ASN Wikibase Occurrence # 31047
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| Date: | Friday 29 August 1997 |
| Time: | 12:15 LT |
| Type: |  Bell UH-1B |
| Owner/operator: | Grizzly Mountain Aviation |
| Registration: | N22753 |
| MSN: | 64-13985 |
| Year of manufacture: | 1964 |
| Total airframe hrs: | 5875 hours |
| Engine model: | Lycoming T53-L-13B |
| Fatalities: | Fatalities: 0 / Occupants: 3 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Dayville, Oregon -
 United States of America
|
| Phase: | En route |
| Nature: | Ferry/positioning |
| Departure airport: | Prairie City, OR |
| Prineville, OR | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
While cruising at 2,000 feet above ground level and 100 knots, the helicopter's right transmission door separated from the aircraft, striking the tail rotor and 90-degree gearbox and knocking them off the aircraft. The pilot entered an autorotative descent to a forced landing in a field, but was unable to raise the collective for touchdown without inducing undesirable yaw. The aircraft landed hard in the forced landing. An FAA inspector found that the two rear cowl latch blocks (which attach the aft end of the separated door to the engine firewall) were missing and did not appear to have been installed, and that the cowl top latch was also unlocked. This enabled the door to lift enough to slide aft out of the front latches and separate from the aircraft. The FAA inspector subsequently found that the company mechanic who removed the latch blocks had not entered the work in the helicopter maintenance records, and that another company mechanic who reinstalled the cowls did not notice the blocks were missing and also improperly locked the top latch.
Probable Cause: Improper installation of the transmission door by a company mechanic, resulting in inflight separation of the door (which then struck the tail rotor system) and consequent total loss of the tail rotor. Contributing to the accident were: inadequate recordkeeping by a company mechanic, and attainment of proper descent rate for the forced landing touchdown was not possible.
Accident investigation:
 |
|
Sources:
NTSB SEA97LA198
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 27-Sep-2008 01:00 | ASN archive | Added |
| 31-Oct-2011 12:29 | Dr. John Smith | Updated [Time, Total fatalities, Total occupants, Other fatalities, Location, Country, Phase, Nature, Departure airport, Destination airport, Source, Damage, Narrative] |
| 08-Apr-2024 13:07 | ASN Update Bot | Updated [Time, Cn, Total occupants, Other fatalities, Nature, Departure airport, Destination airport, Source, Damage, Narrative, Category, Accident report] |
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