On April 27, 1991, a Bell 47G4 (registration N1195W) operated by W. J. Tiller was involved in an aviation accident near Corpus Christi, TX. Investigators recorded the probable cause as: The failed lateral servo had been replaced by an unqualified person prior to the flight. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A commercial pilot experienced intermittent binding in the cyclic control while herding cattle. During a precautionary landing flare, the lateral cyclic control locked, causing the helicopter to pitch and strike trees, resulting in its destruction. The failed servo had been replaced by an unqualified person.
Incident
A commercial pilot was maneuvering a helicopter to control a herd of cattle when he noticed an intermittent binding in the left quadrant of the cyclic control. He informed his flight leader of his intention to land and inspect the hydraulic servos in the flight control system, then initiated a precautionary landing near their maintenance support vehicle.
Pilot Actions
During the landing flare, the helicopter pitched sharply to the right rear as the lateral cyclic control became locked. The pilot applied full right pedal in an attempt to cushion the landing and prevent the helicopter from rolling.
Damage
The helicopter was destroyed upon impact with mesquite trees.
Findings
Examination revealed that the failed lateral servo had been replaced by an unqualified person prior to the flight.
Probable cause
The failed lateral servo had been replaced by an unqualified person prior to the flight.
What happened in the 27 Apr 1991 Bell 47G4 accident near Corpus Christi, TX?
A commercial pilot experienced intermittent binding in the cyclic control while herding cattle. During a precautionary landing flare, the lateral cyclic control locked, causing the helicopter to pitch and strike trees, resulting in its destruction. The failed servo had been replaced by an unqualified person.
What aircraft was involved and where did it happen?
The accident on 27 Apr 1991 involved a Bell 47G4, registration N1195W, operated by W. J. Tiller, at Corpus Christi, TX.
What was the probable cause of the accident?
The failed lateral servo had been replaced by an unqualified person prior to the flight.
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