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POF > Stability > Flashcards

Stability Flashcards

1
Q

Static stability

A

Initial response of the a/c

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2
Q

Dynamic stability

A

Change over time

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3
Q

Statically neutral

A

Push the ball and remains where it is pushed

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4
Q

Positive static

A

Pushed the ball it wants to return to original position

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5
Q

Negative static

A

Push the ball, it will continue to roll

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6
Q

2 different types of dynamic stability

A

A-periodic without oscillation

Periodic with oscillation

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7
Q

Neutral dynamic and static

A

Remains in the position it was pushed to

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8
Q

Positive static and neutral dynamic

A

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

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9
Q

Positive static and negative dynamic

A

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

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10
Q

Negative static, negative dynamic

A

Continues to get worst

A-periodic

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11
Q

Longitudinal stability

A

Stability in the pitch

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12
Q

Lateral stability

A

Stability in the roll

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13
Q

Directional stability

A

Yaw

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14
Q

Point on the wing where the force acts

A

AC

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15
Q

M Cm

A

Pitching moment
Lateral axis
Positive is up

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16
Q

L Ci

A

Rolling moment
Longitudinal axis
Positive is right

17
Q

N Cn

A

Yawing moment
Normal axis
Positive is right

18
Q

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

A

Increase the surface area

Move the tailplane further away

19
Q

Further aft CG

A

Decreases stability

20
Q

Further fwd CG

A

Increases stability

21
Q

Directional stability

A

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

22
Q

To improve directional

A

Increase the size of the tail

Increase the distance of the tail from the CG

23
Q

Lateral stability

A

All about the wings

24
Q

Lateral - AoA of the wings

A

Upgoing, Reduced, wants to pitch down

Downgoing, increases, wants to pitch down

25
Q

Improving lateral stability

A

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

26
Q

Decreases lateral stability

A

Anhedral wings

A keel below the CG will destabilise - vortral fins

Low wings

27
Q

Longitudinal stability

A

Disturbance in the pitch

28
Q

Absolute AoA

A

From the RAF to the zero lift line

Using absolute AoA makes it easier to determine the reaction force

29
Q

Cm formula and was is it and the most important factor

A

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

30
Q

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

A

Elevator is deflected upwards, trim tab further downwards

31
Q

Which direction does a bob weight move the control stick

A

Forwards

32
Q

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

A

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

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

33
Q

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

A

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

34
Q

Why is excessive lateral stability undesirable for transport a/c

A

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

35
Q

Reducing sweepback

A

Decreases static lateral stability

36
Q

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

A

Remains unchanged

POF (16 decks)

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