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OCR for page 83
83 Ready-to-use Type I fluid is the most common form of Type Most deicing and anti-icing procedures occurring in I fluid used; 65% of Type I fluid use reported by respondents freezing precipitation are performed using the two-step pro- was with ready-to-use fluid rather than fluid mixed to spe- cedure. For the anti-icing step in the two-step procedure, cific FFP buffers. 76% of all respondents indicated that they use a Type IV The majority (85%) of respondents do not use Type II, III 100/0 fluid mix. or IV fluid mixes for one-step procedures. A number of interesting comments on the use of diluted flu- Of the respondents having proportional blending equip- ids were given (see details in Appendix C). In general, they ment, a 10C buffer was most commonly used for Type I addressed: fluids. The majority of respondents (82 to 88%) do not use hot The respondents own particular situation or approach to water for deicing as the first step in a two-step procedure, using diluted fluids; regardless if Type I fluid or Type II/III/IV fluid is used for A desire for a different mix (60/40) for Type II fluid; the second step; nor do they use hot water for defrosting A lack of awareness or willingness of some DSP customers operations. to accept use of fluid diluted to the full extent of the Most operations at non-hub airports do not make use of approved buffer; diluted fluids. The need for attention to wing temperature differences from OAT; and The survey results are discussed further in the next section. Constraints due to limited labor skills. Application of Findings to Current Practice Of those operators and DSPs that used deicing equipment with fluid proportioning capabilities, it was indicated that sub- The combined findings of the literature review, phone stantial savings in Type I fluid usage could be achieved. One interviews, and focus group survey are examined in this sec- respondent claimed reductions in Type I fluid glycol consump- tion as they relate to current practices. tion as much as 63% in one season through use of dilutions. Extent of Use of Fluid Dilutions Factors Influencing Decision to Use Fluid Dilutions Of all survey respondents, 65% use a ready-to-use Type I The survey asked respondents to rank the influence of a fluid mix such as 50/50 or 55/45, and 76% use a Type II or Type number of factors in the decision to use Type I ready-to-use IV 100/0 fluid mix. No respondents indicated current use of a mixes instead of fluids blended to appropriate buffer mixes, Type III fluid mix at this time. and 100/0 concentrations of Type IV fluids rather than 75/25 For Type I fluid applications, the extent of use of a 10C or 50/50 mixes. Tables 50 and 51 present the factors ranked buffer and a 10 to 20C buffer were about equal. A small per- in descending order of importance by the survey respondents centage indicated use of a buffer of 30C or higher: no expla- for Type I fluid and Type IV fluid, respectively. nation was given for the use of this high buffer. A large number Several respondents indicated that additional fluid savings of airline respondents were unsure as to the extent of use of could be realized if forced air could be used in conjunction high buffer fluids; presumably this is due to operations per- with proportional blending for deicing. To proceed with this formed for them by DSPs. Of those respondents who had Type I fluid proportioning approach, research would be required to determine if the use of equipment installed on deicers, 25% applied first-step deicing forced air either in conjunction with Type I proportional blend- fluid with a FFP buffer of -3C, while 41% used fluid with a ing or with full strength fluid is a suitable and safe procedure. FFP buffer of 10C. For the same operators, 55% of anti-icing with Type I fluid was performed with a 10C buffer. Use of 0C to -3C Buffer for First-Step Deicing Interviews indicated that airports with limited facilities, milder temperatures, or both use Type I mixes for anti-icing. The optimum use of fluid dilutions occurs with the use of a The main use of Type II and Type IV blends was for defrosting 0/100 dilution or "Hot Water" for deicing. Regulatory guid- related activities. ance documents allow this procedure in the first step of a two- Over 85% of the airlines and DSPs interviewed do not use step application when the ambient temperature is -3C and Type II, III or IV fluid mixes for the one-step de/anti-icing pro- above. However, 88% of the survey respondents do not use cedure. The respondents who do use Type II/III/IV fluids for this procedure. One concern mentioned was that the follow- this procedure indicated Type II 50/50 and Type IV 100/0 as up anti-icing fluid coating had to be a mix heated to 60C, the most commonly used fluids/mixes for this procedure. with the appropriate buffer, if Type I fluid was used. The 12%

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84 Table 50. Decision factors for Type I fluid Table 51. Decision factors for Type IV fluid ready-to-use mix versus dilutions. 100/0 concentration versus 75/25 or 50/50 concentrations. Decision Factors (Ranked in descending order Rank of importance) Decision Factors (Ranked in descending order Rank of importance) 1 Fluid Storage Requirements 2 Prevailing OAT during the Winter Deicing Season 1 Cost of Blending Equipment 3 Cost of Fluid 2 Prevailing OAT during the Winter Deicing Season 4 Cost of Blending Equipment 3 Cost of Fluid 5 Replacement Cost of Modern Deicing Equipment 4 Fluid Storage Requirements 6 Environmental Issues/Concerns 5 Replacement Cost of Modern Deicing Equipment 7 Cost of Fluid Application Equipment 6 Training of Deicing Personnel 8 Training of Deicing Personnel 7 Large Variations in OAT during a De/Anti-Icing Event 9 Availability of Suitable Water to Effect Blending 8 Environmental Issues/Concerns 10 Large Variations in OAT during a De/Anti-Icing Event 9 Cost of Fluid Application Equipment 11 Protection Against Freeze up in Deicing Vehicle Systems 10 Geographic Location of Airport 12 Fluid Quality Control Checks 11 Checking/Inspection Equipment and Requirements 13 Geographic Location of Airport 12 Fluid Quality Control Checks 14 Location of Available Airport Space for Deicing Operations 13 Fluid Reclaim, Reuse, Reblending Factors 15 Fluid Reclaim, Reuse, Reblending Factors 14 Fluid Availability 16 Fluid Availability 15 Availability of Suitable Water to Effect Blending 17 Checking/Inspection Equipment and Requirements 16 Location of Available Airport Space for Deicing Operations 18 Need for Changes to Regulations/Guidance Documents 17 Fluid Application Time 19 Fluid Application Time 18 Need for Changes to Regulations/Guidance Documents 20 Proximity to Fluid Manufacturer's Plant 19 Proximity to Fluid Manufacturer's Plant that do use hot water for deicing reported no problems with most temperatures in the United States. The survey indicated its usage. that only 1 to 2% of airlines annual operations are delayed or Similarly, regulations allow use of Type I fluids mixed to a suspended due to lowest operational use temperature (LOUT) -3C buffer for first-step deicing when OAT is below -3C. inadequacies from deicing fluids. Only 24% of respondents make use of this procedure. The freeze point of a typical Type I 50/50 fluid mix varies from approximately -26C to approximately -38C depend- ing primarily upon the type of glycol used. Thus, in the major- Use of Type I Ready-to-Use Mixes ity of deicing activities that occur in the -10C to +3C Ready-to-use mixes of Type I fluids have been a mainstay of temperature band, an excessive fluid concentration is used. aircraft deicing operations in the past. Currently these mixes The survey indicated 35% of respondents do not use a are still prevalent at most commercial service airports (hub, Type I ready-to-use mix. Of the remaining 65% that do use non-hub, reliever/feeder airports, and, to a greater extent, gen- ready-to-use mixes, 24% used them most of the time, and only eral aviation airports). The ready-to-use mixes are typically 12% used them all of the time. supplied in 1000 gallon tanks and 55 gallon drums. They are Of those operators equipped with deicers having propor- used with older or conventional deicing equipment that do not tional blending capability, about 40% used ready-to-use mixes have proportional blending capabilities. Fluid manufacturers half of the time. supply these ready-to-use mixes in blends requested by the user. The mix ratio may change during the deicing season to Use of Type I Concentrated Aircraft Deicing Fluid accommodate the colder months of the winter, with lower strength blends being supplied in the late fall, early winter time Interviews indicated that many North American deicers at frame and in the early spring time frame. In addition, many major hubs and large satellite airports procure Type I fluid in airports will opt for the stronger concentrations, i.e., 60/40, if 100/0 concentration. These airports have blending capabilities their site has a history of extreme cold climatic conditions (vehicular mounted or remote blending stations for pedestal throughout the deicing season. mounted systems) and use 10C buffer criteria for blend con- Of these ready-to-use mixes, the 55/45 blend is possibly the centrations. To a lesser extent, Type I neat concentrations are mix used most often, as its freeze point is around -34C for a supplied to outlying stations, however these stations must have propylene-glycol based fluid and is deemed to be adequate for blending capabilities since Type I 100/0 must be blended before

OCR for page 83
85 application. In areas where there is a large excursion in temper- In the few cases where dilutions of Type IV fluid are applied, atures, remote blending stations may require that the mixes be these mixes are typically of a 50/50 concentration and are used reblended often. in frost removal procedures. Use of Type II Fluids Deicing Equipment Requirements Type II anti-icing fluids are a mainstay of the Western Euro- Current deicing equipment is available in several configura- pean and some Asian aviation communities, and are used in all tions that include conventional equipment with one, two, concentrations. Airports with warmer prevailing climates such three, or four tanks. For operations at general aviation and as London Gatwick (LGW) typically opt for the lower concen- small regional airports, the one-tank system may be employed. trations of 50/50 or 75/25 whereas many of the Northern Euro- It is usually non-motorized, holds 250500 gallons, and would pean airports use the stronger concentrations as dictated by be filled with a 50/50 mix of Type I fluid. At many satellite and holdover time requirements. There was no record of Type II major airports the two-tank system is used. Here, one tank fluids being used in North America in recent years. would hold a ready-to-use Type I fluid mix and the other The survey respondents indicated that only diluted Type II would hold a much smaller quantity of 100/0 Type IV fluid. (50/50 or 75/25) fluid is used in the one-step de/anti-icing pro- The three-tank system usually has a medium-to-large tank cedure. For the second step of the two-step procedure, Type II with capacities of 1000 gallons up to 3000+gallons. In this sys- showed very little use and that only at 100/0 strength. tem one tank would contain water, one would contain Type I fluid, and one would contain either Type II or Type IV fluid. Water would normally be blended with the Type I fluid to Use of Type III Fluids achieve mixes with the required freeze point. In the four-tank This fluid type, introduced early in the first decade of the system there would be a small standby tank for instant mixing 21st century, was intended to fill the need for a longer holdover and heating of deicing fluids just before application. time than Type I fluids, while being able to be pumped and Some of these deicing systems may be equipped with a applied by the existing conventional deicing units with a pis- high velocity forced air system. This equipment has been ton type pump system. Type III holdover times are significantly shown to use less fluid than those of conventional design to longer than those of Type I fluids. Of the DSPs and airlines sur- achieve the same de/anti-icing capability. The least amount veyed, none use Type III fluids at this time; however, the fluid of fluid usage was obtained with those systems using a com- manufacturer has indicated that some airlines are using the bination of forced air and a proportional blended Type I mix fluid. This fluid is fully developed and approved. Endurance for deicing when climatic conditions permitted. Some deic- time tests have been conducted and holdover time guidelines ing providers did not have the latter equipment with the are available for Type III fluid at all three concentrations. forced air capability. The survey indicated that more DSPs than airlines had deicers equipped with proportional blending capability. Forty- Use of Type IV Fluids nine percent (49%) of operations conducted by DSPs are con- Type IV fluid is the primary anti-icing fluid and is used by ducted with deicers having proportional blending capability, North American, Western European, and Asian deicers. In the compared to 28% of aircraft deiced by airlines. 100/0 concentration it typically possesses the longest holdover times and is used in this concentration throughout North Use of Fluid Dilutions at Regional Airports America, even though in many cases a 75/25 or 50/50 dilution would be sufficient to effect a safe takeoff in the prevailing The survey indicated that regional non-hub and general avi- freezing climatic condition. In several climatic conditions, the ation airports are unlikely to have equipment with propor- holdover times for 75/25 mixes of some Type IV fluids exceed tional blending capabilities. Type I ready-to-use mix is the those of the 100/0 concentration. This has been attributed to most commonly used fluid at these airports. the fact that when water is added to the concentrated version of the fluid, the fluid builds up thicker on the surface, due to an Manpower Requirements increase in viscosity. This phenomenon in turn produces longer holdover times. Although most airlines are aware of this Additional manpower is not required for the application performance, Type IV fluid is still routinely applied in the of de/anti-icing fluid dilutions. However, additional train- 100/0 concentration. The survey indicated that 76% of users ing in the correct selection of dilution blends for ambient apply only full strength Type IV fluid for the second-step anti- conditions, skin temperatures, or both is very important. icing application. Normally senior deicing inspection/checking personnel will