L11 - Dynamic Longitudinal Stability

Question 1

what is Phugoid motion?

Answer 1

Long period oscillations

Question 2

What are the two types of osciallaiton?

Answer 2

Short and long (phugoid)

Question 3

What are the 6 degrees of freedom?

Answer 3

Longitudinal - X forces, Z forces, pitching moments

Lateral - Y forces, rolling and yawing moments

Question 4

What are the two types of solution to secnd order differential equations?

Answer 4

Homogenous (free response) and Particular solution (forced response)

Question 5

What are the three cases of characteristic equation outcome?

Answer 5

Case 1 - Two real roots (overdamped)
Case 2 - 2 complex conjugate (samped sinusoid, underdamped)
Case 3 - real double root (critically damped)

Question 6

What is x replaces with in second order differentials?

Answer 6

e^gamma*t

Question 7

What are eigenvalues?

Answer 7

Roots to the characteristic equation

Question 8

What is phugoid oscilation also knows as?

Answer 8

Dolphining

Question 9

How can the dynamic stability of the whole aircraft be modelled?

Answer 9

As two coupled mass dampers sytems, for short and long period oscillations.

Question 10

What effect does moving the cg aft have on stability?

Answer 10

longitundinal modes become aperiodic and eventualy unstable