Both the OAA textbook and video say that Vy is the same speed as Vmd for a propeller driven aircraft.
They illustrate that Vy is found by drawing a vertical line down to the axis of TAS from the tangent of a line drawn from the origin of the axes of Power and TAS to the curve of Power Required.
They also illustrate the same procedure for finding the Vmd and repeatedly state in the book and video that they are the same speed.
As far as I understand it, Vy is found at max. excess power which is not solely dependent on power required but also dependent on power available and the maximum difference between the two (i.e. the point of maximum distance between the two curves)
To complicate matters further, my instructor says that Vx is at Vmd! [Pretty sure this is wrong or at least the wrong way of looking at it as Vx is merely the speed for max. excess thrust as far as I understand]
The OAA book also states categorically that the IAS for Vx does not increase with altitude yet this is contradicted by many, including my instructor.
Who is right in all of this? - I don't want to screw up in the exams for misinformation!
