FAA Defends Landing System Upkeep

The Federal Aviation Administration defended its maintenance of a key landing system at Los Angeles International Airport on Tuesday and vowed to keep technicians working until they diagnose what caused the sensitive equipment to malfunction twice in one week.

The agency denied assertions by LAX officials after a brief outage Monday that there were systemic maintenance problems, saying the navigation aid is subject to rigorous, regularly scheduled testing and monitoring.

The FAA’s technical operations director said he was still unsure why the Instrument Landing System on the south airfield went down, but he suspects the cause was “something inherent” in the equipment, which includes several antennae connected by cables to computer electronics.

“We have seen this on occasion at other airports, but it’s very infrequent,” said Steven Zaidman, vice president for technical operations at the FAA’s Air Traffic Organization. “This has become a real professional challenge for us to track down the problem. We haven’t seen one this difficult in a while.”

The FAA will keep a technician at LAX full time to work on the equipment and to reset it if it malfunctions, he said.

The FAA’s response was welcomed by airport officials, who on Monday questioned whether there was “something fundamentally wrong” with the landing system at LAX and demanded that it be fixed or replaced.

“We’re very pleased with the urgency and the thoroughness of the investigation,” said Paul Haney, deputy executive director of airports and security for the city’s airport agency. “We’re confident that the FAA will find the source of the problem and make any and all necessary repairs.”

With clear skies Tuesday afternoon, technicians got permission from controllers in the LAX tower to begin working on the landing system to try to figure out why it shut itself off on Monday and on Aug. 7, delaying many flights. The Aug. 7 outage delayed 46 flights, and Monday’s problems caused 13 delays, the FAA said. It was unclear whether the two incidents were related, Zaidman said Tuesday.

The landing system malfunctions came after several other air traffic control equipment glitches in Southern California in the last month. The problems have led LAX officials to question whether there are maintenance issues across the air traffic system. The FAA, which manages the nation’s air traffic control system, has said the outages were unrelated.

The mishaps started July 18, when controllers at a Palmdale center that handles high-altitude flights briefly lost all communication with pilots after a backup power system inexplicably went down. On July 26, a system designed to alert controllers at the LAX tower to potential collisions on the ground was partially disabled minutes before a turboprop plane narrowly missed a regional jet that had strayed onto its runway.

Problems with the Instrument Landing System at LAX began the weekend of Aug. 5-6, when it flickered and went out but was quickly reset. The equipment was down for 3 1/2 hours on Aug. 7 and about 40 minutes on Monday. FAA officials said Tuesday that the outages did not compromise safety.

“We have procedures in place, so if we have equipment outages the air traffic controllers can still keep the planes safely separated,” said Laura Brown, an FAA spokeswoman, adding that those procedures reduced the arrival rate at LAX when the landing system was down.

When the landing system goes out, pilots receive a warning telling them that the system has shut itself down. Controllers in the tower also receive an alert.

If pilots can see the runway, they are clear to land, but if they are too high, they must go around the airport and make another attempt, officials said.

The 9-year-old Instrument Landing System at LAX enables pilots to land on a runway without visual cues and is used regularly during periods of fog.

It includes several antennae that transmit radio signals that tell pilots where they are flying and what their altitude is in relation to the center of the runway. Cables connect the antennae to a series of computers in red and white sheds that sit a distance from the runway.

The system uses preset limits for the signals, so when one is interrupted, as it was on both Aug. 7 and Monday, it is designed to shut itself down, requiring a technician to reset the equipment.

The FAA generally doesn’t do preventive maintenance on the system’s electronics, Zaidman said, comparing them to a reliable appliance, such as a microwave oven or TV set.

But the agency is required to certify the landing system every 180 days by conducting flight tests to ensure the antennae signals are in alignment, he said. Although the system has been “historically very reliable,” technicians have seen corrosion in equipment, particularly when it is near a body of water, and found some intermittent cable and circuit board problems, he added.

Technicians who work on complex air traffic control systems for the FAA said they periodically encounter a particularly challenging system problem, like the glitches at LAX, that takes time to diagnose.

“Every major airport through the U.S. has one type of landing system or the other, and you very rarely hear of them having problems,” said Richard Riggs, a systems expert with the FAA technicians’ union. “But sometimes pieces of electronic equipment have a problem that’s pretty difficult to figure out.”