A prototype Lockheed F-22 jet fighter caught fire and burned extensively on the main runway at Edwards Air Force Base on Saturday after experiencing problems during a test flight by a Lockheed company pilot, who escaped with minor injuries.
The Air Force said the pilot decided to make an emergency landing after the aircraft experienced "uncommanded oscillations"--meaning, apparently, that it began to vibrate--during touch-and-go landing maneuvers.
After the emergency landing, the aircraft caught fire, according to a spokeswoman for the Air Force's Aeronautical Systems Division in Dayton, Ohio.
Air Force and Lockheed officials could not say what caused either the flight problems or the resulting fire.
Until now, no major technical problems with the F-22 have been made public. Lockheed, Boeing and General Dynamics are developing the aircraft under a $9.5-billion contract.
The Air Force spokeswoman could not say whether the F-22 actually was destroyed, although the plane burned on the runway for about 1 1/2 hours before the fire was extinguished.
The spokeswoman also said she could not provide a cost estimate for the F-22 prototype. Under its original 1986 contract, Lockheed and its partners built two of the prototypes for $790 million, not including substantial investments of their own.
The loss of the aircraft will have minimal effect on the flight test program, since the prototype already had provided 90% of the data required, the spokeswoman said.