What happened
The helicopter was operating at an altitude of 200-300 feet above ground level (AGL) over terrain with an elevation of approximately 8,000 feet. The aircraft was maintaining a speed of 80 knots when the pilot reported encountering significant wind gusts. These gusts caused the ground speed to decrease rapidly, eventually slowing to zero.
Following this loss of forward momentum, the aircraft began a rapid vertical descent while still indicating an airspeed of 80 knots on the instruments. The pilot attempted to arrest this descent but was unable to prevent impact with the ground. Upon impact, the right skid collapsed. The force of the collision caused the helicopter to roll to the right, resulting in the shearing of the main rotor (M/R) blades and twisting off the tail boom.
The investigation
The investigation focused on the mechanical condition of the aircraft following the accident. Examination revealed that the right skid collapsed upon impact with the terrain. The main rotor blades were found to be sheared, and the tail boom was twisted off its normal position. These damages are consistent with a high-energy vertical descent followed by an uncontrolled impact.
Findings
Contributing factors identified in the report include:
- Wind gusts that reduced ground speed to zero, leading to a loss of lift and control authority.
- The aircraft's rapid vertical descent while still indicating forward airspeed.
- Inability to arrest the descent prior to impact.
The sequence of events indicates that the combination of terrain elevation, low altitude, and sudden wind conditions led to a critical loss of flight performance. The pilot's efforts to recover were insufficient to prevent the accident given the rate of descent and environmental factors.