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OCR for page 66
66 However, at the May 21, 2009 meeting of the SAE G-12 Aircraft Manufacturers Aircraft Ground Deicing Methods Subcommittee, the addi- In performing spot deicing for frost removal, standard fluid tion of wording related to spot deicing was discussed. The fol- application procedures are typically employed, in which a fan lowing proposed wording for paragraph 6.5 was agreed to by spray nozzle setting is used. Also, Type I fluids applied at a 60C the subcommittee: temperature (at the nozzle) are used extensively. Of the air car- riers that have adopted spot deicing for frost removal proce- For non-active frost limited to a small patch on the upper dures, the survey indicated that this practice is performed on wing surface or horizontal stabilizer, and when no precipitation is falling or expected, `local area' deicing may be carried out. most current commercial aircraft, thus precluding the need for Spray the affected area with a heated fluid/water mix suitable for additional guidance from aircraft manufacturers. a One-Step Procedure, and then spray the same area on the As an example, page 307, paragraph 9 of the Boeing Aircraft other wing. Both wings must be treated identically (same areas, Maintenance Manual (AMM-12-33-01) for the B-737 600-900 same amount and type of fluid, even if the frost is only present series of aircraft states: on one wing. (Refer to aircraft manufacturers requirements for specific guidance) The trained and qualified person releasing the aircraft must The right and left side of the wing and the horizontal stabilizer visually check that the treatment was done symmetrically and must get the same ice removal/anti-icing treatment. that all frozen deposits have been removed, and then report the a) If contamination exists only in a limited area (such as details of the treatment to the Flight Crew. spoiler panel) and there is no active precipitation, it is per- CAUTION: Holdover times do not apply. mitted to deice only that area, but the same area should be treated on the other wing. Adoption and passage of the revised version of ARP 4737 (ARP 4737H) is anticipated prior to the start of the 200910 Summary winter deicing season. Although government and industry regulations, guidance material, and standards current at the time of the literature AEA review did not appear to provide sufficient guidance for con- ducting spot deicing for frost removal, changes recommended A specific AEA recommended procedure for spot deicing to SAE ARP 4737, which are expected to be adopted for the for frost is found in paragraph 3.9.1.3.2 of the AEA docu- winter 200910 operating season, should correct this defi- ment, Recommendations for De/Anti-icing of Aircraft on the ciency. Changes in FAA and aircraft manufacturer guidance Ground: materials do not appear to be necessary. For frost limited to a small patch on the upper wing surface only, and when no precipitation is falling or expected, `local Laboratory Tests area' deicing may be carried out. Spray the affected area with a heated fluid/water mix suitable for a One-Step Procedure, then This section examines results of the laboratory tests from the spray the same area on the other wing. Both wings must be perspectives of spot deicing for non-active frost (due to radia- treated identically (same areas, same amount and type of fluid, tion cooling) and for active frost (due to cold-soaked surfaces). same mixture strength), even if the frost is only present on one A detailed log of tests showing test variables and measured wing. The trained and qualified person releasing the aircraft must results is provided in Appendix E. check that the treatment was done symmetrically and that all frozen deposits have been removed, and then report the details of Assessment of Frost Severity the treatment to the Commander. CAUTION: Holdover times do not apply. The test plates were allowed to accumulate frost for a one- hour period prior to conducting the spot deicing tests. The amount of frost on the plate at test time is of interest as the FAA water content of the melted frost can trigger early freezing The FAA Ground Icing Research Lead participated in the due to fluid dilution. survey discussed above and indicated the following position on To assess frost severity for non-active frost deicing, the spot deicing for frost removal: "currently spot deicing is not frost amounts for the various test sets were simply com- prohibited by the FAA; however it is not specifically encour- pared, using the highest as the base case. The results shown aged. Generally the FAA would expect the operator to follow in Table 43 indicate that test surfaces for test sets 3b, 3c and instructions from the airframe manufacturer in the aircraft 5 had collected considerably more frost than for the other maintenance manual. . . ." test sets.

OCR for page 66
67 Table 43. Assessment of frost severity for frost spot-deicing. Ranking of Frost Chamber Test Surface Frost for Frost for Test Accumulation Temp Delta Temp Deice* Deice* Set (% of greatest F (C) F (C) (g/hr) (g/dm2/h) amount) 1 -19.5 (-28.6) 32 (0) 1.1 0.09 0.24 2 2.1 (-16.6) 5.4 to 10.8 (3 to 6) 2.1 0.16 0.47 3 24.4 (-4.2) 3.6 to 5.4 (2 to 3) 1.4 0.11 0.31 3a 24.4 (-4.2) 1.8 to 7.2 (1 to 4) 0.5 0.04 0.11 3b 26.6 (-3.0) 12.6 to 19.8 (7 to 11) 3.8 0.29 0.84 3c 26.6 (-3.0) 7.2 (4) 4.5 0.35 1.00 4 13.5 (-10.3) 7.2 (4) 0.8 0.06 0.18 5 35.4 (1.9) 10.8 (6) 3.2 0.25 0.71 * Test surfaces were exposed to chamber conditions for one-hour prior to test to accumulate frost on test surfaces. To assess frost severity during the active frost tests, mea- Results for Spot Deicing in Non-Active Frost sured frost rates were compared to rates proposed for frost Forty (40) mL of fluid (0.011 U.S. gal) prepared at an 18F testing in natural conditions. These rates were proposed in (10C) buffer and applied at 86F (30C) was of sufficient previous studies to determine test methodology for fluid amount and strength to de-ice non-active frost surfaces. endurance times in natural frost, and vary for different ambi- Most non-active frost test surfaces subjected to spot deicing ent conditions. The results are shown in Table 44. with this fluid condition remained clean for the duration of Test 3b experienced a rate of frost generation much greater the test (2.5 hrs). The shortest interval until refreezing was than proposed for standard testing as shown in Figure 24, 115 minutes. while tests 1 and 2 were close to proposed standard test rates. Forty (40) mL of fluid on a test plate is equivalent to 0.27L/m2. The application of fluid at a minimum rate of 1/3 L/m2 Quantity of Fluid Needed to Remove Frost (approximately 1/3 US quart per 10 ft2) could be used as a guide to field operations. Results from both active and non-active frost tests generally The fluid should be applied at a temperature not less than indicated that 10 mL of fluid was not enough to cover and de- 140F (60C) at the spray nozzle as this generally produces an ice the entire surface plate area, 20 mL was barely enough, and on-wing fluid temperature of 86F (30C) due to cooling 40 mL was sufficient to remove frost from test plate surfaces. between nozzle and wing. Table 44. Assessment of frost severity for anti-icing in cold-soak conditions. Test Anti-ice Anti-ice Anti-ice Recommended Chamber % of Test Surface Test Test Test Standard Test Temp. Standard Set Delta Temp Rate Rate Rate Rate* F (C) Rate F (C) (g/2.5hr) (g/hr) (g/dm2/h) (g/dm2/hr) 1 -19.5 (-28.6) 32 (0) 2.1 0.84 0.07 0.08 81% 5.4 to 10.8 2 2.1 (-16.6) 3.6 1.44 0.11 0.13 86% (3 to 6) 3.6 to 5.4 3 24.4 (-4.2) 4 1.6 0.12 0.21 59% (2 to 3) 1.8 to 7.2 3a 24.4 (-4.2) 0.7 0.28 0.02 0.21 10% (1 to 4) 2.6 to 19.8 3b 26.6 (-3.0) 10.9 4.36 0.34 0.23 147% (7 to 11) 3c 26.6 (-3.0) 7.2 (4) 4.2 1.68 0.13 0.23 57% 4 13.5 (-10.3) 7.2 (4) 0.6 0.24 0.02 0.15 12% 5 35.4 (1.9) 10.8 (6) 3.2 1.28 0.10 0.28 35% * Recommended frost generation rate for Type I fluid tests; see Transport Canada report TP 14145E, Figure 4.10.