What is the primary function of Pitot tubes on an aircraft?

The primary function of Pitot tubes on an aircraft is to sense ram air pressure, which is crucial for the operation of airspeed indicators. These tubes are typically mounted on the exterior of the aircraft and face forward, allowing them to capture the air that enters as the aircraft moves. This captured "ram air" pressure is essential for calculating the dynamic pressure, which ultimately allows pilots to determine the aircraft's airspeed.

Airspeed indicators compare the pressure sensed by the Pitot tube to that of the static pressure from the environment, enabling the instrument to display the speed at which the aircraft is traveling through the air. Thus, the role of Pitot tubes directly relates to the measurement of airspeed, making this function vital for safe and effective flight operations.

The other options do not align with the primary functionality of Pitot tubes; for example, atmospheric pressure measurement pertains to barometric devices and aircraft altitude indication, which involves a different set of instruments, while roll and pitch commands are handled by the aircraft's flight control systems and are not related to Pitot tubes.