Salzinger_FOO
9th Jun 2005, 00:03
F/A-22 accident report released
LANGLEY AIR FORCE BASE, Va. (ACCNS) - A flight control system problem caused an F/A-22 Raptor to crash on the runway at Nellis Air Force Base, Nev., Dec. 20, according to an Air Force report released today.
The pilot ejected and sustained minor injuries. The $133.3 million aircraft, assigned to Nellis AFB's 422nd Test and Evaluation Squadron, was destroyed on impact. Additional damage was limited to an arresting cable, runway guide sign, runway light, and the runway itself.
The flight control system malfunction was caused by a brief power interruption to the aircraft's three Rate Sensor Assemblies, which caused them to fail. The RSAs measure angular acceleration in all three axes: pitch, roll and yaw. With three failed RSAs, the F/A-22 is unflyable. When the pilot shut down engines for maintenance servicing, he left the auxiliary power unit running. Based on technical order guidance, he believed the power unit would supply continuous power to the flight control system. However, there was a less-than-one second
power interruption to the RSAs during engine shutdown. There is no automatic warning of this condition. To discover it, the pilot would have to have performed a diagnostic test called an "Initiate Built in Test". The pilot accomplished a successful IBIT prior to engine shutdown, and because the power unit was on, he believed a second IBIT was unnecessary.
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Cheers
Salz
LANGLEY AIR FORCE BASE, Va. (ACCNS) - A flight control system problem caused an F/A-22 Raptor to crash on the runway at Nellis Air Force Base, Nev., Dec. 20, according to an Air Force report released today.
The pilot ejected and sustained minor injuries. The $133.3 million aircraft, assigned to Nellis AFB's 422nd Test and Evaluation Squadron, was destroyed on impact. Additional damage was limited to an arresting cable, runway guide sign, runway light, and the runway itself.
The flight control system malfunction was caused by a brief power interruption to the aircraft's three Rate Sensor Assemblies, which caused them to fail. The RSAs measure angular acceleration in all three axes: pitch, roll and yaw. With three failed RSAs, the F/A-22 is unflyable. When the pilot shut down engines for maintenance servicing, he left the auxiliary power unit running. Based on technical order guidance, he believed the power unit would supply continuous power to the flight control system. However, there was a less-than-one second
power interruption to the RSAs during engine shutdown. There is no automatic warning of this condition. To discover it, the pilot would have to have performed a diagnostic test called an "Initiate Built in Test". The pilot accomplished a successful IBIT prior to engine shutdown, and because the power unit was on, he believed a second IBIT was unnecessary.
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Cheers
Salz