M8.4 Flashcards
(27 cards)
What is stability?
Stability is the ability of an aircraft to return to or continue its original flight path.
What 2 main areas does stability affect?
- Manoeuvrability: The quality of an aircraft to be manoeuvred easily and withstand the stresses involved with the manoeuvre.
- Controllability: The capability of an aircraft to respond to a pilots control.
What is static stability?
Static stability refers to the initial tendency of an aircraft to return back to a position of equilibrium.
What is positive static stability?
Positive static stability: Has a tendency to return to its original state of equilibrium after being disturbed.
What is neutral static stability?
Neutral static stability: Has the tendency to stay in its new attitude when disturbed.
What is negative static stability?
Negative stability: Has the tendency to continue moving away from its original attitude after being disturbed.
What is dynamic stability?
Dynamic stability refers to an aircraft response over time when disturbed. Relates to wether an aircraft will continue to oscillate after a disturbance.
What is positive dynamic stability?
Positive dynamic stability:Has oscillations that dampen over time, gradually returning to an equilibrium state.
What is neutral dynamic stability?
Neutral dynamic stability: Has oscillations that never dampen out.
What is negative dynamic stability?
Negative dynamic stability: Has oscillations that get worse over time.
What is longitudinal stability?
Longitudinal stability is the tendency for an aircraft to pitch up or down. (Stability around its lateral axis). A longitudinally unstable aircraft will tend to dive or climb, in bad cases it could stall.
What is longitudinal stability dependant on?
- The location of the wing with respect to the centre of gravity
- Location of the horizontal tail surfaces with respect to the centre of gravity
- Area or size of the tail surfaces
What is directional stability?
The stability of an aircraft about its vertical axis.
What two design features contribute the most to directional stability?
The vertical stabiliser and the sweep back of the wing.
When is an aircraft considered directionally stable in terms of turning moments?
When the yawing moment behind the centre of gravity is greater than in front of it, causing the aircraft to return to its original path.
Name two additional surfaces used to improve directional stability.
The dorsal fin and keel surface.
How does wing sweepback enhance directional stability?
When the aircraft yaws, the forward wing presents a large frontal area, creating more drag and generating a restoring yawing moment towards the original flight direction.
What is lateral stability in an aircraft?
Lateral stability is the aircraft’s tendency to maintain or return to its original bank attitude around the longitudinal axis after a disturbance.
How does dihedral contribute to lateral stability?
In a sideslips, the down-going wing experiences an increase in AOA, producing more lift and rolling the aircraft back to level.
How does wing sweepback help lateral stability?
During a sideslip, the down-going wing presents a longer effective leading edge, producing more lift and aiding roll recovery.
What is the keel effect and how does it aid lateral stability?
The fuselage acts like a keel; when the aircraft yaws during a sideslip, the side facing the airflow receives more force, helping the aircraft realign with the relative airflow.
How does weight distribution affect lateral stability?
A low centre of gravity helps stabilise the aircraft by resisting roll, much like the pendulum effect.
How can a spiral dive happen?
Spiral dives can happen when there is a greater effect on the direction stability than on the lateral stability.
How can a Dutch roll happen?
Dutch rolls happen when there is a greater effect on the lateral stability then on the directional stability
