What happened
The pilot in command was conducting the final phase of flight during an approach to land. At an altitude of 125 feet above ground level, the pilot detected an audible low RPM warning from the aircraft's systems. In response to this indication, the pilot immediately initiated an autorotation maneuver. This involved lowering the collective control lever to its full down position and moving the throttle to the flight idle setting. The pilot successfully completed the autorotational landing sequence. Upon touchdown, the aircraft's speed was higher than intended. To arrest the forward momentum of the helicopter, the pilot applied aft cyclic pressure.
The investigation
The investigation relied primarily on the pilot's statement regarding the sequence of events. No mechanical examination or physical evidence from the crash site is included in this source text. The pilot confirmed that the low RPM warning was active prior to the initiation of the emergency procedure.
Findings
The primary finding relates to the aircraft's powerplant performance during the final approach phase. The activation of the low RPM audio warning indicated a loss of engine power or rotor drive integrity. The pilot's decision to enter autorotation was consistent with standard emergency procedures for this type of aircraft failure. The touchdown speed exceeding normal parameters suggests that the available altitude and airspeed were insufficient to achieve a perfectly controlled flare, necessitating the use of aft cyclic to stop the aircraft.
Safety message
This incident highlights the critical importance of monitoring engine RPM indicators during low-altitude operations. Pilots must be prepared to execute autorotations immediately upon receiving low RPM warnings, even at very low altitudes where recovery options are limited.