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National Advisory Committee for Aeronautics, Report - Lift and Drag Characteristics and Gliding Performance of an Autogiro as Determined in Flight

The results of flight tests made by the National Ad-
visory Committee for Aeronautics on a Pitcairn “POA—2’ ’
autogiro are presented in this report. Lift and drag
coefficients with the propeller stopped have been deter-
mined over approximately a 90° range of angles of attack.
Based on the sum of fired-wing and swept—disk areas,
the maximum lift coezficient is 0.895, the minimum drag
coefi'icient with propeller stopped is 0.015, and the maxi-
mum L/D with propeller stopped is 4.8. Lift coeficients
were found also with the propeller delivering positive
thrust and did not difier consistently from those found
with propeller stopped. Ourves of gliding performance
included in this report show a minimum vertical velocity
of 1 6 feet per second at an air speed of 36' miles per hour
and a flight-path angle of -17'°. In vertical descent the
vertical velocity is 35 feet per second.
Research on the autogiro has been undertaken by
the National Advisory Committee for Aeronautics in
connection with the study of the general problem of
safety in flight. The essential characteristic of the
autogiro that distinguishes it from conventional air-
planes is that the velocity of the lifting surfaces with
respect to the air is almost entirely independent of the
velocity of the machine as a whole. The value of this
attribute with respect to safety lies in the increase in
the useful range of air speeds at which flight may be
maintained.
The determination of lift and drag characteristics
was decided upon as the initial step into an extensive
program of research because of the lack of reliable
full-scale information on the fundamental aero—
dynamic characteristics of the autogiro and the need
to establish clearly a datum to which further work will
be referred. The curves and data contained in the
body of this report constitute, so far as is known, the
first authentic full-scale information concerning auto—
giro characteristics that has been published. This re-
port presents the results of a series of glide tests, made
to determine the lift and drag characteristics of a
Pitcairn POA—2 autogiro over the full range of angles
of attack. The tests were performed by the National
Advisory Committee for Aeronautics at Langley
Field, Va.