FAA withheld warning of turbulence from 757s

January 04, 1994|By Los Angeles Times

SANTA ANA, Calif. -- The FAA had evidence dating as far back as October 1991 that Boeing 757s cause unusually dangerous wake turbulence, but the agency issued no public warning until last month -- after the deaths of 13 people in two plane crashes believed to have been linked to the phenomenon.

Wake turbulence occurs when a large plane slices through the air, leaving a trail of horizontal cyclones that spring out from each wingtip.

The FAA had previously said that it wasn't until early last year that it learned of the problem. But documents obtained by the Los Angeles Times indicate that the agency was aware of the problem long before FAA Administrator David Hinson issued a nationwide directive Dec. 22 that air traffic controllers begin issuing "wake turbulence" warnings to pilots landing behind 757s.

Since the fall of 1991, at least two formal reports on the dangers were given to the FAA, in addition to anecdotal evidence gathered from pilots by the National Aeronautics and Space Administration:

* In October 1991, two researchers who conducted wake turbulence studies on 757s at the FAA's request told the agency that the plane caused more turbulence than any ever tested before. The researchers speculated that the plane's uniquely designed fuel efficient wing may be the cause of the problem. They recommend that the FAA immediately require that smaller planes be kept four miles behind 757s on final approach and that further testing be done.

* Also in October 1991, the United Kingdom's Civil Aviation Authority, the British equivalent of the FAA, presented a report at an FAA-sponsored symposium in Washington, saying the 757 had been involved in a higher proportion of wake turbulence-related incidents than other aircraft its size. Calling the 757 an "anomaly" among similar aircraft, the report said, "it is important to address the B-757 problem."

* Officials with the NASA-run Aviation Safety Reporting System, after collecting and reviewing 757 turbulence-related reports from pilots nationwide, brought the problem to the FAA's attention twice in 1993: once in a teleconference call in January, and again in April.

The most recent crash believed to have been related to the wake turbulence problem was that of a twin-engine corporate jet carrying two executives of a hamburger chain and three other people. The plane was about two miles behind a 757 Dec. 15 when it went out of control as both planes were landing at John Wayne Airport in Costa Mesa, Calif. All aboard the smaller craft perished.

rTC "I can't say that we were surprised" by the latest crash, Bill Reynard, head of the Aviation Safety Reporting System, said, referring to the Costa Mesa accident. "The [conditions] were such that we felt there was a high probability that something was going to happen. That's why we brought it up in the first place."

Besides the Costa Mesa accident, eight people were killed in December 1992 when a twin-engine jet attempting to land behind a 757 in Billings, Mont., apparently flew into the jetliner's wake and went down.

Researchers Leo Garodz and Kirk Clawson said they conducted wake turbulence testing on a 757 for the FAA Sept. 25 and Sept. 26, 1990.

What Mr. Garodz and Mr. Clawson found both surprised and alarmed them: The narrow-body 757 appeared to cause more wake turbulence than any plane ever tested by NOAA, even military planes 3 1/2 times its size. The 757's wake speed of 326 feet a second -- 222 mph -- was more than the winds generated by Hurricane Andrew.

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