Use Of Programmable Force Feel For Handling Qualities Improvement In A Helicopter Velocity Flight Control System

Extensive flight experience with helicopter velocity flight control systems has shown that conventional thinking regarding pilot's control force-feel characteristics must be modified for this type of control system. Simpler control systems, including those with rate augmentation, require a relatively high level of pilot's control activity because the pilot must provide attitude and speed stability by control inputs. Because of this, pilots have developed an aversion to controls with high feel forces. Velocity control systems, on the other hand, provide full and continuous stabilization of attitude and speed so that no control manipulation is required to check divergences. Control inputs with velocity control therefore are much less frequent and of relatively small amplitude. Some premium is, however, placed on smoothness of control motion due to the nature of the transfer functions relating control motions to aircraft responses such as attitude, engine torque, etc. The paper presents an analysis in terms of these transfer functions from which is developed the design of a programmable force feel system to improve the short term handling qualities of the control system. Such a system applied to the longitudinal axis of the CH-47B TAGS system has been flight tested.