What happened
On October 10, 2012, at approximately 11:22 JST, a Bell 206B helicopter, registration JA9745, operated by Nakanihon Air Service Co., Ltd., was conducting a visual flight rules (VFR) mission toward the Suzuka Mountains. The helicopter was carrying a pilot-in-command and two trainees at an altitude of 2,000 feet.
Simultaneously, a Mitsubishi MU-300, registration JA30DA, owned by Diamond Air Service, Inc., was returning to Nagoya Airfield after training operations. The jet aircraft was also operating under VFR at 2,000 feet. While the helicopter was flying west-southwest, the jet aircraft was instructed by air traffic control to hold over Mamba Bridge for a low-level flyby mission. During a counter-clockwise turn over the bridge, the JA30DA approached from the left rear of the JA9745 and overtook it on the left side. The aircraft passed within approximately 390 meters of each other, with a vertical separation of roughly 50 feet. No injuries were reported, and neither aircraft sustained damage.
The investigation
The Japan Transport Safety Board (JTSB) examined radar tracking records and air traffic control communications to reconstruct the flight paths. The investigation reviewed the sequence of instructions provided by the Nagoya and Chubu Terminal Radar Control Facilities. Investigators also analyzed statements from the crew of the JA9745, including the trainee who first spotted the approaching jet, and the crew of the JA30DA. The investigation also looked into the effectiveness of the traffic information provided by controllers to both aircraft prior to the encounter.