Definition
Horizontal tail surfaces whose angle of incidence (the angle at which they meet the oncoming airflow) can be changed in flight to trim the aircraft for varying load and speed conditions. Instead of relying solely on a small trim tab attached to the elevator, the entire horizontal stabilizer pivots, allowing the pilot to balance pitch forces over a wider range of center-of-gravity positions and airspeeds.
Plain English
These are tail surfaces at the back of the airplane that can be tilted up or down as a whole. Tilting them lets the pilot keep the nose at the right angle without having to constantly hold pressure on the controls.
Context Anchor
Seen in weight-and-balance and trim discussions, especially when loading changes the airplane’s balance point.
Derivation
Stabilizer comes from the Latin stabilis, meaning steady or firm. The horizontal stabilizer keeps the nose steady in pitch. Adjustable simply means it can be moved -- in this case, repositioned in flight rather than fixed in place.
Why Pilots Care
Sets a trim position that reduces the need for constant elevator input and lowers pilot workload.
Grounding Statement
Changing the stabilizer angle changes how the tail helps balance the airplane’s nose.
Intuition Check
Do not assume this means only a small trim tab moves. On aircraft with adjustable horizontal stabilizers, the main horizontal tail surface itself can change angle.
Example Sentence 1
On the larger jet, the pilot trims pitch by repositioning the adjustable horizontal stabilizer rather than relying on an elevator trim tab alone.
Example Sentence 2
During preflight the mechanic verified full travel of the adjustable horizontal stabilizers before the first flight of the day.