Some Measurements of the Buffet Region of a Swept-Wing Research Airplane During Flight to Supersonic Mach Numbers Page: 4 of 16
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NACA RM L53D06 " 0 5
AIRPLANE AND INSTRUMENTATION
The Douglas D-558-II airplanes have sweptback wing and tail sur-
faces and were originally designed for combination turbojet and rocket
power. The airplane used in the present tests, however, has the turbo-
jet engine removed, has no air inlet or exhaust ducts, and is powered
solely with a rocket engine exhausting from the rear of the fuselage.
Photographs of the airplane are shown in figure 1 and a three-view
drawing is shown in figure 2. Pertinent airplane dimensions and physi-
cal characteristics are listed in table I. The airplane is equipped
with an adjustable stabilizer and both leading-edge slats and stall-
control fences are incorporated on the wing. The wing slats can be
locked in the closed position or can be unlocked.
Standard NACA recording instruments, synchronized by a common
timer, were used to measure all quantities pertinent to this investiga-
tion. The airspeed system was calibrated at all Mach numbers by the
NACA radar phototheodolite method (ref. 1). The accuracy of the Mach
numbers presented herein is estimated to be *0.025.
TESTS AND PROCEDURE
The data presented in this paper were obtained at altitudes
varying from 30,000 to 63,000 feet in the Mach number range from 0.85
to 1.2. The Reynolds number varied from 6 x 106 to 21 X 106. The
data were taken with the airplane in the clean (slats-locked-closed)
condition during rocket-powered climbs and during turns and pull-ups
performed at high altitudes after the exhaustion of rocket fuel. No
significant difference was found between power-on and power-off data
that could be attributed to the presence of power.
The intensity of the buffeting was determined by measuring the
amplitude of buffet-induced fluctuations in normal acceleration and
converting the incremental accelerations to values of incremental
normal-force coefficient LSCN. The accelerometer used for buffet-
intensity determination was an air-damped instrument having a natural
frequency of 10.5 cycles per second. The response of this instrument
varies with air density and with forcing frequency. The incremental
acceleration data obtained from it have been corrected for both
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Baker, Thomas F. Some Measurements of the Buffet Region of a Swept-Wing Research Airplane During Flight to Supersonic Mach Numbers, report, May 28, 1953; (digital.library.unt.edu/ark:/67531/metadc59778/m1/4/: accessed January 22, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.