What happened
On July 14, 2011, at approximately 18:15 local time, a privately owned Robinson R22 Beta, registration JA007J, was involved in a roll-over accident at the Sabaekoizumi temporary helipad in Sabae City, Fukui Prefecture. The aircraft was conducting a familiarization flight with the pilot in command and one passenger on board.
During the final approach, the pilot utilized a steeper descent angle to clear electrical wires located south of the helipad. While the approach was initially stable, the pilot encountered turbulence and instability while attempting to hover. Upon touchdown, the aircraft''s left skid made contact with the ground, but the aircraft immediately began to drift to the right. This movement triggered a rapid right-hand spin. The aircraft subsequently became airborne again, rolled over, and came to rest on its left side on the south slope of the helipad. The impact resulted in major injuries to the pilot and minor injuries to the passenger. The aircraft sustained substantial damage, including a deformed main rotor mast, fractured tail rotor, and broken canopy.
The investigation
Investigators from the Japan Transport Safety Board (JTSB) examined the aircraft's flight history, meteorological conditions, and the pilot's recent training records. The investigation focused on the sequence of control inputs during the unstable touchdown and the impact of local wind conditions. The team also reviewed the functionality of the helipad's windsock, which was found to be too stiff to provide accurate wind velocity readings. Additionally, the pilot's recent flight experience was scrutinized, specifically noting a significant gap in recent takeoff and landing maneuvers.
Findings
- The accident was precipitated by the pilot's unintentional increase in collective pitch and inadequate left pedal input during the touchdown phase, which induced a right-hand spin.
- The aircraft's drift to the right was likely caused by an unintentional right cyclic control movement, potentially triggered by the weathercock effect from shifting crosswinds.
- The pilot's insufficient skill maintenance was a contributing factor, as recent flight logs showed a lack of recent takeoff and landing experience.
- Local wind conditions, characterized by north-northeast winds with gusts up to 15 knots, likely created turbulence near the helipad's vertical edge.
- The windsock at the site was in poor condition, preventing the pilot from accurately assessing the wind state before approach.