Which instrument reads the aircraft's height above sea level by sensing atmospheric pressure?

• A. Airspeed Indicator
• B. Altimeter
• C. Attitude Indicator
• D. Vertical Speed Indicator

Answer: (B)

The instrument that reads the aircraft’s height above sea level by sensing atmospheric pressure is the altimeter. It measures the ambient static pressure from the atmosphere and converts that pressure into an altitude using the standard atmosphere model. By adjusting the Kollsman window to the local sea‑level pressure (QNH), the readout becomes altitude above mean sea level. If the local pressure isn’t set correctly, the reading can shift, showing a different reference height (such as pressure altitude). This is distinct from the other instruments: one measures how fast air is moving relative to the aircraft using dynamic pressure, another shows the aircraft’s orientation relative to the horizon, and the last indicates vertical speed by tracking how quickly pressure changes.