Lecture 2 - Overview of Aircraft Static and Dynamic Stability Flashcards
(22 cards)
What is longitudinal stability connected to?
CG
What is CG (4 things)
Where mass is considered to be concentrated
Point by which aircraft pitches, rotates, or yaws
Point where a/c balances
It’s position changes
What is another name for centre of lift? What is it? How can it change?
Centre of lift = centre of pressure
Point at which overall upward force of wing is.
It changes with AoA; moves forward when AoA increases.
Where is the wing’s aerodynamic centre for a subsonic a/c? What’s it used for? Does it change?
Approx. 1/4 chord along wing from LE for subsonic a/c
Used as a reference point for defining pitching moment on wing.
Constant within certain AoA.
How do you make an unstable system stable?
Apply forces or moments
What happens when an aircraft is in trim?
Forces and moments are balanced, WRT CG.
Is being “in trim” a stable state?
Not necessarily; as this state is perturbed, a/c departs from equilibrium
Difference between trimmed flight and stability?
Trim is concerned with equilibrium; stability is concerned with maintaining equilibrium.
What is static stability? What is it evaluated relative to? What are the 2 types?
Initial tendency to return to equilibrium after disturbance
Relative to steady-state, trimmed flight condition
Statically unstable: divergence from equilibrium after disturbance
Neutral static stability: no moments; a/c holds disturbed condition
Three types of dynamic stability?
Dynamically stable
Neutral stability
Dynamically unstable
Two types of motion?
Oscillatory: dynamics (can analyse angular frequency, damping coefficient, etc.)
Non-oscillatory: Subsidence and divergence, neutral
Angle notation for roll, pitch, yaw axes
Roll angle: Φ
Pitch angle: θ
Yaw angle: Ψ
Angular velocity notation for roll, pitch, yaw axes.
Roll rate: p
Pitch rate: q
Yaw rate: r
Velocity components for roll, pitch, yaw axes
Roll velo. comp.: u
Pitch velo. comp.: v
Yaw velo. comp.: w
Aerodynamic force components for roll, pitch, yaw axes
Roll axis force: X
Pitch axis force: Y
Yaw axis force: Z
Aerodynamic moment components for roll, pitch, yaw axes
Roll moment: L
Pitch moment: M
Yaw moment: N
Moments of inertia for roll, pitch, yaw axes
Products of inertia for roll, pitch, yaw axes
What parameters are included in “the notation”?
7
Angles
Angular velocities
Velocity components
Aerodynamic force components
Aerodynamic moments components
Moments of inertia
Products of inertia
AAVAA MP
“The notation” mnemonic
AAVAA MP
What are moments of inertia related to?
How much a body resists being moved.
Positive conventions for control surface deflection
Right aileron down
Trailing edge elevator down
Rudder trailing edge left
