What is VLV on Boeing 737? (Valve)

The Boeing 737 is a popular and widely-used aircraft in the aviation industry. It is known for its reliability, efficiency, and versatility. One of the crucial components that contribute to the safe operation of the Boeing 737 is the valve system. Valves, abbreviated as VLV, play a vital role in various systems of the aircraft, ensuring proper control and movement of fluids or gases. In this article, we will explore the significance of valves on the Boeing 737 and their functions in different systems.

Valve Functions in the Boeing 737

The valve system in the Boeing 737 is responsible for regulating, directing, and controlling the flow of fluids or gases in different systems of the aircraft. Let’s take a closer look at some of the essential functions of valves:

1. Fuel System

The fuel system of the Boeing 737 relies on the proper functioning of valves to deliver fuel to the engines efficiently. The fuel control valves, also known as fuel metering units, regulate the amount of fuel supplied to the engines based on the pilot’s inputs and engine parameters.

Another critical valve in the fuel system is the fuel shutoff valve, which helps in isolating the fuel flow to the engines during emergencies or when the engines are shut down. This valve is typically controlled by the pilots or the aircraft’s automated systems.

2. Hydraulic System

The hydraulic system on the Boeing 737 powers various crucial components, such as the flight control surfaces, landing gear, and thrust reversers. Valves in the hydraulic system play a crucial role in controlling the pressure and flow of hydraulic fluid, allowing for smooth and precise operation of these components.

A prominent valve in the hydraulic system of the Boeing 737 is the hydraulic control valve, which regulates the flow of hydraulic fluid to different parts of the aircraft. This valve ensures that the hydraulic power is directed accurately and efficiently to where it is needed.

3. Pneumatic System

The pneumatic system of the Boeing 737 provides air pressure for various functions, including engine starting, air conditioning, and anti-ice systems. Valves in the pneumatic system aid in maintaining the desired air pressure, routing air to the appropriate systems, and preventing excessive pressure.

One of the essential valves in the pneumatic system is the cabin pressure relief valve, which regulates the cabin pressure and helps prevent excessive pressure differentials between the cabin and the outside atmosphere. This valve ensures the comfort and safety of passengers and crew by maintaining the appropriate cabin altitude.

Valve Types and Control

Valves used in the Boeing 737 can vary depending on their specific functions and the systems they are a part of. Some commonly used valve types in the aircraft include:

1. Check Valves

Check valves are used in the Boeing 737 to allow the flow of fluids or gases in one direction while preventing backflow in the opposite direction. These valves help maintain desired pressure levels and prevent system failures or malfunctions.

For example, check valves are essential in the fuel system to ensure that fuel flows only in the intended direction, preventing fuel starvation or leakage. Similarly, in the pneumatic system, check valves control the airflow to maintain desired pressure levels.

2. Solenoid Valves

Solenoid valves are electromechanical devices that use an electric current to control the movement of a valve mechanism. These valves are commonly used in the Boeing 737 for various functions, including fuel system control and pneumatic system operations.

For instance, solenoid valves play a crucial role in the automatic shutdown of the fuel flow to the engines during emergencies. They can also be used to control pneumatic valves, allowing for precise and efficient regulation of air pressure in different systems.

3. Pressure Relief Valves

Pressure relief valves are designed to limit and release excess pressure from a system. These valves are essential for maintaining safe operating pressures and preventing the buildup of excessive pressure that could lead to system failures or damage.

In the Boeing 737, pressure relief valves are commonly used in the fuel system, hydraulic system, and pneumatic system to prevent overpressurization. They provide an essential safety mechanism to protect the aircraft and its systems from potential damage.


The valve system, abbreviated as VLV, is a critical component of the Boeing 737 aircraft. Valves are responsible for regulating the flow of fluids or gases in various systems, including the fuel, hydraulic, and pneumatic systems. By controlling the movement of these essential substances, valves contribute to the safe and efficient operation of the aircraft.

For More: What is TGT on Boeing 737? (Turbine Gas Temperature)