Lecture 13 - Aircraft Dynamic Lateral and Directional Stability and Dynamic Modes Flashcards
(15 cards)
Roll angle symbol in terms of roll rate symbol
Newton’s 2nd law for rotational motions
What stability/instability can lead to a dutch roll?
Lateral stability
Directional instability
What does dutch role mode begin with? What follows?
Yawing; rolling and sideslipping.
What happens to CG trajectory during dutch roll?
Remains approx. straight line
What is the relationship between yaw and roll motions in dutch roll?
Oscillatory; synchronised in phase, but 90 degrees shifted. Similar amplitudes.
What starts a spiral mode?
Small increase in roll angle
What stability/instability leads to spiral mode?
Directional stability; lateral instability.
How is the spiral model characterised with regard to roots?
1 real root
How quickly foes the spiral model develop?
Slowly; t>=100s
How is spiral mode controlled with design?
Dihedral
With dynamic modes, what is the criteria for stability WRT the eigenvalues?
At least one must have -ve real parts
With dynamic modes, what is the criteria for instability WRT the eigenvalues?
At least one must have +ve real parts
With dynamic modes, what is the criteria for neutral stability WRT the eigenvalues?
At least one has 0 real value
How can you tell whether a system is oscillatory or non-oscillatory from the roots?
Complex = oscillatory
Real = non-oscillatory
