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ASN Wikibase Occurrence # 185036
Last updated: 5 December 2020
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Type:Silhouette image of generic BE36 model; specific model in this crash may look slightly different
Beechcraft A36 Bonanza
Registration: N700TT
C/n / msn: E-2361
Fatalities:Fatalities: 0 / Occupants: 1
Other fatalities:0
Aircraft damage: Substantial
Location:4 miles West of General William J Fox Airport, Lancaster, California -   United States of America
Phase: En route
Departure airport:Fullerton, CA (FUL)
Destination airport:Fresno, CA (FAT)
Investigating agency: NTSB
The airplane collided with power lines during an off-airport forced landing following a loss of engine power. While in cruise at 10,500 feet, the pilot heard a bang, and the engine lost power. He declared an emergency, and attempted to glide to a nearby airport; however, he was unable to make it to the runway. The airplane collided with power lines and fell to the ground about 4 miles west of the airport. The N1 and N2 shafting systems were bound up and would not move. The upper magnetic chip detector was free of metal, but it did contain coke. There was slight varnishing of the anode and cathode. The lower magnetic chip detector contained a substantial amount of metallic particles, subsequently identified as material from the No. 5 bearing. The particles did bridge the gap from anode to cathode. A detailed examination of the engine determined that three sections of the first stage turbine wheel separated. The stub shaft also fractured and separated, and a portion of the fractured tie bolt remained in the wheel. Metallurgical examination of the first and second stage turbine wheels found evidence of gamma prime solutioning and localized melting of the second stage turbine wheel airfoil tips, indicating temperature exposures above 2,100 degrees Farenheit, a temperature range outside the normal operating envelope of these wheels. This exposure to elevated temperatures resulted in rim separation due to thermal fatigue initiating at the rim followed by accelerated interdendritic creep crack growth. No evidence of an oil fire was associated with the first stage wheel separation. The composition, hardness, and microstructure of the first stage turbine wheel were as required by the engineering drawing. The No. 5 bearing exhibited heat distress, but the cause of this could not be conclusively determined. According to Rolls-Royce Allison, the internal evidence of excessive thermal damage to the first and second stage turbine wheels was consistent with prior examples of known hot starts.

Probable Cause: A loss of engine power due to thermal fatigue failure of the first stage turbine wheel resulting in release of a section of its rim. The thermal fatigue was due to the engine exceeding its temperature limits during one or more start cycles.


FAA register: 2. FAA:

Revision history:

01-Mar-2016 00:32 Dr.John Smith Added
01-Mar-2016 00:32 Dr.John Smith Updated [Location]
21-Dec-2016 19:30 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
08-Dec-2017 19:58 ASN Update Bot Updated [Departure airport, Destination airport, Source, Narrative]

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