Jet's design may have caused crash

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.
 

jrm1493

New Member
Re: Jet\'s design may have caused crash

I don't think this was the first time that flight controls have brought down an airbus - wasnt a pilot unable to add power while attempting to go-around once because of software (on an A321 maybe)?

Also, shouldn't the vertical tail be built to withstand full rudder deflection at any allowed airspeed? Maybe its not in big planes, but I think it should be able to handle it, even if its not permitted, because you never know what might happen when a pilot freaks out, or slips and jams his foot into a pedal or something. One problem with using composites rather than metals is that you don't get any indication that they are about to break - they don't start cracking and showing signs of fatigue that can be observed, they just break when you overload them.
 

MikeD

Administrator
Staff member
Re: Jet\'s design may have caused crash

An interesting question:

In the latest case in Florida of the young girl caught on film being abducted, NASA was consulted to enhance the video image from the car wash to gain better detail for IDing the kidnapper.

AA587s flight, part or all, was filmed by a security camera at a parking garage. To my knowlege, that film was pretty much dismissed as unusable. Anyone know if NASA worked on image enhancement for that video, and if so what came of it, if not why?
 

PhotoPilot

New Member
Re: Jet\'s design may have caused crash

[ QUOTE ]
Also, shouldn't the vertical tail be built to withstand full rudder deflection at any allowed airspeed? Maybe its not in big planes, but I think it should be able to handle it, even if its not permitted, because you never know what might happen . . .

[/ QUOTE ]

The definition of Va is the maximum speed at which full, abrupt control surface deflections can be made without overstressing an airframe. I've never flown or heard of a modern airplane that didn't have a published Va and it's a speed that every pilot should know for each plane he or she flies. I'm not an aerospace engineer, but I'm guessing that building an aircraft's vertical and horizontal stabilizers and wing surfaces to withstand full deflection at any airspeed would add an unreasonable amount of weight and complexity when compared to the costs of properly training pilots to know and observe their V speeds.

Then again, I'm an inexperienced private pilot, so I could be totally off base . . .
 

pilot602

If specified, this will replace the title that
Re: Jet\'s design may have caused crash

Yup just like the NTSB/FAA - blame the pilot. He was doing what he was trained to do yet somehow he's supposed to "know" not to do that in "X" scenario. WTF.
 

PhotoPilot

New Member
Re: Jet\'s design may have caused crash

That's why I said "properly training pilots." I agree that it's bogus to blame the pilot when he was trained improperly. Blame the training facilities, not the pilot! I didn't mean to imply that the co-pilot didn't know or abide by published V speeds.


Edited to add: Then again, after a second reading, maybe you weren't responding to me . . .
 

E_Dawg

Moderator
Re: Jet\'s design may have caused crash

The idea is that you can do full control movement but the conditions are that it is ONE control ONE time. When you start to put multiple loads on the aircraft either by using more than one control surface or worse, jamming that surface side to side you run a much greater chance of damaging it.
 

MikeD

Administrator
Staff member
Re: Jet\'s design may have caused crash

[ QUOTE ]
The idea is that you can do full control movement but the conditions are that it is ONE control ONE time. When you start to put multiple loads on the aircraft either by using more than one control surface or worse, jamming that surface side to side you run a much greater chance of damaging it.

[/ QUOTE ]

I'm screwed in air-air training.


I know, I know......kidding.
 

Ecl!pse

Well-Known Member
Re: Jet\'s design may have caused crash

We had also discussed this in my mock up US Air 427 Thread in Pro Pilot Corner...but i have a few questions...

1.) If the rudder is deflected one way, wouldnt it corkscrew that way? Cant this be countered by ailerons?

2.) What would cause the tail fin to seperate? Just from the rudder swinging side to side? Did the JAL 747 wake turbulence have anything to do with the seperation?

3.) Also, aside from the tail coming off, didnt they find one of the engines in a gas station parking lot nearby? Would this have come off after ground contact and blew that far?

....a lot of unknowns in this...will be interesting if they ever do find out the true cause
 

Wm226

New Member
Re: Jet\'s design may have caused crash

Very interesting story.

A300Capt, since you fly the A300-600, I am interested to hear your input for this story.

Thank You!
 

pullup

Homewrecker
Re: Jet\'s design may have caused crash

[ QUOTE ]

2.) What would cause the tail fin to seperate? Just from the rudder swinging side to side? Did the JAL 747 wake turbulence have anything to do with the seperation?

[/ QUOTE ]

Probably just the rudder movements. Using back and forth full rudder deflections will stress the material beyond its limits. All the stress will be concentrated at the joints in the tail. I believe (not too sure) that inspection of some other Airbuses did show "half moon" fractures starting at the same spots that this tail failed at. As was said earlier, composites are very different then metal. They are very strong and light but when they break, they break.
 

seagull

Well-Known Member
Re: Jet\'s design may have caused crash

I won't get involved in this except to say that most of the speculation that has been presented here is false.

There is some good stuff on www.pprune.org on this accident, and there are a couple of folks there that actually know what they're talking about.
 

ananoman

New Member
Re: Jet\'s design may have caused crash

[ QUOTE ]
The definition of Va is the maximum speed at which full, abrupt control surface deflections can be made without overstressing an airframe.

[/ QUOTE ]

This is only true in regard to positive limit load factor, it is still possible to damage an aircraft below Va.

[ QUOTE ]
Also, shouldn't the vertical tail be built to withstand full rudder deflection at any allowed airspeed?

[/ QUOTE ]

No, the regulations to certify a transport category aircraft require that the the tail be able to withstand full rudder deflection and then the rudder returned to center. If you cause a full rudder deflection and yaw the aircraft, then use full opposite rudder, it is possible to overstress the tail. You have to get the a copy of the FAR Flight Crew book, it covers the certification rules of transport category aircraft. It is dull reading, but worth knowing.
 

Tired

New Member
Re: Jet\'s design may have caused crash

[ QUOTE ]
The definition of Va is the maximum speed at which full, abrupt control surface deflections can be made without overstressing an airframe.

[/ QUOTE ]

Only in pitch, and only for positive load factors. For example, on one of the aircraft I fly the Va is 250 kts. However, no negative load factor is permitted...this can easily be exceeded even at low speeds.

Stay off the rudder, atleast in the jets I've flown. Even with an inop yam damper I still fly with my feet flat on the floor until just before touchdown.
 
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