What are signs of pitot-static blockage and your response?

• A. Inconsistent airspeed readings and erratic altimeter or VSI; use alternate air source and follow emergency instrument failure procedures.
• B. Consistent airspeed readings but altitude changes slowly.
• C. Only a fuel-flow anomaly.
• D. GPS failure indicates blockage.

Answer: (A)

Pitot-static blockage disrupts the instruments that rely on air pressure: the airspeed indicator from the pitot tube and the altimeter and vertical speed indicator from the static ports. If the pitot tube is blocked, the airspeed readings can become inconsistent, jump around, or go to zero. If the static port is blocked, the altimeter and VSI can behave erratically or freeze, since they rely on ambient pressure changes. When you see inconsistent airspeed along with erratic altitude or vertical speed indications, that pattern points to a blockage in the pitot-static system. The prudent response is to switch to the alternate air source to restore a reliable supply to the airspeed indicator and then follow the instrument failure/emergency procedures to maintain control and navigate safely. Other choices describe issues that aren’t tied to the pitot-static system—engine fuel anomalies or GPS failures—so they don’t fit the scenario of a pitot-static blockage.