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Originally Posted by surreal1221  Thanks gents. Now does Vx or Vy vary depending on weight? |
Yes, both will vary.
They both depend on minimizing drag and having lots of thrust or power. Obviously, thrust or power will not vary with weight, but they *do* vary with airspeed, and so does the drag on the airplane.
Your point of minimum drag will occur at a particular AOA for any given weight. Vx is set at max gross and occurs at a particular AOA. If you are not quite as heavy, then your AOA
at that airspeed will be lower than optimal, because AOA and airspeed combined have to produce lift=weight. With less weight, you need less lift and if you hold airspeed constant, your AOA must be less. Got that?
So if you increase your AOA to least drag, your airspeed will be lower than what it would be at max gross.
I can't tell you how much less though. Since Vx and Vy also depend on available thrust and power, the changes in airspeeds don't quite follow the rules that stall speed or best glide do.