Human Describing Functions Measured in Flight and on Simulators

Comparisons have been made between human describing functions measured in flight and on the ground using two different types of ground simulation. A T-33 variable-stability airplane was used for the in-flight measurements. The ground tests were conducted in the T-33 airplane on the ground with simulated instrument flight and also on a general-purpose analog computer in conjunction with a contact analog display. For this study, a multiple-degree-of-freedom controlled element was used in a single-loop compensatory tracking task. The input disturbance in each case consisted of the sum of 10 sine waves with a corner frequency of 1.5 radians per second.