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National Advisory Committee for Aeronautics, Research Memorandum - Preliminary Tests to Determine the Maximum Lift of Wings at Supersonic Speeds

An exploratory test program was carried out in the Langley 9—inch
supersonic tunnel to determine the maximum lift of wings operating at
supersonic speeds. A variety of wing plan forms of random thickness
distribution were tested at Mach numbers of 1.55, 1.90, and 2. 32 and
Reynolds numbers varying between 0.3 x 105 and 0.7 x 106 at angles of
attack ranging from zero up through the angle at which maximum lift
occurred. In general, at these Mach numbers the value of maximum lift
coefficient was approximately 1.05:0.05; it appeared to be independent
of plan form and decreased slightly with increasing Mach number. No
discontinuities in lift occurred from zero angle of attack through
maximum lift, which was attained at approximately 11-00 angle of attack.

In the Mach number range tested, the lift curves remained linear as high
as 20° to 30° angle of attack. Lift—drag ratios at maximum lift were of
the order of 1. 0.

The designer of supersonic aircraft - particularly the guided—missile
designer — is interested in the maximum loads that can be attained on
wings operating at supersonic speeds. The need for such maximum—load
information is obvious in determining the maximum accelerations that can
be attained by supersonic aircraft and in the structural design of aircraft
components. To provide maximum lift and drag information, tests of
10 wings to high angles of attack were made in the Langley 9—inch super—
sonic tunnel. Only available models were used; hence no comprehensive
study of plan form and wing section was made. The tests were concerned
mainly with plan form inasmuch as it was felt that this was the primary
variable.

The Langley 9—inch supersonic tunnel is a closed-return wind tunnel
in which the humidity and temperature of the air can be controlled
with suitable drying and cooling equipment.