NTSB Identification: SEA97LA198.
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Accident occurred Friday, August 29, 1997 in DAYVILLE, OR
Probable Cause Approval Date: 02/02/1998
Aircraft: Garlick UH-1B, registration: N22753
Injuries: 1 Serious,2 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
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.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: 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. Full narrative available
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