A Study of an Open-Loop System for Decoupling Airspeed and Flight Path Angle Control.

Using an in-flight simulator, a simple longitudinal decoupling concept was compared with conventional airplane characteristics for the approach and landing tasks. The decoupling system allowed the pilot to command flight path angle changes with the stick with little or no accompanying speed change; likewise, speed changes with only small accompanying flight path changes could be made with throttle only. The unique feature of the concept is that it is an open loop (that is, non-feedback) control system. Results indicate that in calm air and up to moderate levels of turbulence the decoupling system provides a substantial reduction in pilot workload.