Which pitot-static instruments would be affected by a static system malfunction?

• A. Altimeter only
• B. Airspeed indicator only
• C. Vertical speed indicator only
• D. All three

Answer: (D)

The static system provides the ambient air pressure that several instruments rely on. The altimeter uses static pressure to indicate altitude, the vertical speed indicator uses changes in static pressure to show climb or descent rate, and the airspeed indicator uses a combination: it compares the pitot (dynamic) pressure to the static pressure to display airspeed. If the static system malfunctions—due to a blockage, leak, or other fault—the static pressure feeding all three instruments becomes erroneous or unchanging. As a result, the altimeter can read the wrong altitude, the vertical speed indicator can show an incorrect rate of climb or descent, and the airspeed indicator can display an incorrect speed. Because all three rely on the static pressure, a static system problem affects all of them.