[Ref. Pilot’s Handbook of Aeronautical Knowledge, FAA-H-8083-25B Page 5-14]
Stability – the inherent quality to return to the original flight path.
There are 2 sub-types of stability
- Static Stability
– aircraft’s initial response (tendency) when disturbed from a given pitch, yaw, or bank - Dynamic Stability
– the aircraft response over time
Notes:
Positive static stability – initial tendency to return to the original state
Neutral static stability – initial tendency to remain in a new condition
Negative static stability – initial tendency to continue away from the original state
Positive dynamic stability – over time, tendency to return toward previous state
Neutral dynamic stability – over time, tendency to remain in new condition -neither increases nor decreases
Negative dynamic stability – over time, tendency to continue away from the original state and become more divergent
Stability affects maneuverability AND controllability.
Stability affects two areas significantly:
- Maneuverability ≈ Is it easy be changed and is it within limit?
- the quality of an aircraft that permits it to be maneuvered easily and to withstand the stresses imposed by maneuvers
- governed by weight, inertia, size and location of flight controls, structural strength, and powerplant.
- There is a trade-off between stability and maneuverability – e.g, a passenger airplane would require more stability, whereas a fighter requires greater maneuverability.
- Controllability ≈ Can it be changed/managed
- capability of an aircraft to respond to the pilot’s control, especially with regard to flight path and attitude,
BUT regardless of its stability characteristics.
- capability of an aircraft to respond to the pilot’s control, especially with regard to flight path and attitude,
Read More –
[Ref AircraftSystems: Mechanical,electrical,andavionicssubsystemsintegration,Third Edition ISBN: 978-0-470-05996-8]
# CG-CP, manoeuverability
The distance between the CG and the centre of pressure (CP) is a measure of how stable and also how manoeuvrable the aircraft is in pitch. The closer the CG and centre of pressure (CP), the less stable and more manoeuvrable the aircraft.