The Air Force acknowledged Tuesday that a Lockheed F-22 prototype "crashed" at Edwards Air Force Base last Saturday, reversing its original statement that the jet fighter had simply made a "forced landing."
The change by the Air Force indicates that the incident was far more serious than previously indicated and involved a loss of control by the pilot. If it is determined that the causes of the crash involved mechanical failure, the mishap could have serious repercussions--technically and politically.
The F-22 is the Air Force's next-generation fighter, designed to replace the F-15 jet starting in the year 2002. The service wants to buy 648 of the aircraft for a total cost of $60.1 billion, making it one of Calabasas-based Lockheed's biggest programs.
Lockheed Chairman Daniel Tellep said Tuesday at the firm's annual meeting that the incident would have very little impact on the program.
The Air Force said it would discontinue the aircraft's flight test program and not attempt to repair the prototype, known as the YF-22, which was apparently destroyed by a fire that followed the crash. The wreckage is being held in a hangar at Edwards.
After hitting the runway with its landing gear up, the aircraft skidded several thousand feet and caught fire, an Air Force statement issued Tuesday said.
The incident occurred at 4:20 p.m. Saturday after the pilot had completed a practice landing approach over the runway. The pilot had begun a second approach and put on the jet engine afterburners, which threw the airplane into "severe pitch oscillations," the statement said.
Pitch oscillations refer to an aircraft that quickly pitches up and down in an uncontrolled manner, a former senior officer at Edwards said. They can be caused either by an electronic malfunction of the flight control system or by a pilot who overcompensates for a pitch change and makes a series of overreactions, the expert said.
The YF-22 that crashed Saturday was flown by Lockheed pilot Tom Morgenfeld, who has significant experience in the aircraft and who escaped with minor injuries. The aeronautics expert discounted the likelihood that a pilot experienced in an aircraft would induce pitch oscillation.
The more likely cause of the incident would be an electronic or computer software malfunction in the aircraft's flight control system, a potentially serious problem that could affect the program, the expert said.
A videotape of the crash released by the Air Force showed that a jet engine nozzle, which can direct the thrust up and down, pitched up and down erratically during the incident. The vectoring, or thrust-directing, system can operate automatically or by pilot control. It wasn't known which mode Morgenfeld had selected Saturday.
The former Edwards officer noted that the JAS-39 Grippen, a Swedish fighter program, experienced pitch oscillations that forced redesign of the flight control system and resulted in a lengthy delay.