In the pitot-static system, which component senses ram air pressure?

• A. It uses cabin pressure sensors.
• B. Pitot tube senses ram air pressure; static ports sense atmospheric pressure.
• C. Pitot tube senses static pressure; static ports sense ram air pressure.
• D. It measures engine oil pressure.

Answer: (B)

The main idea is that the pitot-static system uses two pressure readings: ram (dynamic) pressure measured by the pitot tube, and static atmospheric pressure measured by the static ports. The airspeed indicator calculates airspeed from the difference between these two pressures.

The pitot tube is positioned to face into the oncoming airflow, so air is forced into it and its kinetic energy is converted into pressure—the stagnation or ram pressure. As speed increases, this ram pressure rises. The static ports are flush with the aircraft surface and sample the surrounding atmospheric pressure, which remains relatively constant for a given altitude, regardless of the aircraft’s speed.

Because the airspeed indicator relies on the difference between ram pressure and static pressure, the pitot tube provides the ram pressure reading, while the static ports provide the ambient pressure. The other options mix up these roles or refer to pressures unrelated to the pitot-static system (like engine oil pressure or cabin pressure).