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Lateral control

 
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eagle8



Joined: 22 Sep 2012
Posts: 1

PostPosted: Mon Sep 24, 2012 4:40 am    Post subject: Lateral control Reply with quote

Years ago (I retired in 1991) I noticed that just about every crosswind takeoff I observed resulted in the airplane rolling down wind at liftoff. Pilots will hold aileron into the wind to keep the wings level, so why the roll down wind at liftoff? I believe that the rolling moment at liftoff is as a result in decreasing lateral control effectiveness as AOA is increasing during rotation. In my own flying I always increased control throw into the crosswind as I rotated. And since directional control during the takeoff roll was with the rudder, the result was that the airlplane would be in a cross-controlled slip after liftoff. Centering all affected controls then produced normal flight.
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K.Haroon
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Joined: 11 Dec 2005
Posts: 1305

PostPosted: Mon Sep 24, 2012 8:57 pm    Post subject: Reply with quote

What the Boeing says:

Begin the takeoff roll with the control wheel approximately centered. Throughout the takeoff roll, gradually increase control wheel displacement into the wind only enough to maintain approximately wings level.

Note: Excessive control wheel displacement during rotation and liftoff increases spoiler deployment. As spoiler deployment increases, drag increases and lift is reduced which results in reduced tail clearance, a longer takeoff roll, and slower airplane acceleration.

At liftoff, the airplane is in a sideslip with crossed controls. A slow, smooth recovery from this sideslip is accomplished by slowly neutralizing the control wheel and rudder pedals after liftoff.
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Nabeel Javed



Joined: 15 Nov 2015
Posts: 1

PostPosted: Mon Nov 16, 2015 2:22 am    Post subject: Lateral control Reply with quote

I can't recall anything from aerodynamics which says increasing AOA reduces control effectiveness.
I think roll towards downwind side is due to loss of landing gear traction at lift off which was providing some resistance to yaw induced roll during takeoff roll, but as soon as you break off the ground that resistance is finished and applied rudder causes roll.

Basic principal of Aerodynamic:

"Roll causes yaw" & "Yaw causes roll"

Wink
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