Recorder holds Osprey accident key

Tucson, AZ -Investigators examined flight data recorder information for clues to what caused the crash of a Marine Corps MV-22 Osprey tiltrotor aircraft, killing 19 Marines here on April 8. The nature of the crash would suggest, according to aviation authority Jay Miller (co-author of a book on the aircraft), "a catastrophic mechanical failure or an indication of vulnerability to pilot error at a critical phase of flight."

Smiths Industries Aerospace (Grand Rapids, MI) makes the armored MV-22 Crash Survivable Memory Unit. The device records 227 aircraft parameters on non-volatile memory chips. An RS-422 serial data bus links the vehicle's systems to the recorder.

The aircraft was participating in an exercise determining how it would function and fit in with other aircraft and forces in a simulated rescue of civilians from a hostile environment. A total of 30 aircraft, including four MV-22s, were involved in the mission that took place over multiple Arizona locations about 200 miles apart. The aircraft that crashed was conducting a rolling landing at the time. The pilot had completed the transition from wingborne, airplane flight (engines horizontal) into the fully rotor-supported helicopter mode (engines vertical). One report says the approach appeared normal until, somewhere above 200-ft altitude, the nose yawed to the right and then immediately pitched down, with the impact in a near vertical attitude. Preliminary results point to a very high rate of descent, coupled with a right-wing-down bank, causing loss of lift from the right rotor-the airflow pushed down by the rotor equalled that coming up because of the descent speed and banking.

Two major accidents have occurred with the Osprey before. In 1991, reversed electrical wiring was blamed for a nonfatal crash. An engine fire during transition to conventional flight resulted in seven deaths in 1992. Miller says the accidents were unrelated, "without a line of a traceable history of problems." He adds, "It's a complex aircraft in terms of technology, materials, and propulsion. Everything on it is pacesetting."