Wind-tunnel testing with a rotary-balance apparatus to simulate aircraft spin motions

Experiments have been conducted in the Ames 12-Foot Pressure Wind Tunnel on a simple airplane-like model using a rotary-balance apparatus to simulate a steady spin motion at high angles of attack. Tests were run at Mach numbers of 0.1 and 0.25 over a wide Reynolds number range with the angle of attack varying from 45 to 90 deg. During previous tests of the same research model, some difficulties were experienced with measurement accuracy in the low-to-medium range of Reynolds number because of limitations in the sensitivity of selected force balances. For the present tests, special balances were built to provide accurate measurements of the nose and tail contributions to spin motions and improvements were made to the overall test apparatus. The results of this test, including some interesting hysteresis effects with spin rate, are described. Some of the problems associated with rotary-balance tests at high Reynolds numbers are discussed. A new large-scale rotary apparatus now nearing completion for use in the Ames 12-Foot and 11- by 11-Foot Wind Tunnels is described briefly.