NTSB urges pilots to change landing distance calculations

CHICAGO, Illinois (AP) -- A year after a plane skidded onto a busy street after landing at Midway International Airport, the head of the National Transportation Safety Board urged airlines Wednesday to change the way they calculate stopping distances on slick runways.

The comments by NTSB Chairman Mark Rosenker came 10 1/2 months after the government panel recommended a more conservative method to figure out how much landing room is needed and two days before the anniversary of the accident that killed an Indiana child in a car struck by the airplane.

While the Federal Aviation Administration has recommended that airlines make the change, which entails not assuming thrust reversers will stop a plane on slippery runways, a new rule requiring the change has not yet been adopted.

Rosenker indicated he hoped his comments could help prevent a recurrence of the Midway accident as seasonally bad weather returns.

"We think airlines should voluntarily adopt the procedures contained in the FAA's (guidance) now, as we are entering another winter flying season," he said.

On December 8, 2005, Southwest Airlines Flight 1248 landed in a snowstorm, skidded off Runway 31-C through an airport blast fence and into traffic. The accident killed 6-year-old Joshua Woods of Leroy, Indiana, who was riding in a nearby car.

During the approach to Chicago on a flight from Baltimore, the pilots used a laptop which factored in wind speed and direction, airplane weight and runway braking action, then calculated the stopping margin.

Depending on whether the conditions were input as "wet-fair" or "wet-poor," the NTSB said, the computer calculated the remaining runway after stopping at either 560 feet or 30 feet.

The panel said the calculations were based on the assumption that the engine thrust reversers would be used immediately upon landing. However, it said, flight data recorder information revealed that the thrust reversers were not deployed until 18 seconds after touchdown, at which point there was only about 1,000 feet of usable runway remaining.

The safety board urged the FAA on January 27 to prohibit airlines from factoring in the use of thrust reversers when calculating stopping distances on wet runways. Had such an action been heeded for Flight 1248, it said, the computer would have indicated a safe landing was not possible on Runway 31-C.

FAA rules currently allow pilots of certain airplanes to assume that thrust reversers will be deployed immediately upon touchdown, which reduces the calculated landing distance.

Since the accident, Southwest Airlines Co. has adopted more restrictive conditions on landing calculations, requiring pilots to use "poor" if conditions are reported as "fair to poor." The FAA also mandated that pilots add 15 percent to the length of runway they think they need to land safely.

But Southwest spokeswoman Beth Harbin said Wednesday that the carrier continues to calculate thrust reversers into landings because it believes it gives a more accurate prediction of the landing performance.

"We believe having thrust reverser credit accounts for what will happen when you land," she said. "We believe you should factor that in, because that is the actual operation of the aircraft."

Rosenker noted that Midway has improved safety at its runways by installing a lightweight concrete bed designed to prevent planes from overshooting the runway.

The arrester bed of 1,764 water, foam and cement blocks is the first of four planned buffer zones at the airport.