If the ram air input to the pitot head is blocked by ice, how will the airspeed indicator react?

When the ram air input to the pitot head is blocked by ice, the airspeed indicator will drop to zero. This occurs because the pitot tube measures dynamic pressure, which is derived from the difference between ram air pressure and static air pressure. If the ram air input is blocked, no new air pressure is sensed, and the indicator can no longer read the dynamic pressure necessary to provide an accurate speed reading.

In flight, as the aircraft moves through the air, the ram air pressure should normally increase, allowing the airspeed indicator to function correctly. However, with the blockage, the instrument no longer receives this vital information, causing the airspeed reading to reflect a value of zero, regardless of the true airspeed of the aircraft. This is crucial for pilots and dispatchers to understand, as a zero reading could lead to incorrect assumptions about the aircraft's speed and performance, especially in critical situations like takeoff and landing.

This knowledge highlights the importance of monitoring and maintaining pitot tubes and understanding how blockages affect airspeed readings in flight operations.