Which flight instrument is affected if the pitot tube becomes clogged with ice during flight?

The airspeed indicator relies on the pressure differences measured by the pitot tube to determine the speed of the aircraft through the air. When the pitot tube becomes clogged with ice, it cannot accurately measure the dynamic pressure, which is essential for calculating airspeed. This results in the airspeed indicator providing faulty readings or potentially becoming completely inoperative. Understanding that the airspeed indicator reflects the relationship between static and dynamic pressure highlights why the blockage of the pitot tube directly impacts this instrument. The other instruments do not rely on this type of measurement; hence, they remain unaffected by the ice blockage in the pitot tube.