What happened
The aircraft was engaged in agricultural operations, specifically preparing for chemical dispersal. The helicopter was heavily loaded with chemicals situated on a truck-mounted platform positioned ten feet above ground level. During the initial phase of flight, the pilot attempted to lift off from this position.
Upon liftoff, the engine experienced a significant mechanical failure characterized by a partial reduction in available power. This loss of thrust occurred simultaneously with the aircraft's transition from a hover or low-speed climb. The pilot was unable to maintain altitude due to the insufficient power output relative to the heavy load and the critical phase of flight.
As the helicopter began to descend uncontrollably, it impacted the terrain. The accident sequence concluded when the aircraft struck the ground. The descent occurred at an altitude that proved insufficient to execute a successful autorotational forced landing, leaving no opportunity for the pilot to mitigate the impact or save the occupants.
The investigation
Examination of the helicopter's engine revealed the mechanical root cause of the power loss. Investigators identified two intake valves that were sticking within their housings. This mechanical fault prevented the valves from operating correctly, leading directly to the partial reduction in engine power observed during the critical moments of liftoff.
Findings
The primary factors contributing to this accident include:
- Sticking intake valves which caused a partial power reduction in the engine during the critical phase of takeoff.
- Insufficient altitude at the time of failure, which prevented the pilot from performing an autorotational forced landing.
- The heavy load of agricultural chemicals on the truck-mounted platform, which likely contributed to the power requirements needed for liftoff.
The combination of mechanical failure and inadequate height resulted in a fatal impact with the terrain.