If the static port is blocked, which instruments are affected?

• A. VSI, Airspeed Indicator, Altimeter
• B. Attitude Indicator, Heading Indicator
• C. Turn Coordinator only
• D. GPS Display

Answer: (A)

The static port supplies ambient air pressure to the pitot-static system, and the instruments that rely on that pressure are the altimeter, the vertical speed indicator (VSI), and the airspeed indicator. If the static port is blocked, the altimeter can’t sense changes in ambient pressure and may freeze or read incorrectly; the VSI measures the rate of pressure change, so it can stop moving or show a false rate; and the airspeed indicator uses dynamic pressure minus static pressure, so with static pressure blocked the indicated airspeed becomes unreliable. The attitude indicator and heading indicator are gyroscopic instruments powered by their own source (vacuum or electric) and don’t depend on static pressure, and the GPS display uses satellites, so they aren’t affected by a blocked static port.