O.C. Jet Crash Prompts Wake Turbulence Plan : Aviation: Federal safety board urges lengthened landing distances between planes, new weight classes for craft.
The National Transportation Safety Board on Tuesday approved a detailed set of recommendations designed to prevent airplane accidents caused by wake turbulence from Boeing 757 jetliners--the presumed culprit in a Dec. 15 crash in Santa Ana that claimed five lives.
The board’s action sent a strong message to the Federal Aviation Administration that the minimum distances between landing airplanes should be lengthened and that its 20-year-old weight-classification system for larger aircraft be overhauled to reflect a new generation of commercial jetliners.
The board also urged that air-traffic controllers provide more detailed information to pilots about wake turbulence and that training manuals be updated to emphasize the dangers of such airborne encounters--particularly when the trailing plane is smaller and more vulnerable to the miniature cyclones produced by rapid air movement across the larger aircraft’s wings.
NTSB records show that 51 instances of wake turbulence have occurred over the last decade, killing 27 people and damaging or destroying 40 airplanes.
Because it could potentially decrease the number of flights at an airport, the FAA has been reluctant to increase separation distances between 757s and trailing aircraft. But only a week after the crash of the corporate jet in Santa Ana two months ago, FAA Administrator David Hinson issued a directive requiring air-traffic controllers nationwide to warn pilots of the turbulence caused by 757s.
The safety board’s action on Tuesday, though not binding on the FAA, is expected to put more pressure on federal regulators to adopt the preventive procedures adopted unanimously by the board’s five commissioners.
FAA spokesman Paul Steucke said the agency would review the NTSB recommendations “immediately.”
“We’re aware of the problem and we’re taking measures to make sure there is not another occurrence,” Steucke said.
The fatal accident in Santa Ana occurred when a twin-engine corporate jet was on a landing approach to John Wayne Airport. The jet, which was about two 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.
Four other incidents attributed to 757 turbulence have occurred in the past 14 months, including a Dec. 18, 1992, crash in Billings, Mont., that killed eight people.
Despite the long list of safety recommendations, NTSB commissioners did not cite any particular flaw in the 757’s design. The heart of the problem, they said, was revising the FAA’s plane-classification system to ensure the proper separation between airplanes.
“There may be some unique characteristics of the 757,” said Commissioner John. K. Lauber, “ . . . but it is clear that the fundamental problem goes back to the outdated weight-categorization scheme that needs to be fixed.”
The board found that “inadequacies in the current airplane weight classification scheme . . . air control procedures . . . and pilot knowledge . . . of wake vortices were more important factors in the five recent accidents investigated by the Safety Board than any specific characteristic of the B-757 wake vortex.”
Under the present system, the 757 is considered a “large” aircraft, but industry experts have previously urged the FAA to reclassify it as a “heavy” aircraft and require most smaller planes to stay five miles back on final approach, as opposed to the three miles they are supposed to adhere to now.
The safety board on Tuesday took action on both fronts. It recommended that the separation distances be lengthened for smaller planes trailing 757s--even for jetliners such as Boeing 737s, MD-80s and DC-9s.
And it also urged that the three-tiered U.S. airplane weight-classification system be revised to narrow the weight ranges in some categories. Under present U.S. rules, the 757 is the heaviest aircraft in the middle-weight class.
Although it didn’t specifically say so, the board seemed to be leaning toward a version of the British system that divides aircraft into four weight categories.
Peter Murray, a veteran airline pilot who regularly flies 757s, said he believes the FAA should adopt the NTSB guidelines--at least until turbulence testing on the 757 is completed.
“If they can relax the separation standards later, fine,” Murray said. “But for now, safety should come first.”
The safety board also recommended that 757s and other large aircraft conduct landings on a more standard flight path angle. The board’s study of wake turbulence showed that trailing airplanes are in more danger of being thrown out of control when they fall below the larger plane’s descending flight path.
Because 757s and other newer jets can slow down quicker than older jetliners, trailing aircraft can inadvertently close in too quickly and wind up in this danger zone. NTSB staff members made it clear that maintaining a higher relative position to larger landing aircraft was the key preventive factor.
“The flight path is (the) critical factor), but maintaining proper distance is the best solution,” said John Clark, an aircraft performance specialist for the board.
The commissioners also recommended:
* Certain air-control procedures be amended to give pilots more information about the planes landing in front of them, especially if the leading plane is a 757 or “heavy” aircraft.
* Wake-turbulence warnings be issued more frequently.
* Training of pilots and air controllers include more detailed study of wake-turbulence dangers.
* Manufacturers be required to determine the wake vortex characteristics during aircraft certification procedures.
During discussion of the wake-turbulence issue, several new facts emerged about the Santa Ana crash.
The 757 was at 5,000 feet, Clark said, and had to make a sharply banked turn to the right in order to make its approach to John Wayne Airport. The Westwind corporate jet was at 4,000 feet and was heading straight in.
The Westwind jet was traveling faster than the 757, but the smaller craft’s pilot intended to stay safely above the larger craft, Clark said.
“The geometry of the flight paths, rather than the speed difference” was the critical factor, said Clark. Because landing clearances were issued to both planes in a short space of time, “the primary effect was to lose separation,” Clark said. Instead of staying far enough behind, the smaller jet was actually closing on the 757, Clark said.
Tests have indicated that the 757’s sleek wing design makes it capable of producing wake turbulence more powerful than that caused by aircraft four times its size.
The NTSB’s recommendations “all make sense to me,” said William Reynard, head of the nation’s Aviation Safety Reporting System, which noted an increase in 757 turbulence-related incidents in January, 1993, and, shortly thereafter, alerted the FAA.
“The process of looking at incidents in order to prevent accidents is very valuable,” he said. “You don’t have to have an accident first.”
Leo Garodz, a former FAA manager who was one of the first to bring the 757 turbulence problem to the FAA’s attention in 1991, applauded the NTSB recommendations--some of which were identical to ones he and co-researcher Kirk Clawson submitted to the FAA in a formal report three years ago.
“People at times don’t listen unless you have a Ph.D,” said Garodz, an ex-fighter pilot who worked in the FAA’s wake turbulence department for 20 years. “It’s frustrating.
“But this is great. I agree with all of them,” he said.
“If the NTSB is right,” said Christopher Fotos, editor of Avmark, a Washington-based airline industry newsletter, “this is a very serious problem. The FAA may have a hard time . . . dismissing it.”
The NTSB commissioners took nearly three hours to pore over the staff report and fine-tune its recommendations. One recommendation was eliminated altogether, and the board, at one point, was inclined to meld several technical points into a more general recommendation.
But staff members worried that the FAA would not respond as vigorously to the broader language.
Commissioner Lauber agreed. “We could receive the classic bureaucratic response: ‘We already have the proper rules, if they were just followed we wouldn’t have accidents.’ ”
Aviation officials in Canada and the United Kingdom have already implemented similar recommendations on the 757.
