Analysis of vertical-tail loads in rolling pull-out maneuvers

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Material Information

Title:
Analysis of vertical-tail loads in rolling pull-out maneuvers
Series Title:
NACA WR
Alternate Title:
NACA wartime reports
Physical Description:
5 p., 1 leaves : ill. ; 28 cm.
Language:
English
Creator:
Gilruth, Robert R ( Robert Rowe ), 1913-
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:
Ailerons   ( lcsh )
Aerodynamics -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Summary: An analysis is presented of the vertical-tail loads to be expected as a result of abrupt aileron action in accelerated flight, as in rolls from turns or pull-outs, for example. The formulas derived show that the vertical-tail loads obtained in rolling pull-out maneuvers are directly proportional to the load factor, wing loading, and aileron effectiveness and are inversely proportional to directional stability. Sample calculations for an assumed fighter airplane are presented and discussed. It appears that critical tail loads may occur in rolling pull-out maneuvers, particularly on airplanes with good ailerons and low directional stability.
Statement of Responsibility:
by Robert R. Gilruth.
General Note:
"Originally issued August 1944 as Advance Confidential Bulletin L4H14."
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 - 003806701
oclc - 124095906
System ID:
AA00009401:00001


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Full Text


N.: ...


CB No. L4H14


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS


WARTIME REPORT
ORIGINALLY ISSUED
August 1944 as
Confidential Bulletin L4H14


ANALYSIS OF VERTICAL-TAIL LOADS IN


ROLLING PULL-OUT MANEUVERS
By Robert R. Gilruth


Langley Memorial Aeronautical Laboratory
Lengley Field, Va.

UNIVERSITY OF FLORiDA
DOCUMENTS DEPARTMENT
120 MARSTON SCIENCE UBRARY
P.O. BOX 117011
GAINESVILLE, FL 32611-7011 USA


WASHINGTON


RA: WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of
',StliBe research results to an authorized group requiring them for the war effort. They were pre-
ijai4 held under a security status but are now unclassified. Some of these reports were not tech-
i idtei d. All have been reproduced without change in order to expedite general distribution.


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NACA CB ITo. L4H14

I/iATIOIAL ADVISORY CO!'.ITiTEE PFR :.EOLLUTI'Cs


C: FIF TTiTITL EBLTLTTIJ


ANALYSIS CF V2P,.TIC.-.L-TAIL TLO. I'7

ROLLING PULL-OLT iAIUiVEiiS

B.' Pobert R. Cilruth


TT1 .13.-Y


An analys's is presented cf t-he .ertic :.1-tcs l
loads to be ex,:ect-t2 d as j result ,'of .bru. t j'l,.rcn
action in acceler3ator fli;,ht, as in rolls from tLrn.3
or pull-outs, fcr ex.'n.rle.

The formulas deri- vd 3'1o7 tii.at *th.- vertical-tatl
loads obtained ir. r-llin,- ul'-cut ziraneuv rs .Lre directly
proportional to the lad factor, witnj loading, .nJ
aileron cffectlvenes:- and :-.re ir.ve'rscl icporti nal
to directional -cst.'Jiity. Smn-.le c i.c-:i .ions frr an
assumed fighter airnl:n? are prez ;tn:led jan. di.i:'.ssd.

It appears that critical to;l l-..ds may occur' 1:
rolling pull-out maneuvers, particularly y .,n ai:rl ans
with good aileror-ns and low directiot-il stA, bl'.tvy.


I TT C'LL U" TIOIl


In fightor and dive-homre r 9ir1la.tes, albru:-t
aileron action is frequently iusd in acc3lerat-' flihlt,
as in rolls from turns or pull-outs, for e:-:sr.ple.

Because of the large :;awir,.g mo,.!nts -n.c'd.rced by
ailerons in accelerated fli-h;t r.nd boc'C s -rf the
increase in ailercn rower achieved sirce the war, the
vertical-tail loads obtainable in. rollir.: rull-rut
maneuvers have bpon examined anmislyticall'y a.nd the
factors on which the loails dep.-rn h.Ave benr determined.

3'.awn7 f BOLS

N yawing moment, foot-rounds


yawing-noment coefficient










2 CONFIDENTIAL NACA CB No. L4H1t4

CL
p rolling velocity, radians 3er second

b wing .pan, feet

V true airspeed, feet per second

pb/2V helix angle generated b: wing tip, radian

p sidesi1.p angle, Pegreoes

dCn/d airplane ?-lcctioral stabili ty per de,'ree

q da-ns-r:i rreasrre, rounds peir square foot

S vertical-t-'il area, square feet

dCN/'d. slore or t ll or.-.:al-force-cc'ffccient curve per
degree

n lo.d factor, 5

S ::.r'.J: rca, suc.re feet

W a' rrlyne grom. wiA-l.-t, rounds

it tail length, foet

Lv load on vertical tail, pcunds


DEVELOPIEPT OF PFO.C Lt.S FOR CI TE INIr; VEITIC L-TA IL

L(',IOS IN ; -OLLTINH FULL-OUTS


For elliptical spcn loa~ir.g, the yawing moment due
to alleron derifle:tion and rolling velocity ray be
expressed with sufficient accuracy in teris of the wing
lift coeff:'.cient a.nd t-e helix angle in the roll as

CT'_ ( )
cn 2V

The silceslin -ngle p developed in the roll with
rudder fixed is obtained, to a first approximation, b7
dividing .he aw'ing-morment coefficient of equation (1)
by th--. directional-stability coefficient of the airplane;
thus,
C ONF TDEIT IAL
A










NACA CB No. LLHl4 CnFFTDTYTIAL 3


Cn
dC n/d

L pb
'-r (23)
3 27 c:Cn/dil

The vertical-tail loads r.esult.r:g frcrm s3idsl.ip
angles are the product of the ild-.3ip an7,le, c1-
vertical-tail area, the dynamic pressure, and the
slope of the tail norral-force-coefficient cu-rvs; that
is,

L 5V-1 --- (3)
u.0


Since qCL is equivalent to the product of wing
loading and the load faco;r, equation (5)may : be rewritten
as
ni *J b 1
S 2' (v4.
2 .-, V. ,/4

From equation (4) the vsrtical-.a:il lead nr a rcll m.y
be seen to increase :n direct prcpo..;lon to the load
factor, the wing lord!:ng, ,nd cYe aileron effectiveness.
The loads are also proportional to the vertical-ta'il -red
and normal-force-coefficient slope :.nd are inversely
proportional to dirctiona stability. Icreang .he
tail size and aspect ratio should, in general, rdu"ic
the loads because the directional scatility incre'sys3
faster than the product of area and ncr:t.al-forco-
coefficient slope; that is, an increase in tail cffec-
tiveness should reduce the loads by restrictir-.,g th'
sidsslip angles and thereby reducing the unstable rror cnts
contributed by the fuselage and propeller. The loads
represented by equation (4) v:oald be chiefll. ls.ads on
the fin due to angle of attack of the vertical tail.

If the rudder were sufficiently light per degree of
deflection and rolls could be perfectly coordinated, the
tail load would be
N


n V' ob Sb
= 8 S 2V VIt


C ONP TDIT IAL










CNIACA CE Bo. LH14


This loc.d wo-ld be pri'arilv a rudder load and, in general,
woAld be considerably smaller than that of equation (4)
althou-gh the 'valua of pb/27V might be sonme-"hat increased
by the rolling moment Jue to vcwing. It should be noted
in addLtion, hciw vcr, Ichat with a light rudder the rrd.or
could ce applied a2ter substLntial sideslip had .evelo:ud
so that rudder loads would be added to tl.e loads cf equa-
tion (4).


C-.LCUL.';.TAO OF TAIL LOAD ,T 0 A

TYPICAL l 7. T{'. A !RI I .


In order tc illu.sctrte t-he oe-,dr of mainntude of
loads to be e:-r:ectd in rcllinr- cuill-out maneuvers,
sample calculations are presented for a t'rpicdl case.
The css-ui.cd dirmensions and characteristics of the air-
plane are as fellows:

S, square fee ............... ............... ..... 2 0
W/S, pouinis r er squar-e -' c t ....... ............... .
b, qeet ................... .......................... 3.
Sy, square f et .. ....... 2
daj/6 per egre ..................... ............ 0.0 5
ndC,/6 "er degree ............................. -0.0005
It, feet ......................... ...... 17

The var-itic-ni with ir,n'ic te r?- --.0c of ,b/2V o'tc'- n-
able 'r'ith a 50-poiinr stick fc'-ce for tl'o a .s-;s.':d airP:ln:1.no
Is ,i.o'. in ? 'ore 1(a). The c. ';, :.ted an-les "f cid?-
slip rprodJced -r3 a rcsuilt -!f rol'lin.g wiith a 50-pound
stick force c-iotbined with ncr.:.!l accelerstlons cf 53
and 6o are shown as a function of ir.t'icated alrspe.. c in
flit3lro l(b). 'he calculated loads on the vertical tail
that result from tne sideline r')evelored are shown in
figure 1(c). The l,?:ad c-. th- tail witrn bg nrm-ial
acccleratcon aicd a 50-pound stic:: force, ..t with
rudder uzed to maintain zero s'desl'4, is also Chown in
figure l(c).




As :.nmy be seen from figure 1 or front frcmulas (1)
to (5) from vnich figure 1 was constructed, large
C 0'FIDENTIAL


CONFTD';lFT IAL










NACA CB No. I.h'lla


vertical-tail loads may be orodceed b; the aEleronr control.
Although the loads are much lower ';hen tan rudder is i. .3rd
to maintain zero sileslip, rudder forces are, n 7-;nr.:l,
far too heavy to re ,-it use of thle r.U.de--" exce It .it
relativol.r low speeds. .1Aso to be ',crsi'le:red 12 L.-2 ca'3
in which the rudder Is applied after- cideslip ss.s v".e-
loped so that the rudder action would tend to Ircr3a .
rather than to decrease the lobids.

In the exar:ple shown in fi,.T re 1, the c.lr.-ti-lc
stability was assumed to be constant over ':he ':ng) of
sideslip angle. In most actual casss, riowover, the
yawing-mor.ient-coef'ficlent sloie is j.;mll thlrout-h- a
moderate range of s'Vdeslip anCle -.d genrll' be .-es
great at larger angles. A sma.-ll. slope th..ou.-i n-utr-al
will cause the :l axt ; !" tail lo.-:.d t'-o b pi'o ac- at
speeds higher the. n those Lhc.n ir f -2r; -. In an
actual case ca.il.latlcns ;ot.ld. lve tc be :.ac' frc the
yawing-momert curve obta ..e f.rOi lind-tu.:n:: tsts !..b3
on a model cn .:hlch a propcllsr lvi.n~, the prop-r suie-
force factor was instlled.

Present nmetho-s of c. lcul.:ti r.7 th-- 'i'fe.li:p r-n.- e
and therefore the lod,"- resultInr. f_'o.:: sil.ciron action
are open to qutJsticn. The ac.':.-xi'".,.te m tr..t :ed presented
herein is believed to Five sc-ire.ht crasinller sideline
angles than those actu.lly cbtaircd in fli-:'ht an.- tLhe
sample loads rcesent-d are th.'efore probably too s:r.-ll.


%.'ICLTiDI' .n ; R;2: 3


wTe analiys's oresnted indicates that lar.e nf.
perhaps critical loads on the vertical tail v.il'. vcz-.'.
in rolling pull-outs. These loads are directly nro-
nortional to t'-s load factor, einig lo-Ading, and frlleron
effectiveness and are inversely proportic-nal to the
directional stability of the. sir'.lain. .' r ex ac
methods of calculating these loA.ds ar? bein; developed.

Langley !Ymorial Aeronauti'a-.l Libccr'atory
National Advisory Con.,ittee for Aorone'itics
Langley Fielj, Va.


C O FID.T IAL


C ONP EF Di.TTI1JL



















U
U


* U
W>
01
0h'
.4-
OS


'!>
w

h a
0z
0.0
IcC
Ua


Fig. 1


(a) Assumed values of pb/2V obtainable with 50-pound stick force.


o
I


(b) Angles of sideslip obtained in ro.is at 3g and 6g.


S-6g (aileron only)I
^a I- _- -- -
r4

A.4 2000





rudder) | _
0-

100 200 300 400 500 600

Indicated alrepeed, mph

(a) Vertical-tali loads at 3g and 6g in rolls using alleron only
and at 6g using both aileron and rudder.

Figure 1.- Sample calculations of vertical-tail loads in rolling
pull-out maneuvers.


NACA CB No. L4H14








UNIVERSfIT OF ORIDA



UNIVERSITY OF FLORIDA
DOCUMENTSS DEPARTMENT
1 20 MARSTON SCIENCE LBRARY ,
PrO. BOX 117011
r,,ll ESVILLE, FL 32611-7011 USA





















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