Investigators probing the second-deadliest air crash in US history are weighing new evidence about pilot action and aircraft design, according to industry sources and documents.
Sources familiar with the investigation of American Airlines Flight 587 say the National Transportation Safety Board has found nothing so far to indicate a mechanical flaw caused the crash in New York that killed 265 people.
The Airbus A300-600 went down shortly after takeoff from John F Kennedy Airport on November 12, 2001. The most vexing question is why the plane’s tail fin fell off, causing it to spiral into a residential area in Queens.
From the start, investigators have scrutinized co-pilot Sten Molin’s use of the rudder over a period of several seconds to try and gain control of the aircraft after it was buffeted by unusually strong turbulence.
The rudder is a vertical movable panel on the back of the tail fin that moves the nose of the plane.
A report by an outside expert on aircraft stability and control, submitted recently to the board as evidence, suggests the design of the plane’s flight control system could have played a role in the accident, the worst since a 1979 American Airlines crash in Chicago that killed 273 people.
Ronald Hess, vice chairman of the mechanical and aeronautical engineering department at the University of California at Davis, was asked by the board to examine conditions that could have caused Molin to lose control of the plane.
SENSITIVE CONTROLS
Hess found that rudder controls on the A300-600 were much more sensitive than similar systems on other jetliners. As a result, when Molin activated them at 250 knots to correct a worsening sideways motion, he could have unintentionally pushed the plane out of control and snapped the fin.
Hess did not address the key question of whether Molin should have used the rudder, which is normally employed at slower speeds.
American has long contended that Molin sought help from the rudder pedal after getting no response from other flight controls and got more than he bargained for. American has been criticized for its emergency rudder training but the airline says that had nothing to do with the crash.
The safety board said it has drawn no conclusion from Hess’s report. “It’s his opinion. It’s not the board’s opinion at this point,” said NTSB spokesman Ted Lopatkiewicz.
But the findings drew sharp reactions from American and Airbus.
“Molin didn’t make a mistake in using rudder. The outcome was tragic but that was due to design,” said American spokesman Bruce Hicks.
In a letter to the board, Airbus defended the A300-600 and said to compare its flight control system with other models is meaningless. Airbus said Hess took shortcuts and he lacked factual data to support his conclusion on rudder sensitivity.
“It seems to us difficult to make a simple judgment that the flight controls are implicated,” Airbus said.
By: Bmused55 - 9th February 2004 at 10:22
An interesting problem.
[In boxing announcer voice/]
In the Blue corner we have the U.S. investigators.
In the Red Corner we have airbus.
[/end voice]
The US wants the blame put on anything, as long as its notm american. Hardware or personnel.
Airbus wanna blame anything but their design
Who’s right, who’s wrong??
Makes for an interesting debate.
By: steve rowell - 9th February 2004 at 10:15
WASHINGTON — A scientist hired by federal investigators has concluded that the design of an Airbus A300 jet may have contributed to the wild side-to-side motions that tore its tail loose and sent it plunging into a New York City neighborhood in 2001.
The scientists’ report, recently made public with other findings from the investigation, signals that the National Transportation Safety Board (NTSB) is considering whether the jet itself could be partly to blame for the accident that killed 265 people.
The NTSB has not yet concluded what caused American Airlines Flight 587 to crash into Queens shortly after takeoff Nov. 12, 2001. It was the second-worst airline crash in U.S. history. A spokesman for the agency declined to comment on the scientist’s report. Airbus, however, says its data will show that the jet in the accident, the A300-600, was not at fault.
If the NTSB cites the jet’s design in its findings, that could prompt a call for changes in the way the government certifies the design of rudders on all aircraft. It also could affect the legal battle between American and Airbus over which company should pay damages in lawsuits filed by victims’ families.
Investigators have long since concluded that the co-pilot of Flight 587 triggered the accident by repeatedly punching the jet’s rudder back and forth, according to NTSB documents. The rudder is a movable panel at the rear of the jet’s 27-foot-tall tail fin. It swings the nose of the aircraft right or left but is so powerful that it can damage the tail fin if misused.
Several sources familiar with the crash investigation told USA TODAY that an intense debate is underway over the underlying reasons for a pilot to make such severe rudder movements on a routine flight. The NTSB is expected to release its findings this spring.
Some argue that blame lies with the pilot and American’s training program, which taught pilots to use the rudder in an emergency. Pilot groups and American insist that is not true.
But others suspect that the rudder system on the A300-600 — which moves with less pressure from the pilot than any other large jet — was at least partly to blame. Foot pedals on the floor of the cockpit move the rudder.
The scientist hired by the NTSB, Ronald Hess, writes in his report that the Airbus accident is “consistent” with a rare phenomenon in which a pilot essentially loses control of a plane because he or she is tricked by the controls.
Hess is an aeronautical engineering professor at the University of California-Davis. He says that on an A300-600, a pilot could apply more rudder than intended because its pedals are so sensitive, particularly at higher speeds. This could cause the pilot to slam the jet from side to side while intending to straighten it.
A similar situation could occur in a car. A driver who suddenly swerves to avoid debris in the road might overcorrect and skid in the other direction if the steering is difficult to control. That could trigger a series of increasingly larger skids back and forth.
Many other factors have been cited to explain why co-pilot Sten Molin turned the flight into a terrifying ride that fatally damaged the jet.
Another American pilot who had flown with Molin told the NTSB that he believed the co-pilot had used too much rudder on a previous flight.
American taught its pilots to use rudder to help stabilize a jet if they felt it was going out of control. Federal regulators had warned that the training was dangerous, NTSB records show. The records also show that American’s flight simulators also distorted the way a rudder works on a real jet.
The airline says its training was the same as other airlines and had no role in the accident.
In addition, virtually no airline pilots knew before the accident that they could damage a jet by moving the rudder from side to side at such a speed.
Airbus officials, meanwhile, have attacked the theory that their rudder could be flawed.
The European jet manufacturer, which last year delivered more planes than Boeing for the first time, says its data show Molin put far more pressure on the rudder pedals than was needed.
That suggests he would have caused similar extreme motions on any jet model, company officials say. A report filed by French accident investigators, who represent Airbus’ interests in the case, also disputes Hess’ report.
The A300-600 and the A310, a similar model that shares the same rudder, have flown 16 million hours since being introduced in the early 1980s, and “there has never been an issue with rudder pressure,” says Airbus spokesman Clay McConnell.
About 460 of the two models are used around the world. In the USA, only American carries passengers on the jet.
A few minutes before takeoff on Flight 587, co-pilot Molin pushed down on one rudder pedal and then the other, the plane’s data recorder shows. They each moved 4 inches and required 65 pounds of pressure to depress as far as possible.
The rudder performed perfectly in this preflight check. But the check might have given Molin a distorted idea about how the pedals worked at higher speeds.
Just 85 seconds after Flight 587 lifted off, as the jet flew at 290 mph, the pedal moved only 1.3 inches and required half the pressure to swing the rudder as far as possible, according to tests after the accident. This was when Molin began the series of extreme rudder movements that tore the vertical fin off the tail.
Like all rudder pedals on commercial jets, a pilot must push with about 20 pounds before the rudder on the A300-600 moves. Pedals are designed this way so that pilots don’t move the rudder accidentally.
But after the A300-600’s rudder begins to move, it requires far less pressure to swing the rudder an equal distance than on other types of jets. At 290 mph, a pilot who had begun to move the rudder need only add 10 pounds to the pedal to swing the rudder all the way to one side.
By comparison, the similar-sized Boeing 767 requires 63 pounds of additional pressure to move the rudder as far as possible.
By: Bmused55 - 7th February 2004 at 23:40
Originally posted by Thomas Cook
Hi,
From my understanding the NTSB have previously blamed the use of rapid rudder reversal at high speed for the vertical stabilizer detaching from the air frame? Thus meaning that Molin would have been to blame but if AA had trained there crews to use the rudder system more responsibly…?Thanks
Thomas Cook
Molin did exactly has he was taught to. I think AA training is the root of this problem
By: Thomas Cook - 7th February 2004 at 22:57
Hi,
From my understanding the NTSB have previously blamed the use of rapid rudder reversal at high speed for the vertical stabilizer detaching from the air frame? Thus meaning that Molin would have been to blame but if AA had trained there crews to use the rudder system more responsibly…?
Thanks
Thomas Cook
By: wysiwyg - 7th February 2004 at 22:31
The A300’s rudder ratio system does seem to be slightly unusual compared to the way Boeing design theirs however the techniques taught for dealing with upsets by the type training department at American were highly unusual for a big jet and in contradiction to the recommended technique by Airbus.
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February 7, 2004 at 3:45 am