Bell OH-58C N911PT accident near Riverdale, California

Probable cause

A flight control malfunction while maneuvering for reasons that could not be determined because it was not possible to establish whether observed damage to the flight control assembly was the result of wreckage recovery efforts or a preexisting condition.

NTSB analysis

The pilot was conducting agricultural spray operations when he experienced a flight control system anomaly that was described as a right rolling tendency. The pilot increased altitude in an effort to return to the operator's base for repairs. The helicopter became progressively difficult to control, continuing to roll right and not fully responding to left cyclic control inputs, and the pilot maneuvered to a nearby company loader to land. However, the right rolling tendency continued and the helicopter subsequently collided with terrain.

Postaccident examination of the flight control assembly revealed that the gas producer throttle control cable, which is routed adjacent to the connecting linkage push-pull tubes, was entwined with the push-pull tubes. A section of the cable appeared to be pinched between the lower mixing lever unit and the tunnel partition wall. Multiple nylon loop cable clamps, used to secure the throttle cable to the vertical tunnel partition, were broken and separated; however, it was not possible to determine whether the observed damage was the result of the wreckage recovery efforts or a preexisting condition.

Text from the NTSB. Open the NTSB docket for WPR13LA087 for the full record.