FAA Had Data on Jet Wake Dangers in ’91
The FAA had evidence dating as far back as October, 1991, that Boeing 757s caused 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 be linked to the B-757 phenomenon.
Wake turbulence occurs when a jet slices through the air, leaving a trail of horizontal cyclones that spring out from each wingtip.
The Federal Aviation Administration had previously said that it was not until early last year that it learned of the problem. But documents obtained by The 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 B-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 B-757s at the FAA’s request told the agency the plane had caused more turbulence than any plane ever tested, even planes nearly four times its size. The researchers speculated that the plane’s uniquely designed fuel-efficient wing may be the cause of the problem. They recommended that the FAA immediately require that smaller planes be kept four miles behind B-757s on final approach and that further testing be done.
When the most recent crash believed to be linked to the wake turbulence problem occurred--a Dec. 15 accident involving a twin-engine corporate jet carrying two executives of the In-N-Out hamburger chain--the plane was approximately two miles behind a 757 as it prepared to land at John Wayne Airport. All five people aboard perished.
* In October, 1991, Britain’s Civil Aviation Authority, the British equivalent of the FAA, presented a report at an FAA-sponsored symposium in Washington, saying the B-757 had been involved in a higher proportion of wake turbulence-related incidents than other aircraft its size. Calling the B-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 B-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 at the quarterly meeting of the FAA’s Air Traffic Procedures Advisory Committee.
“I can’t say that we were surprised” by the Santa Ana crash, said William Reynard, head of the Aviation Safety Reporting System. “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.”
Tony Broderick, the FAA’s associate administrator for regulation and certification, acknowledged that the FAA has had the data on B-757 wake turbulence, but said there was nothing alarming about it. But with no new information other than the two recent crashes, his boss, FAA administrator Hinson, issued a bulletin Dec. 22 to the nation’s air traffic controllers ordering them to give “wake turbulence” warnings to planes landing behind B-757s.
Broderick said the agency has begun further testing of the B-757.
In addition to the Santa Ana accident, eight people were killed in December, 1992, when a twin-engine jet flew into the wake of a 757 in Billings, Mont., and went down. Researchers Leo Garodz and Kirk Clawson said they conducted wake turbulence testing on a B-757 for the FAA on Sept. 25 and 26, 1990. The FAA had hired the National Oceanic and Atmospheric Administration to do the test. NOAA called on Clawson, one of its own researchers, and hired Garodz as a consultant. He is a decorated fighter pilot who had been with the FAA’s wake turbulence program for 20 years before retiring in 1986.
The tests were conducted in the NOAA vortex test facility near Idaho Falls, Ida., where such testing has been done for 20 years.
What Garodz and Clawson found both surprised and alarmed them: The narrow-body B-757 appeared to cause more wake turbulence than any plane ever tested by NOAA, even military planes 3 1/2 times its size. The B-757’s wake speed of 326 feet per second--222 m.p.h.--was more than the winds generated by Hurricane Andrew.
At one point during the test, which involved flying a B-757 past a 200-foot tower equipped with sophisticated electronic equipment, the force of the aircraft’s wake wrenched the equipment out of its mounting socket--a first in two decades of such testing, the researchers said.
The researchers issued a draft report of their findings in May, 1991. Although they did not submit the final version of the report until January, 1993, they presented their results publicly in October, 1991, at the FAA’s International Conference on Aircraft Wake Vortices in Washington.
Speculating that the unusually high level of turbulence may be linked to the B-757’s sleek wing and flap design, Garodz and Clawson recommended that smaller planes landing behind B-757s be kept four miles behind and that heavier aircraft stay three miles behind on final approach. That recommendation and another--that further testing be conducted--were ignored, the researchers said in interviews.
“We did not make (the recommendations) lightly,” Clawson said from his home in Idaho. “We felt that what the report did was bring it to the FAA’s attention. But they’re the regulatory agency. What happens after the report is up to them.”
Broderick of the FAA cautioned against lending too much weight to the NOAA report, saying “people make recommendations about all kinds of things. You have to evaluate . . . whether or not they are appropriate or make sense.” He said the data was not definitive.
At the October, 1991, symposium where Garodz and Clawson presented their findings, the Britain’s Civil Aviation Authority also reported on wake turbulence, documenting incidents involving the B-757 dating back to the early 1980s. The British agency noted a disproportionate number of wake turbulence-related incidents involving B-757s and advised further study.
In January, 1993, a month after the fatal accident in Montana, officials with NASA’s Aviation Safety Reporting System expressed their concerns about the problem in a teleconference call with FAA officials, according to Reynard.
Safety officials brought the subject up again in April at the quarterly meeting of the FAA’s Air Traffic Controllers Advisory Committee, Reynard said.
“It was of a concern to us,” he said. “It struck us that here we had this information, that we had conveyed it, and nothing happened.”
In retrospect, Broderick said, the FAA could have acted sooner in issuing the type of bulletin Hinson issued Dec. 22.
Broderick said neither the Santa Ana nor the Montana crash would have happened if the pilots had followed basic rules of airmanship. Pilots are always told to fly above the path of a leading jet to stay out of its wake, Broderick said. Furthermore, he said, both pilots were flying under visual flight rules, which meant the pilots, not air traffic controllers, were responsible for maintaining a safe cushion between their planes and the B-757s in front of them.
“It is a matter of physics that if in fact a following airplane stays above the preceding airplane, the following airplane will never encounter the wake of the preceding plane,” he said.
Other aviation sources say that at a minimum, the FAA was obliged to say what it knew about the B-757’s dangerous wake turbulence so pilots could take extra precautions when landing behind them. At most, some people, including researcher Garodz, believe the FAA should have mandated a three- or four-mile separation for aircraft landing behind B-757s in all circumstances until it conducted further tests.
A national aviation source who requested anonymity because he works with the FAA on rule changes said, “There is kind of a common concern that it often takes a catastrophic incident before the FAA does anything.”
Boeing spokeswoman Elizabeth Reese said the B-757 has been in service since 1982 and only recently has wake turbulence been cited in any accident. Last year, she said, the worldwide fleet of 574 B-757s logged 7 million safe hours in the air, traveling 2.7 billion miles and making 3.5 million landings.
The National Transportation Safety Board, which is investigating both crashes in which B-757 turbulence is believed to have been a factor, has asked the company for whatever data it has on B-757 wake turbulence, Reese said. She said the company is “helping out in the interest of aviation safety.”
Times librarian Sheila Kern contributed to this report.
