The design of a new aircraft as well as the modification of existing types requires comprehensive numerical and experimental studies. The results of the design process and thus the definitive quality of the product will be verified during flight tests for certification. Extrapolating data obtained in the wind tunnel or at low Reynolds number simulations to real flight is not trivial and primarily based on engineering experience, sometimes exhibiting considerable deviations from the predictions. In terms of measurement techniques non-intrusive optical image based methods have undergone considerable technological progress during the past decade.
This project made advanced, nonintrusive measurement techniques applicable for time and cost effective industrial flight testing as well as in-flight testing for research.
The purpose of the 3-year AIM programme was to further develop measurement techniques in such a way that they can be routinely applied to flight tests, hence providing comprehensive planar information on various important parameters such as wing and propeller deformation, thermal loads on the structures of helicopters, the surface pressure distribution on a wing, density gradients of strong vortices generated by airplanes and helicopters and velocity flow fields near airplanes and helicopters.
All measurements were carried out in full-scale outdoor flight tests on five aircraft (VfW614 ATTAS, BAe Jetstream, Piaggio P180, Fairchild Metro II, Airbus A380) and three helicopters (Eurocopter EC-135 ACT/FHS, Eurocopter Superpuma, MBB Bo 105).
The AIM project was divided into six technical Work packages and one management Work package:
- WP 0 - Project Management and coordination;
- WP 1 - Wing Deformation Studies - the objective was to further develop the IPCT method for wing deformation measurements in investigations carried out in the laboratory and in research flight tests.
- WP2 - Propeller Deformation Studies - the objective was to further develop QVT and IPCT for propeller deformation studies carried out in the laboratory and in research flight tests on a small aircraft.
- WP 3 - Helicopter Studies - the intention of this work package was the development of applicable setups of the QVT, IPCT, PIV, LIDAR, IRT and BOS technique for rotor blade systems.
- WP 4 - Surface Flow Measurements - within this work package the PSP technique is further developed and adapted for a feasibility test for the measurement of planar pressure distributions on a wing carried out in the laboratory and in a research flight test.
- WP 5 - High Lift Flow Structures - in this work package BOS and PIV were tested for ground-based measurements to monitor wing vortices generated from aircraft on approach condition. The viability of using the technique PIV for in-flight measurements under a range of flight conditions was also tested.
- WP 6 - Industrial Flight Testing - This work package consisted of all industrial flight tests of transportation aircraft as well as of helicopters. The results of the flight tests are evaluated and transferred to the industrial flight tests. For the tests a number of advanced image-based measurement techniques, which are most suitable and of highest industrial interest, were applied to industrial flight tests.
Ten Partners from aircraft industries, airport services and research organisations from seven countries worked closely together in the AIM consortium.
The following advanced optical measurement techniques tested within AIM have been described and some sample applications have been given to show the potential of these techniques:
- Particle Image Velocimetry(PIV);
- Background Oriented Schlieren method (BOS);
- Image Pattern Correlation Technique (IPCT);
- Quantitative Video Technique (QVT);
- Light Detection and Ranging method (LiDaR);
- Pressure Sensitive Paint (PSP) and
- Infra Red Technique (IRT).
The AIM project clearly demonstrated innovative possibilities of joint multinational cooperation between aircraft industries and research organisations. The EU-funded project ended in October 2009, but during the work in this project a multitude of demanding inflight applications for nonintrusive measurement techniques were identified which will have to be addressed in future.