What is the primary function of a pitot tube in aviation instruments?

The primary function of a pitot tube in aviation instruments is to measure airspeed. The design of the pitot tube allows it to capture dynamic pressure from the airflow as the aircraft moves forward. This dynamic pressure is used to calculate the airspeed of the aircraft by comparing it with the static pressure measured simultaneously through a separate static port.

When the aircraft is in motion, the air enters the pitot tube and exerts pressure on the inside of the tube. This pressure, known as stagnation pressure, is a combination of the static pressure of the air and the dynamic pressure due to the aircraft's speed. By measuring this stagnation pressure and subtracting the static pressure, pilots and instruments can derive the true airspeed of the aircraft. This information is crucial for pilot awareness regarding operational limits, calculating fuel consumption, and determining performance during takeoff and landing.

While pitot tubes are critical in measuring airspeed, they do not measure altitude directly, determine density, or sense static pressure independently. Instead, static pressure is typically sensed using a static port separate from the pitot tube, which allows for accurate altitude readings. Thus, the function of the pitot tube primarily revolves around its capability to measure the aircraft's airspeed effectively.