Advanced In-Flight Measurement Techniques An Overview on Modern Optical Measurement Techniques for

Flight Testing applied within AIM and AIM²

Fritz Boden

Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)

Institute of Aerodynamics and Flow Mechanics

Göttingen

GERMANY

fritz.boden@dlr.de

+49 (0)551 709 2299

Dr. Nicholas Lawson Cranfield University

School of Engineering

MK43 0AL Cranfield

U.K.

n.lawson@cranfield.ac.uk

+44 (0)1234-758245

Application of classical sensors*) means:

• Very accurate local measurements (but only locally)

• Installation of lots of sensors + wiring at the aircraft

• Modification of the A/C structure (surface, mass and strength)

• Time consuming installation

• Experimental prototype has to be used (customer A/C not applicable)

Motivation

Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

*) e.g. strain gauges, accelerometers, pressure probes

Flight testing

• necessary part of A/C certification

• provide final validation of full scale A/C design

• critical and most expensive phase:

• all trials must be completed in a short time

• high quality standards in the certification process

• heavy instrumentation installed

advanced optical measurement techniques can overcome these drawbacks

AIM – Project Overview

Slide #4

Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

Advanced In-flight Measurement Techniques

Specific Targeted Research Project within the 6th European Framework

duration: 3 years + 6 months (1.11.06 – 30.04.10)

intended to apply advanced non-intrusive in-flight measurement techniques for

flight testing

consortium of 11 Partners (DLR, Airbus France, Eurocopter Germany, Eurocopter

France, Piaggio, EVEKTOR, NLR, ONERA, Cranfield University, Moscow Power

Engineering Institute, Airport Braunschweig – Wolfsburg)

• non-intrusive wing deformation measurements using IPCT

– small aircraft: Piaggio P.180 and Fairchild Metro II

– large passenger aircraft Airbus A380

• helicopter blade tip vortex measurements with LIDAR and PIV (Bo105)

• temperature measurements on engine exhaust (EC 255)

• optical deformation measurements on helicopter rotorblades (EC 135)

and propellerblades (Piaggio P.180)

• non-intrusive in-flight flow field measurements with PIV (Do 228)

• in-flight pressure measurements using PSP (VfW 614) (example below)

AIM – Achievements

Slide #5

Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

• Advanced Inflight Measurement Techniques 2 • CP in the 7th European Framework

• Duration: 42 Months + 6 Months (10/10 – 9/14)

• Funded by the European Commission

aim:

• further develop optical measurement techniques to be easily and routinely applied to in-flight testing with industrial demands

• developing reliable and easy to use dedicated measurement systems

• defining design and application rules for these new in-flight measurement techniques

3 progressive steps:

1. basic studies on challenges discovered in AIM

2. test of optimized measurement systems under research conditions

3. application of optimized measurement systems in an industrial

environment

Website: http://aim2.dlr.de

The follow-up project AIM² – Overview (1)

CP = Collaborative Project

Slide #6

Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

11 Partnerorganisations:

• DLR

• Airbus Operations SAS

• Avia Propellers

• Piaggio Aero Industries

• EVEKTOR

• NLR

• Rzeszów University of Technology

• ONERA

• Cranfield University

• MPEI (TU)

6 Work Packages (WP1-WP6)

The follow-up project AIM² - Overview (2)

WP1 Manage-

ment

WP2 Defor-mation of

Wings and Control

Surfaces

WP3 Defor-mation of Propeller Blades

WP4 Surface

Flow Measure-

ments

WP5 Flow Field

Measure-ments

WP6 Tools and

Demonstra-tion

Slide #7

Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

• Background Oriented Schlieren technique

• image based density measurement technique

• uses deviation of light due to refractive index changes in density gradients (e.g. in compressible flow regimes, non-uniform temperature fields, gas mixtures)

• randomly patterned background recorded without density gradient (reference image) and with density gradient in the line of sight (measurement image) cross correlation algorithms identify pattern shifts visualisation of density gradients e.g. vortex core location, jet location

AIM² Measurement Techniques - BOS

x

Slide #8

Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

• Fiber Bragg Grating (FBG) method – wing strain measurement

• Extrinsic Fibre Fabry Perot Interferometer (EFFPI) – pressure measurement

• FBG – Fibres labelled with holographic gratings (few mm’s long) laser light transmitted through the fibre change in reflected spectrum yields to temperature or strain change at grating location

• EFFPI – Fibre tip modified with diaphragm, laser transmitted down fibre and reflected light forms an interferometer as diaphram deflects with pressure

AIM² Measurement Techniques – FBG (1)

Slide #9

Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

FBG Method FBG Method

• Fiber Bragg Grating (FBG) method – wing strain measurement

• Extrinsic Fibre Fabry Perot Interferometer (EFFPI) – pressure measurement

AIM² Measurement Techniques – FBG (2)

Slide #10

Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

• Fiber Bragg Grating (FBG) method – wing strain measurement

• Extrinsic Fibre Fabry Perot Interferometer (EFFPI) – pressure measurement

AIM² Measurement Techniques – FBG (3)

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Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

• image based deformation measurement techniques

• Marker based techniques optical tracking of markers on the investigated object application of photogrammetry algorithms measurement of global 3D deformation or 3D position and orientation

• Image Pattern Correlation Technique recording of a random dot pattern on the investigated object application of cross correlation and photogrammetry algorithms measurement of 3D position, shape and local deformation of wings and propeller blades

AIM² Measurement Techniques – Markers and IPCT

Slide #12

Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

• InfraRed Thermography

• Surface temperature and surface flow transition measurement technique

• Recording of infrared radiation from investigated surface image of the thermal topology of the surface laminar-turbulent transition causes jump in wall stress coefficient jump in heat transfer coefficient detection and visualisation of transition from laminar to turbulent flow, laminar separations and in some cases also vortices

AIM² Measurement Techniques – IRT

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Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

• LIght Detection And Ranging

• optical direct air speed measurement technique

• radiation of single frequency laser light wave light wave reflected by natural aerosols Doppler shift of the reflected wave length due to aerosol movement recording and comparison of emitted and reflected wave determination of Doppler shift and time lag local air speed measurement (if scanning flow field)

• Direct measurement = no calibration needed can be used to calibrate e.g. FTI

AIM² Measurement Techniques – LIDAR

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Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

• Particle Image Velocimetry

• image based measurement technique for instantaneous flow velocity fields

• recording of tracer particles in the measured flow illuminated by two co-planar pulsed laser light sheets cross correlation of both particle images displacement vector field flow field topology known time delay and magnification of the recording system velocity vector field

AIM² Measurement Techniques – PIV

Laser Light Sheet

Position of Camera

Window

Laser Light Exit

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Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

flap measurements on A320 with IPCT

• AIM and AIM² have been first steps in establishing modern optical measurement techniques in flight testing

• several flight test demonstrations showed their applicability, their limitations and their advantages

• tools and guidance material has been created to ease future application of those techniques

• some AIM Techniques reached high TRL can be now applied easily by experts (see exploitation examples below)

• for daily application by non-experienced, further development is required

Conclusion and Summary

Slide #16

Advanced In-Flight Measurement Techniques – Aerodays 2015 – N. Lawson, F. Boden – http://aim2.dlr.de EU FP6 - Contract #030827 EU FP7 - Contract #266107

(ISBN 978-3642347375)

(ISBN978-3732237401)

in-flight vortex measurements on A320 with PIV

Wingtip

inboard

strake-vortex

outboard

strake-vortex

deployed flaps

The will take place in

in cooperation with