Overview
On April 14, 2021, at approximately 08:11 JST, a privately owned Cessna 525A (registration JA001T) collided with a bird during climb after take-off from Yao Airport. The aircraft, which had seven occupants (captain and six passengers), sustained damage to the left horizontal stabilizer. No injuries were reported.
Aircraft and Flight Information
The aircraft, serial number 525A-0311, was manufactured on June 25, 2006, and held a valid airworthiness certificate. The 60-year-old captain held an airline transport pilot certificate and a type rating for the Cessna 525, with total flight time of 8,207 hours (2,167 on type).
The flight departed Yao Airport runway 27 at 08:10 under instrument flight rules. During initial climb at an indicated airspeed of approximately 150 knots, the aircraft entered clouds at about 500 ft above ground level. A flock of approximately 10 birds suddenly appeared from a gap in the clouds and passed near the aircraft. The captain heard a sound consistent with a collision from the aft section and immediately requested air traffic control to return to the airport. The aircraft climbed to 5,000 ft and landed safely on runway 27 at 08:26. No abnormal engine indications or airframe vibrations were noted during the remainder of the flight.
Damage
Post-landing inspection revealed a dent on the leading edge skin of the left horizontal stabilizer, measuring approximately 9 cm long, 41 cm wide, and 5 cm deep, with deformed ribs. The damage was assessed as requiring major repair, classifying the event as an aircraft accident on April 27, 2021.
Bird Strike Analysis
DNA testing of feathers found on the stabilizer identified the bird as a gray heron (Ardeidae family). According to the guideline for the bird strike prevention program, gray herons are considered high-risk due to their weight (1.02–2.073 kg) and potential for causing significant aircraft damage, though strike frequency is low. The accident site, about 2 nm west of Yao Airport at 500 ft, lies in an area with rivers, ponds, and green spaces that serve as feeding and breeding grounds for gray herons.
Bird Strike History at Yao Airport
Between August 2010 and May 2021, 13 bird strikes were reported at Yao Airport. Eight occurred at 50 ft or below during take-off or landing, four (including this accident) occurred between 130 and 500 ft along the take-off path of runway 09/27, and one was at an unknown altitude. This was the only recorded strike involving a gray heron and the only one investigated by the Japan Transport Safety Board.
Preventive Measures
The Yao Airport Office had established a wild animal collision prevention program, which included grass mowing, bird expulsion methods (e.g., smoke, vehicle horns), and monitoring of bird presence. Observations noted six ardeidae birds annually near the airport's drainage and reservoir. Information was shared via a restricted-access platform.
Conclusion
The Japan Transport Safety Board determined that the bird strike occurred when the flock suddenly appeared from cloud cover, leaving the captain insufficient time to take evasive action. The damage was consistent with a collision with a gray heron.