Control Surfaces

Question 1

What are the primary flight controls?

Answer 1

• Aileron
• Elevator
• Rudder

Question 2

What is an elevator?

Answer 2

The elevator is the horizontal surface on the tail of the aircraft. It is controlled by either pulling out or pushing in the control column of the pilot.

Question 3

How does an elevator work?

Answer 3

An elevator’s up and down movement allows the aircraft to pitch nose up or down depending on it’s deflection. This is done by creating an AoA on the tailplane, therefore creating more of less lift on this surface and either lifting it or allowing it to sink.

Question 4

What are ailerons?

Answer 4

Ailerons are the controlling/deflecting surfaces on the outer, trailing edge of the main wing. They are controlled by rolling the pilot’s control column either left or right.

Question 5

How do ailerons work?

Answer 5

Aileron’s either lift or allow the wing on their respective side to sink due to their deflection into the airflow. This creates more of less lift depending on their deflection. Ailerons will always work opposite to each other. (one goes up the other goes down)

Question 6

What is a rudder?

Answer 6

The rudder is the vertical surface on the tailplane of an aircraft. It is controlled by the pilot’s rudder pedals.

Question 7

How does the rudder work?

Answer 7

The rudder is deflected into the airflow by use of the rudder pedals and either creates a left or right side force (lift) depending on it’s deflection. This will in turn yaw the nose of the aircraft in the opposite direction.

Question 8

How does speed affect the handling qualities of the controls?

Answer 8

The higher the speed the stiffer the controls but the more responsive their actions will be.

Question 9

What is elevator reversal?

Answer 9

At high speed, loads/forces on the controls may twist the horizontal tailplane and create reverse forces.

Question 10

What is adverse yaw?

Answer 10

Adverse yaw is yaw of an aircraft in the opposite direction of the roll.

Question 11

How is adverse yaw caused?

Answer 11

Adverse yaw is caused by the increased drag of the down-going aileron (up-going wing) and decreased drag on the up-going aileron (down-going wing) which will pull the up-going wing backwards and create a yawing force in the opposite direction of the roll. :-)

Question 12

How can adverse yaw be reduced?

Answer 12

• Differential ailerons

- Frise ailerons

Question 13

What is aileron reversal?

Answer 13

Aileron reversal is the twisting of the wing due to large aileron lifting forces creating a force that is opposite to the pilot’s input.

Question 14

What are spoilers?

Answer 14

Spoilers are surfaces on the upper part of the wing that protrude into the airflow and disrupt the laminar airflow over the wing.

Question 15

What are three reasons spoilers may be used for?

Answer 15

• Roll control
• Speed brakes
• Ground lift dumpers

Question 16

What is the difference between differential and non-differential spoilers?

Answer 16

With differential spoilers, when they are partially extended as speed brakes, one side will deflect up further while the other will retract slightly to aid in roll control. Non-differential spoilers only one side will deflect up further while the other side remains in its position.

Question 17

Give six reasons for spoilers?

Answer 17

• Aileron reversal
• Aileron is limited in size and effectiveness
• Span-wise flow reduces aileron effectiveness
• Adverse yaw tendencies especially on swept wing aircraft
• Speed brakes
• Ground spoiler (lift dumpers)

Question 18

What limits the use of spoilers?

Answer 18

• Aircraft speed

- Spoiler design limit (hydraulic system capabilities)

Question 19

How is spoiler blow back prevented?

Answer 19

Flying in the correct speed range and not exceeding any limits.

Question 20

How do you correct for spoiler blow back?

Answer 20

• Reduce speed

- Recycle spoiler controls

Question 21

What are leading-edge slats?

Answer 21

Leading edge slats are protruding surfaces on the leading edge of the wing aiding in lift production at slow speed and high AoA’s such as during landing and take-off by increasing a wing’s camber and MAC and therefore the Cl. A slot created between the slats and the wing allows re-energizing airflow to move to the upper surface of the wing at high AoA’s.

Question 22

What are Krueger flaps?

Answer 22

Krueger flaps are protruding surfaces on the leading edge of the wing which aid in the lift production of the main wing my increasing the wing’s surface area and camber (Cl).

Question 23

What are fowler flaps?

Answer 23

Fowler flaps are surfaces located at the trailing edge of the wing which extend back and down from the main wing. They increase a wing’s surface area, camber and therefore the Cl. Slots between the main wing and the flaps allow re-energizing airflow to move to the upper surface of the wing.

Question 24

What are flaps used for on an aircraft?

Answer 24

Increase lift producing capability of a wing at slow speed.

Question 25

What are the effects of extending flaps in flight?

Answer 25

• Increased lift (initial ballooning)
• Increased drag (nose up or down pitch depending on flap and wing position relatively to the CoG)
• Speed reduction
• Lower nose attitude
• Steeper descent angle

Question 26

What are the effects of raising flaps in flight?

Answer 26

• Reduced lift (initial sinking of aircraft)
• Reduced drag (nose up or down pitch depending on flap and wing position relatively to the Cog)
• Speed increase
• Higher nose attitude
• Shallower descent angle

Question 27

How do flaps affect the take-off ground run?

Answer 27

Flaps reduce the take-off ground run if set in the correct (take-off) flap setting.