ----do--- - - 2 20 40 --- --- - - -- 0 :--do- - Complete model 6

minus horizontal '. tail

3! ~ 1,[indmilling 2 20 40 0 0 -2.1 0 --do-- Complete model 7 35 ----do- --- 2 20 40 0 0 ·7 0 --do-- ------do------- 7 36 ----do----- 2 20 40 --- -- 0 --do-- Complete model 7

minus hori zontal

I I I I I I tail , - !

tAl

4

DISCUSSION

~pe of pro~ell~r.. - The effect of changing from the three -blade propellel' (D = 1.36 ft ) D.sed in reference 1 with f3 = 300 to the two-blade propeller (D::: 1 . 54 n) used in the subject tests i,rith 13 = 200 is shOlm in figure 2 . Changing from the throe -blade to the two -blade propell er increased the sl ope 0,( the pitching­moment-coefficient curve a small amount . The change in the slopo of tbe pitching-moment-coefficicnt cux"J'c is probably caused by a change in the do'Wmlash and q distribut ion at the wing and tail, 8ssociatea, with the change :Ln propellers. The increase in l i ft may be largely clue to a small variation in f lap set.ting and angle of attack . 'l'he variation ill resultant drag is probabl y caused by a slight variation in pl'opeller rpm.

Ele7ator deflection. - '1'he effect of elevator" def lections is shown in fig\.;;:::;- 3 for the model wi th 1/2 rated power , the' flaps deflected, and the landing gear ey.tendecl. . The d.ecrease tn longi ­tudinal stability dem/deL with up-elevator de,ne'ction has been found in previous pOHel' - on tests m~de at the 7-- 'by .l O- foot w'ind, tunnel . The decrease in dCm/ dCL w:L th up·-6J.evator . deflect l on is

probably the result of the ch~l1ge in the q.irection of the : load on the tail along id th the retio of 'the change in d:m-lllwasil and dyn8m1c pressure at the taU with increasing 'a!lgle of attack,

The elevator angles f or trim are given in figure 4. 'f01' ·'the : model with 1/2 ra'ljed power, the f l aps deflected,, ' an " the landing gear extended . 'rhese ele vator 8l1,~,:l ef3 \Vere 11 te:cpolcrted from the d.atEt in figure 3· In reference 1, it 1{as pofnted out that it was not good practice to extra:polate to obtain elevator tr:lm 8l-lg1es .. The angles

1° 0 for trim in figure 4, a:te 12 to 2 more positive. than the values

given in reference 1 .

~ of a't!tack of taiJ.:.....§.urfa£Q. - The effect of small stabilizer deflecti ons is 8i ven in figure :, for the model with 1 /2 rated power and flaps deflecterl. Figure 6 8i ves the effect of hori zontal tail on the aerodynamic characteristics of the lilodel vTi th 1 / 2 rated power and f laps deflected. The effect of small stabilizer angles and hori zontal tail is shown in figu:ce 7 for the model with propeller windmHling and with flaps deflected.

The stabilizer tests (figs . :5 and 7) shm.; that the change in pitching-moment coefficients ,·rith stabilizer angle dCm/diT increases with the applicatloll of 1101ver. The value of dCm/ dj.rr for propeller windmilling 0.020:5 agrees vri th the value used in correction of pitching moments for tunnel effect .

t-i I

-J o co

5

The angle of attack of the horizontal tail is shown in figure 8 for the model ",ith flaps def lected and landing gear extended for both 1/2 rated power Dnd 'Yrindmilling propeller. The values ClT were obtained by dividing the 6Cra caused by horizontal tan by

<g the value dCm/ diT for the incUvidual conditions. Since a tail ~ surface stalls at angles of attack of approximately 150 , these H data show no indication of tai l stall.

An analysis of the sub ject data indicates that a larger hori­zontal tail is desirable for the airpl ane with full-span slo·tted flaps.

Langley Memorial Aeronautical Laboratory , National Advisory Committee for Aeronautics,

Langley Field, Va., Oct ober 27, 19)·~1 .

REFEHENCES

1. Low'ry} John G. : Pm'Ter -On Wind-Turmel Tests of the 1/8-Scale Model of the Br "ls ter :8'2A Airpl ane with Full-Span Slotted Flaps . NACA MH, AUf . 21 , 191 ~1 .

2. Lowry, John G.: Povler - Ofl ~'Tin "Tunnel Tests of the l / ,'3-Scale Model of the Brc'YTSter lI'2A Air plane. NACA MR, June 2;1., 1941.

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