Don’t tell Evan

[3WE]

Anyway, I’m not out to win.

Just totally closed-minded that the system might have been overly sensitive to well-meaning and possibly very reasonable inputs.

As Gabriel said, a system requiring 0.4 Corgi-lengths and 0.005 Elephant weights of force would be incredibly unlikely to have its tail busted off due to its conspicuous feedback to the pilot.

I would also add a huge “so what” to your sample of six simulated events where pilots didn’t break the tail off…Who knows how many millions yaw corrections pilots make (See Brianies YouTube) and multiply that by a system where 0.05 Corgi lenths and 0.001 Elephants will slam it to full deflection…

[Evan]

Just totally closed-minded that the system might have been overly sensitive to well-meaning and possibly very reasonable inputs.

How close minded can a person be 3WE? I just posted the effing FCOM from the big airplane company stating in very BLACK AND WHITE terms that the rudder is not to be used to control roll (for very important reasons)... and furthermore, never to be used in reversals (for very important reasons). Therefore, it is impossible for such inputs to be very reasonable. I'm beginning to think you might have a reasoning disability.

[3WE]

I just posted the effing FCOM from the big airplane company stating in very BLACK AND WHITE terms that the rudder is not to be used to control roll.

Pretty sure I said nothing about using the rudder for roll control.

However, it is widely used for yaw. Given your years on this forum, I figured you would have learned that by now.

I hesitate to tell you this (a gray area), but it can, indeed, cause a roll response, but pilots really avoid such uses for the vast majority of flight. Snap rolls are cool, though. And, yes, it is mentioned in some upset recovery scenarios. Did AA-587 get upset, or was it just waggled a bit?

Another non-black and white thing for you to work on is that wake turbulence generally disrupts all three axises of flight.

[Evan]

Pretty sure I said nothing about using the rudder for roll control.

Pretty sure you're on the wrong thread. These were wake turbulence roll disturbances from trailing vortices. If you look closely at the A300, you with spot a very large vertical stabilizer that is there to stabilize any yaw disturbances. Could you please tell us how the his use of rudder was possibly very reasonable in the case that we are actually discussing?

That's a rhetorical question. You can't give a reasonable answer because there isn't one. Sorry, there's no grey area to hide in. Black and white as it gets 3WE.

[Gabriel]

I also believe this pilot would have broken the A330 or the 747. It just might have required more work.

Ok. I don't. Increased forces and displacement required for a given control input are a known deterrent top PIO. Not that it is impossible, but it becomes more obvious and, especially, more bodily physically challenging. Remember that work = force * distance. So 3 times the force * 3 times the distance requires about 10 times the amount of work. Now repeat that work 10 times. It may even become exhausting to the point that it is really hard to do, and to do fast, which was required for this to happen.

[Evan]

Ok. I don't. Increased forces and displacement required for a given control input are a known deterrent top PIO. Not that it is impossible, but it becomes more obvious and, especially, more bodily physically challenging. Remember that work = force * distance. So 3 times the force * 3 times the distance requires about 10 times the amount of work. Now repeat that work 10 times. It may even become exhausting to the point that it is really hard to do, and to do fast, which was required for this to happen.

I hope you are right. As for PIO being obvious, that's the inherent problem in using rudder for roll. The inherent delay of induced roll leaves it as more of an open-loop system, the kind of system that inspires overcontrol in the first place.

But the BEA argued that it might not have even been PIO:

III.B.1: Bearing in mind all of the reservations expressed on this report, it does not appear to us to be convincing to state that the PIO phenomenon has been clearly established just on the basis of observations made on oscillation frequencies. We note that following the first right open loop rudder input there was a first rudder doublet over a period of two seconds, stabilization for two seconds and then a second doublet over a period of two seconds. These observations do not lead to the conclusion that there is a cyclical phenomenon. It is likely that the pilot reacted to unusual perceptions and that his actions in turn reinforced his perceptions.

In that scenario, I think you can also break an A330 or a 747. In any case, I think you will agree that it isn't something we want to find out.

[Gabriel]

Evan, all this discussion started with this.

3WE: When the A-330 crashed in New York back in 2001, after the tail broke off...
Gabe: A300. And the difference is not minor. This accident would likely not have happened in an A330.
Evan: What makes you say that?
Gabe: A300 small pedal force and displacement required to effect full rudder deflection vs rudder-ratio approach in the A330 which requires full pedal force and deflection to effect full rudder deflection, and the influence of that difference in PIO

Are you ok with that? Any objection? (other than you don't agree with the likelihood of this accident not happening in the A330, which I addressed in my previous comment)

Did I say, at any point, that the pilot used rudder correctly? No. Because I don't think he did.
The pilot was incorrectly trained and was known for using the pilot aggressively. The way he used rudder was undoubtedly a cause of this accident.
This accident would have not happened if the pilot had not used rudder incorrectly, which means used rudder at all.

Now, realize that this pilot's intention was not "let's go for max overswing, bang, max overswing to the other side, bang". It was most likely "oops, turbulence, plane went left, let's put some right rudder... opps, too much, let's put some left to compensate, oops too much, let's put some right". It is still bad, ok? I am not saying that it is ok.

1) This accident would have not happened if he had not used the rudder, what is what he should have done, I mean not done, I mean, you know.

2) But this accident would not have happened, and yes this is opinion, in an A330 which is the only thing I intended to say initially, because its rudder design is much less propense to PIO, especially full rudder rudder reversals PIO.

3) Also, this accident would likely have not happened in a Boeing, because Boeing has an internal requirement for a design load of full rudder max overswing followed by full rudder reversal, once. While repeated overswings would have caused higher loads, there is a safety factor between the design load and the ultimate failure load (generally 1.5, but Boeing uses 1.2 for this because this condition is not a regulatory requirement for certification). And also, and perhaps more important, this scenario is assessed at Va, and they were still below Va. Which takes us to...

4) This accident maybe would not have happened if all we pilots were correctly trained in what Va means and in particular what it means for the rudder. There was a false common knowledge that Va meant the speed at and below which the plane will not break up due to aerodynamic loads. no matter the pilot's control inputs. Even I fell in that false known truth, despite having studied the correct concept, using the correct concept when designing an airplane in college, and teaching the correct concept when teaching Aerodynamics in college. If I had seen this pilot doing what he did and I knew he was below Va, back then, I would have thought that what the pilot is doing is horrible but not dangerous. Which was of course wrong.

All the points except point 3 have been addressed. There is better training now in upset recovery, Va, and rudder. As far as I know all planes are using rudder ratio now instead of variable pedal stops. The only one that is not addressed is 3). I would wish it would be addressed because there are times where a max rudder input to oppose max overswing may be the correct course of action. For example, if you have an engine failure close to Vmc and you are a bit slow in applying rudder, you may end up applying max opposite rudder at the point of max overswing. And you HAVE to do it there. Of course, Vmc is much lower than Va, so all will be right. But I don't like having special cases and exceptions and decision diagrams of when it is ok or not to do something. Of course you need to have those decision points, but the fewer the better. I would like Va to approach more the false concept of being the speed at which "you cannot break upo the plane".

[Evan]

Evan, all this discussion started with this.

3WE: When the A-330 crashed in New York back in 2001, after the tail broke off...
Gabe: A300. And the difference is not minor. This accident would likely not have happened in an A330.
Evan: What makes you say that?
Gabe: A300 small pedal force and displacement required to effect full rudder deflection vs rudder-ratio approach in the A330 which requires full pedal force and deflection to effect full rudder deflection, and the influence of that difference in PIO

Are you ok with that? Any objection? (other than you don't agree with the likelihood of this accident not happening in the A330, which I addressed in my previous comment)

Did I say, at any point, that the pilot used rudder correctly? No. Because I don't think he did.
The pilot was incorrectly trained and was known for using the pilot aggressively. The way he used rudder was undoubtedly a cause of this accident.
This accident would have not happened if the pilot had not used rudder incorrectly, which means used rudder at all.

Now, realize that this pilot's intention was not "let's go for max overswing, bang, max overswing to the other side, bang". It was most likely "oops, turbulence, plane went left, let's put some right rudder... opps, too much, let's put some left to compensate, oops too much, let's put some right". It is still bad, ok? I am not saying that it is ok.

1) This accident would have not happened if he had not used the rudder, what is what he should have done, I mean not done, I mean, you know.

2) But this accident would not have happened, and yes this is opinion, in an A330 which is the only thing I intended to say initially, because its rudder design is much less propense to PIO, especially full rudder rudder reversals PIO.

3) Also, this accident would likely have not happened in a Boeing, because Boeing has an internal requirement for a design load of full rudder max overswing followed by full rudder reversal, once. While repeated overswings would have caused higher loads, there is a safety factor between the design load and the ultimate failure load (generally 1.5, but Boeing uses 1.2 for this because this condition is not a regulatory requirement for certification). And also, and perhaps more important, this scenario is assessed at Va, and they were still below Va. Which takes us to...

4) This accident maybe would not have happened if all we pilots were correctly trained in what Va means and in particular what it means for the rudder. There was a false common knowledge that Va meant the speed at and below which the plane will not break up due to aerodynamic loads. no matter the pilot's control inputs. Even I fell in that false known truth, despite having studied the correct concept, using the correct concept when designing an airplane in college, and teaching the correct concept when teaching Aerodynamics in college. If I had seen this pilot doing what he did and I knew he was below Va, back then, I would have thought that what the pilot is doing is horrible but not dangerous. Which was of course wrong.

All the points except point 3 have been addressed. There is better training now in upset recovery, Va, and rudder. As far as I know all planes are using rudder ratio now instead of variable pedal stops. The only one that is not addressed is 3). I would wish it would be addressed because there are times where a max rudder input to oppose max overswing may be the correct course of action. For example, if you have an engine failure close to Vmc and you are a bit slow in applying rudder, you may end up applying max opposite rudder at the point of max overswing. And you HAVE to do it there. Of course, Vmc is much lower than Va, so all will be right. But I don't like having special cases and exceptions and decision diagrams of when it is ok or not to do something. Of course you need to have those decision points, but the fewer the better. I would like Va to approach more the false concept of being the speed at which "you cannot break upo the plane".

Ok, yes, I agree that this wasn't an A330 and that the A330 is a better, more tolerant system. I agree with you that no rudder was called for here. I acknowledge points 1-4. But I don't agree that this accident likely wouldn't have happened on the A330 because I think he was just getting started and actually amplifying the upset with intentional rudder reversals. I think he was doing this intentionally because he was trained to use rudder in high-bank (exceeding 90deg) wake upset recovery on smaller airplanes in situations where ailerons become ineffective. And I think he just... didn't... get it. Supporting this is the testimony of other pilots who flew with him who remarked that he had an alarming tendency to be very active with the rudder. He used it as a primary flight control. As for the overswings, that is what we can expect on any large airplane from an open system that does not provide the expected feedback in time to inform and mitigate the input force. I think he would have broken the A330 or the 747 but with more work and a bit more time. He had been taught mad airplane-breaking skills.

Essentially what I am saying is: what he did, intentionally, is potentially catastrophic to any large airplane. None are immune.

[3WE]

Pretty sure you're on the wrong thread. These were wake turbulence roll disturbances from trailing vortices. If you look closely at the A300, you with spot a very large vertical stabilizer that is there to stabilize any yaw disturbances.

Aircraft with vertical stabilizers don’t yaw.

And wake vortexes cause nothing but roll.

Got it.

The thing that is so uber cool is realizing how many tailless airplanes I’ve ridden in.

https://youtu.be/YP3W-E0OamU

[Evan]

Aircraft with vertical stabilizers don’t yaw.

And wake vortexes cause nothing but roll.

Got it.

The thing that is so uber cool is realizing how many tailless airplanes I’ve ridden in.

https://youtu.be/YP3W-E0OamU

This was a roll upset.

RUDDER SHOULD NOT BE USED - To counter roll induced by any type of turbulence

That's coming from the people who slide ruled the airplane into being. They are much smarter than any of us (except Gabriel).

Notice the lack of grey area there. Notice that Gabriel has noticed this.

It's come to the point where I have to ask you: are you capable of learning?

[3WE]

This was a roll upset.

An upset?

Heck, I think all bank angles were less than 30 degrees until the cheap composite tail let go.

[3WE]

Notice that Gabriel has noticed this.

I notice that you refuse to notice that Gabriel said this crash was unlikely with airplanes with non-amplified rudder control systems.

I notice that you can’t comprehend that light rudder inputs are part of flying almost all planes, including this very airplane during takeoff and landing.

I notice that you still believe the pilot was intentionally slamming the rudder left and right.

I notice that you have no idea what could happen when a vertical stabilizer moves through laterally rotating air…it likely would push it one way, then the other, likely causing uncoordinated flight.

I notice that you can’t comprehend that a system that takes quick, light rudder PEDAL inputs (that are almost universally used) and turns them into full rudder deflections might be a big contributing factor…Gabriel said this, too.

[Evan]

I notice that you refuse to notice that Gabriel said this crash was unlikely with airplanes with non-amplified rudder control systems.

I notice that you can’t comprehend that light rudder inputs are part of flying almost all planes, including this very airplane during takeoff and landing.

I notice that you still believe the pilot was intentionally slamming the rudder left and right.

I notice that you have no idea what could happen when a vertical stabilizer moves through laterally rotating air…it likely would push it one way, then the other, likely causing uncoordinated flight.

I notice that you can’t comprehend that a system that takes quick, light rudder PEDAL inputs (that are almost universally used) and turns them into full rudder deflections might be a big contributing factor…Gabriel said this, too.

Well, then stick to Cessnas please.

[3WE]

Well, then stick to Cessnas please.

I will, but that doesn't change the fact that I didn't crash this plane. A highly trained, regulated and screened pilot did.

[Evan]

I will, but that doesn't change the fact that I didn't crash this plane. A badly trained, regulated and screened pilot did.

A Cessna does not have a yaw damper. You use the rudder quite often for turn coordination and to deal with adverse yaw.
Airplanes with a relatively sort wing span make it possible to roll into high-bank angles in wake turbulence where rudder might be needed to recover (not rudder reversals).
An A300 (or any large jet) does not need rudder for turn coordination or adverse yaw compensation, nor does it roll into high-bank angles in wake turbulence.
Large jets need rudder in one direction for crosswind landings, thrust asymmetry, and both directions for ground handling and some ultra-rare circumstances like shaking the gear loose on gravity extension and shaking the hijackers off their feet. That's it for rudder.