NTSB Recommendation re Airbus Rudder Travel Limits
One of the more interesting aspects of the NTSB’s letter is EASA’s response on pilot training (page 4).
It appears that NTSB, FAA, and EASA are agreed on the need for regulation change and the need to review aircraft for compliance (the actual applicability to individual aircraft types remains open), but apparently only EASA has considered the training issue.
The rudder design requirements are sufficient for the static and the single-input dynamic cases, but insufficient for reversals, particularly for a ‘high geared’ designs. Thus the argument for change rests on the aircraft’s susceptibility to a pilot induced oscillation, triggered by an inappropriate response to an external influence (old style human error).
The case against the A300 has been proven and apparently accepted by Airbus. For the A320 and other aircraft, the NTSB makes the strong inference of similarity, but apparently without conclusive proof.
EASA’s reconsideration of their “position on the pilot training-out as being an efficient and sufficient measure to avoid any new hazardous situation … ” and “that crew use of rudder pedal inputs in upset encounters cannot be ‘trained out’ ” points towards a system change as being the only viable solution for a range of aircraft.
Essentially EASA has changed its view of the pilot’s contribution towards safety in situations involving aircraft with deficient systems, where the pilot through erroneous behaviour, contributes to an accident. This is a major advancement in safety thinking, but could have very wide ranging implications.
Consider the MD-80 take-off configuration warning system. A recent accident involved pilot erroneous behaviour and a weak system (modern regulations already require a more reliable configuration warning system). Arguably problems of configuration warning failure have caused more accidents than the rudder problem in turbulence encounters, thus these systems should also be considered as unacceptable.
This line of thought (the change in the assumed capability of the pilot), could question many other aspects of weak designs which continue in service due to ‘grandfather rights’, or even industry lobbying, e.g. contaminated runway operations FAR vs CS 25.
The next move by the regulatory authorities could be interesting, particularly the FAA who appear to ‘believe’ in training as a solution for many safety aspects.
It appears that NTSB, FAA, and EASA are agreed on the need for regulation change and the need to review aircraft for compliance (the actual applicability to individual aircraft types remains open), but apparently only EASA has considered the training issue.
The rudder design requirements are sufficient for the static and the single-input dynamic cases, but insufficient for reversals, particularly for a ‘high geared’ designs. Thus the argument for change rests on the aircraft’s susceptibility to a pilot induced oscillation, triggered by an inappropriate response to an external influence (old style human error).
The case against the A300 has been proven and apparently accepted by Airbus. For the A320 and other aircraft, the NTSB makes the strong inference of similarity, but apparently without conclusive proof.
EASA’s reconsideration of their “position on the pilot training-out as being an efficient and sufficient measure to avoid any new hazardous situation … ” and “that crew use of rudder pedal inputs in upset encounters cannot be ‘trained out’ ” points towards a system change as being the only viable solution for a range of aircraft.
Essentially EASA has changed its view of the pilot’s contribution towards safety in situations involving aircraft with deficient systems, where the pilot through erroneous behaviour, contributes to an accident. This is a major advancement in safety thinking, but could have very wide ranging implications.
Consider the MD-80 take-off configuration warning system. A recent accident involved pilot erroneous behaviour and a weak system (modern regulations already require a more reliable configuration warning system). Arguably problems of configuration warning failure have caused more accidents than the rudder problem in turbulence encounters, thus these systems should also be considered as unacceptable.
This line of thought (the change in the assumed capability of the pilot), could question many other aspects of weak designs which continue in service due to ‘grandfather rights’, or even industry lobbying, e.g. contaminated runway operations FAR vs CS 25.
The next move by the regulatory authorities could be interesting, particularly the FAA who appear to ‘believe’ in training as a solution for many safety aspects.
P51 Guy
When I was looking at the photos of the failed fin attachments, I had the same feeling the front attachments may have failed first -- definitely a worse case than initial failure at the rear.
Considering the human response, the PF:
I've had two PIO/APC incidents in small a/c known for benign handling. You don't know you're in it until you realise the first correction is an overcorrection. Then you have to gently correct the overcorrection and keep the controls still for a moment. The rudder control system in AA587 did not allow a gentle correction to be made.
Startle factor, now we have something. PTH and I have probably never heard of startle factor. I assume that means something happens you were not expecting and over react. Jumping all over the rudders is not something I would do with startle factor. Maybe my adrenaline would go up but I wouldn't start beating up the airplane because of startle factor. I don't think the AA FO did either. I think the vertical stab separated from the aircraft from the front and the yaw caused a yaw that the gyroscopic forces spit the engines off and the vs finally separated totally. The FDR rudder data was not programmed for a vs coming loose.
Considering the human response, the PF:
- Got a whole bunch more rudder than he wanted
- Attempted a correction
- Again got a whole bunch more rudder than he wanted -- perhaps augmented by front attachment failure.
I've had two PIO/APC incidents in small a/c known for benign handling. You don't know you're in it until you realise the first correction is an overcorrection. Then you have to gently correct the overcorrection and keep the controls still for a moment. The rudder control system in AA587 did not allow a gentle correction to be made.
Thread Starter
RatherBeFlying;
If I may, I would like to ask those reading/contributing: -Other than the AA training program, was there (and is there today) any reason whatsoever to use any rudder at all, ever?
Was this aircraft "upset" or just rolling a bit? I've hit wake turbulence at altitude, (744 1000' above, opposite direction) and it hit us very sharply and hard, (30deg bank approx). I suspect the A340's flight control system used appropriate aileron and that's all.
I'm not second-guessing here, (nor am I saying response should always be left to the AFS, although the NTSB Recommendation did state that, left alone, the Air Canada A320 would have righted itself). - I'm trying to understand the reason for the use of rudder at any time. I understand the reason for the NTSB's Recommendation and agree because of the reasons given, (inability to modulate rudder movement) and I like very much the view expressed by SP above, but still the question lingers...
PJ2
The rudder control system in AA587 did not allow a gentle correction to be made.
Was this aircraft "upset" or just rolling a bit? I've hit wake turbulence at altitude, (744 1000' above, opposite direction) and it hit us very sharply and hard, (30deg bank approx). I suspect the A340's flight control system used appropriate aileron and that's all.
I'm not second-guessing here, (nor am I saying response should always be left to the AFS, although the NTSB Recommendation did state that, left alone, the Air Canada A320 would have righted itself). - I'm trying to understand the reason for the use of rudder at any time. I understand the reason for the NTSB's Recommendation and agree because of the reasons given, (inability to modulate rudder movement) and I like very much the view expressed by SP above, but still the question lingers...
PJ2
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Couldn't remember...
411A,
I couldn't remember, with regard to the USAir accident, and, frankly, I'm too lazy to look it up. :> :> :>
In any event, Airbus came out with an "FCOM Bulletin" after the American accident (FCOM Bulletin 828/1, dated June 2004) that discusses the proper and improper use of the rudder. (I happen to have this in my library....no need to research....:> :> :>)
And, you're right with regard to the misuse of the rudder....Airbus explicitly talks about this in the bulletin.
Someone else in this discussion talks about 'feet on the floor'. I respectfully disagree....the rudder is a flight control and should be used as appropriate when appropriate.
Years ago, when I was on the Boeing, I used to fly with a gentleman (F/O) who insisted on keeping his feet on the rudder pedals throughout the flight, especially during takeoff and landing....feet on the pedals with knees locked. It was difficult for me when I was the flying pilot to manipulate the rudder for centerline tracking during takeoff and landing. (Crosswind landings were a XXXXX when flying with this fellow.) His logic was to 'be there' in case of sudden pilot incapacitation. No counselling of mine convinced him otherwise. A run-in with another captain brought the issue before the chief pilot (training department representative present in the meeting, as well), and the problem was resolved right then and there.
Never flew with the fellow again....don't know for sure what happened to him.
I asked him where he learned this nonsense...he told me, "The U.S. Air Force." I doubted it, since I flew with many guys who were U.S. Air Force trained, and none employed this practice. (I am not U.S. Air Force trained.)
Anyway, good discussion. Enjoying it.....
Fly safe,
PantLoad
I couldn't remember, with regard to the USAir accident, and, frankly, I'm too lazy to look it up. :> :> :>
In any event, Airbus came out with an "FCOM Bulletin" after the American accident (FCOM Bulletin 828/1, dated June 2004) that discusses the proper and improper use of the rudder. (I happen to have this in my library....no need to research....:> :> :>)
And, you're right with regard to the misuse of the rudder....Airbus explicitly talks about this in the bulletin.
Someone else in this discussion talks about 'feet on the floor'. I respectfully disagree....the rudder is a flight control and should be used as appropriate when appropriate.
Years ago, when I was on the Boeing, I used to fly with a gentleman (F/O) who insisted on keeping his feet on the rudder pedals throughout the flight, especially during takeoff and landing....feet on the pedals with knees locked. It was difficult for me when I was the flying pilot to manipulate the rudder for centerline tracking during takeoff and landing. (Crosswind landings were a XXXXX when flying with this fellow.) His logic was to 'be there' in case of sudden pilot incapacitation. No counselling of mine convinced him otherwise. A run-in with another captain brought the issue before the chief pilot (training department representative present in the meeting, as well), and the problem was resolved right then and there.
Never flew with the fellow again....don't know for sure what happened to him.
I asked him where he learned this nonsense...he told me, "The U.S. Air Force." I doubted it, since I flew with many guys who were U.S. Air Force trained, and none employed this practice. (I am not U.S. Air Force trained.)
Anyway, good discussion. Enjoying it.....
Fly safe,
PantLoad
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don't forget dampening dutch roll in swept wing planes via yaw damper...controlling rudder.
also in correcting adverse aileron yaw.
the rudder is a legit flight control and should be used with skill by excellent pilots.
placing the engines on top of each other in the tail would be one way to not have to worry about engine failure yaw.
crosswind landing gear would take care of that aspect of rudder use
but...oh well. now we know...
rudder saved my life when I lost the ailerons on a light GA aircraft...so keep it there! but at least put something in the book about making the darn thing fall apart in the sky.
also in correcting adverse aileron yaw.
the rudder is a legit flight control and should be used with skill by excellent pilots.
placing the engines on top of each other in the tail would be one way to not have to worry about engine failure yaw.
crosswind landing gear would take care of that aspect of rudder use
but...oh well. now we know...
rudder saved my life when I lost the ailerons on a light GA aircraft...so keep it there! but at least put something in the book about making the darn thing fall apart in the sky.
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Crosswind takeoffs and landings, and engine failures. That's about it.
Note that the rudder is automatically used for yaw damping, turn co-ordination (L1011 and others), runway aligment and roll-out (the latter two on many aircraft equipped with an autoland function).
IE: no direct pilot input necessary.
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However, AA purchased A300-600R aircraft, then introduced very poorly thought out upset training, using the powered rudder in a totally inapporopriate way...and had a hull loss, with many dead.
IE: it wasn't the airplane (as other airlines had the type, and still do), it was the totally inept upset training scenario that American Airlines developed...that did the deed.
No doubt about it.
IE: it wasn't the airplane (as other airlines had the type, and still do), it was the totally inept upset training scenario that American Airlines developed...that did the deed.
No doubt about it.
The deadly tango of flight 587 did indeed require two partners - Airbus and American Airlines. The FO and the A300 were merely the shoes of the dancers.
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Really interesting point....
vapilot2004 brings to light a major point....with major airlines in the U.S. (don't know how things work in the rest of the world), everything we do and every way we do it is scrutinized and rubber stamped by the FAA.
Wow, simple, yet brilliant!!!!!!
Thanks vapilot2004!
Fly safe,
PantLoad
Wow, simple, yet brilliant!!!!!!
Thanks vapilot2004!
Fly safe,
PantLoad
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warnings prior to AA587
One key fact was omitted from the above comment - AA's flight training program for the A300 series aircraft was reviewed and approved by Airbus Industries prior to the airline's implementation. There was no contrary guidance issued regarding AA's upset recovery training from the manufacturer until after the accident.
The deadly tango of flight 587 did indeed require two partners - Airbus and American Airlines. The FO and the A300 were merely the shoes of the dancers.
The deadly tango of flight 587 did indeed require two partners - Airbus and American Airlines. The FO and the A300 were merely the shoes of the dancers.
A letter dated Aug. 20, 1997, warned American chief pilot Cecil Ewing that rudders should not be moved abruptly to right a jetliner or when a plane is flown at a sharp angle. The letter was signed by representatives from The Boeing Co., the Federal Aviation Administration and Airbus.
Airbus contends that even people within American Airlines were concerned about how the airline was training its pilots. A letter to Airbus dated May 22, 1997, from American technical pilot David Tribout expressed concern about the airline's then-new training course on advanced maneuvers.
"I am very concerned that one aspect of the course is inaccurate and potentially hazardous," Tribout wrote. His concern: Pilots were being taught that the rudder should be used to control a plane's rolling motion
Paul Railsback, American's managing director of flight operations, testified in an April 8, 2003, deposition that he warned airline executives that someone would be killed some day as a result of the training.
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Due to the recalculation of loads for the Multi Role Transporter
and Tanker (MRTT) aircraft, it has been found that a structural
reinforcement at the aft section of the fuselage (FR (frame) 87-
FR91) is required for A300-600 aircraft and A310 aircraft with a
Trim Tank installed.
* * * * * * *
The unsafe condition is the potential loss of structural integrity
in the aft section of the fuselage between FR87 through FR91,
inclusive, during extreme rolling and vertical maneuver combinations.
We are issuing this AD to require actions to correct the unsafe
condition on these products.
and Tanker (MRTT) aircraft, it has been found that a structural
reinforcement at the aft section of the fuselage (FR (frame) 87-
FR91) is required for A300-600 aircraft and A310 aircraft with a
Trim Tank installed.
* * * * * * *
The unsafe condition is the potential loss of structural integrity
in the aft section of the fuselage between FR87 through FR91,
inclusive, during extreme rolling and vertical maneuver combinations.
We are issuing this AD to require actions to correct the unsafe
condition on these products.
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Re. new AD for A300/310
Quickly reviewed it , doesn't really relate to the issues in this thread, also
not a big issue really, just something that needs to be crossed of the todo list.
not a big issue really, just something that needs to be crossed of the todo list.
Originally Posted by accompanied link
For the reasons discussed above, I certify this AD:
1. Is not a “significant regulatory action” under Executive Order 12866;
2. Is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and
3. Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility
1. Is not a “significant regulatory action” under Executive Order 12866;
2. Is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and
3. Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility
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Paul Railsback, American's managing director of flight operations, testified in an April 8, 2003, deposition that he warned airline executives that someone would be killed some day as a result of the training.
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The letter to which kbrockman refers is at http://www.ntsb.gov/events/2001/aa58...its/239998.pdf
Notice that the signatories specifically warn about events such as occurred 4 years later: "Rudder reversals such as those that might be involved in dynamic maneuvers [sic] created by using too much rudder in a recovery attempt can lead to structural loads that exceed the design strength of the fin and other associated airframe components."
PBL
Notice that the signatories specifically warn about events such as occurred 4 years later: "Rudder reversals such as those that might be involved in dynamic maneuvers [sic] created by using too much rudder in a recovery attempt can lead to structural loads that exceed the design strength of the fin and other associated airframe components."
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these rudder problems and warnings prior to the tragedy only indicate to me that AIRBUS and the regulatory agencies of the world, including the FAA, had the moral responsibility to place a placcard on the instrument panel in full view of the crew, warning them about rudder movements and structural failure.
of course if this happened and reached the press...NO ONE WOULD book a ticket on this type.
of course if this happened and reached the press...NO ONE WOULD book a ticket on this type.
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Originally Posted by Hornet
these rudder problems and warnings prior to the tragedy only indicate to me that AIRBUS and the regulatory agencies of the world, including the FAA, had the moral responsibility to place a placcard on the instrument panel in full view of the crew, warning them about rudder movements and structural failure.
of course if this happened and reached the press...NO ONE WOULD book a ticket on this type.
of course if this happened and reached the press...NO ONE WOULD book a ticket on this type.
What most people keep on focussing on is the lost of the rudder but it wasn't a unique event leading to the crash, there where also the separating engines which is at least indicative of excessive forces put on the entire frame, the extending (weakest) points gave up first , like expected, namely the rudder and the engines.
To be perfectly honest I wouldn't like to be in a repaired airplane (like the rudder was on this frame) in any type from any manufacturer while going to such abuse, changes are that it also will be the last it'll be flying.
Like people said before on this thread, the Copilot also doesn't bear full responsibility for this crash, there is enough blame to spread around, Airbus for what seems to be a halfassed (just within delamination limits) job repairing the rudder and more importantly checking up regulary later on (not unlike what Boeing did to the JAL 747 pressure bulkhead which lead to the fatal crash later), AA for teaching these idiotic recovery techniques, and the FAA fro not reprimanding AA beforehand, they obviously knew about the issue and while they where ultimately the authority that could demand immediate action they failed to do so.
PS sorry for spelling errors, no spell check.
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protectthehornet,
it is hard to make any coherent sense out of your view. All aircraft, not just the A300, have been certified to the same requirement of one-full-movement-and-hold. As became evident after the accident, not least through some good work by the late Michael Dornheim, not all pilots and their management were aware of rudder certification requirements and their limitations.
One could hold the view that at least one knows that the A300 fin is good for almost 30% above ultimate load; for other aircraft one knows it not yet.
There is no point putting a placard when all commercial transport aircraft must have it.
One of the main reasons why rudder reversals were not considered in certification is that no one at the time was able to perform reliable calculations of the aerodynamics involved in such oscillatory dynamic manoeuvres. At least at that time no one saw the point in making certification requirements for which no one would be able to provide reliable evidence of assurance (although one could argue that it's now done with SW routinely).
kbrockman,
It wasn't the rudder, it was the fin.
Something which fails just short of twice design load, 30% more than ultimate load, doesn't count in my book as a poor repair job. It counts in my book as very robust.
PBL
it is hard to make any coherent sense out of your view. All aircraft, not just the A300, have been certified to the same requirement of one-full-movement-and-hold. As became evident after the accident, not least through some good work by the late Michael Dornheim, not all pilots and their management were aware of rudder certification requirements and their limitations.
One could hold the view that at least one knows that the A300 fin is good for almost 30% above ultimate load; for other aircraft one knows it not yet.
There is no point putting a placard when all commercial transport aircraft must have it.
One of the main reasons why rudder reversals were not considered in certification is that no one at the time was able to perform reliable calculations of the aerodynamics involved in such oscillatory dynamic manoeuvres. At least at that time no one saw the point in making certification requirements for which no one would be able to provide reliable evidence of assurance (although one could argue that it's now done with SW routinely).
kbrockman,
Originally Posted by kbrockman
there is enough blame to spread around, Airbus for what seems to be a halfassed (just within delamination limits) job repairing the rudder
Something which fails just short of twice design load, 30% more than ultimate load, doesn't count in my book as a poor repair job. It counts in my book as very robust.
PBL
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Originally Posted by hetfield
@kbrockmann
Did that one crash as well?
Did that one crash as well?
Interestingly this B52 mishap was during testflight on a special stresstest program, pretty much comfirming that too much rudderuse is not a good idea in flight.
The A300 AA just might have made it if it was in level flight , not loosing its engines also during the whole event (or even maybe with one of the 2 left), they just had too many issues going against them and just didn't make it.
There are ample examples of all kind of airplanes loosing control surfaces during all differnt stages of the flight (most in combat situations, just look at all the examples during WWII bombermissions) , some of them made it , many did not.
If you have just enough control surface left, power is available and you happen to be trimmed correctly at levelled flight , you can survive a lot of structural damage, but if you are in a difficult part of the flight (in a turn at or close to MTOW, during heavy turbulence, low to the ground) it just takes away most of your chances of making it out alive.
AA587 was a prime example of just that.