The high speed possibilities of
a 0.16 scale model of the Burnelli Aircraft Corporation XB-AB-3
design were investigated in the N. A. C. A. 8-foot high speed wind
tunnel at Mach numbers from 0.18 to 0.65 with corresponding Reynolds
numbers of 2,500,000 to 7,000,000.
Drag measurements were made with
fixed transition in order to provide a better basis for the
estimation of the full-scale drag coefficient increments. Static
pressure measurements were made in order to estimate the critical
speed. The rate of air flow and internal head loss in the cooling
ducts were also measured.
At 20,000 feet altitude and at 0-degree angle of
attack the model would have a critical speed of approximately 376
miles per hour. However, if the hatch and fuselage lower surface
were redesigned the critical speed under the same conditions could
probably be increased to approximately 440 miles per hour. The
external drag of the duct appeared too high indicating that a more
suitable design locating the exit farther aft would be
The Materiel Division of the
United States Army Air Corps requested the N. A. C. A. to
investigate the high-speed possibilities of the Burnelli Aircraft
Corporation XB-AB-3 design. A model of this airplane suitable for
testing in the N. A. C. A. 8-foot high-speed wind tunnel was
provided by the Burnelli Aircraft Corporation.
The test programme was arranged
by representatives of the Material Division, the Burnelli Aircraft
Corporation, and the N. A. C. A. to provide data to aid in the
performance estimates and to study the compressibility effects as
outlined in reference 1. The Mach number range for most of the tests
extended from 0.18 to 0.65 giving a corresponding Reynolds Number
range of 2,500,000 to 7,000,000 based on the mean aerodynamic chord,
24.34 inches, of the complete model.
Static pressure measurements
were taken at the critical locations on the model in order to
determine the effects of compressibility and to estimate the
critical speed. The drag measurements were made with transition
fixed at the probable full-scale location whenever necessary in
order to provide a better basis for estimation of the full-scale
drag coefficient increments. The rate of air flow and internal head
loss in the cooling ducts were also measured.
The tests were conducted with
the assistance of Messrs. Berkok and Applegate, representatives of
the Burnelli Aircraft Corporation, and Mr. J. A. Roche of the
Materiel Division Liaison Office.