Definition
Two related but distinct flight characteristics of an aircraft. Stability is the aircraft's tendency to return to its original flight condition after being disturbed (by a gust, control input, or change in power) without pilot effort. Controllability is the aircraft's responsiveness to pilot inputs, allowing the pilot to maneuver it as intended. Both are directly affected by weight and balance: loading outside approved limits — especially center of gravity (CG) outside the forward or aft limit — degrades one or both, sometimes severely.
Plain English
Stability is how well the airplane holds its own flight path on its own. Controllability is how well it responds when you move the controls. How the airplane is loaded affects both.
Context Anchor
Seen in weight-and-balance discussions when deciding whether the aircraft is loaded within approved limits before flight.
Derivation
Stability comes from Latin stabilis, meaning 'firm' or 'steady' — an aircraft that holds steady. Controllability comes from control, originally 'to check or verify against a record,' later 'to direct or command.' Together they describe an aircraft that is both steady on its own and responsive to the pilot's commands.
Why Pilots Care
An aft center of gravity reduces stability while increasing controllability; a forward center of gravity increases stability but can make the airplane heavy on the controls and reduce controllability.
Analogy
Think of balancing a broom in your hand. If the balance is in a safer, steadier place, small bumps are easier to manage. If the balance is too far the wrong way, even small movements can become hard to control.
Intuition Check
Do not read stability as simply “good” and controllability as simply “easy.” In this context, they are two different handling qualities, and changing the aircraft’s loading can improve one while reducing the other.
Example Sentence 1
Loading the aircraft with the CG aft of the rear limit reduced its stability and controllability, making the airplane harder to recover from a stall.
Example Sentence 2
The pilot verified that the loaded center of gravity kept both stability and controllability within safe limits for the flight.