Which instrument continuously measures air pressure to determine altitude?

• A. Airspeed indicator
• B. Vertical speed indicator
• C. Barometric altimeter
• D. Tachometer

Answer: (C)

The barometric altimeter is the instrument that continuously measures air pressure to determine altitude. It works by sensing the ambient air pressure and comparing it to a predefined standard pressure level, which allows it to calculate how high the aircraft is flying above sea level. As altitude increases, air pressure decreases, and the altimeter uses this relationship to provide a readout of the aircraft's elevation.

In the context of aircraft instrumentation, the airspeed indicator measures the speed of the aircraft relative to the surrounding air, rather than altitude. The vertical speed indicator indicates the rate of climb or descent but does not measure altitude itself. The tachometer measures the rotational speed of the engine or propeller, which is also unrelated to altitude measurement.