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Wednesday, September 11, 1991 - Page updated at 12:00 AM

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Lessons From Doomed Flight -- Lauda Says 767 `Had No Chance' But Findings Can Save Other Lives

The pilot, crew and passengers aboard a Lauda Air 767-300ER were doomed once the jetliner's left-side thrust reverser suddenly deployed last May over Thailand.

"They had no chance whatsoever," Niki Lauda, founder of the Vienna-based airline, said of pilot Thomas Welch, who grew up in Seattle, and the other 222 people who died on the flight. "There's no pilot in the world who could have kept his plane flying."

Lauda and Thai authorities have concluded the crash was caused by an engine thrust reverser that activated in flight.

Boeing officials have said it's premature to conclude what caused the crash, noting that the National Transportation Safety Board has not yet released its formal findings.

Lauda, in Seattle to meet with Boeing officials, said he was sick of "politics" that pit Boeing and the Federal Aviation Administration against pilots' organizations, passenger-safety advocates and the NTSB. He said politicking slows down solutions.

"We have come to the point where we should say, `This was the cause and this is the action we have to take,' and stop all this politics," Lauda said. "We do know why 223 people are killed, and now the important thing is we have to admit it, and find a solution, so at least we can say, `Unfortunately, 223 people got killed to save 100,000 other people's lives.' "

But Lauda credited Boeing officials with working earnestly to fix the problem with 767 reversers. He said Boeing is about to

propose a new design for a flawed safety feature that is supposed to automatically restow and relock the reverser should it ever begin to slip loose in flight.

The redesigned part, if approved by the FAA, could be installed on 767s in three to four weeks. In the meantime, operators of certain 767s have been ordered to deactivate the reverser systems.

Boeing's top engineer, Ben Cosgrove, told The Times Monday that the change may be as simple as adding more locks to the reversers and adjusting the wiring, although Lauda said Boeing engineers told him more extensive alterations were planned.

Lauda said questions raised about the potential hazard to passengers and flight crews on more than 1,400 late-model Boeing planes, including 747s, 757s and 737s, that use the same reverser system should be addressed swiftly. He said pilots should be warned that they could quickly have an uncontrollable aircraft on their hands if a reverser deploys.

So far, Boeing and the FAA have refused to upgrade pilot emergency instructions about what to do if a reverser warning light comes on in the cockpit, despite a call by the NTSB in early July to do so.

Currently, pilots are instructed to ignore the reverser warning light, which illuminates when the system starts to become unlocked in flight, unless it is accompanied by buffeting or yaw. The assumption is that the automatic restow device will quickly restow and relock the system.

But to play it extra safe until that device is redesigned, Lauda earlier told The Times that pilots should be instructed to shut down the engine at the first flicker of the warning light and divert to the nearest airport.

Lauda spoke to reporters yesterday after a chilling ride in a newly programmed 767 Boeing simulator in Renton.

As outspoken about the crash investigation as Boeing and the FAA have been secretive, Lauda related a harrowing description of what authorities now think the terrifying final moments of the flight probably were like.

In "a couple of seconds," the plane twisted and flipped completely over to its left, he said. A few seconds more and it was careening, nose aimed at the darkened jungle below, at the speed of sound - more than 600 mph, or 10 miles per minute, at that altitude and temperature.

Designed to withstand a maximum speed of 86 percent of the speed of sound, the plane plummetted three miles - from 24,700 feet to about 8,000 feet - in less than half a minute and then began breaking apart, he said.

"You're suddenly upside down in a dive; there's nothing you can do," he said. "It turns over, then it goes nose down, you go right into overspeed and then you lose all of your controls . . . The airplane broke up at exactly 17 seconds after it went out of control."

A certified commercial pilot, Lauda experienced a much different flight in a 767 simulator in London a week after the May 26.

After that simulated flight, he told reporters in Europe that he thought the plane probably yawed and buffeted a little, but that if the reverser was the only problem, the plane should have been easily controllable by the pilots. He surmised at the time that something else, perhaps a bomb or fire, caused the crash.

But in the 11 weeks since then, Lauda and others close to the crash have become convinced that the automatic restow device can, under certain rare circumstances, actually deploy the reverser.

After Boeing persuaded the FAA that automatic restow was highly reliable and made it virtually impossible for a reverser to deploy once the plane left the ground, the company was never required to calculate or test to see what would happen if the reverser somehow did deploy at a high altitude and high speed, as happened on the Lauda flight.

One bad assumption led to others: The simulators used for training pilots were programmed to simulate in-flight reverser deployment as a "controllable event" - even at high altitude and high thrust; and Boeing assigned the lowest priority caution to pilot instructions for how to handle in-flight reverser deployment.

But now, Lauda asserts, one valuable lesson that should not go unheeded is that modern jets - especially those with only one large engine mounted on each wing - are very dangerous if a reverser deploys in flight.

Aviation sources said this is because modern turbofan engines are positioned up close to the underside of the wing, jutting well out in front of the leading edge. This design makes for quiet, fuel-efficient power.

But it also sets up the potential that a sudden blast of reverse thrust on one side of the aircraft could severely interrupt the air flowing over the top of that wing. This disrupts lift, causing the wing to drop and the fuselage to roll over to that side.

At the same time, the opposite engine, operating under forward thrust, suddenly snaps forward, creating a radical yaw, or swerve, that accentuates the roll. The plane then is in a twisting dive headed for the ground.

"If it deploys in the air, you crash," Lauda said. "The problem is simply nobody ever expected that when the thrust reverser deployed in the air you couldn't fly the airplane anymore." ---------------------------------------------------------------

What happens when a thrust reverser deploys in flight

Recent simulator and wind-tunnel tests have shown - for the first time - how hig-thrust-in-flight deployment of the left reverser could have quickly snapped a Lauda Air Boeing 767 into an uncontrollable crash dive last May. Before the wind-tunnel tests, Boeing had relied on exptrapolations of low-speed tests - but no actual high-speed testing.

1. The Lauda Air 767-300ER leaves Bangkok airport en route to Vienna with 223 aboard. At 24,700 feet, climbing at more than 500 mph under near full thrust, the left engine's thrust reverser deploys - something that is supposed to occur only on the ground after the engines have wound down to idle.

2. Because the large turbofan engine is mounted close to the wing and juts well in front of the leading edge, the sudden blast of reverse thrust interrupts the air flow over the wing, disrupting lift. This causes the airplane to roll left, or counterclockwise.

3. As the airplane rolls, the right engine's high forward thrust makes the plane yaw, or swerve to the left, and snaps the right wing forward into the airstream. This produces additional lift on the right wing.

4. With no lift on the left wing, the plane's roll is accentuated, and it begins a twisting dive to earth. The forces generated could overcome the automatic pilot and leave little chance for corrective action.

5. Diving at 10 miles per minute, the Lauda plane may have careened down to 8,000 feet in less than 30 seconds, with the plane breaking apart under speed and forces it was not designed to withstand.

SOURCES: The National Transportation Safety Board, The Federal Aviation Administration; Niki Lauda --------------------------------------------------------------- Rob Kemp, Bo Cline, Randee S. Fox / Seattle Times

Copyright (c) 1991 Seattle Times Company, All Rights Reserved.

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