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Advanced In-Flight Measurement Techniques

Tags: Air


The research project Advanced In-flight Measurement Techniques (AIM) has the aim of developing advanced, non-intrusive, in-flight measurement techniques for the purpose of efficient, cost-effective, in-flight testing for certification and in-flight research for aircraft and helicopters. In order to achieve this ambitious goal, AIM will organize and structure a close collaboration among leading experts from industry, research organizations, universities and a SME with complementary knowledge of and experience in in-flight testing, development of image-based measurement techniques and operation of small airports.

The results of the design process and thus the quality of a new aircraft 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 measurement methods have undergone considerable technological progress over the last decades and are now used as standard diagnostic techniques to measure planar distributions of velocity, pressure, density and model deformation in industrial wind tunnels.


Non-intrusive, optical image-based measurement techniques shall be further developed such that they can be routinely applied to flight tests to provide comprehensive information on various important parameters such as wing and propeller deformation, thermal loads on the structure of helicopters, the planar pressure distribution on a wing, density gradients in strong vortices generated by airplanes and helicopters and velocity flow fields near airplanes and helicopters.

The objectives of AIM are:

  • To prepare new flight test measurement techniques with a significant improvement in accuracy, ease of installation and measurement speed resulting in a major reduction in the duration and cost of flight test programs for the industry. This advance is essential for both aircraft and helicopter development and certification,
  • To facilitate new collaboration between European industry and the academic sector for the application of advanced in-flight measurement techniques,
  • To assess the feasibility of implementing existing advanced image based measurement techniques for flow field measurements during in-flight tests,
  • To validate the most promising techniques in an in-flight test performed with a large industrial transport aircraft, a helicopter and a light aircraft carried out by the flight testing department of the industrial partners.
Image Pattern Correlation Technique applied to an Airbus A 340: Setup and result.
Image Pattern Correlation Technique applied to an Airbus A 340: Setup and result.

Description of work

The work plan has been constructed on a fast-track with simultaneous efforts on all technological aspects. The same measurement techniques will be adapted to different applications. To avoid duplication of work and increase the innovation per time unit, the work packages are strongly linked. The work packages themselves are defined by the technological application:

  1. Wing deformation studies,
  2. Propeller deformation studies,
  3. Helicopter studies,
  4. Surface flow measurements,
  5. High lift structures,
  6. Industrial flight testing.


The expected results of the project are reliable optical measurement techniques performed in-flight for certification as well as for research purposes. This project will demonstrate only the general feasibility of the measurement techniques, since not all possible application can be tested.

In particular, the goal of AIM is to use of the following measurement techniques for in-flight investigations:

  • Image Pattern Correlation Technique (IPCT) for the measurement of local deformations of e.g. wing, aileron and flap and with help of Quantitative Video Technique (QVT) for the determination of local propeller and rotor deformations,
  • Particle Image Velocimetry (PIV) for the measurement of a velocity flow field of a vortex and velocity fields in high lift configurations,
  • Background Oriented Schlieren method (BOS) for the measurement of the density gradients of a flow field and therefore to determine the position and strength of spatial vortex filaments,
  • Light detection and ranging (LIDAR) for the measurement of a velocity flow field of a vortex,
  • Pressure Sensitive Paint (PSP) for the measurement of surface pressures,
  • Infrared Technique (IRT) for the measurement of surface heat distributions.
P 180 after the take off
P 180 after the take off