8.4 Flight Stability And Dynamics Flashcards
What are the two types of stability?
- static stability
- dynamic stability
What is static stability?
When an aircraft is displaced from level flight, it will return to its equilibrium position
What are the three types of static stability?
- positive (moves back)
- negative (moves away)
- neutral (no movement)
What is dynamic stability?
The continuous motion of a body over time
- only when there is a POSITIVE static stability present
What are the three types of dynamic stability oscillations?
Divergent (negative dynamic stability)
Damped (positive dynamic stability)
Undampened ( neutral dynamic stability)
What are the three aircraft axis’?
- longitudinal
- lateral
- vertical
What occurs on the longitudinal axis?
The roll movement
What occurs on the lateral axis?
The pitch movement
What occurs on the vertical axis?
The yaw movement
What is another name for the directional stability?
Weathercock stability
What does the sweep back of a wing increase?
Directional stability
What are two other ways of increasing the directional stability on older or military aircraft?
- dorsal fin
- keel surface
What determines the lateral stability?
- angle of attack
- dihedral angle
- sweepback angle
What is an advantage of the dihedral angle?
It helps restore level flight
What is the side-slip angle?
The angle between the aircraft centreline and the side-slip direction
What is “Dutch Roll”?
It exists when there is a greater effect on the lateral stability than the directional stability
What type of aircraft is “Dutch wing” found on?
All aircraft with swept wings
How can the directional stability be increased?
Increasing the size of the vertical stabiliser (however this increases weight and drag)
What do most aircraft have to improve directional stability instead of increasing the size of the vertical stabiliser?
Yaw Damping System - automatic system deflects control surface on the vertical stabiliser (rudder)
With directional stability, would a “forward-going” wing produce more or less lift?
More lift
What is longitudinal stability?
The stability of the aircraft around the lateral axis
What happens if the distance between the CofG and the aerodynamic centre is:
- Large?
- Small?
- Large = longitudinal stability is high
- Small = longitudinal stability is low
