Wittman, R. B. | Search NASA

NASA NTRS1977

V/STOL hover stability impact on hover control task

Longitudinal static stability requirements for V/STOL aircraft are discussed in terms of vertical landing on a small ship at night, response of the aircraft to air turbulence, and hovering flight. The increased pilot workload encountered under these flight conditions is considered. Results of a flight simulation study performed to evaluate a specific hover control task, two control systems - attitude rate command and translational velocity command, and the pilots' performance with and without turbulence are reported. It is concluded that the translational velocity command system provides the control requirements for good spot hovering capability and reduced pilot workload.

Whitaker, A. B.↗

NASA NTRS1975

Stabilizer flutter investigated by flight test

Flight flutter tests were conducted on an experimental airplane which resulted in the successful prediction of a limited amplitude stabilizer flutter at supersonic speeds. The flutter obtained was unusual in that fore and aft bending of the stabilizer carry-through structure contributed to the flutter condition. During flight tests the impending flutter condition was observed from force per unit amplitude, damping coefficient, and frequency measurements. A description is given of the physical and operational characteristics of the test equipment and telemetering facilities. A flutter analysis using measured modes and incompressible two-dimensional strip air forces yielded a conservative flutter speed. Sled tests of a similar stabilizer configuration had lead to the conclusion that flutter would not be encountered. Certain overall conclusions are reached regarding this particular flight flutter testing program and the need for a concerted research effort in this field.

Baird, E. F.↗