What is the function of the altimeter in a Cessna 172?

The primary function of the altimeter in a Cessna 172 is to show aircraft altitude. The altimeter measures the atmospheric pressure outside the aircraft and translates this pressure into an altitude reading. As altitude increases, air pressure decreases; the altimeter utilizes this relationship to provide a reading of the aircraft's height above sea level. This is crucial for maintaining safe flight levels, navigating airspace, and ensuring proper separation from terrain and other aircraft.

When pilots adjust the altimeter setting to match the current local barometric pressure, they ensure accuracy in altitude reporting, which is essential for safe operations, especially near airports and in controlled airspace. Other functions such as indicating airspeed, calculating vertical speed, or determining heading are performed by different instruments, such as the airspeed indicator, VSI (vertical speed indicator), and the magnetic compass or directional gyro, respectively.