Fibre optics put to the test for Airbus A400M

Fibre optics put to the test for Airbus A400MAs the new super airlifter for the 21st century, the A400M has been designed to fulfil multiple operational goals and to set new benchmarks for performance expectations. In its role as a dual airlifter and tactical fuel tanker for in-flight refuelling, verifying the accuracy and reliability of the fuel management system is critical.

That is why, as specialists in fibre-optic connectors and cables for harsh environments, Acal BFi were asked to adapt and re-work the custom Airbus test rigs after a critical connector in the fuel system was upgraded.

Airbus A400M – airlifter for the 21st century

The new A400M Airbus is the successor to the C-130 Hercules and C-160 Transall military airlifters. As a modern, multi-role military aircraft, the A400M is designed to bring new and more flexible capabilities to airlift operations and to deliver on challenging performance target. The result is an airlifter which doubles the payload of the aircraft that it is replacing and delivers an extended reach, fast response times as well as a more agile, role-changing capability.

For strategic missions, the A400M must achieve a high cruise speed for long-range flights; during tactical missions, however, the A400M must operate effectively at low speed and low level, despite rough, short or soft-field conditions. An in-flight re-fuelling capability also gives the A400M the ability to operate as a tactical tanker, giving an additional dimension to its multi-function role.

Computerised fuel management system

Accurate monitoring of fuel levels is crucial to support the A400M in both long-range and short-range operations as well as whilst dispensing or receiving fuel during in-flight re-fuelling. The A400M’s fuel load is contained in a main fuel tank, and also in two, optional cargo-hold fuel tanks (CHT), which connect into the aircraft's computer-controlled centralised fuel-management system. The fuel quantity management system (FQMS) uses fibre-optic connectors for reliable transmission of crucial information on fuel levels in the on-board tanks and on the air-to-air refuelling pods.

The A400M’s FQMS harnesses connect to the wing root end and power all six tank-wall processors. In-tank harnesses, attached to each processor, are fitted with probes which monitor data on capacitance, resistance, humidity and density, which is fed back to the wing data recorder via fibre-optic cables.

Regular testing, using custom test rigs, is essential to ensure that the computerised fuel management system continues to function correctly by measuring the return loss, insertion loss and signal integrity of fibre-optic network in the wings. So, when Airbus changed the connector on the wing root end of the fuel system, they asked Acal BFi to re-work the custom test rigs with a new, compatible connector. This, in turn, required replacement fibre-optic cabling which would be compatible with the new connector. Acal BFi adapted the existing test rigs using ruggedised fibre-optic connectors, linked via 62.5/125μm multimode cable, to ensure a high optical performance. Acal BFi’s expertise in fibre-optic technologies for harsh and mission-critical applications, allowed them to suggest a suitable combination of connector and cabling, whilst their fully equipped cable-assembly production facility, allowed in-house re-working of the existing test rigs.


Designed to fulfil a demanding double role as an air transporter and air-to-air re-fuelling aircraft, the A400M relies on fibre-optic cabling and connectors to monitor fuel levels during flight and in-flight refuelling. By adapting the existing custom test rigs with new fibre-optic connectors and cabling, and re-working the rigs in-house, Acal BFi are helping to ensure robust reliability for these mission-critical systems.

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