AMR 587 Airbus Crash (merged)
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from a PM
Why wouldn't this problem afflict every airplane model? What is it about the A300-600 that makes it
different? Good question. Let’s see now:
1. Static Port placement? (and mayhap one that sucks in water flow-by when the atmospheric pressure is varying –
see *more below on this)
2. Early design that didn’t accommodate any real safeguards against a feedback loop in the FCS
3. Deficient safeguards for aircraft washing?
4. Airborne airflow patterns that allow rainwater to be entrained into static ports (or melting ice on the airframe to flow down/along and to be sucked in)
5. A CADC design that has sampling rates so high that you could say it was “hair-triggered” and over-responsive)
6. Designed-in low points in the static lines that allow water to pool and completely (rather than partially) obstruct the static lines (and so maximizing the hydro-pneumatic damping of air pressure sensing under rapid yaw.)
7. Insufficiently frequent specified water-trap draining intervals – i.e. allowing the water to accumulate.
8. Servicing manual deficiencies that don’t specify the water traps to be checked/drained after aircraft washes.
* My first experience with the ability of static ports to take in water was a long time ago. Imagine a rubber
bung that’s concentrically hollow to allow the static system to accommodate atmospheric pressure changes while
parked (and so allow air-fed flight instruments to “breathe” properly). Even though the bung is designedly
inserted upwards so that the hole faces downwards, water flowing down over it (in torrential rain) whilst parked
can still get sucked up that hollow rubber tube by capillary action. We proved that after a nasty mass incident
back in 1974 (or thereabouts). So you can get trapped water in the lines. In the case referred to here there was
no static port or line heating and that trapped water froze causing all pneumatic flight instruments to be lost
during a climb above freezing level. Not really applicable to AA587 but water in the lines can still have an
effect as outlined in the theory.
Explanation: “and so allow flight instruments to “breathe” properly” Pneumatic instruments can be destroyed (or
at least require removal and recalibration) if subjected to large pressure transients (like blowing orally into
a static port or obstructing a tube and removing a solid bung in a much changed atmospheric pressure days later
etc.) They are best left not 100% sealed in other words).
different? Good question. Let’s see now:
1. Static Port placement? (and mayhap one that sucks in water flow-by when the atmospheric pressure is varying –
see *more below on this)
2. Early design that didn’t accommodate any real safeguards against a feedback loop in the FCS
3. Deficient safeguards for aircraft washing?
4. Airborne airflow patterns that allow rainwater to be entrained into static ports (or melting ice on the airframe to flow down/along and to be sucked in)
5. A CADC design that has sampling rates so high that you could say it was “hair-triggered” and over-responsive)
6. Designed-in low points in the static lines that allow water to pool and completely (rather than partially) obstruct the static lines (and so maximizing the hydro-pneumatic damping of air pressure sensing under rapid yaw.)
7. Insufficiently frequent specified water-trap draining intervals – i.e. allowing the water to accumulate.
8. Servicing manual deficiencies that don’t specify the water traps to be checked/drained after aircraft washes.
* My first experience with the ability of static ports to take in water was a long time ago. Imagine a rubber
bung that’s concentrically hollow to allow the static system to accommodate atmospheric pressure changes while
parked (and so allow air-fed flight instruments to “breathe” properly). Even though the bung is designedly
inserted upwards so that the hole faces downwards, water flowing down over it (in torrential rain) whilst parked
can still get sucked up that hollow rubber tube by capillary action. We proved that after a nasty mass incident
back in 1974 (or thereabouts). So you can get trapped water in the lines. In the case referred to here there was
no static port or line heating and that trapped water froze causing all pneumatic flight instruments to be lost
during a climb above freezing level. Not really applicable to AA587 but water in the lines can still have an
effect as outlined in the theory.
Explanation: “and so allow flight instruments to “breathe” properly” Pneumatic instruments can be destroyed (or
at least require removal and recalibration) if subjected to large pressure transients (like blowing orally into
a static port or obstructing a tube and removing a solid bung in a much changed atmospheric pressure days later
etc.) They are best left not 100% sealed in other words).
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What's Confusing You?
DownIn3Green
It seems pretty clear (to me) that Overtalk is referring to the possibility that accumulated water trapped in the static lines could induce the air data computer to feed faulty airspeed signals to either/both the yaw damper and rudder limiter via the Flight Augmentation Computer. Water in the static lines would dampen the ADC inputs considerably and create the potential for an out-of-phase condition to develop (particularly following on from the yaw caused by the externally applied gross stimulus of a wake encounter).. Closed loop feedback is the most likely cause of this accident - despite all the obfuscation by Airbus, the FAA and NTSB about pilot inputs. Overtalk is admitting that there may have been belated pilot intervention attempts that may not have helped (and may indeed have exacerbated the condition). That is quite different to a pilot-input inspired event.
Unlike roll and pitch, the problem in the yaw circuit is that the very large vertical fin is going to provide a powerful stabilizing force - but that can be subverted by mis-timed FAC signals to the rudder (as caused by faulty feeds from the ADC). In my view the theory is credible and might explain the A300's tail-wagging proclivities. For AA587 it was likely to have been a case of an unfortunate conjunction of a wake encounter, water in the static lines and a PF who was hand-flying and tried his best to calm the beast that was suddenly unleashed by the wake encounter.
It seems pretty clear (to me) that Overtalk is referring to the possibility that accumulated water trapped in the static lines could induce the air data computer to feed faulty airspeed signals to either/both the yaw damper and rudder limiter via the Flight Augmentation Computer. Water in the static lines would dampen the ADC inputs considerably and create the potential for an out-of-phase condition to develop (particularly following on from the yaw caused by the externally applied gross stimulus of a wake encounter).. Closed loop feedback is the most likely cause of this accident - despite all the obfuscation by Airbus, the FAA and NTSB about pilot inputs. Overtalk is admitting that there may have been belated pilot intervention attempts that may not have helped (and may indeed have exacerbated the condition). That is quite different to a pilot-input inspired event.
Unlike roll and pitch, the problem in the yaw circuit is that the very large vertical fin is going to provide a powerful stabilizing force - but that can be subverted by mis-timed FAC signals to the rudder (as caused by faulty feeds from the ADC). In my view the theory is credible and might explain the A300's tail-wagging proclivities. For AA587 it was likely to have been a case of an unfortunate conjunction of a wake encounter, water in the static lines and a PF who was hand-flying and tried his best to calm the beast that was suddenly unleashed by the wake encounter.
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While Overtalk and I both agree to what is the most likely_"late event" in the causal chain (a divergent rudder oscillation caused by a control loop with negative dynamic stability), I believe we diverge in our opinions as we progress backwards in the causal chain to what may have been the cause of this divergent oscillation of the control loop.
Overtalk favors the Air Data Computer inputs to the Flight Augmentation Computer, whereas I believe it was induced by hi-frequency pulsing in the hydraulic system. The reason I can't "stretch" to Overtalk's theory is because the characteristics of air data are well-known in the flight control world, and have been since even before the advent of digital computers as flight control system controllers. I think the entire community of flight control engineers would be aghast if we were to find out that Airbus did not filter out hi-frequency, oscillatory effects from the air data inputs to the control laws. It is THE FIRST consideration you make once you decide to use an airspeed parameter in your control loop computation.
The most typical, and easy, solution is a simple low-pass filter, so named because it only allows the LOW frequencies to pass thru to affect the control law. Low pass filters are typically characterized by a "break frequency", which is the design point at which inputs at that frequency begin to be attenuated (rejected). [Low Pass Filters are even discussed in the CVR analysis in the accident factuals.]__For airspeed inputs, the filter break frequency_is usually somewhere around the 8-10 Hz range. Any oscillation in the digital airspeed signal higher than this frequency is filtered, and will never drive the control law, for the specific reasoning of avoiding divergent oscillation caused by excessive phase lag. Such filtering is inherent to ALL flight control system designs that use airspeed programming in the control laws, and this is why hi-freq oscillations in airspeed do not plague the worldwide fleet. It would be a VERY regular occurrence (on Airbus as well as other airplanes) if such filtering did not exist....and yes, water in the lines would exacerbate such oscillations.
It would be even easier than performing a flight test to see if Overtalk's theory holds water (pardon the pun). If Airbus would simply reveal their design specifics of the FAC control laws with respect to airspeed inputs to the rudder control law, any one of a multitude of controls engineers could easily perform a frequency domain analysis, and tell you if there was any potential for oscillating airspeed signals to get into the closed-loop control law.
The other issue I have in accepting this theory is lack of abundant "smoking gun" evidence. Yes, we have a_fair amount_of tail wagging events in the Airbus history file. However, one cannot assume that this is all due to faulty air data processing without some hard evidence that points in that direction (it could just as easily point to my theory). However, this is where I believe my theory (rudder hydraulic_de-synchronization)_shows ample smoking-gun evidence:
1) The existing AD on de-synchronization is the biggest smoking gun! But it goes deeper:
2) The FedEx hangar event (with airspeed=0) was a clear rudder oscillation that lead to mechanical failure. The test being performed was, indeed, the test required to attempt to detect the de-synchronization problem. I'd say_they found it!
3) The AA587 subject airplane had a history of rudder system related write-ups.
4) The subject airplane had a FAC preflight test failure right before the doomed flight. It is my understanding that this pre-flight test specifically seeks to verify proper operation of_the rudder servo control loop.
But again, even my theory could be dispelled by Airbus coming clean on their design details. To dispel Overtalk's theory, one only needs to know the control law filtering specifics on airpseed signals coming from the ADC to the FAC. To dispel my theory, one only needs to see actuator system frequency response test data, both under normal conditions, and under the conditions described as "de-synchronization".
In the past, I have amply described how the word "synchronization" is a direct reference to a closed-loop control system's amount of phase lag.
So...there's my summary! Nothing personal....just a difference of technical opinions. :-)
Overtalk favors the Air Data Computer inputs to the Flight Augmentation Computer, whereas I believe it was induced by hi-frequency pulsing in the hydraulic system. The reason I can't "stretch" to Overtalk's theory is because the characteristics of air data are well-known in the flight control world, and have been since even before the advent of digital computers as flight control system controllers. I think the entire community of flight control engineers would be aghast if we were to find out that Airbus did not filter out hi-frequency, oscillatory effects from the air data inputs to the control laws. It is THE FIRST consideration you make once you decide to use an airspeed parameter in your control loop computation.
The most typical, and easy, solution is a simple low-pass filter, so named because it only allows the LOW frequencies to pass thru to affect the control law. Low pass filters are typically characterized by a "break frequency", which is the design point at which inputs at that frequency begin to be attenuated (rejected). [Low Pass Filters are even discussed in the CVR analysis in the accident factuals.]__For airspeed inputs, the filter break frequency_is usually somewhere around the 8-10 Hz range. Any oscillation in the digital airspeed signal higher than this frequency is filtered, and will never drive the control law, for the specific reasoning of avoiding divergent oscillation caused by excessive phase lag. Such filtering is inherent to ALL flight control system designs that use airspeed programming in the control laws, and this is why hi-freq oscillations in airspeed do not plague the worldwide fleet. It would be a VERY regular occurrence (on Airbus as well as other airplanes) if such filtering did not exist....and yes, water in the lines would exacerbate such oscillations.
It would be even easier than performing a flight test to see if Overtalk's theory holds water (pardon the pun). If Airbus would simply reveal their design specifics of the FAC control laws with respect to airspeed inputs to the rudder control law, any one of a multitude of controls engineers could easily perform a frequency domain analysis, and tell you if there was any potential for oscillating airspeed signals to get into the closed-loop control law.
The other issue I have in accepting this theory is lack of abundant "smoking gun" evidence. Yes, we have a_fair amount_of tail wagging events in the Airbus history file. However, one cannot assume that this is all due to faulty air data processing without some hard evidence that points in that direction (it could just as easily point to my theory). However, this is where I believe my theory (rudder hydraulic_de-synchronization)_shows ample smoking-gun evidence:
1) The existing AD on de-synchronization is the biggest smoking gun! But it goes deeper:
2) The FedEx hangar event (with airspeed=0) was a clear rudder oscillation that lead to mechanical failure. The test being performed was, indeed, the test required to attempt to detect the de-synchronization problem. I'd say_they found it!
3) The AA587 subject airplane had a history of rudder system related write-ups.
4) The subject airplane had a FAC preflight test failure right before the doomed flight. It is my understanding that this pre-flight test specifically seeks to verify proper operation of_the rudder servo control loop.
But again, even my theory could be dispelled by Airbus coming clean on their design details. To dispel Overtalk's theory, one only needs to know the control law filtering specifics on airpseed signals coming from the ADC to the FAC. To dispel my theory, one only needs to see actuator system frequency response test data, both under normal conditions, and under the conditions described as "de-synchronization".
In the past, I have amply described how the word "synchronization" is a direct reference to a closed-loop control system's amount of phase lag.
So...there's my summary! Nothing personal....just a difference of technical opinions. :-)
Belgique: Does the expression "control law" apply to the older technology Airbus 300/310 rudder systems as much it does to the fly-by-wire A-320/330--- systems?
I have no engineering training but find the comments on this topic quite interesting, and wish I could better understand some of the complexities without a graphic flow chart in a flight manual. In my company's flight ops magazine, the Internet and in "Aviation Week & ST" magazines, the words "control law" seem to be used only in connection with the A-319/320 etc, but never with the 757/767 generation.
I have no engineering training but find the comments on this topic quite interesting, and wish I could better understand some of the complexities without a graphic flow chart in a flight manual. In my company's flight ops magazine, the Internet and in "Aviation Week & ST" magazines, the words "control law" seem to be used only in connection with the A-319/320 etc, but never with the 757/767 generation.
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Control Laws
Ignition Override
Any time that you have digital data feeds inputting into a flight control system (yaw damper) you must have "control laws". These accommodate (and/or negate) the type of dangerous feedback loops described by OVERTALK.
It is almost unthinkable (but not unbelievable) that in an early design, such as the A300, an unforeseen anomaly may have been allowed to creep into the system. But then again, would they have been testing for an unlikely "sometime" occurrence (such as an accumulation of water in the static lines) to create a feedback loop - and only once excitated by an external influence (such as a wake encounter). But it cannot be ruled out - basically on the grounds that I doubt that Airbus would have watered the prototype's static lines and tested for it. They'd have needed to go seek out an external excitation (such as a wake encounter, stall or similar upset) whilst having a significant amount of water trapped in the lines. See my point there?
Neither can the possibility of hydraulic feedback loops be ruled out. Both possibilities are far more likely to have caused the AA587 accident than a pilot pedalling into a destructive yaw cycle. It's just that the non-aerodynamic FEDEX hangar incident points more to the actuator having broken because of a straight hydraulic anomaly.
B
Any time that you have digital data feeds inputting into a flight control system (yaw damper) you must have "control laws". These accommodate (and/or negate) the type of dangerous feedback loops described by OVERTALK.
It is almost unthinkable (but not unbelievable) that in an early design, such as the A300, an unforeseen anomaly may have been allowed to creep into the system. But then again, would they have been testing for an unlikely "sometime" occurrence (such as an accumulation of water in the static lines) to create a feedback loop - and only once excitated by an external influence (such as a wake encounter). But it cannot be ruled out - basically on the grounds that I doubt that Airbus would have watered the prototype's static lines and tested for it. They'd have needed to go seek out an external excitation (such as a wake encounter, stall or similar upset) whilst having a significant amount of water trapped in the lines. See my point there?
Neither can the possibility of hydraulic feedback loops be ruled out. Both possibilities are far more likely to have caused the AA587 accident than a pilot pedalling into a destructive yaw cycle. It's just that the non-aerodynamic FEDEX hangar incident points more to the actuator having broken because of a straight hydraulic anomaly.
B
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unlikely occurrence?
Belgique says:
"But then again, would they have been testing for an unlikely "sometime" occurrence (such as an accumulation of water in the static lines)"
Rather than "unlikely" I might have said "unanticipated". Probably no manufacturers would water a static line and go out and flight- test for such a condition. However in my experience some aircraft are more likely than others to draw water into their static lines. It would be interesting to know:
a. How much they normally find in an A300 (and whether recods are kept)
b. Whether they check it after an aircraft wash (most companies wouldn't, they'd just trust that taping over the ports would ensure that no water got in).
c. Whether water can accumulate inflight (due to flight through heavy precipitation - or be drawn in on descent as airframe icing melts.
d. What parameters American Airlines use for mandatorily chucking the bungs in (overnight parking only - or at all other times?)
I think I'm right in saying that low points are normally provided as water traps (with drains fitted) at some point before the port and starboard static lines are Y'd (or T'd) together. Water accumulating in those low points MUST affect the air pressure being sensed by the transducers further downstream in the lines (or at the CADC itself) - particularly during rapid yawing, when the water flows would be in opposite directions on the port and stbd sides..
I'll leave it up to your imagination as to what effect this hydro-pneumatic damping might have upon the static pressures being sensed at the CADC (and more importantly what effect a pulsing pressure [that's usually fairly constant] might have upon the airspeed outputs being provided to other aircraft systems - including most importantly the yaw damper). This is where "sampling rates" start to confuse the issue and you'd really need to go out and conduct experiments to get to a bottom line.
"But then again, would they have been testing for an unlikely "sometime" occurrence (such as an accumulation of water in the static lines)"
Rather than "unlikely" I might have said "unanticipated". Probably no manufacturers would water a static line and go out and flight- test for such a condition. However in my experience some aircraft are more likely than others to draw water into their static lines. It would be interesting to know:
a. How much they normally find in an A300 (and whether recods are kept)
b. Whether they check it after an aircraft wash (most companies wouldn't, they'd just trust that taping over the ports would ensure that no water got in).
c. Whether water can accumulate inflight (due to flight through heavy precipitation - or be drawn in on descent as airframe icing melts.
d. What parameters American Airlines use for mandatorily chucking the bungs in (overnight parking only - or at all other times?)
I think I'm right in saying that low points are normally provided as water traps (with drains fitted) at some point before the port and starboard static lines are Y'd (or T'd) together. Water accumulating in those low points MUST affect the air pressure being sensed by the transducers further downstream in the lines (or at the CADC itself) - particularly during rapid yawing, when the water flows would be in opposite directions on the port and stbd sides..
I'll leave it up to your imagination as to what effect this hydro-pneumatic damping might have upon the static pressures being sensed at the CADC (and more importantly what effect a pulsing pressure [that's usually fairly constant] might have upon the airspeed outputs being provided to other aircraft systems - including most importantly the yaw damper). This is where "sampling rates" start to confuse the issue and you'd really need to go out and conduct experiments to get to a bottom line.
Swounger
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The National Transportation Safety Board today
released the following update on its investigation of the
November 12, 2001, crash of American Airlines flight 587, an
Airbus A300-600, in Belle Harbor, New York, which resulted
in the deaths of all 260 persons aboard and 5 persons on the
ground.
Composite Lug Test
On August 13, 2003, the NTSB conducted a lug sub-
component structural test at the Airbus test facility in
Hamburg, Germany. Engineers from the NTSB, Airbus, American
Airlines, BEA, and the NASA Langley Research Center
supported the testing and analysis.
The test component was a rear main attachment lug from
an A310-300 Carbon Fiber Reinforced Plastics (CFRP) fin box
skin panel. The panel was originally constructed as a
manufacturing quality test article and was used to
demonstrate the interior quality of the skin panel.
The test was to demonstrate the behavior of the lug
under a load condition similar to that experienced by
American Airlines 587 during the accident flight. The load
condition used was derived from the flight data recorder
information and the subsequent structural finite element
analyses.
During the test, the lug structurally failed at a load
beyond its design ultimate limit. The test failure appeared
to be consistent with calculated failure load analyses
performed by both Airbus and NASA Langley. Work is
continuing at the Safety Board to continue refining a
reliable estimate of the loads on the AA587 fin during the
accident.
The Safety Board has obtained two other lugs for
testing. Two rear lugs were removed from the tail fin from
the A-300-600 aircraft that was involved in a loss-of-
control incident in 1997 as American Airlines flight 903
(see Fifth Update, February 25, 2002). These lugs will
undergo structural tests in December of this year and
February 2004 in Hamburg.
www.ntsb.gov
released the following update on its investigation of the
November 12, 2001, crash of American Airlines flight 587, an
Airbus A300-600, in Belle Harbor, New York, which resulted
in the deaths of all 260 persons aboard and 5 persons on the
ground.
Composite Lug Test
On August 13, 2003, the NTSB conducted a lug sub-
component structural test at the Airbus test facility in
Hamburg, Germany. Engineers from the NTSB, Airbus, American
Airlines, BEA, and the NASA Langley Research Center
supported the testing and analysis.
The test component was a rear main attachment lug from
an A310-300 Carbon Fiber Reinforced Plastics (CFRP) fin box
skin panel. The panel was originally constructed as a
manufacturing quality test article and was used to
demonstrate the interior quality of the skin panel.
The test was to demonstrate the behavior of the lug
under a load condition similar to that experienced by
American Airlines 587 during the accident flight. The load
condition used was derived from the flight data recorder
information and the subsequent structural finite element
analyses.
During the test, the lug structurally failed at a load
beyond its design ultimate limit. The test failure appeared
to be consistent with calculated failure load analyses
performed by both Airbus and NASA Langley. Work is
continuing at the Safety Board to continue refining a
reliable estimate of the loads on the AA587 fin during the
accident.
The Safety Board has obtained two other lugs for
testing. Two rear lugs were removed from the tail fin from
the A-300-600 aircraft that was involved in a loss-of-
control incident in 1997 as American Airlines flight 903
(see Fifth Update, February 25, 2002). These lugs will
undergo structural tests in December of this year and
February 2004 in Hamburg.
www.ntsb.gov
AA's Submission to the NTSB -- Excerpt
AA's Full Submission
The "best" part is that full available rudder deflection force and pedal travel decreases from 65 pounds and 4 inches at takeoff speed to 32 pounds (over a breakout force of 22 pounds) and 1.2 inches at the accident speed.
Also of note is that no pilot in the static tests was able to modulate rudder at 250 kt. It was either maximum available deflection or nothing
Here we see rudder being called upon to bring bank back under control after full right wheel input was found insufficient to counter the wake induced roll. I'd find it personally difficult to stay off the rudder with the bank going past 25 degrees, especially in a transport a/c. Is the pilot better off throttling back an engine 
Looks perhaps like he should on this a/c type
Pssst Shadow -- What's with the pic of Tafari Makonnen?
PROBABLE CAUSE AND CONTRIBUTING FACTORS
The probable cause of this accident was the onset of a design-induced, adverse aircraft pilot coupling (APC) event that led to rapid development of excessively high aerodynamic lateral loads resulting in the catastrophic structural failure of the vertical stabilizer and rudder in only six and one-half seconds.
The event was triggered by an unexpectedly sensitive response of the rudder to an initial, single pedal input by the pilot during a wake vortex encounter. Due to the unique characteristics in the aircraft's flight control system design, the pilot became caught in an adverse APC/pilot involved oscillation mode as he attempted to counter the effects of that input. Specifically, after making a control wheel input followed by a rudder input intended to achieve a desired aircraft response, the over-sensitivity of the rudder control system induced the pilot to make additional, essentially cyclic, corrective rudder inputs as he attempted to stabilize the aircraft. Unknown to the pilot, because of the sensitivity of the rudder controls and the powerful nature of the hydraulically driven rudder actuators, these corrective inputs rapidly generated rupture loads. The rudder travel limiter unit (RTLU) and yaw damper failed to protect against the build up of these loads due to deficiencies in the flight control architecture design.
Contributing factors to the accident included:
1. The manufacturer's failure to disclose information learned from prior in-service high-load events demonstrating the adverse APC characteristics of the A300-600 flight control system and the resulting risk of structural overload;
2. Extraordinary rudder sensitivity at increased airspeeds due to a high rudder pedal breakout force relative to the shallow (low) rudder pedal force gradient and a corresponding reduction in rudder pedal travel that makes the A300-600 uniquely susceptible to adverse APC/pilot involved oscillation;
3. The rudder travel limiter unit's inability to protect the aircraft from excessive lateral loads;
4. The inability of the yaw damper, when the rudder pedal is held at the stop, to damp out motions resulting from the adverse APC/pilot involved oscillation tendencies of the aircraft;
5. Industry-wide lack of awareness before the accident of the catastrophic potential of rudder reversals, even at speeds below design maneuvering speed;
6. Industry-common, but incorrect, pilot assumptions about aircraft maneuvering speed based upon prevailing definitions of the term; and
7. The lack of clear regulatory verification requirements to identify and correct adverse characteristics through flight-testing and evaluation of handling qualities of flight control systems during original, as well as subsequent, "derivative" model, aircraft certification.
The probable cause of this accident was the onset of a design-induced, adverse aircraft pilot coupling (APC) event that led to rapid development of excessively high aerodynamic lateral loads resulting in the catastrophic structural failure of the vertical stabilizer and rudder in only six and one-half seconds.
The event was triggered by an unexpectedly sensitive response of the rudder to an initial, single pedal input by the pilot during a wake vortex encounter. Due to the unique characteristics in the aircraft's flight control system design, the pilot became caught in an adverse APC/pilot involved oscillation mode as he attempted to counter the effects of that input. Specifically, after making a control wheel input followed by a rudder input intended to achieve a desired aircraft response, the over-sensitivity of the rudder control system induced the pilot to make additional, essentially cyclic, corrective rudder inputs as he attempted to stabilize the aircraft. Unknown to the pilot, because of the sensitivity of the rudder controls and the powerful nature of the hydraulically driven rudder actuators, these corrective inputs rapidly generated rupture loads. The rudder travel limiter unit (RTLU) and yaw damper failed to protect against the build up of these loads due to deficiencies in the flight control architecture design.
Contributing factors to the accident included:
1. The manufacturer's failure to disclose information learned from prior in-service high-load events demonstrating the adverse APC characteristics of the A300-600 flight control system and the resulting risk of structural overload;
2. Extraordinary rudder sensitivity at increased airspeeds due to a high rudder pedal breakout force relative to the shallow (low) rudder pedal force gradient and a corresponding reduction in rudder pedal travel that makes the A300-600 uniquely susceptible to adverse APC/pilot involved oscillation;
3. The rudder travel limiter unit's inability to protect the aircraft from excessive lateral loads;
4. The inability of the yaw damper, when the rudder pedal is held at the stop, to damp out motions resulting from the adverse APC/pilot involved oscillation tendencies of the aircraft;
5. Industry-wide lack of awareness before the accident of the catastrophic potential of rudder reversals, even at speeds below design maneuvering speed;
6. Industry-common, but incorrect, pilot assumptions about aircraft maneuvering speed based upon prevailing definitions of the term; and
7. The lack of clear regulatory verification requirements to identify and correct adverse characteristics through flight-testing and evaluation of handling qualities of flight control systems during original, as well as subsequent, "derivative" model, aircraft certification.
Also of note is that no pilot in the static tests was able to modulate rudder at 250 kt. It was either maximum available deflection or nothing
The Committee also found that "the precursor or trigger is pilot related" in many adverse APC events, and that "an environmental or vehicle trigger" often "precedes the pilot trigger." (NRC Study, p. 54.) According to Figure 4a below, reproduced from page 19 of the Group Chairman's Aircraft Performance Study Addendum #1, the initial right wheel input preceded the First Officer's first application of rudder by approximately0.6 seconds. (Time in seconds is listed on the horizontal line of the figures; 839 seconds corresponds with 09:15:47.2 EST and 850.3 with 09:15:58.5 EST (tail separation). The second wake encounter begins at 841.8 seconds/09:15:50 and ends at 845.8 seconds/09:15:54. Therefore, recorded data in these figures account for 11.3 seconds before stabilizer separation.) The initial flight control inputs were triggered by the
second wake turbulence encounter. The pilot's initial full right wheel input did not overpower the wake, and the aircraft roll attitude did not respond. Roll actually increased from about 23 degrees left angle of bank, at the onset of the wake turbulence, to a peak of approximately 25 degrees before reversing toward wings level. (Figures 2 and 4e of Group Chairman's Aircraft Performance Study Addendum #1, pp. 17 and 23, respectively.)
second wake turbulence encounter. The pilot's initial full right wheel input did not overpower the wake, and the aircraft roll attitude did not respond. Roll actually increased from about 23 degrees left angle of bank, at the onset of the wake turbulence, to a peak of approximately 25 degrees before reversing toward wings level. (Figures 2 and 4e of Group Chairman's Aircraft Performance Study Addendum #1, pp. 17 and 23, respectively.)
Looks perhaps like he should on this a/c type Pssst Shadow -- What's with the pic of Tafari Makonnen?
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AMR 587 Airbus Crash
RatherBeFlying,
NTSB hearing on AA 587, excerpt.
"PROBABLE CAUSE AND CONTRIBUTING FACTORS"
"The probable cause of this accident was the onset of a design-induced, adverse aircraft pilot coupling (APC) event that led to rapid development of excessively high aerodynamic lateral loads resulting in the catastrophic structural failure of the vertical stabilizer and rudder in only six and one-half seconds."
In the NTSB reports there is no mention of the possibility of a free floating rudder! Fact - NO PILOT would kick the rudder back and forth as recorded on the FDR. Period!!!
When the rudder was struck broadside by the .3 and .4 G forces, first on one side and then on the other, by the rotating vortices from the B-747 "Heavy", the linkages to the rudder actuators failed! (NASA states that, "the rotating forces in a vortex can reach 300'/sec.")
These rotating forces were also striking the large surface area of the vertical stabilizer. When the vertical fin was then struck broadside, by the .8 g force, the abrupt Yaw initiated an inertia force that sheared off both engines from their pylons and the fin from its support structure.
IN THE ATTEMPTED RECOVERY MANEUVER , THE CO-PILOT USED A FULL RIGHT AILERON INPUT, TO COUNTER THE STEEP LEFT BANK. HOWEVER, THERE IS NO EVIDENCE OF ANY RIGHT RUDDER INPUT TO ASSIST IN THE RECOVERY ATTEMPT!! THERE WAS NO RUDDER INPUT AVAILABLE !!!!!!!
If ATC had furnished an extended separation interval behind the B-747 "Super Heavy", (Full Fuel Load, Non Stop to Tokyo!), this accident might not have occurred!!!!
This is the first accident, of this type, in 100 years of flight, where an aircraft is flown, in a perfect formation joinup, on a horizontal tornado. (The vortex off the left wing tip of the B-747 "Heavy".)
NTSB hearing on AA 587, excerpt.
"PROBABLE CAUSE AND CONTRIBUTING FACTORS"
"The probable cause of this accident was the onset of a design-induced, adverse aircraft pilot coupling (APC) event that led to rapid development of excessively high aerodynamic lateral loads resulting in the catastrophic structural failure of the vertical stabilizer and rudder in only six and one-half seconds."
In the NTSB reports there is no mention of the possibility of a free floating rudder! Fact - NO PILOT would kick the rudder back and forth as recorded on the FDR. Period!!!
When the rudder was struck broadside by the .3 and .4 G forces, first on one side and then on the other, by the rotating vortices from the B-747 "Heavy", the linkages to the rudder actuators failed! (NASA states that, "the rotating forces in a vortex can reach 300'/sec.")
These rotating forces were also striking the large surface area of the vertical stabilizer. When the vertical fin was then struck broadside, by the .8 g force, the abrupt Yaw initiated an inertia force that sheared off both engines from their pylons and the fin from its support structure.
IN THE ATTEMPTED RECOVERY MANEUVER , THE CO-PILOT USED A FULL RIGHT AILERON INPUT, TO COUNTER THE STEEP LEFT BANK. HOWEVER, THERE IS NO EVIDENCE OF ANY RIGHT RUDDER INPUT TO ASSIST IN THE RECOVERY ATTEMPT!! THERE WAS NO RUDDER INPUT AVAILABLE !!!!!!!
If ATC had furnished an extended separation interval behind the B-747 "Super Heavy", (Full Fuel Load, Non Stop to Tokyo!), this accident might not have occurred!!!!
This is the first accident, of this type, in 100 years of flight, where an aircraft is flown, in a perfect formation joinup, on a horizontal tornado. (The vortex off the left wing tip of the B-747 "Heavy".)
Last edited by wsherif1; 12th Mar 2004 at 05:52.
wsherif1,
After reading all 60-some pages of AA's submission, I am at present persuaded that APC is well supported by the available facts and more probable than an immediate loss of the rudder.
But of course, I'm still waiting for Airbus to hire a 747 and fly a fully instrumented A300-600 through the accident profile -- perhaps with bang seats or flown from the ground
After reading all 60-some pages of AA's submission, I am at present persuaded that APC is well supported by the available facts and more probable than an immediate loss of the rudder.
But of course, I'm still waiting for Airbus to hire a 747 and fly a fully instrumented A300-600 through the accident profile -- perhaps with bang seats or flown from the ground
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RatherBeFlying,
Your comment,
"After reading all 60-some pages of AA's submission, I am at present persuaded that APC is well supported by the available facts and more probable than an immediate loss of the rudder."
AA is correct, the lead up to the accident was APC, and then the real cause was AP-decoupling. When the rudder was struck broadside, from opposite directions, severing the linkages to the rudder actuators, there was no longer any APC.
The rudder loss was not immediate but occurred after the .3 and .4G forces struck it.
What other explanation is there, for the co-pilot not to use right rudder to assist the right aileron input, in the attempted recovery maneuver? There was no rudder input available!!!
Your comment,
"After reading all 60-some pages of AA's submission, I am at present persuaded that APC is well supported by the available facts and more probable than an immediate loss of the rudder."
AA is correct, the lead up to the accident was APC, and then the real cause was AP-decoupling. When the rudder was struck broadside, from opposite directions, severing the linkages to the rudder actuators, there was no longer any APC.
The rudder loss was not immediate but occurred after the .3 and .4G forces struck it.
What other explanation is there, for the co-pilot not to use right rudder to assist the right aileron input, in the attempted recovery maneuver? There was no rudder input available!!!
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AA587 F/O Sten Molin Had Kicked Rudder Before...
From NTSB File:
"Person Interviewed: John Francis LaVelle
Position: Captain, B-737, American Airlines,
Represented By: Mr. Ray Duke, Attorney Allied Pilots Association
Date and Time: July 15,2002,0915.EDT
Present: Operations Group members David Ivey, Bart Elias, James Goachee, Delvin
Young, John Lauer
. Location: Telephonehtewiew ,
Captain LaVelle stated that his date of birth was May 21,1960 and that American
Airlines hired him on October 28,1986. He estimated his total flying time to be about
14,000 hours and currently was a captain on the B-737. Positions he had held since being
. hired by American included flight engineer B-727, first officer MD-80, first officer B-
757/767, first officer MD-11 , captain E727 and current was a captain and check aiman
on the B-737. Captain LaVelle estimated his flying times to be about 1,700 hours on the
B-727 while flying as captain, and about 1,200 hours as captain on the B-737.
He stated he had met Ed States, the captain, and stated that they had met in
operations a few times. He only had casual conversations with him.
He knew Sten Molin, the first officer. They had flown together on a number of
occasions on the B-727. When they first met, Captain LaVelle was a junior captain and
Sten Molin was a junior first officer. Both were on reserve in the New York base.
He described Mr. Molin’s personality as that of a perfectionist who worked hard
and did everything by the book. He was a real gentleman as well. He said the first met in
May 1997, and the last time he saw Sten Molin was sometime in the summer of 2001 in
operations. He was just as he always was; a nice person and Captain LaVelle enjoyed his
company.
Captain LaVelle said he flew two or three trips with Mr. Molin over a 12 month
period. He stated that Mr. Molin’s flying skills were excellent. He had excellent flying
ability, however, he had one strange tendency: to be very agressive on the rudder pedals.
Captain LaVelle stated that during a climb out in a B-727, while the airplane was “dirty
of with flaps 5 degrees”, Mr. Molin stroked the rudder pedals “1-2-3, about that fast.”
Captain LaVelle thought they had lost an engine. Captain LaVelle asked him what he
was doing, and Mr. Molin said he was leveling wings due to wake turbulence. Captain
LaVelle stated that Mr. Molin never leveled the wings, and his actions just created
yawing moments on the airplane. M e r they cleaned up the airplane they discussed it
M e r . Mr. Moli told him he was leveling the wings as per the M. Captain
LaVelle told him it was quite aggressive, and that it didn’t really level the wings. They
talked about the AAMP, Mi. Molin insisted that AAMP (Advanced Aircraft
Maneuvering Program) gave him directions to use rudder pedals in that fishion. Captain
LaVelle disagreed, and said he thought the use of rudder was, according to AAMP, for
use at lower airspeeds.’ He disputed Mr. Molin and told him to be less aggressive and
more coordinated using rudder.
- . ..
Captain LaVelle said that on two subsequent occasions Mr. Molin modified his
wake turbulence manuever to comply with his wishes. Mr. Molin used rudder during
these encounters but did not go to the full stop. He was still very quick.
During this first wake turbulence encounter, Captain LaVelle stated that it did not
require any more than aileron to level the wings. Occasion (wake encounter) was nothing
more than needing a little aileron to level the wings. Captain LaVelle thought that Mr.
Molin was more aggressive than he needed to be. He said the B-727 was very a very
stable airplane. He did not have to be that aggressive.
He recalled the fist encounter to be during the “clean up” [ d e r departure] on the
B-727. The altitude was between 1,000 and 1,500 feet. It was somewhere around this
altitude range that the event occurred. He believed Mr. Molin that the rudder was pushed
to fill stops. He said the effect on B-727 was that it created an uncomfortable yaw to the
“left- right- left”. There were heavy side-loads. He said he thought they went to left first,
but was not sure. Mr. Molin stopped using the rudder on his own. Captain LaVelle
thought they had an engine problem so his attention was drawn to the engine instruments.
When asked, he said he did not think Mr. Molin made any aileron inputs during the
encounter. The rudder never leveled the wings. He did not recall the wings moving, but
experienced, “sideload, sideload, sideload”.
.
His experience has been that you have to hold rudder in to get wing leveling fi-om
rudder. The AAMP program was brought up by Mr. Molii in their conversation after the
event. He was adamant that he was complying with AAMP. Captain LaVelle requested
that Mr. Molin review the AAMP program when he got home, and to be less aggressive
when he flew with him. It never came up in conversation again. This was first time he
flew with him. Months later, when they flew together, they encountered wake turbulence
on two separate occasions with him again. During the subsequent times they flew
together, the subject did not come up again in conversation ifMr. Molin had reviewed the
AAMP.
Captain LaVelle knew Mr. Molin had a civilian background and had been a
commuter pilot. He was proud that his dad had been an Eastem Airlines pilot. He told
Captain LaVelle that his father had taught him to fly when he was very young.
Regarding the AAMP program, Captain LaVelle thought he went through it once
in 1995 or 1996. He said he was a first officer on the B-767 at the time. He stated there
was AAMP training in the simulator, Once every checkride there is some kind of
airplane upset training received in the simulator.
had “hands of silk.” He could grease the Bi727 on landings and had good systems
knowledge.
Captain LaVelle when asked, had no recollection of what type of airplane they
were following during the first wake turbulence encounter.
Captain LaVelle stated that he was a C-130 pilot in the United States Air Force
Reserves. On one occasion, he was the last airplane in a 12-ship formation and
experienced wake turbulence. He had some very remarkable full aileron deflection with
full-scde rudder deflection, yet still rolled in the opposite direction. It was not until the
C-130 got out of the vortex that the airplane began to respond to control inputs. He went
to about 60 degrees of bank and was at an altitude of 300 feet during low-level operations
when the upset occurred. Once or twice while flying the MD-80 did he encounter wake
turbulence and he may have hit a control stop with ailerons. He was behind a B-757 on
one occasion. He used aileron only and leveled the wings. It was on an approach to a
domestic airport.
Captain LaVelle said the first event involving Mr. Molin happened about May
1997. The subsequent two wake turbulence encounters were separated by a few months;
perhaps in September 1997 and December 1997. He said that when he is the non-flying
pilot, he follows along on the rudder pedals. He felt Mr. Molin’s inputs on the rudder
pedals during that first wake turbulence event. He said it is typical for him to fly with his
feet on the pedals at critical times when the copilot is flying. He did not know what other
captains did with their feet while flying.
When asked why he remembered the event with such clarity five years later,
Captain LaVeIle stated that it was ti very aggressive maneuver and he had never seen any
other pilot do this but Mr. Molin. When questioned-about the initial direction of the yaw,
Captain LaVelle said he thought it was the left rudder input first but it could have been
the right. He said the wake vortex encounter with Mi. Molin was not much of anything.
Maybe just some choppy air. He thought that Mr. Molin may have been responding to
the choppy air. The ailerons were kept level and he used just the rudder pedals.
He stated that he was not a chkk airman at the time of the encounter. He did not
become a check airman until he became a B-737 captain.
He said he did not document or inform anyone at American Airlines, regarding
the event.
The two or three events did not seem very significant. Usually he did not
encounter wake turbulence very often. Perhaps once every quarter. Captain LaVelle
said he flew with Mi. Molin three times. Three separate trips and both of them were on
reserve status. He did not recall how many legs they flew together.
During the second and third enkounters Mr. Molin applied rudder with
During the first event, he stated he did not think Mr. Molin applied any aileron.
coordinated aileron and it was not aggressive.
Maybe a little, but it was full or close to full rudder deflection. He did not believe it was
the first leg of the first trip together in which‘the turbulence encounter happened. It was
probably the second or third time that Mr. Molin was at a e controls. It startled him
because Mr. Molin had been so smooth on the controls.
Captain LaVelle stated the wake turbulence encounter could have been due to
thermal activities or a preceding airplane. He did not think they were following a heavy
airplane. He did not recall aggressive movements or abnormal rudder inputs fiom Mr.
Molin during approaches or during the last two or three times they flew together.
When asked if he had ever made any accidental inputs to the rudder pedals while he
feet were on the pedals, Captain LaVelIe answered in the negative.
Captain LaVelle’s concluding thoughts were that he considered Mr. Molin a fiiend.
He was a great guy. He was a great pilot in all aspects except the one quirk; his use of
the rudder pedals. When asked why he had waited until now to disclose this event with
the accident first officer, he stated that he believed the NTSB was more interested in
interviewing pilots that flew the A300 and had more recent experience flyihg with the
accident crew. He said he had thought about his prior event when he heard that a wake
turbulence encounter with the accident airplane might have been a factor in the accident..."
"Person Interviewed: John Francis LaVelle
Position: Captain, B-737, American Airlines,
Represented By: Mr. Ray Duke, Attorney Allied Pilots Association
Date and Time: July 15,2002,0915.EDT
Present: Operations Group members David Ivey, Bart Elias, James Goachee, Delvin
Young, John Lauer
. Location: Telephonehtewiew ,
Captain LaVelle stated that his date of birth was May 21,1960 and that American
Airlines hired him on October 28,1986. He estimated his total flying time to be about
14,000 hours and currently was a captain on the B-737. Positions he had held since being
. hired by American included flight engineer B-727, first officer MD-80, first officer B-
757/767, first officer MD-11 , captain E727 and current was a captain and check aiman
on the B-737. Captain LaVelle estimated his flying times to be about 1,700 hours on the
B-727 while flying as captain, and about 1,200 hours as captain on the B-737.
He stated he had met Ed States, the captain, and stated that they had met in
operations a few times. He only had casual conversations with him.
He knew Sten Molin, the first officer. They had flown together on a number of
occasions on the B-727. When they first met, Captain LaVelle was a junior captain and
Sten Molin was a junior first officer. Both were on reserve in the New York base.
He described Mr. Molin’s personality as that of a perfectionist who worked hard
and did everything by the book. He was a real gentleman as well. He said the first met in
May 1997, and the last time he saw Sten Molin was sometime in the summer of 2001 in
operations. He was just as he always was; a nice person and Captain LaVelle enjoyed his
company.
Captain LaVelle said he flew two or three trips with Mr. Molin over a 12 month
period. He stated that Mr. Molin’s flying skills were excellent. He had excellent flying
ability, however, he had one strange tendency: to be very agressive on the rudder pedals.
Captain LaVelle stated that during a climb out in a B-727, while the airplane was “dirty
of with flaps 5 degrees”, Mr. Molin stroked the rudder pedals “1-2-3, about that fast.”
Captain LaVelle thought they had lost an engine. Captain LaVelle asked him what he
was doing, and Mr. Molin said he was leveling wings due to wake turbulence. Captain
LaVelle stated that Mr. Molin never leveled the wings, and his actions just created
yawing moments on the airplane. M e r they cleaned up the airplane they discussed it
M e r . Mr. Moli told him he was leveling the wings as per the M. Captain
LaVelle told him it was quite aggressive, and that it didn’t really level the wings. They
talked about the AAMP, Mi. Molin insisted that AAMP (Advanced Aircraft
Maneuvering Program) gave him directions to use rudder pedals in that fishion. Captain
LaVelle disagreed, and said he thought the use of rudder was, according to AAMP, for
use at lower airspeeds.’ He disputed Mr. Molin and told him to be less aggressive and
more coordinated using rudder.
- . ..
Captain LaVelle said that on two subsequent occasions Mr. Molin modified his
wake turbulence manuever to comply with his wishes. Mr. Molin used rudder during
these encounters but did not go to the full stop. He was still very quick.
During this first wake turbulence encounter, Captain LaVelle stated that it did not
require any more than aileron to level the wings. Occasion (wake encounter) was nothing
more than needing a little aileron to level the wings. Captain LaVelle thought that Mr.
Molin was more aggressive than he needed to be. He said the B-727 was very a very
stable airplane. He did not have to be that aggressive.
He recalled the fist encounter to be during the “clean up” [ d e r departure] on the
B-727. The altitude was between 1,000 and 1,500 feet. It was somewhere around this
altitude range that the event occurred. He believed Mr. Molin that the rudder was pushed
to fill stops. He said the effect on B-727 was that it created an uncomfortable yaw to the
“left- right- left”. There were heavy side-loads. He said he thought they went to left first,
but was not sure. Mr. Molin stopped using the rudder on his own. Captain LaVelle
thought they had an engine problem so his attention was drawn to the engine instruments.
When asked, he said he did not think Mr. Molin made any aileron inputs during the
encounter. The rudder never leveled the wings. He did not recall the wings moving, but
experienced, “sideload, sideload, sideload”.
.
His experience has been that you have to hold rudder in to get wing leveling fi-om
rudder. The AAMP program was brought up by Mr. Molii in their conversation after the
event. He was adamant that he was complying with AAMP. Captain LaVelle requested
that Mr. Molin review the AAMP program when he got home, and to be less aggressive
when he flew with him. It never came up in conversation again. This was first time he
flew with him. Months later, when they flew together, they encountered wake turbulence
on two separate occasions with him again. During the subsequent times they flew
together, the subject did not come up again in conversation ifMr. Molin had reviewed the
AAMP.
Captain LaVelle knew Mr. Molin had a civilian background and had been a
commuter pilot. He was proud that his dad had been an Eastem Airlines pilot. He told
Captain LaVelle that his father had taught him to fly when he was very young.
Regarding the AAMP program, Captain LaVelle thought he went through it once
in 1995 or 1996. He said he was a first officer on the B-767 at the time. He stated there
was AAMP training in the simulator, Once every checkride there is some kind of
airplane upset training received in the simulator.
had “hands of silk.” He could grease the Bi727 on landings and had good systems
knowledge.
Captain LaVelle when asked, had no recollection of what type of airplane they
were following during the first wake turbulence encounter.
Captain LaVelle stated that he was a C-130 pilot in the United States Air Force
Reserves. On one occasion, he was the last airplane in a 12-ship formation and
experienced wake turbulence. He had some very remarkable full aileron deflection with
full-scde rudder deflection, yet still rolled in the opposite direction. It was not until the
C-130 got out of the vortex that the airplane began to respond to control inputs. He went
to about 60 degrees of bank and was at an altitude of 300 feet during low-level operations
when the upset occurred. Once or twice while flying the MD-80 did he encounter wake
turbulence and he may have hit a control stop with ailerons. He was behind a B-757 on
one occasion. He used aileron only and leveled the wings. It was on an approach to a
domestic airport.
Captain LaVelle said the first event involving Mr. Molin happened about May
1997. The subsequent two wake turbulence encounters were separated by a few months;
perhaps in September 1997 and December 1997. He said that when he is the non-flying
pilot, he follows along on the rudder pedals. He felt Mr. Molin’s inputs on the rudder
pedals during that first wake turbulence event. He said it is typical for him to fly with his
feet on the pedals at critical times when the copilot is flying. He did not know what other
captains did with their feet while flying.
When asked why he remembered the event with such clarity five years later,
Captain LaVeIle stated that it was ti very aggressive maneuver and he had never seen any
other pilot do this but Mr. Molin. When questioned-about the initial direction of the yaw,
Captain LaVelle said he thought it was the left rudder input first but it could have been
the right. He said the wake vortex encounter with Mi. Molin was not much of anything.
Maybe just some choppy air. He thought that Mr. Molin may have been responding to
the choppy air. The ailerons were kept level and he used just the rudder pedals.
He stated that he was not a chkk airman at the time of the encounter. He did not
become a check airman until he became a B-737 captain.
He said he did not document or inform anyone at American Airlines, regarding
the event.
The two or three events did not seem very significant. Usually he did not
encounter wake turbulence very often. Perhaps once every quarter. Captain LaVelle
said he flew with Mi. Molin three times. Three separate trips and both of them were on
reserve status. He did not recall how many legs they flew together.
During the second and third enkounters Mr. Molin applied rudder with
During the first event, he stated he did not think Mr. Molin applied any aileron.
coordinated aileron and it was not aggressive.
Maybe a little, but it was full or close to full rudder deflection. He did not believe it was
the first leg of the first trip together in which‘the turbulence encounter happened. It was
probably the second or third time that Mr. Molin was at a e controls. It startled him
because Mr. Molin had been so smooth on the controls.
Captain LaVelle stated the wake turbulence encounter could have been due to
thermal activities or a preceding airplane. He did not think they were following a heavy
airplane. He did not recall aggressive movements or abnormal rudder inputs fiom Mr.
Molin during approaches or during the last two or three times they flew together.
When asked if he had ever made any accidental inputs to the rudder pedals while he
feet were on the pedals, Captain LaVelIe answered in the negative.
Captain LaVelle’s concluding thoughts were that he considered Mr. Molin a fiiend.
He was a great guy. He was a great pilot in all aspects except the one quirk; his use of
the rudder pedals. When asked why he had waited until now to disclose this event with
the accident first officer, he stated that he believed the NTSB was more interested in
interviewing pilots that flew the A300 and had more recent experience flyihg with the
accident crew. He said he had thought about his prior event when he heard that a wake
turbulence encounter with the accident airplane might have been a factor in the accident..."
Union Goon
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This encounter as described by Lavelle was disputed by the engineers of the trips in question, but lets say for the second that it is absolutely true, and no other motivations were at work here...
So what did we learn?
The Boeings weren't damaged in the slightest, and the Airbus crashed...
THAT my friend, pretty much says it all.
Cheers,
Wino
( American Airlines A300 LGA F/O, and friend of Ed States and Sten Molin, with far more time in the cockpit with these gentlemen than John Francis Lavelle)
So what did we learn?
The Boeings weren't damaged in the slightest, and the Airbus crashed...
THAT my friend, pretty much says it all.
Cheers,
Wino
( American Airlines A300 LGA F/O, and friend of Ed States and Sten Molin, with far more time in the cockpit with these gentlemen than John Francis Lavelle)
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411A
Your comment,
"About says it all, really...
Why are we not surprised"
Do you mean that an experienced co-pilot would change his mode of operation with each different Captain he flew with? All the other Captains lauded Sten's piloting abilities!
One mans recall against the many, I think not!
Your comment,
"About says it all, really...
Why are we not surprised"
Do you mean that an experienced co-pilot would change his mode of operation with each different Captain he flew with? All the other Captains lauded Sten's piloting abilities!
One mans recall against the many, I think not!