Casualties unknown

1989-11-04: Bell UH-1E (N138US) — Gilman D. Christopher — Mesa, AZ

Mesa, AZ, US

On November 4, 1989, a Bell UH-1E (registration N138US) operated by Gilman D. Christopher was involved in an aviation accident near Mesa, AZ. Investigators recorded the probable cause as: THE INFLIGHT SEPARATION OF THE TAIL ROTOR DUE TO IMPROPER MAINTENANCE PROCEDURES AND THE INSTALLATION OF INCORRECT ATTACHMENT HARDWARE ON THE TAIL ROTOR BLADE PITCH CHANGE LINKAGES. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 1781061362Data APIEditorial standards

An investigation into a tail rotor separation in flight revealed missing hardware on one blade and incorrect hardware on another, with worn bushings and excessive washers; these discrepancies should have been detected during preflight inspection.

Investigation Findings

The investigation determined that the tail rotor separated from the helicopter while in flight. The tail rotor assembly was subsequently sent to the manufacturer for detailed analysis.

Hardware Discrepancies

On tail rotor blade 'A', the bolt, nut, and associated hardware that attached the pitch change link to the blade grip were missing. Additionally, the bolt bushing was worn beyond the service limits, mandating its replacement. On blade 'B', the attaching bolt, nut, and hardware were found to be the wrong size. Furthermore, the wrong spacer was attached to the bolt, and four more washers than allowed were installed under the trailing edge blade retaining bolt nut.

Inspection Requirements

According to the preflight inspection requirements, the discrepancies on blade 'A' (the worn bushing) and the incorrect hardware on blade 'B' (the pitch change link) should have been detected during the daily inspection event.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001213X29808. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.