What happened
On March 14, 2017, a Eurocopter AS350 B3, registered JA500H, was conducting annual pilot training at Kobe Airport. The flight, operated by HIRATA GAKUEN, involved a pilot in command and a trainee. During the session, the crew performed various maneuvers, including autorotation practice and a simulated hydraulic system failure.
Following a running landing on a grass area within the airport grounds, the crew attempted to lift off again to continue the training. During the transition of control from the trainee in the right seat to the pilot in command in the left seat, the helicopter experienced an unexpected left rotation. As the aircraft attempted to climb, the trailing end of the right skid became embedded in the muddy ground. This created a fulcrum point that triggered a dynamic rollover to the right. While the aircraft was destroyed, there were no injuries to the two occupants, and no fire broke out.
The investigation
The Japan Transport Safety Board (JTSB) examined the flight history, engine data recorder, and the physical condition of the aircraft and landing site. Investigators focused on the sequence of events during the transfer of control and the specific mechanics of the hydraulic system failure simulation. The investigation also reviewed the cockpit procedures used to restore hydraulic pressure and the state of the grass area where the landing occurred.
Findings
- The transfer of control was poorly coordinated; the trainee released the flight controls before the pilot in command had established secure control.
- The pilot in command attempted to restore hydraulic pressure while simultaneously taking control, leading to a lack of attention to the flight controls.
- The collective pitch lever rose unexpectedly because it was not properly secured or held during the transition.
- The ground conditions in the grass area were muddy, which allowed the right skid to catch and initiate the rollover.
- There were inconsistencies in how pilots within the organization understood the emergency operating procedures for hydraulic failure training.