On July 5, 2005, a Bell 47G-2A (registration N38926) was involved in an aviation accident near Oroville, WA. Investigators recorded the probable cause as: A broken throttle cable housing, which permitted the engine's RPM to decay to the idle position. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter's main rotor struck cherry trees during an autorotation following a sudden engine stoppage. Postimpact examination revealed a broken throttle cable housing caused the engine RPM to decay to idle.
Incident Overview
According to the pilot, the helicopter was engaged in spraying operations over a cherry orchard when the engine ceased operation unexpectedly. The pilot initiated an autorotation to manage the descent, but the main rotor blades made contact with cherry trees.
Damage Assessment
The impact shattered the helicopter's main bubble and bent the skids and frame. The extent of damage indicates a forceful collision with the trees.
Postimpact Examination
Following the accident, a Federal Aviation Administration inspector examined the aircraft. The inspection identified that the throttle cable's housing had broken. This failure allowed the engine's RPM to decrease to the idle position, preventing the engine from producing power.
Findings
The examination concluded that the broken throttle cable housing was the mechanical issue that led to the loss of engine power.
Probable cause
A broken throttle cable housing, which permitted the engine's RPM to decay to the idle position.