What occurs to the Airspeed Indicator (ASI) if the Pitot tube opening and drain hole are blocked while the static port is open?

When the Pitot tube opening and drain hole are blocked while the static port remains open, the airspeed indicator will freeze at its current reading. This phenomenon occurs because the airspeed indicator operates based on the pressure differential between the static pressure (from the static port) and the dynamic pressure (from the Pitot tube).

The Pitot tube collects dynamic pressure, which is dependent on the airflow into the tube. If the opening of the Pitot tube is blocked, it cannot sense any changes in dynamic pressure. Consequently, as the aircraft ascends or descends, the static pressure may change, but the lack of airflow into the blocked Pitot tube means the dynamic pressure remains unchanged. As a result, the ASI cannot accurately reflect changes in airspeed and will display a reading that is ‘frozen’ at the last value recorded before the blockage occurred. This is why the correct answer reflects that the ASI will freeze at its current reading, illustrating the specific failure mode of the instrument in the context of blocked Pitot systems.

The other options describe different behaviors that would not occur under these circumstances, making the selection of the freezing behavior definitive in this situation.