A monitoring system that alerts flight controllers when an aircraft enters an airport runway to prevent accidents was operating normally when a Japan Airlines jetliner collided with a Japan Coast Guard aircraft at Tokyo's Haneda airport earlier this week, the transport ministry said Friday.
The function causes the entire runway to flash yellow on the controller's display, with the aircraft in red, when it detects an entry. Investigators will look into the possibility that the controller may have missed the onscreen alert.
The Ministry of Land, Infrastructure, Transport and Tourism has said the controller did not grant permission to the JCG plane to enter the runway, while the JAL jetliner's pilots have told an internal probe that they could not visually confirm the presence of the coast guard aircraft when touching down.
Several factors, including human error, may have caused Tuesday's deadly accident that killed five of the six people aboard the JCG's Bombardier DHC8-300 aircraft. Detailed investigations by the Japan Transport Safety Board and the Tokyo Metropolitan Police Department are currently underway.
"While it is unclear whether the controller was watching, there is no rule that requires them to constantly monitor the screen," a ministry official said.
According to the JTSB, the JAL passenger jet's flight recorder was retrieved Wednesday, but its voice recorder has yet to be found. All 379 people aboard the JAL Airbus A350 escaped without life-threatening injuries.
The accident, which occurred around 5:47 p.m. Tuesday, forced the temporary closure of all four runways at Japan's busiest airport. All except the one where the collision occurred were reopened later in the day after the cancellation of many flights.
The final runway is scheduled to be reopened on Monday, according to transport minister Tetsuo Saito, who also said that staff will be deployed to monitor the runway alert system on a constant basis from Saturday. Further emergency measures will be announced next week, Saito added.
According to the ministry, the runway occupancy monitoring function was introduced to prevent human errors following multiple runway incursions in 2007. It was implemented on all four runways at the Haneda airport by March 2011.
Accurately determining the position of aircraft in rainy weather or when they moved into the shadow of a building proved difficult under conventional radar systems. The new function allowed for more accuracy as it enabled controllers to confirm the presence of aircraft both visually and through the display.
The 39-year-old captain of the JCG plane, who survived the accident, said he was cleared to enter the runway, according to the coast guard.
But flight control data showed controllers directed the JCG plane to proceed to a holding point, stopping short of allowing it to enter the runway where the collision happened.
Controllers then continued communicating with several other aircraft. There was no record of them instructing pilots of the JAL plane to perform a go-around or take other measures.
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Crew's quick decisions behind safe escape from burning JAL plane
JAL pilots did not see coast guard plane when touching down
JAL jet passengers recount 18 minutes of terror while awaiting escape
