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Monday, 10. August 2020

WP 2 Deformation Measurements on Wings and Control Surfaces

Image Pattern Correlation Technique (IPCT) provides unique possibilities to measure the exact shape and position of surfaces non-intrusively. The shape of the wing determines the aerodynamic loads and performances (lift and drag). Knowledge about the exact shape of the surfaces under flight conditions does enable to verify and improve the design of efficient and effective control surfaces which may lead to adjustments of the design of existing wings or the improvement of design tools. Beside IPCT, which provides the shape of the observed surface continuously, marker based optical deformation techniques can give the position of local marker positions and thus the global deformation of the wing and the position and orientation of control surfaces.

A step-by-step approach is followed for the development. In the first step of WP 2 the IPCT and the marker techniques are improved towards easy and accurate wing and control surface deformations. In the second step the improved measurement setups are tested and optimised during tests on research aircraft. In the third step the optimized setup is tested under industrial conditions.

Task 2.1 Improvement of IPCT and Marker based techniques towards industrial application

In this task the limitations of the application of measurement techniques identified in AIM are addressed and solutions for the currently major limitations will be developed. The main topics of this task are:

  • improving installation of the cameras on the aircraft with respect to an easy installation, i.e. the minimization of camera movements and compensation techniques for movements
  • optimizing the application of patterns and markers on the wing and the control and high lift surfaces
  • optimizing the calibration and recalibration procedures
  • application of IPCT and marker techniques on rotating control surfaces
  • application of IPCT and marker  techniques on vibrating surfaces

The improvements are to be developed by studying the theoretical basis of the technique, applying the consequences into an improved measurement set-up and by performing validation tests in the laboratory. At the end of this task solutions of the major limitations of the application of IPCT and the marker based techniques for application in flight tests shall be found and improved measurement setups and procedures should be present. Limitations of the measurement techniques, an estimation of measurement accuracy and error sources will be described.

Task 2.2 Research flight test with transport aircraft concerning wing and aileron deformation

Improvements of the IPCT and marker techniques developed in Task 2.1 are applied on the NLR Fairchild Metro II research aircraft. On-ground measurements do validate results of laboratory tests and in a next phase the improvements will be tested in research flight tests with the NLR research aircraft. The techniques will be applied with state-of-the-art high-resolution cameras imaging large areas of the wing as well as focussed images on the aileron as an example of a control surface. Reference measurements are to be made to assess effects of different flight parameters determining for instance camera motion on results.

Task 2.3. Evaluation of research test with transport aircraft concerning wing vibration

To assess the applicability of optical deformation measurement techniques for wing vibration measurements, a performed measurement campaign on the DLR A320 D-ATRA is used. The measurement results of both a complete accelerometer installation and the recorded stereo images are available and are subject to processing with the latest improvements from Task 2.1. The results of both, the image based deformation measurements and the accelerometer, are to be compared.

Task 2.4. Optical wing deformation measurements in an industrial environment

At least one of the optical measurement systems developed and optimized in Task 2.2 and 2.3 are installed on the Evektor VUT100Cobra. A comparative measuring system is installed too. The aim is to measure the wing twist and bending dynamically and in addition the deflection and deformation of the aileron in flight. The testing activities include ground tests in order to verify the setup and a flight test campaign with the VUT100 Cobra. The data processing and analysis is mainly be performed by DLR and NLR, while EVE, RUT and A-F do participate to learn how the processing is done. Finally an assessment of the optical wing deformation measurement techniques with respect to practical industrial applicability will be done.

AIM² Advanced In-Flight Measurement Techniques, c/o German Aerospace Center (DLR), Bunsenstrasse 10, 37075 Goettingen, Germany, Tel: +49 551 709 2252, Fax: +49 551 709 2830, Email: