Which instrument measures airspeed relative to surrounding air?

Which instrument measures airspeed relative to surrounding air?

• A. Altimeter
• B. Heading Indicator
• C. Airspeed Indicator
• D. Attitude Indicator

Answer: (C)

Airspeed is how fast the airplane moves through the air around it, so the instrument that measures that is the airspeed indicator. It uses the pitot-static system: a pitot tube faces forward to sense stagnation (dynamic) pressure as you fly, while static ports measure ambient pressure. The instrument compares the dynamic pressure to the static pressure and converts that difference into a reading of indicated airspeed. This reading reflects motion through the air, not the distance over the ground, and it changes with air density (altitude and temperature) because that affects the pressure relationship. For context, the altimeter uses static pressure to show altitude, the heading indicator shows direction relative to magnetic north, and the attitude indicator shows the aircraft's orientation to the horizon. But when you need to know how fast you’re moving through the air itself, the airspeed indicator is the correct instrument.

Airspeed is how fast the airplane moves through the air around it, so the instrument that measures that is the airspeed indicator. It uses the pitot-static system: a pitot tube faces forward to sense stagnation (dynamic) pressure as you fly, while static ports measure ambient pressure. The instrument compares the dynamic pressure to the static pressure and converts that difference into a reading of indicated airspeed. This reading reflects motion through the air, not the distance over the ground, and it changes with air density (altitude and temperature) because that affects the pressure relationship.

For context, the altimeter uses static pressure to show altitude, the heading indicator shows direction relative to magnetic north, and the attitude indicator shows the aircraft's orientation to the horizon. But when you need to know how fast you’re moving through the air itself, the airspeed indicator is the correct instrument.