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He stepped on the Rudder and redefined Va

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He stepped on the Rudder and redefined Va

Old 29th Sep 2013, 09:22
  #81 (permalink)  
 
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Snoop

Originally Posted by Owain Glyndwr=
To go back to your original post, could you please point me towards the actual FAA change to Va? I failed to find it.
I failed too. Teldorserious, could you help please?

Thank you dsc810. Gliders are not built like airlines, but it is assumed that starting piloting with gliders is a good pedagogy. As we learnt it from AA587 wrong practices were accepted from the community of pilots. We have to change now these false ideas built on very particular situations with bad solutions : Learjet dutch roll or communication between glider and trailer. Didactic is important. We know that in critical situation our brain is regressing to what we learn first. How we learn to fly is still coming out after thousands of hours. What you have well learnt in initial formation is for ever. Poor initial training is expensive and dangerous.It is important to give effect to accident reports like AA587 in pedagogy.
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Old 29th Sep 2013, 09:55
  #82 (permalink)  
 
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This has been an interesting and illuminating discussion, thanks!

Quote from tdracer:
I don't seem to recall anyone ever claiming that the 707 airframe wasn't robust.

When I did my base training with AA at DFW in 1975, I was surprised that no attempt was made to demonstrate dutch roll characteristics and recovery at altitude, even though the a/c was equipped with only one yaw damper. (BTW, I'm not suggesting that dutch roll recovery by the pilot would involve any use of rudder.) Four years earlier, my VC10 conversion had included several full demonstrations (up to about 40 degrees of bank) and recovery. The VC10 has(d) 3 independent rudders, each with a yaw damper.
One possible interpretation was that the a/c was not inclined to serious dutch roll at altitude - we all know that it would on the approach. On reflection, I'm wondering if the B707 airframe, specifically the vertical surfaces, may have been merely adequate for the regs? Has anyone got a copy of Davies to hand?

Quote from flarepilot:
that plane would still be flying if it had a rudder limiter based upon speed. at low speed full throw, at higher speeds less throw.

It has precisely that.

Clandestino,
Your posts are always well-informed, but could I respectfully suggest that you might resist the temptation to nit-pick the statements of those posters with whom you are broadly in agreement, and that you allow for the context in which they are made, and the audience? I'm sure you don't mean to sound arrogant..

Quote from Teldoserious:
Must be fun to get an Airbus type...

Indeed it is! The OP has made some unsupportable assertions (not all as cliched as the above), and in doing so has done us readers a favour by provoking the authoritative contributions of AirRabbit, Owain, and some others.
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Old 29th Sep 2013, 10:27
  #83 (permalink)  
 
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Re-upping my CFII was pretty funny...
Teldorserious, out of interest what A/C ratings do you hold or have held?

I gather you've never flown an Airbus, what about Boeing?
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Old 29th Sep 2013, 11:27
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He has no ratings what so ever. He has appeared under numerous identities over the years, and always wears his ignorance on his sleeve.
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Old 29th Sep 2013, 11:54
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john smith

just about every plane I can think of in the transport catagory has the admonishment that the pilots operating handbook assumes the pilot is an experienced and knowledgeable pilot and does not hand hold the novice.


shutting down the engines in cruise is generally recognized as contrary to maintaining altitude

scanning the instruments is generally recognized as a requirement for precise flying...

an experienced pilot knows that.


but what us experienced pilots didn't know was that using the rudder in a certain way WOULD CAUSE THE PLANE TO FALL APART.

I am of the generation that had it drilled into them BY THE FAA in its approved methods that structural failure wouldn't occur below certain speeds with full control throw.

(not unless their was previous damage to the plane)


In the modern cockpit there are some odd placcards...one I mentioned was about limiting control throw to HALF above 40,000'

many of us go to work every day in planes that have placcards saying you can't do a Catagory 2 ILS without proper training and operating equipment...now most of us still think that one is out of place...BUT ITS STILL THERE.

A placcard describes something unusual about the airplane, it is akin to the pilots operating handbook. Even a short paragraph in the airbus POH saying not to screw with the rudder would have done the trick

OF COURSE, who would buy an airplane that has a placcard or POH statement like: IF YOU SCREW WITH THE RUDDER THE PLANE WILL< REPEAT WILL< FALL APARt and KILL EVERYONE.

sorry john smith...if you knew the plane had this problem and you didn't tell all us other pilots, shame on you.

I just wish I had copies of all those books and tests I've used over the years with statements about what controls, what speeds, etc , all FAA approved.

DP Davies would have had something to say.

Oh, by the way...getting ''locked into " wake turbulence is something we train for...and it can be a bitch ...can't anyone conceive that the wake was bad enough to start a whole cycle of events that ended up showing the weakness of this plane?


I am reminded that there was a dissenting opinion from an NTSB member about the probable cause and the tail had previous , unknown or unreported damage.

makes one think

oh, and an A310 lost a piece of its rudder on a different flight...hmmmm

makes one think
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Old 29th Sep 2013, 12:52
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Originally Posted by flarepilot View Post

oh, and an A310 lost a piece of its rudder on a different flight...hmmmm

makes one think
I think that it is a separate issue. Losing a rudder is a lot different than losing the entire fin which happens to take the rudder with it.

The partial rudder thing was due to some sort of disbonding I believe.
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Old 29th Sep 2013, 13:07
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A placcard describes something unusual about the airplane
Maybe that's the reason there is no placard in transport airplanes explaining use of rudder?
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Old 29th Sep 2013, 13:23
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HN, exactly.
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Old 29th Sep 2013, 13:26
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Isn't it somewhat tiresome discussing stuff with two different SSG personae in one thread?
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Old 29th Sep 2013, 15:28
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Since the trolls(Brian and Denti) have jumped in, the thread derailed. I'm out.

If the Airbus can't take a rudder back and forth, so be it. You can believe that all planes are like this, completely nullifying what us pilots do every day in training, in x winds, in single engine ops, or day to day flying, stepping on the rudders all day long, back and forth, at all sorts of speeds. Still here.
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Old 29th Sep 2013, 15:35
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The sad part is some still havn't learned the lessons from this accident. Boeing has pages of text on what is, or isn't, acceptable rudder input.

"If you believe that all planes are like this" - we're talking about commercial jet aircraft. What a/c are you talking about? What commercial jet a/c can you swing the rudder back and forth, stop to stop, with no cause for concern?
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Old 29th Sep 2013, 15:53
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The lesson is that Airbus made a crappy tail that couldn't be inspected for fatigue, and it did fall apart under conditions that many of us have exceeded in other aircraft, by orders of magnitude, every day in turbulance, upset recoveries, and normal training regimens.
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Old 29th Sep 2013, 17:10
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I've got a technical question (this being the Tech Log forum) that I haven't seen addressed, even in the NTSB report.

What sequence of effects or factors led to AA587 then losing control and crashing after losing the vertical stabilizer?

Yeah, yeah. I know. "Duh! The tail fell off!" Except that aircraft (even large jets) have lost their vertical stabilizers without subsequently crashing: http://www.murdoconline.net/wordpres...52-no-vert.jpg

I'm figuring the probable effects were:

- abrupt shift to a nose-down cg with the loss of the stabilizer's weight from the tail.
- "snap yaw" in reaction to the loss of the rudder's yaw force in the opposite direction.

BTW - I don't mean to imply that the AA crew could have saved the aircraft. They had little altitude or time and were in an already confusing situation. The crew of the B-52 pictured were test pilots intentionally trying to identify structural weaknesses. So they were at a safe altitude, and expecting (more or less) something to break.
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Old 29th Sep 2013, 17:20
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AFAIR, according to tests after the AA587 accident the "crappy Airbus tail" did exceed the required and specified strength specifications by a considerable margin. A more valid point of Airbus-related criticism was the sensitive reaction of the rudder pedals, translating even very small pedal movements into considerable rudder deflections at higher speeds. And indeed there was apparently some widespread confusion regarding the limits represented by Va, including the FAA itself.* But all this has nothing to do with the tailfin strength or accessibility of the Airbus vertical stabilizer.

* Cited source: AA587: The Perils of Flying by the Book | Flying Magazine

@pattern: the B52 on the picture still has an (albeit small) remaining piece of vertical fin that stabilizes the airplane with regard to yawing movements. Without any fin and the resulting weathervaning tendency, AFAIK no airplane can be controlled in flight.

Last edited by Armchairflyer; 29th Sep 2013 at 17:29. Reason: Added reply
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Old 29th Sep 2013, 17:44
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@pattern

I'm not sure about this but I believe that the B52 didn't have any hydraulics in the vertical stabiliser - I'm sure someone here will correct me if I am wrong there.
When AA587 lost its fin it also lost all hydraulics since it was supplied by all three systems. Consequently there was no aerodynamic control of any sort available whereas, if I am right, the B52 at least had elevators and ailerons.
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Old 29th Sep 2013, 18:26
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What we have here is a failure to communicate

DEAR JOHN SMITH...

I see the problem...you don't understand that thousands of properly certificated FAA approved pilots did NOT KNOW THAT STOMPING ON THE RUDDER would cause the plane to fall apart.

thousands of us learned that if you were at or below Va and applied full control movement the plane would not fall apart.

it was on countless examinations and in FAA literature of the time.

Even while flying other planes, that had rudder LIMITATIONS and rudder limiters WE (PILOTS) were required by the FAA and OUR AIRLINES to memorize and display knowledge of limits imposed by design of the plane we were flying.

I can still explain how the rudder limiter system works on douglas systems and boeing systems and that if the limiter system fails we have to KNOW NOT TO USE TOO MUCH RUDDER ABOVE CERTAIN SPEEDS.


What the properly certified airline, training program, and pilots who were involved in the A300 inflight breakup DIDN'T know then is what you claim to have known all along.

Hence my advice about a placcard or a POH write up.


I'm glad you know...but I didn't and a whole airline didn't and the FAA didn't know.

But you knew.

yeah, right.

now we know...and maybe that's why the airbus is so junior at some airlines.

Last edited by flarepilot; 29th Sep 2013 at 18:26.
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Old 29th Sep 2013, 19:41
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Here is a cut and paste out of a Boeing 777 AFM:

F L I G H T C O N T R O L S

Avoid rapid and large alternating control inputs, especially in
combination with large changes in pitch, roll, or yaw (e.g. large
side slip angles) as they may result in structural failure at any
speed, including below VA.
I'm pretty sure all Boeing AFMs have that same statement. It didn't use to be there - it's addition was in direct response to the A300 AA587 crash.

Do you really need a placard to remind pilots not to do something that the AFM tells them not to do?
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Old 29th Sep 2013, 19:54
  #98 (permalink)  
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I agree with everything Flare said.

You see some of us teach this stuff, some of us have been getting ratings, some of us have been getting types, some of have been going to school every year and some of us have had to teach and regurgitate the definition of Va now for some time.

It's absolutely full out of deception for peeps in here to say after the fact, after the crash, after the FAA redefines Va, to say ..

'Yeah, well, you know, when WE flew, we never thought that Va, full scale deflection and all that meant anything...because you know...we didn't trust the test pilots, or the manufacturers to give us a speed that we could trust to hit a top, come out upside down, do a recovery any which way...because you know...WE knew all along that three pedal imputs in an Airbus would take the tail off.'

Meanwhile, the rest of us are pounding on the rudders for single engine work, side slips, x winds, upsets, stall recoveries, sometimes bad spin recoveries...and yes in twins, tprops and jets, because you know, pilots should know this stuff..and believe it or not they do upsets, stalls, and recoveries in airlines...right? Or do all you guys just get a little beep and push the nose over and call it good.

Either flare and I are getting putt on by a bunch of kids in here or the airline guys are just following what they are told.

This year Va is x, next year y. This year CRM is great, next year crap.

Maybe because its on me to pull the levers back when things get bumpy I have to know this stuff.
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Old 29th Sep 2013, 20:20
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whether or not those who are doing it as in at work at the front end heed these savvy words
from the coal face and inputs Teld, please keep it up. you have a large readership and no mistake

BTW how come that chinese 747 that stalled and only recovered feet from the briney off NW america all those years ago not serve as an example to all plane makers in getting it right on the drawing board and making them Boeing tough?

Last edited by Fantome; 29th Sep 2013 at 20:26.
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Old 29th Sep 2013, 20:25
  #100 (permalink)  
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Teldoserious

I think some of us airline guys are merely trying to say that large rudder inputs, other than for assymetric yaw conditions, are pretty much unheard of. Possibly in an "upset" condition if it helps to pick up a wing and/or prevent further yaw. I'm not an expert but I've never heard it suggested as an appropriate response. In a vortex encounter I'd expect to use aileron primarily.

Light aircraft may need an appropriate rudder input and I've spent a fair amount of time teaching "co-ordinated" controls. If you're teaching in an aircraft with barn door ailerons that are prone to aileron drag then it's essential. Perhaps that is where your confusion is arising?

tdracer

I suspect all the Boeing FCOMs were amended after the AA crash.
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