Definition
Describes an instrument or control system in which a small input drives a secondary mechanism (a servo) that provides the actual sensing or actuating force, producing a faster or more accurate response than a purely mechanical system. In a servo-assisted vertical speed indicator, a servo mechanism augments the standard pressure-diaphragm sensing to display rate-of-climb or descent changes more quickly and with less lag.
Plain English
A helper mechanism inside the instrument does some of the work, so the needle reacts faster and more accurately than it would on its own.
Context Anchor
Seen in discussions of the vertical speed indicator, especially when comparing basic pressure-operated instruments with designs that respond more quickly.
Derivation
From Latin servus, meaning 'servant.' A servo is literally a small mechanism that 'serves' the main system by doing part of the work. Knowing this helps: a servo-assisted instrument has an internal helper assisting the primary sensing element.
Why Pilots Care
Reduces lag in the VSI reading, allowing pilots to make more timely corrections during instrument flight.
Analogy
It is like power steering in a car. The driver still controls the car, but a powered helper makes the movement easier and more responsive.
Intuition Check
Servo-assisted does not mean the autopilot is flying the airplane. It means a small automatic mechanism is helping the instrument move or respond.
Example Sentence 1
The aircraft was equipped with a servo-assisted VSI, so the needle responded almost immediately when the pilot adjusted pitch.
Example Sentence 2
During the approach, the pilot relied on the servo-assisted instrument to maintain a precise descent profile.