Lowry, John G

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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 pre-
viously held under a security status but are now unclassified. Some of these reports were not tech-
nically edited. All have been reproduced without change in order to expedite general distribution. 
L - 708 
https://ntrs.nasa.gov/search.jsp?R=19930093665 2020-06-16T23:43:57+00:00Z
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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 
---"-~--
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 pitching-
moment-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 . 
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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 hori-
zontal 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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Additional Power-on Wind-tunnel Tests of the 1/8-scale Model of the Brewster F2A Airplane with Full-span Slotted Flaps

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