Pilot error caused the 14 October 2004 fatal crash of a Pinnacle Airlines Bombardier CRJ200, the US National Transportation Safety Board (NTSB) concluded yesterday.
Contributing to the cause of the accident is engine core lock, which prevented at least one engine from being restarted when the regional jet suffered an aerodynamic stall at 41,000ft (12,500m) - the aircraft’s certified ceiling - and the engines flamed out.
Additionally, the aircraft’s flight manuals did not communicate to pilots the importance of maintaining a minimum airspeed to keep the engine cores rotating, says the regulator in its final report on the accident.
Operated by Northwest Airlink affiliate Pinnacle, the General Electric CF34-3-powered CRJ200 was on a repositioning flight to Northwest Airlines’ Minneapolis/St Paul hub from Little Rock, Arkansas when it crashed in Jefferson City, Missouri, killing the two pilots on board.
Flight data recorder (FDR) information revealed the accident aircraft suffered an aerodynamic stall at 41,000ft and flame out in both engines.
A transcript of cockpit voice recorder data from the crash gave possible insight into why the crew decided to climb to the regional jet’s 41,000ft operational ceiling. When the controller remarked: “I have never seen you guys up at 41 there,” one of the crew responded: “Yeah, we don’t have any passengers on board so we decided to have a little fun up here.”
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”.
Also, the NTSB says “the pilots’ failure to prepare for an emergency landing in a timely manner, including communicating with air traffic controllers immediately after the emergency about the loss of both engines and the availability of landing sites; and the pilots’ failure to achieve and maintain the target airspeed in the double engine failure checklist, which caused the engine cores to stop rotating and resulted in the core lock engine condition”.
“This accident was caused by the pilots’ inappropriate and unprofessional behavior,” says NTSB chairman Mark Rosenker.
“Simply adhering to standard operating procedures and correctly implementing emergency procedures would have gone a long way to averting this tragic accident.”
From this accident report, the NTSB has issued 11 recommendations to the US FAA on pilot training and high altitude stall recovery techniques. These include determining whether requested changes to be made to the high altitude training syllabuses for regional jet aircraft, would also enhance the high altitude training syllabuses for all other transport-category jet aircraft. Rules mandating high altitude recovery techniques should also be put in place, the recommendations continue.
The regulator also recently recommended the FAA implement several new procedures and tests for CRJ and Bombardier Challenger aircraft equipped with GE CF34-1 and CF34-3 engines - and potentially other engine models, pending review - after citing engine core lock as a likely factor in the Pinnacle crash. Core lock is caused by differential cooling of static engine parts and the rotating core.
“Despite their four auxiliary power unit-assisted engine restart attempts, the pilots were unable to restart the engines because their cores had locked. Without core rotation, recovery from the double engine failure was not possible,” the NTSB says.
However, it adds: “Both engines experienced core lock because of the flameout from high power and high altitude, which resulted from the pilot-induced extreme conditions to which the engines were exposed, and the pilots’ failure to achieve and maintain the target airspeed of 240 knots, which caused the engine cores to stop rotating; both of these factors were causal to this accident.”
These recommendations, if adopted by the FAA, will affect over 1,000 CRJs (models -100, -200 and -440) as well as 550 Challenger 601 and 604 corporate jets.
Commenting on today’s report, GE notes that when properly operated, its CF34 engines “are completely safe and have compiled an outstanding safety record with more than 27 million flight hours”.
“Tragically, the pilots in the Pinnacle accident put the engines into a hazardous condition for which they are not designed or tested. CF34 engines are completely safe when operated appropriately,” says GE.
In regard to the NTSB’s recommendations concerning core lock, the engine manufacturer says: “Core lock is a known industry phenomenon and can occur with any engine if operated outside of recommended flight procedures.
“The flight manual provided to pilots of CF34-powered CRJ aircraft has always contained all operating instructions necessary to successfully operate and re-start the engines.”