Flight tests of an airplane showing dependence of the maximum lift coefficient on the test conditions Page: 4 of 16
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N.A.C.A. Technical Note No. 622
timer was used in determining the rate of change of angle
of attack and for synchronizing the records from the dif-
The general method employed in the investigation was
to fly the airplane with a known wing loading at the de-
sired altitude at which either a series of steady glides
or a series of pull-ups to the stall at various rates of
change of angle of attack would be made. The flights were
made only when the air was smooth. The air speed, angle of
attack, and accelerations were recorded by the instruments
as functions of time. The approximate time at which the
lift coefficient reached a maximum in each run was obtained
from an inspection of the film records.' The value of the
lift coefficient was then calculated for several instants
at intervals of 1 second or less in the vicinity of the
time at which the maximum value was expected.
In the calculation of the lift coefficients the re-
sultant force acting on the airplane and its direction
relative to the airplane axes were computed from the ac-
celerometor records and the weight of the airplane at the
time of the tests. The lift L, which is defined as the
component of force normal to the wind axis, was determined
from the resultant force and the angle of attack. The
weight for each flight was estimated from the weight of
the airplane and pilot obtained immedfItely after the
flight by correcting for the fuel used ia returning to the
hangar. The dynamic pressure q was obtained by correct-
ing the pressure given by the air-speed head for the posi-
tion error. From the simultaneous values of L and q
so found, the lift coefficient was computed from the rela-
in which S is the area of the wing (171 square feet).
Variation of the Reynolds Number was secured by vary-
ing the wing loading and the altitude at which the tests
were made. For the low Reynolds Number condition, the
airplane was flown with the lightest load and at the highs
est practicable altitude. High Reynolds' Numbers were ob-
tained by flying with full service loading and 500 pounds
of ballast in the front seat and at the lowest practicable
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Soule, H A & Hootman, James A. Flight tests of an airplane showing dependence of the maximum lift coefficient on the test conditions, report, November 1, 1937; (digital.library.unt.edu/ark:/67531/metadc54381/m1/4/: accessed March 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.