There's another issue, let me introduce you to what is known to a select few as the "Venton Walters Equation".
For a particularly flexible wing, washout increases dramatically with loading, leading to the relationship:-
Vs = Vs(MTOW,1g).(((W/MTOW)Nz)^CAe)
Where CAe is the aeroelastic constant for the wing, equal to 0.5 for a perfectly rigid wing, but I've seen values as high as 0.82 for some (perfectly safe) microlights, which in some cases moves Va above Vne, creating a mild headache for the certification engineer, and severe migrane for many classical aerodynamicists.
The formula was first proposed by Roy Venton Walters, who designed the Puma and Raven microlight wings about 15 years ago, and despite a rather superficial proof on his part at the time, surprisingly works incredibly well for highly aeroelastic wings that tend to offload lift with loading (generally through increased washout).
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Last edited by Genghis the Engineer; 27th Aug 2002 at 22:59.