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80 trate fluid required in a diluted operation price of new annually by TC, the FAA, and the AEA. The TC documents are Type I concentrate and/or Type II/III/IV concentrate); and provided in Table 48 (SAE Type I Deicing Fluid Application Subtracting the additional annual fixed costs. Procedures) and Table 49 (SAE Type II, Type III, Type IV Anti- icing Fluid Application Procedures) for reference. These tables The annual glycol savings are determined by: are taken from the Transport Canada Holdover Time Guide- lines and are very similar to the tables in the SAE ARP 4737, Type I: Subtracting the liters of concentrate fluid required in FAA, and AEA guidance materials. the diluted operation (concentrate is assumed to be 100% Results from the survey indicate that both airlines and glycol) from the liters of glycol required in the current oper- DSPs feel the information contained in these tables pro- ation (liters ready-to-use fluid required glycol percentage vides adequate guidance for the use of fluids and their dilu- in ready-to-use fluid); and tions. Neither group recommended changes to the guidance Type II/III/IV: Subtracting the liters of neat fluid required in material. the diluted operation from the liters of neat fluid required in However, deicing trainers and others expressed the need for the standard operation and multiplying by the glycol per- a possible modification, with the objective of encouraging centage in the neat fluid. greater use of fluid dilutions. This possible modification could be summed up in a direct quote from one respondent: The years to breakeven are determined by: The FAA and Transport Canada could add more language not Comparing the annual financial savings to the initial invest- necessarily to regulation CFR 14 121.629, or the Canadian equiva- lent, but perhaps to TP 14052, AC 120-60, or any annual guidance ment required (set-up costs plus capital costs) and deter- published by either regulator. Language could be included to mining how many years it will take for the annual savings to encourage dilutions, and examples provided showing that dilutions pay for the initial investment. are not as difficult to accomplish as perceived by numerous deicing entities. The AEA Deicing recommendations could employ a sim- ilar strategy. Since ARP 4737 is a recommended practice, language Model Testing again could be added to better show the merits of more closely fol- lowing FPD buffers instead of always using 50/50, or some other The cost-benefit model was refined and validated through a concentration where the buffer is much larger than needed. testing process. The testing process involved running the devel- oped model through a variety of scenarios and situations cre- ated by inputting various parameter values representing both Implication of the Availability of typical and extreme operations. This process confirmed that Diluted Fluid Holdover Times the model can provide reasonably accurate outcomes for a variety of situations and users. Documents related to endurance time testing and the deter- mination of holdover times were reviewed as part of the liter- ature review. Findings and Applications Type I holdover times have been derived from endurance The findings and applications of the work completed to time tests with various fluids mixed to a 10C buffer (i.e., the examine the current practices and regulations, opportunities, fluids are applied at a concentration such that the freezing limitations, obstacles, and potential benefits associated with point of the fluid is at least 10C below that ambient tempera- the usage of diluted aircraft de/anti-icing fluids are addressed ture). The temperature and quantity of fluid applied in these in this section. tests is such that it replicates typical application of fluid on air- craft. In the course of the testing to develop these holdover times, associated research was conducted to compare the Examination of Current Government endurance times of fluids applied at a 10C buffer versus fluid and Industry Regulations, Guidance applied at standard 50/50 mixes which had more glycol. The Material, and Standards Related research showed that the extra glycol 50/50 mixes did not pro- to the Use of Fluid Dilutions vide significant endurance time benefits; generally, it was found that the heat from the fluid was a greater contributor to Adequacy of Current Regulations holdover times than the additional glycol. This result was also Specific guidelines in SAE ARP 4737 address procedures for found to be true when research was conducted to examine the the application of Type I, II, III, and IV fluids in both one-step use of negative buffers that can be used for the first step of a and two-step de/anti-icing procedures. These general guide- two-step application. This research is documented in a TC lines are also contained in the guidance documents published Report TP13315E, Aircraft Deicing Fluid Freeze Point Buffer