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A helicopter’s total power required curve is the resultant of:

  • A
    Induced power + rotor profile power - parasite power.
  • B
    Induced power + rotor profile power + parasite power.
  • C
    Induced power - parasite power - rotor profile power.
  • D
    Power required + power in hand.

Refer to figure.
Drag is the force that resists the movement of a helicopter through the air and is produced when lift is developed. Drag always acts parallel to the relative wind and is overcome by the engine turning the rotors.

The 3 types of drag acting on the helicopter are as follows:

  1. Induced Drag is the result of the rotor blades producing lift therefore, a helicopter in a hover as we know has a very high Angle of Attack (AoA) meaning the Induced Drag will also be the highest. As the helicopter transitions to forward flight the AoA becomes more efficient and therefore less AoA is required to maintain less Lift leading to a reduction of Induced Drag with increased speed.
  2. Parasite Drag is the result of the helicopter’s non lifting components moving thru the air such as the fuselage, landing gear, etc. Parasite drag increases with the increase of forward speed.
  3. Profile Drag is the frictional resistance of the blades moving through the air. As the airspeed increases the friction increases on the blades and therefore an increase of profile drag is evident.

The Total Drag is the resultant of all 3 types of drag as shown in the attached figure. The power required curve is to overcome the total drag meaning a result of Induced Drag, Profile Drag and Parasite Drag, therefore, the total power required is a result of induced power, profile power and parasite.

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