What happened
On November 11, 2017, at approximately 16:24 JST, two rotorcraft experienced a near-collision over Akashi City, Hyogo Prefecture. The first aircraft, a privately owned Robinson R44 II registered JA274J, was performing a flight from Yao Airport toward a temporary helipad in Taishi. Simultaneously, a Eurocopter EC135P2+ registered JA831H, operated by Academic Corporate Body HIRATAGAKUEN, was flying an emergency medical service mission from the Kakogawa Medical Center toward the Minami-Uozumi Rice Center.
As the two aircraft converged, the pilot of JA274J initially spotted the other aircraft at a distance. However, after momentarily shifting focus to maintain forward flight direction, the pilot realized the Eurocopter EC135P2+ was rapidly approaching. At their closest point, the aircraft were separated by only 30 to 60 meters horizontally and roughly 100 to 200 feet vertically. The pilot of JA274J performed evasive maneuvers, including a right turn and climb, to avoid contact.
The investigation
The Japan Transport Safety Board (JTSB) examined radar tracking records, air traffic control communications, and statements from the pilots and crew. The investigation focused on the visual identification capabilities of both crews and the flight paths of the aircraft. Investigators analyzed the relative speeds and headings of both rotorcraft to determine why the collision risk was not identified earlier.
Findings
- The investigation established that both aircraft were flying on a collision course, which made the other aircraft appear nearly stationary to the pilots, significantly delaying visual recognition.
- The pilot of JA2 .74J was unable to maintain continuous surveillance on the second aircraft while simultaneously monitoring the flight path, leading to a late recognition of the proximity risk.
- On the Eurocopter EC135P2+, the pilot was primarily focused on the flight destination, and while a mechanic acting as an outside observer spotted the Robinson R44 II, the warning came only as the aircraft were already passing each other.
- The two aircraft were operating on different radio frequencies, preventing them from sharing position information or receiving traffic updates from each other via ATC.
- Weather conditions were within visual meteorological limits, meaning visibility was not a contributing factor to the lack of identification.