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The field phase of the Second Alliance Icing Research Study (AIRS II) was conducted from November 2003 to February 2004, with the main center of interest being near Mirabel, Quebec. The AIRS II project operational objectives are to: a) develop techniques/systems to remotely detect, diagnose and forecast hazardous winter conditions at airports, b) improve weather forecasts of aircraft icing conditions, c) better characterize the aircraft-icing environment and d) improve our understanding of the icing process and its effect on aircraft. In order to support the operational objectives, the following science objectives are being addressed to: a) investigate the conditions associated with supercooled large drop formation, b) determine conditions governing cloud glaciation, c) document the spatial distribution of ice crystals and supercooled water and the conditions under which they co-exist, and d) verify the response of remote sensors to various cloud particles, and determine how this can be exploited to remotely determine cloud composition. Five research aircraft were involved in the field project. These aircraft flew special flight operations over a network of ground in-situ and remote-sensing meteorological measurement systems, located at Mirabel, Quebec. Data were collected to evaluate some prototype airport weather forecasting systems, which use satellite and surface-based remote sensors, PIREPS, and numerical forecast models. The project will also be used in North America and Europe to further develop numerical forecast models, and forecast systems, which predict aircraft icing over large areas. AIRS II is an exciting collaborative effort involving approximately 26 government and university groups from Canada, the United States and Europe. It will assist in providing the aviation community better tools to avoid aircraft icing, and to improve the efficiency of airport operations.

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The objective of this effort was to validate in flight, data that has been gathered in the NASA Lewis Research Center' s Icing Research Tunnel (IRT) over the past several years. All data was acquired in flight on the NASA Lewis Research Center' s Twin Otter Icing Research Aircraft. A faired 3.5 in. diameter metal-clad cylinder exposed to the natural icing environment was observed by a close-up video camera The grazing angle video footage was recorded to S-VHS video tape and after the icing encounter, the resultant ice shape was documented by 35 mID photography and pencil tracings . The feather growth area was of primary interest; however, all regions of the ice accretion, from the stagnation line to the aft edge of runback were observed and recorded. After analysis of the recorded data several interesting points became evident: (1) The measured flight feather growth rate is consistent with IRT values, (2) The feather growth rate appears to be influenced by droplet size, (3) The feathers were straighter in the lower, spottier L WC of flight in comparison to those observed in the IRT, (4) Feather shedding and ice sublimation may be significant to the final ice shape, (5) The snow encountered on these flights appeared to have little influence on ice growth.