X-31 VECTOR - Taking ESTOL to the Ground

Thomas Grohs, VECTOR EADS Chief Engineer, EADS Military Aircraft, Flight Test – MT521, Manching, Germany
Oliver Brieger, FCS/Flying Qualities Engineer, German Aerospace Center, Institute for Flightsystems, Braunschweig, Germany

Abstract

In October 2002 the X-31VECTOR Program started the ‘up & away’ flight test campaign, assessing the performance and robustness of the automated ESTOL (Extremely Short Take-Off and Landing) maneuver to virtual runways at a safety altitude of 5000ft. After a successful completion, the results were used to improve the control law functionality. Following this modification phase and after revisiting the ’up & away’ test environment, the ESTOL maneuver was taken to the ground at Patuxent River Naval Airstation, MD in April 2003. This fully automated maneuver is designed to reduce landing speeds and roll out distances by increasing the angle of attack during the final approach phase up to 24deg.

In close proximity to the ground a fully automated derotation maneuver is initiated to reduce the aircraft’s pitch attitude to a value that guarantees a safe main gear touch down without the threat of a tail strike. The entire ESTOL maneuver consists of a lateral and vertical trajectory capture, intercepting a predefined glide slope with a subsequent build up in angle of attack (AoA) to a maximum selectable value of 24 deg, followed by a derotation and touchdown phase. This paper focuses on the findings of the initial OFP123B ‘up &away’ flight test phase, the required modifications within the control laws of the aircraft to facilitate safe ESTOL landings ‘to the ground’, the flight test approach and execution, as well as the results of the final ESTOL‘to the ground’ flight test phase.