Deliberate pilot deviation from proper procedures caused the 14 October 2004 fatal crash of a Pinnacle Airlines Bombardier CRJ200, says the US National Transportation Safety Board final report. The aircraft stalled at its 41,000ft (12,500m) absolute ceiling, causing the engines to flame out, then engine "core lock" prevented re-ignition. The NTSB cites core lock in the General Electric CF34-3 turbofans as a contributory cause.
GE says: "The NTSB's 'contributing cause' and earlier-released recommendations reference engine restart. GE supports these recommendations, which focus on operational and training procedures to enhance aircraft safetythe pilots in the Pinnacle accident put the engines into a hazardous condition for which they are not designed or tested."
The NTSB also observes the aircraft's flight manuals did not make clear the importance of maintaining a minimum airspeed to keep the engine cores rotating. Core lock is caused by differential cooling of static engine parts and the rotating core. The NTSB says: "Both engines experienced core lock because of the flameout from high power and high altitude, which resulted from the pilot-induced extreme conditionsand the pilots' failure to achieve and maintain the target airspeed of 240kt (445km/h)Despite their four auxiliary power unit-assisted engine restart attempts, the pilots were unable to restart the engines because their cores had locked."
The CRJ200, operated by Pinnacle for Northwest Airlink, was on a positioning flight to Minneapolis/St Paul from Little Rock, Arkansas when it crashed in Jefferson City, Missouri, killing the two pilots who were the sole occupants. The cockpit voice recorder reveals that when an air traffic controller remarked: "I have never seen you guys up at 41 there," one of the pilots responded: "Yeah, we don't have any passengers on board so we decided to have a little fun up here." The flight data recorder shows the aircraft stalled at 41,000ft and both engines flamed out. The NTSB says the probable cause of the accident "was the pilots' unprofessional behaviour, deviation from standard operating procedures, and poor airmanship, which resulted in an in-flight emergency from which they were unable to recover, in part because of the pilots' inadequate training".
The NTSB has recommended that the FAA should review the requirement for crew training in stall recovery, response to stickshaker actuation, and handling aircraft at very high altitude.