Book 23, Question 54
How Does an Altimeter Know How High a Plane Is?
How does an airplane know how high it is? It feels the air! The tool is called an altimeter. Air pressure drops by about half at eighteen thousand feet.
More fun facts
- An altimeter is a very sensitive barometer, a tool that measures air pressure.
- Air pressure drops fairly quickly as you go higher.
- So the altimeter can turn the air pressure around the plane into a height.
- Inside is a stack of sealed metal wafers that swell or squeeze as the pressure changes.
- The altimeter is the only instrument that can show a plane's altitude, so it is one of the most important.
- Pilots set the altimeter to match the local air pressure so it reads correctly.
Sources: faa.gov
Questions kids ask
What does an altimeter measure from?
It measures the plane's height above a set air pressure level.