On April 16, 1994, a Hiller UH-12 (registration N41319) operated by Central Helicopter Services was involved in an aviation accident near Alvin, TX. Investigators recorded the probable cause as: Engine power fluctuation during climb leading to loss of rotor RPM and subsequent autorotation. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter experienced engine power fluctuations during climb, leading to a low-altitude autorotation. The pilot landed safely, though the aircraft sustained significant structural damage to the right skid and tail boom.
What happened
During a climb to cruise altitude, the helicopter's engine power began to fluctuate unexpectedly. This instability caused the main rotor revolutions per minute (RPM) to decay to a level that was insufficient to maintain controlled flight. Recognizing the loss of power, the pilot executed an autorotation from a low altitude, aiming for the only available landing area nearby.
During the touchdown phase of this emergency landing, the aircraft sustained significant structural damage. The right skid was damaged upon impact, and the tail boom was severed completely.
The investigation
Following the incident, an FAA airworthiness inspector examined the helicopter's engine and drive train to determine the cause of the power fluctuation. The inspection revealed no discrepancies in the mechanical systems.
Probable cause
Engine power fluctuation during climb leading to loss of rotor RPM and subsequent autorotation.