United Landing Mishaps Probed: 2 Airbus A320s Have Veered Off Runways
Two United Airlines planes careened abruptly off runways in recent months, apparently after crossed wiring on landing-gear brakes caused wheels to lock.
The incidents, both involving Airbus A320 aircraft, are being investigated by the National Transportation Safety Board and are among a flurry of airliner mishaps, suggesting there may be holes in aviation’s safety net.
It’s highly unusual for mechanical failures to send large airliners skidding off runways, safety experts say. What is alarming to investigators is that the same issue, crossed wiring, happened to two United A320s within a four-month period. Three carriers outside the U.S. have experienced similar anti-skid failures with A320s, sources said.
"How do we make sure it doesn’t happen again?" said Peter Knudson, spokesman for the National Transportation Safety Board.
United said it found no additional wiring problems when it checked the landing gears on its fleet of 97 Airbus A320s following the latest runway incident, which occurred last month in Jackson Hole, Wyo.
It is one of several major American carriers in the spotlight as Congress and the Federal Aviation Administration probe maintenance miscues.
Last week American Airlines and Delta Air Lines canceled hundreds of flights as mechanics checked their fleets of MD-80s for potential wiring problems. United earlier in the month pulled aside seven Boeing 747s for hasty reinspections, while Southwest grounded 38 Boeing 737s. The FAA also ordered airlines to inspect more than 600 Boeing 737s for a potentially faulty bolt that may have triggered an inferno on a China Airlines jet last summer. All 165 people aboard were evacuated before fire engulfed the plane.
The groundings and mishaps raise the curtain on regulators’ increased reliance on the airlines to police themselves and to ensure that mechanical work is performed to exacting standards.
What’s more, regulators count on a new computer system to flag safety concerns as aircraft maintenance is increasingly outsourced to subcontractors scattered around the globe, but the technology that is supposed to direct FAA inspectors to potential hot spots is only as good as the data entered into it. And that data is gathered and supplied by the airlines themselves.
"Either we don’t have an adequate number of people to evaluate the data," said Jim Hall, former chairman of the NTSB, "or the data is being ignored or mishandled by the FAA personnel. If the latter is the case, I’d be very concerned about what’s happening with the safety culture at the FAA."
Furthermore, federal safety inspectors say they spend the bulk of their time in front of computer screens, rather than walking around maintenance-shop floors. Without the threat of unexpected FAA inspections, workers may be tempted to cut corners.
"That’s a deterrent, and they’ve eliminated that 100 percent," said Linda Goodrich, an FAA inspector who is vice president of the Professional Aviation Safety Specialists union.
Congress sets hearings This week two congressional committees are slated to investigate recent safety lapses. One concern on Capitol Hill is whether FAA staffing has kept pace as the bulk of airline maintenance has spread from relatively few airline shops to thousands of vendors around the world.
Even congressional Democrats who have sounded alarms on safety issues concede it is implausible to hire enough inspectors to examine work done on the nearly 350,000 airplanes flown within the U.S. The FAA has 3,800 inspectors, a number that has remained relatively flat over the past decade. An agency representative did not respond to a request for comment.
The sudden interest in aircraft upkeep comes during a period of unprecedented safety in air travel within the U.S. Large commercial jets have been involved in only one fatality over the past six years, when a Southwest Airlines aircraft slid off a runway at Chicago’s Midway Airport and killed a boy inside a motor vehicle.
While Congress ponders how to strengthen the public-private partnership that ensures airplane safety, the NTSB, FAA, Airbus, United and its mechanics and pilots unions search for answers on the recent A320 incidents.
Federal inspectors think the braking systems on both United jets likely failed because the tachometers, which measure wheel speed, had been wired backward, according to the NTSB, apparently during routine maintenance. As a result, the anti-skid system that controlled braking on the inboard wheel was reading the speed of the outboard wheel, and vice versa. When a tire started to skid, the system released pressure on the wrong brake, causing the overstressed tire to shred and the aircraft to pitch sharply off the runway.
Incident at O’Hare The first United Airbus plane to suffer anti-skid failure veered off, and then got back on, Runway 22 Right at Chicago’s O’Hare International Airport at 8:30 p.m. on Oct. 9. A flight attendant and a passenger were injured.
The plane, which had flown in from Seattle, mowed down lights lining the runway as pilots brought it under control. They guided the damaged plane to United’s terminal, although some turbine blades had been shattered as runway lights were sucked through the engines, according to a witness.
Sources say the plane’s landing gear had been repaired recently by a United vendor. United said its mechanical work was done according to an FAA-approved maintenance program and that United mechanics on site at vendors provide "independent surveillance, as does the FAA."
On the evening of Feb. 25, a United Airbus A320 jet fishtailed as it landed on Jackson Hole Airport’s short runway. The plane pivoted off the runway at a 90-degree angle as its anti-skid system failed, its engines scooping up chunks of snow and ice as it slid about 150 feet.
After the pilot asked if anyone was injured, a passenger calmly pointed out that an engine was on fire. Flight attendants opened exits, triggering evacuation slides, one of which failed. "Feet first! Help at the bottom!" they yelled as passengers, including Andrea Matthews, jumped from the plane.
The fire had burned itself out as Matthews reached the bottom of a slide at the aircraft’s rear, she said. But she noticed the engine glowing orange as she and 118 other passengers trudged to the runway through 5-foot-deep snow. The plane had come to rest 116 feet past the runway’s end and 140 feet to the right of its centerline, according to the NTSB.
The heavy snow surrounding the runway acted as a brake and also may have prevented the plane from breaking up, said Ray Bishop, airport director at Jackson Hole Airport. "Had it been summertime, it probably would’ve been much worse."
Later, Matthews came to the sobering realization that had the brakes failed on the other side of the jet, the craft could have slammed into an airport building rather than a snowfield.
"You’re fine, but you might’ve died," Matthews said.
Federal officials, United and Airbus are investigating the incidents to see where the system failed and why two potentially catastrophic mechanical problems occurred within such a short stretch. They have found that in addition to the crossed wiring, United’s mechanics in Denver placed the wrong landing gear on the 10-year-old plane involved in the Jackson Hole incident.
Still to be determined is whether United or its vendor properly tested the aircraft for anti-skid failures, whether United took the right steps to alert mechanics of the wiring issue following the October incident, and whether the maintenance manual or landing-gear design contributed to the wiring problems.
Union, airline at odds Steve MacFarlane, national director of the Airline Mechanics Fraternal Association, which represents United’s mechanics, claims the airline is loath to disclose maintenance issues that arise at its vendors, although he wouldn’t say if that was the case with the A320 incidents.
"It really isn’t in their interest to share that information," he said. "We would use this information to show that the maintenance is not as good, the standards are not maintained."
For its part, United said it freely shared news of the braking issue with its vendors, mechanics and other unions.
"We informed our mechanics, pilots and flight attendants of the incidents and the corrective steps we are taking," said Megan McCarthy, a United spokeswoman. "We further conducted a stringent review process with our maintenance partners to ensure they had the same information."
United is working with federal investigators to find the root cause of the recent incidents, including the effectiveness of tests its mechanics use to ensure the A320 anti-skid systems work properly, McCarthy said.
"Our primary responsibility is the safety of our customers and our employees, and there is no obligation we take more seriously," she said.
jjohnsson@tribune.com
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