What is PRSOV on Boeing 737? (Pressure Regulating Shut-Off Valve)

The Pressure Regulating Shut-Off Valve (PRSOV) plays a crucial role in the operation and safety of the Boeing 737 aircraft. As its name suggests, this valve regulates the pressure within the aircraft’s fuel system while also serving as a shut-off mechanism to prevent fuel leakage in case of emergencies. The PRSOV is designed to maintain a stable and optimal pressure level throughout the flight, ensuring a reliable fuel supply to the engines.

In this article, we will delve into the importance, function, and operation of the Pressure Regulating Shut-Off Valve on the Boeing 737 aircraft.

The Function of the Pressure Regulating Shut-Off Valve

The primary function of the Pressure Regulating Shut-Off Valve is to maintain a constant fuel pressure within the aircraft’s fuel system. This is crucial for the efficient operation of the engines, as they rely on a steady and regulated fuel flow. The valve achieves this by modulating the flow of fuel in response to fluctuations in pressure.

When the fuel pressure exceeds the desired level, the PRSOV partially closes, restricting the fuel flow and reducing the pressure. Conversely, if the fuel pressure drops below the desired level, the valve opens wider, allowing more fuel to flow and increasing the pressure. By continuously adjusting the fuel flow, the PRSOV ensures that the pressure remains within the specified range, thus optimizing engine performance.

In addition to its pressure-regulating function, the PRSOV also acts as a shut-off valve. In the event of an emergency or during maintenance procedures, the valve can be fully closed to isolate the fuel system and prevent fuel leakage. This feature enhances the safety of the aircraft by minimizing the risk of fire or other hazards associated with fuel leakage.

How Does the PRSOV Operate?

The Pressure Regulating Shut-Off Valve operates based on inputs from various sensors and control mechanisms within the aircraft’s fuel system. These sensors continuously monitor the fuel pressure and relay the information to the aircraft’s Engine Fuel Control System (EFCS). The EFCS, in turn, processes the data and sends signals to the PRSOV to adjust the fuel flow accordingly.

The PRSOV itself consists of several components, including a servo valve, an actuator, and a diaphragm. The servo valve receives the control signals from the EFCS and modulates the fuel flow by adjusting the position of the actuator. The diaphragm, connected to the servo valve, detects the pressure difference between the fuel system and the regulated pressure, allowing the valve to respond promptly to pressure fluctuations.

It is important to note that the PRSOV is a fail-safe system, designed to prioritize safety in case of malfunctions or power loss. In the event of a failure or loss of electrical power, the valve automatically closes to prevent any potential leaks or pressure instability. This ensures that even in unforeseen circumstances, the aircraft remains safe and under control.

The Importance of the PRSOV in the Boeing 737

The Pressure Regulating Shut-Off Valve is a critical component of the Boeing 737 aircraft, ensuring the reliable and efficient operation of its engines. By maintaining a stable fuel pressure, the PRSOV optimizes engine performance and fuel efficiency, ultimately enhancing the aircraft’s overall performance.

The shut-off feature of the PRSOV also contributes to the safety of the aircraft. In the event of emergencies such as engine fires or fuel leaks, the valve can quickly and effectively isolate the fuel system, minimizing the risks associated with such incidents. This capability significantly enhances the safety of passengers and crew on board the Boeing 737.

It is worth noting that the design and functionality of the PRSOV may vary between different aircraft models and generations. Therefore, it is essential for pilots, maintenance crews, and engineers to familiarize themselves with the specific PRSOV configuration and operating procedures of the Boeing 737 variant they are working with.


The Pressure Regulating Shut-Off Valve (PRSOV) plays a vital role in the operation and safety of the Boeing 737 aircraft. It maintains a constant fuel pressure to optimize engine performance while also serving as a shut-off mechanism in emergencies. By understanding the function and operation of the PRSOV, aviation professionals can ensure the efficient and safe operation of the Boeing 737.

For more information on the Boeing 737 and its systems, you can visit the Boeing official website.

For More: What is ADS on Boeing 737? (Air Data Systems)