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Theory of Flight

6.03 Secondary Controls and Secondary Effects of Controls

References: FTGU pages 15, 28, 29

Review

1. What control surface causes roll? 2. What movement does the elevator create? 3. Which axis does yaw act around? 4. Name the 2 types of fuselage construction.

6.03 Secondary Controls and Secondary Effects of Controls

•  MTPs: – Trim – Spoilers and Dive Breaks – Flaps – Secondary Effects of Controls – Coordination

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Trim •  Trim tab: adjustable device located on the

trailing edge of control surfaces •  Purpose – alleviates pressure on the controls •  Other types of trim are bungees connected to

the control column •  Most often only on the elevator

Trim

The trim tab moves in the opposite direction as the control surface

Trim

•  Trim in a glider – No trim tabs

•  Types - side trim (bungee) - stick trim (ratchet)

Bungee Trim

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Spoilers & Dive Brakes •  Primarily used in glider

flying

•  Spoilers – are hinged plates on top of the wing –  disrupt the airflow over

the wing to “spoil” the lift (Top)

•  Dive Brakes – increase drag (Bottom)

NASA applet - http://www.grc.nasa.gov/WWW/k-12/airplane/spoil.html

Spoilers & Dive Brakes

Purpose – allows the pilot to control the rate of decent during final approach and landing

- Spoilers and dive breaks increase drag and decrease lift

Flaps

•  Increases the camber of the wing •  This increases the lift and the drag •  Known as a high lift device •  Allows the aircraft to have a steeper approach

path with a decreased stall speed •  Allows glider pilot to fly slower in a thermal

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Flaps

•  Types of flaps

Secondary Effects

•  The air movement over control surfaces when they are moved causes adverse effects

•  When you yaw you get Roll •  When you roll you get Adverse yaw

Roll from Yaw

Roll from yaw •  When rudder is

applied, the wing on the outside of the turn moves faster, which causes it to experience more lift

Faster = more lift

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Roll from Yaw

YAW LEFT

CAUSES ROLL TO THE LEFT

MORE LIFT

FASTER

Adverse Yaw from Roll •  When ailerons are applied the plane has a tendency

to yaw away from the lower wing because of aileron drag.

•  The wing that rises experiences more lift, but also more induced drag.

Adverse Yaw from Roll

Left aileron DOWN LESS LIFT LESS DRAG

Right aileron UP MORE LIFT MORE DRAG

ROLL CAUSES ADVERSE YAW

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Coordination

•  To turn the aircraft without causing unnecessary drag, aileron and rudder must be used.

•  Using too much rudder will cause a “skidding turn”.

•  Using too little (or opposite) rudder will cause a “slipping turn”.

Coordination You slip in and skid out. Think of driving and skidding around a corner.

Confirmation 1.  How is adverse yaw created?

2.  Why is there roll when an airplane is yawed?

3.  What is the purpose of flaps?

4.  Name 2 types of trim.

5.  What is trim used for?

6.  What is the difference between slipping and skidding?

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Confirmation Draw on the airplane where the following go:

•  Flaps •  Spoilers •  Elevator Trim tab •  Aileron Trim tab

C-130 Deploying Flares