Effect of powered propellers on the aerodynamic characteristics and the porpoising stability of a dynamic model of a lon...

MISSING IMAGE

Material Information

Title:
Effect of powered propellers on the aerodynamic characteristics and the porpoising stability of a dynamic model of a long-range flying boat
Series Title:
NACA WR
Alternate Title:
NACA wartime reports
Physical Description:
4 p., 3 leaves. : ill. ; 28 cm.
Language:
English
Creator:
Land, Norman S
Langley Aeronautical Laboratory
United States -- National Advisory Committee for Aeronautics
Publisher:
Langley Memorial Aeronautical Laboratory
Place of Publication:
Langley Field, VA
Publication Date:

Subjects

Subjects / Keywords:
Seaplanes   ( lcsh )
Aerodynamics -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Introduction: The tests described in this report were made on a 1/8-full-size model of a large, long-range, twin-engine flying boat in NACA tank no. 1. The airplane had a wing loading of 43.9 pounds per square foot and a power loading of 11.5 pounds per horsepower. Its arrangement was such that 34.2 percent of the wing area and 56.1 percent of the horizontal tail area were included within the fore-and-aft projection of the propeller disks. The model was fitted with leading-edge slats to make the angle of attack for maximum lift coefficient correspond with that of the airplane at the low Reynolds number associated with the tank tests (3.28 x 10⁵ based on the mean aerodynamic chord and the get-away speed of the model). The model was equipped with two three-blade metal propellers of scale diameter and form, power for which was furnished by two variable-frequency alternating-current motors. Sufficient power was available to develop scale thrust with the propellers. The tests were divided into two parts: (1) aerodynamic tests to determine the effect of the slipstream and thrust from the powered propellers on the lift and trimming-moment characteristics, and (2) hydrodynamic tests to determine the effect of the powered propellers on the range of stable locations of the center of gravity.
Bibliography:
Includes bibliographic reference (p. 4).
Statement of Responsibility:
by Norman S. Land.
General Note:
"Originally issued May 1943 as Restricted Bulletin 3E13."
General Note:
"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."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 003805116
oclc - 123911838
System ID:
AA00009444:00001

Full Text
K L-Q3C


RB No. 3E1'


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS





WARTIME REPORT
ORIGINALLY ISSUED
May 1943 as
Restricted Bulletin 3E13

EFFECT OF POWERED PROPELLERS CO THE AERODYNAMIC
CHARACTERISTICS AND THE PORPOISJNG STABILITY


OF A DYNAMIC MODEL OF A LNGG-RANGE FLYING BOAT
By Norman S. Land

Langley Memorial Aeronautical Laboratory
Langley Field., Va.






r rg


WASHINGTON
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 235







I-.-b 'I I


NATIONAL ADVISORY COM1'IITTEE FOR AERONAUTICS


rE.SThICTED BULLETIN-


EFFECT OF POWERED PROPELLERS 0O TFi AERODYIIAMIC

CHARACTERISTICS AITD THE PORPOISING STABILITY

OF A DYNAMIC MODhL OF A L01TG-RANGE FLYING BOAT

By Norman S. Lnnd


IITRCDUCTION


The tests dpscrib-,d in this report wrre made on p
1/8-full-sizr- model of .r lere,, long-range.-, twin-engine
flying bopt in NACA tenk no. 1. Thr airplane had a wing
loading of 4,3.9 pounds per squr- foot -nd a power loading
of 11.5 pounds per horsepower. Its arrangement was such
thnt 34.2 pprcrnt of the wine arpn end 5C.1 percent of the.
horizon l tail arm. wr include d within th," fore-end--ft
projection of the propeller disks.

The mod.-l wa-s fitted with r d ing--deo sl1ts to makr-
thr anglo of pttpcx for -:,ximrum lift cooffici- nt correspond
with th.it of the airplane .t the low Reynolds numbr-r asso-
ciated with the tpnk tests (3.28 x 10 bFsed on the m~en
a.orodynamic chord and tho get-r.w'y speed of thp model). The
modr:l was Pquipped with two three-blad? r.ptal propellers of
scr.l diameter and form, power for which was furnished by
two varinble-frequency altrrnnting-curr.-nt mnLtors. Suffi-
cient Dowur was available to dev,,lop scale thrust with the
propellers.

Thr tests wore, divided into two parts: (1) a'rodynaLic
tPste to deter -inr-- the effect of th,- slistrepu and thrust
from th.- pow.-er d pr.prll.'rs on t*.*- lift and trimmingn-mom.-nt
characteristics, and (2) hydrzdynnqaic tests to dcterm.inr the
effect of the, powered propellers on thr rpnge of stable lo-
cations of th-3 center of ,ravity.


sA.RJ3D YLAIC rESTS


Aerodynamic tc-sts were :id, by suspending the model
above, the water with th. tri., nxis at a height that allowed










a small clearance of the stern post at a trim of 160. The
trim axis was located at the point corresponding to the
position of the center of gravity at 25-percent mean aero-
dynvmic chord and the trimm.ing-moment coefficients were
measured about this axis. All aerodynamic data were obtained
at a constant speed of 45 feet per second.

In tank tpsts of powered models, the effects of power
are assumed to be approximately simulated by dimensionally
sealed propellers turning at a speed that will cause the
propellers to develop scale thrust. In the case of the
present model, the values of thrust assumed and the corre-
sponding propeller speed, as determined from a calibration
of thr model proprellers in a wind tunnel, ware as follows:

Propeller speed
(rpm)

Z-rzo thrust . . 0
Onn-half of scal-' thrust at V= 35 fps (model) 4200
.Full static thrust . 4700
Full thrust at V= GO6 fps (model) .. 5300

The curv.'s of aerodynamic lift coefficient against
trim L .nd .trim.inrg-.1oLent coefficient giv-n in figure 1
show that the change fro-i zero thrust' to or.--half af scale
thrust has a relatively greater eff-c.ct on the aerodynamic
characteristics than the change from one-half of scale
thrust to full thrust. Also, the curves show that the dif-
ferences between the characteristics with prorillers turn-
ing at 4700 rpm and a-t 5300 rpai are negligible. The last-
mentioned conclusion is significant in that continuous
adjustment cf the propeller speed of the model during an
accelerated run appears unnecessary for simulating the vari-
ation 6f thrust with speed of the full-size propellrers.


HYDRODYNU.MIC TESTS


Details of the test procedure used to determine the
range of stable locations of the center of gravity aay be
found in reference 1.

Figure 2 shows th-, lrge difference in tho stable
rang-, between half-thrust and full-thrust conditions. For
the nydrodynamic tests, full thrust was represented by a
propeller speed of 5000 rpm. The principal effect af in-













creasing the thrust front half (4200 rpn) to full (5000
rpi.) is to shift both thl forward and th- after li..its of
stability aft. The after limit is :L.vcrd pft to a auch
lsser degree that the forward limit.

Thrne effects of pow-r nar, inv-lv.'d in the. location
of thp stable rang- .f thr- c2nt.,r of gravity. First,
thm slipstre-.u ov.r th-- wing causes an i2icr-asp in the
lift and a decrease in the l -"d :n th-- wAter. The trim
limits of stability are thus rrise.? to higher tri;.-i. (S? r.
reference 1.) Sec on' thi-- thrust pruducr s a nose-1 own
on:mi toruilning th r rang.,: of st.r.bl" lc 't ions tf the, center f
gravity. Thire. thr. slipstrn ..: on th tril ch rng.es th.
mco rnt produced by theo toil an)r incre-.ss -s th'- -fff'ctive-
nfoss of th ,'lr-rator.


CDITCLUS IC S


1. Whpn the hyv.r ad.ya-.ic st. ability of a flying b-at
is -1 tt r:..inrd by L- nr.s of tested 'f r dyn-".ic iol'--l, the
scaln thrust should" if pULSsible, ber ?cv lope. by :. "cns of
opnrrting; propollrrs of at le-.st appr xi .?tely scnal diajn-
etOr. On a :..:fl of r i",n,-r nige flying bcj-t of conv'-n-
tional design, l:rg. increa-ses in wineg lift anr' t il i:oozent
mijay b? *-xp ct .--- to f ll :.w tn' usii ,, f p :*;er .d r r:'p-ll-l rs.
In addition, the thrust zi.ur nt c.nsirerabiy changes th2
tri:as assun.=d by thr flying bt:t. Thejrsn -ffrcts gre-tly
influence th '.ir'th of th0- range of stable lc:ntions of the
center of gravity.

2. With the present u.'th s f et: -r ...inin thi- stabil-
ity of d.nr'-n-mic :.,. '1ls, 'xrct s i..ulation .f full-siz,': vari-
ation of thrust with sp t,'. is unn:c-ssar;,y.


Lang- ly Mr nor il A-r onsut i c 1 L:b orst or.y',
Yp.t i onnl IA'vis ry C n.it tee f r a-r onaut ics,
Langley Fir d, Vr..











REFERENCE


1. Olson, Roland E., and Land, Norman S.: The Longitudinal
Stability of Flying Boats as Determined by Tests of
Models in the NACA Tank. I Methods Used for the
Investigation of Longitudinal'Stability Characteris-
tics. NACA A.R.B., Nov. 1942.





NACA iF ?ig. la



2 -6- -- t---- --
2,, 6


2.4 --- --1 -- .. .

.... ]--- --/ .--1 ----K--.--.. .-/- r'

2.2 --





/ I I _

o-50 r .--













I 2C-- r 4-
._l_ -.o / 1 --- ---'- ......














LLl
1- i1 -', e I pI" -- l- n--r--- -I_---




S. 12 1E 0 -.2
/ '/ 7 /
1.6,-- -- .... ..-- --1 I ... --' _



b I y i 'F/"


Trim, Tri in-m nt efficient, C
(a) levat--- ors n tral
^/--- --- -. --^ -- --
/ -- -- 5o00 rr y '
-- -- .. ... -- -- i7c,:j rp.'. --- /- --..-- -- --- --. ..

.3. --- ,r oil.... _-.o ,, __+ ____
I / 1i
--Fiz.ur ',b)- Ef'fct ci" p-i.ered or -oe1itri n t-. h edrc&J'.,," ,ic --
chcracierisLics .f oyie..,ic a,;dtl. |
.6 I. II IiI 1I
9 8 12 16 0 -.2 -.-
Trim, d Trimnz-,in&-mcrn~nt cc.efficient, C(
(a) Elevators neutral












2.6





2.4





2.2





2.0




1-.
*.
U
.4

0
01.6

.-4


1.2





1.0


Sriars de
(b) Elevators 25" uo


IL 0 -.2 -.4
Trii.ming-mImn.t coefficient, CM


Figure 1.-(Concludjd)







NACA Fig. 2










24--- ---- -------
22 --

I I i


-' 4
12 -- -+------ ---}----









tt II
I I Irra .ai ar I sili

24 2b -32 40 44















Crt 1 f- rev i 1. cr t i c n percent ..A.C.


ibure 2.- Effect of ,nicrad ur- r-.11srs r: thj lilidLs ?f stable
lo I tiI t f i
,, \ ^I l iii. I r i I



I ... -- __________.___ __,
oY rw r ft l "it,
,- I --------{----,J--------










ifur' 2.- E21tr ct .,f {rv/crid nr'oCj lrs r f. the lir.ir.s .f stable
"ocf\ti rns n -,f tie c-_n_ _r cf gr : ,it cf r- d2n3jnic




U OF FLORIDA A :

I ....I..IIR...I..I III ...ll

.'*:

UNIVERSITY OF FLORIDA
DOCUMENTS DEPARTMENT
120 MARSTON SCIENCE LIBRARY
RO. BOX 117011
GAINESVILLE, FL 32611-7011 USA

'.



"ii












"":i E iii:
....... *B
":"', 8i