Propulsion Controlled Aircraft System

Initiated in 1989, the Propulsion Controlled Aircraft (PCA) system was developed and flight-tested at NASA Dryden, with the goal being to help pilots land safely in the event that flight control components were dis­abled. PCA automatically provides computer-controlled variations in engine thrust that give pilots adequate pitch, yaw, and roll authority to fly their aircraft. The PCA system was tested and initially demonstrated on the HIDEC F-15. In simulator studies, NASA demonstrated the PCA concept on more than a dozen other commercial and military aircraft. The PCA system integrates the aircraft flight control and engine con­trol computers to manage engine thrust and ensure adequate aircraft control. When the PCA system is activated, moving the control column aft causes the engine thrust to be automatically increased, and the air­craft begins to climb. Forward movement of the control column results in reduced thrust, and descent begins. Right or left movements of the control column produce differential engine thrust, resulting in the air­craft yawing in the direction of the desired turn. Flight-testing with the HIDEC F-15 was carried out at landing approach speeds of 150 knots with the flaps down and between 170 and 190 knots with the flaps retracted. At the conclusion of testing, the HIDEC F-15 accomplished a successful landing using the PCA system on April 21, 1993, after a flight in which the pilot used only engine power to turn, climb, and descend for approach to the runway.[1269]

The NASA Dryden F-15A HIDEC testbed had originally been obtained from the Air Force in January 1976. During its career with NASA, it was involved in more than 25 advanced research projects involving aerodynamics, performance, propulsion control, systems integration, instrumentation development, human factors, and flight-test techniques before its last flight at Dryden, in October 1993.[1270]

A similar propulsion controlled aircraft approach was later evaluated and publicly demonstrated using a modified three-engine McDonnell – Douglas MD-11 jet airliner in a cooperative program between NASA, McDonnell-Douglas, Pratt & Whitney, and Honeywell. Pratt & Whitney modified the engine control software, and Honeywell designed the soft­ware for the MD-11 flight control computer. Standard autopilot controls already present in the aircraft were used along with the Honeywell PCA software in the reprogrammed MD-11 flight control computers. NASA Ames performed computer simulations in support of the PCA program. On August 29, 1995, NASA Ames test pilot Gordon Fullerton successfully landed the PCA-modified MD-11 at Edwards AFB with an engine out after activating the aircraft’s auto-land system.[1271] Simulator testing of a PCA system continued using a NASA Ames-FAA motion-based Boeing 747 simulator, with pilots making about 50 landings in the simulator. Additional simulation research by Ames resulted in further tests of the PCA system on B-747, B-757, MD-11, and C-17 aircraft. NASA Dryden test pilots flew simulated tests of the system in August 1998 in the NASA Ames Advanced Concepts Simulator. Ten pilots were involved in these tests, with 20 out of 20 attempted landings successfully accomplished. PCA technology can be used on current or future aircraft equipped with digital flight control systems.[1272]