Testing the A350F’s cargo loading and main deck door actuation systems

For the new A350F now taking shape, building a next-generation freighter is about much more than simply removing passenger seats. Its wings and engines are only half the equation; the operational heart of the aircraft lies in its ability to secure and protect up to 111 tonnes of payload. By testing the Main-Deck Cargo Door (MDCD) actuation system and the Cargo Loading System (CLS) on large physical test rigs, Airbus teams in Bremen, Germany, are turning the digital concepts into a certified reality.

Preparing the A350F’s operational readiness

Indeed, as the first flight and subsequent flight test campaign of the A350F draws closer later this year, these key components are being put through their paces: The “Cargo Door Actuation System System Integration Bench” (CDAS SIB), and “Cargo Zero” respectively, are already helping to achieve A350F certification readiness, industrial maturity, operational reliability – and of course to de-risk the flight test campaign. 

 

Overall the systems integration testing works toward aircraft-related milestones, with one of the first milestones being ‘power on the aircraft’ and to be ’ready for ground testing,’ followed by first flight clearance.

Testing the main-deck door: validating aircraft cargo door and actuation systems

Before describing the test rig operations, it is first worth appreciating that the A350 Family was from its very outset conceived as a 'more electric' aircraft. It made sense therefore that the new MDCD's opening/closing mechanism would be driven by electrical rather than hydraulic power. On the one hand it avoids the need for hydraulic fluid lines to the door and on the other hand it minimises the required space envelope thanks to Geared Rotary Actuators capable of opening or closing the door within 60 seconds and even operating it in a 40kt wind!

Furthermore, the mechanism to latch the door is completely new, and is based on an Airbus patent, used now for the first time on a freighter. The main benefits of that are savings in space, weight and cost, since the way of latching the door reduces the number of parts compared to current systems. The CDAS SIB is mainly dedicated to test these MDCD system components and their integration within the aircraft.

A 20-tonne demonstrator for the industry's largest cargo door 

The demonstrator comprises a frame weighing almost 20 tonnes on which the test door – which is made of metal but with equivalent stiffness, weight and center of gravity of the eventual carbon fibre composite door – will be operated in different configurations.

Essentially it is the ‘proving ground’ for the industry's largest cargo door (featuring a 170-inch wide clear opening) and its innovative all-electric drive. 

By repeatedly opening and closing the door under various simulated structural loads, the team validates the new electric actuators (which replace traditional hydraulics) and the patented latching systems (including the sensors, motors and software). Last year, the project achieved its first milestone of ‘marrying’ the bench with the test door in Bremen’s Test Centre.

From engineering tests to EASA certification 

Jürgen Ruckes, cargo and door testing leader notes: “While preparing for the handover, the teams are conducting in parallel ‘engineering tests’ to support the development of ground testing on the first aircraft. It will also address the systems integration aspects, specifically the door activation system. It will initially focus on clearing first-flight aspects and subsequently move onto the certification stream.”

“The door system itself is always shut off during flight, so the immediate goal is ensuring the system is locked and secured,” says Jürgen. “Later, the system must be shown to be compliant with airworthiness requirements for EASA certification. The results from the testing benches feed into the certification campaign.”

Inside the 'Cargo Zero' test rig

The ‘latest and greatest’ demonstrator in Bremen is known as “Cargo Zero”. Its ‘Zero’ designation means that the demonstrator is essentially one step before the first real aircraft – in this case the flight test aircraft, MSN700.

Cargo Zero is primarily used for testing cargo operations – including loading and unloading. It features a cut-out of the main deck cargo door, the cargo hold’s interior lining and also a fully working Cargo Loading System (CLS) with its control panels and electrical power-drive units (PDUs) in place.

The CLS built into the floor of a freighter aircraft. The most visible aspects are a network of mechanical rollers, electrical power-drive units (PDUs), latches, and advanced control panels that allow ground crews to seamlessly and precisely maneuver cargo pallets and containers into place.

The 24 metre long demonstrator is essentially a partial full-scale replica of the A350F cargo hold, consisting of both mechanical and electrical CLS components as well as some of the interfacing systems. By simulating extreme floor flex and floor-tilt angles, it also ensures that even the most demanding loads – from large turbofan engines to delicate electronics, as well as the heaviest ULDs (up to 28 tonnes) – can be maneuvered with precision.

Cargo Zero looks very similar to the real A350F: The floor is modelled on the aircraft's structure, with cross beams and the original roller tracks. The mechanical and electrical components of the CLS are installed on it with the aid of mixed reality tools (like HoloLens) to bridge virtual parts with the real-world frames: additional rails, floor panels, rollers and bolts. The control panels, which allow the loading crew to move the pallets and containers, are located on the walls.

Testing the Cargo Loading System under real-world operational scenarios
 

“The team working on the Cargo Zero is testing  the operation of the CLS, replicating operational scenarios experienced by customers,” explains Jürgen. “This includes testing how different loads are moved in or out, using different containers, and testing with varying container weights, including very heavy loads. They also test different aircraft attitudes, such as nose up or down.”

He adds: “A key specific test is the engine loading test [using a representatively large wooden engine mockup on a pallet], requested by customers to ensure that in real life large turbofan engines would be easily and automatically transported in and out of the aircraft while mounted on their dedicated engine stand.”

Jürgen points out that the team in Bremen recently conducted a rescue test campaign to determine the accessibility of the cargo area and how personnel can carry an individual experiencing a medical event from the cargo area to the courier area behind the cockpit.

“To facilitate such tests, the demonstrator includes mockups of seats and other relevant elements, with accurate measurement clearances,” he notes.

Official testing with Cargo Zero has been running since mid March, following the first power-on tests which were just completed at the time of writing.

Other topics related to normal and abnormal CLS test conditions or maturity items will continue this year and during 2027. Beyond the initial phase, the team plans to offer customer slots for specific testing, training, or simulating operational scenarios relevant to how customers operate the aircraft.

Additionally, Cargo Zero is used to test the Tail Tipping Warning System. This innovation prevents the aircraft from tipping backwards in case of ‘abuse loading’ (ie. heavily loaded at the rear and too light at the front) in adverse conditions (such as a headwind; or snow on the horizontal tailplane).