redblue,
I note from your profile that you fly C152 aircraft, and that Intruder, who just responded flys B747 aircraft. We still need to know whether your enquiry relates to propeller or Jet aircraft to respond appropriately.
What Intruder has said in the second sentence is absolutely correct for a jet aircraft, but certainly not for a propeller aircraft.
Both Max Endurance and Max Range are highly dependant upon Fuel Flow. There is a direct relationship between Fuel Flow and Power for a propeller aircraft, and between Fuel Flow and Thrust for a jet aircraft. Consider the following -
Power = Force X Velocity, and putting it into aircraft terms -
Power = Thrust X TAS
So, for the prop aircraft, Fuel Flow is on one side of the equation, and for the jet, on the other.
For the jet aircraft, thrust (and therefore Fuel Flow) is ALMOST (but not quite) constant over the entire speed range. Therefore, without even knowing the engine installed, I can extract the best holding speed from the conventional drag curve as the speed for best L/D ratio, i.e. VMD, the bottom of the Drag curve, and Intruder is absolutely correct.
For the propeller aircraft, thrust, for a given power setting declines constantly as speed increases, and the optimum holding speed can NOT be directly found from the conventional Drag curves. Instead, you need to refer to a POWER Required curve, a different beast to the Drag (Thrust required) curves. From this you can extract the speed for Minimum Power, which will be the speed for minimum Fuel Flow, that is, best holding sped. This speed will invariably be BELOW the optimum L/D speed. Just how far below will depend upon the characteristics of the propeller installed.
And we haven't talked of Maximum Range yet, that too, depends upon whether you're asking about a propeller or jet aircraft.
Regards,
Old Smokey