What is FQPU on Boeing 737? (Fuel Quantity Processor Unit)

The Fuel Quantity Processor Unit, or FQPU, is a vital component of the Boeing 737-800 aircraft’s fuel system. It plays a crucial role in determining and monitoring the amount of fuel present in the aircraft’s fuel tanks. The FQPU collects data from various sensors and sends it to the central computer system, allowing pilots to accurately monitor fuel levels and make informed decisions during flight.

As the industry standard for narrow-body jetliners, the Boeing 737-800 is equipped with advanced fuel management systems to ensure efficiency, safety, and optimal performance. The Fuel Quantity Processor Unit is an integral part of this system, providing accurate fuel level information to the flight crew.

How does the Fuel Quantity Processor Unit work?

The Fuel Quantity Processor Unit is responsible for receiving electrical signals from various sensors installed in each fuel tank of the aircraft. These sensors measure the fluid level and temperature of the fuel. The FQPU then processes these signals and converts them into meaningful data that can be easily understood by the flight crew.

The FQPU employs redundant channels to ensure accuracy and reliability. This redundancy serves as a safety measure, providing a backup in case one channel fails or encounters errors. The system continuously monitors the signals from the sensors and performs various checks to detect any discrepancies or faults.

The processed data from the Fuel Quantity Processor Unit is displayed on the aircraft’s instrument panel, allowing the flight crew to monitor the fuel levels in real-time. This information is crucial for flight planning, including determining fuel load, calculating the remaining fuel during the flight, and making decisions regarding fuel transfers between tanks.

Importance of the Fuel Quantity Processor Unit

The Fuel Quantity Processor Unit is of utmost importance in ensuring the safe and efficient operation of the Boeing 737-800 aircraft. Accurate fuel level information is essential for flight crews to properly manage fuel consumption, avoid fuel shortages, and maintain the aircraft’s balance during flight.

By continuously monitoring the fuel levels, the Fuel Quantity Processor Unit helps prevent fuel-related incidents such as fuel exhaustion or fuel imbalance. These incidents can have severe consequences, including loss of control or unexpected engine shutdowns. The FQPU acts as a reliable source of information, enabling pilots to make informed decisions and react promptly to any abnormalities in the fuel system.

Additionally, the Fuel Quantity Processor Unit assists in detecting any potential faults or malfunctions within the fuel system. If the FQPU identifies discrepancies between the measured fuel levels and the expected values, it can trigger warnings or alerts, notifying the flight crew to investigate further and take necessary action. This early detection system helps ensure the overall safety of the aircraft and its passengers.

The Boeing 737-800 is renowned for its fuel efficiency, and the accurate monitoring provided by the Fuel Quantity Processor Unit contributes to this reputation. By precisely measuring the fuel levels, the aircraft can optimize its fuel consumption during flights, reducing costs and environmental impact. The FQPU also aids in weight and balance calculations, allowing the crew to distribute fuel evenly for stable and efficient flight operations.


The Fuel Quantity Processor Unit plays a vital role in the fuel management system of the Boeing 737-800. With its ability to accurately measure and monitor fuel levels, the FQPU ensures the safe and efficient operation of the aircraft. By providing real-time fuel information to the flight crew, it enables them to make informed decisions and take appropriate actions during flight.

As technology advances, the Fuel Quantity Processor Unit continues to evolve, incorporating more advanced features and capabilities. Pilots can rely on this crucial component to provide accurate and reliable fuel level data, contributing to the overall performance and success of the Boeing 737-800 aircraft.

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