Some US Marine Corps and US Air Force Bell Boeing V-22 Osprey tilt-rotors were returned to flight last week after being grounded when a flight-control computer fault was found during factory testing. While a fix is developed, flight-control computers with an earlier microchip have been pooled and installed in 16 USMC MV-22s and three USAF CV-22s to allowing testing and training to continue.
The fault in a chip that ensures redundancy in the V-22’s triplex digital fly-by-wire system, by detecting and isolating a failed flight-control computer, was discovered during start-up testing of a V-22 on Bell’s Amarillo, Texas assembly line. Analysis found the Texas Instruments chip reacts poorly in cold temperatures.
The commercial chip has been used by flight-control computer supplier BAE Systems since 2003, and was believed to be functionally identical to the chip previously used, which came from a different manufacturer. “We are still looking into how a chip that was not suitable for this application came to be incorporated,” says the Navy.
Thirty-five Ospreys - 30 MV-22s and five CV-22s – remain grounded until a “minor modification” to the flight-control computer is qualified. “We will leave the chip on the [circuit] board and make minor changes to the board,” says the navy. Flight tests were planned for late last week, with flight clearance expected by the end of February.
n US Air Force Lockheed Martin F-22A Raptors were scheduled to fly from Hawaii to Japan last weekend after a software fix to cure a navigation system anomaly that forced the aircraft to abandon their 11 February first attempt to cross the Pacific. The 12 F-22s were en route to Kadena AB on Okinawa for the Raptor’s first overseas deployment when the problem forced them to turn back to Hickam AFB in Hawaii.
Source: FlightGlobal.com
