ASN Wikibase Occurrence # 386249
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| Date: | Saturday 3 February 2001 |
| Time: | 12:30 LT |
| Type: |  Enstrom F28A |
| Owner/operator: | Private |
| Registration: | N98PM |
| MSN: | 200 |
| Year of manufacture: | 1974 |
| Total airframe hrs: | 1732 hours |
| Engine model: | Lycoming HIO-360-C1A |
| Fatalities: | Fatalities: 0 / Occupants: 3 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Napoleon, OH -
 United States of America
|
| Phase: | Approach |
| Nature: | Unknown |
| Departure airport: | Napolean, OH (7W5) |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The helicopter developed a vibration, and the pilot elected to return to the departure airport. On final approach to landing, approximately 10 feet above the ground, the main rotor mast fractured, and the main rotor system departed the helicopter. The pilot and two passengers were not injured. Examination of the fracture surfaces by a Safety Board metallurgist revealed the mast failed in fatigue in the area of the fillet radius. Microscopic examination revealed that a portion of the fatigue region had been painted over with paint that matched the exterior of the mast. The mast installed in the accident helicopter had a narrower fillet radius than masts subsequently produced by the manufacturer. An FAA Airworthiness Directive (AD) that required inspecting and strengthening of the fillet radius affected the narrower masts. As a result of this investigation, the FAA amended the AD to immediately retire some transmission/mast combinations, and to ultimately remove all of the narrower masts from service.
Probable Cause: The fatigue failure in the fillet radius of the mast, which resulted in the separation of the main rotor system.
Accident investigation:
 |
|
Sources:
NTSB IAD01LA031
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 05-Apr-2024 12:51 | ASN Update Bot | Added |
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