yak52
Joined: 25 Oct 2007
Posts: 50
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 Posted: Fri Jun 26, 2009 9:20 am Post subject: Heavy wing |
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For your consideration as there are many reasons for a heavy wing:
The solution to keeping the wing balanced at all airspeeds is to have the weight of the aircraft balanced from side to side and to make sure both wings gain and lose lift in exactly the same way as airspeed changes; that actually takes a little effort. Following are some possible causes of airspeed-dependent lift imbalance.
1) Aileron hinge-line gaps. If air can go through the aileron hinge lines, it will. That represents a loss of lift, and the leakage is an often unpredictable function of airspeed, angle of attack, "G" loading, and aileron-control deflection or trim. That means the leakage is seldom balanced from side to side. The leakage often gets worse at high angles of attack, such as in a climb. The airplane will turn to that side.
2) Imperfect airfoils. Tiny differences in airfoil shape from side to side (especially the rounding of the LEs) can require that the ailerons be trimmed to counteract. The aileron deflection and airfoil shape will have different airspeed characteristics, so the trim will be upset as the airspeed changes.
3) Wing warps, even subtle ones, will require the ailerons to be trimmed to counteract, and these two also vary with airspeed. The warp usually maintains its influence at very low airspeeds better than the aileron deflection.
4) If the ailerons are trimmed to one side to counteract a problem caused by the rudder trim not being centered (or a crooked fin!), the balance between these control surfaces will change with airspeed. We call this condition an aileron vs. rudder cross-trim
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