Traffic Control Limits Cited in Cerritos Crash

The National Transportation Safety Board determined Tuesday that “limitations of the air traffic control system” were the probable cause of the collision of an Aeromexico DC-9 and a small plane over Cerritos that killed 82 people.

After a five-hour hearing the safety board announced it had concluded that the air traffic control system did not spot the small plane before it strayed into restricted air space and could not prevent the Aug. 31, 1986, accident.

The panel cited as contributing factors to the accident the “inadvertent and unauthorized entry” of the single-engine Piper Archer aircraft into the airspace of Los Angeles International Airport and the pilot’s visual limitations.

The board did not blame the air traffic controller on duty for failing to see the Piper on his radar screen because he was busy with other traffic. But the board said a reconstruction of what should have appeared on the controller’s screen indicated that the smaller plane could have been seen on the screen.

Development of New System

The board recommended that the Federal Aviation Administration speed up the development and installation of the Traffic Alert and Collision Avoidance System for use in airliners.

Once that system is working, the board recommended that the FAA require all other smaller aircraft flying into airport radar areas be equipped with altitude reporting devices.

It also recommended that software be added to airport computers that would alert air traffic controllers of potential conflicts between commercial and smaller aircraft.

The FAA should also take enforcement actions against pilots who intrude into airport radar areas without required air traffic control communications, the board said.

The DC-9 was on approach when it was struck by the Piper Archer at 6,560 feet shortly before noon on a clear, sunny Sunday.

Both planes plummeted into a neighborhood of Cerritos, killing 15 on the ground, destroying five houses and damaging seven others.

Safety board investigators said studies showed that under similar circumstances the Piper pilot should have had a 50-50 chance of spotting the jetliner within 25 seconds before impact.

Two people in the cockpit of the small plane should have seen the jet, which was eight times larger, within 38 seconds before impact, the investigators said.

No Radio Contact

However, the Piper was not in radio contact with the tower and the air traffic controller tracking the DC-9 did not see the smaller plane on his radar screen, so he gave no warning to the jet.

An autopsy showed that the Piper pilot, William Kramer, 53, had heart disease, but “we really have no evidence of a heart attack before the crash,” NTSB Chairman Jim Burnett said.

Kramer, of Rancho Palos Verdes, was new to the area, but he was known to be careful about preflight planning and sensitive to scanning for other planes, investigators said.

“We just don’t know why he did what he did. Whether it was a mistake, we just don’t know,” said Marty Speiser, a senior investigator who wrote the accident report.

Speiser defended the air traffic control system, saying it did not fail, but that it could not protect the two planes against the Piper’s intrusion into restricted airspace.

“If you avoid these areas, this (type of) accident doesn’t occur,” Speiser said.

Although the board’s finding didn’t single out any individual as causing the accident, Burnett said he believes Kramer, the Piper pilot, should have seen the DC-9 in time to avoid a collision, and said he would add a statement to that effect in the final report.

“I do not think that is true of the DC-9 flight crew, because by the time they were able to see the other aircraft it would have been the last seconds (before impact),” he said.

Frank Silane, Aeromexico’s lawyer, said after the hearing, “The evidence discussed here supports Aeromexico’s position there was no fault or wrongdoing on the part of Aeromexico or its flight crew whatsoever.”

Burnett said the see-and-avoid system for pilots to guard against collisions is a “very flawed” safety concept, but since mechanical methods aren’t foolproof it must be taken seriously “until we have something better.”

Board member Joseph Nall agreed that pilots cannot rely entirely on the air traffic control system, but also must watch the skies.

The air traffic controller tracking the Aeromexico jet on the radar screen was experienced and followed established procedures, Burnett said.

“It is unfortunate the controller did not observe the Piper and interpret it as a potential conflict, and give a warning to the DC-9 aircraft, but given the philosophy of the air traffic control system and the training he has had, the board did not find it beyond understanding,” Burnett commented after the meeting.

“We know from our reconstruction of what he had on his screen, he could have seen that aircraft there. Whether or not it was reasonable (that he didn’t), considering the requirement to give priority to other things, we cannot resolve,” Burnett said.

Investigators said that just before the collision the controller was busy tracking the Aeromexico jet’s path to the airport and warning another small plane that called in on its radio after straying into the area.

Proper Procedure

Burnett said air traffic control training provided that during a heavy workload the controller was “entitled and encouraged to ignore the kind of targets that were presented by the Piper in order to do higher priority work.”

During discussion of the accident report, board member John Lauber said the air traffic controller was “one of the most tragic characters of this accident,” because he followed procedure but that the system failed to effectively use available information.

“The problem stems from the fact that the fundamental basis of the air traffic control system is to separate the players from each other,” Lauber said. “He did not perceive the target.”

Additional built-in protections are necessary because, despite all the regulations, “Some pilot is going to blunder into restricted airspace,” he said.

Investigators cited as further evidence of the need for improved collision avoidance mechanism a Jan. 15 collision between a single-engine plane and a Sky West Airlines commuter plane over a Salt Lake City, Utah, suburb that killed 10 people.