23rd Congress of International Council of the Aeronautical Sciences, 8-13 September, 2002, Toronto, Canada
Paper ICAS 2002-5.3.4 (I.L.)

HIGH ANGLE OF ATTACK APPROACH AND LANDING CONTROL LAW DESIGN FOR THE X-31A

B. Fischer, A. Knoll
EADS Company, Military Aircraft, Flight Dynamics, Munich, Germany

Keywords: estol, x-31a, control laws, vector

The X-31 flight control system enables flying at very high angles of attack, including the poststall regime. This not only offers extreme maneuverability, but also the capability for a steady slow flight. This feature can also be used for the landing approach. Since the landing ground roll distance is proportional to the square of the speed during touchdown, reducing the speed offers a crucial advantage with regard to landing performance. The X-31 VECTOR program is developing and flight-testing this new technique with the automatic Extreme Short Takeoff and Landing (ESTOL). The following presentation shows the development of the ESTOL autopilot control laws, based on the standard X-31 control laws, starting from the design objectives, leading to the present structure. The calculation of the flight path as well as the feedback and the feedforward path for both the longitudinal and the lateral axis are described. The control laws during the derotation phase, immediately before touch down are also presented. Time histories demonstrate the quality of the present solution.

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