AW&ST
From Aviation Week & Space Technology 07/29/02
Japan Debates TCAS When Controllers Err
EIICHIRO SEKIGAWA/TOKYO
A report on the worst near-collision in Japanese airline history--one with 677 lives at stake--has aroused public concern about the quality of the nation's air traffic control system, especially because what went wrong in the skies west of Tokyo was hauntingly similar to the July 1 tragedy in Germany.
The incident occurred Jan. 31, 2001, near Yaizu and involved a Japan Airlines 747-400 (Flight 907) that had taken off from Tokyo's Haneda airport bound for Naha, Okinawa, and a JAL DC-10-40 (Flight 958) heading from Pusan, South Korea, to Tokyo's Narita airport.
The report cites human error, panic, confusion and training inadequacies that led the two wide-body transports to cross with a vertical distance of just 20-60 meters (66-197 ft.) and horizontal distance of 105-165 meters at an altitude of 35,300-35,600 ft. The Transport Ministry is recommending that pilots rely on instructions given by their traffic-alert and collision avoidance system (TCAS) units ahead of those from air traffic controllers.
THE JULY 12 REPORT by the Aircraft and Rail Accident Investigation Committee of the Ministry of Land, Infrastructure and Transport concluded that the Japanese ATC conflict alert system, called CNF, functioned inadequately. It also said Japanese and International Civil Aviation Organization TCAS regulations are inadequate, as are JAL's TCAS training and regulations.
JAL Flight 907 (JA-8904) took off from Haneda at 3:36 p.m. local time.The weather was calm with good visibility, which helped prevent a collision because the pilots could see each other's aircraft.
The 747 was cleared to 39,000 ft. toward Yaizu about 60 mi. west of Tokyo. The DC-10 (JA-8546) was flying east at 37,000 ft. via Kowa VOR/DME station.
The airspace around the city of Yaizu was managed by two controllers at the Tokyo Air Traffic Control Center: a 26-year-old trainee and his 32-year-old instructor. The trainee had two years of experience and began his shift 75 min. before the incident. He controlled 14 aircraft between 3:43 and 3:52 p.m. and transmitted 37 times, including 18 ATC instructions. The supervisor had 10 years of experience and had been on the job for 40 min. when the incident occurred.
The committee said first notice of the incident occurred at 3:54:15 p.m. when a CNF conflict alert signal appeared on the trainee's radar screen concerning Flights 907 and 958. However, the trainee was focusing on American Airlines Flight 157 because it was approaching JAL Flight 907. The investigation showed that he forgot about the presence of JAL Flight 958. (Flight 157 subsequently played no part in the incident.)
When he did focus on it, he attempted to resolve the conflict between Flights 958 and 907 by having the DC-10 descend from 37,000 ft. to 35,000 ft. But he nervously mixed up the flight numbers of the two JAL aircraft, calling on Flight 907 to descend to FL350.
At the time, the 747 Flight 907 was climbing through 36,900 ft. and turning left while the DC-10 was flying level at 37,000 ft. at a 095-deg. heading.
The 747 crew had already seen the contrail of the DC-10 at 11 o'clock. When the trainee called on them to descend, the 747 captain was puzzled as to why an ascending aircraft would be instructed to descend under the circumstances. Nonetheless, he followed the controller's instructions and responded, "JAL 907, we descend to FL350. The other traffic is in sight."
Initially, the controller did not make the mental connection that he had ordered the wrong aircraft to descend and took the Flight 907 acknowledgment as confirmation of his order. Meanwhile, the DC-10 crew had no way of knowing that the descend order was actually meant for them. They maintained their course. Since he could see that the DC-10 was not descending as he intended, the trainee tried to establish a horizontal separation between the aircraft. This time, at 3:54:38 p.m., he correctly called to "JAL 958" to turn to 130 deg., then to 140 deg. But his voice was so low that the DC-10 crew did not hear the instruction and failed to respond.
THE ROCKWELL COLLINS TTR 920 TCAS units in both aircraft showed a traffic advisory (TA) alert at 3:54:18 p.m. It changed to a resolution advisory (RA) at 3:54:34 p.m. in the DC-10 and 3:54:35 p.m. in the 747--about the time the controller was issuing his new order for Flight 958 to turn.
The TCAS RA prompted the crew of both aircraft to take evasive action--the 747 crew to climb by 1,500 fpm. and the DC-10 crew to descend by 1,500 fpm.
The supervisor controller took command at 3:54:57 p.m., but she also became momentarily distracted by the CNF alert and didn't focus on the DC-10, the investigators reported. She instructed Flight 907 to climb and intended to call for Flight 958 to descend. But she mistakenly called for "JAL 957" to descend, the report said. That elicited no response because there was no such flight in the area.
So at 3:55:02 p.m. she tried again, this time instructing Flight 907 to climb to FL390. The 747's TCAS unit instructed it to increase its climb rate to 2,500 fpm. So the aircraft was initially given a descend instruction by ATC to 35,000 ft. and several seconds later got just the opposite instruction--to climb--from its TCAS unit. Twenty-five seconds after the initial ATC instruction to descend, the tower also told the crew to climb.
The 747 captain (age 40, with 7,747 total hours, including 3,758 hr. in 747s) said he was concerned that his engines couldn't spool up fast enough to make an effective climb, so he elected to continue to descend, thereby neglecting the instructions of his own TCAS unit and the tower.
When he caught sight of the approaching DC-10, he increased his rate of descent to 4,060 fpm. He crossed safely beneath the DC-10 at 3:55:11 p.m.
The DC-10 crew had responded to the RA alert by pitching down and deploying speed brakes. However, the 45-year-old captain (6,584 total hours; 5,690 hr. in the DC-10) could see the contrail of the approaching 747 and realized the two aircraft could collide. The captain said later that he couldn't figure out why both
aircraft had been instructed to descend.
His 49-year-old first officer (4,333 total hours; 3,874 hr. in DC-10s) also saw the contrail and simultaneously with the captain pulled back on his yoke. The two exchanged no words as they performed this action and as the captain increased thrust. A moment later they saw the 747 pass beneath them.
The DC-10 captain told the controllers at 3:55:21 p.m. that he had experienced an RA signal and critical near-collision. The supervisor controller replied, simply, "Roger, 90 . . . 8," giving the wrong flight number again.
At 3:55:32 p.m., the 747 captain reported that the DC-10 had flown on and that the emergency had passed. The supervisor responded, "Roger."
Passengers in the DC-10, though shaken, were unhurt and the flight proceeded to Narita. But the situation in the 747 was a different story.
THE CAPTAIN HAD JUST turned off the Fasten Seatbelt sign when the drama began. His evasive action included a vertical acceleration of -0.55g to +0.59g. Of the 411 passengers on board, 344 had kept their seatbelts fastened. Fifty-three of these people were injured, mostly lightly. But 35 of the 67 whose seatbelts were unfastened were injured. Seven passengers and two cabin attendants were injured severely, mainly when they hit the ceiling or other people fell on them.
The severity of the situation was illustrated by two 112-lb. service carts that hit the ceiling. One jammed itself into the overhead support structure; the other fell on passengers. The crew elected to return to Haneda for medical aid, where the flight was met by 43 ambulances and 155 rescue staff.
The ATC trainee and supervisor were suspended from their duties, as was the 747 captain. The DC-10 captain continued in service.
The investigations committee cited 14 reasons for the incident, including a distracted trainee handling traffic, his and his supervisor's failure to remember that Flight 985, the DC-10, was in the airspace, and the fact that both controllers were upset by activation of the tower's CNF alert system. The committee said that normally the CNF would turn on 3 min. before a collision, but its activation was delayed because the 747 was turning left.
THE FINDINGS ALSO cited the trainee for erroneously instructing the 747 to descend, and the lack of sufficient training by the 747 crew of a TCAS event. The 747 crew also was cited for descending contrary to the TCAS instructions. The dangers of service carts flying around the cabin were cited, along with the fact that some passengers elected not to wear their seatbelts.
Beyond those immediate findings, the committee said there was insufficient mutual understanding between controllers and pilots, and a vague description of the relationship between TCAS instructions and ATC instructions. Favorable visibility and the prompt action by the pilots are credited with having prevented the situation from becoming more serious.
Prior to the report, and the midair crash in Germany, the Japanese public was said to have taken ATC expertise for granted. The revelation that a trainee and his supervisor could forget the existence of an aircraft, mix up flight numbers, repeat a wrong call number and not recognize their own mistakes has raised a public debate about the safety of the ATC system.
The committee said Japan's rules are too vague regarding the relationship between controllers and TCAS. Besides improving Japan's CNF system, the committee has also pushed for a "TCAS first" principle. The Transport Ministry has signaled its agreement with those conclusions.
But relying on TCAS has prompted some dissent among pilots, who question the reliability of the systems. They are concerned that crews will be punished if they follow TCAS instructions rather than those of air traffic controllers.
Japanese prosecutors said they are considering filing charges against the trainee and supervisor for negligence.
The ministry said it expects to field a system by 2004 that will use digital displays to show the controller's instructions in the cockpit.
ŠJuly 29, 2002, The McGraw-Hill Companies Inc