PPRuNe Forums - View Single Post - Lift versus drag conversation
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Old 2nd November 2000 | 23:36
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Cuban_8
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Dabhand,

You seem to be somewhat confused with regards to your theory. In a power-off forced landing situation, i would suggest that Vmd is NOT what you are looking for!

For the greatest range over the ground during such a glide, any aircraft must fly at a speed which gives the best lift/drag ratio - a value for which is suggested by the manufacturer. In terms of remaining in the air for the longest period, then the aircraft must fly at a speed that gives Cl^1.5/Cd maximum.

Your argument is even more incorrect considering that when flying at maximum endurance configuration, Cd=4Cdo, whereas for a maximum range case, Cd=2Cdo. Therefore, in a maximum flight duration situation, the drag coefficient is even greater. Hence, your suggestion that Vmd is the desirable speed is false.