Which instrument is specifically used to measure the aircraft's altitude?

• A. Vertical speed indicator
• B. Altimeter
• C. Airspeed indicator
• D. Heading indicator

Answer: (B)

The altimeter is the instrument specifically designed to measure an aircraft's altitude. It functions by sensing changes in atmospheric pressure as the aircraft ascends or descends. As altitude increases, air pressure decreases, and the altimeter translates this change into a corresponding altitude reading. This allows pilots to understand their vertical position relative to sea level or a chosen reference point.

The vertical speed indicator measures the rate of climb or descent, providing information about how quickly an aircraft is gaining or losing altitude, but it does not give the actual altitude. The airspeed indicator measures the speed of the aircraft relative to the surrounding air and is essential for flight safety but does not relate to altitude. The heading indicator shows the aircraft's direction or heading, which is important for navigation but unrelated to altitude measurement.