ASN Wikibase Occurrence # 129
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| Date: | Wednesday 26 December 2007 |
| Time: | 10:00 LT |
| Type: |  Piper PA-46-310P Malibu |
| Owner/operator: | Bretton International Ltd |
| Registration: | N47BC |
| MSN: | 4608129 |
| Year of manufacture: | 1988 |
| Total airframe hrs: | 3638 hours |
| Engine model: | Teledyne Continental TSIO-550-C |
| Fatalities: | Fatalities: 0 / Occupants: 4 |
| Aircraft damage: | Minor |
| Category: | Serious incident |
| Location: | 12.5 miles E of Aspen/Pitkin County Airport (ASE), Aspen, CO -
 United States of America
|
| Phase: | |
| Nature: | Private |
| Departure airport: | Aspen-Pitkin County Airport, CO (ASE/KASE) |
| Denver International Airport, CO (DEN/KDEN) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
During initial climb at 16,000 feet, the pilot noticed oil droplets forming on his windscreen. On seeing the oil, he contacted air traffic control, declared an emergency, and began a standard rate, 180-degree turn, back to the airport. As he completed the turn, he heard a "boom," felt a shutter, and then the windscreen was covered with oil. The pilot said he may have noted a pitch up with the bang, but he immediately got on the best glide speed, 90 knots, and began retracing his ground track via the global positioning system (GPS) back to the airport. The airplane landed uneventfully back to the airport. An examination of the airplane showed minor damage to the front of the cowling, and the engine showed the crankshaft fractured aft of the flange. The propeller and spinner, and the forward part of the crankshaft were missing. Several months after the incident, the separated propeller assembly and crankshaft were located. Examination of the engine revealed the crankshaft was fractured through, aft of the propeller flange. The fracture of the crankshaft was caused by a fatigue crack that stemmed from the aft relief radius of the propeller flange. The surface of the aft radius contained no evidence of mechanical damage and the fatigue crack emanated from multiple origins over a wide area, indicating that a great amount of stress was necessary to initiate the fatigue crack. The reason for the crack initiation could not be determined. The fatigue crack origin area was located in the relief radius in line with the axis of the propeller blades, consistent with forward and aft bending stresses imposed by the blades during flight. The location indicates a possibility that the blades were out of balance while rotating or that the crankshaft was somehow damaged in the past. No evidence of fretting was noted between the faces of the crankshaft propeller flange and the alternator pulley. The propeller assembly was attached firmly to the crankshaft.
Probable Cause: The failure of the crankshaft due to fatigue. The fatigue crack initiation was not determined.
Accident investigation:
 |
|
Sources:
NTSB DEN08IA044
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 21-Jan-2008 21:29 | JINX | Added |
| 21-Dec-2016 19:13 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 21-Dec-2016 19:14 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 21-Dec-2016 19:16 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 21-Dec-2016 19:20 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 05-Dec-2017 09:47 | ASN Update Bot | Updated [Cn, Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
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