What happened
On July 20, 2015, at approximately 12:40 JST, a privately owned Cessna 172P, registration JA4005, was attempting a pleasure flight from the Betsukai Flight Park Temporary Airfield in Hokkaido. The aircraft was configured for a short-field take-off from a grass runway, carrying a pilot and three passengers.
During the initial climb, the pilot attempted to manage the aircraft's ascent while seated in the right pilot seat. Shortly after lifting off, the pilot reached for an aeronautical chart stored in the door pocket to verify the flight route. In doing so, the edge of the chart struck the flap lever, inadvertently retracting the flaps from 10° to the full-up position. This sudden change in configuration, combined with insufficient airspeed, caused the aircraft to enter a stall at a very low altitude of approximately 10 meters. The aircraft became unstable, veered left, and crashed into a nearby meadow, triggering a fire in the engine area. The accident resulted in three serious injuries and one minor injury.
The investigation
The Japan Transport Safety Board (JTSB) examined the flight history, aircraft maintenance records, and witness statements. Investigators analyzed GPS data, which confirmed the aircraft's rapid descent and impact at roughly 12:42 JST. The investigation also reviewed the aircraft's weight and center of gravity, noting that the presence of multiple passengers placed the center of gravity in a rearward position, making the aircraft more prone to nose-up tendencies. Furthermore, the investigation looked into the mechanical state of the flight controls and the impact of the flap retraction on the aircraft's aerodynamic performance.