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Wind Tunnel Investigation of a Full Span Retractable Flap in Combination with Full Span Plain and Internally Balanced Ailerons on a Tapered Wing

SUMMARY

An investigation was made_in the LMAL 7— by lwaoot
tunnel of a 20—percent—chord full-span retractable flap in
combination with 8—percent-chord full—span plain and in?
ternally balanced ailerons on a semispan model of the ta-
pered wing of a typical fighter airplane. The full—span
flap fits into a cut—out ahead of the aileron to conform
to the original wing contour when in the retracted posi-
tion and moves down and back to its extended position.
Increments of maximum lift coefficient of approximately
1.3 and 1.5 were obtained from the full—span flap at de—
flections of 30° and 50°. respectively. The-aileron ef—
fectiveness for a deflection range of 115° is thought to
be adequate in the flap—retracted condition. With the
flap fully extended. the aileron effectiveness was about
50 percent greater than with the flap retracted. A re—
duction of aileron effectiveness of approximately 40 per—
cent relative to the aileron effectiveness with the flap
retracted appeared unavoidable at certain intermediate
"flap positions. The internal balance reduced the esti-
mated aileron stiok forces to acceptable values for all
flap positions and deflections along a selected path.

INTRODUCTION

One of‘the problems arising from the increased speed
and wing loading of modern airplanes is the difficulty of
obtaining high lifts for landing and take—off without in—
pairing lateral control. In order to obtain-solutions to
this problem. the NAGA is investigating, an a semispan
model of the tapered wing of a modern fighter atrplane.
lateral-control devices that appear promising from PP371-
ous wind—tunnel tests.
The present tests of an 8-percentéchord full-span ai-
leron on a tapered wing with a full-span retractable flap
may be considered an extension of the work reported in
references 1 and 2. The object of the wind—tunnel tests
was to determine the lift characteristics-and the aileron-
control characteristics for various positions and deflec—
tions of the flap. Most of the tests were made with a
'sealed internally balanced aileron with small overhang in
order to obtain data over a large aileron deflection range;
with the flap retracted. comparative tests were made of the
aileron with the seal removed. The results indicated that
an aileron deflection of :150 would provide adequate rate
of roll if the aileron were sealed;'the sealed internal
balance was therefore increased to the maximum overhang
permissible with an aileron deflection of $150. With the
large internal balance. tests were made to determine the
hinge-moment characteristics of the aileron with the flap
retracted. Some additional tests were made with the flap
extended. primarily to obtain lift and rolling—moment
data at angles of attack or flap positions not investigat—
ed with the small owerhang.

The stick forces and the rates of roll were estimated
for an airplane with :15 aileron linkage for several flap
positions along a selected flap path. With the flap fully
extended. two arrangements of the flap and aileron were
investigated; one of these arrangements retained the'215o
aileron linkage, but the other required a differential
linkage.