What happened
On June 3, 2015, at Naha Airport, a series of events led to a serious runway incursion involving three different aircraft. The incident began when a Japan Air Self-Defense Force CH-47J helicopter, registration 57-4493, took off from taxiway A-5 and approached the active runway. Simultaneously, an All Nippon Airways Boeing 737-800, registration JA80AN, was cleared for an immediate takeoff on runway 18. As the ANA aircraft began its takeoff roll, the crew observed the approaching helicopter and determined that continuing the takeoff posed a significant danger, leading them to execute a rejected takeoff.
At the same time, a Japan Transocean Air Boeing 737-400, registration JA8938, was on final approach for landing on the same runway. Although the aerodrome control tower issued an instruction for the JTA aircraft to perform a go-around, the aircraft had already entered the flare phase. The pilot, having received landing clearance and being unable to confirm the status of the ANA aircraft, proceeded to land. The JTA aircraft touched down on runway 18 before the ANA aircraft had successfully vacated the runway area. There were no injuries to the passengers or crew on any of the three aircraft.
The investigation
JTSB investigators examined air traffic control communications, flight data recorder records, and cockpit voice recordings from all involved aircraft. The investigation focused on the sequence of clearances, the visibility of the aircraft to one another, and the effectiveness of the communication between the control tower and the pilots. Specifically, the investigators looked into why the SDF helicopter crew misunderstood their takeoff clearance and why the tower was unable to identify a faulty read-back from the helicopter crew.
Findings
- The primary cause of the incident was the rejected takeoff of the ANA Boeing 737-800 (JA80AN) caused by the presence of the SDF CH-47J (57-4493) crossing the runway path.
- The JTA Boeing 737-400 (JA8938) landed on the runway despite the go-around instruction because the crew had already initiated the landing flare and reverse thrust operations by the time the instruction was received.
- The pilots of the SDF helicopter mistakenly believed the takeoff clearance intended for the ANA aircraft was meant for their own aircraft. This error went uncorrected because the controllers could not hear the incorrect read-back, likely due to the technical characteristics of the VHF receiver used for communications.
- The ANA crew decided to abort the takeoff because they could not determine the flight path of the approaching helicopter and perceived a high level of risk.