Some measurements of flying qualities of a Douglas D-558-II research airplane during flights to supersonic speeds Page: 2 of 27
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P NACA RM .53AO6 3 1176 01437 5811 .
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
SOME MEASUREMENTS OF FLYING
QUALITIES OF A DOUGLAS D-558-II RESEARCH AIRPLANE DURING
FLIGHTS TO SUPERSONIC SPEEDS
By Herman 0. Ankenbruck and Theodore E. Dahlen
During demonstration flight tests of the air-launched Douglas D-558-II
rocket-powered airplane, some measurements of the dynamic lateral stability
and lateral and longitudinal trim were obtained in flights up to a Mach
number of about 1.87 and to an altitude of about 67,000 feet.
The results indicated that the airplane flying at supersonic speeds
in low density air had poor dynamic lateral stability which became more
objectionable as Mach number was increased to 1.85. The amplitudes of
the oscillations increased as angle of attack decreased. A simplified
analysis indicated the directional stability parameter Cn decreased
considerably as Mach number increased from 1.2 to 1.85. With power on
and rudder free a lateral oscillation occurred at Mach numbers from
1.1 to 1.4 which did not occur when the rudder was locked. The rudder
floating tendency was reversed when power was turned off at the higher
supersonic speeds. There were no changes in lateral trim in the tran-
sonic region, and the apparent stabilizer effectiveness decreased to
about one-third the subsonic value at supersonic speeds.
The National Advisory Conmittee for Aeronautics is conducting
research at transonic and supersonic speeds at the NACA High-Speed
Flight Research Station at Edwards Air Force Base, Calif., by use of
research-type aircraft. One of the aircraft, the Douglas D-558-II
(BuAero No. 37974), was recently modified in order to explore the
problems of controlled flight in the supersonic speed range. This
paper is concerned with this airplane. The modification consisted
primarily of an increase in rocket propellant and the use of the air-
launching technique as applied in the X-1 project. During the demonstra-
tion of the modified aircraft by the Douglas Aircraft Co., attempts to
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Ankenbruck, Herman O. & Dahlen, Theodore E. Some measurements of flying qualities of a Douglas D-558-II research airplane during flights to supersonic speeds, report, March 10, 1953; (digital.library.unt.edu/ark:/67531/metadc59514/m1/2/: accessed September 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.