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NTSB Recommendation re Airbus Rudder Travel Limits

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NTSB Recommendation re Airbus Rudder Travel Limits

Old 6th Aug 2010, 19:53
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PJ2
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NTSB Recommendation re Airbus Rudder Travel Limits

NTSB Recommendation A-10-119/120, August 04, 2010

Reference: American Airlines 587, Air Canada 190 accidents
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Old 6th Aug 2010, 21:10
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It's amazing that a seemingly seasoned crew would introduce major rudder deflections in a jet airplane with 3000psi hydraulics and triple PCUs. To do this at 36000 feet is asking for certain death. Feet belong on the floor, point blank period. When aileron is exhausted and the airplane continues to roll, it may be appropriate but the first instict should be aileron and reducing AOA.
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Old 6th Aug 2010, 21:21
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PJ2

It would appear that EASA and the NTSB are both in agreement regarding the retro fitting of a PTLU to the aircraft mentioned. So, I am a little surprised that the NTSB needs to reiterate its position on the matter to EASA.

The following from the NTSB letter [bolding & emphasis is mine]-
On March 19, 2010, EASA further indicated that “its previously held position on the pilot training out as being an efficient and sufficient measure to avoid any new hazardous situations has to be reconsidered following more recent service experience which confirms that crew use of rudder pedal inputs in upset encounters cannot betrained out.’” EASA therefore indicated that it plans to require the PTLU on Airbus A310 and A300-600 aircraft models.
Possibly the NTSB are hoping that EASA will be prompted into issuing an AD forthwith.

mm43
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Old 6th Aug 2010, 21:26
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In the American Airlines flight 587 accident, the pilot applied four full alternating rudder inputs; after the fourth input, the aerodynamic loads on the vertical stabilizer exceeded the vertical stabilizer’s ultimate design load (at about twice the maximum load), and it separated from the airplane. In the Air Canada flight 190 accident, the pilot applied three alternating rudder inputs and exceeded the limit load by 29 percent.
What sort of idiots are they training over there? Or perhaps that should be 'what sort of idiotic training is being given over there'?

This NTSB recommendation is utter rubbish. Teach your pilots to fly correctly!
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Old 6th Aug 2010, 23:05
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what amazes me is that a plane that can destroy itself in flight wouldn't have rudder limiters to protect its structure. the jets I've flown either had a placcard saying : no full control throw above blank altitude.

or a gadget that prevented you from doing too much.
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Old 6th Aug 2010, 23:28
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BEagle, we are not trained to fly like that over here. AA conducted advanced maneuvering training at high angles of attack to use rudder to assist in recovery but not in a 250 knot climb out of JFK. The A300 had such severe yaw both engines snapped off along with the vertical stabilizer. The vertical stab on that particular aircraft had delamination where it separated coming out of the factory. It was patched with a brace right where it broke off. We know severe yaw was involved which could be from irratic rudder inputs or the vertical stab leading edge separating causing the yaw. Would you let your FO use that kind of rudder control because of wake turbulence?
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Old 7th Aug 2010, 00:49
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Correct me if I'm wrong, but there was no data in the American crash showing rudder pedal input - only rudder deflection. And the yaw damper had been written up prior to that flight. And the pilots are dead, thus unable to explain what happened.
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Old 7th Aug 2010, 01:26
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I agree, the chance that both pilots would allow those reported rudder reversals to snap the vertical stab is not possible. It made it a lot cheaper for Airbus blaming it on the dead copilot though. Any flight attendant standing in the back would probably have been killed before the breakup with the lateral g forces. I wish they had data on actual rudder pedal movement, not just rudder displacement. The FDR also averaged movement of the rudder so left a lot to be desired for real time info.
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Old 7th Aug 2010, 01:30
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Originally Posted by Huck
Correct me if I'm wrong, but there was no data in the American crash showing rudder pedal input - only rudder deflection.
All the control inputs were recorded.

http://www.ntsb.gov/events/2001/aa58...path_web01.wmv
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Old 7th Aug 2010, 01:35
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Those aren't inputs - they're control displacements.

The YD moves the rudder pedals too.
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Old 7th Aug 2010, 02:45
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Not to disrespect those who have departed, but watch that .wmv clip. The FO in clearly overcontrols through the first and second wake encounters. Extrordinarily aggressive IMO. The rudder and aileron are moving in the same direction which is probably a result of deliberate manual input. The training program was flawed, and this was probably a pilot who got too excited in a heavy airplane at 250 knots with plenty of roll authority to counteract a wake encounter. Interesting to note all of his previous experience prior to joining AA was in aircraft with unboosted controls.
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Old 7th Aug 2010, 03:39
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F/O had previous record of stroking rudders . . .

The October 2002 NTSB hearing heard evidence from one American Airlines Captain John Lavelle, who had flown a number of times with F/O Stan Molin on the B727 in 1997-1998. He recalled that F/O Molin had aggressively used rudder in an oscillatory mode on a B727 to attempt to control roll. This action didn't level the wings, but it did create sideloads due to yaw. They discussed this during the flight. Captain Lavelle recalled that Molin had told him that he was following American Airlines training procedures. The NTSB concluded that the PF [F/O Sten Molin] tended to react to wake turbulence using excessive control inputs, and that his control inputs in this case were too aggressive and the degree of his initial rudder pedal activation was unnecessary to control the aircraft.
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Old 7th Aug 2010, 07:29
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Huck....

your quote:

"The YD moves the rudder pedals too."

That must be an AB thing, since that's not the case in the 737NG!

Cheers..
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Old 7th Aug 2010, 09:59
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Huck,

Your statement about the yaw damper is incorrect.

The rudder trim moves the pedals so you can see the level of displacement. If the yaw damper was to move the pedals, you would be getting tiny vibrations during flight.

That goes for A320 and B737 series anyway. The system set-up shouldn't be any different for other types.
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Old 7th Aug 2010, 10:39
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p51 guy is right...if you over control, your flight attendants go flying, your passengers get sick and even YOu can get sick or the other pilot anyway.
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Old 7th Aug 2010, 11:07
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Where does AF 447 fit into this????????????
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Old 7th Aug 2010, 12:15
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You guys are right, I read it wrong. From the report:

The yaw autopilot actuator(emphasis mine), which produces yaw autopilot commands,42 is a single
unit that houses two electrohydraulic actuators, each of which is controlled by a flight
control computer. The yaw autopilot actuator has an output lever that is connected
through a torque limiter to the main bellcrank. The torque limiter allows a pilot to
override an autopilot output as long as the pilot applies about 143 pounds more than the
rudder pedal feel forces. Yaw autopilot commands are limited by software in the flight
control computers to a maximum of 34º of rudder per second. The yaw autopilot actuator
and the rudder pedals are rigidly linked, so a yaw autopilot input (through the main
bellcrank) results in pedal motion.
I know I'm in the minority here. But watch that video of the control movements again, keeping an eye on the artificial horizon. Look at the size of the control deflections. Tell me that there was nothing going on besides a wake encounter.....
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Old 7th Aug 2010, 13:00
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The present design is an ergonomic trap.

The ratio between breakout force and full deflection at high speeds makes rudder next to impossible to modulate.
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Old 7th Aug 2010, 13:22
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Sorry, I meant yaw control from the A/P, not the YD....

Watch the artificial horizon, combined with the size of the control movements. About 19:15:53.

I doubt I've ever moved a yoke like that at 250 knots. Sure, maybe he was just a really really bad pilot. But maybe something was happening to that vertical stabilizer - something that doesn't show on the FDR.
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Old 7th Aug 2010, 16:21
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Narrow reading of procedures

Like any turbulance,you need to "ride it out" in wake turbulance and steady gentle inputs are the norm.
Quite often low experince pilots will quote "procedures"chapter and verse...without a clear idea as to where and how to apply them.
Another factor is that this event occured just after 911...maybe in this context wanting to "stay in control come what may" might have been a possible mind set.
Pure conjecture.....but just a thought about all the possible factors which could have played a role.
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