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| Date: | Thursday 11 February 1999 |
| Time: | 19:50 LT |
| Type: |  British Aerospace BAe-146-200A |
| Owner/operator: | United Express, opb Air Wisconsin |
| Registration: | N608AW |
| MSN: | E2049 |
| Total airframe hrs: | 24544 hours |
| Engine model: | Lycoming ALF502R-5 |
| Fatalities: | Fatalities: 0 / Occupants: 88 |
| Other fatalities: | 0 |
| Aircraft damage: | Minor, repaired |
| Category: | Serious incident |
| Location: | Near Aspen, CO -
 United States of America
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| 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 |
The airplane experienced an uncontained number 4 engine failure during climb to cruise altitude. Examination of the engine revealed that the number 4 turbine disc had all its blades separated just above the blade platform except 1, which separated just below the blade platform. According to maintenance records, the number 4 turbine disc assembly was installed 22.5 hours or 22 cycles prior to this event. The manufacturer of the turbine disc said that the wheel was new; however, all 60 of the blades had seen previous use. A high-cycle fatigue crack was found in the one blade which had separated below the blade platform. The metallurgist noted that the fatigue crack originated from a fretting damage mark located at the fir-tree portion. The manufacturer reported that 9 blade retention pins, which were used to prevent blade radial movement, did not meet the requirement of no more than 0.005 inch clearance between pen head and wheel. They further reported that blade stress concentration was induced by the wheel broach slots sharp edges.
Probable Cause: The inadequate maintenance overhaul of the number four turbine disc by the manufacturer. A factor was the turbine blade's failure due to high cycle fatigue fracture.
Accident investigation:
 |
|
Sources:
NTSB DEN99IA038
https://www.jetphotos.com/photo/111748 (Photo)
History of this aircraft
Other occurrences involving this aircraft
| 18 January 1991 | N608AW | Air Wisconsin | 0 | Chicago, IL | |
min |
| 26 May 1996 | N608AW | Air Wisconsin | 0 | Des Moines, IA | |
non |
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 13-Sep-2024 16:24 | ASN Update Bot | Added |
| 13-Sep-2024 16:26 | ASN | Updated [Aircraft type, Operator, Location, Nature, Departure airport, Narrative, ] |
| 17-Apr-2025 06:48 | Justanormalperson | Updated [Operator, Location, Destination airport, Source, ] |
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