Final answer:
If the pitot system is blocked by ice, a pilot will experience inaccurate airspeed readings, which can pose a serious flight safety risk. The blockage can cause the airspeed indicator to become static or drop to zero. Pilots are trained to handle such situations by using pitot heat or changing altitude to clear the blockage.
Step-by-step explanation:
If the pitot system ram air input and drain hole are blocked by ice, a pilot can expect inaccurate airspeed readings, which can be a serious hazard during flight. The pitot system measures the dynamic pressure of the air flowing into the pitot tube, which is then used to calculate the true airspeed of the aircraft. If ice blocks the ram air input the system can't measure dynamic pressure correctly.
In some cases, if only the ram air input is obstructed while the drain hole remains clear, the pitot tube might still function as a form of simple pressure chamber, providing some airspeed information that reacts slowly to changes in actual speed. However, both blockages will result in the airspeed indicator to remain static at the speed at which the blockage occurred, or it may drop to zero, depending on whether the blockage is complete or partial, respectively.
Pilots are trained to recognize and handle such malfunctions. Procedures may include attempting to melt the ice by using pitot heat or by changing altitude to an area with a warmer temperature. These steps are critical since incorrect airspeed information could lead to a stall or other unsafe flying conditions.