Chapter 22: Introduction to Stability and Control

Question 1

Static / Dynamic Stability Table

Static Stability, Dynamic Stability, Motion, Graph

Answer 1

Static - Dynamic - Motion - Graph
unst - unst - aperiodic - diverging deadbeat
neutral - neutral - aperiodic - constant
stable - stable - periodic - converging sin or deadbeat
stable - neutral - periodic - constant sin
stable - unstable - periodic - diverging sin

Question 2

Aerodynamic Center

Definition, Position for Sym, Cambered, SS Flight Wing

Answer 2

Point at which moments of a wing is constant
Symmetric: 25 %
Cambered: 23 - 27%
SS Flight: 50%

Question 3

Moment Coefficients

Moment, Symbol, Coeff, AC Attitude, Axis

Answer 3

Moment - Symbol - Coeff - AC Attitude - Axis
Pitch - M - CM - nose up - lateral
Roll - L - CL’ - roll right - longitudinal
Yaw - N - CN - yaw right - normal

Question 4

Longitudinal Static Stability

Factors (2)

Answer 4

Horizontal stabilizer Surface

Distance from CG

Question 5

Directional Static Stability

Factors (3)

Answer 5

Vertical stabilizer Surface
Distance from CG
Amount of fuselage behind CG

Question 6

Lateral Static Stability

Factors (5)

Answer 6

Dihedral
Sweepback
High Mounted Wing
High Keel Surface
Low CG

Question 7

Dorsal and Ventral Fin

Affect on Directional / Lateral Stability

Answer 7

Dorsal: good for directional, good for lateral
Ventral: good for directional, bad for lateral

Question 8

Stick Fix vs Stick Free Stability

What is unpowered powered controls considered?

Answer 8

Stick fix - more stable
Stick free - less stable
unpowered powered controls = stick fix

Question 9

Absolute AoA

Answer 9

Zero lift line = chord line for which wing produces no lift at AoA 2D = 0