Originally Posted by Pace
Now about best angle of climb airspeed. This angle can also be viewed as how much altitude is gained per foot/mile/etc. of forward travel. Obviously, at a slower airspeed you cover less ground, so at the same vertical rate the angle would steepen. But we've already shown that there is only one speed at which you get the max rate of climb. However, recall that squared relationship between speed and drag -- it also works in reverse, so that drag decreases with the square of the speed reduction.
This means that at a slightly slower speed than Vy, the angle becomes a little steeper. So the manufacturers test and calculate until they find the optimum relationship between speed reduction and drag reduction that results in the airspeed that gives you the best (steepest) angle of climb (Vx), which is good for clearing obstacles. Just as Vy decreases with altitude, Vx increases with altitude.
Drag will be reduced with as a square of airspeed, but so will Lift meaning the angle of attack will have to increase to compensate which will mean the same IAS - unless I am very mistaken!
Last edited by baleares; 27th Feb 2014 at 07:25.