Small Craft May Have Strayed Into Airport Approach Path

The light plane that collided with an Aeromexico jetliner over Cerritos may have strayed into one of Los Angeles International Airport’s principal approach routes without proper authorization, airlines and sources at the Federal Aviation Administration indicated Sunday.

Aeromexico officials said the DC-9 apparently was descending on its approach to the airport at 6,000 to 7,000 feet in altitude when it was struck by the Piper PA-28 over Cerritos in an accident that claimed at least 70 lives.

That would place the approaching airliner within the Los Angeles Terminal Control Area at the time of the collision. No aircraft is permitted to enter this airspace without the specific permission of Los Angeles approach controllers.

And FAA officials said that while the DC-9 was under FAA control at the time of the collision, the light plane was not.

In the moments before the collision, the Aeromexico pilot was talking on his radio to an air traffic controller. The officials said the light plane’s pilot was not believed to have been talking to anyone.

The FAA declined to give further details about the circumstances surrounding the accident Sunday.

Air safety experts and pilots familiar with landing procedures at L.A. International Airport say the controller should have warned the Aeromexico pilot if radar showed there was another plane nearby or on a collision course with the jetliner.

However, John Galipault, director of the Aviation Safety Institute in Worthington, Ohio, said the controller would not have been able to relay information about the light plane’s altitude unless the small craft was equipped with a transponder that broadcasts such information. As of Sunday evening, it had not been determined whether the single-engine Piper had a transponder linked to an altimeter.

And without transponder equipment, Galipault said, the controller might not have seen the light plane at all.

“Controllers’ radar is tuned up to receive targets with transponders,” Galipault said. “It’s quite possible that the echo from the (light plane’s) skin alone might not be terribly visible.”

At least three eyewitnesses to the collision said it was the small monoplane that appeared to strike the big DC-9, rather than the other way around.

Jim Cenami, 33, of Anaheim, who was driving a van east on the Artesia Freeway, said the smaller plane, which seemed to him to be climbing slightly and moving up from behind the DC-9, slammed into the jetliner. He said the Piper “plane actually hit the other one right behind the wing area in the fuselage . . . at a 45-degree angle.”

Richard Santana, 24, of Cerritos, who was outside his house about four blocks from where the main wreckage fell, said the small plane appeared to strike the jet’s under side in the tail section.

Eric Ainsworth of Los Angeles, returning from Riverside on the Artesia Freeway, said it appeared that the smaller plane appeared to strike the larger plane from below.

But aviation sources familiar with the maximum speed of the Piper and the minimum landing speed of the DC-9 said the jet was almost certainly flying faster than the propeller-driven plane, so the witnesses’ impressions of which plane struck which may be illusions.

In any case, they said, the question whether one plane was where it should not have been is probably more significant than which plane struck which.

Electronic proximity-warning equipment designed to prevent collisions in flight is still in the testing stages, and in the final analysis, avoiding such accidents is still up to the pilots.

“The pilots have the primary responsibility,” said Bill Bush, a spokesman with the National Transportation Safety Board in Washington. “They’re supposed to use the ‘see-and-avoid’ concept--make sure they keep their eyes open to avoid other planes in the area.”

Galipault said concerns over the inadequacy of present systems has led to a search for effective--and affordable--equipment to warn pilots that they are on a collision course with another aircraft.

Two threat collision avoidance systems, one active, the other passive, are currently being tested, but both are years away from widespread deployment.

Method Employs Radar

The active system currently under study by Piedmont Airlines employs ground radar that analyzes the course and altitude of each plane that it picks up and transmits the information to all other planes utilizing the system. Galipault said the principal problem is a price tag for each unit of $75,000 to $100,000, well out of the reach of the private plane market.

The passive system being developed for the Navy employs radar, a transmitter and minicomputer aboard each plane. The transmitter sends out a signal, the on-board radar listens for the echo, and the computer calculates whether a collision is imminent. Again, Galipault said, the price is currently prohibitive for private pilots.

Galipault said the need for effective collision avoidance systems is especially acute over the Los Angeles area.

“One-third of all the air traffic in the United States is over Southern California,” he said. “The FAA has estimated that if you take a given point in Southern California, there probably are 15 planes in the air within a radius of 4 miles. That’s pretty dense.

“And nobody has resolved the problem of how to keep controlled and uncontrolled airplanes separated.

“Everyone knew there was going to be another collision,” Galipault said. “We were bound to have one. It was just a question of where it was going to be.”