Piper Was on Screen in Midair Crash : But Final Report on Cerritos Disaster Still Blames System

The light plane that struck Aeromexico Flight 498 over Cerritos appeared on an air traffic controller’s screen moments before the collision and crash that claimed 82 lives last Aug. 31, National Transportation Safety Board investigators concluded Wednesday in their final report.

The report, which continues to place primary blame for the in-flight collision on “limitations” of the air traffic control system, rather than on any individuals, is the final word after thousands of hours of investigation into the worst air disaster ever in the Los Angeles metropolitan area.

Walter R. White, 35, the Federal Aviation Administration air traffic controller who was guiding Flight 498’s approach to Los Angeles International Airport for 4 1/2 minutes before the collision, has maintained throughout the investigation that he never saw the single-engine Piper Archer on his radar screen.

Radar Was Tracking Piper

But as early as last December, investigators said taped data showed that a radar system at the Los Angeles Terminal Radar Control facility at Los Angeles International was tracking the small plane.

The report released Wednesday went further and asserted that the data picked up by the radar was displayed on White’s screen.

“Given the evidence,” the report said, “. . . the safety board concludes that the positions of the Piper airplane were depicted on (White’s) display.”

The board said that two images representing the Piper appeared on White’s screen. One was a small, computer-generated triangle, and the other was a larger representation called a “primary target.”

The board said there were three possible factors that could have caused White to “overlook” the Piper:

- White’s attention may have been drawn away by another light plane that appeared to threaten Flight 498’s airspace or by some runway changes that he was making for the jetliner’s scheduled landing at Los Angeles International.

- White may have assumed that the Piper was flying above or below the Los Angeles Terminal Control Area, or TCA, when the collision occurred. The TCA is restricted, layered airspace, and only planes with automated transmitters called “Mode C transponders” that broadcast data on their altitudes are permitted within it. Since the Piper did not have such a transponder, a controller might assume that it presented no hazard to a jetliner in the TCA.

- While the triangle generated by the radar’s computer appeared on White’s screen, there is a possibility that the Piper’s larger “primary” image was weakened by atmospheric interference or may not have appeared on White’s screen at all. The board said White may have been relying on the primary returns to mark traffic, and with the distractions, “it is possible and understandable” that he might miss the smaller, computer-generated triangle.

John K. Lauber, the NTSB member who headed the Aeromexico investigation--and who currently is heading the probe of last week’s Northwest Airlines crash in Detroit that killed at least 154--has taken pains to point out that White is not considered the villain in the collision over Cerritos.

Lauber called White “one of the most tragic characters” in the accident and said White was a “conscientious performer” who was carrying out his primary responsibility: to separate aircraft under air traffic control that were authorized to be in the TCA.

“The controller was clearly acting in accordance with existing (FAA) directives,” Lauber said.

Richard Cox, White’s boss, said Wednesday that White is “one of the best” of the controllers at Los Angeles TRACON and he considers the men and women there “the finest air traffic controllers in the world.”

White, who has declined to be interviewed, is working in a staff position at the facility, but Cox said he expects him to return to a control position in the near future.

As it did when it released an abridged version of its conclusions last month, the NTSB said Wednesday that the failure of the FAA’s air traffic control system to protect aircraft from collision was the “chief probable cause” of the Aeromexico accident.