Commercial Pilot License (CPL) 2026 – 400 Free Practice Questions to Pass the Exam

The component responsible for aneroid movement in the Vertical Speed Indicator (VSI) is the expansion and contraction of the aneroid. An aneroid is a sealed metal chamber that responds to changes in atmospheric pressure. In the VSI, this chamber expands or contracts when there are changes in static air pressure, which reflects the upward or downward movement of the aircraft.

As the aircraft climbs, the ambient air pressure decreases, causing the aneroid to expand, which results in a needle movement on the VSI indicating a climb. Conversely, when the aircraft descends, the internal pressure of the aneroid decreases, leading to contraction and showing a descent on the indicator. This mechanism effectively translates the rate of pressure change into a visual indication of vertical speed, making it essential for pilots to understand their altitude changes relative to the surrounding atmosphere.

The other components mentioned, like pressure changes from the pitot tube and static air pressure, do play roles in various instruments but do not directly affect the aneroid's mechanism in the VSI. The flexible diaphragm is a part of other instruments, such as the altimeter, but it is not the main component responsible for the VSI's operation.