Stability

Question 1

What is Static Stability?

Answer 1

A statically stable system reacts to disturbances by returning to the previously established equilibrium

Question 2

What is Static Instability?

Answer 2

A statically unstable system reacts to disturbances by moving further away from the established equilibrium

Question 3

What is Neutral Stability?

Answer 3

A neutrally stable system finds itself in equilibrium in whatever state it reaches after experiencing a given disturbance, neither tending towards the previous equilibrium nor away from it

Question 4

What is dynamic stability?

Answer 4

Dynamic stability refers to the tendency of a disturbed system to return to an established equilibrium over time.

Dynamically stable systems are either aperiodic (equilibrium restored through a single correction of the disturbance) or periodic (experience dampened oscillations until flatlining upon reaching equilibrium)

Question 5

What is dynamic instability?

Answer 5

Dynamic instability is the tendency of a system to move away from its established equilibrium over time upon experiencing a disturbance.

Dynamically unstable systems experience increascing oscillations rather than dampened oscillations

Question 6

What is the Neutral Point of the Aircraft?

Answer 6

The point along the longitudinal axis at which changes in angle of attack do not change the pitching moment

This point is fixed for any given aircraft

(It is nalogous to the Aerodynamic Center of an airfoil but for the entire plane)

Question 7

What is the relationship between longitudinal static stability and the Neutral Point?

Answer 7

For longitudinal (Pitch) static stability, the centre of gravity of the aircraft must always be forward of the neutral point

Question 8

Behavior of a longitudinally statically stable Aircraft

Answer 8

Changes in angle of attack produce an inverse change in the pitching moment

i.e, if the angle of attack increases clockwise, the pitching moment counterclockwise becomes more intense.

Question 9

Behavior of a longitudinally statically unstable Aircraft

Answer 9

Changes in angle of attack produce directionally commensurate changes in pitching moment

i.e, if the angle of attack increases, the pitching moment clockwise increases as well, increasing pitching tendency

Question 10

What is the relationship between tail volume and Directional (Yaw) stability?

Answer 10

Increasing Tail Volume increases directional stability of the aircraft

Question 11

What is the primary method used to achieve Lateral (Roll) Static stability?

Answer 11

Wing positioning/Angle