Until nowadays, during icing certification flight tests, Airbus used meteorological probes, FSSP and King probe, to determine cloud granulometry. The measurements help to find the different conditions asked by Appendix C. Airbus France has developed a new probe, called Nephelometer, measuring particle sizes between 12 micron and 400 micron, adapted to operational requirements, instead of FSSP and King probe. The Nephelometer is based on an optical principle called 'coherent shadowgraphy': droplets and crystals going through the measurement area of the probe are lightened by a low coherency punctual source. The number and the size of the droplets are measured from their shadow on a CCD. A pulsed laser coupled to a fast camera freezes the movement. Image processing is done in real time and results are provided to the flight test engineer. All data and raw images are recorded in order to allow on-ground complementary analysis if necessary. The probe is designed to be easily installed through a dummy window. It is retractable which allows the aircraft to fly at VMO (Maximum Operating Limit Speed) without flight conditions limitations, and to install the Nephelometer not only for specific icing tests. All outside part of the probe is electrically de-iced. Nephelometer now exists in triplicate. During the fine tuning phase, experiments in icing tunnel and on plane have been held, involving FSSP, King Probe and Nephelometer. The results of the different probes are herein compared. Recently, a dossier has been made up for Nephelometer qualification (for droplets up to 99 micron), and the last A380 icing certification campaign has been performed with the Nephelometer as prime instrument. At present, validation activities are continuing for larger droplets, up to 400 micron. Freezing fog is also assessed.
Nephelometer: A flight test probe for cloud characterization
2009
5 Seiten, 9 Bilder, 10 Quellen
Conference paper
Storage medium
English
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