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as what i read from books, on thrust-velocity and power-velocity curves for a piston-prop airplane

  1. V max excess power= Vmd

  2. V max excess thrust= Vmp

these two values are just so clicking, and i couldn't figure out what's the physics behind it.

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Power in aviation physics is Thrust × Velocity. The best combination of these two is V max excess power, meaning (because of the drag curve) that no other speed will give a better rate of climb.

V max excess thrust is a slower speed because prop efficiency curve (thrust curve) declines with airspeed. By slowing down, the greatest difference in thrust to drag is achieved (even though drag is slightly greater). This allows the plane to climb at a higher angle, albeit at a slower speed.

V max excess thrust is also referred to as Vx, and V max excess power is Vy.

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  • $\begingroup$ thanks for the answer! i entirely agree with what you said. but sorry for i didn't declare my question clearly lately, what i really wanna ask is why at a speed where an aircraft gets minimum drag gets maximun excess power, and vice versa. $\endgroup$
    – master olof
    Sep 4, 2022 at 6:33
  • $\begingroup$ @masterolof remember, "power" is Thrust × Velocity. At minimum drag plane uses least amount of thrust to counteract drag from lift, leaving all "excess" thrust to do things like climb. $\endgroup$
    – Robert DiGiovanni
    Sep 4, 2022 at 16:07

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