In-flight monitoring of aircraft wings
Reflectometry is an optical technique that allows the calculation of the shape of reflective surfaces based on the deformation of a predefined pattern. The measurement setup supports installation on aircraft wings without affecting its aerodynamic or structural characteristics. Geometric limitations of aircraft installation require reflection to be measured under a small angle. In the EU-funded project WING REFLECTOMETRY (In-flight monitoring of wing surface with quasi tangential reflectometry and shadow casting), researchers used an infrared flash system to overcome additional limitations. The laminar flow wings have specific curvature. Moreover, there is only limited space to integrate components such as cameras, controllers and illuminators. The latest developments in aircraft painting further challenge the application of reflectometry. The WING REFLECTOMETRY system capabilities were proven during two test campaigns. Furthermore, it was tested on a full-scale wing mock-up constructed to demonstrate that reflectometry is a viable solution. The resolution offered is significantly better than the required limit of 0.02 mm. Project members were able to measure tiny deformations using low-angle and quasi-tangential reflectometry, while surface steps were measured with digital photogrammetry on casted shadows. The combination of both methods allowed in-flight measurements without influencing the aerodynamic characteristics of the wing. Specifically, researchers first assured the feasibility of measuring local deformations on the wing surface using reflectometry and a static reference pattern. For the validation of data analysis software and hardware architecture, tests on the laboratory setup followed additional ones on the wing mock-up. The wing mock-up allowed the WING REFLECTOMETRY team to test the new optical system in multiple configurations. To validate its operation at high altitude and under subsonic cruising speeds, the equipment will be deployed on the breakthrough laminar aircraft demonstrator in Europe (BLADE).
Keywords
Reflectometry, laminar flow wings, WING REFLECTOMETRY, infrared flash, digital photogrammetry
