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-   -   He stepped on the Rudder and redefined Va (https://www.pprune.org/tech-log/524238-he-stepped-rudder-redefined-va.html)

Teldorserious 24th Sep 2013 20:04

He stepped on the Rudder and redefined Va
 
Just curious if anyone else has noticed the FAAs recalibration of what Va is after the Airbus rudder deal?

Re-upping my CFII was pretty funny...maybe it's old news now, but I was reminded that Va stress limits can be exceeded under Va, you know, if you step on the pedal too hard in an Airbus, right after departure, going slow...

Always cracks me up. Just have to wonder how much Airbus bought off the FAA to get us all to swallow this.

Tinstaafl 24th Sep 2013 20:36

I thought certification required a single application of the control input. Didn't the separation of the fin from the fuselage involve a couplet or two, and not a single application?

flyboyike 24th Sep 2013 20:49

I was pretty sure the speed in question was Va (maneuvering speed) and not Vmo.

Teldorserious 24th Sep 2013 22:12

You were right, corrected that...I think you guys knew what I meant.

flarepilot 24th Sep 2013 22:25

teledorserious


IT IS CRAP. How many written exams did I pass in my aviation life? 10 or more...none of them including flight engineer and ATP said: will wiggling the rudder hard cause the plane to come apart?

NONE.

They all warned that a placcard had to be obeyed...and I've seen placcards like: do not use more than half control throw above 40,000' or something similar.

TELED...the FAA basically changed the rules after more than 30 years and not one other plane had the problems the b'us had/has.

Pugilistic Animus 24th Sep 2013 23:08

"wigling the rudder hard" is not something airplanes tolerate well, even at or below Va

misd-agin 25th Sep 2013 00:00


I thought certification required a single application of the control input. Didn't the separation of the fin from the fuselage involve a couplet or two, and not a single application?
It was three or four.

bubbers44 25th Sep 2013 00:50

The AA A300 crash was blamed on the FO reversing rudder movements and the VS separated. I doubt if that was the cause but like TWA800 that was the official cause according to the NTSB. TWA800 was covered up and may be reopened because of the documentary of FBI manipulation of evidence recently. Wouldn't it be nice if we could trust our own government?

tdracer 25th Sep 2013 03:12

Listen, I'm not exactly in the habit of defending Brand A, but.....
In the aftermath of the A300 vertical tail failure, Boeing evaluated what would happen with similar oscillatory rudder inputs on various Boeing airplanes. The results were not pretty :eek:

Boeing AFMs have subsequently been updated with words saying, euphemistically:
DON'T DO THAT!

So, unless you like potentially structurally failing the vertical tail and killing everyone on-board,
DON'T DO THAT!

bubbers44 25th Sep 2013 03:49

I don't think the FO did that because the captain would have stopped him if he did. Would any captain let his FO do this? I wouldn't. We had an A300 have out of control rudder movements landing at MIA and both pilots felt they were going to crash prior to this event. They went around and regained control. The FA's in the back would be beat up by the rudder movements.

NTSB has political pressure to blame the pilots, not the manufacturer, so blame goes to the low money people.. That is my opinion.

My friend by the way was the FO in the MIA incident.

de facto 25th Sep 2013 04:46


I thought certification required a single application of the control input. Didn't the separation of the fin from the fuselage involve a couplet or two, and not a single application?
Correct,a single full rudder application up to VMO/MMO still has a 50 % safety load on it but where it hurts is reversal of input...ie full left followed by full right.

On the 737,at speed above 137 kts,rudder pressure is limited by 25 %.

Semaphore Sam 25th Sep 2013 05:28

Was there not some discussion about an American Airlines procedure that used rudder input to aid roll control during turbulence? Is it not also true that this procedure was cancelled after this accident? So, it seems, the F/O might have been following AA turbulence SOP. Sam

misd-agin 25th Sep 2013 13:01


Was there not some discussion about an American Airlines procedure that used rudder input to aid roll control during turbulence? Is it not also true that this procedure was cancelled after this accident? So, it seems, the F/O might have been following AA turbulence SOP. Sam

Training had nothing to do with turbulence.
Cancelled after the accident.
Was not following SOP.

de facto 25th Sep 2013 14:49


Was not following SOP.
Would you be so kind and elaborate on that please?

SMT Member 25th Sep 2013 15:27

If memory serves me right, AA had during their upset recovery training placed an emphasis on the use of rudder. From the same fading memory banks, the FO had a habit of being 'ham fisted' (in lack of a better word) in his rudder handling. Combine the two with 3 or 4 full rudder reversals, as evidenced by the FDR and supposedly induced as a reaction to wake turbulence from a preceding heavy, and you have a plausible explanation why the VS failed.

Other scenarios are possible, but are unlikely to survive an encounter with Occam's Razor.

As for the idea of the skipper stopping it .... with feet on floor, and 3 rapid rudder movements which his sensory system is likely to have overwhelmingly felt rather than seen, I think it would require reaction times far in excess of what is humanly possible.

flarepilot 25th Sep 2013 18:33

a skipper doesn't keep his feet flat on the floor if the plane is being thrashed around..
he may not put his feet directly upon the pedals or hands near the yoke/stick, but they are near

that's how you stay alive for years.


some pilots, myself included, think the problem was not in the pilots/copilots feet.

the four jet transports I've flown either had a rudder limiter or a placcard about control use. 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.


and if you call a captain "skipper" he might call you gilligan.

Pugilistic Animus 25th Sep 2013 18:46

even with rudder ratio limiting...no airplane in existance will tolerate such oscillation ...at Va let alone. at Vmo

roulishollandais 25th Sep 2013 20:46


Originally Posted by bubbers44
We had an A300 have out of control rudder movements landing at MIA and both pilots felt they were going to crash prior to this event

Had they a yaw damper failure?:zzz:
roulishollandais

roulishollandais 25th Sep 2013 20:56


Originally Posted by Teldorserious
He stepped on the Rudder and redefined Va

Just curious if anyone else has noticed the FAAs recalibration of what Va is after the Airbus rudder deal?

May I ask you both definitions and ref? Thanks
rh

bubbers44 25th Sep 2013 22:33

As I recall it was a yaw damper problem. I had two yaw damper oscillating rudder situations in the B727. One was corrected by turning off the yaw damper showing rudder actuation, the next, that didn't work, so turned off the one that wasn't.


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