drag curve problem
 

if the a/c weight was increased what would happen to the speed for max end (min drag)anybody help with this

It is the angle of attack corresponding to (Cl**1.5/Cd)max which gives the theoretical angle of attack for max endurance in a piston engined aircraft. For a jet aircraft it is (Cl/Cd)max. This angle of attack gives an unique value of Cl, so in the equation L=Cl*1/2 rho V**2 S, at a given level, if weight is higher, then L must increase correspondingly. With Cl, 1/2 rho and S being constant, speed for max endurance will therefore increase by the square root of the mass ratio.

There may, however, be power plant efficiency factors which will modify this theoretical speed. It will also be sensible to increase the speed slightly to achieve a more stable airspeed/drag relationship and better propeller efficiency.


[This message has been edited by BEagle (edited 03 March 2001).]