AMR 587 Airbus Crash (merged)

[ANOpax]

Bloomberg News is reporting the following;

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

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

Rudder Movements

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

[Bubbette]

The hearings are available live (Eastern US time) here: www.ntsb.gov.

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

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

http://www.ntsb.gov/Events/2001/AA587/exhibits/240246.pdf see page 3.

[411A]

AA has sent pilots for advanced upset training, which uses the rudder quite vigorously...in large jet transports, this is NOT a good idea.

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

(Can hear the moans from the APA already...:rolleyes: )

[747FOCAL]

I still have problems believing the movement caused all of the tail to come off. I can see the rudder coming off by itself, but not the entire tail. Unless.....there is a real structural flaw that is built into the design of the tail.

I am not trying to start a conspiracy theory debate. :)

[411A]

Barry's Anorak,

Don't mean to upset you but...

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

It seems the lessons learned many years ago have been forgottren by some of the younger guys...one wonders, will they EVER LEARN?

[filejw]

Sorry to agree however i can still rememerber being told not use the rudder in this manner...in the late to mid 70's.In those days all the ground school instructors were old engineers and mechanics.JW:( :(

[Burger Thing]

I am a current widebody Captain, still in my 30's and holding down a junior management role with my flag carrier employer. Not that that makes me jump up and down with joy, it merely makes me happy that you hear that others are doing really well!

Barry's Anorak... maybe you should choose an outfit which suits you better. Your Your Anorak seems at leat 3 numbers too large. Sorry, but sound very cocky and immatured to me.:rolleyes: :D

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

(Sorry, 411A, didn't mean to be disrespectful ;) )

[Kefuddle_UK]

Does nothing ever change in internet land? A discussion I have been waiting for serious comment on about a crucial hearing of one of the most bizzare and seriously tragic events in aviation in recent years is hijacked and you guys just want to score points off each other. Just stop a moment and think of your responsibilities in this industry!

Can we please resume the proper thread of discussion?

[Belgique]

Latest Uncommanded rudder upset

American Airlines, A300-605R, Flight 934 from Guyaquil (Ecuador) to Miami, Oct. 28. At 31,000 ft. autopilot kicked off, plane rolled 30 deg into right bank, climbed 1,000 ft and descended 800 ft. before pilots were able to restore control. 3 flight attendants injured.

[patrickal]

In an effort to try to bring this thread back to a technical level, suppose the rudder control went "stupid" and started to travel back and forth, from stop to stop, on it's own. Wouldn't the severe yaw motion that would result cause the engine pylons to fail? My thoughts are that, like most other air disasters, this one resulted from a combination of problems that all met at one single point in time.

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

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

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

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

This is all conjecture on my part, but I don't see any other clear cause. I'd love comments by some of the more non-emotional members on this theory.

[GotTheTshirt]

Not familiar with Airbus but all other heavy jets have rudder authority limiting.
You cannot put large rudder inputs at speed even if you wanted to.
The limters ( in some cases 2 stage) set the maximum deflection for the speed to reduce the loading on fin and rudder, regardless of the amount of rudder pedal travel.

I would have asumed that Airbus did the same mathmatics:confused: :confused:

[ORAC]

LA Times (http://www.latimes.com/news/nationworld/nation/la-na-crash30oct30,0,1175354.story?coll=la%2Dhome%2Dtodays%2Dtimes )

Extracts:

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

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

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

Side-to-side rudder movements "can lead to structural loads that exceed the design strength of the fin," it added. The 1997 incident that prompted the letter did not cause a crash. The NTSB did not warn pilots of the potential danger until February.....

[Huck]

Now y'all take a moment to read just what rudder inputs would have had to have been.... Huge pedal forces in a sine pattern over more than a few seconds.... Them boys are dead; it's real convenient to park the blame in the cockpit.

[FDXmech]

Thoughts on A300-600 rudder travel limiting system:

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

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

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

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

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

Also, #2 yaw damp is sort of the back-up yaw damp channel with the #1 directly controlling the rudder.

[Shore Guy]

A couple of questions.....

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

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


The finger pointing at the dead pilots is repulsive, but not unanticipated. The legal implications are enormous, and if the basic design of the tail is found to be inadequate, the entire Airbus consortium is at risk (it is my understanding that the entire Airbus family have vertical stabs with similar design/material).

[Nopax,thanx]

Not the entire Airbus family - older A300's have a tin fin.

[lomapaseo]

> The finger pointing at the dead pilots is repulsive, but not unanticipated. The legal implications are enormous, and if the basic design of the tail is found to be inadequate, the entire Airbus consortium is at risk (it is my understanding that the entire Airbus family have vertical stabs with similar design/material).<

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

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

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

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

I suspect that the majority will select the latter.

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

I just don't see how the informed public will judge the pilots as the cause and then walk away.

[Kefuddle_UK]

Guys,

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

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

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


Cheers,
Kef.

[NigelOnDraft]

Just to clear something up...

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

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

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

NoD

[cwatters]

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

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

[Wino]

worse than that is what happens if the airplane on its own starts swinging the rudder back and forth. AA Airbus's have had several incidents where the rudder started swinging back and forth on its own hard enough to cause injuries.

If it decides to do it on its own you may be screwed. The Yawdampener has up to 15 degrees of authority depending on the regime of flight. The rudder load limiter limits the rudder down to 3.5 degrees of travel around 315 knots. So basically the Yaw dampener has full authority over the rudder. I am now to believe that should the nose yaw wildly (say for example in a wake turbulence encounter) that when the yaw dampener applies opposit rudder to counteract the yaw it may snap the tail off the aircraft. What a lovely design.


Plus has anyone else noticed how badly airbus is behaving during the hearings?

Apparently there has NEVER been a design defect in an airbus aircraft.

Cheers
Wino

[NigelOnDraft]

cwatters:

<<So what should you do if the initial yaw is caused by sever turbulence?>>
How on earth does turbulence lead to significant yaw that is not almost immediately corrected by normal aerodynamics?

<<Wouldn't you be tempted to apply full oposite rudder to correct it?>>
Absolutely not... and I would be horrified to know you would even consider touching the rudders in this case?

In any jet aircraft I have flown (except the one that hovers, which is different), from light jet trainer to FBW widebody, to Boeing, you only use the rudder pedals:
1. To taxi
2. To kick off drift on a xwind landing
3. To conteract (and no more) the effects of an engine failure

NoD

[BlueEagle]

Apart from the three occasions mentioned above the only other time I have been required to use rudder on a jet is in the SIM recovering from unusual attitudes, in this case a massive overbanking to almost 90 degrees, then just enough rudder opposite to the direction of bank to prevent the nose dropping, roll off bank and gently pull out. That was taught on the B744.

[Edited to get it right!:o ].

[Anthony Carn]

Anyone know the airspeed at the time of this incident ?

[NigelOnDraft]

260ish?

Blue Eagle - interesting about the rudder. At 90 AoB, I would have thought the nose needed very little persuading to drop!

NoD

[N380UA]

As the printed NTSB report stated, the number two pitch trim and the yaw damper would not engage. The corresponding CB was cycled and all was back on line and cleared by line maint..
The cause may have never really been fixed. The yaw damper as well as the pitch trims both serve the FAC, at least on the 310, and there may have been the problem.
Now, what if the vortices from the JAL flight hit the Airbus in such an unfortunate angel, that the parameters given through the FAC were exceeded, the alpha-floor trying to correct a too high angle of attack, re-triggers the pitch and yaw damper problem causing the accident.
Such a scenario should of course have produced an ECAM warning, and yet, if there was a system problem in the first place it may never even have been displaced.

A bit of maybe but just a thought.

Cheers

[patrickal]

In my 20+ years experience in computer technology, I have never been confident in recyling circuit breakers to fix a problem. At best, this process usually masks an intermittent problem that almost always returns. I do not understand why the airline industry, especially in todays electronics dependant aircraft, continue to endorse this process as valid for fixing problems.

[Belgique]

Patrickal

Quite right. And the "cleared" problem need not have been electrical. It might have been, in the case of AA587, mechanical and related to the 3rd servo-actuator (the one that serves up the output for both yaw dampers). Yaw damper actuators spend 99.999% of their time moving through a very limited travel and so probably pick up quite distinctive wear patterns. Perhaps it's only at "those other times" that travel outside their normal comfort zone detects a bit of stiction (or dirty hyd fluid or corrosion/erosion) and causes the FAC to hiccup. Those other times? Pre-start BITE checks and the dynamism of wake encounters or CAT.

Fascinating design arrangement that one. A soft-drive (#2YD) and a hard-drive (#1YD) act through a singular servo-actuator valve. Hardly fail-safe or fail-operational if a momentary intermittency in one causes the system NOT to trip, but to cycle between the two yaw damper outputs. I wonder if that might induce rudder oscillations?

During the NTSB's Public Docket (just finished) they very vaguely referred to a failure mode of those three rudder hyd actuators as "force-fighting" and reassured everyone that because of that FEDEX hangar failure of an actuator they'd implemented a 1300 hour synchronization check. Now that's about as reassuring as Firestone introducing a 10,000 mile safety check on their quality radial tyres. It doesn't make that failure mode evaporate. Until force-fighting was mentioned, I thought that that possibility might just have been a figment of my imagination.

Also interesting that the Airbus chappie gave, as a reason for having three rudder actuators connected to a single rudder panel, the logic that "how else would you provide for each of the 3 hyd systems to be available and cover a dual failure (in the uncontained engine failure case)". But no-one seemed to think it relevant to query whether it constituted "reasonable redundancy". That term was introduced by Dr Loeb in the NTSB Public Docket on the 737 rudder hard-overs. Eventually Boeing has had to introduce a 737 fix. I personally find much similarity between the 737 rudder valve's shenanigans and the misconduct of the A300-600's rudder over the many incidents culminating in AA587. The similarity of the 737's actuator and the dual acting A300 yaw damper servo actuator is very striking. I'm suggesting that it may be the quintessential Achille's Heel.

Below (in a few links) is the story of two 747 uncommanded yaw incidents. Just reflect upon a similar malfunction involving NOT the life-saving split panel rudder arrangement in the 747 incidents, but the single panel scenario - with a number of FAC driven authorities fighting for rudder command and control (and perhaps passing the ball between them). The dismissive comment in the 747SP incident report is very telling when you think of AA587. It says:
"System redundancy had operated as required to limit the effect of the upper yaw damper anomaly" Here they are referring to the split rudder on that a/c.



A few links
one (http://www.ntsb.gov/NTSB/brief.asp?ev_id=20021018X05344&key=1)

two (http://www.pprune.org/forums/showthread.php?s=&threadid=70592)

three (http://www.atsb.gov.au/aviation/occurs/occurs_detail.cfm?ID=381)

four (http://www.pprune.org/forums/showthread.php?s=&threadid=2617&perpage=15&highlight=AA587&pagenumber=8) (the final two posts)

[PickyPerkins]

Does anyone who attended the NTSB Public Hearing October 29- November 1, 2002 at Belle Harbor, New York November 12, 2001, on the American Airlines Flight 587 crash have any observations or comments to share?

[wes_wall]

I watched a little via WebCast, and in part, AirBus seemed to be suggesting that the rudder movement was crew induced. In support of this position, they suggested that AA SIM training
was flawed, in that excessive rudder application was being recommended as a primary tool in recovering from uncommanded roll situations. AirBus also indicated that full pedal travel (about
1 inch) at 250K could cause enough movement and subsequent loading for the rudder to fail. They advocate use no rudder in roll recovery. I have never flown the Bus, other than a PAX, but something doesn’t add up. Evidently, the rudder limiters will not restrict movement at speed sufficiently to prevent structural problems. How can you certify an airplane that has a primary control surface which is likely to fail under normal flight operations?

Question for AirBus crew... There was a lot of conversation about unsafe gear proceedures. AirBus advised their recommended proceedure is to yaw the airplane back and forth in an attempt to free the gear, which requires alternating rudder inputs. I am sure this is at slower speeds, but is their a noted speed restriction to prevent rudder loading? AA's proceedure is to roll the airplane, 45 to 45, and refrain from rudder use. Comments?

And Blue Eagle, are you sure you did not apply top rudder to help prevent the nose from dropping while you returned the airplane to level flight.

[RatherBeFlying]

Graph on last page (http://www.ntsb.gov/Events/2001/AA587/exhibits/241833.pdf) shows four full opposite yaw damper oscillations and five full travel opposing pedal movements in the last seven seconds the tail was attached.

There has been considerable discussion that the breakout force on the rudder pedals is very close to that required for full allowable pedal motion at the accident airspeed. At this airspeed the pedal motion was limited to approximately one inch.

The yaw damper shows a classic sine wave with a lengthening of period over the seven second interval while the pedal movement shows greater excursions both in and out of phase with the yaw damper except that for one two second period the rudder pedal was held at full right.

The rudder travel limit was exceeded on four occasions, the last one could be the rudder coming off.

Both the yaw damper and PF seem to have perceived and reacted to rapid yaw oscillations.

While it seems that the evidence points to the tail suddenly being wrenched off, it should be noted that the first oscillation was contained within rudder travel limits and subsequent oscillations diverged. If the forward lug took any deformation, divergent aerolasticity would do the rest.

Taken from exhibit
168467 Oct 04, 2002 Systems 9 - A300-600 Yaw Damper System Overview (Exhibit No. 9-B)

[Anthony Carn]

Looking at the previous thread link, if my co-pilot started "booting" the rudder around like that at those speeds, then I'd have big worries about the fin on ANY aircraft type! Just try to visualise the aircraft response alone, to such inputs !

The yaw damper seems to be reacting correctly and in the correct sense and without excessive input.

Even in extreme unusual attitude recovery, the rudder should have little part to play. Warnings abound regarding the possibility of overstressing the fin with "excessive" rudder input.

Recovery ( I realise all pilots reading know this. Alternatively, correct me if I'm wrong. )

(a) -- Thrust +/- (max/min)

(b) -- Roll upright (smoothly but promptly)

(c) -- Pitch +/- (smoothly, within g limits/stall warning/shaker)

....In that order in your thoughts, albeit apparently "blended" together in enaction.

No yaw/rudder, though !

What flying experience did the handling pilot have, anyone, please ?

IMHO

[RatherBeFlying]

I've not had the "pleasure" of flying an a/c with only 1 inch of available rudder pedal movement in a sudden sideslip condition.

Fine modulation is next to impossible when the breakout force is close to that required for full available deflection; so I find a claim of booting the rudder untenable in this particular circumstance.

Missing from the graph is the sideslip condition -- it may well be buried elsewhere in the docket. Even without that the PF and yaw damper seem to have perceived a sideslip oscillation -- or was it the PF and YD triggering counteractions from each other?

Earlier I laid considerable suspicion on the yaw damper, but the pedal inputs are larger.

I would focus on unavailability of fine rudder pedal modulation and inadequacy of rudder travel limitation for these circumstances.

And I would also like to see other yaw damper readouts to see if the acccident graph is an appropriate action or a runaway. Yaw damper oscillations may trigger corrective actions from the PF. So maybe the YD should have been switched off, not that the crew had much time to figure out what was happening.

[Anthony Carn]

I used the term "booting" the rudder to describe abrupt full use of whatever available rudder travel there is, be it one inch or twelve inches or whatever. The readout shows abrupt full use of available rudder.

My experience of rudder limiters is that accurate modulation is still perfectly possible.

However, I say again that ZERO rudder input should be required/used when recovering from unusual attitudes in commercial jets. Normal teaching suggests that a small ammount of rudder in the same sense as any aileron input may be used, but emphasises that OVERSTRESSING THE FIN is a distinct possibility if the rudder is used too enthusiastically.

On the readout the yaw damper smoothly lags (and therefore is reacting to) pilot inputs. The pilot input is leading the yaw damper, as opposed to reacting to the yaw damper.

All IMHO and open to correction. Nothing in my comments is intended as a slur on the pilot; I'm simply stating my interpretation of the readout.

[BOING]

The US airlines with whose training I am familiar have all been teaching inappropriate rudder use in upset recoveries for about five years. It did not start as excessive use of rudder. Initially the teaching was that an "appropriate" amount of rudder would be used to aid recovery. Over the years "appropriate" slowly evolved into "full" use of rudder. It was easy to see this transition take place sitting in the left hand seat during simulator check rides. My objections that excessive rudder was being used were ignored by the training system.

Of course, a simulator check pilot, in my airline at least, does not actually occupy one of the pilots seats during a check, therefore he is unaware of the actual technique being used during an upset recovery. All the check pilot knows is that the recovery was successfully carried out, he cannot judge (or does not care) that the recovery technique could have seriously overstressed the aircraft.

The use of large amounts of rudder for upset recovery was initially introduced by a competition aerobatic pilot who had no swept wing, high speed flight experience outside of his airline time. A technique which is perfectly valid during aerobatics was misapplied to the airline scenario. The procedure was accepted by the FAA, probably out of similar ignorance.

To see the viewpoint of someone who really knows what he is talking about - been there, done that - in the air not just in the simulator, read Davies's " Handling the Big Jets" again.

[Wino]

Having flown with both airmen in question, neither was hamhanded nor unprofessional. Both had the farside of 5000 hours of experience in large jets and well over 1000 hours in type. They were the extremely professional talented aviators.

Anthony Carn,
The sim has since been reprogrammed to more accurately represent rudder forces. During my last sim I knocked the sim off the jacks while trying to apply a miniscule amount of rudder force.

I canfurther tell you that the A300-605r is different from the original A300b4 in several critical ways beyond the noted tin vs composit tail.

First off, THe A300b4 has a ratio type rudder load limiter (as do all boeings past the 727, which though it has a blocker system, also reduces rudder Power to 800 psi when the trailing edge flaps retract) so that full travel is always the same distance on the pedals, corresponding to a smaller movement of the rudder so that rudder forces/reactions stay somewhat constant. THe A300-605r ha a blocker system that is a menace. Airbus had it right in the A300b4 and went wrong from there.

2nd the A300b4 had outboard ailerons which were removed from the A300-605r greatly limiting its roll authority in certain regimes of flight. Furthermore, you cannot raise a wing with spoilers.


You do not seam to grasp how exquisitely sensitive the Airbus rudders become at high speed.

The blocker type rudder load limiter has been used in other aircraft, but only in conjunction with DEPOWERING the rudder. The A300 keeps its 3000 psi and gets very very sensitive. Picture a car that the brakes get more sensitive the faster you go (with no antilocks). Picture a car that going 80 miles an hour the only thing that will happen if you touch the brakes is that the wheels lock and the car spins out of control. That is an A300-605r.

Your experience of rudder load limiters is not the piece of crap that Airbus put on the A300-605r.


Boing, you are somewhat incorrect or just outdated. Advanced simulators can measure the projected Gs on an aircraft maneuver and excedeing the G limit would be recorded and stop the sim (In crash protect mode). Furthermore I have never seen anyone advocate uncoordinated rudder or to simply mash the rudder. The ball would go way out of the center if you did such a thing and then you would be repeating the maneuver. Otherwise you would be comitting a spin entry. Atleast that is how I was trained, by many different people at American and my previous airlines.


Ratherbe flying.
A rudder load limiter that allows the rudder to go beyond the limit doesn't seam to be limiting, does it?

CHeers
Wino

[Anthony Carn]

Wino -- Thanks for the excellent insight into the A300-605r and into the experience levels of the crew; This lays a few of my "theories" to rest.

My statement regarding unusual attitude recovery stands, but it really is up to manufacturers to give us an aeroplane which behaves "properly". One is left wondering, based upon your description !

[RatherBeFlying]

Wino A rudder load limiter that allows the rudder to go beyond the limit doesn't seem to be limiting, does it? That's what the Airbus graph shows.

Possible causes:
The rudder moved faster than the computer could keep up with
The limiter mechanicals/structure were overpowered by the rudder movement
Something wrong in the flight control algorithm
The other question is whether the rudder limits protect the a/c in all flight conditions. While the first rudder excursion was right at the limit, there is a possibility that the first structural damage to the forward lug happened at that point -- a small amount of flex might have started the entire train.

[ORAC]

AC, I've sent you a private message.

[wes_wall]

"The other question is whether the rudder limits protect the a/c in all flight conditions"

According to AirBus this past week, they do not!

[Few Cloudy]

I guess the first lesson for us all is that the rudder is a very powerful control. It can conceivably get you out of an upset situation but it can for sure get you into one too. It can also tear off the Fin (Vert Stab.) - as has been attested to by no less than John Tullamarine, the respected test pilot - if used in a cyclic manner. The RAF also issued warnings about using the flight controls in this manner on certain larger jet aircraft - particularly when being flown in formation.

Before going any further let us admit that we have little knowledge of the case in question and we weren't in the cockpit. What follows is surmise only on my part.

If the rudder is the last option in an upset, in my opinion it should be used. Vigorous use for "A little wake turbulence", however wouldn't be appropriate.

The comments from the Captain to the FO "Are you all right? " were during just such a cyclic useage period. This may have indicated a certain concern with the flight control inputs (as opposed to the atmospheric conditions.)

I have fairly often noticed a tendency for pilots to use rudder cyclically during approach in turbulent conditions (I am not talking about the alignment phase during the flare/touch down). This actually causes greater problems because an opposite aileron input is then required. The IAS difference from 140 odd knots to 260 knots and higher - as during climb out - causes a tremendous increase in the effect of control inputs.

The recent warning not to use the rudder in this manner still seems sensible.

[411A]

Hmmm, FewCloudy may just have hit the mark...many older guys who have been 'round for a long time (or...who were taught by same) know full well that large/rapid rudder inputs (machine or pilot induced) are NOT a good idea.
Look in the past guys for appropriate authority.
Seem to remember that Davies had it right in "Handling the Big Jets"... a primer for all younger jet airliner pilots.
Have loaned my copy to countless guys...good stuff enclosed.
Live and learn...;)

[Carrier]

> American denies Airbus ever formally warned that moving the rudder too

> much at high speed could cause it to come off. (Comment on AVweb)



The problem in this incident is that it did not happen at high speed. The whole flight lasted about two minutes from take off to crash. Obviously the aircraft was in post take off climb, probably following noise reduction procedure, and in that situation and short time could not possibly reach high speed!



I would expect ANY aircraft to be structurally capable of full control deflections at low speed, particularly at normal climb or approach speeds where wake turbulence and wind shear requiring strong control inputs are likely to occur. It is completely unacceptable that anyone should design, make, certify, operate and fly any aircraft incapable of this unless it is certified as Experimental and does not carry passengers, and then what about the risk to those on the ground. To do this with a public transport aircraft is sheer criminal negligence at the very least. I hope ALL of the culprits will be brought to account.



It is unacceptable to continue flying public transport aircraft in which the public's safety depends on a pilot in a moment of stress and urgency remembering not to tread too hard! This obvious structural weakness, which is openly admitted by the manufacturer, is no different from the Comet and Concorde crashes and for public safety demands the same response - the IMMEDIATE revocation of the Airworthiness Certificates of all transport aircraft with such a weakness. Will the various worldwide aviation authorities, particularly the FAA since the crash happened on their turf, have the moral fibre of the Brits or will passengers continue to be put at unacceptable and unnecessary risk because of political or other expediency?



While there is never a good time for addressing such a problem the worldwide aviation recession should lessen the impact on affected operators since there are many surplus aircraft they can lease to keep their operations functioning.



Pilots of affected aircraft should refer to the Transport Canada article and govern themselves accordingly: http://www.tc.gc.ca/civilaviation/systemsafety/newsletters/tp185/3-02/371.htm

[pigboat]

Hope you got thick skin.

[moggie]

But there was no grounding of the B737 for rudder hard-over (at least two fatal crashes) or the B747 for fuel pump explosions (TWA 800 was not caused by little green men, the US Navy or Airbus-employed saboteurs!).

It happens every time - the US based Boeing lovers start screaming "Airbus is unsafe" - just because Airbus are wiping the floor with Boeing.

All aeroplanes are potentially lethal - but fewer people died in this accident than as a result of p!ss-poor US DOMESTIC airline security last year. Maybe in bad taste, but realistic, folks.

Get real - get a life - get out more.

[wes_wall]

"The problem in this incident is that it did not happen at high speed. The whole flight lasted about two minutes from take off to crash. Obviously the aircraft was in post take off climb, probably following noise reduction procedure, and in that situation and short time could not possibly reach high speed! "



Gear and flaps were up and wake was encountered approx 0:1:27 after leaving the ground, alt 1840, speed 241K and accel. They were cleared to FL130.

[twistedenginestarter]

I must admit I find it a little bizarre that an entire tail snaps off a plane - for no apparent good reason - and nobody seems to be doing much about it.

[BlueEagle]

Does the A340 have a similar rudder construction and design to the one on the AA Airbus300?

In the unlikely event of losing two on the same side with T/O or climb power set I can see the need for a fairly quick and large amount of rudder to correct yaw.

[lomapaseo]

Regardless of how one feels about the design and certification standards, the fact remains that they are standards and represent a sizeable fleet. If some pilots feel that they can not adjust to these standards than they should simply stand down until such time that the standards are changed to accomodate them as the fleet retires due to old age.

The passengers deserve reassurance that it is safe to fly, not condemnation of the fleet that they fly on by people that were entrusted to understand and be trained to safely fly this fleet.

[Wino]

During the investigation of 587 the entire AA fleet of all aicraft was looked at for wake encounters, CAT, and anything else that might have over stressed the tails.

DFDRs data from the incidents were analyzed. In the 800 aircraft fleet that comprises AA (not including the commuter jets) there were no incidents of design or Ultimate load being exceded in the Fokker, McDonnel Douglas or Boeing fleets. In the teeny tiny airbus fleet of 35 aircraft there were 7 excedences of design loading of the tail (including two cases of autopilot malfuntions that caused the rudder pedals to continually move back and forth. It was impossible to disengage the rudder channel from the autopilot) and two excedences of ultimate load (587 and the other tail that is still removed in Tulsa, which turned out to be cracked even though several inspections had not found the cracks untill the tail was removed from the aircraft and ultrasounded)

Furthermore throughout the fleet more examples were found at FEDEX, a German airline, and on a swissair 330. (and yes the tails are very similar)

This is a serious problem that needs to be fixed. This is not about protectionism. Airbus has done absolutely ZERO to address this known problem. Atleast boeing comes up with a workaround untill a permanent fix can be implemented.

Cheers
Wino

[Tan]

I received this Avweb Avflash yesterday, rather interesting...


"587 HEARING POLARIZES: The public hearing into the crash of an American
Airlines Airbus last November has degenerated into a polarized blamefest
over rudder deflection. There's now no argument that five full back-
and-forth deflections of the A300-600's rudder caused the tail to rip
off American Airline's Flight 587, precipitating its crash in New York
last November 12, which killed all 260 aboard and five on the ground.
Airbus maintains it told American Airlines that its training on use of
the rudder was faulty and indicated that communication implies the
carrier knew such a failure was possible. American denies Airbus ever
formally warned that moving the rudder too much at high speed could
cause it to come off."

[Wino]

No one has yet proved that the pilots moved the rudder at all!

It has been proved that the rudder load limiter did not limit the rudder to design or ultimate load however. Further it has been proven that 2 other incidents have occured where the autopilot did not declutch from the rudder channel exceded design loading on the tail. In both of those cases the rudder pedals moved on their own for the entire duration of the event.

Most certainly the statement from the Airbus AOM that that rudder load limiter works by physically limiting the travel of the rudder so as not to over stress or over control the aircraft at high speeds has been proven false.

The Airbus alternate gear extension checklist calls for alternating rudder inputs to induce back and forth sideslips to lock the gear in place! Obviously according to airbus testimony we can't do that either. I guess I should just belly it in if I have a hydralic failure.



Cheers
Wino

[Huck]

Some enlightenment, please:

the previously posted Airbus graph shows "Pedal Command + YD."

Is that just pedal position? Do the pedals shadow the YD inputs, hence the "+YD" label?

Or is the pilot the only source of pedal movement?

[Loose rivets]

During multiple rudder deflections, for whatever reason, what is known about the differential air pressures within the fixed vertical structure. The lack of adequate venting that has been a problem in the past, might exacerbate the stresses during side loadings, especially if it changes rapidly several times in phase with the mechanical loads

[Wino]

If the autopilot commands a rudder movement the pedals will move as well. Normally this only happens with the slats extended.

However two previous failures of the clutching mechanism left the autopilot incontroll and moving the rudder and pedals even though the autopilot was completely disconnected (disconnect buttons pushed, paddles down, autopilot still moving the rudder pedals, aircraft wildy yawwing back and forth)



Cheers
Wino

[Traffic]

Wino

You're clear description of the A300-605 sytem is frightening to say the least.

It would logically follow that anyone with 1,000 hours on the type would avoid even tickling the rudder pedals if at all possible.

To suggest that there were multiple inputs of opposite rudder is to imply a suicide conspiracy which is clearly nonsensical.

What has been done by type operators and Airbus in the meantime to address this issue?

[Tree]

TO: moggie

"But there was no grounding of the B737 for rudder hard-over (at least two fatal crashes)."

True, but despite the rudder hard-overs none caused the fin to fail and that is the important issue here that should and must be resolved. Also the 737 problem was an extremely difficult mystery to solve and it was only through many years/decades of effort by ALPA that the truth was discovered and the blame shifted from the pilots. There appears to be no mystery to the A300 problem and safety must be above jingoism in this industry.

[wes_wall]

Wino

Agree, according to AirBus, they stated that the correct procedure for extending the gear was the alternating rudder inputs you refer. I would assume gear extension speed is something short of 250K, but could certainly be high enough to cause potential structural damage if excessive rudder is applied. Accordingly, what speed restriction is noted for this alternating rudder procedure. During the same exchange, AA indicated their procedure was to bank the airplane rather than yaw.

[Wino]

Yes we modified the procedure to increase g loading via coordinated turns (bank the aircraft) to try and extend the gear and get the overcenter locks that way. It is not a good solution however, just the best we can do.

If there was some sort of major problem that forced us to be clean at the same time (can't be total loss of hydraulics because would make the aircraft unfliable, but you never know multiple failures DO happen) green dot would be around 235 knots or so at max landing weight, so we would be doing the gear extension procedure up around that speed.

Furthermore, as it is an unusual procedure that requires moving your seat and sticking a handle in the ground and turning it some recommend doing it in the holding pattern or before the approach. Again, 235 knots or so is a good clean maneuvering speed with a full load of pax and not much fuel.... If it was a return after takeoff (no dump for upto 120,000 lbs of fuel) green dot could be well above 250.

Airbus posts no speed limit other than the normal gear door limits (270 knots) and says nothing about slowing down to apply rudder. The manual says the rudder load limiter will protect us in its description of the rudder load limiter.

Cheers
Wino

[LJDRVR]

Very useful information here. Safety is well served by honest public discussion and debate. I've several thoughts here:

Airbus certainly has no monopoly on less than stellar behaviour during post accident certification issues. One only needs to remember how Boeing responded during the Palm 90 investigation, particularly in regards to pre-loading and flying various mathematical models for leading edge contamination on the sim prior to turning it over to the NTSB. (Nance 1986)

I'm not much on aerodynamics, but does'nt AOA have a direct relationship on which control surface provides the most roll authority? At higher AOA we reach a speed where the aileron/spoiler create less of a rolling moment than the rudder. (Crossover speed) As has been pointed out, we do not yet even know if the crew used the rudder. I mention crossover speed to the never-use-the-rudder crowd. I know some of you folks have a lot more flying time than I do, but do you really think you're going to recover an aircaft at >90 degrees, loaded up without carefull but firm use of both forward stick and full rudder followed by coordinated aileron spoiler?

United had an A319 in December of 1999 that had a number one uncontained failure in a 800' 25 degree left turn. The AC rolled to 45 degrees. the Captain (ex-fast jet type) unloaded to 1/2G and STOOD on the right rudder. I'm not familiar with what envelope protection the A319 would have provided him rudder-wise, but he recovered with 200 AGL. I bring this incident up because I think we as an industry are not yet in agreement on what constitutes appropriate use of rudder during an upset. Based on incidents such as this one, how can you say that aileron/spoiler only would have been appropriate? I simply don't see how he could have recovered without aggresive use of the rudder. I don't bring this up to insult anyone, I'm here to become a better educated aviator. Can anyone in the never-use-the-rudder crowd please explain to me how their philosophy relates to crossover speed? At high G/angle of bank situations we have little roll capability. I'm going to do whatever gets the lift vector point up quickly. RUDDER.

On a less related note concerning the 737 un-commanded yaw controversey: has anyone seen the Boeing 737 footage of the wing tip vortices encounters they flight-tested behind the FAA's 727? With autopilot disengaed and no hands or feet on the controls, there was a +70 degree upset. Both the Pittsburgh and Colorado Springs accidents recorded roll rates well in excess of what deliberate, full deflection aileron and rudder inputs would have resulted in. Food for thought.

There are aviators far more talented than I will ever be, who for one reason or another got to meet Elvis. There but for the grace of god go we.

Cheers,

DAN

[wes_wall]

"Airbus posts no speed limit other than the normal gear door limits (270 knots) and says nothing about slowing down to apply rudder. The manual says the rudder load limiter will protect us in its description of the rudder load limiter."

Wino

Thanks for the above. That is exactly what I expected, and while there was some back and forth comment, I am surprised that AA or the Pilots Assn. did not really hold Capt. Jacob’s feet
to the fire during his testimony. How can he infer fault with rudder movement when their own procedure call for similar actions? Is one to believe that on a Bus slide slip and yaw is acceptable and safe when wrestling with a gear problem, but taboo if used to aid in arresting an upset condition involving roll. Where and how do you draw the line. AA seemed to be saying that their SIM training suggested active rudder use due to the degree of roll airman are put into, 90 degrees. I never did understand why and where AirBus found fault with this procedure, other than their position that the SIM did not accurately reflect real world conditions at that AOA.

[PickyPerkins]

Some impressions from listening to some of the 2nd and 3rd days of the AA587 NTSB hearing, and later looking at some of the on-line material (http://www.ntsb.gov/events/2001/AA587/exhibits/default.htm) including the “Reconstruction video” of the flight.

Reconstruction video: This shows “pictures” of the plane and the attitude indicator, together with graphic displays of positions of the rudder pedals and rudder, as well as the vertical and lateral accelerations of the a/c, all derived from FDR data. One of the most interesting features (to me) is that you can see the operation of the yaw damper/auto-coordination system on the ground. As the a/c exits the taxiway it does a 180º right turn onto the runway, during which the rudder deflects left without the rudder pedals moving, i.e. the system thinks the a/c is yawing right (nose right) and tries to correct. When the a/c holds (stops) on the runway the rudder makes a large deflection right which then slowly decays to zero, again without the rudder pedals moving.

During the first wake encounter the rudder makes only tiny movements. Evidently feet were on the pedals but they were used with great restraint.

The second wake encounter is extremely short, about ten seconds from start to fin separation. Its so quick that its hard to see exactly what happens, and I have not found any way to slow the video down. In contrast to the first encounter, extreme coordinated yoke and rudder movements are used almost from the start. The delay between a rudder pedal movement and the consequent rudder movement can be seen. The delay is apparently due to digital processing. It was stated in the hearing that pilot induced oscillations are always more of a concern in fly-by-wire a/c because of this delay. The delay usually has to be reduced to less than 1/10 second. It was also stated that with PIO it is possible to reach limit loads in two cycles and ultimate loads in four cycles.

Vertical Motion Simulator: FDR data are used to back drive a simulator specially suited to reproducing large-amplitude vertical motion. The observers noted that on take-off from JFK 31L the runway roughness was much less than they knew it to be from experience, probably due to the filtering of the FDR data on the a/c and/or limitations in the simulator. They thought the encounter with the first wake felt like a wake encounter. In contrast, they did not feel anything in the second encounter that would justify the extreme yoke and rudder pedal movements recorded. They described these movements as being more typical of an avoidance maneuver.

Wakes from JAL47: The atmospheric conditions were favorable for stable wakes, and it was estimated that 63% of the original energy was still in the wake in both encounters. However, the maximum velocity was estimated to be only 10 m/s (about 20 kts), and too low to be of any concern to the a/c structure. The a/c crossed the wakes at very narrow angles, so that it was almost flying along the wake. One structures witness stated he was not aware of any study of the effects of wakes on structure while in a yaw.

FAR25: It seemed that everybody worked from the regulations only. The FAA decided in the 1950’s that there had to be some standards as to what a/c have to be able to do in order to carry people about, and started to list certain maneuvers, which become the “envelope”. Because manufacturing a/c is a competitive business, manufactures design to this “envelope” and little more, or they will not be competitive. The aircrew are then assumed to stay within the envelope. This whole approach was best illustrated by the first sentence of Mr. Winkler’s prepared presentation, “The most important thing for an a/c structure is that it should be strong enough to resist all load conditions as required by FAR25”. He did not say “strong enough to withstand possible loads“. The same with maintenance. Anything which happens outside the envelope is “non-scheduled maintenance”, e.g. being hit by a truck on the ground. I am not commenting on this, just stating everybody’s attitude.

One question posed to the hearing but not directed to any particular individual was, “how can we continue to certify an a/c which can be broken by use of its certified flight controls?”. The answer given was along the lines that it has always been the case that a/c can be broken by use of the pitch controls. The pilot has always been expected to stay within the pitch envelope. It struck that this is like the case of a bus - you rely on the driver not to drive over a cliff. But perhaps a better analogy is a ship, where a storm may put you on the rocks whatever you do. But at least a ship Captain does not expect the rudder to fall off if he goes “hard a port”. (Continued in the next post.)

One the most interesting (to me) on-line documents is an (undated) talk (http://www.ntsb.gov/events/2001/AA587/exhibits/240005.pdf) by Captain William Wainwright, Chief Pilot of Airbus Industrie. I have no idea if this is old or recent. Here are some extracts. The omission of text in these extracts is indicated by “………”.
--------- Start of quote extracts -----------
AIRPLANE UPSET RECOVERY TRAINING AID, By Captain William Wainwright, Airbus Industrie.
INTRODUCTION
The idea for a joint industry working group to produce an Airplane Upset Recovery Training Aid was first proposed by ATA in June 1996. ,,,,,,,,,.The end result of 2 years work is a training package including a video and a CD-ROM, giving an airplane upset recovery training aid. This package is on free issue to all of you, to use or not to use as you wish. ………..The content of the package is not my subject today, but there are a few issues of general interest which I gained from my experience as a member of the working group which I would like to talk about.
2. THE BEGINNING
…… Right from the beginning there was a conflict between the technical advice given by the manufacturers' training pilots and that expressed by those of the principal airlines already practicing upset training. They naturally considered themselves to be the experts on this subject, based on the many .hours of training that they had already conducted on a large number of pilots in their simulators. At the beginning of 1997, the Flight Test Departments were asked to come in to support their training pilots. From then on, the chief test pilots of the 3 major manufacturers became members of the working group; XXX of Boeing, YYY of McDonnell-Douglas (now Boeing - Douglas Products), and myself. But the conflict over the different opinions on aircraft handling and recovery techniques continued for a long time until we finally achieved agreement at the last meeting in January 1998. The reasons for these differences of opinion are the subject of my talk today.
3. THE DIFFERENCES
The differences of opinion were mainly concentrated in the following areas:
(a) Procedures versus general advice.
(b) Ease of training versus failure cases.
(c) Stalling.
(d) Use of rudder.
(e) Use of simulators.

It is worth saying that there was never any difference of opinion between the 3 test pilots on the group. Although we come from different backgrounds and have worked in different organisations with different work cultures, we always agreed on our technical advice. ………………………..
6. STALLING
Another aspect that was being ignored in the existing training was the stall. ……… However, the technique being taught only works if the aircraft is not stalled. ………….This is something that we are well aware of in testing, but it was either being totally ignored, or misunderstood. I consider the inclusion of this note to be one of our most important contributions. ………

7. USE OF RUDDER
We also spent a lot of time discussing the use of rudder. The existing training courses all emphasised using rudder for roll control at low speeds. It is true that the rudder remains effective down to very low speeds, and fighter pilots are accustomed to using it for "scissor" evasive manoeuvres when flying not far from the stall. But large airliners, with all the inertias that they possess, are not like fighter aircraft. Based on our experience as test pilots we are very wary of using rudder close to the stall. It is the best way to provoke' a loss of control if not used very carefully, particularly with flaps out. We finally got the training managers to agree to play down the use of rudder in their existing courses. But we do not say never use the rudder at low speed. We say that, if necessary, the aileron inputs can be assisted by coordinated rudder in the direction of the desired roll, We also caution that "excessive rudder can cause excessive sideslip, which could lead to departure from controlled flight".

But why did we have so much difficulty in convincing the training pilots that it is not a good idea to go kicking the rudder around at low speed? Their reply was always the same; “but it works in the simulator“. This leads me on to my last point.

8. USE OF SIMULATORS
We manufacturers were very concerned over the types of manoeuvres being flown in simulators and the conclusions that were being drawn from them. Simulators, like any computer system, are only as good as the data that goes into them. That means the data package that is given to the simulator manufacturer. And we test pilots do not deliberately lose control of our aircraft just to get data for the simulator. …………..

The complete data package includes a part that is drawn from actual flight tests, a part that uses wind tunnel data, and the rest which is pure extrapolation. If should be obvious that conclusions about aircraft behaviour can only be drawn from the parts of the flight envelope that are based on hard data. This in fact means being not far from the centre of the flight envelope; the part that is used in normal service. It does not cover the edges of the envelope. I should also add that most of the data actually collected in flight is from quasi-static manoeuvres. Thus, dynamic manoeuvring is not very well represented. …………

In other words, you have reasonable cover up to quite high sideslips and quite high AOAs, but not at the same time. Furthermore, the matching between aircraft stalling tests and the simulator concentrates mainly on the longitudinal axis. This means that the simulator model is able to correctly reproduce the stalling speeds and the pitching behaviour, but fidelity is not ensured for rolling efficiency (based on a sirrpfified model of wind tunnel data) or for possible asymmetric stalling of Ihe wings. Also, the engine out range is much less than !he all engines operating one, and linear interpolation is assumed between low and high Mach numbers. Wind tunnel data goes further. ,,,,,,,,,,,,,,,,,,,,

In fact, this is a perfectly adequate coverage to conduct all normal training needs. But it is insufficient to evaluate recovery techniques from loss of control incidents. Whereas, the training managers were all in the habit of demonstrating the handling characteristics beyond the stall; often telling their trainees that the rudder is far more effective than aileron and induces less drag and has no vices In short, they were developing handling techniques from simulators that were outside their guaranteed domain. Simulators can be used for upset training, but the training should be confined to the normal flight envelope; For example, training should stop at the stall warning. They are "virtual" aircraft and they should not be used to develop techniques at the edges of the flight envelope. This is work for test pilots and flight test engineers using their knowledge gained from flight testing the "real" aircraft.
--------- End of quote extracts -----------

Several test pilots (some USA) made the point (if I understood them correctly) that pilots do not make control inputs of set amounts. They make a control input and wait to see what happens. On the basis of the result they then make another input. And so on. They do not just stamp on the pedals. So to some extent it may be argued that it should not matter what the rudder travel gearing is. Certainly the Airbus Industrie engineering test pilot witness said he was very happy with the present system. On the other hand it seemed to me that events in the reconstruction were happening so fast that a “try-it-and-see" approach wasn’t really possible.

If you got this far you may be amused by a comment by one of the simulator instructors being questioned about the psychology of instruction who said, “I know that pilots have a pretty short attention span, and if you have a point to make you had better get it over early”. This same interviewe said that simulator instructors have no way of telling which behaviors of the simulator are based on data and which on extrapolations.

These are just some personal impressions of the hearing. I was not there. :)

[Tan]

PickyPerkins


Your article has to be one of the most informative rudder discussions that I've seen so far. All the years that I spend flying both Boeing and Airbus aircraft and no one ever told me that a rudder could actually separate from an aircraft. Maybe the industry didn’t know or didn’t think that it could happen.

A few years back, I did attend, an Airbus equipment meeting with Airbus test pilots and was surprised how their opinions differed on the interpretation of some of the FMGS information presented on the Airbus aircraft.

It seems that we have a lot more to learn about how airplanes fly...

Cheers .:)

[411A]

Interesting comment about sim instructors...and the rudder.
Suspect that part of the problem is all the old guys have retired and gone to heaven, and the lessons learned a LONG time ago about abrupt maximum rudder use have been forgotten.
Good friend of mine, now retired L10 fleet manager at DAL mentioned that when he joined the airline (was a former Marine pilot), one of his older instructors mentioned ..." be gentle but positive with the rudder." Same for me at PanAmerican, long ago.
Newer guys need to be reminded.

[Few Cloudy]

There seem to be two inter-related but separate subjects here:

- Should the rudder ever be used to max deflection?
Answer - If neccessary (but this presumes a unidirectional input).

- Should the rudder ever be cycled?
Bearing in mind the gear locking procedure quoted above, the answer must be - One side at a time and then wait in neutral - a continuous cyclic movement can well lead to the separation concerned. (And by the way, a "coordinated turn" won't help the gear locking - because the ball will be in the middle).

We all need to learn more about the use of the rudder - it's a friend if treated right and a fiend if not.

[Wino]

411a

That quote is what we heard at AA (contrary to Airbus statements and hooplah).

A few other points about the NTSB hearing. THere were some ground rules laid out by the new chair of the NTSB before the hearing which directly restricted the APA's ability to defend their pilot.

I have forgotten the woman's name at this second in time, but she doesnt know anything about airplanes. I hope she knows something about trains and can help out in a train accident because she was worse than useless in this case. One of her ground rules was "I will not let you turn this into an advertisement for beoing." which makes an excellent sound bite.

The problem with this is that AA is the largest airline in the world 800+ jets off 100,000 lbs or greater, and thus has an ENORMOUS body of experience in operating aircraft. More than most countries of the world. Airbus was directly attacking the way that AA operates aircraft and trains their pilots. If it was the training that was the problem, then there should have been other incidents of aircraft exceding design or ultimate loading. And yes there were. There were a total of 7 incidents of aicraft exceding design loading and 2 incidents of aircraft exceding ultimate loading (including 587) on the tails over the last 20 years. The problem is that they were ALL on the airbus fleet of 35 aircraft, and none on the 727/737/757/767,777,MD80/MD11/DC10/DC-9/F100.

That is not a statistical abberation and indicates there is nothing wrong with the techniques employed by pilots in line operations except on one aircraft type. That means there is a problem with the aircraft type, not the pilot corps. Furthermore we were able to identify other incidents in other airline fleets that were simliar to ours. But as this was not to be an "advertisement for boeing" we were forbidden from introducing the evidence.

As to the rudder movements during the first wake and the second wake. It is very likely that during the first wake Sten did not excede breakout force on the rudder pedals, hence the no movement. You may think you are making an application but because you are beneath breakout force you are not, but since the ailerons are still doing the job and the aircraft is going the direction that you expect it to, no further pressure is required. In the second wake he definately exceded the breakout force (probably for the first time in all the years he had been on the aircraft) and the result was not what was expected as the rudder is guaranteed to go to the stop and then all hell breaks loose.

There was also testimony from airbus as I recall that it was possible to go through the rudder load limiter if enough force was applied, which had me "gobsmacked". The only time you should come up against the load limiter is in the heat of battle, and then it should be protecting you from yourself at that point. Hence the whole point of a rudder load limiter . I dont know about other pilots, but in the heat of battle this pilot has an adrenal gland that might make me somewhat stronger than normal.

Cheers
Wino

[Captain104]

Looked into some threads started in PPRuNe during past year all dealing with AA 587.
Interesting.
Some contributions a bit far from reality, some more emotional
posts motivated more by sympathy for the poor crew or the company involved rather than dealing with facts. And than those brilliant tech. theories or explainations indicating profound system
knowledge and competence.(i.e. BELGIQUE, JOHN TULLAMARINE and others).

In a thread "witnesses saw AA 587 exlpode in flames" JAN2002
I wrote:
"I dare say during the next weeks the profs will circle again around those AA-Procedures you all heard about: the recovery out of unusual attitudes by applying full rudder. Believe me, the Airbus A 300-600 got a huge one and after takeoff you better get your feet off the pedals."
Reaction was not very friendly: "Captain of a C150 me thinks"
Or MCD wrote that application of "full rudder" was not the point.

Reading BOINGS post in this thread:
"The US airlines with whose training I am familiar have all been teaching inappropriate rudder use in upset recoveries for about five years. It did not start as excessive use of rudder. Initially the teaching was that an "appropriate" amount of rudder would be used to aid recovery. Over the years "appropriate" slowly evolved into "full" use of rudder. It was easy to see this transition take place sitting in the left hand seat during simulator check rides. My objections that excessive rudder was being used were ignored by the training system"

and following the nice informative post by PICKY PERKINS (thank you) I'm rather shocked that some forgotten oldfashioned pilot habits could have caused or contributed to this tragic accident.

411A in his charming manner is quite right: in big commercial airliners easy on the rudder.

BTW N380UA: when I was sitting LH on a A300-600 or A310 years ago recycling FAC CB (pull-push) to reengage pitch trim or YD was daily bread and butter routine. The FAC "needed" it sometimes. ;)

Regards

[moggie]

Accepted - the B737 hardover did not cause fins to fail but it did cause fatal crashes.

Boeing said "there is no problem" but published a recovery technique and then redesigned the rudder for the B737 NG - pretty telling for "no problem".

I am not saying Airbus are perfect or Boeing cr@p - just trying to point out the one-sided arguement. Why should european airliners be grounded if they have problems but American ones keep flying? Could we be talking bias here?

Any crash is a tragedy and should be investigated fully but the truth will only emerge if that investigation is both neutral and open minded. We learn from our errors and if carbon fibre tails are found to be inappropriate then action will be taken.

Concorde has been worked on and the problem sorted ou, the Comet was fixed (and still flies safely today as the RAF's Nimrod), Boeing have reworked their 737 PFCU and I expect that they will sort out the "exploding" fuel pumps, too.

I feel that there is a tendency to turn the blind eye to faults on American products if you live west of 30W - after all, Ford and Firestone said that the Explorer was fine!

[Wino]

So moggie,

Though boeing said no problem, they atleast did something. Airbus's reaction to the 737 crashes if they were airbus aircraft would simply be that its the pilot's fault.

Tell me what airbus has done? That is the problem. They just said, the pilot did it and there is nothing wrong with the plane and done NOTHING ELSE!

This is not a protectionism debate. I know that no airplane is perfect. However, it is airbus's position that no crash has been anything other than the pilot's fault. That is the problem that they refuse to address.

Airbus could fix the rudder load limiters fairly easily by either further limiting the rudder at high speeds (simply a software change, which would effectively prevent this from ever happeneing again) publishing limitations that are far more accurate than what is published now, or reducing the breakoutforce and or increasing the force to reach the stop at higher speeds (again a software change to reduce the chance of a Pilot Induced Oscilation).

You in your complaint against airbus bashing which you claim to be based on where you live ably pointed out the difference between the two companies. Boeing did something. Airbus did not, even though they knew about the problem atleast 4 years in advance.

Cheers
Wino

[arcniz]

Are we learning something from this?

I am really disturbed by the practices described in anecdotal comments about recycling the breakers for YD, pitch/trim, FIC, etc. From these remarks, one can infer that this practice is common, normal, and sometimes considered necessary.

This may be a case where 'old-time' practices have been carried forward without much-needed examination for relevance and safety.

As a pilot, I am familiar with the decision process that leads to go/no-go decisions when some piece of MEL equipment is 'a bit flaky' but seems essentially sound: If you can inspire it to work in a perceptibly proper manner, you sure want to do that rather than scrub the flight. I am also very familiar with the tweaks and prodding sometimes required to fully awaken an aircraft from a cold / hot / long / damp sleep.

But as a computer architect, controls maven, and systems guy, it scares the stuffing out of me to think that repeatedly cycling primary power to mission critical systems - when the systems are balky on startup - is a popular cure-all in operations with "modern" aircraft.

The "modern" qualifier is meant to distinguish between older aircraft systems that were often controlled by relays and other mechanical contactors, versus newer ones that are principally implemented and controlled by electronic circuits of a much more complex nature. In the days of relays, cycling power repeatedly was a crude but effective way to break through oxides on the contacts and to free up stuck or slightly welded contacts on mechanical actuators.

In these modern days of electronics everywhere, cycling power a lot on systems is just a way to make them wear harder and fail much sooner than they otherwise would.

Not only that, the inability of an electronics-implemented control system to function *PERFECTLY* on the first power-up means either

a) it was designed wrong,
b) it (or something attached to it) is broken,
or c) both.

This is especially true for computer / microprocessor-driven systems - which most of the referenced ones appear to be.

If a system has to be recycled four times before it operates correctly, that really means the system probably is only working ok a mere ten percent of the time at initialization, (if I remember the statistics computation). Further correct operation is far from a sure thing. To emphasize the seriousness of this, one need note that initialization is, by design, normally the MOST reliable process in the operation of electronic control systems, so general operation may immediately be less reliable than the startup.

Tolerating faulty systems - in the aero controls especially - really introduces a wild card into the understanding of whatever happens afterward.

In what other aviation context would one *commence* flight with a critical system known to be working incorrectly more than half of the time ???? !!!!!!!! Not many, I hope.


Footnote: A practical procedure I would suggest, consistent with the above: If a system is not operating properly on power up, and smoke is not billowing forth, then leave power on awhile and give it an appropriate time to warm up. Then pull the breaker, count to 10, and repower it. If still inoperative, write it up, with bells.

[Captain104]

arcniz:
Your footnote-procedure sounds reasonable and proves common sense. That's what I was talking about. (plus or minus a second?) ;) Agree with you completely:there is no sense in resetting a CB more than once and there are CB's in a modern Airbus or Boing I wouldn't touch without recommended by maintenance.
My remark above was referring to some speculation about AA 587 where the crew called maintenance due to disengaged YD/PT switches. They recycled FAC-CB prior leaving the ramp at JFK. All I meant was: probably nothing unusual, just routine.
BTW a FAC is not a FIC. A FAC is just a flight augmentation computer. ;)

[Kefuddle_UK]

I strikes me, reading all the very many informative and relevant views that have now permiated this thread, that Airbus and Colin Chapman have alot in common.

The fact that Airbus have built a plane that can be mistreated to the point of destruction by the pilots by simply moving control surfaces in an inappropriate manner gives me the hebe gebbies! That just sounds absolutely rediculous. But I don't get this general feeling from this thread. Many of you seem to think that the pilot should not have used the rudder in such a way in the first place (not saying people are blaming the pilot...training issue). I say regardless of how the pilot flew the plane, it has been designed to carry 200 people over crowded densly populated areas. If a fin fails because of loading issues then that is a design problem pure and simple.

Is the A3X0 series just like a Lotus 49? Superbly equiped to do the job in-hand, extremely efficient but extremely fragile?

[Tan]

Wino

Quote: "Tell me what airbus has done? That is the problem. They just said, the pilot did it and there is nothing wrong with the plane and done NOTHING ELSE!"

I remember when my airline first introduced the 320. Airbus maintained that their aircraft was perfect. After many frustrating years Airbus finally started to listen to their customers and modified the arrogant manner in which they treated them. We all thought it was just the European (read French)way. But now they seem to have returned to their old ways.

The bottom line: A tiger doesn’t change its stripes

[moggie]

Airbus may have their head in the sand - but Boeing did the same with the rudder and are still doing it with the fuel pumps. It too a lot of effort to get Boeing to fix the rudders (or even admit to the problem in the first place).

Maybe Airbus and Boeing are reluctant to admit problems if they are worried about getting their @rses sued off in the ludicrous American legal system. that is why Piper stopped producing aroplanes for some years - product liability litigation.

[Wino]

Moggie!

You still don't get it. We could argue all day long about whether or not Beoing CHANGED the rudder fast enough, and it would be a valid arguement.

But what beoing did do, is as soon as the problem was documented they speeded up the approach speeds for the 737 so that a hard over would no longer mean a loss of the aircraft and published a procedure to deal with the failure. With the fuel pumps they again published a procedure to deal with the problem untill it could be fixed.

Airbus on the other hand has known for years that there is a problem with the A300 tail. They could have at the very least published a limitation, or a restriction on doublets. They did no such thing!

That is an absolute fact that you cannot dispute. And as a result 265 people are gone. Airbus did not make even the slightest effort. If you think boeing is poor, then by your standards airbus is worse! Your inability to see that makes you the biased protectionist one.

Cheers
WIno

[411A]

So then, IF some of the opinions here are more or less factual, Airboos has a lot to answer for.
Wonder IF they will face the music?...or, if the French have their collective way, all will be swept under the carpet.
Many concerned are waiting and watching.
One thing for sure, the lawyers will make a bundle.

[GlueBall]

Curiously, as to the alleged excessive rudder inputs by the flying F/O: One AA captain had come out of the woodworks and testified to the NTSB that he remembered one particular incident when this F/O at an earlier time had applied multiple excessive rudder inputs while at the controls of a B727. This F/O was said to have rapidly cycled the rudders to nearly full deflection during one mild wake encounter at low altitude. The F/O had explained to this captain that his action was as per the AA "Advanced Maneuvering Program," ...whatever that may have said. The captain stated that he had vivid memories of this event as this was the only F/O who ever did this.

[Anthony Carn]

Kefuddle_UK

Don't know if you're a pilot, but all of the commercial aircraft that I've flown COULD be mistreated to the point of destruction by "simply moving control surfaces in an inappropriate manner", hebe geebies or not.

That's why we learn pages of limitations for each type we fly and observe them if we wish to survive. Further limitations are imposed by safe flying practices and it is these which apply to the case in question.

I repeat the warning that anything other than small rudder inputs in co-ordination with aileron, when recovering from unusual attitudes, may lead to overstressing of the fin, certainly on ANY of the types that I've flown ( medium twin jets ).

IMHO

[Huck]

Glueball-

If that captain has memories of the right guy, that would be the biggest piece of news I've heard in this investigation. I wonder if he wrote up the incident at the time?

[wes_wall]

I would think Glueball that if you want to post "a particular incident" involving one of the airman, that you get your facts completely correct, and if you cannot, then may I respectfully suggest you refrain from suggesting something based on an "alleged" story. IF there is anything to your allegation, it will most certainly be included in the NTSB findings.

[Captain104]

wes_wall:
It's all in the papers. Please read and check.(NTSB) ;)
http://www.ntsb.gov/events/2001/AA587/exhibits/239990.pdf

Regards

[GlueBall]

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.

[Few Cloudy]

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.

[PickyPerkins]

-----------
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 (http://www.aviationnow.com/media/jpg/587dfdr2.jpg).

[wes_wall]

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.

[PickyPerkins]

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 (http://www.ntsb.gov/events/2001/AA587/exhibits/240009.pdf) 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.

[Few Cloudy]

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.

[Wino]

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 (http://www.ntsb.gov/events/2001/AA587/NTSB_reconstruction587.wmv) . 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

[Mac the Knife]

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.

[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.

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?

[PickyPerkins]

=========
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 ...".

[wes_wall]

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?

[Wino]

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

[whatshouldiuse]

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

[Bubbette]

I just heard on the local (New York) news that a plane of the same type just turned back to JFK because the pilot felt something wrong.

[PickyPerkins]

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.

[Wino]

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

[wes_wall]

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.

[PickyPerkins]

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.
---------------
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.

http://home.infionline.net/~blueblue/_uimages/Pedals.gif

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)?

----------
Wino …. nor could Captain States have known that he was banging off the stops. …
----------

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?

----------
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.

[RatherBeFlying]

Given that the rudder pedal breakout force is close to that required for full deflection (all of 1.3 inches:eek: ) 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 (http://www.aussiegasstrutcompany.com/) as they offer custom engineering in low quantities.

[Wino]

Both could be overpowered as I recall. That was one of the points where "I don't understand the question" started to rear its head.

I can't screen capture like you can Picky, but the next reversal, before the bang and tail departed had both exceding the movment limits.

Also the traces have the yaw damper doing its thing ontop of the movements...

As to Captain states, every time I flew with him he always followed along on the controls. The problem is that even if he was on the controlls as there is no indicator to point to the reduced rudder pedal travel available. So Ed would have seen or felt the rudder pedal moving 1.3 inches or so, not the 4 inches when they did the rudder check right before take off, so the movements would APPEAR to be quite restrained. Without stepping on the pedals with additional force himself, there is no way he could know that pedal progess was stopped by the load limiter rather than restraint on the flying pilot's part.

I would guess that about 60-70 percent of pilots follow along on the controls. I know I do when the other guy is flying, and the majority do the same, though not all. Oddly enough it is something that is not possible in later Airbus aircraft where the controls are not back driven or interlinked.

You are correct, they were not yet in a turn for the first wake encounter, I over looked that in my far closer focus to the second wake encounter. Good catch.

Ratherbeflying.
That is a manufacturer problem unfortunately. You can't just willy nilly alter an aircraft design without certification which requires the cooperation of the manufacturer. As Airbus feels they have never made a mistake, I doubt they would cooperate.

Cheers
Wino

[RatherBeFlying]

Wino, between AA's engineering department and the FAA I believe there's enough expertise to develop an AD.

Having made my own changes to OEM computer code, I do understand that modifications, even those that bring the product to published specification, generally receive a cold reception from the OEM.

[Wino]

Not so easy.
If the manufacturer pulls their support, your aircraft are effectively grounded. Airbus had threatened to do that to the 12 Airbuses 340s that boeing bought back from Eva Air, but thought better of it at the last minute because of the larger number of Boeings they buy back in their deals.

Unfortunately we are not talking about an AD here. We are talking about a modification (An AD is usually an inspection or a repair) which would require an STC (Supplemental Type Certificate) If airbus doesn't play ball then the aircraft are grounded forever.

CHeers
Wino

[Techman]

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.

Is that statement based on experience or assumption?.

[Wino]

experience. You get the 32 pounds of force at the opposite stop pushing the stuff back towards center plus the weight of your leg moving in that direction. Put your leg on the scale and see what it weighs. Once it gets moving, it will go right through the center pretty easily (as compared to breaking it out in the first place) and allow you to get to the opposit stop.

The Sims did not represent that too accurately before. They do now. Its shocking.

If you take your feet off both pedals it will stop at the stop. If you try and go back and forth, you lose the center position pretty quickly. Going from Full left to Full right is much easier in feel than going from neutral and getting the pedal moving.


Cheers
Wino

[PickyPerkins]

---------
Wino I can't screen capture like you can Picky, but the next reversal, before the bang and tail departed had both exceding the movment limits.
---------
Technically you are right, the rudder is shown in the Reconstruction video (Rv) immediately before the fin separates as being a bit outside the limits.

http://home.infi.net/~blueblue/_uimages/FinBreak.gif

Above are two frames taken within the same second at 09:15:58, the top one before the fin separates and the lower after the fin has separated. The rudder is shown as being just outside the limits in the top frame, and gone in the bottom frame.

However, looking at the (unfiltered) FDR trace, I am not sure that we really know that it did go out of limits.

http://home.infi.net/~blueblue/_uimages/Cutout.gif

Here is the FDR rudder position trace during the second wake encounter. Positive (downward) deflections on this graph correspond to deflections of the rudder to the right on the a/c. The first point outside the limit is at a rudder deflection of -115º, and hence is clearly during/after the fin separation. The three later points are all at zero, presumably representing a disconnected circuit. Since the point before the -115º reading is also zero, it may also represent a disconnection and not be valid. All the other points are at or within limits.

So I don’t see any evidence that the rudder really went out of limits in this case.

Curiously, you can see above that the last points on the (unfiltered) FDR trace before the -115º point are at about 6º right and zero, whereas the last frame of the Rv before fin separates shows the rudder deflected to the right limit (or slightly more). I imagine the Rv uses estimated unfiltered rudder positions, so that to some extent the Rv rudder positions are synthetic (and of course the FDR readings are “wrong” because they are filtered).

I think that this all adds up to there being no evidence that the rudder really went out of limits in this case.

I have a question: did the process of estimating the unfiltered rudder positions ASSUME that the limiter worked?

If anyone has a transcript of the NTSB hearing, I would be interested to hear Airbus’s exact words on overpowering the rudder and/or its pedals.

BTW, I can’t screen capture video either. All these video frame illustrations are digital photos of the monitor screen. :)

I agree with your comments about Airbus’s attitude at the hearing. One of the most disturbing impressions I got listening to parts of the NTSB hearing was the complete satisfaction of the Airbus engineering test pilot with the present rudder system. He was completely happy with it. There was also a complete conviction expressed that anything not specifically required by the FAR’s wasn’t necessary. (Like displays if you are out-of-the-envelope in a 65º bank?) Guess he was wearing the company hat that day.

[wes_wall]

Unfortunately, I don’t think a written transcript has been published on the net yet, however, the audio/video can still be played. Germaine to the above posts is the testimony of Capt Armand Jocob, test pilot for AirBus. On the salient points raised here, his comments and reply, to me, boarded on being arrogant, evasive, and totally protective. If you have the time, go to the
archives section, and you can check out his testimony here:

http://www.ntsb.gov/Events/2001/AA587/agenda.htm

[bookworm]

Before the investigation of this accident, I had never encountered the concept that control reversals might break an aircraft even at less than the manoeuvring speed, and had the mistaken impression that this theme was a relatively new concern.

I was browsing some NACA reports last night and came across Consideration of dynamic loads on the vertical tail by the theory of flat yawing maneuvers (http://naca.larc.nasa.gov/reports/1946/naca-report-838/).

It concludes that a sinusoidal deflection of the rudder reaches the design limit of the aircraft much more easily than step or impulsive deflections. It was written more than 55 years before AA587 lost its fin.

[PickyPerkins]

Bookworm - NACA "Consideration of dynamic loads on the vertical tail by the theory of flat yawing maneuvers"
Congratulations! What a great find!

I found the underlinings in another version (http://naca.larc.nasa.gov/reports/1946/naca-tn-1065/index.cgi?page0005.gif) of the report interesting!

This report does not seem to be amongst the NTSB on-line documents. I wonder if the NTSB/NASA were aware of it. Full rudder "fishtailing" was described at the NTSB hearing as having happened and discussed at length, but no mention of this report.

If I understand the last para before the conclusions correctly, a prevoius US Army Air Force report had already studied the effects and dangers of "fishtailing" the elevator. As I mentioned in a previous post, a current Boeing document warns against "fishtailing" any of the controls.

It was common in the 1940's for large a/c to have twin or triple fins. Was that done for structural reasons? What about current twin-finned fighters?

Once again, a great find! :)

[PickyPerkins]

During the NTSB hearing on AA587 last November, the NTSB Investigator-In-Charge Robert Benzon included the following in his opening statement (http://www.ntsb.gov/events/2001/AA587/iic_stmt.htm):

---- Start quote ---
Opening Statement of NTSB Investigator-In-Charge Robert Benzon
Flight Data Recorder problems
…….. In 1994, the Safety Board recommended to the FAA that such filtering systems be removed from information sent to flight data recorders, and yet in 2001 this investigation was hampered by totally unacceptable filtering of FDR data. In addition, the sample rates of data are not adequate. Staff and the Board are addressing these issues separate from this hearing.
---- End quote ---

Can anyone tell me:
(a) Has the FAA since required such filtering systems to be removed?
(b) If not, to what extent have airlines, aircraft manufacturers, or FDR manufacturers voluntarily removed them (particularly from Airbus a/c)?

http://home.infi.net/~blueblue/_uimages/pi.gif

[GlueBall]

Interesting observations and comments about FDR interpretations and video graphics. Nevertheless, I believe that it's imperative not to get overly affixiated about the tiniest recorded parameter of control surface position indication. I'm almost sure that the recorder does not record control surface position every nanosecond.

I'm not a Bus driver, but does the A300 FDR get its rudder data from the surface position indicator? What tolerances does the mechanical or digital surface position instrument have?
Is it conceivable that "limits" could have been exceeded within a fraction of a second that was "skipped" by the FDR?

It's as if one were taking a magnifying glass to check the graphically reproduced surface position indices...to see if ever either exceeded limits. Somewhat like debating at what point would 12 degrees Centigrade become 13 degress Centigrade.

Speaking in somewhat general terms, let me briefly recall the FDR interpretations of the COPA 737 crash in 1992, a loss of control accident in IMC.

The FDR readout had recorded one unusual attitude where bank angle went from something like 60 degrees port to 90 degrees starboard in less than one second. But the airplane could not physically make such a maneuver even in one whole second. The crux of the matter was that the FDR had recorded travel of the ADI which had tumbled.
Just one example of FDR limitations, just to make a point. :cool:

[LOWCONEINBOUND]

Going back to the 737 problems, I'd throw in with the idea that the yaw damper is causing a 'chattering' hydraulic actuator. The damage to the A-300 rudder - versus the fin - rather suggests radical flutter, which induced the failure of the vertical fin attachments. Im guessing a case of 'deuling' actuators took place.

A number of 737 hardover events have been solved by turning off the yaw damper. While that's inconclusive, I wouldn't be too quick to discount the possibility.

[OVERTALK]

A recent (03 Dec 02) American Airlines A300-600 uncommanded yaw event (link here (http://www.iasa-intl.com/folders/the068event/the068event.html))

AND

The Crow Hammer Wake Vortex Effect (link here (http://www.iasa-intl.com/folders/the068event/587crows-1.html))

[Bubbette]

The NTSB has just posted updates on this: http://www.ntsb.gov/events/hearing_sched.htm#021029

[Bubbette]

And now airbus is suing AA over this:
http://www.nypost.com/news/regionalnews/71312.htm


Aircraft manufacturer Airbus has launched a legal claim against American Airlines, blaming it for "improper" flight operations that triggered the crash of Flight 587 in Queens.

[patrickal]

The following report was published on a local NYC radiostation website this morning.

Mar 20, 2003 5:43 am US/Eastern
(AP) (NEW YORK) Airplane manufacturer Airbus says in court papers that American Airlines is to blame for "improper" flight operations that caused the 2001 crash of Flight 587 in Queens, which claimed the lives of 265 people.

"American Airlines failed to operate the aircraft in the manner that was foreseeable and normal or intended by Airbus," Airbus said in court papers filed this month in Manhattan federal court, the New York Post reported in Thursday editions.

"Nothing Airbus did or failed to do caused the accident or any harm or injury to the plaintiffs," the court papers say, referring to the victims of the crash.

An Airbus A300-600 crashed on Nov. 12, 2001, minutes after taking off for the Dominican Republic, killing all of 260 people on board and five people on the ground in the Queens neighborhood of Belle Harbor.

More than 200 legal suits from victims' families have since been filed against American and Airbus.

American Airlines spokesman John Hotard told the Post that Airbus' position was "ridiculous."

The National Transportation Safety Board is still examining why the plane's rudder suddenly began swerving violently, causing the tail fin to break off and the plane to crash.

At a Washington hearing last year, the NTSB presented evidence suggesting the co-pilot moved the rudder back and forth after encountering turbulence from a jet five miles ahead. But it is also investigating whether there was a problem with the rudder itself.

It said it may reach some conclusions by this spring.



http://wcbs880.com/topstories/topstoriesny_story_079054436.html

[jet_breeze]

I completely agree with Airbus American is responisble for the overall condition of the aircraft not Airbus however if this is a general problem with all the production A300 aircraft Airbus will be at fault.

[catch 22]

I see it as a pilot induced problem. Have flown that type for many years and never heard of a rudder malfunction. Most probably a recent ex- military pilot reacting correctly to a military aircraft.

[Wino]

Catch22,

Did you fly the A300-605R or the A300b4?

I fly the A300 for AA, and knew the pilots in question. The copilot who was flying the aircraft was civilian background. The Captain was x military (C 141s) Both had been at American for years and years and were consumate aviators. Neither was in the slightest bit ham handed.

The A300 605r rudder becomes progessively more sensitive the faster the aircraft gets. once you pass 230 knots or so the force required to reach the stop is less than the breakout force. At that point the only choice you have is full application of Rudder. Furthermore more the outboard ailerons were removed as part of the aerodymanic cleanup from b4 to 605R, further limiting roll authority laying the ground work for the Rudder trap.

Other aircraft were found to have damaged tails from similar incidents, even though AIRBUS insisted that visual inspections were good enough.

The A300-605R is THE ONLY AIRCRAFT IN THE WORLD that uses a blocker time (constant ratio) rudder load limiter that does not depower the rudder. So the pedal throws become shorter and shorter making the rudder exponentially more sensitive the faster you go. Most pilots will go their career without needing rudder after they leave the runway. IF you suddenly try and use it in the A300 605R you may kill yourself.

The A300B4 had a ratio changer type rudder load limiter so in that aircraft a full throw was always the same at your feet, although the throw at the rudder would reduce. In the605R blockers come up from the floor that restrict the movement. By the time you are going 250 knots a minute after takeoff full travel is achieved by a 1 inch movement of the rudder pedals vs the 4 inch movement that it took to reach full travel while rolling down the runway.

ITS A TRAP FOR POI.

Cheers
Wino

[NigelOnDraft]

catch 22

I'm glad you know exactly what happened. I'm also glad you know that "ex-military types" fly aeroplances completely differently to civil types (military aerodynamics and structures are, after all, different?).

As an aside, as an ex-military type, IF the "pilot induced" theory is correct, then nothing in my military, or civil training, would induce me to do anything like what it is alleged this crew did (that's type training on light pistons, JPs, Hawks, Harriers, A340/320, B757/767).

JB
<<however if this is a general problem with all the production A300 aircraft Airbus will be at fault>>
Not sure what you are saying here? If the crew carried out actions sufficient to detach the fin, then there is a likliehood this would happen on any A300? How does this then become Airbus' fault?

Please note, I am not in any way blaming the crew. There are 2 theories to this accident:
1. Rapid full/large rudder deflections in opposite directions exceeding the certified load of the fin. If this is the case, then there are also comments that AA had taught aggressive recovery techniques from "jet upsets", and this may have been a factor.
2. Something in the rudder / yaw control system of the aircraft went wrong.

And I suspect nothing will ever really be proved as to which it was...

NoD

[N380UA]

NoD,

Military airfoil and structures are indeed different from that of a civilian type.

I really have not the foggiest on what caused this accident however, should there have been a principal construction flaw I’d expect to have heard of other such incidents before. The A300 is a machine which has been introduced as the first Airbus PAX aircraft in 1974, and has an excellent construction record so far.

Early reports have indicated that the aircraft experienced a tail strike some time back, I wonder if that may have had anything to do with this accident.

[Pax Vobiscum]

BBC2's "Horizon" (BBC's flagship popular science program, for our overseas visitors) is screening "Flight 587" next Thursday evening (27th March at 21:00 GMT). I imagine that events in the Gulf could well change this schedule, however.

The programme listing reads:

"... the investigation revealed that the tail fin of the Airbus A300-600 had simply snapped off in mid-air - how could there have been such a catastrophic failure of a critical structure?"

[Jaun Huw Nose]

Maybe this will bring about a requirement for FDR sensors on the flight deck controls so the investigators can see if the crew moved the controls or the control moved on its own....(FBW airbuses already have this) ;)

[BahrainLad]

N380, I think the argument goes that only the A300-600 has the rudder system in question, so if you are discussing length of service vs. incidents then you have to take that into account. I believe the first -600 EIS was the mid eighties?

However, I agree with you that if this is such an obvious flaw in the design of the aircraft (as is being proposed by certain member) then why hasn't it caused a serious accident before? Obviously there's a first time for everything, but I'm still interested. There are two operators in my neck of the woods that fly/have flown the -600, and I'd be interested to hear their and other operators views on this event - which I guess will happen in any court case.

[cwatters]

> BBC2's "Horizon" (BBC's flagship popular science program, for
> our overseas visitors).

It used to be a good science program but recently it seems to be more like a bad disaster movie. These days the art director seems to have the upper hand. It seems to consist of 90%, moody, atmospheric, shock-horror, human interest shots and about 10% science. Remember how the Airport series of films always began? First you spend a lot of time introducing the cast, explain how they all come to be on the plane etc, then just as you get to the end of the show you pull off a dramatic rescue. I suspect we already know how it will end.

[B767300ER]

Wino's comments are appreciated. He knows his aircraft well.

My questions are still related to not only A300-600 rudder sensitivity, but AA advanced manuever training in this specific type. What was this AA F/O taught to do when recovering from unusual attitudes? Why did another AA Captain relate a story of this specific F/O improperly handling a wake-turbulence encounter in a B-727? Was this relevant?

Wino---did you agree with the article in "Vanity Fair" on the A300 accident, and Jason Goldberg's comments?

thanks

[Wino]

I agreed with 95 percent or so of Jason's comments. The only real problem I had with the vanity fair article is who the**** shopped it to Vanity fair? It aint where I get my aviation info from generally...

Sten was taught by AA to use COORIDINATED RUDDER to keep the blue side up. (As was I)

The captain in question had a personal beef with Sten. The Engineer on that flight told a different story. But interestingly, even if it is 100 percent true, Howcome the Boeing survived and the AIRBUS didnt?

BAHRAIN LAD,

There is something else that isn't common to all the A300s. Not all the A300s have fuel in the tail like that A300605Rs. Thats a lot of weight on a long lever arm.... Many other A300600s don't have the stab tank... The manual says to get that fuel out of there before entering turbulence... I believe the gulfair a300600s don't have the stab tank.

Cheers
Wino

[Bubbette]

I Confess--it was me wino--before I discovered Pprune, I got all my aviation info from Vanity Fair, and now I'm their assistant aviation editor. Shhh! ;)

[B767300ER]

I agree Vanity Fair does'nt really have credibility when it comes to aircraft accidents. The thing that disturbed me about Goldberg's comments were that he made these derogatory remarks about the Airbus that AA operated in a public forum---a magazine. Why would an AA pilot basically tell the public that the aircraft AA flew were'nt safe? I see he's on the 767 out of LGA now, but I'm just curious.

I also hold Airbus responsible for assuring the aircraft was safe, including the tail striking the ramp at Toulouse during a windstorm before it was delivered. How much do we really know about composites incorporated in aircraft structures? How much damage could they incur if things like tail-strikes and severe turbulence encounters (or inflight upsets) happen?

AA training must have some responsibility also, if F/O Molin was doing something AA taught. Advanced or rapid manuevers in transport category jets just are'nt smart and certainly could lead to fuselage/flight control damage. Seems to me AA kind of has radical procedures in some areas, including having Captains make PA announcements while he/she taxiies the airplane, and re-briefing approaches (both pilots' heads down) below 10,000 feet, and that ridiculous PA announcement the FO makes approaching the gate when he/she should be watching the ramp for equipment. Would you trust those wing-walkers, Wino?

FAA would have some responsibility also, if lack of oversight caused these AA procedures to be approved without some sort of research/review/dialogue.

[Wino]

Virtually the entire investigative group of 587 bid off the aircraft based on what they learned (including Jason Goldberg). A huge number of others did as well. These guys were not stupid. They really did their homework talking to engineers, structures peoples, composit people etc...

For many of them it just doesn't pass the wife and kids test anymore.

The Airbus at AA is a VERY small tight comunity. There were only 35 aircraft total in the fleet. In NY there were about 90 captain and 90 copilots. We all knew each other quite well and had flown with everyone. It was a stable community with no turnover. People stayed on the aircraft often till they retired. No one but no one thinks that Sten Molin or Ed States could have ever reversed the rudder 5 times in any circumstance.

Now compare that to the 727 community where when STen was on it we had 180 727s or so... So one idiots characterization of sten's flying doesn't hold a lot of water...


The only reason that I stayed on the aircraft is that I felt that the alligator that is closest to the boat are Islamic terrorists with knives, and they are more likely to go after another 757/767 because of the ease of getting sim time in those planes (this goes to whether you think 9/11 is really over, and I got to say, I think nothing has really been done to prevent another one)


As to AA procedures, I don't agree with all of em, but they are written in blood. The arrival announcement is to get the slides (to prevent killing someone in the gate area with an accidental deployment) just before the aircraft stops. It doesn't really distract me. All aircraft are required to have boom mikes, I just configure it before I enter the ramp and use the toggle. I am still lookin out the window, yet making my announcement. With my feet over the brakes, I guarantee even if I develope a stutter we aint gonna hit my wingtip...

I don't view the captain making an anouncement while he taxies as a big deal either. We got brakes on my side of the airplane for that problem as well. And I haven't seen anyone brief below 10 on my aircraft either. Don't know where you saw that, but I have spent almost my entire career in the Airbus community and we don't do it.

And as to maneuvering a Jet. Do what it takes to keep the blue side up, You get upside down and you got bigger problems. That doesn't mean we were taught to go out and break the aircraft. We haven't had any problems with that sort of thing in the other 800 or so jets that were in the fleet, but somehow the Airbus community got a bunch of busted tails.

Sure seams like an airbus problem to me.

Cheers
WIno

[N380UA]

Any A 300-605 driver:

The A 310 manual states -

In the event of loss of both systems switching circuits located in each FLC provide a signal to retract the variable stop actuator to low speed position.

Does this hold true for the -605, and could the systems have failed and no announcement was produced on the flight deck?

[bigbird]

N380UA
To quote the a300-605R flight manual:
"2 independant rudder limiting systems controlled by the FLC, progressivly decrease the maximum rudder travel from +/- 30 below 165kt to +/- 3.5 above 310kts. If both systems fail, whatever the aircraft speed, the mechanism returns to the low speed position( +/- 30 rudder travel available).
If the system does not return to the low speed position, an ECAM warning (indicating the rudder travel system is jammed in the high speed range) is activated when flaps are at 20 or more."

don't know if that answers your question.

[BahrainLad]

Thanks for the info Wino.

Excuse me for not reading all the relevant information, but with regards to the stabiliser tank, was this particular aircraft so equipped and what was the level in the tank at the time of the accident?

And, FYI Gulf Air have never operated the A300. However, Kuwait Airways (605R), Qatar Airways (622R), Emirates (605R) and Saudi Arabian Airlines (620) have all operated the -600, at one stage or another.

[arcniz]

Each airframe series has unique systems comprised of sensors, sensor data transmissson and / or filtering processes, flight system control computers, hydraulic actuators, and the software / electronic / mechanical glue that makes all those things sing together. Even if these are highly similar across related airframes, individual designs can have their own idiosyncratic problems.

The documented reports of tail-wiggling oscillations and eccentric responses to in-flight control actions suggest a real design problem might exist in the 600 rudder controls.

I would suggest that it is incumbent on Airbus to prove that they have designed to prevent such oscillations and tested to verify the correctness of the designs under all plausible flight conditions and maintenance scenarios. Can Airbus prove this? Almost certainly -- if it is true.

[Belgique]

Quote: The A 310 manual states -

In the event of loss of both systems switching circuits located in each FLC provide a signal to retract the variable stop actuator to low speed position.

Does this hold true for the -605, and could the systems have failed with no announcement being produced on the flight deck?

To quote the a300-605R flight manual:
"2 independent rudder limiting systems controlled by the FLC, progressively decrease the maximum rudder travel from +/- 30 below 165kt to +/- 3.5 above 310kts. If both systems fail, whatever the aircraft speed, the mechanism returns to the low speed position (+/- 30 rudder travel available).
If the system does not return to the low speed position, an ECAM warning (indicating the rudder travel system is jammed in the high speed range) is activated when flaps are at 20 or more."
. Assume that a software(or design) glitch existed such that when large pressure transients are experienced (such as in a wake vortex) a rudder limiter system (RLS) trips itself into self-test (or hands over to the other RLS system - OR BOTH [see below]). Because their function is directly speed-related and their purpose is to progressively inhibit rudder travel, their one essential driving input must come from the CADC. But if the CADC's input data (and outputs) is in a state of flux because of transiting the wake vortex, you may see a situation where RLS1 hands to RLS2 (which is feeling the same strain about its own credibility and attempts immediately to hand-over back to RLS1 etc etc).

Now why would this occur? Some of these systems (and early systems in particular) were designed to hand-over and go into a self-test mode before declaring themselves failed (similar to a BITE check self-test on power-up). Great to have systems capable of mutual back-up - but not so great if they were to share a common glitch that could be brought about by an environmental (large short-term pressure transients) that had them swapping authority back and forth (or attempting to do so whilst simultaneously attempting to self-test). And what might be happening if they are handed and/or forced to accept authority whilst in that self-test? Why would they be? Perhaps because self-test is yet incomplete and as far as the FLC is concerned, they have not declared themselves failed or off-line and are therefore deemed available. Or perhaps they are passing their own self-test and are available (but only until back in operational authority)....

What we are talking about here is a scenario where both RLS systems are simultaneously experiencing the same "induced" failure mode (or something that is being self-interpreted as a failure - and which has them (or courtesy of the FLC) trying to hand-over to each other. In this weird interregnum you may indeed have the aircraft FLC (or pilots) trying to correct for sudden yaw but having to contend with excursions through this configuration in green [If both systems fail, whatever the aircraft speed, the mechanism returns to the low speed position (+/- 30 rudder travel available)]. Why wouldn't a failure necessarily be annunciated? In many systems, in order to stop nuisance failure alerts caused by transient conditions, failure attention-getting is latched out either for a finite period or until an “off-line” self-test mode is completed. In the scenario that I have envisaged and described here, because the failure is a commonly held susceptibility to CADC data-flux, neither system gets to complete its self-check before it is called upon [by the other] to take over authority.... therefore no alerts and RLS systems that are dangerously making excursions into and out of (+/- 30 rudder travel available). End result? Inappropriate rudder deflection travels that in turn generate a requirement for correction (but those corrections are also overtravelled….). See the destructive continuum?

With a little further examination this type of mutual excitation failure may be able to be induced by other “inappropriately sensed failure” parameters (ticking faults?) and explain the FEDEX hangar failure and other instances of tail-wag. It may indeed cause a yaw-damper system to trip in protest (before start-up - say).

[Anti-ice]

There are well over 3000 airbuses up there at anytime.

Very different plane to a Boeing,but it's an airliner that does a good job.

maybe the companies a little younger , but i would worry more working on a 737 / DC10 :)

[TheShadow]

Anti-Ice

You work for Airbus or a partner firm, right?

Your job is to stifle cogent debate by injecting inanities at the appropriate point, right?

Well done. You're earning your keep.

theShadow

[Wino]

Anti Ice,

Very few of those 3000 aircraft are more than 10 years old. Aging aircraft are the issue here, and it doesn't have to be structural that doesn't age well.

Cheers
Wino

[N380UA]

Belgique, bigbird

Thanks for the clarification. Notwithstanding the fact that the investigation has not yet concluded, it does appear as though a RLS “failure” has contributed to this accident.

[Belgique]

N380UA

That remains MY THEORY only.

The NTSB plighted their troth to the pilot rudder input theory at the last AA587 public hearing and now refuse to be swayed from that line (being the path of least resistance). Airbus also of course subscribe to the pilot error theory - because it fits their stance so well.

So in a system where the majority (of the major players) rules, nothing is going to change - notwithstanding any evidence, history, anecdotal reputation, expert opinion or cogent hypotheticals pointed elsewhere.

Of course having a DFDR that conveniently produced nothing useful (by way of telling data) also helped.

Belgique

[OFBSLF]

and that ridiculous PA announcement the FO makes approaching the gate when he/she should be watching the ramp for equipment.A brief thread hijack:

As SLF who once had gold status on AA (125,000+ miles in one year), I think that AA's announcement helps keep the idiots in back in their seats until the plane stops. I can't count the number of times I've seen pax on UA and DL stand up prematurely and nearly topple over when the aircraft finally comes to a stop.

[arcniz]

Belgique is "too kind" in his disclaimer.

Just as some banks are "too big to fail" because they are so key to their industry, so also are a couple of airframe manufacturers...... or three, if you want to count NASA.

Does that mean that problems are swept under the carpet and never fixed? I don't know, but a first guess would be that barrels of midnight oil have been and are being burnt in trying to identify possibly related problems, cover them up, and then gracefully phase in changes that finesse-fully remove the "theoretical" faults.

[amanoffewwords]

For info there's a program about this accident on UK TV tonight- BBC2 Horizon @ 21:00 - see BBC News online here (http://news.bbc.co.uk/1/hi/sci/tech/3008385.stm)

[hobie]

did I pick this up correctly from the BBC programme ....... 4 inches of pedal movement on the ground gives full rudder deflection ...... one and a quarter inches of pedal movement in the air gives full rudder deflection ......

I thought that once airborne and with increasing velocity that pedal movement is progressively restricted with a corresponding limit on rudder deflection (to structurally protect the rudder/fin)

this was not mentioned at all in the programme?

[jshg]

I just watched that BBC programme on the loss of AA587. If (-BIG if) the programme was right in portraying AA as promoting the use of rudder to recover from extreme attitudes - and there appeared to be training video supporting this - then surely this must be the crux of the issue.
I've been flying the A300 for the last 11 years, and the 737 before that. I was always trained since basic flying that the rudders in flight were foot rests only, apart from an engine failure or the first/last 5 seconds of the flight. I can think of no other circumstances where I would use rudder - A300 roll input is perfectly adequate. Shortly after the crash Boeing also issued a notice pointing out that their rudders were not designed to be used in this way.
I recall a cross-wind approach some years ago when the PF reverted to his previous turboprop type and applied rudder in the last 500'. There was a sickening, uncomfortable wing-drop as well as a most unusual noise before I clamped my feet on the pedals.
The one thing that continues to puzzle me is the wake turbulence. The A300 easily outclimbs a 747, and vortices move downward. How could AA587 have encountered JAL's wake ?

[Fundi-Ya-Ndege]

I Just watched the same on the beeb.Quite unusual for the hacks to get a few of the facts straight for a change.
I don't have quite so much experience on the bus as the previous poster but I have to agree on the rudder inputs though.
I was also told that during the certification of any aircraft, the design load factors are based on only one full control deflection, not on several..........

[Centre Command]

I was under the impression that in flight full rudder pedal movement would give you less and less rudder deflection, for obvious reasons.

I fly boeings. I cannot imagine that what was said in the programme was right.

Why would an aircraft be designed so that if you accidentally bumped the pedal that you would get full rudder deflection? It's just nonsense!

[Bootlegger]

Excuse me for being naive...im relatively new to flying, and possess a ppl(sep) licence......would someone please explain why the rudder isn't used in flight in the large passenger jets......i understand that with greater velocity less movement would be required...but it sounds like the rudder shouldn't be used at all........plus.......on x-wind lands.....surely it has to be used to line up the aircraft just before touchdown.........i also understand that it doesn't apply to my 152 (or so i've been taught). Please dont jump down my throat, this is an innocent question. Thanks.

[Red Leader]

Of course it is possible that sabotage was involved. An small explosive charge in the tail would have done it. The plane had just come out of service. Funny how they didn't release the actual voice recordings of the last few seconds of the flight, or even the supposed warnings of wake turbulence before take off, yet they did release the take-off clearance. Why only the transcripts for these other times? Call me a conspiracy thoerist, but you can bet your bottom dollar that if there was any information pointing towards this, it would have been extremely well covered up, given the timing after 9-11, to avoid national panic. Things are often simpler than they seem!

[GrantT]

"Call me a conspiracy thoerist, but you can bet your bottom dollar that if there was any information pointing towards this, it would have been extremely well covered up, given the timing after 9-11, to avoid national panic."

OK, so lets say that they did cover the "sabotage" up so it would avoid national panic, why don't they now release the information about their being a small explosive device, America is now past 9/11 (relatively speaking). The only reason i can think of is because there was no explsive device :rolleyes: if there actually was foul play involved the FBI and not forgetting the bush administration would have been onto it like flies on......well you know what. It would have been great propaganda for the admistration and would have further strengthened there war on terror campaign.

[simon brown]

As a mere laymen and PPL I read the responses with interest. The program seems somewhat sensationalist to me,If you and other flyers of other aircraft are aware of this, the program made no attempts as implying its generally known that "rudders are merely foot rests for the majority of the flight" The program gives a somewhat unbalanced view. Perhaps a few interviews with pilots from other airlines flying all sorts of aircraft having the same views would have balanced up the program somewhat.

Perhaps if such program makers were aware of this site they could get some more INFORMED opinion as to the facts from avaitors across the board, and produce a less sensationalist piece that appeared somewhat black and white. To members of the public this program must be somewhat alarming without the full facts..

Fundi Ya Ndege are you saying that designers of aircraft fail to build in factors to cater for the situation where a pilot "wrestles" for control requiring full multiple control inputs in order to restore balanced flight in say a windshear/wake turbulance situation? As an engineer that to me seems somewhat odd

[captf]

Re various FAQs on 587 -

The reason the rudder was so sensitive is that unlike the current Boeings that use variable rudder ratio systems (full travel produces progressively less actual surface movement as speed increases) airbus dropped that system with the A300-600 and subsequent and use a variable stop. the gearing is constant but the load increases, and the maximum travel decreases with increasing speed. The effect of this when breakout forces are taken into account is that it would be very difficult to modulate such a control - but of course no one ever thought that pilots would use the control in that way... see various Aviation Week articles by the excellent Michael Dornheim.

Re jshg's query about why the A 300 didn't easily outclimb the 747 - it did, but then accelerated from 1000ft while the 747 didn't begin its acceleration and clean up until at least 2000ft, so the A300 was at one point below and downwind of the 747. Actually the wind necessary to bring the vortices into play has been quoted as only 28kt (from memory) but this refers to the component at right angles to the flight paths, and means that the total wind necessary might have been higher...unless these vortices were left lying around from some previous departure! The point is not that the vortex upset was particularly strong, but that it triggered this wholly inappropriate and uniquely AA response with the aggressive rudder inputs.

There has been a lot of puzzlement along the lines of 'I thought i could apply full control up to Max manoeuvre speed' Well, you can though whether you should really want to is debatable, but what happens with the reversals is that the aircraft yaws and overshoots the equilibrium position, so achieves a higher than normal sidleslip; if you then reverse the control, the fin load is now much higher than the either of the two design cases. These are: max deflection at zero sideslip (ie one bootful from straight and level) and max rudder in a sustained sideslip, and it is easy to see how the reversal loads will be higher. Should we all have been expressly warned of this? Well, my car handbook doesn't spell out for me what would happen if I decide to slam the shift into reverse at max speed, because they don't believe I would want to do that, and it has been the same for the aircraft builders. Of course in a country that tells you your coffee is hot, things may be different.

[FatFlyer]

Bootlegger,
After years of being told to use the rudder in the turn to stop adverse yaw, particularly in something like a glider or seneca which does not turn much without it, I am now boll*** by the training captain every time i touch it, other than x wind landings or engine out.
I think the reasons are a much bigger roll -yaw couple on a swept wing jet than on a light a/c making it not needed, also it upsets the yaw damper as it trys to correct for your rudder input giving an uncomfortable swing in the back.
please correct me if wrong or there are other reasons.
it's also interesting that when correcting for wing drops etc in light a/c the rudder is used, in a difficult situation it might be easy to revert to this, though not the correct procedure in a jet

[squeaker]

Simon Brown- Fair points but unfortunately TV/ Journos will always go for "sensational" over "accurate".
Never let the truth get in the way of a good story!

Captf- Excellent post, well done, says it all really.

[Wino]

Captf,

Recent information has come out from Airbus (withheld at the hearing...) about the rate of change of the rudder load limiter as well.

The rudder load limiter basically uses a jack screw to retard movement of the pedals, thereby reducing movement of the rudder. . If you get the airspeed trend arrow on the PFD more than 10 knots long (IOW if you will be going more than 10 kts faster in 10 seconds than you are now) YOU ARE OUT RUNNING THE RUDDER LOAD LIMITER, and you can break the aircraft. The max rate of change on the rudder load limiter is 1 knot per sec. The A300605R particularly at low levels accelerates MUCH faster than this.

So anytime you see the trend arrow greater than 10 knots long pointed up you are not protected by the rudder load limiter.

As to AA;s training. They never advocated anything other than cooridinated rudder. There was a long discussion about crossover speed and high angle of attack and rudder inputs (VERY RELEVENT to loss of control crashes in the 737) but nobody was advocating stomping rudders.

The airplane is a trap for a Pilot induced oscilation in the yaw access at certain speeds.

Cheers
Wino

[Anthony Carn]

Regarding the Horizon programme and according to my searches, which I cannot personally verify as accurate :-

[1] -- There was no mention of the comments of senior American Airlines pilot, John Lavelle, who told the NTSB that five years ago, while flying with Molin (the co-pilot in the crash and the pilot in control during the incident), he noticed that Molin used the rudder too aggressively during a takeoff.

[2] -- There was no mention that in 1997 an American Airlines pilot, David Tribout, expressed concerns about the way his company's pilots were being trained to use rudders, saying what they were being taught was potentially dangerous.

[3] -- There was no mention that in 1998, reacting to a turbulence incident involving another A300 flown by American, Airbus warned the NTSB in a memo that rapid back and forth movements of the rudder could lead to structural loads that exceed the design load of the fin.

Can anyone verify the above ?

If they are accurate, then why were these not mentioned in the Horizon programme ? Or did I miss them ?

[TightSlot]

Please excuse rookie question from a non-pilot.

According to the program, about an inch and a half of travel on the rudder pedals causes full deflection of the rudder at high speed. This seems very little - a pilot sneezing or coughing could in theory be enough to cause this kind of movement, which while not catastrophic, might make for an uncomfortable ride down the back.

Have I missed something obvious here? (like pilots feet aren't on the pedals at all during cruise maybe?).

Thanks for any response. Without knowing enough to be sure, it struck me as a balanced and fair assesment of the problem shown in the program. Airbus sure make it tough to love them, especially in the current climate of admiration for the French!

[amanoffewwords]

Purely as a layman I thought the program was a tad biased against Airbus - i.e. the accident happened because it was an Airbus - so it's interesting to see that Boeing released a memo advising against using the multiple rudder reversal procedure on their planes too (as stated in a post above).

I also had the feeling that there was something missing from the program and that maybe the producers knew something that they were not allowed to broadcast (maybe for legal reasons) - it was the kind of feeling when you watch a film that ends open-ended and you kinda of go "and then what happened"? Did anyone else get that feeling?

I also thought it was a nice sensitive gesture not to broadcast the actual voice recordings as the plane was about to go down - it's not nice to listen to and should be kept private for the families and investigators involves, imho.

May they rest in peace.

[Capt H Peacock]

I’m a bit uncomfortable with the use of rudder to recover from upsets. The usual technique for recovery from unusual attitudes is unload, speed, roll, pitch. In other words reduce the G-load, control the speed trend with power bearing in mind the pitch/power couple, idle thrust for nose low, mid to full thrust for nose up, roll to the horizon, then pitch. Use of speed-brake should be cautiously considered against its effect of reducing available lift and compromising the roll authority of the spoilers.

I’m afraid I can’t think of any primary role for the rudder in this. Unlike the wings or the horizontal stabiliser, it is not built to withstand high manoeuvring loads. The rudder is primarily for achieving longitudinal balance in flight and counteracting moderate out of trim loads in the event of engine failure. Yes, the secondary effect of rudder is roll, but it has only a very limited application in the recovery from upset scenario. If yaw is required then assymetric thrust would be far quicker.

In all the years I’ve been flying big aeroplanes, I cannot remember any procedure that required me to rapidly apply full rudder followed by an immediate reversal. I have been conditioned to avoid the use of large rudder deflections at high speed. In many years on the 767, from memory the failure of the rudder ratio system after a hydraulic system loss (can’t remember which one) specifically mentions the necessity to avoid large rudder inputs to avoid structural failure.

Hindsight is a wonderful thing, but we do all need to analyse the actions of the unfortunate crew involved in case there’s anything we can learn. To do anything less would be to dishonour their untimely deaths. I’ll leave blame to the lawyers and suits, that’s about all they’re good at.

[Schrodingers Cat]

I can vouch for the fact that good ole Captain Van.d.B advised using aggressive rudder inputs having seen the video of the AA symposium when it was first mooted as part of company training.

The difference is that these inputs were only advised during LOSS OF CONTROL resulting in an unusual attitude ie up to actually inverted.

The relatively minor controllability problems caused by wake turbulence as shown on the Beeb should not have necessitated these inputs, the A300 is not a 172.

The CRM aspects of being spring loaded or predisposed towards a particular scenario were barely covered.

[togaroo]

Just a few other thoughts,

Is there currently training within your organisation on large aircraft upsets? Perhaps there should be a greater emphasis placed upon upset training considering the increasing congestion of terminal areas and airways - free flight could lead to an altogether interesting situation than there has been in the past.

Unlike the pitch and roll axes, I am unaware of an aircraft that provides protections in the yaw axis. Should this be addressed by all manufacturers?

From Capt F...... "Should we all have been expressly warned of this? Well, my car handbook doesn't spell out for me what would happen if I decide to slam the shift into reverse at max speed, because they don't believe I would want to do that, and it has been the same for the aircraft builders. Of course in a country that tells you your coffee is hot, things may be different."

Lastly and unfortunately in the western world, act of god or 'accident' has disappeared from the dictionary. There must be blame - else no claim, unfortunately to human is to err.

Perhaps we should do as the journalists say and give up flying and travel by rail..........now there is a big can of worms.

[gashcan]

Having had the privilege of flying some great aeroplanes - (C130, B757/767, A320/321/330) I also share the doubts regarding:
Rudder pedal travel
Rudder reversal
Rudder use during wake turbulence encounters

Can any '300' drivers confirm that there is really only one and a bit inches of rudder pedal travel?

As far back as basic training it was drummed into us that all flying controls are powerful creatures and should be treated with respect, (although on small aircraft full scale deflection was used regularly during aeros etc).

On larger aircraft (the Herc especially), large aggressive rudder movements are not encouraged - and I can't imagine a scenario where full scale deflection rudder would be aggressively required during normal flight on any large aircraft.

Even during an EFATO rudder input should be progressively applied quickly and smoothly - not aggressively.

X-wind landings only require a squeeze of rudder really, unless the conditions are very bad in which case it's a bit more - but again, never aggressively.

I have never found the need for large (if any) rudder applications during wake turbulence.

I suspect that AA's training regarding rudder during wake encounters maybe fault, and they do not wish to admit it, for obvious reasons of liability and litigation.
For them to bleat that they were never told that rapid rudder reversal is potentially dangerous is a bit disingenuous for me. They may never have been told - but isn't it obvious? Maybe not.
Did Boeing, McDonnell Douglas or Lockheed warn of this? I suspect not.

Also, not knowing the F/Os background or experience level, it may be that he found himself in a situation that he had not faced before and reacted as best he could, using the information available at the time, overcontrolling as he did so.

Unfortunately as always, it will probably end up with the major companies involved in a slanging match, with only the lawyers benefitting.

We'll all learn from this one I hope.

PS
(The conspiracy theory just ain't sound I'm afraid!)

PPS
Bootlegger - good question, may need a longish answer and I've gone on a long time already. There is a small bit about rudder ratios in 'Handling the Big Jets' page 263/4, and I'm sure other contributers will help out!

[akerosid]

What concerned me after watching the program last night was that you had an airline which had been flying a type (in large numbers - 36 in service) for 12-13 years, which didn't seem to know certain vital facts.

They would have faced bad weather and they would have practiced drills in simulators; aren't the simulators Level 5 and therefore fully representative of the aircraft? It just seems strange that after what must be a good few thousand hours they can come along say, "what, 1 and a half inches . . . we never knew that?"

[Anthony Carn]

Quote - Capt H Peacock --"If yaw is required then assymetric thrust would be far quicker."

Incorrect. I enjoyed that movie, though. :rolleyes:

Apart from that and the suggestion that lawyers are good for anything, then I agree totally. :ok:

[Desk-pilot]

I too watched the Horizon documentary and was surprised to learn that full rudder deflection could cause loss of a tail. Designing a tail which is so vulnerable to catastrophic failure strikes me as a ludicrous weakness and one which ought to be addressed. I would like to think that any airliner I fly on is capable of handling full control surface deflections in case they are ever required to avert disaster. There are many cases of pilots who have flown outside the flight envelope in order to save the aircraft. I would be interested to know if such rudder inputs were applied to a Boeing with an aluminium tail whether it would fail also or whether it might be stronger.

Presumably sometime in the past 50 years other pilots may have done the same thing - the question is whether they survived because they were flying a conventionally constructed tailplance!

Desk-pilot

[Anthony Carn]

..........was surprised to learn that full rudder deflection could cause loss of a tail.
Apologies for yet another post, but.......

Would you be surprised to learn that full elevator deflection could cause the loss of the wings ?

Would you be surprised to learn that full thrust lever deflection could cause the engines to explode/fail ?

Would you be surprised to learn that combined elevator and aileron above a certain design speed could cause structural failure ?

.....then be surprised !

[NigelOnDraft]

Desk-Pilot...

Your comments seems to illustrate you did not understand some of the points being made.

1. <<was surprised to learn that full rudder deflection could cause loss of a tail.>>
A single deflection at any stage cannot - the rudder limiting system keeps the load below a limit - ans the design strength is 1.5x that limit.
What can lost the fin is a full deflection held long enough to reach a stable yaw angle, and then the rudder reversed to full deflection the other way - and that did appear to happen (maybe more than once) here.

As was stated last night - it was felt initially the fin was to blame. However, further study showed the the reversal of rudder exceeded the "ultimate design strength", and hey presto, as advertised it failed. A Boeing Fin is designed to exactly the same certification requirements, and likely would also fail - hence the notices that went out after this from all manufacturers.

2. <<and one which ought to be addressed>>
Fine - we'll build all airliners out of 1" Stainless Steel. Trouble is it would cost 10x the ticket price - attractive idea now?

3. <<the question is whether they survived because they were flying a conventionally constructed tailplance!>>
Again - you missed the whole (eventual) point of the program. It was shown that the load exceeded the ultimate design strength as required for certification. Make your tailplane out of anything you want - if the load exceeds its ultimate strength it breaks (Boeings also do this funnily enough).

What they did not labour on, or make totally clear, was they method used for limiting rudder deflection on the A300-600. If one is going to use the rudder for anything other than the landing and takeoff phases, then the A300-600 system is, IMHO, "not ideal". This came back to the other point of the program was that Airbus' ideas and AA's ideas of rudders (if the training video was still AA policy) were very different...

NoD

Wino

<<As to AA;s training. They never advocated anything other than cooridinated rudder. There was a long discussion about crossover speed and high angle of attack and rudder inputs (VERY RELEVENT to loss of control crashes in the 737) but nobody was advocating stomping rudders.

The airplane is a trap for a Pilot induced oscilation in the yaw access at certain speeds.>>

I think you've hit the nail on the head. Given the strange rudder limiting system on the A300-600, use of measured / co-ordinated rudder at anything other than low speed is very hard to achieve, hence my comment that AA and Airbus' ideas were so different that an accident such as this was somewhat inevitable?

From Horizon last night, it seems a PIO was building up, if the AoB's shown were correct.... Very unusal for a wake encounter to repeatedly roll the aircraft from one side to another - my experiences are you generally get just rough air / a jolt, or if you get stuck in a vortex for a bit, a rolling moment (sometimes needing lots of aileron to stop the roll - no rush to get back level) in one direction.

Can all we just remember the purpose of accident investiagtion - it is not to allocate blame, but to prevent a repetition.

NoD

[lomapaseo]

Nigel

Thank you for that post.

Alas, there are still many who will never accept the fundamental facts. Hopefully the pilots who fly these machines designed and certified to these standards will.

In this case I don't care who they want to blame (the courts ultimately decide this) just as long as the operators and crews learn from this accident.

[Notso Fantastic]

It seems the FEEL mechanism is not being considered here. Boeings have it and I can only assume Airbus too. Although at high speed the rudder pedal movement is restricted to a much smaller range than on the ground, the FEEL inputs to the rudder pedals would presumably make them feel very very heavy, therefore there is no dange of unintentionally pushing on large amounts of rudder. Certainly the 747 rudders at high speed feel solid and fixed, and never having had the desire to try out HOW much force is involved, I can't say exactly how solid, but the word 'rock' springs to mind!
The 747 device that varies Feel according to speed is the Rudder Ratio Changer: "This protects the vertical tail structure from stresses which could result from large rudder surface deflections at high airspeeds" (Tech Man). I would assume the Airbus has a similar feel system, however it would still have been at low airspeed allowing large deflections at a time of rapid upset. Maybe coupled with a pilot with a history of aggressive rudder inputs, a bad combination. I have seen several pilots myself with apparently over aggressive rudder techniques- presumably upbringing is an important factor. I remember after flying the VC10 I had to be trained out of this myself when converting to the Classic. From my early days in airline flying, i have always been made aware of 'take care with the rudder and use with great respect- it's the first of the flying controls that will fail on you'. Pilots know you can happily apply large aileron and elevator, but not to try it with the rudder.

[BobBuilder]

Ok, I'm not a pilot, so I ask humbly: is there any reason that Airbus shouldn't design the flight control software to make this accident impossible? Put it another way: is there a scenario where these agressive actions might prevent a different sort of accident? I am assuming that software can also allow a greater freedom during TO/Landing.
If not then surely this should be fixed to prevent an unlikely, but possible, repeat? Too much cost?
Not interested in blame, just being safe.

[Saint]

Previous posts state that the A300 rudder sensitivity and pedal load is increased deliberately with speed ( as well as the travel limit being reduced). However, the aileron sensitivity is effectively reduced with speed by 'locking' the outer ailerons.

Can anyone explain why this is so? I fly light aircraft and this seems counter-intuative to me.

[Symbian]

Saint

Its to stop the wing from twisting at high speed i.e. due to wing bending the outer ailerons are useless so they lock them out.

[Saint]

I understand the aileron reduced sensitivity, but why increase the sensitivity of the rudder at high speed?

[Notso Fantastic]

Rudder inputs at high speed produce very powerful effects, so the allowable range of movement is restricted AND the sensitivity is vastly increased. Full rudder at high speed would never be required.
Locking out the outboard ailerons is common- they are not needed at high speed- usually when flaps are up. Sensitivity would not be reduced by doing this. Thus they would still have increasing 'feel' with speed.
Any way you design flight control software to restrict one thing, somebody will find a way around it. So design must very carefully cater to what is being protected for- i don't think you can ever get it 'right'. Remember the A320 that flew into the trees restricting the pilot inputs because speed was too low to allow a pull up?
The Interflug upset into Moscow was horrifying- I didn't know about that one, and never knew an airliner could do that sort of aerobatics! But I distinctly remember a Tarom Airbus upset at Bucharest some 10-12 years ago- I know they lost one with an engine failure, but there was another upset that was similar to the Interflug- anyone remember?

[NigelOnDraft]

Saint...

I'm getting confused by what you mean by "sensitivity"??

Ailerons:
Most airliners have inboard and outboard, combine with spoilers on the downgoing wing. At high speed the outboard ailerons are "locked" out. However, I think someone posted here that the A300-600 does not have outboard ailerons??

Rudder:
Most aircraft allow a fixed amount of rudder deflection. As speed increases, full rudder deflection gives you less degrees of rudder deflection. However, the A300-600 just restricts the amount of rudder deflection. As Notso says, another important part of this is whether the "feel" i.e. force also changes with speed (this just simply replicates a Cessna 152 where the controls get harder to operate as speed increase due to airload).

BB
<<there any reason that Airbus shouldn't design the flight control software to make this accident impossible?>>
Well - they sort of have - its called an A320! In fact, I suspect the A320 is vulnerable to rudder reversal in the same way as here, but with most of the other Flight Envelope protections, "Upset" recoveries are not taught. You cannot overstress the aircraft in pitch, or stall it.... However, then you get all the Boeing Brigade jumping up and down about not liking "envelope protection" FBW!

NoD

Notso...

A310 Paris was Tarom I think? Some sort of impromptu aerobatic display near Orly - but all OK.

A310 in Bucharest. Something along lines of as power was reduced (to climb) one TL jammed. Machine kept "trying" to pull off power - resulted in Autopilot in with one at Full Power and one at idle - rolled in (Autopilot could not cope).

Moscow one - again I had not heard of that - looked pretty spectacular... but then so was the Icelandic B757 as Oslo recently (40deg nose down at 1500'? Recovered at 300'? And that was after the go-around!)

Best regards
NoD

[Notso Fantastic]

NOD, ah! 'Twas Paris. Can't remember the details of why, only that it was spectacular. Amazingly good piloting to recover from it, along with the Interflug, but what got into it?

Your 'Rudder' section above should read:"As speed increases, full rudder (Pedal) deflection gives you less degrees of rudder deflection" otherwise it won't make sense to people here trying to get their heads around this new concept!

To explain 'Feel', you are absolutely right: "this just simply replicates a Cessna 152 where the controls get harder to operate as speed increase due to airload". Jet airliners do not have any airload effects on flight control surfaces fed back to the control wheel/pedals as the flight control surfaces are fully hydraulically powered (exception B737 and DC9), therefore you need to have artificially generated 'feel' fed into the flight controls, and obviously this must be compensated for with increased speed and altitude which is what the 'Feel Units' are for.

[Torquelink]

BobBuilder

As Nigel says, software might (or might not) help on a Fly By Wire (FBW) aircraft such as the A320 or B777, but the A300-600 is an "old fashioned" manual aircraft with the pilots more or less directly connected to the control surfaces via rods and wires - with a bit of help from hydraulics.

[fireflybob]

In all my experience of swept wing jet transport aircraft I have never heard of anyone thrashing the rudders around to recover from an upset, including wake turbulence. The only time I might advocate rudder is if I have full aileron in to oppose roll and the aircraft is still departing.

When American Airlines decided to train their pilots this way, did they ask the aeroplane manufacturers (Airbus) first for their advice and opinion?

This almost sounds like a training induced accident. I would suggest that if these pilots had had no formal training in recovering from a wake turbulence encounter the outcome would have been very different.

[Schrodingers Cat]

I rather thought that from the picture of the control position indicator the rudder was well outside the indices for normal inputs, which I took to be the two red marks either side of the instrument display.

The Boeing 747 rudder ratio changer reduces rudder travel at about 186 kts I think, this makes it doubly strange that the programme said that you can get full rudder deflection from less rudder pedal input on the airbii, it seems counter intuitive....

[Wino]

Firefly,

As an American Airlines A300-605r pilot. I can tell you for certain that use of rudder was never advocated except as a last resort as the aircraft was getting away from you in a real serious upset. in other words, don't ignore the rudder if its all you have left. There were VERY long discussions of the effect of rudder, and what enourmous roll rate you could develope with it, especially at high angles of attack. How it related to crossover speed was really driven home. This was really aimed at the 737s community becuase of the rudder hard over problems.

No one EVER argued for a back and forth motion of the rudders, and on any other aircraft it never would have happened. But on the A300 some changes were made when they converted it to the 600 series that laid a trap.

NOD,

Outboard ailerons were deleted when the A300b4 became the A300600 series. Also, spoilers became "spoiler by wire" and most importantly the rudder load limiter was changed from a ratio changer system like the Boeings where 4 inches of travel always equalled full available rudder (be it 4 degrees at high speed or 40 degrees at low speed) to a fixed ratio changer where a jack screw simply restricts rudder PEDAL movement, rather than the movement of the rudder.

Notso,

Furthermore in a peculiarity of the system force required to reach the available stop decreases as the speed inceases untill it is virtually identical to breakout force. On the A300-605R there is NO rudder feel mechanism. The controll forces are NOT balanced and the stops get EASIER to reach as speed increases.

BTW, it gets alot smaller than 1 inch at barberpole. (it goes down to about .7 inches of travel at Vmo/Mmo


NOD again,

The bucharest crash was specifically cited in the AA maneuvering program. the Auto pilot was NOT engaged. The pilot flying the aircraft try to correct the asymetric engine condition with only ailerons, and not terribly aggressive movements of that. Airplane rolled over, all killed.

The Airbus single engine climb and crash on autopilot was the A330 during the test program that crashed killing all while trying to demonstrate a single engine go around on autopilot.

Cheers
Wino

[TopBunk]

Wino

I think the A330 crash during test at Toulouse happened partly because the engine was simulated failed after the go-around was initiated and because of the low level-off platform altitiude.

I understand that the high rate of climb caused the A330 to enter ALT* mode (alt acquire for Boeing types), and in that mode the autopilot flies a programmed parabola to level off. The problem was that the thrust loss from the simulated failure meant that the speed decayed to the point of stall and the crash resulted with loss of all on board.

[A Nonny Mouse]

I am sure that the senior AA pilot gleefully pointed out that in 75 years this was the first aircraft ever to loose its tailfin. He seemed to stress that this would never happen to a boeing.

I am sure I remember a B707 loosing a tailfin in severe turbulance over Mount Fuji in the 60s, killing all on board. Does this not count because it was not an Airbus?

The whole program could have been summed up in 2 minutes. If you reverse rudder several times at speed in any aircraft be it Airbus or Boeing you will exceed max load and are likely to end up in severe difficulty! Yet they padded it out with lots of anti Airbus Rhetoric, and tried to insinuate some kind of Airbus coverup.

[Faire d'income]

I completely understand colleagues of the FO defending him, thats what friends are for. However their case doesn't really add up.

The program, while very good, ran along the current US/UK ' hate everthing francais' lines with the notable exception of the end.

The conclusion seemed to be don't input full rudder reversal repetitively on any type or you risk structural failure. That knocks the anti-Airbus argument back.

We seem to be left with two questions:

1. Is the certified ultimum load on the A300 ( indeed all types ) sufficiently high or is there reason to raise it?

2. Are training sections doing enough to ensure pilots operate to manufacturers specs and understand the procedures required to achieve this?

The program also highlighted one small point that has not been picked up on here, wasn't dealt with fully in the cockpit and if I was honest happens in my cockpit a lot;

The unfortunate FO was never happy with that TO. He was obviously uneasy about departing after a 747 even though the correct separation would be given. ........Some good advice I got years ago advised me to always track down that 'funny feeling' even if it's the FO's instincts, not yours. It might just save you.

The whole thing is a very sad business.

[411A]

fireflybob,
In talking with many AA pilots, both current and retired, it would appear that AA has their own ideas about upset training...indeed any training.
Was therefore not the least bit surprised that IF a vertical stab was to come off an aircraft, any aircraft, than the colors painted on the side would be American Airlines.

Sky Gods' know 'better' than others, it would seem...:rolleyes:
Beaks well above ground effect, approaching the ozone layer.

Lawyers will have a field day in the end, and that truly IS sad.

[jshg]

Wino - "On the A300-605R there is NO rudder feel mechanism".
The A300-600 manual shows the rudder as having an 'artificial feel and trim unit'.
Somebody else queried A300 rudder pedal deflection. The manual says:
"2 independent Rudder Travel Limiting Systems (RUD TRAVEL) controlled by the Feel & Limitation Computers (FLC) progressively reduce the maximum rudder travel from +/- 30 deg below 165kt .. to +/- 3.5 deg above 310 kt." I don't know what that translates to in inches because there has never been any need for me to use the rudders in 2 eng flight (- and that includes a very nasty CAT encounter).

[exeng]

<<I am sure I remember a B707 loosing a tailfin in severe turbulance over Mount Fuji in the 60s, killing all on board. Does this not count because it was not an Airbus?>>

I believe the tragedy you are referring to involved a B.O.A.C. B.707-436.

In that case it was very strongly suspected that severe turbulence caused a total break up of the aircraft. The mainplane failed at the centre section, but whether this was the first point of structural failure or not I cannot be certain.


Regards
Exeng

[Airbus Unplugged]

There was a B52 that lost its rudder in the 60's? during LL training. That was recovered by some pretty fancy flying.

[geoffrey thomas]

For the record there have been a number of Boeing's lost in turbulence/thunderstorms.

Northwest 720 out of Miami Feb 12, 1963, although the tail wasn't the first to go. The aircraft broke up when the pilots started to regain control. Aircraft had flown into a violent turbulence associated with a thunderstorm line.

BOAC 707-436 March 6 1966: Tail was hit by a mountain wave off Fuji on a sightseeing diversion as weather was "perfect". The aircraft was from Tokyo to HK and captain requested ATC clearance to descend to about level with the top of Fuji. Tail collapsed to the left and took with it the horizontal stabilizer on that side, which cause a violet pitch motion that took all engines off. Front broke off in the descent.

A BAC1-11 of Braniff was also lost to thunderstorm in August 1966. The aircraft was struck by violent turbulence ahead of a thrunderstrom line in clear air.
The strong shear struck from the rear and took out the elevators and rudder, although the basic tail stayed intact initially. Stardboard wing then failed.

Geoffrey Thomas

[Notso Fantastic]

Airbus- I remember the pictures of the B52- there were a lot of jagged edges where the fin separated including a large bit sticking up. Enough to provide a little basic directional control. The AA lost everything.

[pom]

I feel that if the previous Airbus incident at Moscow had happened to a Boeing, the fact that the pilot was unaware that rudder reversal could result in loss of the fin would have been acted on, and the manufacturers' notification would have been issued shortly afterwards. Boeing is far more pilot oriented that Airbus, which tends to be engineer driven. Airbus non moving throttles, which are almost universally disliked by pilots, are a classic example of this. A comparison of the design philosophies of the B777 and the Airbus fbw series shows many examples of these differing approaches.

[Cornish Jack]

Re the AA upset training video - I have watched that video (and the other four associated with it) some 30-40 times and there is NOTHING in it which advocates rudder reversals. There IS an extremely well presented case for the appropriate use of CO-ORDINATED rudder and one specific caveat regarding the MD11 (hugely over powerful). It was specified as an appropriate response for upset recovery under particular conditions. The emphasis was necessary because of the repeated fatal results of the 737 crossover problem. That problem was discussed and demonstrated in a particularly accessible way and the illustrations left no doubts about the problem or the importance of rudder when below crossover speed.
In addition to the apparent misunderstanding of the AA training video contents there would appear to be a continuing (deliberate?) misunderstanding of the causes of the various Airbus accidents - particularly Habsheim. If you try to carry out a manoeuuvre for which you have not been trained in circumstances where the most basic prudence would suggest it was stupid to do so, the aircraft protection systems, which keep you and most of those on board alive rather than killing everybody in a 'stall and burn', should be praised rather than villified. :mad:

[Notso Fantastic]

I hope your last comment was not directed at what I said as i was the only one to refer to Habsheim recently:

"Any way you design flight control software to restrict one thing, somebody will find a way around it. So design must very carefully cater to what is being protected for- i don't think you can ever get it 'right'. Remember the A320 that flew into the trees restricting the pilot inputs because speed was too low to allow a pull up?"

Read it carefully- is there a 'misunderstanding' there. The Airbus has more 'protection from pilots' features than any aeroplane flying. Sure enough, no pull up was allowed by the system (quite correctly as a stall would have been the immediate result). So a crash ensued. But Habsheim is not the issue here- that reference was to answer a query of 'why can't everything that can go wrong be catered for in system design' query.

[B767300ER]

The one thing to remember about transport category aircraft is that they are'nt military fighter aircraft and cannot be maunevered as such.

Enough said.

[Raas767]

I am not an expert in Aerodynamics so I will not speculate on that topic. I did, however, fly with a captain the other day who was one of the first AA pilots to go to France for 300-600R training. Among other things, he told me that the Airbus rudder is not actually burried in to the airframe it is simply glued and bolted on. That doesn't sound good to me.
Also, through various publications and books that I have read lately regarding, among other things the shoot down of TWA 800, the NTSB has about 0.0% credibility with me and I am sure that the final report will convey what is considered politically expediant. What is politically expediant is that Sten Molin caused the airplane to crash through excessive use of rudder. Weather or not that is the truth is irrelevant.

[TURIN]

Raas767

The B737 fin is not "buried" inside the fuselage either. Most of the airliners I have worked on for the last 20 years have very similar construction in this department. A handful of trunnions and lugs on the top of the fuselage attach to a handful of similar fixtures on the fin.

Can someone please just clear one thing up.

The A300-600 rudder pedal movement at high speed (ie not take off or landing speed) of about 1". Does this really give full scale deflection of the rudder control surface?

When I heard this on the Horizon program I nearly threw the cat at the telly!

Tell me it aint so please.

Thanks to everyone who has expressed a view on this thread. It is what PPRUNE should be all about, professional informed opinion, not the slanging matches that have dominated some topics.

[Cornish Jack]

NSF
I referred to Habsheim because it was (as far as I can recall) the first of these 'investigative' TV programmes. Its 'conclusions', for want of a better word, appear to have influenced a number of contributors to this and other threads. I did not see the latest Horizon programme - from comments it would seem to have been as technically irrelevant as the Habsheim rubbish.
ALL aircraft manufacturers have problems with their products at times and Airbus are no better or worse than the others - their 'crime' would appear to be having the audacity to produce an innovative aeronautical design.
I have far more experience with the Lockheed and Boeing products than those from Toulouse but that limited experience has produced more plaudits than grumbles.
BTW, the A320 flew into the trees at Habsheim because the pilot was doing something for which he was not authorised, competent or briefed, with passengers on board, whose survival was down to the aircraft's ability to protect its occupants from the worst efforts of its operator.

[Shore Guy]

TURIN and all,

From the NTSB docket on AA 587…..

“On the A300-600, for example, at airspeeds lower than 165 knots (when rudder travel is unrestricted by the airplane’s rudder limiter system) the rudder can travel +/-30°, requiring a pilot force of about 65 pounds to move the rudder pedals about 4.0 inches. However, at 250 knots, when the limiter restricts rudder travel to about +/-9.3°, a pilot force of about 32 pounds is required to move the rudder pedals about 1.3 inches. The rudder system on the A300-600 uses a breakout force6 of about 22 pounds. Thus, at 250 knots, the rudder can reach full available travel (9.3°) with a pedal force of only 10 pounds over the breakout force”.


A description of this bizarre rudder limiting system can be found at:

http://www.ntsb.gov/events/2001/AA587/exhibits/241835.pdf

[brakedwell]

The B52 fin/rudder loss was not a straight forward failure. My B757 Instructor at Seattle in 83 was the pilot of the said B52. When showing me photos of the damage, he said they were searching for turbulence in the rockies as part of an underslung cruise missile mounting test when the incident occured. They certainly found what they were looking for! The B52 entered a vicious mountain wave, the rudder came off cleanly and the vertical stabilizer snapped off leaving about a quarter of it's area sticking up from the fuselage. He found it hard to control the airplane, expecially in pitch. An F100 was scrambled as a chase plane and confirmed the detached part of the fin was still lying across the horizontal stabiliser. Several violent manoeuvres succeeded in detaching the fin and they made a high speed emergency landing at Edwards AFB.

[Arkroyal]

Raas 767 said:
What is politically expediant is that Sten Molin caused the airplane to crash through excessive use of rudder.
Sadly that is also the true cause in my opinion.

More 'politically expedient' for USA plc might be to blame Airbus.

Freeze framing the telemetry from the FDR shows aggressive rudder inputs from the onset of the minor upset. The aeroplane was cross-controlled on many occassions, and most viloent rolling manouvres were induced by the clumsy application of rudder.

Any piolot whose training manuals contained a graphic of an inverted airliner in the wake of another, and the scary and inaccurate video imploring early use of rudder to control the situation was more than likely to be nervous before take off, and pre-conditioned to mis-handle the situation.

'Sky Gods' know 'better' than others, it would seem...
Beaks well above ground effect, approaching the ozone layer.'

At last I seem to be agreeing with 411A.........should I get out more?

[twistedenginestarter]

I've read most of the posts on this thread but I can't remember if anywhere it has been explained why the plane actually crashed. As I recall it plummeted. I can see it going into a directional oscillation that became uncontrollable but I don't think that happened did it? I can only assume that weight loss was more than the elevator could correct but that seems difficult to believe.

[Notso Fantastic]

How else can you explain the loss of the engine/s and subsequent pre-crash fire? I would expect violent lateral oscillations took place. Try flying a model aeroplane without a tailfin- anything can happen. The weight loss was irrelevant.

[topman999]

Were the flaps in F1 position, that is key, one must say. The question of the radius of gyration being prevalent on AMR 587 is questionable to outside sanguine individual. A question yet to be proposed indeed :confused:

[Frangible]

Can someone further enlighten us on the Interflug A310 incident? I was puzzled as to the relevance of this in the documentary ever since I saw it. Don't think it is correct.

My memory of reading the report on the Interflug at Moscow was that the tower ordered them to go around, and they engaged TOGA mode. The pitch seemed excessive to the pilot, who pushed the column forward thinking this would disengage the automatic mode. He had not been informed or trained that this action could not disengage TOGA mode, and the result was that, he still having elevator authority, he was commanding nose down, while the stab was going nose up as requested by TOGA mode. This caused the first stall and the subsequent roller coaster ride (three further stalls I think) before they got stabilised.

What has this got to do with rudder deflections? The film claimed that rudder deflections set this incident off, but I seriously doubt this, and they certainly had nothing to do with the roller coaster ride.

As for the other incidents to A300-600s or A310s, e.g. Tarom over Orly, and the tragic crashes by China Airlines (at Nagoya in 94 and Taipei (in 98?) these were cases where the pilots thought their actions could cancel the automatic mode (not TOGA mode in every case) when they could not. Rudder was absolutely not involved in those cases.

I have a suspicion that the film was desperately looking for precedents to AA 587 and couldn't find any, and so discovered different types of incidents but also involving Airbuses and hoped no one would notice that rudders weren't involved. But if anyone can show that rudder was involved in these incidents I'm happy to be corrected.

[fireflybob]

Can anyone tell me how they know who was making the control inputs on AA 587?

How do we know that the LHS was not applying any control input?

I know there are pros and cons about taking over control but wouldn't most commanders take over control when the situation starts to get really serious?

None of these questions is intended to criticise the flight crew - just for info.

[Carol24]

I have all the details of the Interflug A310 incident in my files. Pls let me know if you are interested in some specific details. Excuse my "german" english pls.

[Wino]

It has not actually been determined that ANY pilot made the controll inputs into 587. It has been INFERRED that the pilots made the controll inputs.

There was an incident at AA in the past where an autopilot clutch did not disengage from the rudder axis and submitted the aircraft to extreme yaw motions back and forth including movement of the rudder puddels by the autopilot. The aircraft was landed in Miami with damage. The A/D that resulted from that incident found another aircraft with a similar problem (in a nutshell it was a wire chafing problem)

Cheers
Wino

[timzsta]

Am only a humble APTL student and PPL holder, but I watched the Horizon programme with great interest.

As part of my course I recently read the UK CAA's circular on Wake Turbulence (AIC 17/1999, Pink 188, 25 Feb, for those in the UK). The thrust of it, especially the latter half is that avoidance is the key.

The Horizon programme compared the flight paths of the JAL 744 and the A300, noting that the A300 turned inside JALs track, and that this meant the wake vortex had drifted down to the A300's track position - hence the encounter.

My first question is were both aircraft flying a SID or not, and if they were, was the portion of the SID in which the accident occured (ie the left climbing turn following departure) a part in which there was no track guidance? (I believe the ICAO stuff on track guidance states track guidance to be achieved within 10km for a turning departure). If both follow the same track, given the wind drift the A300 should not have encountered the 744's wake.

Having been warned of wake turbulence danger, how much consideration was given to their intended flight path with regard to where JALs wake was likely to be - namely turning inside is probably not a good idea. Given the wake turbulence drifts down I was also surprised that the A300 was not above JALs wake, as I would have expected an A300 to outclimb a 744. Overriding this it must be said that there is still much to learn about wake turbulence encounters.

Perhaps of more alarm to someone who is working toward a career as a commercial pilot was Airbus Chief Test pilot saying that wing low should only be corrected with aileron, even at high pitch angles. When taught to fly from day, albeit in Cessna and Piper, we are taught correct wing low at high pitch angle and low speed with rudder. Using aileron will may result in stalling the wings. The problem IMHO in this area lies in the fact that handling a commercial jet and a light training aircraft are completely different - and the problem is that there is little training to bridge the gap. That said I believe from earlier posts the variant of the A300 concerned had no outboard ailerons, hence stalling the wind by applying aileron at high pitch angle following a wing drop maybe unlikely on this particular aircraft type. Thoughts? If this is the case - does the Operating Manual for the aircraft make comment on this? (as required by the JAA regulations concerning handling characteristics unique to the aircraft).

It has all certainly made me think about how I will use the rudder in future in my little C152 and PA28.

Finally from ICAO Annex 13 - Accident Investigation."The sole purpose of accident investigation is to prevent repetition, not to apportion blame". It seems once again all and sundry are concerned with avoiding being blamed, whilst perhaps the true reason for the deaths of several hundred people has not been found.

[fireflybob]

>When taught to fly from day, albeit in Cessna and Piper, we are taught correct wing low at high pitch angle and low speed with rudder. <

timzsta, the points you make are well put.

However, if you have been taught the above then, I believe, you were taught incorrectly.

Many years ago, part of the stall recovery was to "prevent further wing drop with rudder" which is not the same as "correct wing low...with rudder". This part of the recovery was then omitted since it was believed (correctly,I think) that use of rudder near the stall was more likely to induce a spin. All these remarks apply to light training aircraft not swept wing jet transports.

However, in the case of AA 587 they were not in a stalled condition but pilots can revert to old procedures when under pressure.

[AhhhVC813]

Pom,
exactly what pilots are you referring to when you remark that almost all pilots universally dislike non moving throttles? Presumably, you must be speaking from personal experience, as most Airbus pilots I know don't give it a second thought as to whether they move or not. They certainly don't dislike them. If you mean most Boeing only pilots dislike them, then that is rather different, and again, pretty meaningless, as you can hardly criticise something you haven't tried.
And of course there are differing approaches from the two manufacturers; whether one is engineering as opposed to pilot led, is a matter that restarts the whole very tiresome debate of which is supposedly the better producer of commercial aircraft. Ultimately, if you are fortunate enough to be operating either manufacturers product then you are fortunate indeed.

[411A]

Timzsta,
Having personally done full stalls in two heavy jet types, can positively say that a wing is NOT leveled with rudder...if you do, the blue side definately does not remain up, needless to say, BAD.:sad: :oh:

[Notso Fantastic]

Timzsta, you're chasing a red herring about the wake vortex issue. What is the alternative- to take out every airport that has a heavy jet movement for 10 minutes until it has completely dissipated? Wake vortexes are something we have learnt to live with acceptably- it was not the wake vortex that caused the crash, it was just a link in a chain like an aeroplane crashing on a fog approach- it's not the fog that is the cause, rather the procedures and handling of the situation. All jet pilots fly through wake vortexes, it is unavoidable. One just has to ensure that the short duration encounter is handled.
Before proper separation standards were imposed, we got caught once flying up the core of one very close to where AA crashed. On a Canarsie approach into JFK just after Canarsie onto R/W 31- slow and low. I was handling and it took almost full aileron on a VC10 to attempt to keep level. Once 'stabilised', it then took an interesting few seconds to exit it! An immensely powerful phenomenon- I have no doubt something smaller would have ended up upside down. But the separation standards we have now are adequate- it's other things that must be examined.

[Synthetic]

In case anyone wanted to see the Horizon on the accident but missed it last week, it is being repeated tomorrow morning on BBC1 at 03:05 ( Get the kids to set the video:D )

[Jetstream Rider]

Didn't manage to see all of the prog on telly, but a couple of questions:

The wake vortex encounter did not look particulary bad and the supposed contol inputs look excessive for such a manouvre. How bad in the opinion of jet pilots was the encounter?

My own feeling is that the control inpts were either caused by a mechanical/software problem (similar to Wino's posts) or two pilots trying to control and perhaps adding to each others actions (although I doubt that). However that is only a feeling and I would have to see a lot more evidence to actually decide that.

My commercial experience at the moment is on a small turboprop and I am training onto the 757 at the moment so I read the discussion about rudder with interest. Certainly in the Jetstream I never used rudder (or thought about it) to correct turbulence or wake encounters. I was however a little bit excessive on my briefings about thunderstorms when first out of training and talked about pitching to the stick shaker in the event of windshear, mostly due to some weather videos I had seen discussing microbursts and my sim training. That was when I was just starting my career though - unlike those in the accident.

Secondly, a question about training. The AA trainer on the programme said he had never heard that a reversal was bad news (which really surprised me, as I thought it was bad), yet all big aircraft manufacturers susequently said it was. Now what else are we missing? It seems to me that basically as airline pilots we are trained to fly from A to B on a normal sort of flight. We are also trained to deal with engine failures/fires etc and the multi crew bit which is all good stuff. But how much handling do we really do? How many people really understand the envelope of an aircraft? When you become a trainer, what extra handling/engineering type training do you get? If there is none, then the guy who teaches you in the sim or on line and tells you what you can and can't do is not in a position to tell you in some respects. This became apparent to me when a training captain with a non technical background told me things that turned out to be totally wrong about a bit on the aircraft (contrary to my technical training and another engineers view). Perhaps this will start to age old discussion of do we teach (for instance) spinning, or just how not to get into one? My point is that we appear to be missing some important aspects of flying. Certainly the upset training on my ATPL course was minimal and the spinning training was poor, with most people not really knowing what it was all about. I do not say this as a criticism of any airline or training establishment, but more of the culture we have in the airline industry. Also, I do not add this bit to say that the pilots caused the accident, but to widen the discussion as to the quality of our training and abilities. Comments welcome.

[411A]

Jetstream Rider,
Having read Davies well authored book (Handling the Big Jets, first printing) in 1968, I approached large heavy swept wing jet transport aircraft wanting to know as much as possible.
Beyond the sim, and in the aircraft, have many scars from the training Captains of the time telling me (thumping bigtime)...keep OFF the #@%&* rudder, unless an engine should fail (shutdown) or landing in a crosswind....period.
Lessons learned a long time ago should never ever be forgotton, and in my opinion, AA and their training, have a lot to answer for.

Sadly, many younger guys will never know...:mad:

[Notso Fantastic]

The AA boys are understandably trying to protect the reputation of one of their own and their training system. This encounter requires examination beyond that. I think it was probably one of the more serious encountres that lasted longer than normal as they were probably caught in the core and flying pretty well up it. There was no joint wrestling with controls, the NHP would always announce he was getting involved. It depends on his background how aggressively the controls are handled. I think the vast majority would not react so strongly, which is what the aeroplane manufacturers obviously intended judging by their subsequent advice. I don't think the Airbus is at fault in any way. A sad incident and time for us all to digest exactly what the rudder is for and how it should be used. The vast majority of us are aware that the rudder/fin is to be handled 'delicately'.

[Jetstream Rider]

Quote: "Having read Davies well authored book (Handling the Big Jets, first printing) in 1968, I approached large heavy swept wing jet transport aircraft wanting to know as much as possible".

Me too, I read "Handling the Big Jets" before I started my type rating and am not content with only being able to fly from A to B. However, in the past, whenever I have asked to do anything out of the ordinary I get a "why would you want to do that?" response, or a "but you'll never need to". I begged one of my ATPL instructors to let me fly in icing for instance (in a suitably equipped aircraft I hasten to add), but he couldn't understand why I wanted to. It is that sort of attitude that I think needs to be taken out of aviation. If it is left to the student's motivation to find out about the aerodynamics and loads on an aircraft, then most will miss out on important knowledge, as frankly humans can be very lazy.

I will watch with interest what this accident report will say as I still cannot believe, that even if AA taught the use of rudder, that the actual control movements were the intended inputs. But I do think that from the comments of many pilots about the rudder that our training could cover more aircraft envelope/response training and that it is very important.

[Anthony Carn]

timzta/any light aircraft pilots

With apologies for going off topic (?), whatever is correct for your Cessna/Piper light aircraft may not be correct for a swept wing airliner. There may be a dangerous trap in transferring what you read herein to your light aircraft flying. Be wary.

Ask your instructor/training captain, as applicable to whatever you're flying, for clarification.

What you're reading in this thread applies to a particular swept wing airliner (which may, itself, have individual peculiarities).

[Flap 5]

I thought the program was good, except for the reference to the Interflug incident which was nothing to do with vortex turbulence - but the engagement of TOGA mode instead of Go Around mode.

I was very surprised at the AA chief pilots assertion that he had never heard that you should not treat the rudder control with such violence. The rudder control is very powerful in a heavy jet.

[fiftyfour]

Swept wing aircraft, when they stall, become uncontrolable. When the wing drops, that wing tip then stalls. Because the wingtip is well aft of the centre of lift, the nose continues to rise while the wingtip continues to fall a little. There is no recovery possible - even with small rudder input to stop the wing dropping because the huge amount of lift inboard ( and forward of the c of g), at the now increasing high angle of attack keeps the angle of attack increasing to an uncontrolable pitch. Some military aircraft have a huge fully movable tailplane and massive excess(combat) power to save the day in such an encounter, but certainly not in a bog standard transport design. Civil aircraft have stick shakers, pushers, nudgers and so on to help prevent getting anywhere near the full stall, from which there will be no recovery. Rudder is not part of the procedure here and never has been. In theory, a little bit of rudder will help to stop the dropping, but the secondary effects are enormous and difficult to counter accurately. Besides, by the time the desired effect is produced the angle of attack of the main wing is beyond correcting.

Rudder is not part of the procedure for controlling an aircraft upset when just about to stall either. Surely you fly yourself out of the problem using any height available. If there is insuficient height available then a crash is inevitable.

In the AA accident, the speed and g involved shows the aircraft well above the stall. If they were not stalling, then surely they should use the available height to fly out of the problem.? If they (and not a rogue autopilot or control surface) did indeed apply those control inputs, it seems they might have been in too much of a hurry to get the aircraft back on an even keel, and were not prepared to use their height for recovery.

Regarding the Interflug A310 in Russia. On my 6 week Airbus course at Toulouse, this incident was a central part of our one day flight safety seminar. They spent 2 hours covering the incident with video reconstruction from the digital FDR ( possible because the aircraft subsequently landed safely). There was no attempt to cover up Airbus deficiencies. The crews problems were not aggravated by use of rudder. The crew could, however, have prevented the subsequent aerobatics during recovery by using the controls to fly out of the problem. No mention or suggestion on this course that the crew should have, or should not have used rudder. I'm surprised that the TV documentary used this serious incident in their programme - it was irrelevent.

[CraigL]

I'm surprised that the TV documentary used this serious incident in their programme - it was irrelevent.

Yes, but nevertheless spectacular - got to give them a bit of dramatic license, being a TV programme.

[Flap 5]

fiftyfour,

Swept wing airliners certainly are controlable in the stall. It is one of the first things covered on any type conversion. From your description you appear to be refering to the problem of spinning an airliner.

High tail airliners do have a problem in that the high nose attitued causes the airflow over the tailplane to come directly from the disturbed air of the wings, this leads to a deep stall.

However your post has nothing to do with the topic under discussion which refers to the vortex wake turbulence incident of AMR 587 which became an accident after incorrect pilot control inputs of the rudder.

[Notso Fantastic]

54, you are, I believe, holding a few misconceptions. Airliners are designed so the last bit of the wing to stall is the wingtip. There is a discussion on this in TECH LOG-'Windshear Question'. You don't want the wingtip to stall first because it would give a powerful nose up moment at a disastrous time, and if asymmetric would turn you upside down. So you see design tricks on most aeroplanes to prevent the tips stalling before the wing:
1- reduced sweepback towards the tips
2- reduced incidence
The 747 most certainly remains very controllable in a stall- it wallows and behaves very well.

We are starting to chase our tails with this discussion, with a massive amount of irrelevancies being brought in! There was no stall. It was nothing more than a powerful wake encounter- something experienced by most professional pilots. It's a matter of technique.

[Raas767]

I have not been following the investigation of 587. Nor have I read all the threads speculating on one thing or another. I am not an engineer, nor did I fly in the military. I have, however, flown commercial jets for 11 years, turboprops before that and spent a few years instructing before that.
Never in my training or in any aircraft manual that I can recall did it mention any warning concerning rudder reversal. On the contrary, everything I have read says that bellow Va FULL use of flight control is permitted without overstressing the airframe. AFTER 587 we received all kinds of training and warnings about prudent use of rudder. That being said, perhaps the manufacturer never imagined a pilot using the rudder so aggressively. I certainly never would in a wake encounter and I doubt First Officer Molin did either. As a matter of fact the last thing I read about the speed of the rudder deflection would make it physically impossible for him to even move the rudder that fast. Coupled with the history of uncontrolled rudder movement on the A300 on two previous occasions involving AA aircraft alone I would suggest caution before we nail these two gentleman to the proverbial wall. I had the previlage of flying with both of them on separate occasions on the 727 and found them to be very competent aviators.

[Groaner]

Not meaning to hijack the thread, but this is an excerpt from the current issue of "The Economist" - usually a reliable magazine (in an article about counterfeiting):

At least as hazardous is the trade in counterfeit car parts, which may account for as much as 10% of the spare parts sold in the EU, according to a 1999 study. Even more worrying is the thriving trade in reconditioned aircraft components, passed off as genuine parts along with fake certificates of authentication. Last year, police raided three aviation-parts manufacturers in Rome, seizing more than $2m-worth of used parts—modified and repackaged to look as good as new.

Dodgy aircraft parts kill. In 1989, a plane belonging to Partnair, a Norwegian charter airline, crashed when its tail assembly fell off because of substandard counterfeit bolts holding it to the rest of the body. The CIB believes that the November 2001 crash of an American Airlines flight over New York may have been caused by the failure of counterfeit parts.




Has anyone heard anything about fake parts being used?

(Note to journalists: this is entirely hypothetical, and may well be a case of mistaken identity or similar)

The "CIB" they are referring to is the Counterfeiting Intelligence Bureau (CIB), part of the International Chamber of Commerce.

[Anthony Carn]

Raas767
..........everything I have read says that bellow Va FULL use of flight control is permitted without overstressing the airframe.
Va relates to wing stall before overstressing of said wing. It certainly does not include the use of full rudder.

If Va included full rudder useage at wing stall, then you'd be authorising FLICK ROLLS, on any aeroplane, provided you're at or below Va ! :eek:

If that's your interpretation, then please let me know which airline you fly for and I'll avoid it ! (only joking).

I just could'nt let that one go, sorry if it's off-thread.

(Fundamentally, we need to agree here that full rudder useage is'nt something that's necessarily permitted or necessary, except for single engined operation and (in an extreme case) landing. Fins are "easily" overstressed.)

[Flap 5]

Raas I do not believe the pilots are being condemned on this one. According to the tv program it was the airlines procedures that were being criticised. They should have known better. But, as usual, the threat of litigation means that the lawyer heavyweights come out to protect the airline. The senior pilot in the documentary also made a strange statement where he stated he did not realise that full rudder deflections would cause excessive stress on the airframe. This statement must have been prompted by the concern by the company of litigation.

Unfortunately the litigious society of the US does not encourage the revealing of the truth. It is also going that way in the UK too now, which is a great pity to say the least.

[Raas767]

I just did some thumbing through my old college text books. Not a very thorough search but I did not find anything warning about rudder reversal. When I was in Europe converting my ratings I do not recall being specifically warned about it either. I am not surprised that one of our chief pilots claimed ignorance. If anyone at the training acadamy or at the manufacturer knew then they certainly did not tell us. Other line pilots have said the same thing. Military pilots with engineering backrounds seam to be the exception.
Like I said, For the pilots to have moved the rudder as fast as the FDR suggest it would have been a super human feat. I still maintain that the rudder malfunctioned.

One more thing. Not that any pilot that I know spends anytime dancing on th rudder pedals, I do remember a post here a few months ago regarding something in the A300 manual. I think there was a PROCEDURE there to move the rudder back and forth in order to get the gear down if there was a malfunction. I am not positive about that but maybe someone that flies the jet could check it out.

One more thing. Not that any pilot that I know spends anytime dancing on th rudder pedals, I do remember a post here a few months ago regarding something in the A300 manual. I think there was a PROCEDURE there to move the rudder back and forth in order to get the gear down if there was a malfunction. I am not positive about that but maybe someone that flies the jet could check it out.

[fiftyfour]

Flap5 and Not so Fantastic.
If you know the B747 can be stalled and then 'wallow down' in the stall due to the good aerodynamic features like washout etc etc, that you mention, then I stand corrected.
Thanks.

[Flap 5]

Raas,

The 'book' on any aircraft will say many things that do not translate into real life flying. They are often written by engineers. I have many years and thousands of hours of airline flying and one thing I have learnt is that when the 'book' comes up against common sense, common sense wins.

Indeed there may well be a procedure to get the u/c down by moving the rudder. However the person who devised that one clearly was looking at trying to dislodge the u/c by some means. As the pilot you have to consider how kicking the rudder will effect the rest of the aircraft. You don't just do it because 'the book says'.

[Wino]

And Flaps 5

you don't get to make up a procedure or deviate from one just because you think that ain't right.

I am trying to get a copy to post here of what both Airbus and Beoing sent out to all AA pilots. The differences are EYE opening.

That is MORE dangerous.

Cheers
Wino

[fireflybob]

>you don't get to make up a procedure or deviate from one just because you think that ain't right.<

Wino, I don't think Flaps5 is saying that you should do either of these things.

What he is saying is that there is nothing wrong with applying "airmanship" and good judgement - not that I am implying that the crew of AA did not do so.

[Wino]

Fireflybob,

The Airbus manual called for "rapid alternating sideslips" after extending the gear manually untill a 3 green indication is reached.

He is saying that he shouldn't do that, even though the manual clearly instructs it. So if he had the gear collapse after a manual gear extention because he didn't do the alternating side slips then you can bet your ass airbus would be looking to fry him from deviating from their procedures.

While I also have known about doublets, the manual clearly indicated their was a time and a place for them. If you are saying that the manual is incorrect or that it was lost in the translation, then you have a certification issue on the aircraft right there. If the French cannot produce a manual in plain english (the language of aviation) that is both correct and understandable, then they should not be permitted to certify their aircraft for operations outside of france.

Cheers
Wino

[cwatters]

Sorry to go back a bit but...

Has there actually been any research into how humans cope with nonlinear controls (eg like that found on the rudder)? I tried a web search but didn't find anything that lept out at me. It would seem to be important as we are about to get speed senstitve steering in our cars.

Being English and living in Belgium I am used to driving on both sides of the road. I've been living in Belgium for the last 4 years and feel 100% converted to driving on the right - so why did I swerve to the wrong way recently?

Isn't it possible that a pilot faced with a sudden upset might respond automatically and apply rudder travels normally only used at lower speeds?

[Notso Fantastic]

<I've been living in Belgium for the last 4 years and feel 100% converted to driving on the right - so why did I swerve to the wrong way recently?> You're looking at it wrong. You swerved the right way- if they will persist in Europe, along with the Americans, at driving on the wrong side of the road, then it's their fault. You were on the right side of the road (which is the left side), they were all on the wrong side. They'll come around one day.
Pilots having to make large movements on the controls will always have an idea of their speed and the relative safety of large control inputs. Nobody at high speed is going to slam full deflection on unless absolutely essential. Full deflection of the pedal will not produce full design deflection of the control.
.......we go back around in circles in this topic!

[Few Cloudy]

What you say about going in circles is correct Not so Fantastic. I have just taken the trouble to go through this complete thread - God knows what the phone bill will be - but one thing is for sure - most questions and comments coming at this stage have been handled earlier on.

However three thoughts repeatedly occured to me as I did this scan.

The first is that training for jet upsets is creative training to deal with a worst case situation - including tricks to save an aircraft from a hopeless attitude/speed/rate combination. Was this really the situation in which the Airbus found itself? If it wasn't, then the trained upset inputs were inapropriate in this wake turbulence encounter. Whose fault this was we can't say. Training programes have a habit of being taken on board differently and applied differently by different pilots. Let us learn this lesson when writing future programmes.

The next thing is that use of rudder to correct wing drop is only appropriate in a stalled situation. The reason for it is that use of aileron increases the effective angle of attack on the dropping wing, thus in theory stalling it even more. Depending on the design of the aircraft (washout - tip sweep reduction ) and where and to what extent precisely the wing is stalled, this may or may not be the case. Using the rudder simply to right the ship when the wing is NOT stalled, however, has to be bad advice.

The third thought concerns design. Even the DC-9 family had a rudder limiter, consisting of a horn shaped interference pin fitting into a gap on a traveller directly attached to the rudder. The pin was operated by pitot (dynamic) pressure and was there to allow only appropriate rudder inputs for the engine failure case. If you get the chance, reduce thrust on an engine in cruise to idle and you might be surprised what a very small effect this has on yaw at cruise speed. Thus only a small deflection is required - apart from the fact that the rudder effectiveness increases with speed. The designer was being cautious in giving the pilot the rudder authority he NEEDED to deal with engine failure. It may well be that this authority in certain flight modes would suffice to damage the aircraft if mis-applied in an oscillating sense, for which neither the empennage, nor the rudder has been designed. Again - let us teach our pilots what such use may cause, which is the real reason large jet pilots are not taught, as light aircraft pilots may be, to use rudder in all turn manaoevers.

[Notso Fantastic]

Agreed, especially the 3rd. para. I think it fair to say all pilots who have flown T-Tails give extra care and attention to rudder handling. You want to look after your empenage 'cos there ain't a lot you can do without it! I cannot think of a valid reason for rudder reversal. Certainly not rapid, ever! If you push wrong rudder on in an engine failure scenario, then pushing it the other way is the only conceivable time. The change in sideslip will have to be very carefully handled, even doing it slowly.

The lessons have now been learned........haven't they?

[cwatters]

> .......we go back around in circles in this topic!

Not quite my intention. I too have been back through all 16 pages.

I wanted to know if anyone had seen any research on how well (or how badly) people are able to use variable sensitivity controls. Can people adapt or do they react badly when something unexpected happens? I spent some time looking for papers on the web but couldn't find anything.

I suspect that when someone is "surprised" they subconsiously revert to using controls in a way that represents the sum or average of their lifetime experience, rather than how they are behaving at that particular moment.

Jshg wrote..

>I recall a cross-wind approach some years ago when
>the PF reverted to his previous turboprop type and
>applied rudder in the last 500'.

Wino also made the point..

>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,

I suggest that even if he had adjusted to the increased sensitivity he may have been powerless to prevent himself "reverting" when suddenly surprised by the wake encounter.

A common design issue with all systems that contain feedback is the need to maintain stability and avoid conditions that cause the system to oscillate. Anything that adds a time delay in the loop usually makes this harder to achieve. This paragraph I found on reaction times might be relevant..

http://www.visualexpert.com/Resources/reactiontime.html

>Psychological Refractory Period
>
>Following a response, people exhibit a "psychological
>refractory period." During this period, new responses
>are made more slowly than if there had been no previous
>behavior. For example, suppose a driver suddenly steers
>lefts and then right. The steer-right response will
>occur more slowly because it immediate followed the
>steer-left.

Which seems to imply that when you are trying to damp out oscillation your reaction times are reduced. "Heavy" forces would also add a time delay.

Whatever the true position, it appears the pilot in 587 felt the plane was oscillating and applied several rudder reversals to try and stop this.

(and yes I have read the posts that say he shouldn't have used rudder anyway).

[Notso Fantastic]

I think we are digging into obscure academic areas and chasing our own tails again. It's been talked to death. Variable sensitivity controls are discussed in several previous posts, not least 3 posts before yours.

It's not unusual for pilots to 'cheat' by tweaking a bit of rudder, usually on approach at low speed. Different types have very different responses at this stage. They had a severe wake encounter, full control reversal inputs were applied either automatically or manually. The fin separated. At low flap retraction speed, it is more acceptable to apply full rudder than at cruise speed. It was the reversal that did the damage. Rather than discuss to death the principles of pilot input, I think we should satisfy ourselves that this is not some system error. If it is pilot error, we should all learn by it.

[hobie]

please excuse me if my technical term "Fast Data Recording" is not strictly correct .....

my question ......

"Fast Data Recording" is employed to routinely monitor Pilot/aircraft performance/procedures on large passenger aircraft and to highlight deviations from standard practice or identify "Bad Practice" etc ......

I "almost" get the impression that the PF on this flight may have been the first pilot to have ever used his rudder in the "Aggressive" way that he did (I appreciate that malfunction has still to be ruled out) ......

surely routine data recording would have highlighted over time that Rudders were being used excessively and that load limits etc were being exceeded? ..... or is this almost a "One Off" ? ....

cheers .... hobie ......

[OVERTALK]

Not much is being said about AA587 since Airbus imposed its will upon the last hearing. The pilot error theory

is being supported by the NTSB and endorsed by the FAA. The glitch is more likely (IMHO) to be in the original

design (or introduced later by a software patch)._

And I still like my original theory (below):

So, (in part) addressing these selected quotes:
A. "A good look at the DFDR data does not show rudder movement consistent with a mechanical problem." and
B. "Even the AA flight 903 incident occurred in violent weather and an inflight upset that may have been a stall

or may have been something else."

In Daze of Yaw
The AA587 explanation may be as simple as water getting into the pitot-static lines every time an A300-600

aircraft is washed (or is parked in torrential rain) - and introducing a pressure change damping effect that

cannot be accommodated by the CADC’s pneumatic “expectations” (particularly in yaw). Why would that (i.e.

trapped water) make a difference? It’s not as if it might freeze in the lines and cause glaring static errors

(in airspeed, altitude and rate of climb). The errors might be much more subtle than that. In fact, in normal

flight they might be hardly noticeable. But in strongly yawed flight it could be entirely different. Why would

that be?

Explanation

_The input to the CADC’s is (ideally) purely pneumatic pressures being mildly differentiated by height and/or

speed variations. The CADC as a sensor is capable of picking up very minute pressure changes and rates of change

of pressure variation (as well as temperature increments of course). It feeds the resolved heights, rates of

climb and (of particular interest and significance) current airspeeds to a range of systems – including the yaw

damper and rudder limiter. _If _water is inadvertently introduced into the static lines (say) you then have a

damped and laggard hydro-pneumatic response in all the variables that feed pressure changes into the air data

computers (which will in turn misinterpret these “damaged” inputs and thus apply incorrect outputs). Normally

there will be four or more static ports (holes) – with a couple each side (of the airplane) to guard against

blockage (of a singular one). The siting of those holes is designedly where, in normal symmetric flight, the

smallest PEc (pressure error correction) requirement is generated. Some aircraft have the static ports right up

the front on either side of the nose and some aircraft have them way down back, just forward of the empennage.

Being thus located either well forward or well aft of the aircraft’s vertical (i.e. yaw) axis, the effect of

yawing needs to be cancelled out (and that’s why you have the ports uniformly on the port and starboard sides of

the fuselage). Works well, but how will water trapped in the lines affect the sensed pressures?


When the aircraft yaws due to turbulence (or pilot-pedal input) any airflows injected dynamically into the

static lines are self-canceling because the port and starboard static ports are Y-pieced together. Net effect on

the CADC’s sensed pressures? Not a lot, although extreme yaw can cause airspeed indications to fluctuate wildly.

But what if water has collected at a low point in the static lines – perhaps before the port and starboard

pickups are Y-pieced together?? (even if only on one side). In a sharp yaw to port any water in a starboard line

would tend to flow aft (and water on the port side would tend to flow forwards). What will be the effect of that

on the air-pressures sensed by the CADC and, more importantly, its outputs? At this point I should also

acknowledge that some modern systems (but probably not the A300) do incorporate air pressure transducers that

convert what is sensed to a digital signal that then goes to the CADCs. But whether those signals were valid or

not would depend on the location of those transducers. Because the CADC senses both quantum change and trends,

there will be at least a lag and more likely a contrary signal generated by the adverse flow of water affecting

the line pressures. Any correction fed to the rudder actuator by the yaw damper might then be inappropriate in

both magnitude and direction. So where is this error headed? Will any initial wake-induced yaw be damped out or

magnified by the yaw damper in this scenario? Will the erroneous CADC signal cause an initial significant yaw to

overshoot equilibrium and, in fact exacerbate the L/R yaw cycle? (i.e. "set the ball rolling" for some

rudder-supported extreme yaw cycling).


My theory says that YES, if the initial externally-triggered yaw is large enough, it could do that. If an

inappropriate correcting rudder deflection is commanded because of water trapped in the static lines and the

wrong airspeed being sensed - and the yaw correction consequently overshoots significantly, then we are into a

rudder-inspired undamped phugoid around the yaw axis. And beyond that “threshold of significant external yaw”,

because of the great stabilizing influence of the large vertical fin, any out-of-phase rudder control inputs

would be amplified and rapidly approach the point where something has to give (structurally). And that is what

I’m guessing may have happened in AA587. It might explain why much anecdotal evidence of tail-wagging is quite

irregular – possibly because static line water trap drains are cleared out on (just guessing) each C service (or

might be even more regularly)._ Then the aircraft's unalarming (but irritating) tail-wag phenomenon would

disappear overnight without comment. That would explain why particular airframes don't get (and keep) a bad

reputation.


So the theory really says: "You'd need to unluckily combine a waterlogged static system and a wake turbulence event (with

its large amplitude yaw “kick-off”) to end up generating an AA587 event".


In my scenario is there any scope for pilot complication or compounding of the wildly yawing initial scenario

(prior to structural failure)? The easy answer is: “Of course”. No pilot is going to sit there and allow the

airplane to swing wildly from side to side. He will at least attempt to counter the yawing with judicious rudder

pedal inputs (at least I would). But whether he could be successful (or just get out of phase himself and

exacerbate the situation) is the real quandary. Would the other pilot be aware of any such intervention on the

part of the PF (pilot flying)? Not really – and the whole thing would happen so fast that there’d be little

chance for anything further than the gasped expletives heard on the AA587 CVR.

How could you test this theory? The easy answer would be to “water” an A300-605 and go out and see whether

atmospheric disturbances or pilot pedal input could bring about any strange unexpected yawing responses. Another

approach would be to monitor the static-line water-traps across the fleet, measure the amounts of water found

and note whether aircraft washes (or heavy rinses) increased this amount.

Addenda
To specifically address this input by ALPA: (particularly the observation in blue)
<<"As I understand it, the A300 -600 was being hand flown at the time of the upset._ So the autopilot

would not have been engaged._ The A300 is not a fly by wire airplane._ It is conventional hydraulic controls so

the FCS electronics would be very limited._ The yaw damper would be active but the rudder

swings far exceed the authority of the yaw damper (it is mechanically limited)._ So, based on the DFDR, I do not

see any airplane issues based on flight control malfunctions.">>

Apart from the sampling issue with the AA587 DFDR meaning that the number and size of AA587's rudder deflections were not determinable, you

would not need max deflection rudder authority for a yaw-damper-actuated rudder to achieve large yaw amplitudes.

It's the timing of the actuator inputs that would be critical. I used to do a low-level jet aero display that

incorporated extreme yawing cycles on a flyby. Rudder authority was such that the last thing you wanted to do

was to stall the vertical fin - so you needed a keen sense of timing when "walking" the rudders somewhat

gingerly so as to achieve peak yaw in each direction. It is quite possible to achieve extreme yawing angles

(talking about > plus/minus 30 degrees here) by just getting the timing right. In addition to that, do not

disregard my opinion above - that any pilot (PF) would instinctively intervene (and perhaps disastrously) once

an identifiable cyclic yaw was underway.

[OVERTALK]

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).

[DownIn3Green]

Overtalk...

Is the correct screen name here...am I the only one confused by this "overtalk"?

[Dagger Dirk]

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.

[Belgique]

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. :-)

[Ignition Override]

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.

[Belgique]

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

[OVERTALK]

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.

[Ignition Override]

Interesting, Belgique. Thanks for the reply-merci.:)

[Bubbette]

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

[TheShadow]

see this link (http://www.iasa.com.au/folders/Safety_Issues/FAA_Inaction/AA_co.htm) for the American Airlines bottom line on the AA587 crash

theShadow
http://www.iasa-intl.com/folders/images/lionofjudah.gif