Development and Flight Test of an Emergency Flight Control System Using Only Engine Thrust on an MD-11 Transport Airplane

An emergency flight control system that uses only engine thrust, called the propulsion-controlled aircraft (PCA) system, was developed and flight tested on an MD-11 airplane. The PCA system is a thrust-only control system, which augments pilot flightpath and track commands with aircraft feedback parameters to control engine thrust. The PCA system was implemented on the MD-11 airplane using only software modifications to existing computers. Results of a 25-hr flight test show that the PCA system can be used to fly to an airport and safely land a transport airplane with an inoperative flight control system. In up-and-away operation, the PCA system served as an acceptable autopilot capable of extended flight over a range of speeds, altitudes, and configurations. PCA approaches, go-arounds, and three landings without the use of any normal flight controls were demonstrated, including ILS-coupled hands-off landings. PCA operation was used to recover from an upset condition. The PCA system was also tested at altitude with all three hydraulic systems turned off. This paper reviews the principles of throttles-only flight control, a history of accidents or incidents in which some or all flight controls were lost, the MD-11 airplane and its systems, PCA system development, operation, flight testing, and pilot comments. NOMENCLATURE AFS autoflight system AGL above ground level (radar altitude) CG center of gravity, percent of mean aerodynamic chord (fig. 1) EPR engine pressure ratio FADEC full-authority digital engine control FCC flight control computer FCP flight control panel on cockpit glareshield FDS flight deck simulator FPA flightpath angle G/S glideslope (longitudinal part of ILS command) GW gross weight, lb HDG heading (magnetic direction that the airplane points toward) IAS indicated airspeed, knots IFR instrument flight rules ILS instrument-landing system LOC localizer (lateral part of ILS command) LSAS longitudinal stability augmentation system MCDU multifunction control and display unit MDA McDonnell Douglas Aerospace (St. Louis, Missouri) ND navigation display PCA propulsion-controlled aircraft PFD primary flight display TOGA takeoff–go-around

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