What happened
The pilot was conducting a training exercise involving an autorotation maneuver initiated from a closed traffic pattern, aiming to touch down on the numbers of Runway 35. The pilot reported that the initial phase of the landing appeared normal, including a standard flare and subsequent power recovery. However, as the helicopter began to nose forward out of the flare position, the pilot heard an unusual noise and felt a distinct percussion coming from the rear of the aircraft. Immediately following this event, the helicopter yawed significantly and impacted the ground with considerable force.
The investigation
A post-accident examination of the wreckage revealed that the main rotor blades had struck the rear section of the aircraft. This impact resulted in the complete severing of the tail boom. No other mechanical failures or pre-existing conditions were noted as contributing factors to the structural failure beyond the impact forces generated during the hard landing.
Findings
The sequence of events indicates that the primary cause of the damage was the hard landing following the unexpected yaw. The pilot's ability to recover power and flare normally suggests that the initial approach was controlled until the moment of touchdown. The sudden percussion and noise were consistent with structural contact between the rotating main rotor system and the tail boom assembly, likely exacerbated by the yaw motion during the final phase of the landing.
Safety message
Pilots practicing autorotations should be aware that improper pitch control or timing during the flare can lead to excessive nose-down attitudes or yaw. Maintaining precise control inputs is critical to ensuring a smooth touchdown and preventing contact between rotating components and the airframe.