What is the function of the altimeter in an aircraft?

The primary function of the altimeter in an aircraft is to measure the altitude of the aircraft above sea level. This instrument is critical for pilots as it provides essential data regarding the aircraft's height during flight, which is crucial for maintaining safety, navigation, and compliance with air traffic regulations.

Altimeters operate based on changes in atmospheric pressure, utilizing the principle that atmospheric pressure decreases with an increase in altitude. By measuring the air pressure outside the aircraft and comparing it to standard pressure values, the altimeter can determine how high the aircraft is flying above sea level.

While atmospheric pressure is a component relevant to how the altimeter functions, the altimeter’s specific purpose is to indicate altitude rather than simply measure pressure. Unlike options that relate to speed or distance traveled, which are managed by other instruments in the aircraft, the altimeter focuses purely on providing altitude information.