Which instrument in aviation uses changes in ambient pressure to determine altitude?

Which instrument in aviation uses changes in ambient pressure to determine altitude?

• A. Airspeed indicator
• B. Altimeter
• C. Attitude indicator
• D. Turn coordinator

Answer: (B)

Altitude is determined from ambient air pressure, and the instrument that translates that pressure into a readout is the altimeter. It uses a sealed aneroid (pressure-sensing) capsule that expands or contracts with changes in the outside static pressure from the aircraft’s static system. As you climb and the air gets thinner, ambient pressure drops, the capsule changes shape, and the hands on the altimeter move to show a higher altitude. The altimeter has a setting window (Kollsman window) to input the sea-level pressure. With standard pressure set, the instrument indicates pressure altitude; with the local sea-level pressure (QNH) set, it shows altitude above mean sea level. Temperature differences can cause indicated altitude to differ from true altitude, so pilots may apply temperature corrections as needed. The other instruments rely on different physical principles: airspeed uses dynamic pressure from the pitot-static system, while attitude indicator and turn coordinator depend on gyros to show orientation and rate of turn.

Altitude is determined from ambient air pressure, and the instrument that translates that pressure into a readout is the altimeter. It uses a sealed aneroid (pressure-sensing) capsule that expands or contracts with changes in the outside static pressure from the aircraft’s static system. As you climb and the air gets thinner, ambient pressure drops, the capsule changes shape, and the hands on the altimeter move to show a higher altitude.

The altimeter has a setting window (Kollsman window) to input the sea-level pressure. With standard pressure set, the instrument indicates pressure altitude; with the local sea-level pressure (QNH) set, it shows altitude above mean sea level. Temperature differences can cause indicated altitude to differ from true altitude, so pilots may apply temperature corrections as needed.

The other instruments rely on different physical principles: airspeed uses dynamic pressure from the pitot-static system, while attitude indicator and turn coordinator depend on gyros to show orientation and rate of turn.