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Guest Blue Skyy

American Airlines Flight 587

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For those of you who don't recognize the meaning of the subject line, here is a brief description: About two months after 9/11 an Airbus 300 (I think it was a 300) crashed after take-off in New York. The NTSB's primary focus was wake turbulence and Airbus's composite tail.I watched a discovery channel documentery about this. My question isn't about what exactly caused the crash though. My question has to do with procedures when encountering wake turbulence. So, I don't want to see negative posts about Airbus or AAL or the pilots of the plane. Create a seperate post if all you want to do is bash others. Thanks.So, what are the procedures that a pilot should go through when encountering wake turbulence in an airliner? On the discovery channel they said that AAL pilots were trained to use rudder and aileron to recover from WT (wake turbulence) upsets. Here is were I am confused. Example: Your flying along and all of a sudden you encounter WT, you then find yourself at a 40 degree bank angle. AAL pilots were trained to use both aileron & rudder to bring the plane back to wings level. But, my first reaction would be to use only aileron to bring the plane to a more acceptable (for the pax) bank angle. Why use rudder at all? If the upset is a high angle of bank, I would always ues aileron, never rudder. Now, I'm not an airline pilot, so forgive my nieveness. Also, sometime after the crash it was shown that rudder reversals should never be done on airliners, whether is was a aluminum tail or composite, it shouldn't be done. I was a little taken back by this. Does this hold true for the other control surfaces, such as elevators. I would think that if needed a pilot could be very aggressive with the controls and that the plane should be built to withstand it. I would very much appreciate any information an experienced pilot would have. Thanks in advance.

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First let me commend you for such an insightful post. I'm not an airline pilot, but I hold a private pilot certificate. Your points had me dig out the Airmens Information Pilot to confirm my training. As you may already know, the number one way to deal with WT is to avoid it. The AIM states, "The wake of larger aircraft requires the respect of all pilots." AIM 7-3-3 (b.3) Your reasoning makes intuitive sense. Again, from the AIM: "In rate instances a wake encounter could cause inflight structural damage of catastrophic proportions. However, the usual hazard is associated with induced rolling moments which can exceed the roll-control authority of the encountering aircraft." So using ailerons alone may be what one initially wants to do, but the WT may have rolled your airliner beyond its capacity to recover just using ailerons. To further support using ailerons vs rudder, this is from an article published in AOPA Magazine, Mar 02, titled "An Awakening How wake turbulence sucked me in

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Good post :) When Flight 587 crashed I was shocked ..... my favorite aircraft (American A300-600R) had crashed, and it was packed with people :(I'm not a pilot, but I would avoid using the rudder in such a situation. The rudder would introduce yaw to an already critical situation, which IMHO isn't very desireable.This is in no way a criticism of the flight crew of AAL587 .... :)

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* BUMP *I was afraid that such an interesting topic would be lost in the busy forum.Theory: When your at an extreme angle of bank (for an airliner), say 40 degrees left bank, using a lot of right rudder (with aileron too) would bring the nose up as you try to bring the wings level. Perhaps this is why they were taught to use rudder. It would, hopefully, take the plane away from the WT vortex. Also noted in this documentary was that on the ground in order to fully deflect the rudder, 5 inches of travel is needed on the pedals. However, in the air only 1.5 inches are needed. That would seem awfully sensitive, but maybe I heard wrong. Any airline pilots out there.....? :)

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Nice topic! I saw this documentary on the Discovery channel the other day as well and quite enjoyed it. It was interesting to see both sides (AA & Airbus) go at it, trying to place the blame on one another. Both had logical arguments, but in the end Airbus ended up being correct, stating that the pilot should not have acted as he did. I think he did a total of 5 successive full rudder deflections in opposite directions, which far exceeded the maximum forces the tail was built to withstand. OTOH, AA claimed they had no knowledge that this could not be done on a modern airliner, as did other airlines :-eek Quite scary, if you think about it. -Max Cowgill

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I just hope god brought them home to their destination.................

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I am not an AT pilot, but I did complete the Commercial Instrument Ground and Flight training. I believe that the use of rudder in this case, in addition to aileron, would be to recover from what is called a Dutch Roll. Heavy aircraft rolling out of a steep bank at just above maneuvering speed are susceptible to this phenomenon. Uninduced yaw and roll from side to side is encountered and the only way to counteract it is to use opposite rudder as opposed to ailerons. When the yaw is right the roll is left and then it switches. Right bank and left rudder and then left bank and right rudder, in the opposite direction of the Dutch Roll, straightens it out pretty quick. This is a required flight coordination maneuver for commercial pilots. You try to keep the nose on one point on the horizon while changing inputs from left rudder, right aileron, to right rudder left aileron and back, over and over again.Also, when you reach a bank of, say 40*, you can't prevent a heading change. Heavy pilots quite often use rudder to maintain heading instead of bank on final. The best way to avoid WT is to stay high, (WT settles downward with time) maintain a relatively high power setting and use spoilers to compensate. This gives you the ability to stop or slow your descent a lot easier if needed. And try to touch down beyond the point at which the aircraft creating the WT applied full power. A lot of the WT is from the engines but most is from the wing tips while still in ground effect.I'll probably get all kinds of arguments on these points, but that is what you learn in Comm flight school.Hope this helps some.Glenn

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I'm not an airlien pilot either, but I am a private pilot and currently for C172'd.Thr rudder on the 172 has the most authority of any control surface. This is important if you're slow as you're looking for soem control authority. Also, if slow and at a high angle of attack, aelerons exhibit inverse yaw which is what you don't want. As strange as it may seem, the last thing you want to use near the stalling speed is aelerons.I'm not sure how these rules translate to a heavy jet though.Bruce.

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<>It has nothing to do with heavy aircraft. Dutch roll comes into play with swept-wing aircraft and span-wise airflow. You may be talking about "adverse yaw" in which the raised wing in a bank creates more drag, yawing the aircraft in the opposite direction of the turn, which is why rudder is required when entering turns to keep the aircraft coordinated.Your method of damping out dutch roll seems to be correct.<>None of the wake turbulance is due to the engines. Wake turbulance is due to lift being generated from the wings. Wake turbulance is at it's greatest in heavy, clean, aircraft at high angles of attack (i.e. after takeoff). The 757 is the biggest generator of wake turbulance of all the aircraft to my knowledge (including the large Boeing and Airbus aircraft).<>True, stay above the aircraft's glide path.<>?? You should touch down before the preceeding aircrafts' nose comes off the runway (on takeoff), and after it settles down (on landing).<>It's not what I learned...skyy

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