Some measurements of the buffet region of a swept-wing research airplane during flight to supersonic Mach numbers Page: 2 of 16
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NACA RM L53D06 3 1176 01436 9848
NATIONAL ADVISORY COvMMITEE FOR AERONAUTICS
SOME MEASUREMENTS OF THE BUFFET REGION OF A SWEPT-WING
RESEARCH AIRPLANE DURING FLIGHTS TO
SUPERSONIC MACH NUMBERS
By Thomas F. Baker
Measurements of the intensity of buffeting experienced by the
Douglas D-558-II research airplane have been made in the Mach number
range from 0.85 to about 1.10. The values of airplane normal-force
coefficient attained varied from about 1.0 at a Mach number of approxi-
mately 0.9 to above 1.5 at a Mach number of approximately 1.06.
Buffeting was encountered by the D-558-II airplane at both sub-
sonic and supersonic Mach numbers. The intensity of the buffeting
varied with Mach number and with airplane normal-force coefficient, but,
regardless of Mach number, only low-intensity buffeting was experienced
at values of airplane normal-force coefficient less than 0.4. High-
intensity buffeting was not encountered at Mach numbers greater than
about 0.925 nor at normal-force coefficients less than 0.65. The
absence of high-intensity buffeting during the maneuvers to high lift
at supersonic speed indicates that no maneuverability restrictions,
insofar as buffeting is concerned, will be necessary for similar air-
planes during supersonic flight. The significant buffet frequencies,
as regards amplitude and occurrence, corresponded to the first modes
of symmetrical wing bending and wing torsion.
Buffeting may be defined as an aerodynamically induced structural
vibration of one or more components of an airplane. The origin of
buffeting lies in the fluctuating pressures of unsteady flow associated
with separation. Knowledge of the buffeting encountered by full-scale
airplanes at transonic speeds is of interest, since the onset of
buffeting at low values of lift can restrict the maneuvering range of
the airplane. This paper presents the results of some measurements
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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/m1/2/: accessed November 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.