What information does an altimeter provide to the pilot?

An altimeter is an essential instrument in an aircraft that measures the altitude of the aircraft above sea level. It operates primarily by comparing the atmospheric pressure at the aircraft's current altitude with a standard atmospheric pressure level. As the aircraft climbs or descends, the surrounding air pressure changes, and the altimeter reflects these pressure changes as altitude readings.

When the pilot checks the altimeter, they receive crucial information that helps them maintain the proper flight level and avoid obstacles or terrain. This altitude data is typically referenced to mean sea level (MSL), which is a standard benchmark for navigational purposes. Therefore, the altimeter's primary function is indeed to provide the altitude of the aircraft, making it indispensable for safe and effective flight operations.

The other options relate to different aspects of flight instrumentation: airspeed is measured by aairspeed indicator, the rate of climb is indicated by a vertical speed indicator, and heading direction is provided by a heading indicator or compass. Each of these instruments serves a unique purpose distinct from that of the altimeter.