Cover Image

Not for Sale



View/Hide Left Panel
Click for next page ( 45


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 44
44 The test sets were then sorted to separate those that the with the operational significance of these differences. A t-test indicated were from the same population, from those secondary analysis was also completed that examines the that were from different populations. For tests that were between-site differences using the conditions that are stip- determined to be from the same population, we can consider ulated in the CARs exemption; that any difference between the two sites is a random event Examination of Site Separation Distance. This section ex- due to sampling, and can assume there is no real difference amines the relationship of site separation distance and the between sites. extent of HOT differences due to these distances; For tests that were from different populations, the differ- Examination of Lake-effect Snowfall on HOT Differences. ence in mean holdover times was then calculated as a percent- This section examines the impact of lake-effect snow; age of the lower of the two values. These values, as well as the Comparison of HOTDS Results to Current Operational absolute difference in holdover times, were then examined Practices. This section provides a comparison of the HOTDS for significance from an operational perspective and for any results to example cases of information that pilots might de- dependency on distance between sites. rive from the use of current operational practices which use METAR reports or the FAA/TC visibility tables to estimate HOTs; and Secondary Analysis Methodology HOTDS Implementation Strategy and Timeline. This sec- to Account for CARs Exemption tion describes possible implementation strategies. An exemption from Canadian Aviation Regulations (CARs) (1) pertaining to ground deicing operations has been granted Between-Site Differences in HOT to a Canadian carrier for the purpose of permitting operational use of HOTs generated by a HOTDS. This exemption is sub- Based on the previously described data analysis methodol- ject to a number of conditions, some of which affect the calcu- ogy, potential differences in HOTs were determined for spe- lation of holdover times. Those conditions are: cific fluids from the consolidated data collected over the two test seasons. a) Holdover times shall be calculated on the basis of mea- This analysis was conducted to determine the effect that sured precipitation rates, increased by certain tolerances: any real difference in precipitation rate between the two sites From 0 to 10 g/dm2/h: + 3.0 g/dm2/h; would have on fluid HOTs. The initial treatment of the data Above 10 to 25 g/dm /h: 2 + 6.0 g/dm2/h; and thus required calculation of precipitation rates, followed by Above 25 g/dm2/h: + 14.0 g/dm2/h. calculation of fluid HOTs for a variety of fluids. b) The precipitation rate input for the purpose of computing The calculated HOTs for each precipitation data point fluid holdover times shall not be less than 2.0 g/dm2/h. were examined statistically to determine which test sets had c) Holdover time determinations shall be inhibited in snow differences that could not be attributed to random effects and conditions exceeding 50 g/dm2/h. the extent of difference in HOTs generated for each of the two d) Holdover time determinations in snow for Type II and IV sites. The analysis produced a table of results for each fluid; as de/anti-icing fluids shall be capped at 120 minutes. an example, the table for Octagon MaxFlo 100/0 is presented in Table 27. A secondary analysis was conducted wherein the mea- This fluid provides a good example of the extent of differ- sured data was adjusted according to these conditions. The ence in holdover times based on data collected at two sepa- statistical analysis then proceeded as described for the base rate sites. Similar charts for all fluids examined are included case. in Appendix C. This process caused a further number of test sets to be ex- Columns 1 through 4 show the test set number, the dis- cluded from analysis when their actual precipitation rate was tance between sites, the outside air temperature (OAT) at less than 2.0 g/dm2/h or their augmented precipitation rate which the test was conducted, and the average precipitation value exceeded 50 g/dm2/h. rate in snow based on all rate measurements from both sites. Columns 5 and 6 show the mean fluid HOTs for each site, Findings and Applications calculated for Octagon MaxFlo at 100/0 strength; Column 7 The findings and applications of the work completed for shows the calculated difference between Columns 5 and 6; the HOT variance across an airfield task are presented in this Column 8 is the percentage difference between Columns 5 section. They are presented as follows: and 6, based on the lower of the two values; and Columns 9 and 10 show the number and percentage of test sets grouped Between-site Differences in HOT. This section provides a by various parameters for between-site differences. For this summary of the between-site differences in HOTs along fluid, this grouping shows:

OCR for page 44
45 Table 27. Holdover time differences for Octagon MaxFlo 100/0 at two sites. Avg. Number of Tests Distance Comparison of Endurance Difference Set Rate in Specified Between Temp Times (min) as % of No. Both Difference Range Sites (C) Lowest Sites (feet) Site 1 Site 2 Difference Site # % (g/dm2/h) Test sets concluded as coming from same population 95 39% Test sets forced to equality by 120 minute rule 37 15% Test sets where difference is <20% 69 29% 221 28500 -9 17.2 47.7 39.6 8.1 20.5% 237 28500 -6 13.2 55.9 67.5 11.6 20.7% 95 7933 0.4 16.3 103.7 85.6 18.0 21.1% 312 27800 -10 6.0 113.8 93.9 19.8 21.1% 248 8300 -3.3 15.9 67.9 55.5 12.4 22.3% 65 4232 -3.2 11.0 93.1 76.1 17.0 22.4% 254 8300 -4 5.0 98.0 120.0 22.0 22.4% 233 28500 -6 10.0 70.0 86.6 16.6 23.7% 276 8300 -5.6 7.1 96.0 118.8 22.8 23.7% 304 27800 -10 12.3 50.5 62.6 12.2 24.1% 235 28500 -6 10.9 65.1 80.9 15.8 24.3% 258 8300 -4 9.3 103.2 82.6 20.6 25.0% 231 28500 -8 5.9 120.0 95.6 24.4 25.6% difference range 275 8300 -6 8.0 83.7 105.6 21.8 26.1% from 20 to <30% 306 27800 -10 10.4 72.9 57.8 15.2 26.2% 293 27800 -10 13.7 57.7 45.3 12.3 27.2% 218 28500 -10 23.7 36.2 28.4 7.8 27.4% 203 28500 -14 7.9 83.4 65.4 18.0 27.5% 242 8300 -3.3 14.4 75.8 59.0 16.8 28.5% 299 27800 -10 14.1 44.3 56.9 12.7 28.6% 251 8300 -3.3 8.4 93.1 120.0 26.9 28.9% 294 27800 -10 10.6 72.3 56.0 16.3 29.0% 210 28500 -12 13.2 56.6 43.8 12.8 29.2% 241 28500 -6 7.5 114.3 88.3 25.9 29.4% 228 28500 -8 11.6 72.4 55.8 16.5 29.6% 25 10% 300 27800 -10 12.3 64.6 49.7 14.9 30.1% 201 28500 -14 7.2 68.4 89.1 20.7 30.3% 230 28500 -8 7.0 85.2 111.6 26.4 30.9% 290 27800 -10 9.2 82.7 63.0 19.7 31.2% 107 7933 -3.9 24.4 35.8 47.0 11.3 31.5% difference range 30 4232 -4.8 8.8 107.7 80.1 27.5 34.4% from 30 to <50% 317 27800 -10 8.1 68.6 94.4 25.7 37.5% 246 8300 -3.3 22.9 53.0 38.5 14.5 37.7% 229 28500 -8 9.6 62.8 90.2 27.4 43.6% 9 4% 308 27800 -10 9.0 60.7 91.7 31.0 51.0% 240 28500 -6 7.8 120.0 77.0 43.0 55.8% 259 8300 -5 6.3 76.8 120.0 43.2 56.2% 226 28500 -9 7.4 72.2 117.3 45.0 62.3% difference range 249 8300 -3 12.3 62.1 104.7 42.6 68.7% >50% 253 8300 -4 9.4 69.4 120.0 50.6 72.9% 252 8300 -4 21.0 100.4 30.6 69.8 227.8% 7 3% Total tests analyzed 242 39% of 242 test sets had no significant difference in HOTs 10% had between-site holdover time differences from 20 between sites; to 30%; 15% of all test sets were forced to equality by the 120-minute 4% had between-site holdover time differences from 30 rule; to 50%; and 29% had between-site holdover time differences less than 3% had between-site holdover time differences greater 20%; than 50%.

OCR for page 44
46 Table 28. Assessment of operational significance (based on Octagon MaxFlo). Range of Between-Site Tests Within Average Between- Average HOT Differences as % of Range Site Difference in Both Sites Lowest Site (%) HOT (min) (min) 0 to 10 11% 3 50 10 to 20 18% 8 64 20 to 30 10% 17 83 30 and higher 7% 32 75 Operational Significance of Between-Site utes and the average HOT at both sites was 8 minutes. A dif- Differences in HOT ference of 17 minutes on a base of 83 minutes may have op- erational consequences. Of the 242 test sets analyzed for the Octagon MaxFlo 100/0, For the last range, where the between-site differences are 46% showed real between-site differences in HOTs. The ex- greater than 30%, the average HOT difference was 32 min- tent of the difference and its operational significance varied utes and the average HOT at both sites was 75 minutes. A dif- greatly among the data sets. To assess the likely impact on field ference of 32 minutes on a base of 75 minutes has a definite operations, the absolute size of between-site differences was operational effect. examined. Table 28 shows average values for between-site dif- It was concluded from this analysis that between-site differ- ferences and HOT for selected ranges. This format shows the ences in HOTs on the order of 20 to 30% are of potential relationship between absolute HOT differences and the aver- operational interest, and between-site differences greater than age value of HOT generated at both sites, and demonstrates 30% are of definite interest. an increase in HOT difference as the between-site differences grow larger. For the range where the between-site differences are above Summary of Differences--Base Case zero but less than 10% of the lowest site, the average HOT dif- The analysis described in the previous section was applied ference was 3 minutes and the average HOT at both sites was to each fluid in the manner shown for Octagon MaxFlo 50 minutes. A difference of 3 minutes on a base of 50 minutes 100/0 in Table 28. The resulting tables are provided in Ap- is not considered to be of large operational importance. pendix C; Table 29 is a summary of the results for all fluids Similarly, for the next highest range, between 10 and 20%, examined. the average HOT difference was 8 minutes and the average For all fluids examined, there was no statistical difference HOT at both sites was 64 minutes. Although larger than in the in the HOT times for the two sites for 39 to 40% of the data previous range, the difference of 8 minutes on a base of 64 min- sets collected. utes is still not judged to be of great operational importance. Holdover times for a number of data sets for thickened For the range where the between-site differences lie be- non-Newtonian fluids were constrained to 120 minutes, with tween 20 and 30%, the average HOT difference was 17 min- the consequence that there was no difference in HOT be- Table 29. Summary of between-site difference in fluid holdover time--base case. SAE Clariant Octagon Kilfrost Kilfrost Type I MP IV 2012 MaxFlo ABC-S ABC-S Fluid 100/0 100/0 75/25 50/50 No Statistical Difference 94 39% 95 39% 95 39% 95 39% 17 40% Forced to Equality by 120 0 0% 26 11% 37 15% 15 6% 1 2% Minute Rule Test Sets < 20 % 110 45% 88 36% 69 29% 88 36% 12 29% where Dif. in Endurance 20 to 30 % 13 5% 21 9% 25 10% 27 11% 4 10% Time as % of 30 to 50 % 14 6% 7 3% 9 4% 10 4% 2 5% Lowest Site is: > 50 % 11 5% 5 2% 7 3% 7 3% 6 14% Total Test Sets Analyzed 242 100% 242 100% 242 100% 242 100% 42 100%