Uncontrolled copy not subject to amendment

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Uncontrolled copy not subject to amendment

• Principles of Flight

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Principles of Flight

• Learning Outcome 1
• Know the principles of lift, weight, thrust and
  drag and how a balance of forces affects an
  aeroplane in flight
• Part 2

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Principles of Flight
Revision
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Questions

• Newtons 3rd Law States
• Every object has weight.
• Weight equals lift during flight.
• Every action has an equal and opposite reaction.
• Every force causes an object to move.

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Questions

• In which direction does LIFT operate relative to
  airflow?
• Parallel to it.
• Perpendicular (at 90o) to it.
• c. Straight up.
• d. Straight down.

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Questions
What has happened to the air pressure at point
B?

1. It is greater than at point A.
2. It is greater than at point C.
3. It is the same as point C.
4. It is lower than at point A.

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Drag and Thrust

• Objectives
• 1. Explain Drag and Thrust.
• 2. Describe the effect that Streamlining has on
  Drag.
• 3. State the effect that Airspeed has on Drag.
• Describe the relationship between Drag and Thrust
  
• when an aircraft is
• a. At Constant Speed.
• b. Accelerating.
• c. Decelerating.

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Drag and Thrust
Lift
Thrust
Drag
Weight
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Thrust
How do we produce Thrust? Propellers Jet
Engines
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Thrust
Remember Newtons 3rd Law? The engine achieves
this by pushing the air backwards from either
through a propeller or from the rear of a jet
engine. The amount of Thrust depends on engine
size, etc.
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Drag
What is Drag? Remember riding a bicycle into a
wind or riding faster?
PHEW!!
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Variation of Drag with Airspeed
The amount of Drag varies with the square of the
Airspeed. So, Double the Airspeed, then Drag is
Four times as much! Triple the Airspeed, then
Drag is Nine times as much!
Drag
Airspeed
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Drag
Drag is the force which hinders your
progress. The faster you go the more drag you
feel. We need Thrust to overcome the
Drag. Consider
Maximum Drag. 20 people needed on the team.
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Drag
What happens we pull a ball of the same diameter
as the plate?
Drag is reduced by 50. Now only 10 people
needed on the team.
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Drag
What happens we streamline a shape of the same
diameter?
Drag is reduced to 5. Only 1 person needed on
the team.
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Form Drag
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Drag
This type of drag is Form Drag, ie the shape of
the object. So do we need
OR?
This Shape?
This Shape?
Reducing Drag, reduces the amount of Thrust
required!
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Examples of Streamlining
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Surface Friction Drag
Boundary layer

• Total surface area
• Viscosity of the air
• Thickness of the boundary layer

Surface friction drag is reduced by smooth
surfaces
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Interference Drag

• Reduced by adding fairings

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JSF
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Zero Lift Drag
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Lift Dependent Drag
Relatively High Pressure
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• Formation of Wingtip Vortices

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• Effect of Speed on Wing Tip Vortex

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Effect of Aspect Ratio on Wing Tip Vortex
HIGH ASPECT RATIO
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Vortex Drag
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Drag
Drag has several components as the following
Tree will illustrate
Vortex Drag
Surface Friction Drag
Interference Drag
Form Drag
Lift Dependent Drag
Zero Lift Drag
Total Drag
Increments of Zero Lift Drag
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Drag

• Drag can be represented by the following graph

DRAG
ZERO LIFT DRAG
LIFT DEPENDENT DRAG
IAS
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Thrust and Drag in Straight Level Flight
Aircraft Accelerating What is the difference
between Thrust and Drag?
Thrust is Greater than Drag
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Thrust and Drag in Straight Level Flight
Aircraft Decelerating What is the difference
between Thrust and Drag?
Drag is Greater than Thrust
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Thrust and Drag in Straight Level Flight
Aircraft Constant Speed What is the difference
between Thrust and Drag?
Thrust Drag
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Straight Level Flight
For Straight Level Flight at Constant Speed ALL
Forces are in Balance
Lift
Thrust
Drag
Weight
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ANY QUESTIONS?
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Drag and Thrust

• Objectives
• 1. Explain Drag and Thrust.
• 2. Describe the effect that Streamlining has on
  Drag.
• 3. State the effect that Airspeed has on Drag.
• Describe the relationship between Drag and Thrust
  
• when an aircraft is
• a. At Constant Speed.
• b. Accelerating.
• c. Decelerating.

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Questions
What is the force called that drives an aircraft
forwards? Lift Weight Drag Thrust
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Questions
What is the force called that resists the forward
motion of an aircraft? Lift Weight Drag Thrust
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Questions
If you speed is doubled, by how much would the
Drag be increased? x2 x4 x6 x8
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Questions
If Thrust Drag and Lift Weight then the
aircraft is Climbing Flying Straight Level
and Accelerating Flying Straight Level and
Decelerating Flying Straight Level at Constant
Speed
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