What happened
On March 13, 2021, a Honda Aircraft Model HA-420, registration JA01HJ, operated by Okayama Air Service Co., Ltd., departed from Kohnan Airport for a training flight. The flight was part of a program to qualify a trainee for captain status. After performing touch-and-go exercises at Takamatsu Airport, the aircraft returned to Kohnan Airport for landing on Runway 27.
Upon touchdown, the aircraft began to drift toward the left side of the runway. The trainee attempted to maintain the centerline using the rudder and brakes. However, during the deceleration process, the aircraft's heading shifted sharply to the right, followed by an abrupt correction to the left. This sequence of maneuvers caused the aircraft to tilt and generated significant lateral acceleration. Ultimately, the aircraft exited the runway at the side stripe marking and came to a stop in a grassy area. The two occupants, a captain and a trainee, were uninjured, though the aircraft sustained minor damage, including scratches to the fuselage and impact marks on the engine air intake and landing gear.
The investigation
The Japan Transport Safety Board (JTSB) examined flight recorder data, cockpit voice recordings, and physical evidence including tire marks on the runway and grassy area. The investigation focused on the aircraft's systems, the meteorological conditions, and the pilot's control inputs. Investigators analyzed the sequence of heading changes and roll angles recorded by the Central Maintenance Function. The investigation also reviewed the training protocols of the operator and the specific actions taken by the crew during the landing roll.
Findings
- The aircraft's mechanical systems, including brakes, rudders, and nose gear steering, were found to be functioning normally.
- The sudden change in the aircraft's direction was likely driven by excessive corrections to the travel direction made by the trainee.
- As the crew applied repeated rudder and braking inputs to correct the drift, the aircraft experienced significant tilting and lateral acceleration.
- These forces caused the tires to skid, which reduced the effectiveness of both the steering and the braking capabilities of the main landing gear.
- The captain, acting as an instructor, was likely focused on evaluating the trainee's performance and did not intervene with necessary advice or take control of the aircraft at an early stage of the deviation.