As the result of what some aviators have called hot-dogging by a Pinnacle Airlines (PNCL) crew on a positioning flight, the National Transportation Safety Board urged the Federal Aviation Administration to require new standards for the CF34-1 or CF34-3 engines, citing a safety hazard that could prevent them from being restarted if they fail at high altitude. In addition, the Board is concerned that the same problem could impact other engine models and is planning to review them to ensure they do not have the same problem.

In the October 2004 accident, the engines essentially locked up, preventing them from being restarted because they could not spin fast enough. A cause has yet to be determined. The crew took the aircraft to the airplane's maximum operating altitude of 41,000 feet at less than its best rate of climb speed and slowed to its stall speed. An aerodynamic stall followed, which resulted in a loss of control of the airplane.

The plane's flight data recorder indicated that the pilots tried several times to restart the engines using the auxiliary power unit on the Bombardier [BBD] CRJ 200 without success. The flight data recorder (FDR) and the cockpit voice recorder (CVR) indicated that the engines were operating normally before the upset. The crew died in the crash. Evidence also shows the crew violated airline rules.

The board recommended FAA require manufacturers to perform high-power, high-altitude sudden engine shutdowns, determine the minimum airspeed required to maintain sufficient core rotation and demonstrate that all methods of in-flight restart can be accomplished when this airspeed is maintained.

The board also wants airplane flight manuals for the engines that power the CRJ-100, -200, and -440, to clearly state the minimum airspeed required for engine core rotation and that, if this airspeed is not maintained after a high-power, high-altitude sudden engine shutdown, a loss of in-flight restart capability as a result of core lock may occur.

More information can be found at http://www.ntsb.gov/Recs/letters/2006/A06_70_76.pdf