What primary information does the altimeter provide?

• A. Indicated altitude above mean sea level (AMSL), based on ambient pressure
• B. Indicated airspeed
• C. Vertical speed
• D. Ground speed

Answer: (A)

Altitude information is what the altimeter provides. It senses the ambient static pressure around the aircraft, and because air pressure falls as you climb, the instrument uses that pressure with the standard atmosphere model to display an altitude. When you set the local sea‑level pressure (QNH), the reading corresponds to your indicated altitude above mean sea level. This is different from other flight readings such as airspeed (which uses dynamic pressure), vertical speed (rate of climb or descent), or ground speed (speed over the ground).