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Old 27th Aug 2018, 15:03
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Time Traveller
 
Join Date: Jun 2007
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.on the T/0 roll use as little or no, into wind aileron. The more control deflection, the more drag of course.
I know this is as per the Boeing fctm, but I really find it poor theory and poor practice.(I agree with everything else you say though).

Spoilers work by spoiling lift, not creating drag (the form/profile drag of spoilers at takeoff speed is naff-all.) During the takeoff roll, you're not creating lift so the only extra drag is the tiny frontal area of one roll spoiler and deflected ailerons.

The cross wind limit of the 737 is pretty high, and in anything near those conditions, anyone who applies just 1 unit is going to have the wing lifting dramatically, and they'll be squirreling all over the runway. But they do it because the manual says so.

My TriStar instructor taught me to hold in full aileron in any significant crosswind, including during the rotation. It works, although I do limit its use during the rotation, because then you are spoiling lift, and that increases risk of tailstrike.... That said, the guidance of "enough aileron to keep the wings level" is kinda meaningless, because with a weedy input, they rotate, the wheels leave the ground and "bam" - the upwind wing lifts and you've got a sudden 20 degrees of bank. So that's a balance.

But extra drag during the roll ... No, not in any significant way.

Last edited by Time Traveller; 27th Aug 2018 at 15:47.
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