If the pitot system ram air input and drain hole are blocked by ice, what will occur?

When the pitot system's ram air input and drain hole are blocked by ice, the airspeed indicator will experience a malfunction. The correct outcome is that the airspeed indicator may act as an altimeter. This occurs because the pitot tube, which normally allows outside air pressure to enter for accurate airspeed readings, becomes occluded. Consequently, the instrument no longer receives a fresh airflow pressure that would typically indicate changes in the aircraft's speed relative to the air.

As the aircraft climbs or descends, the ambient atmospheric pressure changes typically associated with these maneuvers would not be compensated for since the blocked pitot system fails to register the necessary dynamic pressure changes. Instead, the airspeed indicator will begin to reflect the static pressure changes due to altitude gain or loss, mimicking altimeter behavior rather than indicating true airspeed. Therefore, the instrument begins providing misleading information, and this phenomenon can critically impact situational awareness when flying.

Understanding this situation emphasizes the importance of regular checks on the pitot system to prevent such blockages from occurring, ensuring that flight safety is maintained.