The influence of vertical-tail design and direction of propeller rotation on trim characteristics of a twin-engine-airpl...

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Material Information

Title:
The influence of vertical-tail design and direction of propeller rotation on trim characteristics of a twin-engine-airplane model with one engine inoperative
Series Title:
NACA WR
Alternate Title:
NACA wartime reports
Physical Description:
24, 26 p. : ill. ; 28 cm.
Language:
English
Creator:
Pitkin, Marvin
Draper, John W
Bennett, Charles V
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:
Airplanes -- Testing   ( lcsh )
Aerodynamics -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Summary: Tests have been made in the Langley free-flight tunnel to determine the influence of mode of propeller rotation and vertical-tail design upon the trim characteristics of a model of a twin-engine airplane with one engine inoperative. The test model was mounted on a trim stand, which allowed freedom in roll and yaw under conditions simulating those required by the NACA and the Army Air Forces for asymmetric-power operation in flight. The seven vertical-tail designs tested included three tails of low aspect ratio and of different area, one twin tail of low aspect ratio, two tails of high aspect ratio and with different rudder areas, and one all-movable tail of high aspect ratio equipped with a linked tab. All tests were made with the flaps down.
Bibliography:
Includes bibliographic references (p. 22).
Statement of Responsibility:
by Marvin Pitkin, John W. Draper, and Charles V. Bennett.
General Note:
"Originally issued February 1945 as Advance Restricted Report L5A13."
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 - 003804754
oclc - 123896964
System ID:
AA00009378:00001


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Full Text


ARR No. LcAl


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS





WARTIME REPORT
ORIGINALLY ISSUED
February 1945 as
Advance Restricted Report L5A13

THE INFLUENCE OF VERTICAL-TAIL DESIGN AND DIRECTION
OF PROPELLER ROTATION ON TRIM CHARACTERISTICS
OF A TWIN-ENGINE-AIRPLANE MODEL WITH ONE
ENGINE INOPERATIVE
By Marvin Pitkin, John W. Draper, and Charles V. Bennett

Langley Memorial Aeronautical Laboratory
Langley Field, Va.


. NACA.


,I '


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 191






































Digitized by the Internet Archive
in 2011 with funding from
University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation


http://www.archive.org/details/influenceofverti001ang










NACA ARR 1o. L5A13


NATIC: .-. ADVISORY CO73i"ITTLE R AR -5?1i TICS


A';.:r5 RESTRI~D DEP Ti




-- T } TC





By -.:'vin Ei tki, Jn '..r Tae, an: Chrle V. Eern-ett





etts havLe bee r it.de iti the Ln -~ fre-fllrt t tunnel
to determined het r'nflucrce ?r T:de 0o pro r llir r:tat'rin
and vertical-tall. de '.[ on"., o. the tri; characteristic of
a model of a ttvin-en'o.e arrlanc vthc ore i ine 1in3c r-
ative. Te test rl-.l ';as mun-'te1 on a tr -: sttan, sWich
allow ,ed fr~ dorl n r:ol nrd aw:: 1 :.cr corniltsns sia'ul t-
ing th'- e r. 'uiri b. "lie -.'.i<- t. 1.:. i: Air .:,rcC for
as)nxtric-r.*'r ::-ea.tin '.n fl .;-.,t. cThe sev n "ertical-
tail de1si:'n ttC ine] r:1 t'hr'. ti. f ow -ct
rati? and of diffr ent aR:, one twvin tt'1 of lo v aspect
ratio, t-wo tails of Cnix r a-" ct r.t -.i v t h ;. 'f i r .t
rudder areCa;:, and c~e Ial-:.ovable tf4 Lof hifh asy ct
ratio (cui c ca '.:ith a ir' tab. A 1 tc rts v.-ro r: ad
with tihe flaps do:v.n.

The tcn.ts sh v: :'d c~Iat t!e, o.'ct of rr t. of ..ro llEr
rotation unon tne dir ct'. onal tr. r char'.ctcr- tir s of the
model operation with i y' : t;- pr-.ic 'o.>iver '.,:-* concidterblC .
Pr-cell r rotation :n C' ch x re ir tr' .'tat.t cu-t-
bomard tc'ard th iina tip (outoP ~r'd rotiti:-n) t p n- rally
cr- ted mo o"evrer o'i t-of-tri. c lndiit rns t l.n inboard
rot nation.

a 1 all-rovable tall dei'-n w:eo fornd to be more
effective th n the other d -n eted in ril lif-ine the
effects of anymmeteric per. ..x eo c on. t'i on:. tail de-
slir s with h high apct rTatio fl e ror3 ciffctive than the
designs with low : a.sec raltf- in t:ii respect. -i" -1ing:le
vertical tails vre n encrall]- r m ff -ct ive I t'-rnt-i
the yawi"r- :i.:.cnto created <..; cattrc p-':'er than
t:.in vertical tails of tCe 4 'ars ace t riat!) and eoual









!TA, A ARR I'o. L5A13


are'a, particularly en t the ridder swas free. At sr.all
anile- of si desli however, the Toneiets caused by
a .m-,r;etr c nover were more PradilyT tr.red by deflecting
tE- r iocrs of the twinL tail- than by d-eflarting the
ruCder of a single taIl.

The tr urmini eff-ectiveness -f tie vertical tail in-
cr aseo al:mot dtrectl; with vertical-t,.il area but in-
crteased at a decreas', rate wi L rudder deflection and
chord.

'hen the rudder was free, the addition of dorsal-
aId v-itral-fin areas permitted incire .s 'n the asyrm-
mptric Zowr balanced by t+.c tall surface at moidrate
anrl es of s Gesl 11.


IL2 YT'.0i L


The fa'l".re of one or im:re erlines of multioerine
airplanes introduces a pudder and severe de ..rd upon the
direct'aonal ta ..-'ity aru- cltrol of those airplanes.
Such f allure' r- lt In the n stal..tans;.o- application of
larre r'..wip- mromerts that muivt be reut&rill,, e e'.clher ob
the ruaicer control or by tc directional statilt of the
airplane. In addition, asvyinmrtric power conitftion create
r:-l n:.: n mrTnn'1 that :ut be bla d lnce -by ailron reflection
in order to rainta!n straight flj bt. This aileron de-
flection ce"te *dittioal a- vn.i n; mLntS that require
further trirnir. by ttie vertical t cil .S'rface. For multi-
engine airplares, then, the as ..'-:r-'o Ioier condition
fr'lrall" i'-rm sesn the ';st severe renauire'ent7 for dl-
rectional stability and ccntirol ana to a larpe extent
dictates the desi' of the vertical tail surfaces of these
airp ane s.

An i nvr:'tifaton ha theref.)rc boern carried out in
the Lan'2ley iree:-flith t nnrl to pr) ) ide data concerning
the rel tive r.eri:t of S'even ver cical-a il decirns and
twvo rodes of propeller rotation unli r cnd.it.ions of asyn-
cric oer. The .'AC and _Ar .' ,yin 1-qualities require-
wEnt. (refer(fnc7c 1 and 2) 'or directional 1stabl ty and
c-ntrol of airpl.re r op rati jnl: w':it a.S: !7metric Dower were
J"ed to, establish the tcst c n(dibions. ve-. resul.lt of the
i3vc stifati n arc reo rted h,-re n.









NACA ARR No. L5A1l 3


A ---cale model of a conventional twin-engine air-
planr: ini the redium-bcter class (the icrtih Aerican
B-2S airplane) was used in the tests. The rodel was
rnUnted onr a test sta.d, w hi.ch allowed ..reed om in ya and
roll. The effects of asymmetric power could thus be visu-
ally observed from changes in the roc.3l attitude.

seven vsrtical-tail desi-ns studied in this in-
vestigation varied in either aspect raeic, total tail
area, rudder area, or pererar arrTe-r t. t Tests were
made w~ith rudders fixed and free, and the effects of
adding various dorsal and ventral fin- ;ere studied with
the rudders free. ",-- effect of mode f7 rotation of the
oferasing propeller u on the vertical-tail characteristics
was investi._ted for all tail arrancsr-c ts. All tests
were mAde with the flaps down.





CT lift coeffici2nt t l.t\

C rollinr-moinent coefficient -Roll
c' I/ "e"a-ir rc"rent
Cn -yawing-momi ent coefficient ( -,. n

Cn rate of chane .of ,-:. .-n- ..o -nt coefficient

with an:le :of sideslip C

T thrust coefficient f-r one e .: e 7-


D pr.- 'ller diameter, feet

p density of air, slug per cnic foot

V free-stream alrspeed, feet per second

VLvtf elfcity at end of take-off run, feet per
second

Vmin stallinrc peed with flaps -.__-n, feet per secor'

q free-stream dynamic pressure, pounds per square

foot pV2)
(2









IaiCA ARR Io. L5A13


T effective thrust of one en-rIne, pounds

Spropelrler efficiency, percent

pros S3 v.'el-ht, poundo

3, wirc airea, s-1uare fe-t

bhp trake hor sepcwer of full-scale airplane simulated
by odel
thp thrust hor epov.mr

La coI' ned a'ler -n -*eflection, d'.erees

pr n.-dler deflection, t positive when trailing edge is
to left, dercee

6f flap deflection, positive ei nten trailirf edge is
do3:n, depfreer

6 elevator cdflercton, degreeC
e
6T tab deflect'on of all-niovable t .il, positive
when trailing" edFe is t.o lef., derees

1t tall incidence oP all -rrvable t.l ith respect
to center line of fuselage, degrePs

a an'-le of attack, degrees

at local anorl of attack of vertical] tAl, d,- I-es
S an--le of C'ci p, degree
/ 2/ t
A a -tct ratio -f v:-tical tail (b /S3

St area -c vertical tall) sq are fet

b tbalTnce a'~(n rud cr, **t.rc L rudder area

S rud r arC ar: fer t

b. rn-. f -;i rr:al tail, feet

b win_ span, feet










::ACA ARR No. L5A13 5


APPAR/A /3

Wind Tunnel


The tests were -ade in the Langley free-flight tunnel,
a complete description of vw"ich will be found in refer-
ence 3. The tunnel was locked at an angle of pitch of 0
for all tests.


T'. 'r. Stand

All tests were made on a tri. stand, which was
securely fastened to the floor of the wind tunnel. This
stand was so constructed as to allow the model freedom
in roll and yaw about the stability axes of the model.
The stability axes are a system of axes in which the
Z-axis is in the plane of symmetry of the airplane perpen-
dicular to the relative wind. The X-axis is in the plane
of symmetry perpendicular to the Z-axI.s. The Y-axis is
perpendicular to the plane of ..-t.;. 71 e origin of
the stability axes is at the center of gravity of the air-
plane, which for the present tests was located on the
fuselage center line 25 percent of the mean aerodynamic
chord behind the leading ed_-.

rFh:tographs of the model mounted on the trim stand
are given as figure 1 and the construction of the stand
is illustrated in figure 2. Fi, i.re 2 shows that bearing: A
permits frd-'J-- in roll and bearing B permits freedom in
yaw. A calibrated coil spring was inserted in bearing; A
to provide stability in roll. 1is alteration made pos-
sible the measurement of unbalanced rolling moments as a
function of the angle of bank and thereby facilitated the
trirr:.ir.; of these moments by means of aileron deflection.
Both bearinr-s A and B were equipped with ball bearings to
keep frictional effects to a minimum.

The trl-..l.- fin shown in f: '.i e 2 was added to the
trim stand to neutralize the drag yawing moments caused
when the ...ind was on by the forward struts at an angle of
yaw. Since this fin area was such that the trim stand
was in complete equilibrium of yawing moments ( 0)

over the yaw :1..-e tested, the trim stand did not affect
the directional stability characteristics of the model.










6 ::.-.A A. No. L5A13


oh del

-'e mod(e used in the investigation was a __-scale
20
model of the North Am.rican B-28 airplane. A three-view
drawing and a photoPraph of the model are given as figures
3 and 4, respectively.

The model was equipped with 2 four-blade propellers
having a diameter of ..L0 inches and set at an angle of
pitch of 20. Power was furnished by a direct-current
controllable-soeed electric motor rated 1/8 horsepower
at t1,000 rpm. The left propeller, which was kept in-
operative during the tests, was so mounted as to windmill
freely. The right propeller, which was used as the oper-
ating propeller for all tests, was geared to the motor at
a ratio of 1:3. Provision was made for reversal of the
direction of propeller rotation. The model was equipped
with partial-span slotted flaps (fig. 3), which were de-
flected 450 for all tests.

Sketches of the vertical-taJl designs used in the
investigation are shorn: in figure 5 and sketches of the
dorsal- and ventral-fic areas utilized in the rudder-
free tests, in figure C. 1 2 repr cents the original
vertical tail surface of the full-scale all-lane and is
considered typical of conventional vertical-tail design.
The dinmnsional characteristics of this tail were varied
to form the other vertical-tail designs. All vertical
tails were constructed of the NACA 0012 section. In
order to rrma'ntain similitude of hinjee-rmoment character-
istics as far as practicable, all rudders were of identical
blunt-nose balance ty:e with a balance area 12.2 percent of
the rudder area. This type of r- der is of negative float-
ing tendency and trails with the wind. hen free.

The dimensional characteristics cf the full-scale
airplane are given in the follonirnr table:



AS-r ft ...................................... .61
ct r ti ft................. ................. ....... 7.8

io t chord .n. ............. ... .. ............ 161.13
T pi hrc, in ................................. :.' ,1.
ran aerodynamic chord, in ....... ............. 12-.09
Root section ................. ... ... .......... '::.,CA 23017










..C..A AFR No. L5A13


TFp Se. ti x .... ... .t ... IA.. CA 4. .9R
oErceri chord line vith zero swv.ee'-:back ...... ....


Sweepback at leading edge,
Dihedral angle, deg ......
Incidence, deg ...........
Geometric twist (vashout) ,
Taper ratio ..............


deg ................... 4.2
.......................... 2

deg ................... .5
.......... .......... .4 :1


Pus ela:e:


Length, ft ...............
Section ..................
Frontal area, sq ft ......


................... Circular
..... .. ............ C


Horizontal tail:


Total area, cq ft .................. ........ 183.20
Span, ft ....................................... 2 .
Apect ratio ............... ............... .94
Dihedral angle, deg .................... ....... ... 0
Stabilizer ettin deg ................ ......... l.
Lergth from hinge of elevator to center of
gravity of airplane, ft .. ............ .... .90
Elevator balance area, sq ft ................. 10.63
.Eevator area behind center line of hi". ~., sq ft E


Total area, sq ft ...........................
S ar,, ft ................... ...... .... ........
Aspect ratio .. ...............................
Length from hingr e line of raider to center of
gravity of airplane, ft ...................
Fin area, sq ft .............. .............
Rudder area, sq ft .......... ..... ...... ........
Rudder-balance area, sq ft .......... .......
Rudder area behind h':.-. line, sq ft ...........


74. 0
10.68
7. 4
. ] .54

27.40
35.24
39.24
. 3.14
30. 0


(Pertinent data for tails 1, 3, 4, 5, 6, and 7 are given
in fig. 5.)

A'leron (one of two):

Area behind h1:-.- line, sq ft ................ 20.91
Soan, ft ....................... ................ 111
Mean chord, in. ................ ................ 17.0


Vertical tail 2:









8 1.:.J3 ARR No. L5A13


Flap:

Total flap area, cq ft ................ ...... 230.3
Total span, ft .............. .... ................ 38.4
Tyl- .......................*... .. ........ ...... Slotted


SPECIFICATIONS AND CRITZERICS


The :7ACA and Army flight requirements for multiengine
airplanes operating with asymmetric power were chosen to
establish the proper test conditions. :o separate attempt
was made to reproduce the Navy specifications for asym-
metric power because of the close similarity between the
'!:.vy and the NACA specifications.


Specifications for Directional Control

(Rudder Fixed)

The "CA and Army specifications (references 1 and 2,
respectively) for directional control of airplanes operating
with asymmetric power are as follows:

A.CA requirement ( 3I-7) 3.- 'The rudder control should
be su-:..Cci. i. : f: i r provide equilibrium of yawing
moments at zero sideslip at all speeds above 110 percent
of tne minimum take-off speed under the follc'"i.:- conditions:

a. Air -lane, with two or three engines:
With any one engine inoperative
(propeller in low pitch) and the
other engine or engines developing
full rated power.~1

Aryv re airement E-2c(l) (c).- "The rudder control
shall t .. ef: :.... : t t a multi-engine airplane
for straijiht flight with less than 10 degrees of sideslip
at 1.2 Vq V : stalling speed of the airplane, throttles
.Vsh Sh
closed, en.ar down, flaps ~n best take-off condition when
the throttle on an outboard e --ne is abruptly closed
propellerr in low pitch) and the other enFine or engines
are dcvveloping fL'll tnke-off power. The flope shall be
in the take-off setting, and the gear shall be down...."













Specifications for Directional Stability

(Ruader Free)


he NASA -:ecificaticn (requirement (TTI-) 4 of refer-
ence 1) relating to the reouiremeneC for directional sta-
bility with rudder free under as -tric rower cond tions
is as follows:

"The yawing moment due to sideslip (rudder free with
airplane trimmed for straight fli ht on -yrmmetric poer)
should bfe such that strcaiht liht can be maintained by
sidesliyping at every speE above 1-. percent of the mini-
mu:m speud with ruidcr free '"i'th extreme aryrmetry of pover
possible by the loss of one engine."


Criterion for Vertical-Tail Effectiveness

.inder I. mrme trick Power Conditions

Each of the specificatio -s previously listed requires
the direction control or the directionaRl stability of
the airp-lne in onustion to be sufficiently powerful to
bal-rce Tuhe yawini- moments c.:-~ted b a'-ymetric nower
under certain specified flight conditions. It follows
that the vertical-tail effectiveness in flight rra be
7~-'.ed by the maximnu.m amount of as-mLnetric power which such
a t.il c-an balance under the -' c ifed conditions. In this
investigation, therefore, the- axlimum asymmetric i over
per:iissible under the a rsp. d and trim conditions speci-
fiod by the Army and the wACA was used to evaluate the
effectiveness of the vertical tails tested.

It should be observed that the flight specifications
require that straight flight or c-1. lete equilibrium of
lateral forces and moments be maintained. Tn order to
maintain such oauilibriu.: inr flint, the ailerons must be
deflectAd so tLat the rl--,n1 mrn : ts caused by asymmetric
pow-r ar' bal-i nced and the airplane_ assumes an attitude
of bank, which nullifies the 9iae C'orce creat--d by rudder
deflecLon anl/or angle of sideslio. In)ismuc' as an atti-
tude of bank dost not affect the crim requirements of the
vertical tail surface, no attinmpt .:'as made in the ctsts to
sitnletlt the balance of side force by a. l1,-e of bank.
Aileron deflection, however, drecly affects diectional
trim by ".IItu of the ; "::-.~ m ments creatred by such de-
flections. Consequeintly, the aileros w...re so adju-sted


.i.,Ua ARR -o. L5A13










YACA ARR No. L5A13


for all tests as to maintain complete balance of aero-
dynamic rollinC mor.eats anid thereby to simulate flicrht
cond' tons correctly.


TESTS

Test Condrtions


"he test lift c-,ef'fcient w:a establ.phed fri-o ccn-
siderat!ion cf the specified airsreeds in Che Army and NACA
req i.ren mnts. These value? were converted to lift-
coefficient forms as follows:

The :ACA require::.et (TI-) I a (rudder fixcd) speci-
fies an airspeed equal tD 1.19 tines the take-off sp eed.
Tf VkiIe-off is a'ssvled equal to 1.2Vmin, the airsieed
requirement for this peci ficat ior is equal to 1.32Vi. .
If tie maximum lift coefficielnt cf the E-2 airplane is
assumed equal to 2.0, the specified 1ift coefficient cor-
res;:?idin to 1.2V V 1 defined b:, the excrmssion
V nn
2.0 whic- e uuais l.15. In a similar manner,

the lIft coefficient, r.eces ary to satisfy IACA requirement
(IT-;) 4 (r dder frec) was founu to be 1.2. 7- lift
coef.icient necessaryy to 'at isf tihe Ar-iry requirement
(rudder fT::ei) ':as calculated as 1 .3. Because it was as-
sunrid that slt cliQthances in lift coefficient would not
afct the -odel test re su.ts if the correct values of
thr>, t coefficient were used, all tests were run at a con-
rtant anr 1 of attack of 5, which corre orded to a lift
coefficient of 1.10.

All tests -ere r un at a tlest velocity of ;3 feet per
sec c3 whir.h c.,rrc sp ids to a t.-t Teynold U number of
128,'U(C ba' J.c 3tn the :cEan ae-):,nan: c-ord of (.503 foot.
The a16r'.?n :cfl((Ctiqnr for all tests v-erc adjusL,~i to
provide q qil1'brLu i r' ling r-menc'.


Test Pr c'.- .eres

:Ruddr ixe 7.- 'i the tests nith iudider fixed, the
r.odo .ss r ounces on the "csnd w? th che rudaer dflected
in the director: that counteracted the yaw caused by









NACA ARR No. L5A13


asyTrnnetric power, T;easurements were then taken of the maxi-
mum amount of ar:.,:_ .tric thrust the rudder would balance at
anles of ;'* of 0O and 100 for rudder deflections of 0,
503 1J, 20Y, and 30.

Rudder free.- The tests with rider free a::re made by
mea'.I r.j the &ount of asymmetric t-.rust and anrle of yaw
produced by asymlmetric po,:"er for var-.cus angles of yaw up
to the an'le at which directional instability was encountered.
Tests with rudder free were made of the model with each of
the following vertical-tall arrangements:

(1) Vertical tal. alone

(2) Vertical tail o1nlu dorsal fin a

(3) Vertical tail plus dorsal fin b

(4) Vertical tail plus ventral fin a

(5) Vertical tail plus ventral fin a
plus dorsal fin a

The absolute dorsal- and ventral-fin a-reas required for
each test were determined from the percent .es of the
vertical tdils beinE tested rver: in figure C. No tests
were made to deterrrine the influence of auxilliary fin area
upon the characteristics of twin tail 4.

7 :er calculat-.ons.- T"re thruit c: icfficients that were
obta i-rc" i. i- ,- the S:l ;r cnvErted to the
simulated asymmetric brake hor. epo:'er of the full-scale
airplane '-; mean- of' the rel.tion hip

bhn = t-p

TeV
eh -(

or

T D2
bh = (1)
1:. 2









'L...A AARR No. LEA13


TLe full-srale propeller efficiency rn was assumed
to '7e equal to P.75 for the calclations. Values of wing
l t /1.i, an, rd eller diameter D v:ere obtained
fry; the full-scale characteristic of the North American
p-2l sirplrne and were equal t 7 47.5 pound per square
foot cnd 14.7 feet, respectively'. 7"- value of the mass
densi-: o)f sr p was chosen as 0.0028, whichh is its
value at sea level rli'er standard a~ rsniric conditions.
S'fosti tutor o.f these values in equation (1) yields the
relat-i onship
Te
cbho -31 (2)
C,-/2

The value,3 of CL rt equation (2) are these co~irespond-
ir.g to tne irspeed specified in the Army and the rACA
require.ents and ,wer:'e deterx ined as cho 'n in the section
entitled "'Test Condltions3. 3Su-sttit.-tin these values of
lift coefficient in eoua ior (2) yields the expressions
defining the conver'".n of nmdcl thrust coefficient Tc
to the estimatcd f'ul-sc-le braie horse:o': er, h'rich are:
For rdder fixec,

,ACA reau recent

bh'p = 30FCT (3)

Army requirement

bh- = 67CTc (4)

For rudder fre',

F.i-.YA reqrirepment

bnp = 6C2.CT (5)





The cata ottaTied in the investigation are plotted
in fi- .; 7 to 1C. Figure 7 shows the rollinr-moment
coeificir te s produced by il aid]eros used in the tests.
Filz.urs 3 t' I pre -ert the viaues of the asyrrnetric-
thrut cocfficlent balanced by neans of rudder deflection.










NACA ARR No. L5A13


Figures 11 to 13 Five the values of the asynrr.etric-thrust
coefficient balanced by the yawed rn-odel with rudIer free.
Data sbowiiv- the irfluence of doisal- and ventral-fin areas
upon trim characteristics are presented in figures 14 to 19.

-he test data in figures 8 to 13 were rearranged and
converted to values of full-scale brake horsepower in
figures 19 to 24. An index to all fi ures _s presented
as table I.


Effect of 'h1de of PrDpeller station

71'- mode of propeller rotaticn in which the up -r
blade tips move toward the fuselage is henceforth designated
inboard rotation. ~, rotation in which the v ~.-'r blade
tips move out toward the wing tip is designated outboard
rotation. Almost all conventional airplanes are equipped
with right-hand propellers. On irultiengine airplanes,
the direction of propeller rotation 2'ith respect to the
wine tips (inboard or outboard) is therefore determined
by the location of the propeller. If the right e6.: Ifne
fails, the direction of the o::-rating, propeller rotation
is inboard and the airplane .".s in a positive sense.
For left-enrine failures, the ooerati.r, propeller rotates
outboard and the airplane yaw is negative. The results
of the present investigation show that use of different
modes of propeller rotation caused considerable difference
i.n trim characteristics of an airplane operatir-- under
as-.'r. trick power.

With only one exception, the data presented in
figures 8 to 13 indicate that the use of outboard propeller
rotation ..--creased the values of erlissible asyInretric-
thrust coefficient balanced byy ay given vertical-tail con-
fi u.i action and that thl s mode of rotation would therefore
determine the minimum vertical-tail size. The exception
occurred when twin tail 4 operated under the Army specifi-
cations (fig. 9); in these tests inboard rotation was less
favorable than outboard rotation.

The difference in asymmetric power balanced by a given
tail arrangement with either of the two modes of rotation
appeared to increase in r.-:w'tude with the amount of di-
rectional stability and of control being plied. The
largest differences occurred at large rudder angles and for
tails 5, 6, and 7, which have -,;.h aspect ratios. Particu-
larl'rlarge effects of propeller rotation were observed when
the rudder was free.










".'-A ARR :'. LEA13


"he tmarr'it-ude of effect of reversing the croeeller
rotation '-as bee illestratcd in figure 19. This fi e
preseits tnc calrulated values of erif.issible brake horse-
p'ower for for ot -odes of propeller rotation for the rerre-
se:tative rudder deflection of 200 (fi-gs. 1(a) and 19(b))
and fr that a.;l- le of ides)ip at which directional Tn-
stability was encountered in the tests with rudder free
(fi.. 1 (c)). This anfle of siJeslin was between 10 and
12 for a!os t al21 the conditions tented "'he result
ire=snted in fis-ur 13 shOow that the difference in asyn-
rEtric po;'r balanced by the vertical tail for inboard
and boardad rotation vwar atoutt 'CL horse ier for most
conditions and was as lar-e as 1C'O horsepower for some.

.-. effects of changing tn: direction of propeller
rotation appear to be expl-aied by th'e data of reference
4. Reference 4 condcies th t use of inboard propeller
rotat ion with che fl-?ps d'"r caseda the lipstream to con-
ver-e toward the tal. and there' -- increased thc contri-
bttir. of tle tail surfaces to directional stability for
smTall to moderately largest a.-les of yav. :'s sl ipstream
dlso-laceTmnt w-ould result in a beneficial effect of in-
bcar r-otation upon t-.e 'triiin actior of t'e vertical
tail surfaces, rprticularly for twin tail 4, w:-nch unaer
FACA speo-ifcations (3 = 0e) ai ears to be artly im-
r:ersed in the slirpstreamr jet. Reference 4 also concludes
that outb-,ard otat in causCe the slipptreanr jet to di-
ver --. C ianequently, this nodle of rotation incrFases
the t-il effecti- veness at Ire arFle-s of ?aw b'ut is less
Fat*sfactory in this respect than& the rinoaord mode of
rotation f:r other anles of yaw. This repo:,.- .r explains
the fav-rable effect of outboardi 0 rr~e llet rotat- on upon
twin t;ai 4 v;when c nerot.nr at an ar. le of sidesl.o of 1'0.
At t1 .is anrle, ov:rn to its original lateral dr-lacer.nt,
t.Lis tail lies withinn the slipstrea;.

The d.:ta obtrlnrad in the tests indicate that for
twin- rrin al sir3. e~res eui2.ed : th t in1le vertical tr'ls
and c rv olionr. i r igt-Prnd rrp rlltrs, the failure of a
left t. _ir. ':'ill im;?-e the r-rrc revrtrc flight conditions.
For ar lancd eS ipeJ withl1 ti..n vern cal tails, however,
the iirr of a right enr-re si uld prove more critical
St the flfl n't of the .:-,- r-aurc:.nts. earlyy ,
it -y be reariss that ume of ivocell-rs rotati'.: in-
board n oth 't!i"1'is. ("ymmetric rotatsor) w'o:lId be advpn-
to eur f or a r- .aor. ecIui ed F ith 3:1 : "l fins both to
I-- r-ve ta'l effcctlvtres arnd to :ra:e the handlin- of
contr-o'l s i: lar rc': -less of le location of the









NACA ARR No. L5A13


inoperative engine. Conversely, s-- .-~tric outboard rotation
should be favorable for airplanes equipped with twin fins.


Effect of Vertical-,-:.l Design

Effect of vertical-tail area.- The effect of varying
vertical-t~a' s- t.. :t.i:'- _ror a study of the test
data for geometrically similar tails 1, a., a-. '. -e
data for these tails with rudder fixed were converted to
values of full-scale brake horsepow.er and clotted in
figure 20.

.!e data of figure iC(a) s: ow that increasing the
vertical-tail area resulted in increases in the asymmetric
power balanced by a giver. rudder deflection at zerc anle
of sideslip. These increases, however, are not directly
proportional to the increase in tail (rudder) area, as
might normally be expected; this lack of proportionality
indicates the presence of secondary slipstream effects
upon the vertical tail surfaces. Such secondary effects
are prorbaly produced by the side::,ash angles 7e rated
at the tail by inflow into -'-.e slipstrear jet as well as
by the more direct effects of slipstrear velocity.
furtherr investigation, however, is required to establish
a complete explanation of these secondary slipstream
effects.

ie- data in figure r -(b) illustrate the favorable
effect upon the asymmetric power characteristics of in-
creas~!ni the vertical-tail area at an angle of sideslip
of 10. These data show that, when the airplane is side-
slipping, t-e directional stability of the vertical tail
surfaces reinforces the action of the rudder control in
nullifying the effects of asymmetric power, and higher
values of asymmetric thrust can therefore be balanced
by a .-ven vertical-tail arr.:---~emer.t. ~ F :Tr --nitode
of the effects of directional stability can be obtained
from a study of the curve for a rudder deflection of
0 (fig. 20(b)), which is directl-- indicative of the
rudder-fixed directional stabllity. r'.ise data show
that the directional stability contributed b" tail 1 barely
balanced the unstable yawing nomsnts created by the yawed
fuselage-wing co.-olnation. "-1.:o the tail area larger
than that of tail 1 increased the directional stability,
as would be ':.--cted.









16 i'.A ARR Ho. L5A13


The effectc of .-ncreasin tail area noted in the
test-s vith ruidcr fixed were also observed in the tects
vit. rudder free. Fliure 11 illustrates the influence of
tail area upon the rucder-free trim characteristics of
thze model operating under 'sysrmnetric power. In this
fiJ-ure, the data inJicate that freeing the rudder of
tail 1 was d estabiliing, as would normal~ be Pxpected
cince the rudder tpce mp!oloyed had a negative floating
rsto. Because of the slender margin of stebility
associeted vit tail l, the destabilizing action of
freeing the rudder was sufficient to cause directional
inst ability. Making the til 1 a'rea r neater than that of
tail 1 increased the directional stability contributed by
the tail surfaces sufficiently to overcome the destabiliz-
irn effects of the fu-clae and, connruently, permitted
increases in the asy;r, trick thrust balanced by the vertical
tcAil urfaces.

Comparison of twin tail and single tail.- Twin tail 4
r::;' bc directly compared ;-ith tail 2 inasmuch as both
tails wer? of the samt!e epct ratio and equal area. Fe-
cause the twin. tll I was located ai:nmot di rectly in the
s] ioctre:t, the tw n tall as more effective than the
sinrl tal at zero and small anrles of sideslip. Figure 21
shoss that the influence or power at ~p 0 -made
tail 4 almost as effective as tail 3, a surface of equal
Suspect o utr, a 't possessin t 0 peErcent greater area.. At
angles of sideslip -rcater than 0, however, tail 4 was
less effective tlan tail 2 with the rudder fixed at an
anTle of sideslip of 100 -ad .hwi the rudder free (fig. 22).
These .ata conf"rr, trends noted in the past and indicate
that t'he direction-al stability contributed by a twin
verticpl ta-' is less than tab contributed by a single
tail of the same aspect ratio ana equal aree. The in-
creased directional stab1Tity achieved by us"e of the
single tail Is partly ascribed t' the. favorable end-plate
effect Cf the horizontal surfaces u'on the load charac-
teriLdlcs of the verftcal Purfaces. In addition, the
sl ngle tail tha but one r':t junctur" compTared with two
fcr thr t.win tail and therefore i.r l- s affected by inter-
f.re cc e fe-cts.

It should be noted that the curves for tail 4 for
rvdder free (f'g. 2(I)) do not pass through the origin
but f&ll above aria beo!w it e;rm.iiic, on the I.de of
propeller r-tation em lcyed. Thec-e curves indicate that
revcrsinr the propeller rotation altered the sidewash
carsed by the pr opelltr sAfficie tl t, r reverse the local
anric- of attack of tall 4 at. small anFles of sideslip.









NACA ARR No. L5A13


The results of the tests indicate that choice between
single and twin vertical tails would caepend largely upon
the pilot's handling of the controls following a sudden
engine failure. If the rudder control can be applied be-
fore the airplane reaches a moderately large angle of
sideslip, the twin-tail design should be more suitable;
otherwise, the single vertical-tail design would be
preferable.

Effect of increasing aspect ratio.- The effect of
increas-in a ts> et rea ei-' e" a t-1:' from a comparison
of the data obtained with tail 6, a surface of twice the
aspect ratio of tail 2, with corresponding data for tails
2 and 3. These data are shown in figure 23 and indicate
that doubling the aspect ratio of tail 2 has approximately
the same effect as increasing the area by 50 percent at
the same aspect ratio (ta'l 3). This effect is in close
agreement with the wind-tunnel force data of reference 5,
which show that doubling the aspect ratio of a surface
from 1.5 to 3.0 increased the lift-curve slope from 2.2
to 3.1. 7'or a given rudder configuration, such a change
in lift-curve slope would result in an increase in total
tail load, or trirnming effectiveness, equivalent to that
obtainable by approximately a 50-percent increase in area.

Comparison of conventional tail and all-movable tail
w ith 1 ..* :.- t : .- 7 .- *. "..eL-. r i-- J ', .. t ,L : t: -.e
efficient action of the all-movable bail reported in refer-
ence 6 arose largely from the "all-mo_,vable" feature or from
the fact that the tail was of hi'h aspect ratio and had
the inherent advantages associated' wiTh tails of that type.
For the present investigation, therefore, tests of the all-
movable tail 5 were supplemented with tests of tail 7,
which is identical with tail 5 except that tail 7 is of
conventional that is, fixed-fin design.

A comparison of the effects of tails 5 and 7 upon
the characteristics of the airplane operating with asym-
metric power is shown in figure 24. These data indicate
that the all-movable tail is markedly more effective than
the conventional tail at zero sideslip with the rudder
fixed and with the rudder free. At 10 sideslip and with
rudder fixed, however, the all-movable tail was only
slightly more effective than the conventional tail
(fig. 24(a)).

These test results may be explained by use of the
curves showing typical tail loads (fig. 25). These curves










NACA ARR No. L5A13


hoi, the vii-Ie.cor of tail loa. o. vith vertical-tail inci-
denrce and rudder deflection for E conventional and an
al-1n:ovable tail. The tab area of the all-rmoable tail
is aIssumed equal to the rudder irea of the conventional
tail. Tne variation of the load with deflection of the
all-.:'vabele tail is in6icaled by the dashed line in
figure 25. This variation Is 'ue to the 1l.n: 'e between
the tc and the movaile f rv.-ard surface, ".- slope of
the lcd curve is determined frh- the linkage ratio
wr/it wrnch, for the case invest. ated, was equal to 1,12.
Tf the effect of rovvwr is inorr.c, the angl e of attack
(tail incidence) of the c-nverntJi>nal tail Et = 0 is
als. zero. The rudder reflection therefore rodurce?
cInFre in load a lonr a path cin cide tal with the zero
ordinate. For ex 'aoic, a rudder defect on f iC0 pnrcc'-es
the tail i ad co:,res.rndin> ti : _e load indicated bj
point a. For the all-nmovable teil, however, a rudder
deflection of 10 c.aue s a -imu-lanouse change in tail
an'le of attack and etb deflecionr arnd r.drece the load
inj-icated br point b. Consefuently, at :ero sideslip,
the all-mr.vable tsil is capable of noroduc'r, much .la'-: r
pa'i',ing moments v-ith th i lch to bal ce the effect of a.s.m-
r eet rc power than tn e conrvntional taf.l1

At rnderate anrles of seidelip (1 0 to 15), the con-
ventional toil operates in the hirh-l!ft rerio: of the
lift curve of the ta I and cone gently produces tail
)oads of an order cor.-erable with those p'"duced by the
all-mrcvablI tail. The conventional tail nay conceivably
price tall loads even eater than t.ose of the all-
r.ovable tail because the conventional tail 's unrestricted
in the use of rudder. Th-- all-' va;ole tail, however, is
l.imirfe for a givenn linkarc- ratio to the rn~der deflection
that irol.oc the tail inc.ie'nce at maximurr lift. Further
deflc tion ,woulI cause tne entire surface to stall.

Ir bo.la.c.i. L Ie effects F' syjniatric power, the
supr: -irity of the al.l-r:vrable tail to the conventional
tail was .:ost I.vrked in the r:dder-free tets. This su-
periority car c"e sc-ibed tb the fact that the hinge-
moment chaiacteristics of the all-mrvable tall force the
entire tall t float agIainst the vin:d when free (positive
11 a4 .i.-' rat C) "n: cnaeoa'iently increase the directional
stab'lity of the s!irlane. In c nsi:ering the advant'-.es
of the el.l-.'..vahle vertical' ta.l ve the conventional
tail, it should be observed that sayingg" oscillations
may be ind:c-.C by contr -s:urfacc. fi-.ction with imrpror'rly
des'-icd tilP havingg positive fleati .,- ratios. (See
re fe rence ,.)









':ACA ARR No. L5A13


Effect of rudder chord.- Tie effect of decreasing
rudder ci:rd .- ':- .. -: .e te-t data for tail?- 6 and 7
(figs. 10 and 17). These data show uhat, although the
rudder of tail 7 had only one-half the area and one-half
the chord of the rudder of tail 6, the rudder of tail 7
balanced approximately two-thirds as much asymmetric power
at zero sideslip and approximately seven-eighths as much
power at 100 sideslip as the ru.-er of ta`l 6. 'I'h-se data
are in agreement with conventional trends because it is
known that decreasing the rudder cord increases the yaw-
ing moment per unit rudder area.

With rudder free, tail 7 balanced a greater amount
of asymmetric power than tail 6, which in-dicated a favorable
effect of reduced rudder area upon the rudder-free direction-
al stability. This action occurred because the rudders of
tails 6 and 7 are of the t-: that trail with the wind and
so reduce the directional stability when set free. Con-
sequently, tail 7, because of its smaller rudder area,
created smaller destabilizing moments when the rudder was
set free and so balanced a greater amount of asy:-ietric
power.

Effect of rudder deflection.- The data obtained in
the tesrc s :i..L th_ ii ; '.*I -> i.I the rudder deflection
increased the amount of asymmetric nower balanced by the
vertical tails at a decree i .- rate.

Effect of dorsal and ventral fin,.- The data illus-
trati.,. tihe efi t ',i .'lir- doi;:1- .nd ventral-fin areas
to tails 2, 5, 6, and 7 are presented in figures 14 to
18. "o data are presented for tail 1 because the addition
of dorsal and ventral fins did not noticeably lepsen the
directional instability associated with this tail arrange-
ment.

The test data indicated that the addition of auxiliary
fin area increased the directional stability at large
angles of -:~v and thereby increased the maximum amount of
asymmetric thrust balanced by tne tail surfaces when the
rudders were free. Increases in rmaxi-unm asymmetric thrust
of the order of 30 to 1Ci.- percent were observed in the
tests.

The addition of ventral-fin area was generally found
to be more effective tlan the addition cf an equal amount
of dorsal-fin area. The use of a co:rbination of dorsal-
and ventral-fin areas (dorsal a and ventral a) was










0 A ."A ARR .1J. L5A13


'enerlly r'ore ffec+ive then a sin,:le dorsal fin of the
far'- ot. l areaa (d rrsal b).

AJle.on dfiections rcqured to trhim asyrmnetric
t'rrru 't.- E rero.eptt-ive pc : cital ailer6n deflec-
ti? re-ired to tr.'r the rllairSg ,rent created by
as 'tr' c thlrut is [-p7resnted in f i oure These
deflections were always obtained by' equal uo-and-down
mJovcmets of the ailerons. CaiCultced values P.ae also
rr c [nted irn fApure 26. 'hes calculations were made
by tin _:> the method '-reFented inr referrence 7. The calcu-
lat e lift incredmenLt crented i; thl o-peruting propeller
were ultipll.ed br the la era1 ar'i of the proereller to
ob'carir r'oll]inr. r morncnts, which Jc er1 converted to ailron
daflecti-ons r. ,. r.cd to tri by use of7 the data in figure 7.

The results presentTed in fi:ur2e 26 show that, although
the scatter wa- cons'd ..r ble, te ts-t date agreed fairly
wec1] with the calculated values and ir.dicated that moder-
ately larpe a.ler deflections woula be required to main-
taiit straight t fl t nd- a .- -. trickc poweC rcarCitions.





The fo l:, 1ine c rcl usjon, v'ere drawn from trIm' tests
of a twin-enrine-airplane model ocoratinp under asymme~tric
power (sinple-enrgin-.) ccnditTons sLpcif-ie&d by the NACA and
Arm~i Air F'orcrs:

1. The direction .of rot.tlion of th operating pro-
peller biL an imtpotant eiffct i on the apy:nmmtric power
that could ce ba'l rced b', a r. vn vertical-tail design.
Si.n:-e ei-tical ta&lW were mo.:t effective when the oper-
atir', or'pelicr waL rtintint inbo'"rdr. in tails, however,
were on:Ft Eff'ctlv v :hen the ,eraPting propelr waR
r3t atinr :utb :rd.

2. -., c'..l-:ovrble -vertical ta: of aspect ratio 3
vith a inke l tat war ;7.'e effe-ct.vj thar the conventional
tall of the t asectt ret-o and eqal porea "n balancing
asyn.etrc per, artiloarlr 'l t rcuder-s were free.
The all-.::vab: ttaI I was :.nr :il.7 su ;T eCr to the con-
ventin-inal vert'cal tail -f nor:1l aspect ratio (1.5).

3. hs rin vertal-tall desi-l pr~ierallv balanced
a -re tt.r amoL;nt of syvr!imtri~c power tvhan t".in vertical










NACA ARR No. L5A13


tails of the same aspect ratio and equal area, particularly
when the rudder was free. At small angles of sideslip,
however, it was possible to balance more power by rudder
deflection of the twin tails than by rudder deflection
of a single tail.

4. Increasing the aspect ratio of a vertical tail
resulted in increasing its trirmin- effectiveness under
asymmetric power conditions by an amount proportional to
the accompanying increase in lift-curve slope.

5. The trirn:inp effectiveness of the vertical tail
surface increase almost linearly with the vertical-tail
area. Increasing audder deflection and rudder chord in-
creased the triirJT:v r effectiveness of the vertical tail
under asymmetric c
6. .Then the "udder was free, addition of dorsal-
and ventral-fin areas increased the capacity of the
vertical tail surfaces to balance asyrmetric-power effects
at moderate angles of sideslip.


Langley ,Jem rial Aeronautical Laboratory
iTtional Advisory Committee for Aeronautics
Langley Field, Va.









NrACA ARR No. L5A13


1. 'ilruth, P. R. : Reru-irements for Sat-isfactory Flying
alties of Airplanes A ACR, April 1941.
(Cla-rifiutlion changed bo Festricted Oct. 1943.)

2. Anon.: Stabllty and Control iRquirEr Ets for Air-
1panes. AA' Specification Co. C-381 Ag. 21, 1943.

3. Shjrtal, Jos= ph A., in Ct t .out, Clavton JT.:
Prel rirar S ta Jilit' and C: niblu Tets in the
YACA Friee-lih ,inOd 'unrel a.-. Correlation with
Full-Sac&l Fll,'t Tests,. T"A I N. ~10, 1941.

4. Pitkin, arv'n: "rce-?71f't-unnel. Tnvestigation of
the ffect of ode iof Pr-a ler Rcta.tion, upcn the
lateral-Staibl ty Ch-rac teri stics of a Twin-Eng.ne
Airolane .odel .ith li.n;:le Vertical ais of Dif-
ferent Size. N.AA Al"R No. 13, 94

5. Zi:.ecrman, C. T.: Character~ tics of Clark Y Airfoils
of Sinall Aiect Latios. N.AC Re N 41, 1932.

6. Jones, Rbert T., Kecker, n 1 Keck cr, arolKCd .o : Theory and
frelirinary Fl-ght Tet.-s of an All- unablee Vertical
Tail Surface. NACA AP, Jan. 1945.

7. Pasr, ". R.: ',inrd-Tir.nel Stuide of the effecto of
Proeller Operatin anr Fla- Deflection on the
Fitchinr Mnments and Elevator rinpge c;i nt- of a
Si. le-Enin ne Parsuit-T irpl.ne. "!A"A ARR,
July 1942.










NACA ARR No. L5A13


TABLE I.- INDEX TO FIGURES


Figure Description Remarks

1 Ph t,-.rbh.b :f t t r:.:; 1 _! r. el :n trlr *-ar, r. :-.' fr (- '-: *' .
f il r. t t arie l

S cretc- :f L -:.e ,:. r T d I- trlr sT 6r c r':r. ; r-l r.
freedom in yaw and roll, in Langley free-flight tunnel

T .re-. les drawl-i :f I- ,,.: twrn-er Fre f .idel "estea 1 tarn.leS i
free-fl1gbt tunnel Itnr a-yir-etric :-rer

4 Fh:13-.rach f '.w'. -er- f 'r.e mr del jies In tr:- te?~ 6 1-, Lari-ley fr-e- Y:.el wi tn a'. 1
f llr.t tunnel

5 Plan-form and dimensional characteristics of seven vertical talls
tested on a 7-seale model of a twin-engine airplane in the
Langley free-flight tunnel

6 Various fin arrangements tested with vertical tails on a 1 -scale
model of a twin-engine airplane in the Langley free-flight
tunnel

Test spel Test Tail Operatlng-propeller
Pigur ficatlons condition arrangement Curve Remarks
Tail Dorsal ena roaton1
----------- --------- 2 ------ ------- Prpeller aff CL against 6s All'r:.n -ai8t.rt!ir

a NACA Rudder 1 to _- __ ------ Inboard and outboard Te against 6r C3rectaloal-ontrol
(p = 0) fixed 3 r un
8
b NACA Rudder 1 to ------ -----------do--------- Te against ,r Do.
(p = 100) fixed 3

a NACA Rudder 4 ------ ---------------do--------- Tc against 6r Do.

b Army Rudder 4 ------------- --------do--------- To against 6r Do.
(p = 100) fixed

a NACA Rudder 5 to ------ ------- --------do--------- To against o, Do.
(p = 00) fixed 7

b Army Rudder 5 to -------- ---- --do-------- T against 5r Do.
(p = 100) fixed 7

a NACA Rudder 1 to ------ ------- Outboard Te against p Directional-
(Rudder free free 3 stability run

b NACA Rudder 1 to ------------- Inboard Te against p Do.
(Rudder free) free 3

Na ACA Rudder 4 ------------- Outboard To against p Do.
(Rudder re free
12
'l 1 I-- -----_---- --_--_----------- _-----_-------
b NACA Rudder 4 ------ ------- Inboard Tc against p Do.
(Rudder fre4 free

a NACA Rudder 5 to ------ ------- Outboard Te against p Do.
(Rudder fred free 7

b NACA Rudder 5 to ------ ------- Inboard Te against p Do.
(Rudder free free 7

a NACA Rudder 2 All Outboard Te against p Effect of dorsal-
(Rudder fred free combination&2 and ventral-fin
area
14
b NACA Rudder 2 ------do------ Inboard Te against p Do.
(Rudder free) free

a NACA Rudder 3 -----do------ Outboard Tc against p Do.
(Rudder free) free

b NACA Rudder S ------do------ Inboard To against 0 Do.
(Rudder free) free

1Right propeller operative.
20Cabinatin tested apr tall alone, doral a, dorsal and ventral a, ventral a. toreal b.


NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS











NACA ARR No. L5A13


TABLE I. INDEX TO FIGURES Concluded


Test speci- Test Tail Operating-propeller
Figure ficatione condition arrangement rotation1 Curve Remarks
Taill DorsallVentra

a NACA Rudder 5 Tallalo Outboard To against p Effect of dorsal-
(Rudder free free dorsal a, and ventral-fin
dorsal a and area
S_ ventral a area
b NACA Rudder 5 All Inboard Te against p Do.
(Rudder free) free combination2

a NACA Rudder 6 -----do------- Outboard To against p Do.
(Rudder free) free
17
b NACA Rudder 6 -----do------- Inboard To against p Do.
(Rudder free) free

a NACA Rudder '7 -----do------ Outboard Te against p Do.
(Rudder free) free
18
18 -- --------- ------- ---_ __ ------------___ ---------------------------
b NACA Rudder 7 -----do------ Inboard Te against p Do.
(Rudder free) free

a NACA Rudder 1 to ------ ------- Inboard and outboard bhp for Effect of mode of
(p = o0) fixed 7 8r = 200 rotation
19
b Army Rudder 1 to ------ ---------------do--------- bhp for Do.
(p = 100) fixed 7 Or = 200

c NACA Rudder 1 to ------ ------ --------do--------- bhp for Asymmetric power
(Rudder free) free 7 10 of directional
divergence

a NACA Rudder 1 to ------ ------- Outboard bhp against Curves of various
(p = 00) fixed 3 tall area rudder deflection
20
20 -- --------- ------- ---_ ---- --- ---------- ------------------
b Army Rudder 1 to ------ ------- -------do--------- -----do----- Do.
(p = 100) fixed 3

a NACA Rudder 2 to ------ ------- Inboard bbp against 4 Comparison single
(p = 00) fixed 4 and twin tail
21
21 -- --------- ------- ---__ __ --- -------------------------------
b NACA Rudder 2 to --- ---------- Outboard bhp against ) Do.
(p = 00) fixed 4

a Army Rudder 2, 4 ------ ------ Inboard andoutboard bhp against o Do.
(p = 100) fixed
22 --
b NACA Rudder 2, 4 ------ ----- --------do--------- bhp against p Do.
(Rudder free) free

a NACA Rudder 2, 3, --- ------- Inboard bhp against Effect of aspect
(p = 00) fixed 6 ratio
2!
b NACA Rudder 2, 3, ------ -------------do--------- bhp against p Do.
(Rudder free) free 6

a NACA (pz0) Rudder 5, 7 ------ ------ Outboard bhp against Comparison of all-
Army (p=-10) fixed movable and con-
ventional tail

b NACA Rudder 5, 7 ----- -------------do--------- bhp against p Do.
(Rudder free) free
Tall load Illustrative of
25 ----------- -------- ---- ------ ------ -------- ----------- against it principle of all-
movable tall

2 ---------- --------- ---- ------------- Inboard and outboard Te against ,8 Aileron deflections
required to trim


lRight propeller operative.


2Combinations tested are tail


alone, dorsal a, dorsal and ventral a, ventral a, dorsal b.

NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS







NACA ARR No. L5A13


Figure 1.,- Test model mounted on trim stand in Langley
free-flight tunnel.


Fig. 1












NACA ARR No. L5A13

















w
-I
-1
w
0.



z






















































cr
w o
0







a. a C
0























































OOc
rz
4 a
.I-



(n Xa
o t mz
z -J 4 i
0 I / Il
0 0.4 *


0



z




U 02


Go 0


Fig. 2












z


0
0
UJ
w
LU-


U)

I









z
b-J
LU











-I


LU
0






z









z
z


















z
I-






















ZL
0
-J

































0




u-
LU





















0
z z
41:





2I
S>-
z



I-


0

0


I-
z




LU

0




t-





111






NACA ARR No. L5A13


Tail 2
r- 16-- /3" \
7 I


,Frtiaqpptn slotted
Flaps deflected 45


SPropeller diam, 850"


NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


Figure 3.- Three-view drawing of 1/20 -sca/e twin-
engine model as tted /n Lange y free -
f//l/hf unne/ lw/ asym"r/e/r/c power.


Fig. 3









NACA ARR No. L5A13


~-iC


NACA LMu 27625


NACA LNKU 27627






Figure 4.- Twin-engine model of B-28 airplane used in trim
tests in Langley free-flight tunnel.


Fig. 4


,
7


, 7~3%~'~: ~Ji~a~~







NACA ARR No. L5A13


Tail 5 (a-movable) Tail 6


; about 0.27 MAC.
/6.43" behind C.g.
NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


Tail 7


Figure 5. -Pan-form and dimensional characteristics of seven
vertical tails tested on a 1/20 scale model of a
twin-engine airplane /n the Langley F/ree -1//~gt
tunnel.
o


Fig. 5







NACA ARR No. L5A13


Fig. 6
















V)
CQ










~cz
1






I-
!-a




k
Li:







NACA ARR No. L5A13


> ^

0 *




ceT


~z






--------------3-'0
-
0 ~z ;
\ -



\ EE
\ _O

_\_ _
----~\--
_______^___
-----^--
---\-

""zzzzzz^"\
I I I I I I I I \


. / / O


0 0
IuPJUOL/-6U1//06(


c


)


V)





I Z
Ni


Fig. 7







NACA ARR No. L5A13


0 ----erafing prope/Der '/ to 4/n c'boord
+- -perating prope/Alr rotatr/n/ i'rd


0 I/Q o 30 0 /0 0T 390 /0 80 30
Right racer def ct/on i oLg
(b) Army 5pea/caf/ons M 0 =/O
FiQure 8.- Asymmefic-r/c-poer X ) C/aCrrer ics of a fwn-
eng/ne crloane model equiu/ppel w/fh erf/ca/ -ta//
designs I, Z, arn 3. Cd- uc( 5;/n f/?/ ro///nr mom/n?2
equal Oj c, = 45j, 2-0 or = =SJ /eff propeller w/n't-
mrli/ln rudder f/xed. NATIONAL ADVISORY
COMMtIIEE FOR AERONAUTICS


---


Fig. 8a,b







Fig. 9a,b


NACA ARR No. L5A13


o Operlt/ing propeller rotating
-- -- ODerating p-op/ller rotaf/ng


7Tal 4 (one of hwo)


Oultbord
inboard


./6


.08



0
O








J6
,-q-
o
(24




qD
0
(j


!


Irofafon


/VACA specif/cat/ons ((3



Outboard
rotation-


7T atato-


rofat/o~--


0


/0 20


dO 40


R/ghl rudder cdflection, ,d, dey
(b) Army specif/ca1/ons (G8=/00).
Figure 9- Asyj. --e'r r -P cover ch rctefst'/cs of a twin-eng/ ie-
airplane mode/ eul/pped With vertical- tail des/in 4
cS such that the rol/rng fmomrents equal o ,6& 45; 0e= O1
o= -5 left propeller windmr//ing, rudder fixecl.
NATI-, EE A AF:n ni ,
COMMIT IEE FIJFI A,,.',, iLS







NACA ARR No. L5A13


0 Oi e .ig propeller rotal/r outboard
+-- Operafng propei/er rotating inboard
Hinge //ne H/nge I/ ,
of /a0 o b //





7a/ 5 Taol6 Tail


axi mumr 7
.32 L-- jI- ''L /7e Iboara
-- rotation

y" \ 1 __ /) ou--9 D
L/ --" S -- ^ ----at/o-/



So roation

.32 -I -ytdabl/o- --- ^ -o()
d .24 rlaton

Srotaion
ur I it ard d
.3 16 I o-./oopl

Q 8 1 uInboard r1otion- rotaon-
_- .__rrl ton K' t



J 6 --


/lull /etren ti rudder defleclon, 5 r ceg9
(b) Army speclf/cal/ons (B5=/O".
Figure/o.- A3sy/rnrtrc-power charac/tr .../cs of a fw/n-e&//ne-
oirp/aue model c9/e ipU wItf vertica/l-/fal de3/gn 5, 6,
and 7. 6da u-c/h) fal7 rolling mo/efnts equo/Q0; 6?(5 4 =0;
c<>- 50; ,/e Prope/ler wi/d',)l1ng; n 0d1pr f/,e9.


Fig. 10a,b






NACA ARR No. L5A13


- Modea/ d/rec/orno//ly un-/Ol2


(a) Operathr porooe//er roa2tf/n oL-toard.


d/rect/onoa/
unstable Of
Tco =O


I I I I I I I I TIN AL ADVIBOR4


TOM ITTE FOt AEIONA ITCI



a -


o

o /0o 0 30 /o ?O 30 o /o 0o 30
IAng/e of /os//p,/3, doeg
(b) OperalQl; plrocp/er /c atA /n1xoard.
Figure //. -As3ymfr/tr/c -power c/waroc/r/st/cs of a /wL n-enQ/ne-
ocrp/ane /72del/ equilped w/ih verf/c/- /a// cdeqsgns /, 2, arY
3. 6da such /?ha the ro//lll rrwns m e equal/ 0; S, = 45; O
cc--5/ left ropel/ler w )lndm//n)g; rudder free.


.6 I


ns


Fig. lla,b






NACA ARR No. L5A13

-- AMde/ dlrec/lonally unsta oe
SVertical ta/il lone


.24

.16

.08


(a) orat/ ng prope//er
rot-3/n9 outboard.
32----


.24


Fig. 12a,b


NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


A 0 I_
-/o O /ni O 30
/Angie of side/p,, c, eg
(b) Coerngt/ propeller /-roa/ng /nwrd.
/grre /2. /Asy/mmretr/c-coer ch/racter/st/cs of a f-V/n-engine-
airolane fde/ eQuIpped with ver/tcal-tail desi n Q .
do s5c/ frl t-ae rolling moments equo/al/;45% S -0;o o=
/eft propeller windmil/ing j rudder free.


i~t~I~


-L-







NACA ARR No. L5A13


-- /todel cd/rctonO/ly un~S


Ang/e of ,ds//, (3 ,O 6g
(b) Qorao/rf prope//er rofif/ng inboar d.
F/iure /3 .-Asymmetr-c -ower choaracter/sts oF a -Iwn-en/--
o rpaonex mfc/ L(ep1 Y w//h Yert/rl/-ft/ 6~1sIns 6,arti 7
da, such WA //l/ ro//// moc/7xe2s equo/ O; 6O~ 455,-= cci 5
/eft propelWr win77m/l/lng, rader~ free.


Fig. 13a,b







NACA ARE No. L5A13.


----fAIcef/ a/rect/ior/Jy/ unstabk



7a\llzsal

A--- -
Q^^ v-^~Z D


Ve0nra

0-


(a) op/ratin p'ge//er /z~rzwt aofAz /d.







/0 O0 30 40 : 60
ARng4 of /des6/p, o osg
(2) Operaf/nrq car~ e/, /'er af /nw ,boa/r.


F/7gre /4.-E//I f cya'r/-alod ventflt-f/n oares umcon
t/e asymnr7tnc-co~w4r c/ rac/ens~tc of a /w/n-engne-
aorplane mox e eQau/pped w/fh vert/ica-to// 'esI/gn 2.
d~,suc/th tthe /fro/Ing manZen? equol 0; 6S=45;"6ce=O
o< = 5"; /lef propeller wrindmir/lll ; rudder free.
NATIONAL ADVISORY
COMMITTEE FOR AERONAUTIQG


Fig. 14a,b







NACA ARR No. L5A13


8--- a
---A- a-
y==:-~= L


(a) Operncng pope/ler roat/ng ouLboC/ t.


0 /0 S~0 .30 40 o,. 60 NATIONAL ADVISORY
Afq/e of 5s1de&S11,/ g aS CO MITTEE FOR AERONAUTICS
(b) Ooera3mng pr/xp/er wh//y/n a
r/gwe /5 Effect of daodz/- ard vert7al-f/n areas upon t
oasymmetnrc-,cpo nr c/orac/ert/Aics of a. fw/n-/ -osarp/au e
A/fel eCqu/-pc wi )V7 er/icoa-/xal desi/9n 3 c such/ t#Y/ lthe
rol/irg r rren/t equa/ 0; = 45; 6e = 0 5 cc= 5;" /et propeller
wirdminf)/li rudier f/ee.


a.
a-


Fig. 15a, b







NACA APR No. L5A13


S--- Modelt drectionr/Jl unsLot2


- _DoMrl
8- -


Vef-
GL


S j0 ,0 40 J'D NATIONAL ADVISORY
A/le 0 f SS/0 40 MMITTEE FOR AERONAUTICS
(b) Opang prope/ler roo//an /InbarcZ.
'rQure /6. -Effect of dorsal- acv' ven//rl-n rea5 up r? /he
asymmeftrc power 6charadecrC/scs of a w/n-enq/ne-
o/rp/lane mode/ equipped w/ll w,'rcal- fa// des/in J.
da sucn /11o/ /he ro/ll/n momnen/s equal O; :6= 45; 6- 0
o = 5 leff prope//er Wlndmnl//ngq; rudder free.


Fig. 16a,b







NACA ARR No.


STol <


V-----


0C~fo
bx


~RnI,

0a
06


Cs'ffra/ a

i \ "__ __


(a) Operati/ng prcYl/,r Iot Ig/rk aboard.


/o0 3D 40 50


0 Of S, -,/-.. /&, CA NATIONAL ADVISORY
(Ab) ~O"pei r /er ro/1an1 g 1n219 FOR AtiuNAul'cs
Fig9ue in.-ffeL of abryao/-QfrI ventra/-/Zn areas upon ter/
cf j:rerf c--//C-rV C1fr cYact/er/shtcs of a ltin., ,ic -.vrplane
nd/el -%..l-../ V/ith vecii-/-ful/ c design 6. 6ca such that
te roflirr moments equol O; 6, = 45;, 1 e = 0; = 5; /eft propeter
vvirlnn7)llng. rludtr free.


o<

.40


L5A13


Fig. 17a,b


--------- /1kwr~ c?~~`',~j~7,7 j"y LL.~r~L,71L~k








NACA ARR No. L5A13


o___ rsal
0-- ce

- )
V---- D


/ I ."L YU OU C) NATIONAL AVI''SORY
A/e of 6/c51 7 s/, FO r0 AERONAUIICS
DOeranq propel/er rrolaf/ ,xr .
y/gure/ I-E/k c/ o/ctySa-Iy/-/nd .'_. .J-.o :-- 7 L/pon fhe / e .,'".;,.c-
power Ckzrac/ers///c o/ a y/n-erl rne.-Q/rp. ,.I'?e /7 ads QU/pp
W/r/t ver/ca ta/ OLig/n -2 6 .such ft/ fl/ rokl/// mwo)en/f equcl0O;
6, --d- de-0} --sS /e//prcpC.//c- wt/r)nl//hgr;raljCe/r free.


Zbr5a/ 6


CVka/
(-
a.
al
O-


Ventral a


'25*40
. 24








./6
DB











./6


Fig. 18a, b








NACA ARR No. L5A13


l 0


Inboard rofa4/o


E


qLAJ e

/6 ( ) ,o-

0coh
'-I 7


(a) MCA WpecifloW'10s (Orr 2 .






800 .- -.- -.-.-.-- .-


(b)Army seaficat/ons (, = o) .
SVl--I-


Aboard ratzAoq
5//mated by
x/fpoL/ot/on of
'act.


NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


. n


600r
SDirecton -

0 / 3 4 5-T
(c) VA CA spec/ficalfoCans, r er frse (/Oe d/A.
Figure /9. -Effec of moe of e c/e/er /otaf//Con tH fe pern msst/e
asymmelrpc broJe Morsepower, catutalfd from test cJdt for
the North American B-28 airpane operzatingq c one engine
under NACA and Army flight specificat/ons.


I, s-


Fig. 19a,b.c


L",







NACA ARR No. L5A13


H/nge
One




6Tai /C

IOX ---



/20-C --



800
4X

o
' 900----





S(a) AA LA
SNATI
COMMITII





An/ _


0o 0 .0f .06 ,o8 .0 ./2 ./14 .16 18
Vertical-toal arei,, 5 frlcfton /wng 0/ea.
(b) Arm r speccficah/ons 65(=/0 ).
F/gZre 20. -Eff6ct cf verf/mco/-t/ iMria ore2U r0 c rde oefleori
upon f/; E, l7ni5/WYe br e ho/rseower, ca/cu/ato fron
model stet cl f- for the Norf7 Afmer/can 8 -28 airplane
oparahrg on one e vine u'raer NAc/ ond Army fl/h
Specicf/C//Oa. O/,1erot/g p,/re//er ro*iif/ng oc /IxArd.


Ta/ 3


Fig. 20a,b






NACA ARR No. L5A13


----0----
- +-
- --x _


4 (tw/n- af/to
A/1


---r-ilTT----


I II i-


~jFF//


R-











4a
0






1Oa


4 0


%
f/6cx


4
Riqht


8 /2 16 20
rudder clef/ecdl/o, 4r-,


24
dey


28


Igurm21.-Coanparlon of /he asymnmer/c-px uer cQ r1cfr/5-
//cs of an/rp/one eQu/ppea/td 't/ ruI/n on /~;/e
verf'ca/ a/^./sVC,3Y4 c/f/ca6cv75; = o0*.


"Z/ (a) nboardc rotate^ .


-A- -- 1UM, ITTE FO AE ONAITICS
-7----------------------------- ---




------





-___ (b)Outiboardrbdad/ov
I__ _ _


Fig. 21a,b


2






NACA ARR No. L5A13


RIigh rudder def/ecf/on, c, decq
(a) Army specificaNions (1 =/0).


/200


1000


I ^c7


Ang/e of s/des5ip, /S, deg
(b) AVCA specCficaions ; rudder free.


Figure 22.- Compoarson of the asymmeftrc -power
characfer/5s/cs of an a/rpl/ne equipped with
tw/n and S1/nf7e ver/ical fa/1s and at various
angles of Idesa/p.


Fig. 22a,b







NACA ARR No. L5A13



o 240-To/l Aspeci raIo/-
---- Z /.54 "_,
26W0 1 /.0 -5
x---- 6 3.00 1/

S/60 3






400 NA 1Ni LAt MVIS lY
0
CO MIT EE OH |ERO Al

4 8 /2 /6 20 24 28
/R/qgh/f rudder def/ea/on, o6 o@9
K (ACA 5,pC//-ca1/aS e= 0.





/200- --- 2
m recfKona
uns fob/6



K- X.__
-


Fig. 23a,b


0 2 4 6 8 /0 /2 /4 /6
Ang/e of s/dsL5/p, 1,6 deq
(b) /VA A spec/f/co/on53 rudder free.
Figure 23.- Corn/, r/son of Mhe asymmretric-power
characier/51 of anl airplane equ/paxd wv/fh
hi/h- and lowv-aspec/-ral/o er/coal fails. boardd
rola/on.







NACA ARR No. L5A13


zsa
280







340

ocZ







d, &




0o
^2M




12a

8- 00

400




200
$ ^CO

O


I I I I I I


S6 /O /16 /4 /fo /0


Anrle of sdeslip ,, dg

f7/ire 24.- Copoar/sonv of Ahe asy/n2rneMfc -power c/arac-
terf/cs of a twi/n-eng/ne Cirpo/lre /nomxe/ eqwgpped
w/ih an all-movable vertical fa// wi/t //n/ ana with a s/ng/e connenf/ono/ oa// Oper/ ng
props//er f//?ninqg boarct.


O ---- Connfonalu/ 7)
- 0//5-r -+-- AI/-mtouab/e (To//I)




S---7/ 7



7N -c7 0AL -ll VIS Y
3_ ,t.-ll 7__ _...

(~) Ir-*,der / xec/o


S8 /Z Ir ZO 24 Z8 IO JS
/?/// r/jtider cdnecT/on7,dde o'g


/ DiO/recfnlly
uns/b/






O+

t h) Pear free.
A ,


k


Fig. 24a,b


PC


f







NACA ARE No. L5A13


---Lood carve bor oJI -norable tob I (,/-i z)
Lozd curse for convention ku/ = 200
I I I / /-- 5'


O 5 /o 05 ec
Vrhaco tail incidene, ce
Ang/e of si/deJ/p J deq
Ang/e of aiH ack of/
Figure 25.- Typical /oad curves for /he oil- mowichl
ond conventonal types of vertical /l.
NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


Fi g. 25







NACA ARR No. L5A13


24








O
leo







4-


0


.3, .40
coefficient, Tc


.08 .16 .24
Asymrnmetric thrust


Fgure Z6-Adileron deflections required o trim
ro/ihng moment created by asymmetric
powrn f3 =0o, operating propeller
rdohtng outboard.


1- +-4- ----- -----+ 4-I- -+


o /

G---0 l--


NATIONAL ADVISORY
-0- COMMITTEE FOR AERONAUTICS


--


Fig. 26




Ii
Ii




UNIVERSITY OF FLORIDA

3 1262 08106 463 5





UNW'ERS!TY OF FLORIDA
G'.. ; TSD ,Ei:'PT NT
120 P' -' TON C.D. ,-:. _., ,Y
P.O. .X 117011
S*: ''.' L E, FL G2.11-7011 USA




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