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AMR 587 Airbus Crash (merged)

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AMR 587 Airbus Crash (merged)

Old 29th Oct 2002, 15:29
  #1 (permalink)  
ANOpax
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Post AMR 587 Airbus CVR transcript released

Bloomberg News is reporting the following;

AMR Flight 587 Pilots Didn't Know Tail Came Off Before Crash

Washington, Oct. 29 (Bloomberg) -- The pilots of American
Airlines Flight 587 didn't know their Airbus SAS plane's vertical
tail fin broke off before the aircraft's fatal Nov. 12 crash in a
New York neighborhood, a U.S. board's records show.
Co-pilot Sten Molin, who was flying the AMR Corp. unit's
plane, said "What the hell are we into?'' and "We're stuck in
it'' nine seconds after the fin sheared off, according to a
timeline and cockpit voice recorder transcript released by the
National Transportation Safety Board before a hearing today.
Molin acknowledged wake turbulence from a preceding aircraft
about seven seconds before the plane's rudder made five large
swings. Seven seconds after the rudder movements, the tail fin
sheared off, the NTSB records show. The board is investigating the
possible role of the turbulence in the crash, which killed all 260
people on the plane and five people on the ground.
The Airbus A300-600, headed for the Dominican Republic,
crashed less than two minutes after takeoff from New York's John
F. Kennedy International Airport. The board released evidence
collected in its investigation as the NTSB begins four or five
days of hearings on the second-deadliest U.S. aviation accident.
Less than 30 seconds before his last words, Molin, who was
flying the plane, acknowledged pilot Edward States' comment of
"little wake turbulence, huh.'' Then he said, "Yea, I'm fine''
when States asked, "You all right?'' The final exchange came
during the rudder movements, according to the NTSB timeline.

Rudder Movements

The board is investigating whether Molin initiated rudder
movements as part of a maneuver to escape the wake vortex. The
NTSB in February said the rudder swings and plane's angle may have
created too much force, shearing off the aircraft's tail before it
plunged into a Queens neighborhood.
The NTSB hasn't concluded whether pilot action or a
malfunction caused the rudder movements and won't decide a
probable cause at least until next year. The hearing will focus on
pilot training, the rudder design, jetliner wakes and Federal
Aviation Administration design standards, the board has said.
The rudder is a movable part of the plane's vertical tail fin
that directs the nose of the aircraft left and right. In the seven
seconds after the plane hit a second vortex from the preceding
jetliner, the rudder moved right, then four times in opposite
directions before the tail fin came off.
American since 1996 has trained pilots to use rudders in some
emergencies, such as when planes are in steep angles. The NTSB has
found that many pilots of planes such as the A300-600 didn't know
a small amount of foot-pedal force can cause a large rudder swing.
That finding raises the possibility that Molin intended slight
movements and instead caused wide swings.
 
Old 29th Oct 2002, 15:45
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Swounger
 
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The hearings are available live (Eastern US time) here: www.ntsb.gov.

What's more amazing is that the crew asked for an inspection of the rudder, because something wasn't working correctly in the pre-flight check.

"According to statements taken by the Port Authority of New York and New Jersey 2 , between 0730 and 0800, an American Airlines maintenance crew chief received a radio call from the cockpit of flight 587 reporting that the number two pitch trim and yaw damper would not engage."

http://www.ntsb.gov/Events/2001/AA58...its/240246.pdf see page 3.
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Old 29th Oct 2002, 16:29
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AA has sent pilots for advanced upset training, which uses the rudder quite vigorously...in large jet transports, this is NOT a good idea.

Hope this unfortunate accident was not "pilot induced"...

(Can hear the moans from the APA already... )
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Old 29th Oct 2002, 16:41
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747FOCAL
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I still have problems believing the movement caused all of the tail to come off. I can see the rudder coming off by itself, but not the entire tail. Unless.....there is a real structural flaw that is built into the design of the tail.

I am not trying to start a conspiracy theory debate.
 
Old 29th Oct 2002, 21:57
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Barry's Anorak,

Don't mean to upset you but...

Have "been there, done that" (and still do) with heavy jet transports and the stress caused on the vertical fin with large (too large?) rudder inputs is NOT good....

It seems the lessons learned many years ago have been forgottren by some of the younger guys...one wonders, will they EVER LEARN?
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Old 29th Oct 2002, 23:02
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Longtimelurker
 
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Sorry to agree however i can still rememerber being told not use the rudder in this manner...in the late to mid 70's.In those days all the ground school instructors were old engineers and mechanics.JW
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Old 30th Oct 2002, 03:00
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Angry

I am a current widebody Captain, still in my 30's and holding down a junior management role with my flag carrier employer. Not that that makes me jump up and down with joy, it merely makes me happy that you hear that others are doing really well!
Barry's Anorak... maybe you should choose an outfit which suits you better. Your Your Anorak seems at leat 3 numbers too large. Sorry, but sound very cocky and immatured to me.

I'm in my 30's, too. But I'd take the advise of old grouches like 411A any day.

(Sorry, 411A, didn't mean to be disrespectful )
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Old 30th Oct 2002, 06:32
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Does nothing ever change in internet land? A discussion I have been waiting for serious comment on about a crucial hearing of one of the most bizzare and seriously tragic events in aviation in recent years is hijacked and you guys just want to score points off each other. Just stop a moment and think of your responsibilities in this industry!

Can we please resume the proper thread of discussion?
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Old 30th Oct 2002, 08:54
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Latest Uncommanded rudder upset

American Airlines, A300-605R, Flight 934 from Guyaquil (Ecuador) to Miami, Oct. 28. At 31,000 ft. autopilot kicked off, plane rolled 30 deg into right bank, climbed 1,000 ft and descended 800 ft. before pilots were able to restore control. 3 flight attendants injured.
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Old 30th Oct 2002, 19:39
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In an effort to try to bring this thread back to a technical level, suppose the rudder control went "stupid" and started to travel back and forth, from stop to stop, on it's own. Wouldn't the severe yaw motion that would result cause the engine pylons to fail? My thoughts are that, like most other air disasters, this one resulted from a combination of problems that all met at one single point in time.

1. The tail assembly had some structural damage from either original manufacturing or a subsequent incident.

2. There was a problem in the rudder controls that the mechanics did not find or fix that morning.

3. The PIC used some heavy feet in trying to fly out of wake turbulence.

So a plane with a defective tail structure takes off with a problem with rudder controls. The problem doesn't present itself as a solid problem until the pilot hits the controls hard in an effort to fly out of turbulence. The control problem now presents itself by slapping the rudder from side to side; sort of the opposite of a rudder hard over. This causes (or starts to cause) the engines to seperate. It also causes the original structural defect to fail entirely, seperating the vertical stablizer from the aircraft.

This is all conjecture on my part, but I don't see any other clear cause. I'd love comments by some of the more non-emotional members on this theory.
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Old 30th Oct 2002, 19:51
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Not familiar with Airbus but all other heavy jets have rudder authority limiting.
You cannot put large rudder inputs at speed even if you wanted to.
The limters ( in some cases 2 stage) set the maximum deflection for the speed to reduce the loading on fin and rudder, regardless of the amount of rudder pedal travel.

I would have asumed that Airbus did the same mathmatics
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Old 30th Oct 2002, 20:00
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LA Times

Extracts:

Tuesday's hearings focused attention for the first time on the design of the rudder controls and whether their sensitivity played a role in the accident. Moreover, newly released materials showed that four years ago, Airbus had raised concerns with the NTSB that large rudder movements by pilots could over-stress a tail fin. It is unclear whether the information prompted any action.....

Earlier concerns about the composite material used in place of metal to build the tail fin have been eased, since investigators have been unable to discover any preexisting flaws. But NTSB officials say they are considering recommending more sophisticated inspections of composite components..............

In a 1998 letter from Airbus to the NTSB, which concerned an incident involving another American Airlines A300, the company warned that pilots should not rely on the rudder to recover from in-flight upsets. "Large or abrupt rudder usage ... can lead to rapid loss of controlled flight," Airbus said.

Side-to-side rudder movements "can lead to structural loads that exceed the design strength of the fin," it added. The 1997 incident that prompted the letter did not cause a crash. The NTSB did not warn pilots of the potential danger until February.....
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Old 31st Oct 2002, 01:02
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Now y'all take a moment to read just what rudder inputs would have had to have been.... Huge pedal forces in a sine pattern over more than a few seconds.... Them boys are dead; it's real convenient to park the blame in the cockpit.
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Old 31st Oct 2002, 01:32
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Thoughts on A300-600 rudder travel limiting system:

A very sticky situation for all involved. This wasn't merely a potential design flaw slipping thru the cracks or an unforeseen failure mode but a system that obviously should never have been approved by the regulatory authorities for its obvious undesireable characteristics.

This rudder travel limiting system increases yaw axis sensitivity with increasing indicated airspeed. The faster you fly, the pedal travel is progressively restricted until only about 1 inch of movement is possible (from approx 4" unrestricted). But this 1 inch is equivalent to other types such as the 747 - 767 depressing the pedal all the way to the floor.

If this was a pilot induced situation but hypothetically an aircraft equipped with a ratio changer limiting system, do you feel the pedal would intentionally be pushed to the floor, repetitively?

In addition, the rudder pedal breakout force is very close to the force required to move the rudder pedal 1 inch (full rudder for that airspeed). In other words, the pedals are extremely light at high airspeeds

My experience with the A300-600 indicates the yaw damp and or pitch trim paddle/s not engaging is not an uncommon problem. The instinctive reaction by many when the paddle drops off or does not initially engage and latch (during pre-flight cockpit setup)is to immediately reengage the paddle. This often begins the sequence of trying to engage, won't engage, try again, fails again, etc...call maintenance. When maint. arrives, usually the paddle will engage. Why? If the paddle doesn't initially engage, the FAC (flight augmentation computer)requires approx 5 minutes to accomplish & pass an internal self test or safety check. If the paddle is reengaged before the 5 minute test is complete, the paddle will again drop off and the process (and clock) start all over. If mx arrives 5 minutes later, usually the problem resolves itself.

Also, #2 yaw damp is sort of the back-up yaw damp channel with the #1 directly controlling the rudder.
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Old 31st Oct 2002, 11:32
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A couple of questions.....

(1) Has it been established that the rudder moved to it's limiter controlled maximum deflection, or (perhaps) did it deflect beyond those limits? How many degrees of deflection at 230 Kt with all systems operating normally?

(2) I understand that the vertical stab failed at approximately 195% of design load (I believe FAR part 25 requires a minimum of integrity to 150%). Does anyone know to what values/loads Boeing designs their vertical stabilizers/rudders?


The finger pointing at the dead pilots is repulsive, but not unanticipated. The legal implications are enormous, and if the basic design of the tail is found to be inadequate, the entire Airbus consortium is at risk (it is my understanding that the entire Airbus family have vertical stabs with similar design/material).
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Old 31st Oct 2002, 12:09
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Not the entire Airbus family - older A300's have a tin fin.
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Old 31st Oct 2002, 12:18
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> The finger pointing at the dead pilots is repulsive, but not unanticipated. The legal implications are enormous, and if the basic design of the tail is found to be inadequate, the entire Airbus consortium is at risk (it is my understanding that the entire Airbus family have vertical stabs with similar design/material).<

Caution is urged in being too one sided in defense of one's fellow pilots and assigning of cause to another side.

Of course the issue is neither blame nor liability, but rather one of preventing further accidents by identifying and applying corrective actions.

From what I have gathered, so far, the regulated design standards for *ALL* manufacturers do not provide sufficient margin for what is believed were the actions of this crew.

Either you change the regulations and impact all the worlld's fleets of aircraft or you alter the training by which pilots fly.

I suspect that the majority will select the latter.

My gut feeling is that the FAA/JAA will revisit the margins in the design of aircraft for this type of event in the future designs and that the *ALL* perators will revisit their training syllabus.

I just don't see how the informed public will judge the pilots as the cause and then walk away.
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Old 31st Oct 2002, 12:35
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Guys,

Just a dumb question from somebody ignorant of detailed aircraft systems:

How do the accident investigators know when the tail detached? Could the excessive rudder movements, a fraction of a second later, be the pilot/flight system trying to get a response from the rudder?

Just how can the two events be so conclusively sequenced unless the excessive rudder movements where being executed by the pilot/flight system for a significant amount of time before the breakage. The current view surely assumes that there was no play in the tail before it detached (very sudden!) and that there is some sensor somewhere that can conclusively identify (with other evidence) a very precise time of failure.


Cheers,
Kef.
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Old 31st Oct 2002, 14:10
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Just to clear something up...

It is my understanding that any airliner is certified, at any speed, to take a single, sustained, application of full rudder, and then have that application released. Not good practice of course, but to achieve this rudder limiters are required.

However, a full rudder application made and then held will build up a sideslip angle. What an airliner is not required to withstand is, having established this sideslip angle, for full rudder now to be applied in the opposite direction. This is sufficient to exceed the design strength of the fin / rudder = may snap off.

I further understand this is basically what happened on this occasion. The question is who or what applied the rudder inputS - the pilots (seems pretty unbelievable for perceived "light turbulence"), some "automatic" system (yaw dampers), or the flight control system itself (hydraulic actuators).

NoD
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Old 31st Oct 2002, 20:50
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As I understand things it's now not deemed safe to apply full rudder first one way and then the other... and that this is because the first application yaws the plane so that forces on the fin/rudder are already high when the rudder is reversed.

So what should you do if the initial yaw is caused by sever turbulence? Wouldn't you be tempted to apply full oposite rudder to correct it? This would seem to produce roughly the same forces on the rudder/fin as above.
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