Definition
A control surface hinge whose pivot axis is set back from the surface's leading edge, so that when the surface deflects, a portion of its leading edge protrudes into the airflow on the opposite side. On Frise-type ailerons, the offset hinge causes the leading edge of the up-going aileron to drop below the wing's lower surface, creating drag on the down-going wing to help counter adverse yaw.
Plain English
A hinge that isn't placed right at the front edge of a control surface, but a bit behind it. Because of that placement, when the surface tilts up, part of its front edge sticks down into the air below the wing, and that sticking-out part creates drag.
Context Anchor
Seen in descriptions of Frise-type ailerons and how hinge placement affects roll control and drag.
Derivation
"Offset" comes from the idea of being shifted away from a reference point. Here, the hinge is shifted back from the leading edge rather than being placed on it. That offset is what allows part of the surface to swing into the airflow when deflected.
Why Pilots Care
The added drag on the upward aileron helps cancel adverse yaw and produces more coordinated turns.
Analogy
It is like moving the pin of a door hinge slightly back from the door’s front edge, so the edge swings out in a different way when the door opens.
Intuition Check
Do not read “offset” as meaning damaged, bent, or misaligned. Here it means intentionally placed away from the usual hinge position to make the aileron move in a specific way.
Example Sentence 1
The Frise aileron uses an offset hinge so that when it deflects upward, its leading edge drops into the airflow beneath the wing and produces drag.
Example Sentence 2
During a left turn the right aileron rises on its offset hinge and the resulting drag helps keep the nose aligned with the turn.