Officials Warned Years Ago of 757 Turbulence Danger

As he prepared for final approach into Atlanta’s Hartsfield Airport, the pilot nudged the throttle into idle, set the flaps at 15 degrees and engaged the landing gear. He had gone through this drill countless times before, but this landing would soon be anything but routine.

Without warning, the jet pitched violently to the right. As the pilot and co-pilot scrambled to gain control, the jet banked 75 degrees--2 1/2 times the standard turning angle--both steering wheels shimmied and an alarm wailed.

Just moments from impact, the flight crew advanced the throttle to the fire wall, hurtling the plane toward earth. After a few tense seconds, the crew managed to level the plane’s wings, pull up the nose and eventually touched down safely.

Only later would they learn what had happened: They had flown into wake turbulence caused by a Boeing 757 jetliner.

Details of dozens of similar close calls--from Los Angeles to London--are documented in previously unpublished records on 757 wake turbulence kept by the national Aviation Safety Reporting System and the United Kingdom’s Civil Aviation Authority.

On at least 46 occasions dating back to 1983, flight crews in the United States and the United Kingdom have filed written reports about close encounters with the unusually powerful turbulence caused by 757s.

In often dramatic fashion, the flight crews’ accounts underscore the potential danger of 757 wake turbulence, which is suspected in two fatal air crashes in the past 14 months, including one in Santa Ana Dec. 15 that claimed five lives. They also indicate that pilots recognized the force of 757 wake turbulence more than a decade ago and attempted to draw attention to it.

Flight crews routinely reported that 757 turbulence caused violent, “uncommanded” rolls of their aircraft, triggering “stall warning lights,” “stick shakes,” “dives” and rough landings that resulted in “tire bursts” and “tail strikes.”

“We have called for the 757 to be reclassified as a heavy (aircraft) for a number of years now,” a change that would require planes landing or taking off behind that type of jet to stay farther away, said David Mallino, president of the Air Line Pilots Assn. “This is something that has been a concern.”

The FAA has said that without further study, there is no need to increase separation between 757s and trailing aircraft.

However, with no new information other than the occurrence of the crash of a corporate jet in Santa Ana two months ago, FAA Administrator David Hinson issued a directive Dec. 22 requiring air traffic controllers nationwide to warn pilots of the turbulence caused by 757s.

“We feel that that is sufficient,” said FAA spokesman Fred O’Donnell in Long Beach. “Follow the established procedures for wake turbulence avoidance and you will stay out of trouble.”

The National Transportation Safety Board convenes Tuesday in Washington to address the 757 issue. While the NTSB is not a regulatory agency and does not have rule-making authority, the safety board routinely issues recommendations to the Federal Aviation Administration.

Wake turbulence occurs when a jet travels through the air, leaving an invisible, but potentially lethal pair of horizontal tornadoes emanating from its wingtips. The hurricane-force winds of these mini-cyclones can cause even mid-sized passenger jets to tilt violently, but they can treat smaller aircraft as if they were made of balsa wood. The turbulence is most dangerous during landing and takeoff.

Researchers suspect the 757’s sleek wing design is the culprit in the turbulence phenomenon.

The most recent accident believed to have been linked to 757 wake turbulence claimed the lives of two executives of the In-N-Out burger chain, when a twin-engine corporate jet landing about two miles behind a 757 at John Wayne Airport went out of control.

That accident came almost a year after a similar accident in which eight people were killed in Billings, Mont.

Thirteen of the 46 incident reports obtained by The Times through public information requests for the years 1983 to 1993 were filed as part of the federal Aviation Safety Reporting System, a 17-year-old program run by the National Aeronautics and Space Administration.

The system was created to red-flag potential aviation safety hazards. Because the information is collected confidentially--to encourage reporting--and without reference to aircraft type, there is no way to guarantee the culprit aircraft in every incident was a 757.

However, based on descriptions and technical clues in the reports, ASRS researchers suspect that 13 reports involved 757s. Copies of the same 13 incident reports were distributed to the FAA, NTSB, Air Line Pilots Assn., NASA headquarters and the Berlin Technical University in Germany--all of which are looking into the 757 wake turbulence phenomenon.

In the 33 British reports, the 757 was clearly identified as the source of the turbulence.

In a few cases, there were injuries to passengers and crew members.

In some instances, the planes sent out of control by 757 wake turbulence were MD-80s and Boeing 737s, which can weigh 100,000 pounds and more.

* In December, 1988, a jet taking off from Dallas-Forth Worth International Airport encountered turbulence from a 757 that had taken off moments before. “It took almost full aileron . . . to keep from rolling past 45 degrees,” a member of the flight crew wrote. “The wake I encountered was considerably more than normal.”

* In August, 1990, a jet taking off from Los Angeles struck 757 turbulence when it was just 100 feet off the ground--a particularly precarious situation, pilots say, because there is so little room to maneuver.

“We encountered the wake vortices . . . and we were in them until about 2,000 feet,” the crew reported. “During that time, we experienced very rapid roll rates . . . and full aileron was often required to keep the aircraft right side up.

“(This pilot) strongly suggests the FAA consider treating the (757) as a heavy for separation requirements.”

* Flying at 3,500 feet on final approach to the Atlanta airport in August, 1992, a jet encountered two blasts of 757 turbulence. The first caused the plane to roll 45 degrees to the right; the second pitched the plane into a “90-degree bank to the right,” shoved its nose down 10 to 12 degrees and nearly stopped the plane in its tracks, slowing its air speed “to zero in less than five seconds.”

The FAA considers a bank of 60 degrees to be acrobatic flying.

“It took between 130 to 140% torque to recover and start flying again,” the flight crew reported.

* A jet landing at the Dallas-Fort Worth airport in April, 1993, rolled right nearly 100 degrees when it ran into wake turbulence. The crew applied full throttle to escape, but then hit more turbulence, which knocked the plane back the other way no more than 60 degrees. The crew pulled up and landed uneventfully the next time around.

According to the incident report, this happened despite the pilot’s deliberately flying above the normal landing path in an effort to avoid the “nasty” turbulence that flight crews know is caused by 757s.

“I feel the (757) should be classified as a heavy jet and increased spacing should be used,” the author of the report, a member of the flight crew, wrote.

* In November, 1993, moments after departure from the Minneapolis airport, an MD-80 rolled 25 degrees left, then jerked back the other way 25 degrees. The flight crew wrote of the wake turbulence problem: “Let’s not use crisis management on this issue. We have a problem. Let’s fix it before people are hurt.”

* The flight crew of a 737 on approach to London’s Heathrow Airport reported this mishap five days before the fatal Santa Ana crash: “Aircraft rolled through 40 degrees. Turbulence initially light, then severe. Autopilot disconnected, full aileron plus rudder used to recover.”

Industry experts say it is unclear whether the NTSB will make any recommendations after Tuesday’s hearing. Like many of the pilots who have experienced wake turbulence, the Virginia-based Air Line Pilots Assn., and others in the aviation safety field say the medium-sized 757 should be reclassified as a heavy jet because it appears to be capable of producing wake turbulence more powerful than that caused by aircraft four times its size.

Reclassification of 757s would probably stir controversy because of its potential economic impact. It would require that pilots of smaller planes be given “heavy turbulence warnings” and that smaller planes be required to stay two miles farther behind 757s than the three miles of separation they now adhere to on final approach.

At busy airports, that could effectively push back all incoming planes, meaning potentially fewer flights and fewer paying passengers during optimal flying times.

It’s also unclear how the FAA would respond to any NTSB recommendations on the 757, although historically, NTSB spokesman Ted Lopatkiewicz said, the FAA has adopted 80% of NTSB’s safety advisories, changing flying rules to correct potential safety hazards.

Only last year the NTSB urged mass inspections of all planes equipped with a propeller it thought defective. The FAA took no action, and, a few months later, the propeller was blamed in a crash that killed South Dakota Gov. George Mickelson. The FAA subsequently ordered the replacement of propellers on all planes like the one that killed the governor and seven others.

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 NTSB should recommend that the 757 be reclassified as a heavy jet at least until further flight testing is done. That would increase the separation distance for most corporate and commercial jets from three miles to five.

“They should make sure the increased separation distance remains in effect until we get a better handle on the 757 wake turbulence problem,” said Garodz, an FAA specialist in wake turbulence for 20 years. “What’s causing this? Is it the super-smooth wing?

“There’s something going on back there,” he said.

In the meantime, Canadian aviation officials have already reclassified the 757 as a “heavy” plane and are requiring increased separation distances--five miles or six, depending on size--for planes landing and taking off behind 757s.

In the United Kingdom, Civil Aviation Authority spokesman Jonathan Nickolson said officials at Heathrow Airport have taken a similar step on a six-month trial basis. There, planes that used to be kept three miles behind 757s are being kept four miles behind; aircraft that once were held four miles at bay are now held back six miles.

Times staff writer Richard O’Reilly contributed to this report.