What is the function of an 'altimeter'?

An altimeter functions by measuring the altitude of an aircraft through the assessment of atmospheric pressure. This device operates on the principle that atmospheric pressure decreases with an increase in altitude; as a plane ascends, the pressure outside the aircraft changes, and the altimeter uses this change to determine how high the aircraft is flying above sea level or ground level.

Every 1,000 feet of altitude corresponds to approximately a 1-inch change in atmospheric pressure. An altimeter is calibrated to understand these variations, allowing pilots to maintain safe flying altitudes and avoid terrain collisions.

The other options describe functions that are handled by different instruments on an aircraft, such as airspeed indicators for speed measurement, fuel flow indicators for fuel consumption, and various navigation systems for tracking and calculating distance traveled. Understanding the specific purpose of an altimeter is crucial for pilots and technicians to ensure accurate altitude readings, which are vital for safe flight operations.