A300Capt
Freight Dawg
Jet\'s design may have caused crash
Jet's design may have caused crash
By Alan Levin, USA TODAY
WASHINGTON — A scientist hired by federal investigators has concluded that
the design of an Airbus 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 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.
Using too much rudder
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 Amer
ican 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.
Out of control on Flight 587
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.
Rudder sensitivity
The Airbus A300-600 jet requires significantly less force
from pilots to move its rudder than other large jets. The higher the value,
the more a rudder moves when a pilot applies equal pressure to foot pedals
on the cockpit floor. A report filed with federal crash investigators says
that the A300-600’s rudder controls may have contributed to a 2001 accident
because it is so sensitive. Airbus officials say the rudder controls had
nothing to do with the accident.
Rudder sensitivity comparisons:
A300-600: 0.93
McDonnell Douglas MD-11: 0.273
Boeing 777: 0.214
Boeing 747: 0.197
Boeing 767: 0.127
Sources: National Transportation Safety Board, University
of California at Davis aeronautical engineering professor Ronald Hess.
Jet's design may have caused crash
By Alan Levin, USA TODAY
WASHINGTON — A scientist hired by federal investigators has concluded that
the design of an Airbus 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 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.
Using too much rudder
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 Amer
ican 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.
Out of control on Flight 587
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.
Rudder sensitivity
The Airbus A300-600 jet requires significantly less force
from pilots to move its rudder than other large jets. The higher the value,
the more a rudder moves when a pilot applies equal pressure to foot pedals
on the cockpit floor. A report filed with federal crash investigators says
that the A300-600’s rudder controls may have contributed to a 2001 accident
because it is so sensitive. Airbus officials say the rudder controls had
nothing to do with the accident.
Rudder sensitivity comparisons:
A300-600: 0.93
McDonnell Douglas MD-11: 0.273
Boeing 777: 0.214
Boeing 747: 0.197
Boeing 767: 0.127
Sources: National Transportation Safety Board, University
of California at Davis aeronautical engineering professor Ronald Hess.