In the event that both the ram and drain are blocked, how does the airspeed indicator behave?

When both the ram and drain ports are blocked, the airspeed indicator behaves like an altimeter because it relies on the difference between the static pressure and the dynamic pressure to measure airspeed. With both ports blocked, the airspeed indicator can no longer measure changes in dynamic pressure, as there are no variations in ambient air pressure to compare against. As the aircraft climbs or descends, the static pressure changes, which causes the trapped static pressure in the instrument to act similarly to how an altimeter functions; it will show a reading based on the current static pressure rather than a true measure of airspeed. Consequently, the airspeed indicator will respond to changes in altitude instead of changes in speed. This characteristic is crucial for pilots to understand, as it highlights the importance of ensuring that static and ram air systems are functioning properly for accurate airspeed readings.