ASN Wikibase Occurrence # 32230
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| Date: | Monday 18 September 1995 |
| Time: | 12:00 LT |
| Type: |  Bell 204/UH-1L |
| Owner/operator: | Mountain West Helicopters, LLC |
| Registration: | N70410 |
| MSN: | 157855 |
| Year of manufacture: | 1969 |
| Total airframe hrs: | 9475 hours |
| Engine model: | Lycoming T53-L-13B |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Grace, Idaho -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Unknown |
| Departure airport: | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
During log slinging operations the restricted category UH-1L rotorcraft's T53-L-13B military engine experienced a total loss of power. The pilot dropped the log load and autorotated into a small, upsloping, cleared area within the surrounding wooded terrain landing hard. Postcrash examination of the engine revealed that the centrifugal impeller had separated due to fatigue cracking in one of the drain holes. An Airworthiness Directive (AD) had been issued relative to the -08 impeller but did not include the -07 impeller (installed in the accident engine). The -07 and -08 impellers are essentially identical with the exception that the -07 impeller is found on military variants of the engine whereas the -08 is found only on civilian variants. As the -07 impeller was not included in the AD, the operator was not required to conduct the appropriate inspections described in the mandated service bulletin. Additionally, the AD did not require a cycle count for the impeller as addressed in the service bulletin, thus rendering the service bulletin unusable even if it had been mandated for the -07 impeller.
Probable Cause: the fatigue failure of the centrifugal impeller and the lack of suitable terrain for a forced landing. Factors contributing to the accident were: the lack of required compliance with the FAA Airworthiness Directive by the operator, the insufficiently defined FAA procedure within the AD (failure to include the -07 impeller and establish a cycle count program), and inadequate rotor RPM.
Accident investigation:
 |
|
Sources:
NTSB SEA95LA221
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 27-Sep-2008 01:00 | ASN archive | Added |
| 30-Oct-2011 06:38 | Dr. John Smith | Updated [Total fatalities, Total occupants, Other fatalities, Location, Country, Phase, Nature, Source, Damage, Narrative] |
| 09-Apr-2024 11:51 | ASN Update Bot | Updated [Time, Cn, Operator, Other fatalities, Phase, Nature, Source, Narrative, Category, Accident report] |
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