NASA 

National Aeronautics and 

Facts

Space Administration 

Dryden Flight Research Center 

P.O. Box 273

Edwards, California 93523 

Voice 661-276-3449 

FAX 661-276-3566 

pao@dfrc.nasa.gov FS-2005-04-041 DFRC 

MD-11 PCA Landing: First jet transport propulsion controlled aircraft landing at Edwards, CA. EC95 43247-3 

PCA Emergency Landing System May

Make Air Travel Safer

You’re flying a large transport plane carrying hundreds of passengers and instantly you are unable to control the airplane. 

The controls system has failed. As a pilot or a passenger, you hope that this scenario never presents itself, but if it did, 

what if there was a way to safely land the airplane by using only the thrust of its engines? With a Dryden-developed 

system known a Propulsion Controlled Aircraft (PCA) this concept has become a reality. 

Propulsion Controlled Aircraft is 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. If used on commercial aircraft, PCA 

and follow on projects could help reduce the number of aircraft accidents. 

NASA’s Dryden Flight Research Center, Edwards, Calif., initiated research into this Propulsion Controlled Aircraft 

technology in 1989 following a series of about ten military and civilian incidents over a 20-year period in which there 

were some 1,200 fatalities caused by the loss of the primary flight-control system in the aircraft. NASA sought to develop 

a backup system for landing a jet using only the throttles for control. 

The PCA system uses standard autopilot controls already present in the cockpit, together with the new programming in the 

aircraft’s flight control and engine-control computers. The PCA concept is simple — for pitch control, the program 

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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. 

From Idea to Flight-Proven Innovation 

In August 1995, NASA pilot Gordon Fullerton performed 

the first-ever engine-only landing in an actual airliner — the 

widebody MD-11 that replaced the earlier DC-10. An 

earlier version of the PCA system had already been validated using both flight simulation and a NASA F-15 

research aircraft, which twice landed successfully. 

For the MD-11, the PCA system used standard autopilot 

controls already present in the cockpit, together with 

programming in the aircraft’s flight control computers. The 

aircraft demonstrated software used in the flight control 

computer that essentially landed the MD-11 without a need 

for the pilot to manipulate the flight controls after activating 

auto-land control. 

The success of the program was the result of a partnership 

between NASA and McDonnell-Douglas Aerospace, St. 

Louis, Mo. (now Boeing), Pratt & Whitney and Honeywell. 

Honeywell designed the software used in the aircraft’s 

flight-control computer, while Pratt & Whitney modified 

the engine-control software. NASA Ames Research Center, 

Mountain View, Calif., assisted in the program by performing simulations. 

The PCA technology is capable of being used on current, 

production and future aircraft with digital flight systems but 

not on older aircraft with analog or mechanical flight 

Gordon Fullerton 

systems. Aircraft manufacturers have decided that a PCA 

system will be valuable for use in the design of future 

airplanes. When they incorporate this for future design, it 

will eliminate the need for a less capable hydraulicsdependent backup flight control system. 

Safety for the Future 

Development on the Propulsion Controlled Aircraft system 

continues at NASA. One of the Agency’s main goals is to 

reduce the aircraft accident rate by a factor five within 10 

years, and by a factor of 10 within 20 years. 

Two new versions of the system, dubbed “PCA-Lite” and 

“PCA-Ultralite” have been tested using a NASA Ames/ 

Federal Aviation Administration motion-based Boeing 747 

simulator. The newer concepts are cheaper and can be used 

on more aircraft, as they do not require changes to the 

airplane’s engine-control computer. 

PCA-Lite allows the pilot to use an aircraft’s existing 

autothrottle and engine trim commands to perform enginesonly landings. Pilots have made about 50 landings using 

PCA-Lite on the 747 simulator. Early results show that 

PCA-Lite is almost as effective as the full system, although 

it does require that the airplane have digital engine controls. 

This system could possibly be used on Boeing 757s, 767s 

and 777s, as well as 747-400s. 

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PCA-Ultralite again uses an airplane’s existing 

autothrottles to control pitch (climb and descent). Unlike 

PCA and PCA-Lite, however, PCA-Ultralite does not 

require digital engine controllers. Thus, the pilot must 

manually control the throttles (thrust) of the left and right 

engines for turning right and left. This is a more difficult 

piloting task, and it is probably too difficult for a pilot who 

has not been trained to use the system. However, results 

Simulation research has tested PCA Ultralite on B-747, B757, MD-11, and C-17 airplanes. NASA Dryden pilots 

participated in tests of the system in August 1998, using the 

NASA Ames Advanced Concepts Simulator. The tests, 

which involved 10 pilots total, resulted in 20 out of 20 

successful landings using the PCA Ultralite system. 

Further testing is needed to see how many airplanes can 

showed that if the pilot’s flight director display was reprogrammed to provide cues for moving the throttles, that 

PCA Ultralite worked very well. 

successfully use PCA Ultralite. 

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