ASN Wikibase Occurrence # 351091
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| Date: | Sunday 24 May 1998 |
| Time: | 13:35 LT |
| Type: |  Bell 206L-3 |
| Owner/operator: | Air Evac Ems, Inc. |
| Registration: | N27AE |
| MSN: | 51141 |
| Total airframe hrs: | 3247 hours |
| Engine model: | Allison 250-C30P |
| Fatalities: | Fatalities: 0 / Occupants: 3 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Springdale, AR -
 United States of America
|
| Phase: | Initial climb |
| Nature: | Ferry/positioning |
| Departure airport: | |
| Bella Vista, AR | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
Shortly after the helicopter lifted off from a hospital helipad en route to pick up a patient, the engine lost power. The helicopter descended into a parking lot, landed hard, and rolled over coming to rest on its right side. Disassembly of the engine revealed that both the N1 (gas producer turbine) and the N2 (power turbine) shafts had separated. Coke deposits and rub marks were noted on the outside diameter of the N1 shaft. Coke deposits were also present on the inside diameter of the N2 shaft. Metallurgical examination of the shafts determined that coke build up consistent with reduced oil flow led to rubbing between the shafts. The rubbing produced frictional heat that resulted in softening and subsequent failure of the shafts. An o-ring was found lodged in the main oil passage of the accessory gearbox housing. Oil flow testing and calculations showed that this o-ring reduced the oil flow to the turbine shafting from .82 to between .00 and .10 lbs/min. Maintenance records indicated that the engine had accumulated 531 hours since a 3,500 hour gear train inspection, which included disassembly, cleaning, and reassembly of all accessory gearbox components.
Probable Cause: The failure of maintenance personnel to properly assemble the engine's accessory gearbox, which resulted in a total loss of engine power due to partial blockage of the main oil passage by an o-ring. The blockage reduced oil flow to the turbine shafting, which led to the total failure of the gas producer turbine shaft and the power (free) turbine shaft. A factor was the lack of suitable terrain for the forced landing.
Accident investigation:
 |
|
Sources:
NTSB FTW98FA239
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 21-Jan-2024 19:54 | FlyingWolverine | Added |
| 07-Apr-2024 12:02 | ASN Update Bot | Updated [Time, Operator, Total occupants, Other fatalities, Departure airport, Source, Narrative, Category, Accident report] |
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