NASA is studying a potential application of its recently completed Propulsion Controlled Aircraft (PCA) system, which would allow a twin-engined aircraft to survive a catastrophic engine and flight-control failure.

The PCA was developed following the 1989 crash of a McDonnell Douglas DC-10 with disabled flight controls. The crew of the critically damaged DC-10 managed a crash landing, using engine power alone to control the flight path. NASA, together with MDC, Honeywell and Pratt & Whitney subsequently developed a system in which flight commands would be interpreted by a modified full-authority digital engine-controller. Successful approaches and landings were demonstrated in 1995 with a modified MD-11.

Although the system has applications to tri-jets and four-engined aircraft, the novel use of the PCA on twins is unexpected. NASA believes that the system could be used to transfer fuel in a damaged aircraft to shift the aircraft's centre of gravity (CG) in favour of the operating engine. The revised CG "-would at least allow the crew to crash land wings level", says NASA. The PCA is being investigated for several other uses, including reversionary control for the proposed Boeing 747-500X/600X.

Source: Flight International