What airspeed indication can be expected if both the ram air input and drain hole of the pitot system are blocked by ice?

When both the ram air input and the drain hole of the pitot system are blocked, the airspeed indicator will read an incorrect value. The key factor here is that the system effectively becomes isolated from any dynamic changes in atmospheric pressure, leading to specific behavior of the indicated airspeed during flight.

In level flight, if a power change is made, the aircraft's speed may change, but because the pitot system is blocked, the airspeed indicator does not reflect those changes. The instrument relies on the difference between static and dynamic pressure to provide accurate readings, and with the blockage, it cannot register the actual increase or decrease in airflow or aircraft speed. Thus, the indicated airspeed will remain constant, effectively giving the pilot a false sense of stability and leading to potentially dangerous situations if the actual airspeed significantly changes due to variations in flight conditions.

This scenario emphasizes the importance of understanding pitot-static system functionality and the implications of ice blockage, as pilots would misinterpret the constant indication as a normal operational norm while the aircraft might be experiencing significant changes in performance.