On July 1, 1996, a Hiller UH12 (registration N14637) was involved in an aviation accident near Franklin, LA. Investigators recorded the probable cause as: loss of engine power for undetermined reasons, and the pilot's failure to maintain rotor RPM. A factor was the unsuitable terrain available for the precautionary landing. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter experienced an engine malfunction at about 100 feet, leading to a precautionary landing where rotor RPM decayed. During touchdown, structural damage occurred including severance of the tailboom, tailrotor gearbox, and vertical stabilizer.
Incident Overview
A pilot reported hearing a 'bang' followed by the engine running rough while the helicopter was operating at an altitude of about 100 feet above ground level (AGL). The pilot elected to perform a precautionary landing to investigate the source of the engine problems.
Loss of Rotor RPM and Landing
During the approach for the precautionary landing, the pilot stated that the rotor RPM started to bleed and sufficient RPM could not be maintained for a successful landing. The helicopter touched down in a muddy grass area with low rotor RPM.
Damage Details
Upon touchdown, the front cross tube collapsed and the aft skid settled into the mud. Examination of the airframe revealed that the tailboom, tailrotor gearbox, and a portion of the vertical stabilizer were severed from the helicopter as a result of impact with the main rotor blades.
Engine Power Loss
The reason for the partial loss of engine power could not be determined.