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Summary

Summary

The report presented below was prepared principally from the information supplied to the Bureau.

REPORTED INFORMATION

On 3 March 2005, at about 0700 Western Standard Time, the crew of a Fokker BV F27 Mark 50 (F50) aircraft, registered VH-FNB, was being operated on a scheduled passenger service from Perth to Esperance, WA with four crew and 31 passengers. About 1 minute after takeoff the right engine failed. The crew reported that the failure was accompanied by a triple chime alert, and the illumination of the right engine-out light on the flight-deck centre main instrument panel. At the same time they observed that the right engine torque had exceeded 120%. The crew carried out engine failure procedures, broadcast a PAN,1 and returned the aircraft to Perth.

The aircraft was fitted with propeller auto feathering systems designed to automatically feather a propeller during takeoff when engine torque falls below 25%. An electronic inhibit prevented the propeller on the other engine from moving to feather when one propeller was feathered. The light in the right engine fuel shutoff lever remained illuminated after the flight, indicating that the auto feathering system was still armed. Maintenance engineers completed fault isolation action and replaced the right engine auto feathering control unit (AFCU).

Fokker Service Bulletin (SB) F50-61-011 and Pratt and Whitney SB No. 2104613 were incorporated in 1992. Both SBs required all AFCUs from certain serial numbered aircraft, including VH-FNB, to be replaced with a modified unit to prevent a torque sensor failure initiating an inadvertent auto feather incident during takeoff. The SB action on VH-FNB was completed on 12 November 1992. There have been no reports of a faulty AFCU causing propeller auto feathering during take-off in Australia prior to this occurrence.

The manufacturer of the AFCU examined the removed unit. The manufacturer's report indicated that internal circuit board failures within the AFCU could initiate an auto-feather in flight. The damage within the unit suggests that the unit sustained a power spike or lightening strike. However, the operator had no record of such an event. There was no defect within the AFCU that would cause an indication of a torque sensor failure. The manufacturer recommended that the AFCU be scrapped given its use on an aircraft involved in regular public transport operations. The operator has subsequently scrapped the unit.


  1. Radio broadcast indicating uncertainty or alert.
 
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