If both the ram air input and drain hole of the pitot system become blocked, what will be the indication of airspeed?

When both the ram air input and the drain hole of a pitot system are blocked, the airspeed indicator loses its ability to read the dynamic pressure changes that occur with variations in airspeed and altitude. In this scenario, the airspeed indicator will not register any changes in indicated airspeed during level flight, because the static pressure inside the system is trapped, leading the indicator to reflect a constant value based on the air pressure at the time of the blockage.

In level flight, where altitude and speed remain constant, the airspeed reading will remain static because there are no changes in the air pressure affecting the indicator. The blocked ram air input prevents any new air from entering the system to reflect changes in speed, while the blocked drain hole prevents moisture from leaving, which could otherwise cause erroneous readings due to pressure buildup.

This situation differs from conditions where, for example, the airspeed would read zero or give erratic indications. When the plane climbs or in other flight conditions, the airspeed indicator's behavior would change if only one of the ports was blocked, but if both are blocked simultaneously in level flight, the indicated airspeed remains unchanged.