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For the validation of loads and aeroelastic simulations of a high altitude platform (HAP) in-flight, load measurements are very helpful. One technique to obtain load measurements is to apply strain gages to the primary structure. A calibration procedure enables the reconstruction of the loads from the measured strains. To reduce the risks, gain confidence and establish a feasible measurement set-up, a pre-test based on a CFRP wing segment is performed. This paper presents the theoretical background and the set-up of the measurement equipment. The results of the calibration from three different test cases are presented, showing an excellent agreement between applied and reconstructed loading with a deviation of less than or equal to ±1.0N and less than or equal to ±2.0cm for the location. Finally, the strains measured in the experiment are compared with the simulation, showing that a prediction of the strains is possible within a range of less than or equal to ±8%.

International audience; After the completion of the Airbus A350 XWB 900 Ground Vibration Test (GVT) in 2013 and the A320 NEO GVT in July 2014, the ONERA-DLR joined team performed the GVT of the new BelugaXL aircraft in May-June 2018. The test was completed in 8 measurement days for 2 mass configurations, thanks to efficient methods and tools. The originality of this structure comes from its very large fuselage and its rear section with two large additional vertical planes, which made the modal identification particularly challenging. This paper describes the process followed, the methods used, and the interactions with engineers in charge of aeroelastic computations during the test, and how they allowed the success of this campaign.; Après les essais de vibrations au sol de l'Airbus A350 XWB 900 en 2013 et de l'Airbus A320 NEO en juillet 2014, l'équipe commune ONERA-DLR a réalisé l'essai du nouvel avion d'Airbus, le Beluga XL, en mai-juin 2018. Le test fut effectué en 8 journées de mesure pour 2 configurations massiques, grâce à des outils et des méthodes efficaces. L'originalité de cette structure réside en la présence d'un fuselage de très grande dimension et d'une partie arrière comportant deux grands plans verticaux additionnels, ce qui rend l'identification modale particulièrement difficile. Cette communication décrit le procédé suivi, les méthodes utilisées et les interactions avec les ingénieurs en charge des calculs aéroélastiques durant le test, et comment ils ont permis le succès de cette campagne d'essais.

HALO (High Altitude and Long Range Research Aircraft), the atmospheric research aircraft of the German Aerospace Center (DLR), can be equipped with under-wing stores at different wing positions to transport scientific instruments for atmospheric research. The particle measurement system (PMS) carrier is such an external store which can carry three instruments at the same time per wing. Any modifications on an aircraft must be tested numerically and experimentally to ensure the structural integrity of the aircraft for all flight conditions. Load and flutter analyses can be validated with flight test data. For flight test, the aircraft and the under-wing stores of HALO must be equipped with acceleration and strain sensors. To reduce flight test time it is necessary to make quick decisions during the flight test. Therefore the DLR Institute of Aeroelasticity in Göttingen has developed a real-time analysis procedure for online identification of modal parameters like eigenfrequencies, damping ratios and mode shapes. These parameters vary with flight conditions and are necessary to analyse the aeroelastic stability of the system. The department of loads analysis and aeroelastic design and the department of structural dynamics and system identification have tested the newly developed procedure in 14 flight hours on the HALO. A network of three distributed data acquisition modules enabled the recording of the flight test instrumentation with 51 accelerometers and 16 strain gauge bridges. The measured data were distributed online on several computers where the newly developed software was implemented, allowing an instantaneous analysis of the structural dynamics behaviour and loads in flight. This paper provides an overview of the conducted flight vibration tests with HALO. It also shows the capability of the newly developed online monitoring system for aeroelastic identification.

The design of a highly instrumented, double-swept CFRP wind tunnel model and its experimental setup are presented. A forced sinusoidal pitching motion is applied to the one-sided clamped helicopter rotor blade tip. Challenges of the structural design and the manufacturing process are addressed. A mold with inserts to check the leak-tightness of the pressure transducers and retain the half shells in the mold is presented. Insights in the finite element analysis (FEA) of the blade tip model are given. The strength analysis reveals peak stresses in the adhesive and the spar. The finite element model is validated with an experimental modal analysis. The experimental and numerical mode shapes and eigenfrequencies show an excellent agreement. The design goal of a very stiff lightweight model is met with the first eigenfrequency at 70 Hz. The results of the fluid-structure interaction simulation at Ma=0.4 show no significant differences for the global forces compared to the simulations with the rigid contour. However, the maximum tip deformation is up to 20 mm and a slight excitation of the first bending mode can be observed.