FAA Increases Span Between 757s, Smaller Planes : Aviation: The four-mile distance is designed to prevent accidents involving wake turbulence. The NTSB had urged six miles.
Citing a crash that killed five people in Santa Ana in December, the Federal Aviation Administration has adopted a policy that will require smaller planes to stay farther behind Boeing 757 jetliners to prevent airplane accidents caused by their potentially hazardous wake turbulence.
But the regulatory agency’s action--part of a detailed set of new policies on 757s--falls short of safety recommendations made by the National Transportation Safety Board this year. Aviation safety experts and pilots’ advocates said the changes are merely a first step toward making the skies safe for aircraft landing and taking off behind 757 jetliners.
FAA Administrator David R. Hinson outlined the policy in recent days in a letter to NTSB Chairman Carl W. Vogt.
Beginning July 1, the FAA will require air traffic controllers handling landings to keep aircraft four miles behind 757s--instead of the current three miles--to protect them from the miniature hurricanes produced by rapid air movement across the larger aircraft’s wings.
The safety board recommended in February that the FAA adopt minimum separation distances of up to six miles behind 757s. The FAA is not bound by the NTSB’s recommendations.
At least two accidents that claimed 13 lives and three other serious incidents have been linked to 757 wake turbulence since December, 1992. Because the separation rules could potentially decrease the number of flights at the nation’s airports and cut into revenues of the hard-hit airline industry, the FAA has been reluctant to increase distances between 757s and tailing airplanes.
Although the NTSB does not consider the 757 to have any structural flaws, researchers have speculated that its unique, sleek-wing design may be the cause of the turbulence that can be unusually powerful for an aircraft of its size.
Both fatal accidents occurred when smaller jets flew into wake turbulence as they were preparing to land.
The Santa Ana crash occurred when a twin-engine corporate jet was on a landing approach to John Wayne International Airport. The jet, which was 2.1 miles behind a Boeing 757, went out of control and slammed nose-first into the ground near the Santa Ana Auto Mall. All five aboard, including the top two executives of the In-N-Out Burger chain, were killed. The NTSB is still investigating the accident, but turbulence from the 757 is said to have played a part.
The other fatal crash occurred in Billings, Mont., in 1992. Eight people were killed.
NTSB spokesman Mike Benson said the safety board will review the FAA’s new policies and draft a response over the next several weeks.
Bob Flocke, a spokesman for the Air Line Pilots Assn., said: “We think it’s a good beginning. It certainly addresses part of our concern. But it doesn’t, for instance, address separation on departures.”
The association, the largest pilots organization in the world, recently issued its own advisory on 757s, recommending that pilots of smaller aircraft--even MD-80s, Boeing 737s and DC-9s--remain five miles or at least two minutes behind 757s on final approach, Flocke said. The organization also has recommended that pilots ask the control tower for extra time when taking off behind 757s, Flocke said, to give more time for the turbulence to diminish.
Despite concerns from other corners of the aviation industry, the FAA said it believes that the four-mile separation is safe enough--for now.
“The FAA believes that this interim increased separation will provide an extra margin of safety without unnecessarily impacting system capacity,” Hinson wrote in a May 20 letter outlining the changes to Vogt.
The four-mile separation, Hinson wrote, recently was adopted by the Civil Aviation Authority in England and “has significantly reduced the number of reported incidents” there.
As part of its new policies on 757s, Hinson said, the FAA is embarking on a two-year test with the help of the National Aeronautics and Space Administration to determine the precise level of danger that 757 wake turbulence poses. The four-mile separation limit will remain in effect until testing shows whether additional distance is warranted, Hinson said.
After its investigation, the NTSB in February unanimously advised the FAA to overhaul its 20-year-old aircraft weight classification system, which is used to set separation distances.
The FAA said an overhaul was not warranted now, but that it would study the issue.
Leo Garodz, a former FAA manager who was among the first to bring the 757 wake turbulence problem to the agency’s attention in 1991, said the new policies represented an initial step, but nothing more.
“It’s a beginning, but it’s only a beginning, because there’s going to be another accident, because things are not that precise at airports when there is a heavy traffic load,” Garodz said.
