Definition
A small, precisely sized opening built into a pneumatic instrument or system that allows air to escape or enter at a known, controlled rate. In gyroscopic instruments such as the turn coordinator, a calibrated leak meters the airflow that drives or returns from the gyro, ensuring it spins at the correct speed.
Plain English
A tiny hole made to an exact size so that air flows through it at a specific, predictable rate — not too fast, not too slow.
Context Anchor
Seen in the pitot-static instrument section when learning how the vertical speed indicator shows climb or descent rate.
Derivation
‘Calibrated’ comes from the Latin idea of measuring against a standard — the same root as ‘calibre’ (the precise diameter of a gun barrel). A ‘calibrated’ leak is therefore a leak that has been deliberately sized to a known measurement, not an accidental or random one.
Why Pilots Care
Maintains accurate rate-of-climb and descent indications by allowing static pressure to equalize at a predictable rate inside the instruments.
Grounding Statement
The calibrated leak makes the instrument case catch up to changing outside air pressure slowly instead of all at once.
Intuition Check
Do not read “leak” here as damage or a fault. In this context, a calibrated leak is an intentional, carefully sized opening that makes the instrument work.
Example Sentence 1
The turn coordinator relies on a calibrated leak to regulate the airflow driving its gyro at the correct speed.
Example Sentence 2
During preflight, the pilot confirmed the calibrated leak in the static line was unobstructed so the instruments would read correctly.