Figure: Drag / airspeed relation @~copters

Parasite_Drag - Curve "A"
~ the drag incurred from the nonlifting portions of the aircraft
~ includes the form drag and skin friction associated with the fuselage, cockpit, engine cowlings, rotor hub, landing gear, and tail boom
~ is very low at slow airspeeds and increases with higher airspeeds
~ goes up at an increasing rate at airspeeds above the midrange
Induced_Drag - Curve "B"
~ drag incurred as a result of production of lift
~ higher angles of attack which produce more lift also produce increased induced drag
~ decreases with increased aircraft airspeed
~ is the portion of the total aerodynamic force which is oriented in the direction opposing the movement of the blade
~ think of it as lift which is in the wrong direction
Profile_Drag - Curve "C"
~ the drag incurred from frictional resistance of the blades passing through the air
~ does not change significantly with angle of attack of the blade , but increases moderately as airspeed increases
Total_Drag - Curve "D"
~ presents the sum of the other curves A, B and C
Optimum - where Line "E" and Curve "D" cross each others
~ total drag is lowest
~ airspeed is there is the best for maximum endurance, best rate of climb, and minimum rate of descent in autorotation

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