Taxiway Departure Attempt Triggers Changes At JAL, Changi

While the crew halted the takeoff relatively early after realizing the error, the Air Accident Investigation Bureau of Singapore called the incident “serious.”

The attempted departure of a Japan Airlines (JAL) Boeing 767-300ER from a taxiway at Singapore Changi Airport instead of the assigned runway on July 12, 2015, has led to procedural changes at the airline and the airport.

While the crew halted the takeoff relatively early after realizing the error—at roughly the same time that controllers ordered an abort—the Air Accident Investigation Bureau of Singapore (AAIB) called the incident “serious.”

The pilots did not report the incident until air traffic control queried the airline 11 days later, AAIB’s report reveals. The flight crew returned to Singapore for interviews, but the aircraft’s cockpit voice recorder and flight data recorder information had been overwritten. JAL was able to download pertinent data from the incident from a quick-access recorder.

After pushback, the Changi ground controller assigned a taxi route to Runway 20C. Rather than call out the specific route by naming taxiways, the controller used an approved alternative procedure, telling the pilots to follow “the greens,” referring to green taxiway centerline lights switched on during night and low-visibility operations.

Although the incident took place at 2:25 a.m. local time as the crew prepared to depart for Tokyo Narita Airport, the AAIB does not mention fatigue as a possible factor. However, confusion between the pilots and the controllers about what time the aircraft needed to depart in order to cross an enroute waypoint apparently played a role in the rushed departure.

Controllers had asked the crew for the latest time they would need to depart; the crew answered with the earliest time they needed to leave. The tower then called for an expedited taxi and issued a combined clearance to line up on the runway and take off ahead of an inbound aircraft.

As a result, the tower cleared the pilots to take off earlier than they typically would. The AAIB noted that a takeoff clearance is “usually given” to an aircraft as it approaches the departure runway. “The rationale is that aircraft should be closely watched as [it] approach[es] this position, to ensure that the aircraft is taxiing to the correct runway before a takeoff clearance is issued,” the AAIB said.

With the first officer at the controls, the aircraft lined up on a parallel taxiway ahead of Runway 20C and applied takeoff thrust, crossing a row of red stop-bar lights designed to keep aircraft on the approved green taxiway route. As the aircraft accelerated, both the pilots and controllers noticed the error.

Investigators determined the first officer “appeared to have fixated” on a mental picture of a taxi route that had not been assigned, leading to a confirmation bias. This occurred despite numerous indicators—including the red stop-bar lights—that the aircraft was off the assigned route. The AAIB faulted the pilots for not asking for clarification during calls with controllers and for not communicating better with each other. The board faulted controllers for giving a combined lineup and takeoff clearance. “Issuing a lineup clearance first and then a takeoff clearance later will give [air traffic control] a chance to monitor the aircraft’s movement to ensure that it is on the right route to the departure runway,” AAIB said.

Among the changes: Changi now provides specific instructions when the green taxiway lights are illuminated. The airport’s theory was that night and low-visibility conditions add stress for flight crews, so the “on-the- greens” terminology would minimize radio chatter. The JAL incident made clear the ramifications of misunderstood taxiway instructions.

JAL’s response included revamping its taxiing procedures in September 2015. Among the changes: The pilot flying should actively monitor outside cues such as signage to ensure the crew are following the assigned routes, and the pilot monitoring should call out all taxiway changes as the aircraft approaches turns. JAL also reviewed its Line Operations Safety Data and developed new training materials. 

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