Which instruments rely on sensing ambient air pressure through the pitot-static system?

• A. Airspeed indicator, altimeter, and vertical speed indicator
• B. Attitude indicator and turn coordinator
• C. Magnetic compass
• D. Fuel gauge.

Answer: (A)

The key idea is that these three instruments get their readings from the pitot-static system, which measures ambient air pressure. The airspeed indicator uses the difference between ram (pitot) pressure and the static pressure to determine your speed relative to the air. The altimeter relies on static pressure to indicate altitude, since air pressure decreases with height. The vertical speed indicator tracks how static pressure changes over time to show how quickly you’re climbing or descending.

The other instruments don’t depend on this system. Attitude indicators and turn coordinators use Gyros powered by a vacuum system or electricity, not pitot-static pressures. The magnetic compass responds to Earth’s magnetic field, not air pressure. The fuel gauge measures fuel quantity with its own sensors, not ambient air pressure.