List and explain the different types of parasitic drag?

Answer 1

• Parasite drag

  This drag is created by the uneven surface of the aircraft, like opening, obstruction on the skin of the fuselage and wings. There are different types of parasitic drags, these types of drags are on the following:

  1. Form drag
  2. Skin friction
  3. interference drag
  1. Form drag

  Profile drag is also known as form drag. Profile drag is the drag produced by the action of the rotor blades being forced into the oncoming airflow. If a rotor blade was cut in half from the front of the blade (leading edge) to the rear of the blade (trailing edge), the resulting shape when looking at the cross-section is considered to be the blade "profile". For a rotor blade to produce lift, it must have an amount of thickness from the upper skin to the lower skin, which is called the "camber" of the blade. In general terms the greater the camber, the greater the profile drag.

  This is because the oncoming airflow has to separate further to pass over the surfaces of the rotor blade. The blade profile for a given helicopter has been designed as a compromise between producing sufficient lift for the helicopter to fulfil all of its roles, and minimising profile drag. To alter the amount of lift produced by the rotor system, the angle of attack must be altered. As the angle of attack is increased then the profile drag also increases.

  1. Skin friction

  Skin friction drag is caused by the actual contact of the air particles against the surface of the aircraft. This is the same as the friction between any two objects or substances. Because skin friction drag is an interaction between a solid (the airplane surface) and a gas (the air), the magnitude of skin friction drag depends on the properties of both the solid and the gas. For the solid airplane, skin fiction drag can be reduced, and airspeed can be increased somewhat, by keeping an aircraft's surface highly polished and clean. For the gas, the magnitude of the drag depends on the viscosity of the air. Along the solid surface of the airplane, a boundary layer of low energy flow is generated. The magnitude of the skin friction depends on the state of this flow.

  1. Interference drag

  Interference drag is a component of parasitic drag which is caused by vortices. Whenever two surfaces meet at a sharp angle on an airplane, the airflow has a tendency to form a vortex. Drag is created by acceleration of air in to this vortex, by doing this the aircraft will form a low pressure area. With the help of primary methods interference drag could be reduced, this method will include eliminating any sharp angles on the aircraft by a certain means.drag