By ANDY PASZTOR, Via The Wall Street Journal
Further testing of aircraft needed before definitive cause determined
PHOTO: FRANK FRANKLIN II/ASSOCIATED PRESS
Federal investigators suspect potential brake problems, perhaps complicated by other factors, caused a Delta Air Lines Inc. jet to skid off a snowy runway at New York’s La Guardia Airport, according to people familiar with the probe.
After a normal approach and touchdown, thrust-reversers were deployed as expected, but the plane still veered off the runway at roughly 100 miles an hour, said one of those people familiar with the situation.
Based on preliminary information retrieved from “black box” recorders and pilot interviews, this person said, investigators are focusing on the performance of the braking system, which was set to operate automatically consistent with the airline’s procedures and safety rules.
Air-safety experts tracking the investigation stressed it is too early for definitive conclusions, pending further analysis, examination and testing of the brakes and maybe other systems.
The McDonnell Douglas MD-88 arriving from Atlanta skidded off the runway on Thursday, hit an embankment, crashed through a fence and ripped off some wheels before stopping with its nose perilously close to the frigid waters of Flushing Bay.
Two dozen of the 132 passengers and crew onboard primarily suffered minor injuries, though the accident shut down traffic at the busy airfield for three hours.
The probe also is delving into the condition of the runway, the impact snow or ice on its surface may have had on the effectiveness of the brakes and what pilots were told about braking conditions.
The airport’s operator last week said the strip had been plowed “literally minutes before” Delta Flight 1086 landed, and crews of previous arrivals reported acceptable braking.
Press officials for the National Transportation Safety Board, which is leading the investigation, declined to comment on the focus of the probe. On Sunday night, a Delta spokeswoman declined to comment while the investigation is pending.
So far, indications are that the crew didn’t approach too fast or land the twin-engine jetliner too far down the strip. Thrust-reversers located on the rear of the engines—movable panels designed to shift the direction of thrust to help slow down the jet in conjunction with brakes—seemingly functioned normally, according to one person familiar with the details.
The probe, however, is complicated by the unusually tricky handling characteristics of the MD-88, an 1980s-vintage workhorse serving relatively short-range routes.
Pilots and air-safety experts have long known that when the MD-88s reversers are deployed, its rudder, or large vertical tail panel intended to help turn the nose, sometimes may not be powerful enough to control left or right deviations from the center of runways.
Safety board investigators, among other things, are looking to see if this tendency played any role in the crash or if a crosswind affected the landing roll.
Moreover, the NTSB wants to determine if brakes on one side of the aircraft exerted greater pressure than those on the opposite side, potentially veering the jet off the centerline; and if computer-controlled features properly adjusted brake pressure to compensate for changes in runway friction.
Both pilots were interviewed during the weekend, according to people familiar with the probe’s progress, and the safety board is expected to issue an update perhaps as early as Monday.
If the preliminary theory pans out, the accident could provide ammunition for safety groups and pilot representatives urging adoption of new technologies to provide real-time runway braking reports to cockpits.
Canadian airports have adopted a version of such safety aids.
So-called runway excursions are much more serious problems overseas than in the U.S. Still, three years ago the Federal Aviation Administration decided such events were significant enough to warrant enhanced statistical tracking—similar to daily data gathered about near-collisions on runways between aircraft.
Globally, an average of about 30 aircraft skid off wet or icy runways each year, and the number of runway excursions has climbed sharply in recent years to become the primary cause of major damage to airliners.
Original story, via The Wall Street Journal.
A Press Release from the National Transportation Safety Board can be found, here.