What is the primary function of an altimeter in an aircraft?

The primary function of an altimeter in an aircraft is to indicate the aircraft's altitude. An altimeter measures the atmospheric pressure outside the aircraft and converts this pressure into an altitude reading. As an airplane climbs to higher altitudes, air pressure decreases, and the altimeter reflects this change, allowing pilots to maintain the necessary altitude for safe flight operations. It is crucial for navigation and ensuring safe separation from terrain and other aircraft.

Understanding altitude is vital for various phases of flight, including takeoff, landing, and cruising. While the other functions listed, such as measuring speed or monitoring engine performance, are important for overall flight operation, they are not the primary role of the altimeter. The altimeter’s specific focus on altitude makes it a critical instrument for safe and effective piloting.