The Axes of an Aircraft

Question 1

What are the three aces used to describe an aircraft?

Answer 1

• Longitudinal
• Lateral
• Normal

Question 2

Where does the centre of gravity act?

Answer 2

Through the point where all the balance of aircraft weight is in equilibrium.

Question 3

What is the primary effect of aileron? What is the secondary effect?

Answer 3

• Primary effect is roll about longitudinal axis

- Secondary effect is adverse yaw.

Question 4

What is flutter?

Answer 4

Rapid and uncontrolled oscillation of a control surface that results from the changes in pressure distribution over the surface as AoA is altered and when the CoG is aft of the hinge line.

Question 5

What can be used to increase the roll rate?

Answer 5

Use roll spoilers

Question 6

What are some methods to reduce adverse yaw?

Answer 6

1) Roll spoilers moving up to increase the drag on the downgoing wing.
2) Differential ailerons
3) Coupling of controls (rudder + aileron)
4) Frist ailerons

Question 7

How is motion about the lateral axis controlled?

Answer 7

• By the elevators.

- Also known as pitch

Question 8

What is the primary effect of elevator? Are there any secondary effects?

Answer 8

• Pitching

- Change in speed/altitude.

Question 9

When is the elevator used to control height?

Answer 9

With speed changes in level flight

Question 10

When is the elevator used to control speed?

Answer 10

At a constant power setting in a climb or descent.

Question 11

What are two different types of elevators?

Answer 11

• Elevator on horizontal stabiliser

- All moving tailplane.

Question 12

What is motion about the vertical (normal) axis called?

Answer 12

Yaw

Question 13

What is the rudder used for?

Answer 13

For yaw control

Question 14

What is the secondary effect of rudder?

Answer 14

Roll

Question 15

What are some factors that determine control effectiveness?

Answer 15

1) Size and shape of the control surface
2) Deflection angle
3) Airspeed
4) Moment Arm (Distance from CoG)

Question 16

What are artificial feel units?

Answer 16

Provide force feedback for the pilot to determine how far he has deflected the controls.

Question 17

What is a typical control harmony scale for rudder, elevator and aileron?

Answer 17

Aileron: 1
Elevator: 2
Rudder: 4

Question 18

What are the effects of an increased power setting on the aircraft?

Answer 18

Will pitch nose up and yaw to the left.

Question 19

What are the effects of a decreased power setting on the aircraft?

Answer 19

Will pitch nose down and yaw to the right.

Question 20

What are some design features to reduce slipstream and torque effects?

Answer 20

1) Offset thrust line
2) Automatic rudder trim
3) Regulating engine power at low speeds.

Question 21

What are some corresponding effects on the A/C with a change in airspeed?

Answer 21

• Increase in airspeed means pitch up and yaw right

- Decrease in airspeed means pitch down and yaw left