AMR 587 Airbus Crash (merged)
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wes_wall:
It's all in the papers. Please read and check.(NTSB)
http://www.ntsb.gov/events/2001/AA58...its/239990.pdf
Regards
It's all in the papers. Please read and check.(NTSB)
http://www.ntsb.gov/events/2001/AA58...its/239990.pdf
Regards
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Huck and Wes :
Aviation Week & Space Technology (Magazine), November 4th edition, pages 47, 50 and 51 "AA587 Hearing: Rudder 'Key' To Solving Mystery."
The article reflects preliminary NTSB findings, discussed at last month's public hearing.
"The hearing proceeded with the implicit assumption that a crewman was moving the rudder, not a system malfunction..."
The article mentions crewmembers' names.
Aviation Week & Space Technology (Magazine), November 4th edition, pages 47, 50 and 51 "AA587 Hearing: Rudder 'Key' To Solving Mystery."
The article reflects preliminary NTSB findings, discussed at last month's public hearing.
"The hearing proceeded with the implicit assumption that a crewman was moving the rudder, not a system malfunction..."
The article mentions crewmembers' names.
ex-Tanker
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Well reading that NTSB report linked above, I get the feeling that there is something else we all have to learn - when to report.
This is hard to write and will cause pain to somebody but I feel it is important.
We are all "nice guys"who don't like to let our mates and colleagues down and I must confess to about four occasions when I should have expressed concerns about a colleague's performance (Captain as well as FO) but didn't.
Maybe I figured that by taking control and having a debrief, I had sorted the problem. I remember that Canberra pilot in the RAF had been let off on numerous occasions by well meaning colleagues and finally produced a fatal accident. The Crossair Avro Captain had also had a history.
The usual comments about not being party to the Airbus incident apply here. It is just another lesson, not a witch hunt.
This is hard to write and will cause pain to somebody but I feel it is important.
We are all "nice guys"who don't like to let our mates and colleagues down and I must confess to about four occasions when I should have expressed concerns about a colleague's performance (Captain as well as FO) but didn't.
Maybe I figured that by taking control and having a debrief, I had sorted the problem. I remember that Canberra pilot in the RAF had been let off on numerous occasions by well meaning colleagues and finally produced a fatal accident. The Crossair Avro Captain had also had a history.
The usual comments about not being party to the Airbus incident apply here. It is just another lesson, not a witch hunt.
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Few Cloudy ex-Tanker
........... Maybe I figured that by taking control and having a debrief, I had sorted the problem. .............
-------------------
All the evidence seems to suggest that the rudder problem with the FO had been sorted out. In subsequent flights with the witness, rudder use was much more restrained. No other pilots seem to have commented on any excessive use of the rudder by the FO. Only very slight rudder movement is visible in the 1st wake encounter in the AA587 FDR reconstruction video, so the rudder was used then with great restraint (or not at all) in the 1st wake encounter.
Incidently the NTSB have not made the FDR data available on-line, but it can be viewed here.
Few Cloudy ex-Tanker
........... Maybe I figured that by taking control and having a debrief, I had sorted the problem. .............
-------------------
All the evidence seems to suggest that the rudder problem with the FO had been sorted out. In subsequent flights with the witness, rudder use was much more restrained. No other pilots seem to have commented on any excessive use of the rudder by the FO. Only very slight rudder movement is visible in the 1st wake encounter in the AA587 FDR reconstruction video, so the rudder was used then with great restraint (or not at all) in the 1st wake encounter.
Incidently the NTSB have not made the FDR data available on-line, but it can be viewed here.
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Capt 104 and Glueball
Thanks for posting the links. The data was posted several other places as well, and I had seen them before. I just wanted to make sure that anyone reading this would have the complete story, and that the remarks would not come across as a sensational headline. No offense intended. Again, thanks.
Thanks for posting the links. The data was posted several other places as well, and I had seen them before. I just wanted to make sure that anyone reading this would have the complete story, and that the remarks would not come across as a sensational headline. No offense intended. Again, thanks.
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Some more impressions of the NTSB AA587 hearings and on-line documents:
(a) There were two related questions which I at first thought was crazy lawyer-talk, but which on thinking about it some more, may amount to a good suggestion. The questions were along the lines “wouldn’t it have been better if the fin had been WEAKER, so that part of the fin would have failed before the main attachments? Shouldn‘t progressive failure be a design principle?”. Sounds crazy, but then I seem to remember incidents where a 707 lost engines in a spin, a 707 lost about 12 feet of wing, and a Concorde lost part of a rudder, all landing safely. Progressive failure as design principle sounds like a good idea. All part of the general principle that we should be less concerned about preventing failures (because they will always happen eventually) than about what happens when there is a failure. I remember a Fire Chief saying “don’t worry about whether there is going to be a fire at your home, worry about when, because it will happen eventually”.
(b) Boeing warns in an on-line document that “Elevators and ailerons are not designed for abrupt reversals from a fully displaced position.”. We have heard a lot about rudder reversals, but maybe abrupt reversals of other controls are not necessarily safe either. They certainly happened with AA587.
(c) The same document says that “The amount of roll that is generated by using the rudder is typically proportional to the amount of sideslip, NOT the amount of rudder deflection.”. So that if you do not know how much of a sideslip you are in (e.g. in a sudden cross-wind), you may be surprised by the a/c response to a rudder input.
(d) The same document also says “It is difficult to perceive sideslip and few modern transport airplanes have true sideslip indicators.” It goes on to point out that “ball” and “slip/skid” indicators are indicators of side-force and not sideslip. So you never do know how much of a sideslip you are in, and hence do not know in advance what the response to the rudder will be.
(e) The same document also says “Because sideslip must build up to generate a roll, there is a time lag between the pilot making a rudder input and the pilot perceiving a roll rate. This lag has caused some pilots to be surprised by the abrupt roll onset and in some cases to interpret the rapid onset of roll as being caused by an outside element not related to their rudder pedal input. If the pilot reacts to this this abrupt roll onset with another large input in the opposite direction, large amplitude oscillations in roll and yaw can result.”.
(f) In the hearing it was said that although right rudder eventually produces a right bank and turn, the first response, possibly not perceived by the pilot, is a slight left roll and right yaw. Presumably these occur during the “delay” period. The turn starts only after the yaw has started.
(a) There were two related questions which I at first thought was crazy lawyer-talk, but which on thinking about it some more, may amount to a good suggestion. The questions were along the lines “wouldn’t it have been better if the fin had been WEAKER, so that part of the fin would have failed before the main attachments? Shouldn‘t progressive failure be a design principle?”. Sounds crazy, but then I seem to remember incidents where a 707 lost engines in a spin, a 707 lost about 12 feet of wing, and a Concorde lost part of a rudder, all landing safely. Progressive failure as design principle sounds like a good idea. All part of the general principle that we should be less concerned about preventing failures (because they will always happen eventually) than about what happens when there is a failure. I remember a Fire Chief saying “don’t worry about whether there is going to be a fire at your home, worry about when, because it will happen eventually”.
(b) Boeing warns in an on-line document that “Elevators and ailerons are not designed for abrupt reversals from a fully displaced position.”. We have heard a lot about rudder reversals, but maybe abrupt reversals of other controls are not necessarily safe either. They certainly happened with AA587.
(c) The same document says that “The amount of roll that is generated by using the rudder is typically proportional to the amount of sideslip, NOT the amount of rudder deflection.”. So that if you do not know how much of a sideslip you are in (e.g. in a sudden cross-wind), you may be surprised by the a/c response to a rudder input.
(d) The same document also says “It is difficult to perceive sideslip and few modern transport airplanes have true sideslip indicators.” It goes on to point out that “ball” and “slip/skid” indicators are indicators of side-force and not sideslip. So you never do know how much of a sideslip you are in, and hence do not know in advance what the response to the rudder will be.
(e) The same document also says “Because sideslip must build up to generate a roll, there is a time lag between the pilot making a rudder input and the pilot perceiving a roll rate. This lag has caused some pilots to be surprised by the abrupt roll onset and in some cases to interpret the rapid onset of roll as being caused by an outside element not related to their rudder pedal input. If the pilot reacts to this this abrupt roll onset with another large input in the opposite direction, large amplitude oscillations in roll and yaw can result.”.
(f) In the hearing it was said that although right rudder eventually produces a right bank and turn, the first response, possibly not perceived by the pilot, is a slight left roll and right yaw. Presumably these occur during the “delay” period. The turn starts only after the yaw has started.
Last edited by PickyPerkins; 12th Nov 2002 at 18:01.
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Picky Perkins,
"...All the evidence seems to suggest that the rudder problem with the FO had been sorted out..."
It evidently hadn't though. This is my point - we come across unusual/unsafe behaviour and hope/think we have sorted it, instead of reporting.
Don't get me wrong, I'm not for going behind someone's back but most of us wait too long before taking things further - myself very much included, I'm afraid.
"...All the evidence seems to suggest that the rudder problem with the FO had been sorted out..."
It evidently hadn't though. This is my point - we come across unusual/unsafe behaviour and hope/think we have sorted it, instead of reporting.
Don't get me wrong, I'm not for going behind someone's back but most of us wait too long before taking things further - myself very much included, I'm afraid.
Union Goon
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Boy go flying for a day or two and miss quite a bit.
Picky Perkins, Thank you, yes the copilots's techniques had been sorted out from the previous incident. It must also be pointed out that the previous incident did not damage the BOEING aircraft. So if Airbus wants to hammer the performance of Sten, which has been their contention all along, then I would simply point out that had they been in a boeing aircraft, all would still be alive today. Again, that points out what I had previously said that in 800+ aircraft fleet, the only planes that have been having this problem are the 35 Airbus A300605Rs. 100s of pilots have flown with Sten since that incident 6 years ago. Not one had anything other than the highest respect for his abilities. This is not pilots circling for the media. This is among American pilots talking to each other. If he was anything other than an exemplary pilot we would be saying so to ourselves atleast.
Few Cloudy. NO one but NO one EVER witnessed poor technique by Sten in ANY other circumstance. Over the 6 years flying out of Kennedy from the previous incident he must have crossed wakes several times. How can you say it wasn't sorted? I know EVERY person that flew with sten on the airbus (there are only 178 total captains in the fleet) and not one person ever said he was the slightest bit ham handed or footed! In fifteen years of flying I have seen plenty of crashes, a few of which we shook are heads and said,"dumb**** had it coming". No one, but no one thinks that this time! That is why the constant outrage from the AA pilots about the Airbus 300-605r continues!
For whatever reason the rudder did reverse several times. However, that did not break the tail off. The final reversals went PAST the rudder load limiter and then the tail failed as can be seen byThis link . Airbus said on the witness stand that the rudder load limiter could be overpowered. Again its a problem with the rudder load limiter design. In a ratio changer system this would be impossible to do AND the rudder would behave the same in all regimes, just like the elevator load limiter does (a similar pull force equals a similar Gloading in all speeds).
Instead the rudder gets exponentially more sensitive the faster you go, AND it is possible to have no limits. Again, this was not documented ANYWHERE in the airbus manuals, yet Airbus consider it to be a "feature" not a design flaw. If it was a feature, don't you think they would mention it?
But it is Airbus's position that they have never made a mistake in designing an aircraft, and now 265 people are dead, and 1 year later I am late for the memorial service for 9 of my friends.
More later
Wino
Picky Perkins, Thank you, yes the copilots's techniques had been sorted out from the previous incident. It must also be pointed out that the previous incident did not damage the BOEING aircraft. So if Airbus wants to hammer the performance of Sten, which has been their contention all along, then I would simply point out that had they been in a boeing aircraft, all would still be alive today. Again, that points out what I had previously said that in 800+ aircraft fleet, the only planes that have been having this problem are the 35 Airbus A300605Rs. 100s of pilots have flown with Sten since that incident 6 years ago. Not one had anything other than the highest respect for his abilities. This is not pilots circling for the media. This is among American pilots talking to each other. If he was anything other than an exemplary pilot we would be saying so to ourselves atleast.
Few Cloudy. NO one but NO one EVER witnessed poor technique by Sten in ANY other circumstance. Over the 6 years flying out of Kennedy from the previous incident he must have crossed wakes several times. How can you say it wasn't sorted? I know EVERY person that flew with sten on the airbus (there are only 178 total captains in the fleet) and not one person ever said he was the slightest bit ham handed or footed! In fifteen years of flying I have seen plenty of crashes, a few of which we shook are heads and said,"dumb**** had it coming". No one, but no one thinks that this time! That is why the constant outrage from the AA pilots about the Airbus 300-605r continues!
For whatever reason the rudder did reverse several times. However, that did not break the tail off. The final reversals went PAST the rudder load limiter and then the tail failed as can be seen byThis link . Airbus said on the witness stand that the rudder load limiter could be overpowered. Again its a problem with the rudder load limiter design. In a ratio changer system this would be impossible to do AND the rudder would behave the same in all regimes, just like the elevator load limiter does (a similar pull force equals a similar Gloading in all speeds).
Instead the rudder gets exponentially more sensitive the faster you go, AND it is possible to have no limits. Again, this was not documented ANYWHERE in the airbus manuals, yet Airbus consider it to be a "feature" not a design flaw. If it was a feature, don't you think they would mention it?
But it is Airbus's position that they have never made a mistake in designing an aircraft, and now 265 people are dead, and 1 year later I am late for the memorial service for 9 of my friends.
More later
Wino
Plastic PPRuNer
Well Wino whenever odd/unexpected/inconsistent/undocumented behaviour in an application or operating system is brought to their attention Micro$oft refer to it as a "feature". The rest of us call it a bug.
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Had a look at the FDR link posted above but I'm no expert...
It looks like something happened during the first encounter that caused the aircraft to exit the enclouner rolling right wing down. After 10 or 12 seconds it's 25 degrees down and during this time the heading changes 15 degrees.
This seems rather a long time without corrective input or is it an attempt to let the plane fly out of the wake zone?
Then at 9:15:50 (one sec before the second encounter) the filtered stab position (not filtered elevator) seem to go down a tad without a corresponding control col input. Could someone explain what this is please?
It looks like something happened during the first encounter that caused the aircraft to exit the enclouner rolling right wing down. After 10 or 12 seconds it's 25 degrees down and during this time the heading changes 15 degrees.
This seems rather a long time without corrective input or is it an attempt to let the plane fly out of the wake zone?
Then at 9:15:50 (one sec before the second encounter) the filtered stab position (not filtered elevator) seem to go down a tad without a corresponding control col input. Could someone explain what this is please?
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=========
cwatters Had a look at the FDR link posted above but I'm no expert... It looks like something happened during the first encounter that caused the aircraft to exit the enclouner rolling right wing down. After 10 or 12 seconds it's 25 degrees down and during this time the heading changes 15 degrees. .............
========
I had to print these FDR traces out before I could read them correctly.
The label of the roll signal says, "Roll Attitude (+sense=right wing down)". The scale at the RHS shows + values plotted DOWNWARDS. Weird but true. So the a/c had its left wing down, not its right.
Note that the heading changes from 220 to near 205 during this period. The heading scale on the RHS is also plotted with inceasing values downward.
The a/c was responding to an ATC request to "587 heavy, turn left ...".
cwatters Had a look at the FDR link posted above but I'm no expert... It looks like something happened during the first encounter that caused the aircraft to exit the enclouner rolling right wing down. After 10 or 12 seconds it's 25 degrees down and during this time the heading changes 15 degrees. .............
========
I had to print these FDR traces out before I could read them correctly.
The label of the roll signal says, "Roll Attitude (+sense=right wing down)". The scale at the RHS shows + values plotted DOWNWARDS. Weird but true. So the a/c had its left wing down, not its right.
Note that the heading changes from 220 to near 205 during this period. The heading scale on the RHS is also plotted with inceasing values downward.
The a/c was responding to an ATC request to "587 heavy, turn left ...".
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Wino, or anyone
I believe someone mentioned this earlier, but I do not recall reading a response. From all the data, prior to take off, the rudder moves both right and left without a corresponding movement by the rudder pedals. Is this normal for the rudder to swing freely without any noticeable movement of the pedals?
I believe someone mentioned this earlier, but I do not recall reading a response. From all the data, prior to take off, the rudder moves both right and left without a corresponding movement by the rudder pedals. Is this normal for the rudder to swing freely without any noticeable movement of the pedals?
Union Goon
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The yawdampener will not move the rudder pedals in normal operations. However in the event of an engine failure, autopilot engaged and slats not up, yaw dampener will provide an extra 5 degrees of travel ontop of the authority of the autopilot rudder channel for a total of 15 degrees of movement.
Normally the yawdampener does what it wants when it wants without moving the pedals. Furthermore it is not subject to limitation by the rudder load limiter. The load limiter strictly blocks rudder pedal travel (though apparently according to airbus at the NTSB hearing it can be overridden by stepping firmly on it, though that is no where in the manual.)
Cwatter
The crew was flying the JFK departure, Bridge climb. They took off on ruway 13L and immediately make a sharp turn to a heading of about 230 degrees to fly to the bridge NDB (about 2 miles from the airport) After crossing over the NDB they are to fly a heading (not track) of 220 degrees, expect radar vectors.... Usually by the time you reach Bridge NDB ATC orders you to pick up a heading of 130 or so...
It looks like they were in the turn when they hit the first wake which served to level the aircraft. They were rolling back into the turn when they hit the second wake further rolling the aircraft in the direction of the turn.
One of those unmarked design "Features" of the A300-605r is that if you roll past 65 degrees of bank all the flight displays go into reset (note it did not happen that we are aware of this time, but has in previous upsets) and go blank for 5 secs. This was found out by a crew that had an upset in the carribean. Needless to say that made recovery much more difficult combined with the unexpected suprise at the time. I would do anything to keep the aircraft from rolling away from me, because without instruments its just that much harder to recover.
Furthermore, before anyone considers Sten heavy footed, look at the reconstruction video I put up in the last post. Now look at the rudder inputs that sten used rolling down the runway. Take a grease pencil and mark your monitor where the limits of the inputs are rolling down the runway. You will see that Sten used no more than 1/3rd or so of the available rudder travel to keep the plane rolling down the runway. When the wake encounter happened, those same inputs are now FULL TRAVEL inputs. There is no way in 40 seconds or so he could adjust to the increased sensitivity, nor could Captain States have known that he was banging off the stops. It would have looked like a moderate input. Also, with the rudder pedal movement stopped at 1.3 inches or so 15 minutes after you just did the control check with 4 inches of travel, and the aircraft not behaving as you expect it to, you might feel you have a jammed control, causing you to step harder. Well unknown to EVERYONE except the airbus engineer, if you step harder you will overpower the rudder load limiter and full travel will now be available to you at high speed. How is that a safe or smart design?
The excuse that things get lost in the manuals in translation is simply inexcusable. The language of aviation is English. If you can't produce a manual in English, you certainly shouldn't be building commercial jets for sale outside of France. The same goes for the airbus engineers at the hearing that everytime a difficult question came up simply said, I don't understand the question. IF they are unable to locate a translator that can translate the question, than how can we be sure they actually met certification standards? That excuse alone ought to cost em all of their certifications.
Cheers
Wino
Normally the yawdampener does what it wants when it wants without moving the pedals. Furthermore it is not subject to limitation by the rudder load limiter. The load limiter strictly blocks rudder pedal travel (though apparently according to airbus at the NTSB hearing it can be overridden by stepping firmly on it, though that is no where in the manual.)
Cwatter
The crew was flying the JFK departure, Bridge climb. They took off on ruway 13L and immediately make a sharp turn to a heading of about 230 degrees to fly to the bridge NDB (about 2 miles from the airport) After crossing over the NDB they are to fly a heading (not track) of 220 degrees, expect radar vectors.... Usually by the time you reach Bridge NDB ATC orders you to pick up a heading of 130 or so...
It looks like they were in the turn when they hit the first wake which served to level the aircraft. They were rolling back into the turn when they hit the second wake further rolling the aircraft in the direction of the turn.
One of those unmarked design "Features" of the A300-605r is that if you roll past 65 degrees of bank all the flight displays go into reset (note it did not happen that we are aware of this time, but has in previous upsets) and go blank for 5 secs. This was found out by a crew that had an upset in the carribean. Needless to say that made recovery much more difficult combined with the unexpected suprise at the time. I would do anything to keep the aircraft from rolling away from me, because without instruments its just that much harder to recover.
Furthermore, before anyone considers Sten heavy footed, look at the reconstruction video I put up in the last post. Now look at the rudder inputs that sten used rolling down the runway. Take a grease pencil and mark your monitor where the limits of the inputs are rolling down the runway. You will see that Sten used no more than 1/3rd or so of the available rudder travel to keep the plane rolling down the runway. When the wake encounter happened, those same inputs are now FULL TRAVEL inputs. There is no way in 40 seconds or so he could adjust to the increased sensitivity, nor could Captain States have known that he was banging off the stops. It would have looked like a moderate input. Also, with the rudder pedal movement stopped at 1.3 inches or so 15 minutes after you just did the control check with 4 inches of travel, and the aircraft not behaving as you expect it to, you might feel you have a jammed control, causing you to step harder. Well unknown to EVERYONE except the airbus engineer, if you step harder you will overpower the rudder load limiter and full travel will now be available to you at high speed. How is that a safe or smart design?
The excuse that things get lost in the manuals in translation is simply inexcusable. The language of aviation is English. If you can't produce a manual in English, you certainly shouldn't be building commercial jets for sale outside of France. The same goes for the airbus engineers at the hearing that everytime a difficult question came up simply said, I don't understand the question. IF they are unable to locate a translator that can translate the question, than how can we be sure they actually met certification standards? That excuse alone ought to cost em all of their certifications.
Cheers
Wino
Last edited by Wino; 12th Nov 2002 at 21:52.
I had an arsehole transplant but the arsehole rejected me, which is why I write such rubbish
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One Year anniversary today
Wino;
Good points all. Lot of grief in New York today along Long Island marking the one year anniversary of the awful crash. Live on TV on a couple of stations out here. Really puts the event into perspective...losses of proportions none of us will ever understand unless we've lost a loved one in similar circumstances. Very Sad !!
Time to stop pointing the finger of blame for now and let these folks grieve for a while. Do you think they really care what caused the crash? All they know is they lost a loved one (S). The lawyers care far more about the cause of the crash which unfortunately is another sad statement of life.
Andy
Good points all. Lot of grief in New York today along Long Island marking the one year anniversary of the awful crash. Live on TV on a couple of stations out here. Really puts the event into perspective...losses of proportions none of us will ever understand unless we've lost a loved one in similar circumstances. Very Sad !!
Time to stop pointing the finger of blame for now and let these folks grieve for a while. Do you think they really care what caused the crash? All they know is they lost a loved one (S). The lawyers care far more about the cause of the crash which unfortunately is another sad statement of life.
Andy
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Question:
Once the rudder breakout force has been exceeded, do the rudder pedals then swing freely through the zero position, or is the breakout force again needed to pass the zero position? Thanks.
Once the rudder breakout force has been exceeded, do the rudder pedals then swing freely through the zero position, or is the breakout force again needed to pass the zero position? Thanks.
Union Goon
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Somewhere in the middle Picky, but you get the momentum of your leg plus all the machinery to overcome breakout again, so basically it goes right through. Since you get a running start at it, it doesn't have a chance to stop you.
Cheers
Wino
Cheers
Wino
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I listened to some of the NTSB hearing via the netcast, and what I heard tended to make me uneasy, if not outright mad. These last two posts frightened me. I hope all who fly this airplane
will take note, and not hide behind macho pride and brand loyalty. There is a bug in the wood pile, and it needs to be found and corrected.
will take note, and not hide behind macho pride and brand loyalty. There is a bug in the wood pile, and it needs to be found and corrected.
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Wino Thanks for the pedal momentum info. If you are busy with a wake encounter in a climbing 25º bank with accelerations on all three axes it must be easy to pass through the zero position the second and third time.
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Wino Airbus said on the witness stand that the rudder load limiter could be overpowered. …….…. rudder gets exponentially more sensitive the faster you go, AND it is possible to have no limits. …..
-----------------
I am curious as to exactly what Airbus said at the hearing about their rudder system. Did they say that the rudder PEDAL limiter could be overpowered, or did they say the RUDDER limiter could be overpowered, or both?
The reason for asking is that so far as I can see, although the AA587 Reconstruction video (Rv) shows that the PEDAL limits were exceeded, it also shows that the RUDDER limits were NOT exceeded.
Here is a frame from the Rv during the second wake encounter. Red lines indicate the limits for the pedals and the rudder. The pedal limit has been overpowered, but the rudder limit has NOT. In fact, so far as I can see, in neither the filtered nor the estimated un-filtered RUDDER positions, in either the Rv or the FDR traces, does the RUDDER go outside the limits. So it might be of interest to look and see exactly what Airbus said according to the NTST hearing transcript (I don‘t have a copy)?
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Wino …. nor could Captain States have known that he was banging off the stops. …
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The witness captain said that the reason that he became aware of aggressive use of the rudder was that he had the habit of keeping his feet on the pedals when he was PNF. How common is this method of checking? Could other Captains have missed something?
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Wino It looks like they were in the turn when they hit the first wake which served to level the aircraft. … They were rolling back into the turn when they hit the second wake further rolling the aircraft in the direction of the turn. ….
--------------
Just being Picky, but I don’t think either of these statements are quite right.
The FDR shows the a/c was climbing with no roll and on a constant heading when it encountered the first wake, though it started to turn left soon afterwards.
The FDR also shows that the a/c had been in a climbing left-hand turn for at least 10 seconds and had changed heading by about 15 degrees when it encountered the second wake, .The (filtered) bank angle decreased as soon at the a/c hit the wake.
So the a/c hit the first wake wings level, but it was in a climbing 25º left-hand bank when it hit the second wake.
Maybe just details, but also, maybe, it might turn out to be a significant difference.
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Wino Airbus said on the witness stand that the rudder load limiter could be overpowered. …….…. rudder gets exponentially more sensitive the faster you go, AND it is possible to have no limits. …..
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I am curious as to exactly what Airbus said at the hearing about their rudder system. Did they say that the rudder PEDAL limiter could be overpowered, or did they say the RUDDER limiter could be overpowered, or both?
The reason for asking is that so far as I can see, although the AA587 Reconstruction video (Rv) shows that the PEDAL limits were exceeded, it also shows that the RUDDER limits were NOT exceeded.
Here is a frame from the Rv during the second wake encounter. Red lines indicate the limits for the pedals and the rudder. The pedal limit has been overpowered, but the rudder limit has NOT. In fact, so far as I can see, in neither the filtered nor the estimated un-filtered RUDDER positions, in either the Rv or the FDR traces, does the RUDDER go outside the limits. So it might be of interest to look and see exactly what Airbus said according to the NTST hearing transcript (I don‘t have a copy)?
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Wino …. nor could Captain States have known that he was banging off the stops. …
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The witness captain said that the reason that he became aware of aggressive use of the rudder was that he had the habit of keeping his feet on the pedals when he was PNF. How common is this method of checking? Could other Captains have missed something?
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Wino It looks like they were in the turn when they hit the first wake which served to level the aircraft. … They were rolling back into the turn when they hit the second wake further rolling the aircraft in the direction of the turn. ….
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Just being Picky, but I don’t think either of these statements are quite right.
The FDR shows the a/c was climbing with no roll and on a constant heading when it encountered the first wake, though it started to turn left soon afterwards.
The FDR also shows that the a/c had been in a climbing left-hand turn for at least 10 seconds and had changed heading by about 15 degrees when it encountered the second wake, .The (filtered) bank angle decreased as soon at the a/c hit the wake.
So the a/c hit the first wake wings level, but it was in a climbing 25º left-hand bank when it hit the second wake.
Maybe just details, but also, maybe, it might turn out to be a significant difference.
Last edited by PickyPerkins; 19th May 2003 at 23:16.
Rudder Pedal Needs Gas Struts
Given that the rudder pedal breakout force is close to that required for full deflection (all of 1.3 inches
) at the accident airspeed, my stone axe engineering approach would be to install a gas strut on the rudder pedals which would allow an even modulation of force. Obviously the strut would offer a resistance somewhat greater than the breakout force. Some serious engineering will be required to effectively modulate over a 1.3" stroke.
And how will the longer stroke in the low speed case be handled?
Wino, you may want to discuss further with the folks at The Aussie Gas Strut Company as they offer custom engineering in low quantities.
) at the accident airspeed, my stone axe engineering approach would be to install a gas strut on the rudder pedals which would allow an even modulation of force. Obviously the strut would offer a resistance somewhat greater than the breakout force. Some serious engineering will be required to effectively modulate over a 1.3" stroke.And how will the longer stroke in the low speed case be handled?
Wino, you may want to discuss further with the folks at The Aussie Gas Strut Company as they offer custom engineering in low quantities.