ASN Wikibase Occurrence # 31161
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| Date: | Monday 12 August 1996 |
| Time: | 12:30 LT |
| Type: |  Bell UH-1H |
| Owner/operator: | Reynolds Aviation Inc. |
| Registration: | N97NW |
| MSN: | 65-09823 |
| Year of manufacture: | 1965 |
| Total airframe hrs: | 8763 hours |
| Engine model: | Lycoming T53-L-13B |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | 4 miles north of Fourth of July Pass, ID -
 United States of America
|
| Phase: | Taxi |
| Nature: | Unknown |
| Departure airport: | 4th Of Jul Pass, ID |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The aircraft, originally manufactured by Bell as a military helicopter, had received civil type certification under a different manufacturer. While conducting external load logging operations, the helicopter's vertical fin and tail rotor separated from the tail boom and the helicopter subsequently crashed. Postaccident investigation revealed that the left side of the forward vertical fin spar had a fatigue fracture originating at the first rivet hole above the intersection of the tail boom and the vertical fin. Between March and November 1996, two other similar helicopters (a Bell 205A-1 and a Garlick TH-1L) also crashed during external load operations after their vertical fins separated due to fatigue at the same location on the spar. An existing airworthiness directive (AD) on the Bell 205A-1, AD 71-21-02, contained procedures for checking the fracture area on these aircraft for cracks, but did not apply to any of the aircraft as the 205A-1 which crashed had modifications which exempted it from the AD, and the UH-1H and TH-1L were type-certificated as different make and model aircraft.
Probable Cause: Fatigue fracture of the left forward vertical stabilizer spar, resulting in loss of the vertical stabilizer and tail rotor and subsequent loss of control. A factor was insufficient applicability (by make and model) of an existing FAA airworthiness directive (AD 71-21-02) which mandated repetitive crack inspections in the area of the fracture.
Accident investigation:
 |
|
Sources:
NTSB SEA96FA187
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 27-Sep-2008 01:00 | ASN archive | Added |
| 20-Mar-2011 14:42 | harro | Updated [Time, Total occupants, Location, Country, Phase, Nature, Source, Damage, Narrative] |
| 08-Apr-2024 19:39 | ASN Update Bot | Updated [Time, Cn, Operator, Other fatalities, Phase, Nature, Departure airport, Source, Damage, Narrative, Category, Accident report] |
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