Definition
A precisely sized small opening engineered to allow air to pass through at a specific, controlled rate. In the Vertical Speed Indicator (VSI), a calibrated orifice creates a deliberate, metered leak between the instrument case and the static pressure source so that pressure inside the case lags behind outside pressure during a climb or descent, producing a measurable rate of change.
Plain English
A small hole made to an exact size so that air can only flow through it at a known, steady rate. It acts like a controlled leak that slows pressure changes down in a predictable way.
Context Anchor
Seen in discussions of how a vertical speed indicator works and why it has a slight delay when showing climbs or descents.
Derivation
Calibrated comes from Latin roots meaning to set to a precise standard. Orifice comes from Latin oris (mouth) and facere (to make), meaning a small opening. Together: a small opening sized to a precise standard. This helps because it tells you the hole is not just any hole — its exact size is the whole point.
Why Pilots Care
It ensures the VSI displays an accurate rate of climb or descent rather than just showing pressure.
Analogy
It is like a very small, fixed opening in a container lid: air can still move through it, but only slowly and at a controlled rate.
Grounding Statement
The calibrated orifice creates a controlled delay in pressure change, and that delay is what lets the VSI show a rate of climb or descent.
Intuition Check
Calibrated does not mean the whole instrument is automatically accurate in every situation. Here it means the opening is a known, carefully chosen size so air passes through it at a controlled rate.
Example Sentence 1
The VSI senses vertical speed by comparing static pressure inside the case to the pressure bleeding through a calibrated orifice.
Example Sentence 2
A blocked calibrated orifice can cause the vertical speed indicator to lag or give false readings.