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Flight 427 probe ends this week

Sunday, March 21, 1999

By Matthew P. Smith, Post-Gazette Staff Writer

Bill Debo was in his car, going south on Route 60, when his eye was drawn skyward as the setting sun glinted off the shiny aluminum skin of a twin-engine jetliner on its final approach to Pittsburgh International Airport.

 
    Key dates in the Flight 427 story


March 3, 1991 - United Airlines Flight 585, a Boeing 737-200, rolls to the right and dives into the ground in Colorado Springs, Colo., during a landing approach from Denver, killing all 25 aboard. Investigators never identified the cause, but they suspect the rudder might have been involved.
Sept. 8, 1994 - USAir Flight 427, a Boeing 737-300 en route from Chicago, tilts to the left during descent into Pittsburgh International Airport and enters a nosedive, corkscrewing into the ground in Hopewell. All 132 people aboard are killed.
January 1995 - USAir warns its pilots to be alert for uncommanded rudder movements and issues instructions on how to respond to them.
Jan. 23, 1995 - The NTSB opens public hearings in Pittsburgh on the Flight 427 crash. Boeing discloses a list of more than 180 reports of in-flight problems involving the 737's rudder control system.
September 1995 - NTSB investigators spend about $1 million to conduct in-flight tests to measure the effects of wake vortexes on a 737. Before Flight 427 crashed, it encountered the wake vortex - a tightly wound coil of air trailing off each of a plane's wingtips - of a jetliner four miles ahead.
June 9, 1996 - Eastwind Airlines Flight 517, a Boeing 737-200 out of Trenton, N.J., suddenly rolls to the right during a landing approach in Richmond, Va. The pilot lands safely, and no one is injured. Investigators later determine part of the plane's rudder controlling mechanism was not adjusted properly.
July 1996 - The FAA says it will order U.S. airlines to upgrade nearly 6,000 planes by 2001 with more advanced flight data recorders that would monitor at least 17 parameters, including the rudder and rudder pedal positions. Flight 427's recorder monitored 11 parameters and did not record any rudder information, hampering the investigation. The rule was issued in 1997, and U.S. carriers have four years to comply.
October 1996 - The NTSB issues 14 safety recommendations to the FAA based on its investigation of accidents and incidents involving Boeing 737s.
Oct. 31, 1996 - Boeing issues an emergency service bulletin to airlines, alerting them that the rudder power control unit could jam and, under certain conditions, the rudder could move in the opposite direction of what was commanded.
Nov. 1, 1996 - The FAA orders all carriers test their 737 rudders following Boeing's warning. No problems were found.
Nov. 6, 1996 - USAir says it plans to buy 120 airplanes from Airbus Industrie, Boeing's chief competitor, and may eventually buy as many as 400 planes as it replaces older aircraft and simplifies its hodgepodge fleet of Boeing, McDonnell Douglas and Fokker aircraft.
Nov. 12, 1996 - USAir announces it is formally changing its name to US Airways, effective Feb. 27, 1997.
Jan. 2, 1997 - The FAA provides procedures for 737 flight crews to cope with unexpected, extreme rolls.
Jan. 15, 1997 - The FAA and Boeing announce plans to retrofit the domestic 737 fleet with a redesigned rudder power control unit and other new equipment at a cost of between $120 million and $140 million. The deadline for installation of the PCUs is August 1999. So far, about half of the nation's 1,025 737s have been upgraded.
September 1998 - Cracks are discovered in about a dozen hydraulic valves in the redesigned power control unit.
January 13, 1999 - The FAA proposes an order for domestic carriers to check for hydraulic valve cracks.
Feb. 19, 1999 - A United Airlines 737 experiences a stiff, sluggish rudder during a flight control check while taxiiing in Seattle. An investigation reveals that a mechanic improperly installed a spring valve guide in the PCU while reassembling the device after a test.
Feb. 23, 1999 - A Metrojet Boeing 737-200 begins an uncommanded roll while over Maryland after the wheel makes an unintended left turn while the plane is on autopilot. The pilots switched to a backup hydraulic system and make an emergency landing in Baltimore.
March 23-24, 1999 - National Transportation Safety Board convenes in Springfield, Va., to consider final report on its investigation of the crash of USAir Flight 427.


Related Article:

Most legal cases around 427 have been settled

 
 

It was Sept. 8, 1994, but Debo remembers it like it was yesterday. Because just as he glanced up at the plane, it rolled over to its left side and nose-dived to the ground.

"I kept yelling for the guy to pull up, pull up, but it disappeared. Then a mushroom cloud came up behind the trees," said Debo, 40, of Findlay.

He grabbed his cell phone and called KDKA. "The only thing I could remember at that point was Star 1020. I told them to call the emergency crews."

He stopped his car and ran to the crash site, but as soon as he got there, he knew he wouldn't find anyone alive. The only recognizable piece of what had been a Boeing 737 was the plane's tail section, which was standing on its end, about 10 feet high.

"Outside of that, the largest piece I saw was about the size of a pizza box," he said.

It has been 41/2 years since that evening, when USAir Flight 427 inexplicably crashed into a ravine in Hopewell near the Green Garden Plaza, killing all 132 people aboard.

On Tuesday, the National Transportation Safety Board will convene in Springfield, Va., where it will issue a final report on what has become the longest and one of the costliest air disaster investigations in its history.

On Wednesday, at the conclusion of the two-day meeting, the NTSB's five-member board is expected to issue the probable cause of the crash and also may issue safety recommendations relating to 737s. The NTSB has already issued 20 safety recommendations during the course of its investigation; 13 of them have been adopted by the FAA.

For many people, this weeks' meeting also has been anticipated because it may help bring a sense of closure to the disaster.

Count John Kretz Jr. of Munhall among them. His wife, Janet Stamos, was flying home from a business trip to Chicago aboard Flight 427.

The 47-year-old ironworker says he doesn't do much anymore besides go to work, go home, get something to eat and go to bed. For a time, he served as president of the Flight 427 Air Disaster Support League, a coalition of the relatives of the crash victims, but he's gotten away from even that.

"I'd like to see them have a definite cause and I'm sure a lot of people will be disappointed if they don't, because it makes you wonder whether they'll ever find a fix," he said. "Maybe if I do get some closure, I can start living, but it's never really going to be over. My life will never be the way it was."

The final report on Flight 427 has been widely anticipated in the aviation industry because the 737 is the most popular passenger aircraft in the world. More than 1,000 737s are in service in the United States and nearly 3,000 are in use worldwide. The findings also may help shed light on the unsolved crash of another 737, United Airlines Flight 585, which crashed in Colorado Springs, Colo., in 1991. A rudder problem also was suspected in that crash.

Within weeks of the 427 crash, the investigation focused on the rudder, the movable part of the tail fin.

Using computer analysis of the plane's movement, investigators determined that the plane's rudder swung to the left, causing the plane to go into its fatal roll. And only two things could have made that happen: either the pilots made a mistake, or there was an equipment failure that caused the rudder to move on its own.

That's the mystery the NTSB - along with Boeing, the Federal Aviation Administration and a host of other experts - has been trying to solve since the plane crashed.

It's puzzling largely because pilots normally don't use the rudder to steer the plane in flight. It's primarily used for directional control after landing, or in unusual cases where there's an engine failure or when landing the plane in a stiff crosswind, which makes it difficult to keep the nose pointed straight. Pilots steer a plane by turning a wheel, which moves the ailerons, hinged panels at the rear edges of the wings.

Just before Flight 427 rolled to its left, it was jostled by the wake vortex from a Delta Airlines 727 that was flying four miles - 70 seconds - ahead of it. Aircraft, likes boats, leave wakes, tight coils of air that spin off the wing tips of a plane. They are strong enough to roll the wings of a trailing jetliner, but not enough to flip it out of control.

But a series of flight tests in 1996 as part of the 427 investigation prompted a change in flying operations, which US Airways and other airlines adopted.

Test pilots found that when they were flying at 190 knots with the flaps lowered slightly and the rudder deflected to one side - conditions that mimicked Flight 427 just before it crashed - it was difficult for them to regain control. Only by pushing the nose down and increasing speed to 200 knots, or about 220 mph, were they able to regain control.

The increased speed provides more airflow over the wings, which gives the ailerons the ability to counter the effects of a misplaced rudder.

That finding might explain why 427's flight crew, Capt. Peter Germano and First Officer Charles Emmett, couldn't recover from the roll. But it doesn't explain what caused the roll.

Some aviation experts believe the pilots may have tried to use the rudder but it moved in the wrong direction, known as a rudder reversal. Boeing officials have said there has never been a documented case in which that has occurred in flight.

But tests conducted during the investigation have shown instances in which the rudder hydraulic power control unit can malfunction, and despite their insistence there was nothing wrong with the 737 rudder, Boeing in 1996 said it would install redesigned power control units in the planes. Boeing also agreed to pay the cost of that retrofit, expected to be between $120 million and $140 million. About half of the 737s in the U.S. fleet, or slightly more than 500, now have the new units. The rest are supposed to have them by August.

Tests conducted on the hydraulic unit taken from the 427 plane were inconclusive. Investigators were able to make the two valves inside the unit jam, which could have made the rudder misbehave, but only under certain conditions that officials have said were unlikely to occur in flight. Some have questioned the test results, however, because some of the parts were damaged in the crash and had to be replaced before the testing was done.

Even if the NTSB is unable to arrive at a probable cause for the crash, the FAA believes the redesigned rudder, new training procedures to help pilots deal with upsets and other safety measures have fixed whatever flaws that may have existed in the 737 rudder controls.

Thomas McSweeny, the FAA's associate administrator of regulation and certification, said the agency is confident the 737 is a safe airplane that has been made even safer.

Citing a lack of evidence that the rudder malfunctioned, Boeing officials say the only other plausible explanation is that the pilots either acted improperly or didn't react quickly enough to save the plane when it started to roll.

In a report submitted to the NTSB, Boeing officials suggest the pilots, on the last leg of a routine, three-day trip, were startled by the wake vortex encounter on a calm clear evening, and that could have precipitated a series of mistakes that resulted in the fatal roll.

Boeing officials have forwarded a theory that one of the 427 pilots, in trying to counter the wake vortex, turned the control wheel and also stepped on the rudder pedals. They theorize that the pilot became so engrossed in trying to regain control that he forgot he was still pushing hard on the rudder pedals while trying to use the ailerons to get the plane back to level.

That submission drew a sharp response from US Airways and the Air Line Pilots Association, both of which claimed that Boeing's hypothesis had no basis in fact. ALPA officials believe the plane's rudder went in the reverse direction and that in any case, the plane was out of control within four seconds and could not have been recovered.

US Airways, in its submission, asserted that the crash was caused by an uncommanded rudder movement or rudder reversal that pilots had not been trained to recognize or deal with. Moreover, US Airways blamed Boeing for failing to advise airlines that the ailerons could not overcome the force of the rudder at slower speeds.

NTSB Chairman Jim Hall has complained frequently during the investigation that it has been hampered by a lack of data from the black boxes that were on Flight 427. All U.S. commercial aircraft are equipped with a digital flight recorder that monitors the planes' movements and some of its flight control surfaces that pilots use to steer the plane.

In the event of a crash, investigators can use the data to reconstruct the accident.

Modern airliners have flight data recorders that record more than 100 kinds of data, or parameters. The recorder on Flight 427 measured only 11 parameters, and while it met FAA standards at the time, it did not record critical functions like the movement of the plane's rudder or rudder pedals.

Had the plane been equipped with a more advanced black box, the mystery probably would have been solved years ago. That lack of progress prompted Hall to demand that the FAA require airlines to install more modern flight data recorders on their planes. The FAA eventually agreed, but those newer recorders will not be in place for another two years.

Just last month, a Metrojet 737 flying from Orlando, Fla., to Hartford, Conn., experienced a rudder problem in flight. The pilots regained control after shutting off the rudder hydraulic system and made an emergency landing in Baltimore. The incident is being investigated by the NTSB, but like Flight 427, the Metrojet plane was equipped with an 11-parameter flight recorder that can't tell investigators anything about the rudder movements.

Bill Debo, whose job as a sales representative for gas and oil drilling equipment requires him to take business trips frequently, keeps abreast of problems with 737s and had read about the Metrojet incident. He hopes the NTSB comes up with a definitive answer because he believes there's something wrong with the 737.

"I fly in them all the time. And so when I fly, I want to fly in a safe environment," he said, conceding that he sometimes says a Hail Mary before takeoff.



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