Preliminary Transonic Flutter Investigation of Models of T-Tall of Blackburn NA-39 Airplane Page: 2 of 35
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NACA RM SL58D10
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
RESEARCH MEMORANDUM
for the
Office of Naval Research
PRELIMINARY TRANSONIC FLUTTER INVESTIGATION OF MODELS
OF T-TAIL OF BLACKBURN NA-39 AIRPLANE
By George W. Jones, Jr., and Robert W. Boswinkle, Jr.
SUMMARY
A transonic flutter investigation has been made of models of the
T-tail of the Blackburn NA-39 airplane. The models were dynamically
and elastically scaled in accordance with criteria which include a
flutter safety margin. The investigation is to be considered prelimi-
nary in that only estimated airplane properties were available for the
scaling. The investigation was made in the Langley transonic blowdown
tunnel and covered a Mach number range from 0.71 to 1.15 at simulated
altitudes extending to below sea level.
The results of the investigation indicated that, if the models
simulated the airplane in all important respects, the airplane would
have at least a 52 percent margin of safety in stiffness at sea level
at Mach numbers up to 0.90. Symmetric stabilizer pitching oscillations
(which may have been symmetric flutter) and antisymmetric flutter
were obtained at Mach numbers of about 0.95 and 11.00, respectively, at
altitudes as high as about sea level. Near a Mach number of 1.00, a
region in which the random tunnel turbulence excited low damped anti-
symmetric oscillations of the model extended to altitudes above sea
level. The relationship to the airplane of the low damped oscillations
obtained with the model is not known.
INTRODUCTION
At the request of the Office of Naval Research a transonic flutter
investigation has been made of models of the T-tail of the Blackburn
NA-39 attack airplane. The T-tail of the airplane consists of an all-
movable sweptback stabilizer mounted on top of a sweptback fin. TheF- - E
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Jones, George W., Jr. & Boswinkle, Robert W., Jr. Preliminary Transonic Flutter Investigation of Models of T-Tall of Blackburn NA-39 Airplane, report, April 15, 1958; (https://digital.library.unt.edu/ark:/67531/metadc53280/m1/2/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.