Hot Water Deicing of Aircraft
APS AVIATION INC MONTREAL (QUEBEC)
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A research program was undertaken to further examine environmental limits for the application of hot water as the first-step fluid in a two-step deicing procedure. Results from several previous related studies were used to determine an approach to current testing and as sources of related data. Tests on flat plates were conducted at the National Research Council Canada NRC, Climatic Engineering Facility CEF in Ottawa. Test parameters included temperature, wind, active precipitation type and rate, and substrate material. Standard test plates were fabricated from typical aircraft composite materials as well as from aircraft aluminum. A controlled level of contamination was allowed to collect on the plates prior to each test run by exposing the plate to precipitation for a predetermined time interval, The resulting layer of ice contamination was then removed by spraying as much fluid as was required to produce a clean plate. Fluids tested included water, diluted Society of Automotive Engineers SAE Type I fluid, and full strength SAE Type I fluid. The most critical data measured in these trials were the time intervals between fluid application spray and first appearance of ice on test surfaces. An interval of at least 3 minutes was the key indicator of acceptable temperature and wind limits. Laboratory testing has shown that at a precipitation rate of 25 gmsq cmhr, hot water provides a period of protection equal to or better than Type I mixed to the approved buffer -3 deg C at outside air temperature OAT down to -6 deg C and wind speeds to 10 kph. A Type I premix provided about the same period of protection at the same test conditions 2 to 3 minutes. Increasing the level of surface contamination has no significant effect on fluid performance since increased quantities of hot water are required to deice, which negates the effect of increased contamination.