Two small airliners on the ground at Los Angeles International Airport came within moments of colliding earlier this week after a malfunctioning system designed to alert controllers to potential collisions was partially disabled.
The pilot of one of the planes, which was taking off, averted disaster by pulling up suddenly -- risking a stall -- to avoid a regional jet that had just landed and strayed onto its runway. He cleared the aircraft by less than 50 feet, according to initial reports from the control tower.
Controllers described the incident as the closest call they have seen at LAX in seven years.
The incident began about 4 p.m. Wednesday, after America West Flight 6008 from Phoenix landed on the airport's southernmost runway. Controllers instructed the pilot to leave the runway on a taxiway known as "Mike" and stop short of the inner runway.
Even though the pilot read back the instructions correctly, he drove onto the inner runway and into the path of a departing United Express turboprop, said Laura Brown, a Federal Aviation Administration spokeswoman.
Horrified controllers watched the incident unfold from the LAX tower.
"Traffic unauthorized crossing downfield!" a controller yelled into the radio to warn the United Express pilot, who told authorities that he pulled up early after hearing the transmission.
Brown said the United Express pilot was "past the point where he could have stopped."
"It was fortunate in this case that the air traffic controller noticed the conflict and immediately alerted the pilot," she said, adding that a preliminary FAA investigation showed the vertical distance between the two aircraft was "less than 150 feet."
United Express Flight 6037 to Monterey, Calif., was taking off less than halfway down the runway in what's known as an "intersection departure."
Because of the incident, the city's airport agency said Friday that it will call a meeting of the FAA, pilots and airline officials to review "specifically whether midfield takeoffs are in the best interests of everyone's safety."
It's likely that the close call will be classified by the FAA as a Category A or Category B, the two most serious designations, Brown said. Officials attributed the incident to an error by the America West pilot, who told investigators he "got confused" when he reached "hold bars" on the taxiway that indicated where he was supposed to stop and instead continued forward onto the runway.
Controllers said the incident is likely to be deemed the most serious near-collision at LAX since Nov. 22, 1999, when an Aeromexico MD-80 that had just landed mistakenly crossed a runway on which a United Boeing 757 was taking off. The United pilot saw the Aeromexico jet and quickly got airborne, clearing it by 100 feet. Former Republican presidential contenders Bob and Elizabeth Hanford Dole were aboard the United flight.
Wednesday's incident came less than two weeks after a power outage and radar failure at a Palmdale center that controls high-altitude flights snarled air traffic across the country and prompted concerns about the vulnerability of the backup power system.
At the time of this week's incident, an audible alarm on a ground radar system designed to warn controllers that planes are too close was not operating, Brown said. Officials in the tower shut off the alarm after the system put out a false alert, but controllers could still see airplanes on the screen, she added.
Had the alarm been on, controllers said, they might have had a chance to warn the United Express pilot to abort his takeoff.
The incident marked the second time in less than a week that a close call between two aircraft occurred when the radar system, known as AMASS, or Airport Movement Area Safety System, was not operating properly. In Chicago on Sunday, a departing United Airlines Boeing 737 came within 300 feet of colliding with a Boeing 747 cargo plane on an intersecting runway at O'Hare International Airport. The incident was attributed to controller error.
The FAA hoped that AMASS, which the agency began installing at busy U.S. airports in the late 1990s, would help prevent collisions. Safety experts have criticized the equipment, which is prone to false alarms that sometimes prompt controllers to shut down the system.
Controllers also say that they are forced to shut the equipment off during bad weather because sheets of rain show up on the screen. Some experts question whether the system gives controllers adequate time to respond to its signals.
Experts say federal officials need to focus on communication between pilots and air traffic controllers as part of efforts to eliminate close calls.
"AMASS has a lot of serious problems," said Najmedin Meshkati, a professor of engineering the Viterbi School of Engineering at USC who studies aviation safety and runway incursions. "We really need to concentrate on human factors and not get bogged down in technological fixes."
With an ever-increasing number of takeoffs and landings at the nation's crowded airports, safety experts have warned that potential collisions between aircraft on the ground remain one of the biggest threats to commercial aviation today.
The rate of close calls at LAX has remained high despite years of efforts by local and federal officials to ensure that pilots and controllers follow federal rules allowing only one plane at a time on or near a runway. Among the nation's airports, LAX is unusual because airplanes cross active runways about 900 times a day.
There have been six close calls at LAX this year, compared with five for a similar period in 2005.
Wednesday's close call at LAX occurred just days before the city's airport agency is scheduled to start construction on the southern runway complex that it hopes will reduce near-collisions.
Officials will shut down the airport's southernmost runway, known as 25L, today and start rebuilding it 55 feet closer to El Segundo. In March, the agency will reopen the runway and start building a center taxiway in between the two runways to the south of the terminals.
Local and federal aviation officials hope that by separating the runways and installing a center taxiway, they will be able to significantly reduce close calls at LAX. About 80% of such incidents occur on the airport's south side after pilots land on the outer runway and use taxiways to cross the inner runway on their way to the terminals.
"The whole reason we have them tearing up the runway is so we don't have them peeling off the runway at a high speed," said Diane Aceves, a controller at LAX and local president of the National Air Traffic Controllers Assn. "Hopefully that will eliminate a lot of the runway incursions."