Pilot Describing Function Measurements in a Multiloop Task

An experimental program to measure pilot describing functions in a multiloop control task is described. The basic objective of the program was to provide the data essential for refinement of the multiloop pilot model, which has previously been based on a rational extension of single-loop experimental results. The piloting task was tracking a bank-angle command input. The displayed quantities were bank-error and aircraft yaw rate. The pilot had both aileron and rudder controls. For four of the five configurations, the aircraft was unstable and the pilot had to close a yaw-rate loop. One configuration was stable and could be flown single-loop, bank- angle-to-aileron.