On November 14, 2004, an Enstrom 280C (registration N51739) was involved in an aviation accident near Galloo Island, NY. Investigators recorded the probable cause as: A partial loss of engine power for undetermined reasons. A factor was the pilot's improper decision to operate the helicopter outside the height velocity curve. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter conducting aerial photography at low altitude and speed experienced a partial engine power loss. The pilot initiated an autorotation, but the rotor rpm decayed, leading to a hard impact. Post-accident inspections found no anomalies in the engine or clutch.
Accident Sequence
While performing aerial photography operations at an altitude of approximately 80 feet above ground level and an estimated groundspeed of 20 knots, the helicopter's engine suffered a partial loss of power. The pilot immediately executed the emergency checklist and configured the aircraft for an autorotation. During the descent, the pilot reported that the rotor and engine would not disengage, and rotor rpm continued to decrease. The helicopter subsequently struck the ground with considerable force, resulting in damage to one main rotor blade and the tail boom.
Post-Accident Examination
Following the accident, the engine was ground-tested at idle power and operated normally. A teardown and inspection of both the engine and clutch assembly revealed no mechanical anomalies or pre-existing faults.
Operational Considerations
A review of the helicopter's height-velocity diagram indicated that, under the conditions present at the time of the incident, the aircraft was operating outside the recommended safe operating envelope.