ABSTRACT
NASA has been engaged in research on control of powered-lift aircraft during low-speed flight. Aircraft types have included short take-off and landing transports, vertical and short take-off and landing transports, and short take-off and vertical landing fighters (STOVL). Trajectory control involves control of the aircraft's velocity vector, which, in turn, requires the continuous control of axial and normal force. The influences of the aircraft design on the control system would be realized in feedback and feedforward control commands which are gain scheduled to accommodate variation in flight condition and aircraft configuration within the flight envelope, thus presenting considerable design complexity and difficulty for the designer. Effects of variations in flight condition, aircraft loading and configuration are accommodated by the nonlinear inverse calculations that convert these commands to commanded aerodynamics and then to the associated thrust coefficient and flap setting. The flightpath angle is reduced to acquire the descending approach path, whereupon the deceleration is commenced at 200 knots.
