Airbus has completed one of the key tests of its new A350F freighter, bringing the programme another step closer to its first flight. A three-day Ground Vibration Test (GVT) was carried out in Toulouse in June to assess how the aircraft’s structure responds to different dynamic loads.

The test is an important milestone in preparations for flight testing, as it allows Airbus to validate and further refine the computer models used to calculate the aircraft’s aeroelastic behaviour and dynamic loads.

“This validation is a key enabler for the first flight, providing the necessary evidence to complete the first step of aeroelastics model validation, which is essential for opening the aircraft’s flight envelope,” said Nicolas Lastere, Airbus loads and aeroelastics expert.

Preparations began several days before the test itself, with additional sensors, electrodynamic vibration exciters and data acquisition equipment installed on the aircraft. The A350F was also configured specifically for the test and accurately weighed.

During the GVT, the aircraft structure was deliberately exposed to controlled vibrations. Airbus used both external shakers and movements of the aircraft’s own flight control surfaces. Accelerometers recorded the structural response, allowing engineers to determine the actual dynamic characteristics of the wings, fuselage, engines and other parts of the aircraft.

Additional vibration exciters were attached to the wingtips, rear fuselage section and engines, while the aircraft’s control surfaces performed controlled sine sweeps across different frequency ranges.

“When the test was underway, the aircraft was excited by its own control surfaces through sine sweeps performed across different frequency bandwidths. In addition, shakers were connected to the airframe at the wingtips, on the rear fuselage cone and on the engines to complement the different types of excitation,” explained Fabien Ayme, Airbus aeroelastic testing expert.

Airbus also introduced a new approach to data collection for the A350F test. Information from the aircraft’s standard Flight Test Instrumentation was combined with data from additional autonomous sensors installed specifically for the GVT, helping to reduce test duration while increasing the amount of measurement data available.

The results were monitored in real time, while data processing was performed after each individual test run. Initial results were immediately passed to the design teams, allowing the remaining test programme to be adjusted where necessary.

According to Airbus, the results showed a very good correlation between the aircraft’s actual structural behaviour and the theoretical models developed beforehand.

The three-day test was the result of almost two years of preparation involving a wide range of Airbus teams, including final assembly, flight control systems, vibration testing, flight test instrumentation, tooling development, aeroelastics, and mass properties and quality specialists.

The GVT is only one of several tests being conducted on the first A350F. Extensive ground testing began earlier this year on the first aircraft on the final assembly line in Toulouse, while separate tests of the Main-Deck Cargo Door actuation system and Cargo Loading System were carried out in parallel in Bremen.

Following completion of the GVT, Airbus engineers are continuing detailed data analysis and final model tuning ahead of the start of the flight test campaign.

Among the most important tests still to come are the Flight Vibration Tests, commonly known as flutter tests, which are scheduled to take place during the first three months of the flight test programme. During these tests, the A350F will gradually be taken up to its maximum design dive speed and Mach number, VD/MD, in order to confirm structural stability at the outer limits of the flight envelope.

“By validating the aircraft’s structural dynamics on the ground, the GVT team has ensured that when the A350F finally takes to the skies, it does so with an aeroelastic model that has been rigorously tested, measured and quantified,” Ayme concluded.

Completion of the GVT therefore represents one of the final major ground-testing milestones before the A350F’s first flight and the start of its intensive flight certification campaign.