What is FQIS in Aviation? (Fuel Quantity Indication System)

The Fuel Quantity Indication System (FQIS) is a crucial component of aircraft fuel management. It provides accurate measurements of the amount of fuel in an aircraft’s tanks, allowing pilots and other crew members to monitor the fuel levels and make informed decisions about refueling. By ensuring that there is a sufficient amount of fuel on board, the FQIS plays a vital role in flight safety and efficiency.

The Importance of Fuel Quantity Indication System

The Fuel Quantity Indication System is an essential part of aviation for several reasons:

  • Flight Safety: Accurate fuel quantity measurement is crucial for flight safety. Pilots need to know how much fuel is on board to plan flight routes, make decisions on fuel stops, and ensure they have sufficient fuel for emergencies.
  • Fuel Efficiency: The FQIS allows pilots to optimize fuel usage, minimizing unnecessary weight and reducing fuel consumption. This not only saves costs but also reduces the environmental impact of aviation.
  • Operational Cost Reduction: Efficient fuel management facilitated by the FQIS can lead to significant cost savings for airlines. By accurately monitoring fuel levels, airlines can avoid overstocking fuel, optimize refueling processes, and minimize fuel losses.

The Components of Fuel Quantity Indication System

The Fuel Quantity Indication System consists of several components that work together to provide accurate fuel measurements:

Fuel Probes

Fuel probes are sensors located inside the fuel tanks of an aircraft. They are designed to measure the fuel level by detecting the electrical capacitance of the fuel in the tank. The capacitance changes as the fuel level varies, and the fuel probe converts these changes into electrical signals that are transmitted to the Fuel Quantity Indication System.

The system typically consists of multiple fuel probes installed in different tanks to provide accurate readings for each tank individually. This ensures that the pilots can monitor fuel levels and distribution throughout the aircraft.


Transmitters are responsible for sending the electrical signals from the fuel probes to the Fuel Quantity Indication System. These signals are transmitted through wiring or a wireless network, depending on the aircraft’s specifications. The transmitters ensure that the information regarding fuel levels is accurately relayed to the cockpit for monitoring and decision-making.

Fuel Quantity Indicator

The Fuel Quantity Indicator is the display unit in the cockpit that provides the pilots with real-time information about the fuel levels. It uses the incoming electrical signals from the transmitters to calculate and display the fuel quantity in each tank. The indicator is usually designed with multiple gauges or digital displays for easy monitoring and interpretation by the pilots.

In modern aircraft, the Fuel Quantity Indicator may also be integrated into the aircraft’s overall avionics system, allowing for more advanced features such as automated fuel management and data recording.


The Fuel Quantity Indication System is a vital component of aircraft fuel management, ensuring flight safety, fuel efficiency, and operational cost reduction. By accurately measuring fuel levels and providing real-time information to the pilots, the FQIS plays a crucial role in the overall operation of an aircraft. With its various components working together seamlessly, the FQIS enables pilots to make informed decisions about fuel utilization, resulting in safer and more efficient flights.

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