Stability

Question 1

Static stability

Answer 1

Initial response of the a/c

Question 2

Dynamic stability

Answer 2

Change over time

Question 3

Statically neutral

Answer 3

Push the ball and remains where it is pushed

Question 4

Positive static

Answer 4

Pushed the ball it wants to return to original position

Question 5

Negative static

Answer 5

Push the ball, it will continue to roll

Question 6

2 different types of dynamic stability

Answer 6

A-periodic without oscillation

Periodic with oscillation

Question 7

Neutral dynamic and static

Answer 7

Remains in the position it was pushed to

Question 8

Positive static and neutral dynamic

Answer 8

Tries to get back to equilibrium but it doesn’t get better and it doesn’t get worst, constant oscillations at the same heights

Question 9

Positive static and negative dynamic

Answer 9

Tries to get to equilibrium but the oscillations get worst over time

Question 10

Negative static, negative dynamic

Answer 10

Continues to get worst

A-periodic

Question 11

Longitudinal stability

Answer 11

Stability in the pitch

Question 12

Lateral stability

Answer 12

Stability in the roll

Question 13

Directional stability

Answer 13

Yaw

Question 14

Point on the wing where the force acts

Answer 14

AC

Question 15

M Cm

Answer 15

Pitching moment
Lateral axis
Positive is up

Question 16

L Ci

Answer 16

Rolling moment
Longitudinal axis
Positive is right

Question 17

N Cn

Answer 17

Yawing moment
Normal axis
Positive is right

Question 18

How can you change the tail plane to make it more stable

Answer 18

Increase the surface area

Move the tailplane further away

Question 19

Further aft CG

Answer 19

Decreases stability

Question 20

Further fwd CG

Answer 20

Increases stability

Question 21

Directional stability

Answer 21

Stability in the yaw

Airflow to the side of the nose, a/c will want to yaw into the airflow as it hits the tail

Question 22

To improve directional

Answer 22

Increase the size of the tail

Increase the distance of the tail from the CG

Question 23

Lateral stability

Answer 23

All about the wings

Question 24

Lateral - AoA of the wings

Answer 24

Upgoing, Reduced, wants to pitch down

Downgoing, increases, wants to pitch down

Question 25

Improving lateral stability

Answer 25

Low mounted wing has to be dihedral to make it more stable High mounted wing has to be anhedral to reduce the dihedral effect Increase the sweepback A keel surface above the CG

Question 26

Decreases lateral stability

Answer 26

Anhedral wings A keel below the CG will destabilise - vortral fins Low wings

Question 27

Longitudinal stability

Answer 27

Disturbance in the pitch

Question 28

Absolute AoA

Answer 28

From the RAF to the zero lift line Using absolute AoA makes it easier to determine the reaction force

Question 29

Cm formula and was is it and the most important factor

Answer 29

Cm = m/qsL Natural ability for the a/c to pitch in response to a disturbance Most dominant is IAS square (q) which means the faster we go the less Cm

Question 30

In S and L with a reduction in speed, what must be done to the elevator and trim tab to make the stick force 0

Answer 30

Elevator is deflected upwards, trim tab further downwards

Question 31

Which direction does a bob weight move the control stick

Answer 31

Forwards

Question 32

The level of effect on stick force by a change in speed from a trimmed position

Answer 32

High speed small change in speed = less effect on stick force Low speed small change in speed = bigger effect on stick force

Question 33

For an a/c to exhibit static longitudinal stability where do you want the lift to act

Answer 33

Aft of the CG, extra lift will push the nose down again Fwd of the CG, the extra lift will push the nose further up

Question 34

Why is excessive lateral stability undesirable for transport a/c

Answer 34

During sideslip, e.g during a cross wind, it may impose excessive demands on roll control

Question 35

Reducing sweepback

Answer 35

Decreases static lateral stability

Question 36

On fully powered controls what happens to the neutral position of the control column when trimming

Answer 36

Remains unchanged