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74 CHAPTER 5 Increased Use of Aircraft De/Anti-Icing Fluid Dilutions Introduction fluid mixes from remote blending systems with large storage capabilities. Broad application of such systems to dispense This part of the report documents the task that examined the Type I fluid at the approved 10C fluid freeze point buffer use of aircraft de/anti-icing fluid dilutions. reduces the amount of glycol dispensed in Type I operations. Background Industry Use of Type II, III, and IV Fluids Mixes Industry Use of 10C Type I Fluid Buffer Type II, III, and IV anti-icing fluids are available at fluid con- SAE ARP 4737 states that Type I fluids used for either one- centrations of 100/0, 75/25, and 50/50. Fluid holdover times step de/anti-icing or as the anti-icing fluid in a two-step oper- are derived from endurance time test results measured using ation must have a FFP at least 10C (18F) below the ambient fluid mixed to these concentrations. Some 75/25 fluid concen- temperature. Type I fluid holdover times are measured using trations have published holdover times similar to 100/0 fluids. fluids mixed with water to this FFP. In the past, the general Also, most 50/50 anti-icing fluids have holdover times in excess industry practice when de/anti-icing with Type I fluid had of Type I fluids. Despite the opportunity to employ lower been to apply Type I fluid at the standard, as-delivered fluid concentrations of Type II, III, and IV fluids, anti-icing opera- concentration, typically a 50/50 (50% water/50% glycol) or a tions in North America use 100/0 Type IV fluid concentrations 55/45 mix. Other specific mixes such as 60/40 are available almost exclusively. As a result, there is considerable opportu- from fluid manufacturers. These special mixes are selected to nity to reduce the amount of glycol dispensed by applying these provide optimum FFP performance at colder temperatures fluids at lower, already approved concentrations. and are usually based upon prior climatic records of prevail- ing OATs at a given airport. Although Type I fluid mixes are Objective required to have only a 10C buffer, the Type I fluid 50/50 mixes typically have FFP well below the required 10C buffer The objective of this task was to examine current practices for most prevailing temperatures during aircraft deicing oper- and regulations related to the increased use of fluid dilutions ations. This practice results in dispensing much more glycol and to document the opportunities, limitations, obstacles, and content than is necessary, and could lead to unnecessary oper- potential benefits associated with their use. ational costs and increased stress on the environment. Cur- The objective was met by completing the following work rently, this trend is being reversed and many airlines that elements: perform their own deicing and many deicing service providers (DSPs) have converted to the use of deicing equipment with Conduct a literature review of current government and proportional blending capabilities. industry regulations, guidance material, and standards to In the recent past, deicer manufacturers have incorporated document current industry regulations and practices related fluid blending systems into their deicing units that blend Type to the use of fluid dilutions; I fluid with water. In addition, at major hubs where a signifi- Conduct phone interviews with DSPs and airlines; cant number of de/anti-icing operations are carried out annu- Conduct a survey to gather pertinent information from a ally, such as Pittsburgh and Denver, the trend has been to wider audience, including airlines, DSPs, deicing consult- install pedestal mounted deicing equipment that are supplied ants, deicing instruction facilities, and regulators;