Total Drag

1
Total Drag

• Chapter 2
• Lecture 7

2
Total Drag

• Total drag is made up of the sum of parasite drag
  and the induced drag.
• Figure 3-15 p. 74
• The parasite drag starts off at zero at zero
  velocity and increases
• The induced drag at zero velocity and drops off
  inversely
• The point where tow curves cross is drag minimum.

3
Drag Minimum

• Above and below this point drag increases.
• Range, rate of climb, and fuel consumption can be
  improved by slowing down the airplane to a
  certain point.
• Below that point performance begins to
  deteriorate again due to induced drag is building
  up more rapidly than parasite drag is reducing.

4
Equivalent Flat Plate Area

• This method of measuring drag, the parasite drag
  of the airplane is represented by the drag of a
  flat plate in the airstream.
• The equivalent flat plate area is really the
  ratio of parasite drag to dynamic pressure.

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Parasite Drag Coefficient

• The ratio of parasite drag to dynamic pressure
  times the area (wing area)
• The flat plate area and the parasite drag are
  related through the wing area.
• Table 3-1 p. 75
• What do we notice?

6
Pros of using flat plate area to calculate drag

• Convenient way to sum the drag of various
  components.
• Good comparison of the relative aerodynamics
  efficiency of various designs
• Flat plate area can be used to add up drag of
  various components of the airplane.

7
Special Types of Parasite Drag

• Interference Drag
• arises due to the junction of two bodies (wing
  fuselage)
• Cooling Drag
• associated with engine cooling (cowl flaps)
• Profile Drag
• wings parasite drag (drag in profile shape
  related to angle of attack)

8
Summary of Drag Definitions

• DEFINE EACH
• Pressure drag (form drag)
• Skin friction drag (viscous drag)
• Profile drag
• Interference drag
• cooling drag
• induced drag

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Ground Effect

• Drag alteration when flying near the ground
• A cushion of compressed air
• Downwash caused by vortex formation at wing tip
• When are you in ground effect?

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Quiz on Lecture 7Chapter 2

• Please take out a sheet of paper
• Include todays date and your name

11
Quiz on Lecture 7 Chapter 2

• List and explain 3 types of drag discussed today.
• What is ground effect?