What happened
On April 14, 2021, at approximately 08:10 JST, a privately owned Cessna 525A, registration JA001T, departed from runway 27 at Yao Airport under instrument flight rules. The flight was carrying the captain and six passengers. During the initial climb, as the aircraft reached an altitude of approximately 500 feet and entered a cloud layer, a flock of roughly ten birds suddenly emerged from the clouds and passed in front of the aircraft.
The captain reported hearing a collision sound against the rear of the airframe. Following the impact, the pilot requested a return to the airport to inspect the aircraft. The flight proceeded to an altitude of 5,000 feet as instructed by air traffic control before returning to land normally at 08:26. While no engine or instrument anomalies were noted during the flight, a post-landing inspection revealed significant damage to the left horizontal stabilizer, including a large dent in the leading edge skin and deformed ribs. Subsequent detailed inspections determined the damage required major repairs.
The investigation
The Japan Transport Safety Board (JTSB) investigated the incident to determine the cause of the airframe damage. Investigators examined the aircraft's flight path, meteorological conditions, and the physical evidence left on the airframe. DNA testing was performed on bird feathers found adhered to the horizontal stabilizer, which identified the species as a gray heron.
Investigators also reviewed the bird strike history at Yao Airport and the preventive measures managed by the Airport Office. The investigation noted that while the airport maintains a wild animal collision prevention program, the specific collision occurred approximately 2 nm west of the airport, outside the immediate runway environment.
Findings
- The damage to the Cessna 525A was caused by a collision with a bird from a flock that suddenly appeared from within the clouds.
- The species involved was a gray heron, a bird noted in safety guidelines for its heavy weight and high potential for causing significant aircraft damage despite lower collision frequency.
- The pilot was unable to perform evasive maneuvers because the flock emerged abruptly from the cloud layer during the climb.
- No injuries were reported among the seven occupants on board.