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A320 Spoilers

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Just returned to UK via Phoenix from Las Vegas. Flew in America West A320 and had good view of the rear of the wing on take off and noticed something I've never seen before - as the aircraft accelerated the spoilers along the wing surface extended and stayed up for about half the length of the take off run before settling back. Thought it might be something to do with killing lift when taking off with a slight crosswind - anyone any ideas?KD

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KD, I believe you're right. On the takeoff roll,the airbus computers automatically use spoilers to keep the plane steady. If I'm wrong please correct but that's what I've been lead to believe.Pretty clever eh?RegardsJohn Mc AvinueEINN/BAV 855Senior captain-600HRShttp://www.bavirtual.co.ukP 2.53 GHZ512 RAMWINXPGFORCE 4 128MB Ti4600

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You might also notice that the Ailerons deflect down when the flaps are extended and fair to nuetral once retracted. Like a Flap that extends all the way to the wing tip. Wonderful thing, Fly By Wire tehnology.Paul:-cool

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In a lot of modern jets, spoilers are used to augment roll control at lower airspeeds. The ailerons are designed to be effective at higher speeds and don't have quite enough authority at lower speeds, so asymetric spoiler deployment is used to enhance the plane's roll rate.In a crosswind takeoff the pilot will hold the ailerons into the wind to counter the crosswind. This keeps weight on the upwind wheels and helps offset the lateral forces of the crosswind. In a stiff crosswind, pilots will normally start the takeoff roll with full aileron deflection and gradually return the controls to center as the wings begin to generate lift.

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However, it must be noted that the input of into-wind aileron is NOT a recommended technique on the airbus for take-off, unlike other aircraft (Boeing). Airbus recommends neutral roll input for the take-off.Kevin in CYOW

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Thanks everyone for you replies - During the take off I must admit to being a little concerned!!Kevin in CYOW, if Airbus recommend neutral roll input how does the aircraft systems know to deploy the spoiler on the into wind wing?KD

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KD,I am not type-rated on the bus so I cannot give a technical answer; (airbusguy and others are welcome to chime in) however, I do have access to some of the airbus training material. The training manual in the take-off notes section says " Routine use of into wind aileron is not recommended unless encountering strong crosswinds. Even then, small amounts of lateral control may be used to maintain the wings level keeping in mind that excessive amounts may result in spoiler deployment increasing the tendency to turn into wind." It goes on to say "If some lateral control has been applied on the ground, the stick should be centralized during rotation so that the aircraft gets airborne with a zero roll rate demand."Under the cross-wind take-off section is states:"The routine use of large lateral inputs in crosswinds should be avoided, as it will lead to spoiler deployment, resulting in the following adverse effects:increased tendency to weathercockreduced lift and increased dragIn strong crosswind conditions, small amounts of lateral control may be used to maintain winds level. The width of the "Iron Cross" on the PFD is the maximum recommended crosswind input."All that to say, maybe there was a strong crosswind on the day you saw the take-off or well, pilots are just human, and maybe the guys (or gals) upfront had put more sidestick input in than they should have.Kevin in CYOW

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Kevin in CYOW,Thanks for the very comprehensive explanation - yes it was a windy day and we took off across the 2 main runways in use at McCarran.KD

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