What happened
On December 18, 2023, a Robinson R44, registration JA01CG, was participating in a hover training session at the JPD Kyoto Operation Site in Kyoto City. The flight was being conducted by a flight instructor accompanied by a student pilot on their very first flight. The training session, operated by Takumi Enterprise Helicopter & Airplane Co., Ltd., involved practicing vertical take-offs, landings, and hovering at a low altitude.
During the session, the instructor allowed the trainee to take control of the aircraft while maintaining a hand on the flight controls. As the helicopter was hovering, it began to drift backward. When the instructor alerted the trainee to this movement, the trainee attempted to correct the position with a sudden and excessive forward input. This abrupt maneuver caused the aircraft to transition rapidly from a rearward drift to a high-speed forward movement toward the boundary of the training area.
In an attempt to stabilize the aircraft, the instructor took over the controls and applied a nose-up input. This action caused the tail rotor blades to strike the ground, resulting in a loud impact, a sudden rightward yaw, and significant airframe oscillation. The instructor managed to bring the aircraft down for a landing on the asphalt surface, but the impact was hard, causing the helicopter to strike the ground on the forward part of the skids. The aircraft was destroyed in the process, though no injuries were reported for the crew.
The investigation
An investigation by the JTSB examined the flight history, the training status of both the instructor and the trainee, and the physical condition of the wreckage. Investigators analyzed the flight control inputs, the weather conditions (which were fine with a light 5-knot northwest wind), and the training syllabus provided by the operator. The investigation also looked into the instructor's recent certification and the trainee's lack of prior flight experience.
Findings
- The trainee, being on their first flight, lacked the skill to maintain a stable hover and was likely reacting to the pressure of the situation.
- The trainee's response to the instructor's warning was an excessive and disproportionate control input that exceeded the instructor's ability to compensate.
- The instructor's attempt to regain control via a nose-up input directly led to the tail rotor making contact with the ground.
- The instructor had added additional hover training to the session that was not part of the original, pre-planned lesson plan, which may have increased the psychological workload on the student.
- The instructor, while recently certified, was conducting training for a student with no prior experience, and the company had deemed their experience sufficient for such a task.