NASA Dryden X-Press - September 1995
NASA program achieves first propulsion-controlled landing of a transport aircraft
by J. D. Hunley, External Affairs Office
NASA research pilot and former astronaut Gordon Fullerton recently landed a McDonnell- Douglas MD-11 transport aircraft here using only engine power for control.
The milestone flight on Aug. 29 was part of a NASA project, initiated by Bill Burcham, chief of Dryden's Propulsion Branch, to develop a computer-assisted engine control system that enables a pilot to land a plane safely when its normal control surfaces such as elevators, rudders, and ailerons are disabled.
Following several incidents in which hydraulic failures resulted in loss of part or all of an aircraft's flight controls, notably the crash of a United Airlines DC-10 at Sioux City, Iowa, in 1989, NASA started developing a propulsion-controlled aircraft (PCA) system in which engine thrust provides the control needed to land an aircraft safely.
Gordon Fullerton had previously landed a NASA F-15 research aircraft using a similar PCA system in April 1993. The recent landing was the first one ever performed in an actual transport aircraft - the wide body MD-11 that replaced the earlier DC-10.
The success of the program was the result of a partnership between NASA and McDonnell-Douglas Aerospace, St. Louis, Mo., and Pratt & Whitney, along with Honeywell, which designed the software used in the aircraft's flight control computer.
"We actually flew the airplane today to a PCA landing two months ahead of schedule and approximately $3 million under the cost that we had originally signed up for," said NASA project manager Bob Baron, immediately following the event.
Following an earlier flight at Yuma, Ariz., in which the MD-11 did not land, a combined crew including Gordon Fullerton and Douglas Aircraft's flight test team headed by pilot John Miller, made three practice approaches at Dryden before making the initial landing at 11:38 a.m. PDT. The test team then made a second landing at 12:18 p.m., proving that the PCA concept was feasible for a commercial transport.
"What is most impressive about the system is the precision of its control," said Fullerton. "From the first time that we turned it on, John Miller and I were amazed at how accurately it can hold a commanded altitude and steer to exactly a precise heading. The result is that you can bring it in, not only for a survivable crash landing, but a precise normal landing, which is what we did."
The PCA system uses a standard autopilot control already present in the cockpit, together with the new programming in the aircraft's flight control computers. The PCA concept is simple - for pitch control, the program increases thrust to climb and reduces thrust to descend. To turn right, the autopilot increases the left engine thrust while decreasing the right engine thrust. Since thrust response is slow, and the control forces are relatively small, a pilot would require extensive practice and intense concentration to do this task manually. Using computer- controlled thrust greatly improves flight precision and reduces pilot workload.
beyond being able to have controled flight when normal controls (alierons, elevator, rudder) are unuseable this research presses fwd twards aircraft controlled soley by thrust vectoring. Think of the systems and weight savings if the aircraft didn't need conventional controls.
