Military Aviation


F-8 Digital Fly-By-Wire aircraft

Externally identical to a standard U.S. Navy F-8C Crusader, the F-8 Digital Fly-By-Wire (DFBW) aircraft had its control system replaced initially by a primary system using an Apollo digital computer. The backup system used three analog computers.

When the pilot moved the airplane’s stick and rudder, electronic signals went to the computer, which would generate signals to move the control surfaces. The system was designed so that the digital fly-by-wire aircraft would handle almost identically to a standard F-8C.

To carry the computers and other equipment, the F-8 DFBW team removed the aircraft’s guns and ammunition boxes.

Later, in Phase 2, the aircraft used three IBM AP-101 computers for its flight control system.

The F-8 DFBW flight research project validated the principal concepts of all-electric flight control systems now used on nearly all modern high-performance aircraft and on military and civilian transports.

The first flight of the 13-year project was on May 25, 1972, with research pilot Gary E. Krier at the controls of the modified F-8C Crusader that served as the testbed for the fly-by-wire technologies. The project was a joint effort between the NASA Flight Research Center, Edwards, California, (now the Dryden Flight Research Center) and Langley Research Center.

A total of 211 flights

It included a total of 211 flights.

The Apollo hardware jammed into the F-8C. The computer is partially visible in the avionics bay at the top of the fuselage behind the cockpit. Note the display and keyboard unit in the gun bay. To carry the computers and other equipment, the F-8 DFBW team removed the aircraft’s guns and ammunition boxes.

The last flight was on Dec. 16, 1985, with Dryden research pilot Ed Schneider at the controls.

The F-8 DFBW system was the forerunner of current fly-by-wire systems used in the space shuttles and on today’s military and civil aircraft to make them safer, more maneuverable, and more efficient. Electronic fly-by-wire systems replaced older hydraulic control systems, freeing designers to design aircraft with reduced in-flight stability.

Fly-by-wire systems are safer because of their redundancies. They are more maneuverable because computers can command more frequent adjustments than a human pilot can. For airliners, computerized control ensures a smoother ride than a human pilot alone can provide. Digital-fly-by-wire is more efficient because it is lighter and takes up less space than the hydraulic systems it replaced. This either reduces the fuel required to fly or increases the number of passengers or pounds of cargo the aircraft can carry.

Digital fly-by-wire is currently used in a variety of aircraft ranging from F/A-18 fighters to the Boeing 777.

The DFBW research program is considered one of the most significant and most successful NASA aeronautical programs since the inception of the agency.

Source: NASA; Photo credit: NASA

Dario Leone

Dario Leone is an aviation, defense and military writer. He is the Founder and Editor of “The Aviation Geek Club” one of the world’s most read military aviation blogs. His writing has appeared in The National Interest and other news media. He has reported from Europe and flown Super Puma and Cougar helicopters with the Swiss Air Force.

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