Investigation of the application of direct translational control to VTOL aircraft.

Abstract

The possibility of employing a mixed translation and attitude control system through a single cockpit stick has been investigated for low-speed flight control of VTOL aircraft. In this way it would be possible to command more directly low-speed longitudinal and lateral translations and to reduce the amount of installed thrust required for attitude control of VTOL aircraft. The maneuvering translation concept is not to be confused in the longitudinal plane with the more gross thrust vectoring requirement necessary for transition to wing-borne flight. In the current study, combined control schemes were evaluated on the longitudinal axis of a simulated VTOL aircraft during performance of a multiaxis IFR (instrument flight rules) hover task. With pilot opinion as a measure, some combinations of attitude and translational controls were found to be more satisfactory than attitude controls alone. Systems receiving the best ratings were 1) fully stabilized airframe provided with direct translation acceleration control and 2) stick steering control of attitude with open-loop shaping of the translational control to give pseudo-velocity control. Acceptable translational controls seem particularly well suited to IFR hover tasks, since they allow control movements to be minimized. There were definite indications that the larger control movements associated with VFR (visual flight rules) flight, where the pilot is less inhibited by the instrument scanning process, would result in mismatching of the attitude and translation controls.