What happened
On the evening of June 14, 2018, a pair of Japan Air Self-Defense Force (JASDF) F-15J aircraft, registrations 52-8/850 and 32-8818, entered runway 36 at Naha Airport without authorization. At the time of the incursion, a Ryukyu Air Commuter Bombardier DHC-8-402, registration JA84RC, was on final approach for landing after receiving clearance from air traffic control.
The incident began when a scramble alarm activated the two fighter jets at the Naha Air Base. The formation, consisting of a lead aircraft and a wingman, taxied out of the alert hangar during rainy and dark conditions. While taxiing, the formation leader was navigating unfamiliar terrain, noting a lack of taxiway centerline lights and managing a heavy aircraft loaded with external fuel tanks.
As the formation approached the runway, the Naha Tower instructed the fighters to hold short of runway 36 to prioritize the landing of the incoming commercial flight. Although the formation leader read back the instruction, he subsequently entered the runway. The wingman, focused on maintaining position in the dark, followed the lead aircraft, mistakenly believing they had received clearance to line up.
The investigation
The Japan Transport Safety Board (JTSB) examined air traffic control communications, radar tracks, and runway occupation records. The investigation focused on the movements of the two JASDF aircraft and the commercial Bombardier DHC-8-402. Investigators looked into the familiarity of the pilots with Naha Airport's specific ground procedures, the impact of the weather conditions, and the communication protocols used between the formation and the tower.
Findings
- The formation leader misinterpreted the instruction to hold short as a clearance to enter the runway for takeoff.
- The lead aircraft failed to follow the specific Naha Air Base protocol, which requires the leader to confirm the wingman's readback of ATC instructions before entering the runway.
- The wingman did not intervene because he believed he had missed a clearance to enter the runway.
- The formation leader was unfamiliar with the lighting and taxiway layout at Naha Airport, having recently transferred from a base with exclusive military runways.
- High pressure to depart quickly and the distractions of navigating wet, dark taxiways contributed to the error.
Safety action
Following the incident, the 9th Air Wing of the JASDF implemented several measures, including:
- Mandatory reading back of "HOLD SHORT OF RUNWAY" instructions, which was not previously required for the second aircraft in formation.
- Enhanced training regarding human factors and ground operations at night.
- Improved educational programs for personnel transferred to Naha Air Base to ensure familiarity with local airport infrastructure and communication procedures.