NTSB Identification: DEN00IA080.
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Scheduled 14 CFR AIR BC, LTD.
Incident occurred Sunday, April 30, 2000 in DENVER, CO
Probable Cause Approval Date: 07/10/2001
Aircraft: British Aerospace BAE 146-200, registration: CFBAO
Injuries: 20 Uninjured.
NTSB investigators used data provided by various sources and may have traveled in support of this investigation to prepare this aircraft incident report.
Power on the no. 1 engine 'rolled back' (dropped to flight idle) while the airplane was in IMC at FL 290. The operator reported considerable convective cloud and thunderstorm activity in the area, with cloud tops reaching FL500. When the flight descended to FL 260, power on nos. 2 and 4 engines also rolled back. As the airplane passed 12,500 feet msl, power returned to the three idling engines. The flight landed without further incident. The airplane was equipped with four unmodified Honeywell ALF502R engines. In certain temperature and moisture conditions, the engines become susceptible to ice accumulation on the supercharger exit guide vanes. This reduces core engine airflow, resulting in a loss of power. Early airworthiness directives prohibited flight in icing conditions above 26,000 feet and at an outside air temperature above -40 degrees C. SAT within 30 nm of thunderstorms. Some operators were granted waivers from these ADs. Recent airworthiness directives mandate certain engine modifications be made by December 2002. Newer models of the airplane feature redesigned engines.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The accumulation of ice on the supercharger exit guide vanes that reduced core engine airflow, resulting in a loss of power. Factors were the clouds and icing conditions. Full narrative available
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