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The First Petit Bench of the Supreme Court in a 4-1 decision on Oct. 26 upheld a Tokyo High Court ruling that had found two air traffic controllers guilty of professional negligence in connection with a near hit in 2001, which injured some 100 passengers and crew members aboard a jetliner. The two were the first air traffic controllers to be indicted over a near miss. Having received guilty sentences, although imprisonment was suspended, they will be dismissed in accordance with the national public service law.

Multiple factors are believed to have led to the near miss. Even the majority opinion in the Supreme Court decision said the two air traffic controllers should not be held solely responsible for the incident. While the decision serves as a reminder that air traffic controllers must do their utmost to avoid errors, it could unnerve them and lower their morale.

It could have another effect. If an accident happens, air traffic controllers, fearful that they may be indicted, may not disclose all the information they have during an investigation by the Japan Transport Safety Board. Thus, information useful in preventing accidents may not be forthcoming. Wide discussions should be held on how to build a system that will best prevent accidents and collect all the necessary information related to accidents.

The incident occurred on Jan. 31, 2001, over the sea off Yaizu, Shizuoka Prefecture, and involved Japan Airlines Flight 958 from Pusan to Narita and JAL Flight 907 from Tokyo’s Haneda to Naha, Okinawa Prefecture. Mr. Hideki Hachitani was directing flights as a trainee air traffic controller under the supervision of Ms. Yasuko Momii.

Since Flight 958 and Flight 907 were drawing closer to each other, Mr. Hachitani intended to tell Flight 958 to descend. But he confused Flight 907 and Flight 958 and gave instructions meant for Flight 958 to Flight 907. Ms. Momii failed to notice the error.

Consequently Flight 907 started to descend. Immediately, the Traffic Alert and Collision Avoidance System (TCAS) warned it to climb. But the pilot ignored the TCAS signal and continued to descend. Flight 958 was also descending because TCAS warned it to descend. As the two airplanes neared each other the pilot of Flight 907 nosedived his aircraft to avoid a collision. Flight 907 passed under Flight 958 with only about 10 meters seperating the two planes. Flight 907’s evasive maneuver injured some 100 passengers. The near mid-air collision occurred only about one minute after Mr. Hachitani gave Flight 907 the order to descend.

The majority opinion in the Supreme Court decision said that both Mr. Hachitani’s direction to Flight 907 to descend and Ms. Momii’s failure to notice his mistake of confusing Flight 958 and Flight 907 and to correct his instruction constituted professional negligence.

It also said that the pilot of Flight 907 continued to descend because he was following Mr. Hachitani’s command. It added that his instruction to the wrong flight led to “the materialization of a danger” and that there is a cause-and-effect relationship between his direction and the near collision.

The minority opinion given by Justice Ryuko Sakurai said that because the pilot of Flight 907 ignored the TCAS climb signal and the continuation of its descent gave rise to an “unexpected unusual situation,” the two air traffic controllers cannot be charged with professional negligence.

Besides Mr. Hachitani’s mistaken instructions, various factors contributed to the near hit. One is that the pilot of Flight 907 ignored the TCAS climb signal because he thought that if he climbed, the aircraft would stall. However, if he had climbed, the aircraft would not have stalled. But the pilot was unsure about the airplane’s airworthiness capability because he had not been given sufficient information about the aircraft.

Also there was no rule on what a pilot should give priority to — an air traffic controller’s direction or TCAS signals. (After the incident, it was decided that TCAS should be given priority.) At the time, no system existed that enabled air traffic controllers to recognize which signal — climb or descent — a TCAS was giving. These factors led the Tokyo District Court to find Mr. Hachitani and Ms. Momii innocent in the first trial. The lesson from the incident and other similar incidents is that air traffic controllers can make mistakes.

The air traffic control work at Haneda Airport, which is now a 24-hour facility with the addition of international flights, will become more complex because it uses four runways roughly arranged in a cross-hatch pattern. While the total air traffic volume nationwide has increased, the number of air traffic controllers has nearly leveled off. As a result, an average air traffic controller in 2007 had to handle 1.5 times more flights than in 1994. The government and the aviation industry must build a system that ensures air safety on the basis of the assumption that air controllers and pilots are not free from human error.

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