Stability Flashcards
The purpose of a trim tab
The purpose of a trim device or tab is to
- minimize the pilot’s effort when moving a control surface or
- maintaining that surface in a desired position
What are the 3 Axes of Motion and where do they intersect?
Longitudinal
Vertical
Lateral
These axis of rotation intersect at the center of gravity
The center of gravity (CG) is?
The center of gravity (CG) is the theoretical point where the entire weight of the airplane is considered to be concentrated
The center of pressure is also known as?
the center of lift
What is the center of Pressure?
The center of pressure
- (or center of lift)
- is a point along the chord line of an airfoil where lift is considered to be concentrated
What is stability?
Stability is the tendency of the aircraft to return to its original condition (position or attitude) after being displaced
What are the 2 types of stability and what do they mean?
What is positive static stability?
Positive Static: the initial tendency of the aircraft to return to its original position after it has been displaced
What is positive dynamic stability?
Positive Dynamic: the tendency of the aircraft to return to its original position over a period of time through a series of successive, smaller oscillations.
What is positive dynamic stability?
the aircraft returns to its original position through oscillations. Each oscillation is successively smaller until the original position is reached
What is negative Dynamic stability?
the aircraft oscillations increase in magnitude after an initial displacement
What is neutral dynamic stability?
the aircraft continues to oscillate at the same amplitude as the initial displacement
Logitudinal Stability involves what motion along what axis?
Involves pitching motion about the lateral axis
What does longitudinally stable mean?
Longitudinally stable means aircraft will naturally return to same attitude after being disturbed
The Center of Pressure moves _____ with increases in AoA until _____
The CP moves forward with increases in AoA until stall
The further aft of the CP that the CG is located, the LESS _______________
The further aft of the CP that the CG is located, the LESS longitudinally stable
What is a moment?
A moment is a
- force acting at a distance from an axis or fulcrum
- producing a rotation at that point
What is a force?
A force is a mass times an acceleration (F = M x a).
A moment equals force times ___________________
Moment equals force times the distance from the point of rotation (M = F x d)
The _____ is relied upon for longitudinal stability
The horizontal stabilizer is relied upon for longitudinal stability
With a normal Center of Gravity , an airplane will be nose heavy so we need a countering _________
With a normal CG, an airplane will be nose-heavy, so we need a countering tail down force to balance the nose
The horizontal stabilizer is mounted at a negative angle of incidence which provides __________
The horizontal stabilizer is mounted at a negative angle of incidence which provides a tail down (negative lift), nose up force
Longitudinal stability
The _____ the horizontal stabilizer and the _____ the distance the tail is located from the CG, the _______ the horizontal stabilizer’s contribution to longitudinal stability
The larger the horizontal stabilizer and the greater the distance the tail is located from the CG, the greater the horizontal stabilizer’s contribution to longitudinal stability
CG Too Far Forward
What happens?
- Higher stalling speed (bad).
- More stable (good, to a point).
- Slower cruise speed (bad).
- May not have enough elevator authority to flare in the landing (very bad).
