Skoog, Richard B

English

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NATIONAL ADVISORY COMMITTEE FOR AERONAliTICii
WAI!!’’’IMII Iullwll’r
ORIGINALLYISSUED
July 1945 as
Advance Restricted Report 5E22
A COMPARISON OF TWO FLIGHT-TEST PROCEDURES FOR THE
DETERMINATION OF AILERON CONTROL CAPABILITIES
OF AN AIRPLANE
By Richard B. Skoog.
Ames Aeronautical Laboratory
Moffett Field, California
:+.,4
.:
‘““’:’NAC:X.;“’””
WASHINGTON
NACA WART,IME REPORTS are reprints of papers originally iss~ed to provide rapid distribution of
advance research results to sn 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.
A-37’
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“ I?ATIOI?ALAJ)VISORF COMMITTEE FOR AERONAUTICS
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.ADvAMcm Ei-STRICTEiD
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A COMPARISON OF TWO 17LIGHtiTEST
R~PORT - ‘- ,
PROC13@ES FOR Ti3E
. . DETERMINATIQI? 01’AILERON CONTROL .CAl?J@IL1T13ilS
. . .
Ol?M?.AIRPLAXE , “ “
..
By”R$Chard B. Skoog
.“, .
SUMMARY
.. ..
.. .
A comparison, based on actual flight tests of 8everal
airplanes, has been made between. two.flight-test procedures
for the determination of tbe aileron control capabilities of
an’airplane. The ?roceduraa conelet of perform~ng ru&der-
fixed aileron rolls from ~traight unbanked flight and from
steady turning fllght;
For the airplaneE considered in this report,no signifi-
cant difference was fGund to exist in the index of aileron
power pb/2V a~ determined from data taken w,ith either of
the testing methode. This agreement was confirmed a~ being
correct in a comparison of eideelip angle occurring at the
time of maximum rate of” roll. Extension of the close aqree-
ment shown in the report to cover all other pre~ent-day air-
planes is believed to be reasonable.
.. IHTRODUCTIOIJ
. ..
..
At the ~reeent time an indication of the am:ount of ai-
leron contr~l available in an airplane iG determined in
flight from measurements taken in rudder-fixed aileron rolls
. .initiated from straight unbanked flight, Tho resultg of
these tebts are usually presented In a curve. of .maxlmum pb/2V
as a function of total aileron deflection; where p 16 the
maximum. .rolllng velocity .in radians per second, b is the
wing epan in feet, and V iq the true ai~s~eed in feet per
second. The method,. as conceivad originally, admftted tha
possibility of adverse raw due to roll affecting the uieaeured
)1
. .
.
.“.!
2 MAOA ARR ~Om 6E22
. . . .,. . --- . : .-.
value of rolllng velocity.. The qusetion now has arisen as
to whether. rolling ~rom straight flight yields results con-
sistent wath the original concept of the test, since enough
additional aldoelip may develop due to gravity in rolls from
~tralght flight 80 that a lower determination of pb/av
would be obtained than actually ehould be attributed to the
ailerone.
An alternate testing procedure which is believed to
eliminate most of the effect of gravity has been propo”sed.
This method.~s substantially the same am the present one,
exoept that the aileron rallu are to be made from ~teady
turns, with. the airplane banked about 45°. It Bhould”be
fiotod that In this method the”airplane must be rolled out of
the turn.
.
The purpoee of this investigation was to compare the re-
sults obtained from the two methods through an analysis based
on actual flight teete of several airplanes. The com?arlmon
ia baaed on data obtained during the course of flying-quali-
ties inveatlgfltlonn oo.nducted at the Ames Aeronautical
Laboratory, Moffett Field, Oalif. The airplanea which are
considered in the analpala are lieted below:
Martin B-26B-21
Yorth American P-51B-1-NA
Northrop P-61A
Lockheed PV-1
KETHOD Or 00MPARISOE
. .
Comparison ia made between cur+rea of pb/2V and aide-
slip angle as a function of aileron deflection, aa detemined .
from comparable data obtained by each of the testing proced- “ “
ures. Similar aond~tiona of indicated airspeed, engine .
power, flap position, and landlng-gear poeitioi were consid-
ered In the aelectlon of comparable data. Teata at widely
separated alrmpeeds under the engine powers listed below and
with flap and gear up were ohoeen aa being repreaentatlve.
Airplane Power
B-26B-21 Power for level fllght at each speed
P-51B-1-NA Power for ~evel flight at lowor epeed
Mormal rated power at @igher speed
P-61A Normal rated power at all apeede
Pv- 1 Normal rated power at all epeede
—.
MACA ARE NO. 5E22 3
The curves of pb/2v and eideelip angle were obtained
from a consideration of changes In the variablefi involved
from the uteady state befbre ‘the roll to t%e state exigting
at the time of maximum.rolling velocity.
. .
“.-.
. .
. .
. . . RIGSULTS AND DISCUSSION “ “
. . .-
. .
. . “..1 “ . . ..
The pre~entatlo”ri and discussion of.the “cumrves of this.
“report wI1l be ma”de in. three parts: namel’yj’a r“ate of roll
comparison, a @ldesllp-angle comp-arisen, and.a general dis-
cussion. . . -.
. . .
Rate “of Roll Comparison ,. “
..
Curves of maximum pb/2V plotted agalnet aileron angle
are presented in figure 1 for the B-26B airplane, In figure
2 for the P-51B aflrplane, in figure 3 fmor the P-61A airplane,
and in figure 4 for the PV-1 alrplanei Data ”were available
from tests at only two airspeeds for the P-51B airplane,
while it was poeelble to consflder tests at three airspeeds
for the other airplanes. The figuree kmve been dlvlded into
eeveral parte according to airspeed eo that a comparison can
be made more eaeily.
.-
Examination of the curves for the several airplanes
shows reasonably good agreement to exist between the two eets
of data at each of the airspeede teeted. Some scatter in the
data may be seen, am well as apparent trends indicating the
possibility of some disagreement. An analysts of the probable
lrzor in the pb/2V determinations revealed that these dis-
crepancies may be attribtited to experimental error.
,-
The h~gh-spebd cur~ea for the B-26B airplane are not
~trictly comparable because of the great ~pked difference:
Ileverthelesoo if all the curveo for thio airplane arb super-
posed, it will be eeen that eesentlally the same curve was
obtained at all airspeede.
Sideellp-Angle Oomparlaon
Curves are preeented for the B-26B, P-61A, and PV-1
airplanes showing eidesllp anglea exieting at the time of
maximum rolllng veloclty for the tests ~uet discussed In the
rate-of-roll aomparleon. Similar curves are not presented
for the P-51B airplane due to insufficient sldeslip data..
.. . .. . ..
4 RACA ARE HO. 5~22
.
The curves of sideslip angle agalnet al~eron deflection
are praeented in figure -6‘for Mw B+.26B airpLane, in figure
6 for. “the P-61A akaplane, ;sn&.%st&i4Ure ‘7.’f.~.~~a .pV-l.a.ir-
pla’ne..’ “.H .’ : ..--”)=:.”. “:’.:..” .“’: ‘..~”
,..- .r.., .,.. . ..
..’”. .. :.J.. . . .
R’or the tests at 150 miles per hour on the B-26 airplane,
good agreement may be seen from figure 5. More sideelip 1s
ehown to oocur in rolls from turns than from stratght flight
at 224 miles per hour, however, which Is oppooite to that
which might be expected. Ho correlation between this diO-
a~eement and. the correspondl.ng pb/2V -data (fig. l(b)) can
be. seen. The remaining two sideslip curves are for tests at
widely. eeparated alreneeda and therefore are not direotly cQn-
parable. It may be seen, however, that in right roll more .
sldeslip apparently occurred In rolls from turns at 295 mlle~
per hour than in rolls from straight flight at 266 miles per
hour .
., ..- .. .. . .
Good agreement was obtained for the P-61A airplane at .
all airepeede considered. This airplane exhibited very small
amounts of sld.esllp due to roll even at low speeds. This WaE
undoubtedly due to the aileron-spoiler type of lateral~ control
syst em.
Tests on the PV-1 airplane also show guod agreemen~, as
may be seen from figure 7.
. . General Dlscusnion”.. “ . -
. . r..
When the rate-of-roll and sideellp-angle curves are con-
.si@ered .as a whole, i,t appeavs that n~ significant diffe~eneee
exist in the results .obt.ained by the “two teitlng procedures:”
The value of., pb/2V determined with.either method .for practi-
cal purposes may be said to be the same for the airplanes con-
sidered in this repor.%. This result appea~a to bd well con-
flrmad..in the sideslip-angle oompari80n vhzch. shows, in genaral,
~Q difference in the angle of sidesllp at the time of maxi.mu.m
rolllng velocity when determined by.,the two methode.
. . !
A possible explanation of this.agr.cement might ;;ry well
be tha’t the rapidity with whioh maximum rolling velocity OC.
curs, and the moderat,e anglq of bank at which it occurs when
rolling from straight flight, allow for only a negligible
sideelip apgle to develop due to gravity. . . . ~ ..
,.
Coke5deratlon should also be give’rito the fact that an
airplane necessarily flies. at A hlghar angle .of attack :In
..
NACA ARE EO. 6E22 5
turning flight than in straight flight for the same airspeed.
This fact would in&icate that since the aflverOe yawing moment
%a orflinarlly a function of angl% of attaok, more aflverae yaw
should be expaeted in rolls from turning flight than from
rolls from atralght flight when no aiitealip flue to gravity
were present in rolls from straight flight.
It 5s belleveil that the agreement between the two meth-
ofla shown in this oomparlcoa may be extendefl to include all
present-day conventional types of alrplanea.
00?!TOLUSIONS
1. Por the airplauea conaldered in this report no eig-
nlflcant differences exiatsd in the eurvea of pb/2V plotteil
aa a function of aileron ileflection aa fletermined from data
obtained In rolling from atralght flight anfl rolling out of
a 460 hank in steady turntng flight.
2. The elfleslip angle occurring at the time of maximum
rate of roll waa eaaentially the same for rolls mafle from
atralght flight aa for rolls made from a 46° bank In eteady
turning flight.
3. It la believed that the agreement between the reaulta
obtalnefl with theGe two methofla as shown In thlc comparism
may be extended to include all preeent-day conventional types
of airplanea.
Ames Aeronautical Laboratory,
Eational Aflvlaory Committee for Aeronautic,
Moffett I?lelfl,CalIf.
.()
NACA W NO. 5E22 Fig. la
.- —
o From straight flight, 149 mph
O From turning flight, 150 mph
.08
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G
NATI()NAL
FOR
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B
2
20 10 0 10 20 30
Left Total aileron deflection, deg Right
(a) Rolls at low airspeed
Fi~re 1 (a to c).- Comparison between flight determinationsof maximum
pb/2V in rudder-fixedaileron roll~ from straight,
unbanked flight and from steady~ turning flight. Clean pondition, power
for level flight. Martin B-26B-21 airplane.
.,-
.04
.04
, 0 I’romstraight flight, 224 mph
0 From turning flight, 224 mph
I?ATICNAL AtVISC)RICob(nlTTEE 0-’
FOR dERoNAtTICS 9
m
6
,0”
0.
30 20 10 0 10 20 30
Left Total aileron deflection, deg Right
(b) Rolls at moderate airepeed
~igure l.- (Continued).Martin B-26B-21 airplane.”
NACA ARR No. 5E22 Fig. lC
.
0 From straight flight, 256 mph
0 From turning flight, 295 mph
.08
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NATICW& AIvISORY COMMITTEE
FOR AERONAUTICS ()
.04
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o
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30 20 10 0 10 20 30
Left Total aileron deflection, deg Right
(c) Rolls at high airspeed
Figure l.- (Concluded).&rtin B-26B-21 airplane
0 horn
U From
Fig. 2a
straight flight, 175 mph
turning flight, 174 mph
.08
5
z
NATICNAL ALvISORI COMMITTEE
FOR 1ERONAITICS
.04
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> 0
PI
8
0
.
~
.. // p
> &o
l 04 “
; o
~ .08.-
30 20 10 0 10 20 30
Left Total aileron deflection, deg Right
(a) Rolls at low airspeed, power for level flight
Figure 2a,b.- Comparieon between flight determinations of maximunpb/2V
in rudder-fixed aileron rolls from straight, unbanked
flight and from steady, turning flight, Clean condition. North American
P-51B-l-NA airplane.
NACA AM No l !3322
.04
.04
0 From straight fligilt,240 mph
O From turning flight, 241 mph
20
—
Tom 12’TEE
lTJ(js
—.—-,.
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—— .— */
——
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10 0
/7
w
.
17 -
— .—
—
— .—
—
#@-- ---
———-
—.
—
——- --—
——
—-
10 20 30
Left Total aileron deflection, deg Right
(b) Rolls at moderate airspeed, normal rated power
Figure 2.- (Concluded).North Aaerican P-51B-1-NA airplane.
.
NACA ARR No. 5E22 Fig. 3a
-..
,,
0 Froui
O From
straight flight, 183 nph
turning flight, 188 nph
~ .08
a
$
FOR RONA1TICS
,04
&
3
;0 .“ —
.fl
J
.04
g o
4 ,08
30 20 10 0 10 20 30
up Left aileron deflection, deg Down
(a) Rolls at low airspeed
Figure 3 (a to c).- Comparison between flight dete~inations of maximum
pb/2V in rudder-fixed aileron rolls fro= straight,
unbanked flight and from steady, turning flight. Clean condition, :Iormd
rated power. Northrop P-61A airplane.
,, ,,,, . ..! l.—. -. . . . . . . . . . . . .—. .
NACA AM No. !53i22 rig. 311
0 From straight flight, 222 mph
0 From turning flight, 225 mph
~.08 ~
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lx
NATICML AIVISORY COMMITTIIE
l?on@RONAt TICS
,04
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B
c)
.
J H
l 04
9
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‘.08
30 20 10 0 10 a 30
up Left aileron deflection, deg Down
(b) Rolls at moderate airspeed
Figure 3.- (Continued).Northrop P-61A airplane.
NACA ARR No. 5Z22 rig. 3C
.08
,04
o
.04
0 From straight flight, 304 mph
0 From turning flight, 303 mph
I
NATI3ML A)VISORY COMMITTEE & ‘
FOR AERONAm ICS
L
,-
/’
30 20 10 0 10 20 30
up Left aileron deflection, deg Down
(c) Rolls at high airspeed
Figure 3.- (Concluded).Northrop p-61A airplane.
INACA A.RRNo. 5322 Fig. 4a
.,. —
-.. –
. .
0 Yrom straight fli~>t, 142 mph
CJ From turning flight, 14s4mph
30 20 10 0 10 a) 30
Left Total aileron deflection, deg Right
(a) Rolls at low airspeed
Figure 4 (a to c).- Cornparisonbetween flight determinations.of maximum
pb/2V in rudder-fixed aileron rolls from strai~ht,
unbanked flight and from steady, turning flight. Clean condition, normal
rated power. Lookheed PV-1 airplane.
,, ,,.,,,, ,, ... , ,, ,,, ,. ,. ... -,,,-- —.,,, ... ........ ...-
NACA ARR No. 5E22 l?ig.4b
.08
%1
d?
.04
o
.04
0 From etraight flight, 182 mph
Cl llromturning flight, 183 mph
I
NAT1OWL
dOR
————.
(>.— “-
.— ——
30 a Ml 0 10 20 30
Loft Total aileron deflection, deg Right
(h) Rolls at moderate airspeed
Figure 4.- (Continued).LockileedPV-1 airplane.
NACA ARR No. fS322
.04
,04
O From straight flight, 222 mph
0 From turning flight,223 mph
NATI3NAL AXI SOJ3rc w ITTEE
FOR AERONA“mICS
30 20 10
Left Total aileron
(c) Rolls at
4
•1
o 10
deflection, deg
hi@ airspeed
20 30
Right
Figure 4.- (concluded).Lockheed PV-1 airplane.
NACA ARR No. 5E22
O From strai,ght flight
Cl From turnin~ flight
Fig. 5
30 A 10 0 10 20 30
Lsft Total aileron deflection,deg Right
rij
I?igure5.- Conparisonbetween flight determinations of change in sideslip
angle correspondingto maximum rolling velocity in rudder-
fixed aileron rolls from straight,unbanked flight and from steady, turn-
ing flight, Clean condition,power for level flight. Martin B-26B-21 air-
plane.
NACA AM No. =22 Fig. 6
o
al
I-1
1’
o
0 From straight flight
0 From turning flight
-— .——
f>—1 ‘___l -----0 u 0 183 mph
O 188 mph
T
.——
E
/
—.. .-—
NATIoI?fIL ADVISORY C3MMITT
OR AER9NAUTICs
—. —..
J=: :*-7 OK ~ - m
0 222 mph
O 225 mph
.—
—
t
.—.—
— .—. -—
+i [D p.W===&
O 304 mph
0 303 mph
—-
}
/.
30 20 10 0 10 20 30
up Left aileron deflection, deg Down
Figure 6.- Comparison between flight determinations of changa in sideslip
—
angle corresponding to maximum rolling velocity in rudder-
fixed ailero~ rolls froa straight, unbmked flight aaclfrom staady, turn-
ing flight, Clean condition, normal rated power. Northrop P-61A airplane.
\
NACA .4RRNo. 5E22
o From straight flight
0 From turning flight
*10
a
2
n Ofi
o
o J?
n
u
n m O 142 mph
D 144 mph
—. —
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A 10 —
1?.LTIQN& ADV160RY C(lMMITTlE
2 F()R AllR)NAUTI(;s
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a+%
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.——.
.ri
rn
+J 0
0 182 mph
2
Y
0 183 mph
.2E
:.3 10
G
~
w’10---—--
$
Z
— —
Q0 —— H . — — ck- 0
0 222 mph
0 223 mph
— — — —
z
$10 1“
30 20 10 0 10 20 30
Left Total aileron deflection, deg Right
Figure 7.- Comparison between flight determinations of change in sideslip
angle corresponding to maximum rolling velocity in rudder-
fixed aileron rolls frbm straight,Unbatied flight and from steady, turn-
ing flight. Clean condition, normal rated power. Lockheed PV-1 airplane.
“..—. . . . .
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A comparison of two flight-test procedures for the determination of aileron control capabilities of an airplane

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