Calibrated orifice is a specific device used to delay pressure changes in which instrument?

• A. A valve that controls cabin pressure.
• B. A sensor that measures airspeed.
• C. A pipe that connects the engine intake.
• D. A hole of specific diameter used to delay the pressure change in a vertical speed indicator.

Answer: (D)

Calibrated orifice is used to delay pressure changes in a vertical speed indicator. In the VSI, a sensing chamber is exposed to static pressure, and air flows through a small, precisely sized hole. That restricted flow creates a time delay, so the pressure in the sensing chamber changes gradually rather than instantly as the outside pressure shifts with climb or descent. This smoothing lets the instrument respond to the rate of altitude change (feet per minute) rather than to momentary pressure fluctuations, giving a stable, readable indication of vertical speed. It isn’t applied to cabin pressure valves, airspeed sensors, or engine intake piping—the delay function is specific to producing a rate-of-change indication in the VSI.