Incident Overview
A helicopter involved in an aerial application flight experienced a power loss during liftoff after returning to its helipad for refueling and reloading. The helipad consisted of a flat bed trailer attached to a truck. According to the pilot, the engine lost power as the helicopter lifted off from the trailer, causing the helicopter to settle downward. Consequently, the main rotor blades struck the cab of the truck.
Post-Incident Examination
An examination of the helicopter revealed that the engine-to-transmission drive shaft flex coupling had failed. Both components of the flex coupling exhibited corrosion, which likely contributed to the failure. The incident occurred after the helicopter had completed a two-hour aerial application flight and had been refueled and loaded with additional chemicals.
Investigative Findings
The investigation focused on the mechanical failure of the flex coupling. The presence of corrosion on both coupling components was documented. No other contributing factors were identified, and the pilot reported no prior indications of mechanical issues during the flight. The helicopter remained on the trailer after the rotor strike, with the truck cab sustaining damage from the rotor blades.