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6.06 Theory of Flight
4.06 Theory of Flight - Drag
6.06 Theory of Flight - Review
1. Lift acts 90 degrees to what?
The chord
2. As lift increases what happens to drag?
It increases
3. Define Centre of Pressure
The point in an airfoil where the average pressure of a
wing lies
4. Define Angle of Attack
The angle at which the airfoil meets the relative airflow
6.06 Theory of Flight - Drag
MTPs
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Drag
Types of Drag
Wing tip vortices
Streamlining
Flying for Range
and Endurance
 Best angle versus
best rate
6.06 Theory of Flight - Drag
Drag
 Is the resistance an airplane experiences in
moving forward through the air
6.06 Theory of Flight – Types of Drag
There are 2 main types of Drag
1. Parasite Drag– This drag is further
broken down
 Form drag
 Skin Friction
2. Induced Drag
6.06 Theory of Flight – Types of Drag
Parasite Drag
Drag of all those parts the airplane which DO
NOT contribute to lift
This drag is hard to eliminate but it can be
minimized
Landing gear
Antennas
Struts
Wing tip fuel tanks
6.06 Theory of Flight – Types of Drag
Form Drag
 Drag created by the for
or shape of the body as it
resists motion through
the air
6.06 Theory of Flight – Types of Drag
Skin Friction
The tendency of air
flowing over the body
to cling to its surface
What causes it to
resist motion?
Ice on the wings
Dirt build up
6.06 Theory of Flight – Types of Drag
Induced Drag
Caused by those parts of an airplane which
are active in producing lift
Cannot be eliminated
Lift
Drag
6.06 Theory of Flight – Types of Drag
Induced drag can be reduced with a high
aspect ration
6.06 Theory of Flight – Wing tip vortices
 Over the top of the wing the
airflow goes inward
 Under the bottom of the wing
the airflow moves outward
Due to the
pressure changes
This creates a swirling motion off the wing tip called a vortex
6.06 Theory of Flight – Streamlining
 The less drag you have…
 Flying a glider: the further you can fly
 Flying an airplane: the less fuel you use
 Therefore streamlining is important
 A design device by which a body is shaped
to minimize drag
6.06 Theory of Flight – Gliding for Range
An aircraft will glide further if you
optimized the lift / drag ratio
The airspeed that gives the best lift to
drag ratio is called “Gliding for Range”
Why would this be useful?
6.06 Theory of Flight – Gliding for Endurance
An airspeed slightly less than best range
will allow the aircraft to stay in the air the
longest amount of time
This is called gliding
for maximum endurance
Why would this be useful?
6.06 Theory of Flight – Best Angle of climb
Distance travelled versus time
Affected by wind
The speed which gives the most
horizontal distance for a given time
Why would this be useful?
6.06 Theory of Flight – Best Rate of climb
Altitude gained versus time
Not affected by wind
The speed which gives the most altitude
for a given time
Why would this be useful?
6.06 Theory of Flight – Confirmation
1. Fill in the diagram
2. Is it possible to eliminate induced drag?
Why or why not?
6.06 Theory of Flight – Confirmation
3. What is the difference between
maximum glide and maximum endurance
4. Is an aircraft’s best rate speed affected
by wind?
5. What are some ways to minimize drag?