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The Japanese Quiet Short Take Off and Landing experimental aircraft named ASKA was developed and flight tested during 1977 till 1989. The control system hard and software were examined by the functional mock-up with using the actual hardware. The small longitudinal limit cycle was observed in the closed loop test when the Pitch Control Wheel Steering software was on in the mock-up testing. In this paper, first, the method to analyze and to expect the limit cycle based on the describing function was shown. The limit cycle was induced due to the nonlinearities in the automatic control mechanism. The nonlinearities in the hardware were examined to make the model to simulate the system on the computer. The method was shown effective to predict the limit cycle in the mock-up. Second, with using the flight measured dynamics, the limit cycle was concluded as on border line between existing and not, which coincides with the actual flight result.

Control system functional mock-up tests were conducted with ASKA, a quiet short take-off and landing aircraft. Simulation was effectively simplified by omitting the control system right half side and shortening the system's straight sections. Characteristic differences were compensated for by changing cable tension, with simulation “fidelity” being sufficient to check each area of concern. All test measurements were precisely taken, and a “filtering sampler,” an anti-aliasing device/technique, was newly designed and used for digital data acquisition. The mock-up tests significantly contributed to the control system development by providing data to refine the stability and control augmentation system, by enabling accomplishment of system and component clearance tests, by determining unexpected phenomena, and by allowing performance of experimental studies on possible critical problems.