NTSB Identification: FTW01IA051.
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Scheduled 14 CFR operation of American Eagle Airlines, Inc. (D.B.A. N/A)
Incident occurred Wednesday, January 10, 2001 in San Antonio, TX
Probable Cause Approval Date: 04/01/2003
Aircraft: Saab 340B, registration: N394AE
Injuries: 27 Uninjured.
NTSB investigators used data provided by various sources and may have traveled in support of this investigation to prepare this aircraft incident report.
The flight was in cruise, in icing conditions, when both engines experienced momentary power fluctuations (PF) as a result of ice ingestion. Evaluation of the flight data recorder information revealed that the left engine experienced four Type II (compressor stall) PF events, and the right engine experienced one Type I (partial/full quenching of the engine's combustor flame) PF event and one Type II event. The flight descended, the power fluctuations ceased, and the flight proceeded to land at its intended destination. The Saab 340 fleet has undergone extensive research, with regards to power fluctuations, since it was certified in the U.S. in 1985. In 1985, it was determined that ice accumulates on the engine inlet splitter lip, breaks off, and enters the engine resulting in a flame-out. An auto-ignition system was developed to provide a means to re-light the engine. Aircraft certification rules require that no accumulation of engine inlet ice occur that will adversely affect engine operation. In 2000, the FAA's position was that even though no re-design of the engine inlet was found that would preclude ice accumulation on the splitter lip, the risk associated with a PF event was acceptable. Furthermore, the FAA determined that the risk of a dual engine power loss due to the existence of an icing condition and failure of both engines' auto-ignition systems was acceptably low. Lastly, the FAA stated that inappropriate crew response risks associated with PFs combined with an in-flight shut down were quantitatively indeterminate, but deemed qualitatively acceptable by FAA certification pilots and human factors specialists.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: the ingestion of ice/slush into both engines, which resulted in dual engine power fluctuations. Full narrative available
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