8.4- Flight Stability and Dynamics

Question 1

What limits the flight paths and altitudes of the aircraft?

Answer 1

Aerodynamic characteristics of the aircraft, propulsion and its structural strength.

Question 2

What is the vertical axis of movement?

Answer 2

Yaw

Question 3

What is the lateral axis of movement?

Answer 3

Pitch

Question 4

What is the longitudinal axis of movement?

Answer 4

Roll

Question 5

What direction does the nose go in a positive yaw?

Answer 5

To the right.

Question 6

What is positive pitch?

Answer 6

Raises the nose.

Question 7

What is the type of stability associated with roll?

Answer 7

Lateral

Question 8

What is the type of stability associated with pitch?

Answer 8

Longitudinal

Question 9

What is the type of stability associated with Yaw?

Answer 9

Directional

Question 10

What is static stability?

Answer 10

Initial tendency of an aircraft to return back to a position of equilibrium.

Question 11

What are the three types of static stability?

Answer 11

Positive
Negative
Neutral

Question 12

What is positive static stability?

Answer 12

Return to original state of equilibrium after being disturbed.

Question 13

What is neutral static stability?

Answer 13

Stay at new attitude when disturbed.

Question 14

What is negative static stability?

Answer 14

Continues to worsen after being disturbed.

Question 15

What is dynamic stability?

Answer 15

Aircraft response over time when disturbed from a given position.

Question 16

What is positive dynamic stability?

Answer 16

Oscillations that dampen out over time and it returns to normal.

Question 17

What is neutral dynamic stability?

Answer 17

Oscillations that never dampen out.

Question 18

What is negative dynamic stability?

Answer 18

Oscillations that get worse over time.

Question 19

What happens to a longitudinally unstable aircraft?

Answer 19

Tend to dive or climb progressively

Question 20

What is the result of the distance between CoG and aerodynamic centre being far away?

Answer 20

Longitudinal stability is high.

Question 21

What happens when a gust hits the lower front part of the nose?

Answer 21

Nose up rotation.

Question 22

When does positive longitudinal stability occur?

Answer 22

When the centre of gravity as the result of all aircraft weights is forward of the aerodynamic centre.

Question 23

What is directional stability ‘wethercock’?

Answer 23

Stability around the vertical axis.

Question 24

What happens in directional stability if the turning moment behind the centre of gravity is greater than in front?

Answer 24

The aircraft turns back to its original flight path.

Question 25

What design do some aircraft have aft of the centre of gravity to improve directional stability?

Answer 25

Increased surface area.

Question 26

What methods are there of increasing the surface aircraft aft of the centre of gravity?

Answer 26

Dorsal fin or keel surface.

Question 27

What else helps improve directional stability?

Answer 27

Sweep back of the wing.

Question 28

Which wing always produces more lift?

Answer 28

Forward going wing.

Question 29

What is lateral stability?

Answer 29

Stabilize the rolling effect.

Question 30

What four design effects give lateral stability?

Answer 30

Dihedral
Sweepback
Keel effect
Weight distribution

Question 31

What is the effective angle of attack?

Answer 31

The angle between the resultant velocity and the chord line.

Question 32

What do dihedral angles do?

Answer 32

Restore level flight.

Question 33

What is always at right angles to the lateral axis?

Answer 33

Lift

Question 34

In disturbed flight the lift is inclined in the direction of?

Answer 34

The lower wing.

Question 35

What is slideslip?

Answer 35

The aircraft glides to one side without changing flight direction.

Question 36

What is sideslip opposite too?

Answer 36

Relative wind.

Question 37

What is keel effect?

Answer 37

Type of lateral stability.

Question 38

What would strong keel effect result in?

Answer 38

Difficult to roll left and right.

Question 39

What part of the aircraft acts as a keel?

Answer 39

Fuselage.

Question 40

Which wing has greater keel effect, high or low?

Answer 40

High wing.

Question 41

What happens if an aircraft is designed with more stability in one direction more than the other?

Answer 41

Spiral dive or dutch roll.

Question 42

When does spiral dive exist?

Answer 42

When there is a greater effect on the directional stability than the lateral.

Question 43

What is dutch roll?

Answer 43

Lateral directional oscillation

Question 44

When does dutch roll occur?

Answer 44

Greater effect on lateral stability than on the directional stability.

Question 45

How is dutch roll partially overcome?

Answer 45

Reducing the sweep angle and improving the directional stability.

Question 46

How can dutch roll be anticipated and supressed?

Answer 46

Yaw dampening system.

Question 47

What is used to sense the degree of yaw and rate?

Answer 47

Rate gyro.

Question 48

What else can a yaw damper system assist with?

Answer 48

Single engine failure and coordinated turns.

Question 49

What systems are considered passive stability control?

Answer 49

Dihedral
Swept wing
Large vertical stabs
Keel surfaces
THS

Question 50

What is relaxed stability?

Answer 50

Systems that have opposing features that give neutral or negative stability.

Question 51

What does relaxed stability allow?

Answer 51

The aircraft to be designed purely for aerodynamic efficiency.

Question 52

What changed the equation of using active flight control systems?

Answer 52

Auto flight controls and fly-by-wire systems.