SAE AIR 5396A-2015 Characterizations of Aircraft Icing Conditions.pdf

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5、5396Characterizations of Aircraft Icing ConditionsRATIONALEThe information presented in the report is revised to reflect current icing certification procedures. The document is technically correct for Appendix C icing conditions, is mature and is not likely to change in the foreseeable future. There

6、 are additional icing condition definitions that have been developed to address supercooled large drop icing and mixed phase/ice crystal conditions. Addition of these icing conditions to this AIR would not fit within the scope of this document. Therefore, the document will not be revised in the futu

7、re and the intent is to stabilize the document at its five year review.1. SCOPEThis SAE Aerospace Information Report (AIR) provides various graphical displays of atmospheric variables related to aircraft icing conditions in natural clouds. It is intended as a review of recent developments on the sub

8、ject, and for stimulating thought on novel ways to arrange and use the available data. Included in this Report is FAR 25 (JAR 25) Appendix C, the established Aircraft Icing Atmospheric Characterization used for engineering design, development, testing and certification of civilian aircraft to fly in

9、 aircraft icing conditions.1.1 PurposeResearch on aircraft icing conditions in the atmosphere has been conducted intermittently since the 1940s. But, until recently, only the data gathered during the first few years of flight research had been condensed into extreme value envelopes and publicized fo

10、r use in the design of ice protection systems for aircraft. One purpose of this AIR is to assemble in one document some new ideas on displaying icing-related variables and using them for various applications.1.2 Field of ApplicationThis report presents atmospheric data that describes the aircraft ic

11、ing environment. The report contains four different approaches in displaying and using the data:1.2.1 Currently Accepted Civil Design Envelopes (“FAR-25, Appendix C“).1.2.2 U.S. Air Force Trial Design Envelopes.1.2.3 Distance-Based Envelopes.1.2.4 A Nomogram and Statistical Approach.SAE INTERNATIONA

12、L AIR5396A Page2of 472. REFERENCES2.1 Applicable References2.1.1 Lewis, W., “A Flight Investigation of the Meteorological Conditions Conducive to the Formation of Ice on Airplanes,” NACA TN 1393, 1947.2.1.2 Lewis, W., Kline, D.B., and Steinmetz, C.P., “A Further Investigation of the Meteorological C

13、onditions Conducive to Aircraft Icing,” NACA TN 1424, 1947.2.1.3 Bergrun, N.R. and Neel, C.B., “The Calculation of the Heat Required for Wing Thermal Ice Prevention in Specified Icing Conditions,” NACA TN 1472, 1947.2.1.4 Jones, A.R. and Lewis, W., “Recommended Values of Meteorological Factors to be

14、 Considered in the Design of Aircraft Ice-Prevention Equipment,” NACA TN 1855, 1949.2.1.5 Hacker, P.T. and Dorsch, R.G., “A Summary of Meteorological Conditions Associated with Aircraft Icing and a Proposed Method of Selecting Design Criterions for Ice-Protection Equipment,” NACA TN 2569, 1951.2.1.6

15、 Brun, R.J., Lewis, W., Perkins, P.J., and Serafini, J.S., “Impingement of Cloud Droplets on a Cylinder and Procedure for Measuring Liquid-Water Content and Droplet Sizes in Supercooled Clouds by Rotating Multicylinder Method,” NACA Report 1215, 1955 (supersedes NACA TN 2903, TN 2904 and RM E53D23).

16、2.1.7 Federal Aviation Regulations, Part 25 (FAR 25), “Airworthiness Standards: Transport Category Airplanes,” Appendix C, (Code of Federal Regulations, Title 14, Chapter 1, Part 25, Appendix C), Superintendent of Documents, Government Printing Office, Washington, DC 20402. This same document is kno

17、wn as JAR-25Appendix C by European Civil Airworthiness Authorities.2.1.8 Meeting No. 11 of SAE Subcommittee AC-9C Aircraft Icing Technology of the SAE Aircraft Division, Zurich, Switzerland, September 18-22, 1989.2.1.9 Jeck, R.K., “Analyses of Supercooled Cloud Variables for Aircraft Icing Condition

18、s Over the United States,” U.S. Department of Transportation/Federal Aviation Administration Report DOT/FAA/CT-86/20, 1986.2.1.10 Masters, C.O., “A New Characterization of Supercooled Clouds Below 10,000 Feet AGL,” U.S. Department of Transportation/Federal Aviation Administration Report DOT/FAA/CT-8

19、3/22, 1983.2.1.11 Jeck, R.K., “Advances in the Characterization of Supercooled Clouds for Aircraft Icing Applications,” U.S. Department of Transportation/Federal Aviation Administration Report DOT/FAA/AR-07/4.2.1.12 “Engines, Aircraft, Turbine,” JSSG-2007.2.1.13 “Aircraft Icing Handbook,“ DOT/FAA/CT

20、-88/8-1, March 1991.2.1.14 Bowden, D.T., et. al., Engineering Summary of Airframe Icing Technical Data,“ TR ADS-4, March 1964.2.1.15 Lewis, W., “Meteorological Aspects of Aircraft Icing,“ Comp. of Meteo., Am. Meteo. Soc., pg. 1197-1203, 1954.2.1.16 NAVAER 50-1C-528, November 1955.2.1.17 “Forecasters

21、 Guide on Aircraft Icing,” AWS/TR-80/001, March, 1980, Air Weather Service, Scott AFB, IL 62225, 58 p.2.1.18 Heath, E.D. one set for layered clouds (Figures B1A and B4A) and one set for convective clouds (Figures B1B and B4B). The four charts in each set are: Temperature versus Altitude, Liquid Wate

22、r Content versus Temperature, Liquid Water Content versus Altitude, and Horizontal Extent versus Liquid Water Content. The envelopes given represent 99.9% of icing conditions, that is, these data are the result of a 0.001 probability analysis (Reference 2.1.1). These envelopes are a compromise betwe

23、en environment definition and utility for engineers and designers. Note that these charts are preliminary and input from all interested parties is highly encouraged. The shortcomings and possible additions will be discussed later. Our hope is to coordinate the final version of these charts with all

24、of the DOD and with the future FAA envelopes so that, as much as possible, they are the same. We wish to alleviate the burden that two sets of criteria place on the manufacturers.3.2.4 Using the ChartsFigure B1A, Temperature versus Altitude encompasses 99.9% of icing conditions in layered clouds. Fi

25、gures B2, Liquid Water Content versus Temperature and Figure B3A, Liquid Water Content versus Altitude define limits of liquid water content in layered clouds based on temperature and altitude respectively. Figure B4A, Horizontal Extent versus Liquid Water Content defines a LWC factor based on the l

26、ength (in nmi) of the icing encounter in layered clouds. Figures B1B to B4B contain the same information for convective clouds.SAE INTERNATIONAL AIR5396A Page7of 47Figure B1A presents the temperature/altitude envelope in which icing conditions in layered clouds may be encountered by aircraft in norm

27、al flight operations. It does not indicate the severity of those conditions. Figure B2A presents the range of LWCs that can be found at the temperature of interest. Figure B3A presents the range of LWCs possible at the altitude of interest. The curves on Figures B2A and B3A define the limits of LWC

28、based on temperature and altitude respectively. As the data of Figures B2A and B3A are normalized to a 17.4 nmi cloud, Figure B4A further factors the LWC for horizontal extent. The convective cloud information is presented in the same manner on Figures B1B to B4B.3.2.4.1 Examples of Chart Usage3.2.4

29、.1.1 Layered Clouds Example No.13.2.4.1.1.1 Choose an altitude/temperature combination. 10k feet at -20 C (Figure B1A).3.2.4.1.1.2 Check LWC range based on temperature choice. 0.0 to 0.7 g/m3(Figure B2A).3.2.4.1.1.3 Check LWC range based on altitude choice. 0.0 to 0.9 g/m3(Figure B3A).3.2.4.1.1.4 De

30、termine limiting factor. Temperature limits LWC at 0.7 g/m3.3.2.4.1.1.5 Choose LWC from range based on limiting factor. Choose maximum for this example: 0.7 g/m3. NOTE: Any LWC up to the maximum value is a valid choice.3.2.4.1.1.6 Choose extent and determine LWC factor. Choose 50 nmi. Yields factor

31、of 0.66 (Figure B4A).3.2.4.1.1.7 Result: 50 nmi icing encounter at 10k feet at -20 C with LWC of 0.46 g/m3.3.2.4.1.2 Layered Clouds Example No.23.2.4.1.2.1 Choose an altitude/temperature combination. 10k feet at -10 C (Figure B1A).3.2.4.1.2.2 Check LWC range based on temperature choice. 0.0 to 1.0 g

32、/m3(Figure B2A).3.2.4.1.2.3 Check LWC range based on altitude choice. 0.0 to 0.9 g/m3(Figure B3A).3.2.4.1.2.4 Determine limiting factor. Altitude limits LWC at 0.9 g/m3.3.2.4.1.2.5 Choose LWC from range based on limiting factor. Choose maximum for this example: 0.9 g/m3. NOTE: Any LWC up to the maxi

33、mum value is a valid choice.3.2.4.1.2.6 Choose extent and determine LWC factor. Choose 50 nmi. Yields factor of 0.66 (Figure B4A).3.2.4.1.2.7 Result: 50 nmi icing encounter at 10k feet at -10 C with LWC of 0.59 g/m3. As expected the warmer temperature supports a higher maximum LWC and in both cases

34、the horizontal extent factors the normalized cloud to a lower LWC.3.2.4.1.3 Convective Clouds Example No.13.2.4.1.3.1 Choose an altitude/temperature combination. 20k feet at -25 C (Figure B1B).3.2.4.1.3.2 Check LWC range based on temperature choice. 0.0 to 1.3 g/m3(Figure B2B). 3.2.4.1.3.3 Check LWC

35、 range based on altitude choice. 0.0 to 3.5 g/m3(Figure B3B).3.2.4.1.3.4 Determine limiting factor. Temperature limits LWC at 1.3 g/m3.3.2.4.1.3.5 Choose LWC from range based on limiting factor. Choose maximum for this example: 1.3 g/m3. NOTE: Any LWC in this range is a valid choice.SAE INTERNATIONA

36、L AIR5396A Page8of 473.2.4.1.3.6 Choose extent and determine LWC factor. Choose 1.0 nmi. Yields factor of 1.19. (Figure B4B).3.2.4.1.3.7 Result: 1.0 nmi icing encounter at 20k feet at -25 C with LWC of 1.55 g/m3.3.2.4.1.4 Convective Clouds Example No.23.2.4.1.4.1 Choose an altitude/temperature combi

37、nation. 20k feet at -15 C (Figure B1B).3.2.4.1.4.2 Check LWC range based on temperature choice. 0.0 to 3.4 g/m3(Figure B2B). 3.2.4.1.4.3 Check LWC range based on altitude choice. 0.0 to 3.5 g/m3(Figure B3B). 3.2.4.1.4.4 Determine limiting factor. Temperature limits LWC at 3.4 g/m3.3.2.4.1.4.5 Choose

38、 LWC from range based on limiting factor. Choose maximum for this example: 3.4 g/m3. NOTE: Any LWC in this range is a valid choice.3.2.4.1.4.6 Choose extent and determine LWC factor. Choose 1.0 nmi. Yields factor of 1.19 (Figure B4B).3.2.4.1.4.7 Result: 1.0 nmi icing encounter at 20k feet at -15 C w

39、ith LWC of 4.0 g/m3. Again the warmer temperature supports a higher LWC and the horizontal extent factors the LWC of the normalized cloud to a higher value.3.2.4.1.5 Convective Clouds Example No. 33.2.4.1.5.1 Choose an altitude/temperature combination. 20k feet at -30 C (Figure B1B).3.2.4.1.5.2 Chec

40、k LWC range based on temperature choice. 0.0 to 0.5 g/m3(Figure B2B).3.2.4.1.5.3 Check LWC range based on altitude choice. 0.0 to 3.5 g/m3(Figure B3B).3.2.4.1.5.4 Determine limiting factor. Temperature limits LWC at 0.5 g/m3.3.2.4.1.5.5 Choose LWC from range based on limiting factor. Choose maximum

41、for this example: 0.5 g/m3. NOTE: Any LWC in this range is a valid choice.3.2.4.1.5.6 Choose extent and determine LWC factor. Choose 1.0 nmi. Yields factor of 1.19 (Figure B4B).3.2.4.1.5.7 Result: 1.0 nmi icing encounter at 20k feet at -30 C with LWC of 0.6 g/m3.3.2.4.2 Application of the New Charac

42、terizationWhat impact would this new environment have on current uses of the MIL-Standard envelopes? To examine the implications we have chosen an icing condition suggested by JSSG-2007 (Reference 2.1.12); Low Altitude Loiter. The changes to LWC dictated by the new characterization are shown in the

43、accompanying charts. In this case the pressure altitude, flight speed, and ambient temperature were used to determine the values necessary to utilize the charts as in the previous examples. The duration values were used to determine the required horizontal extent. Using the Layered CloudCharts we se

44、e that the LWC is limited by altitude and it is further modified by the horizontal extents (HE). Notice that the LWCs are most severe for the short durations and least severe for the longest exposure (11 minutes or 35.2 nmi). For the short durations the new envelopes yield less severe LWCs but for t

45、he longer durations the LWCs become more severe. Interestingly, if the Convective Cloud Charts are used for the short duration exposures (2 minutes or 6.4 nmi) the results are the same for this particular example. This example demonstrates but one possible implication. Actually we would expect the n

46、ew envelopes to be used in a broader sense that is to determine all of the test condition parameters. And possibly the new envelopes would indicate a vastly different combination of temperature and altitude, not just LWC, as the critical case(s).SAE INTERNATIONAL AIR5396A Page9of 473.2.4.3 Questions

47、 about the New EnvelopesIs this method of presentation acceptable? Is presentation of the “limits“ all that is required? Is more information needed: probability of occurrence, duration versus altitude, droplet size (MVD) versus altitude or some relevant parameter (if one can be found)? All of these

48、questions (and likely many more) must be addressed before consideration for incorporation into a MIL-PRIME can occur.This characterization has been adopted as the specified icing environment in a current USAF program. We anticipate that the lessons learned during this program will be extremely valua

49、ble in the effort toward a new and universal icing environment definition.3.3 Distance-Based Envelopes (Contributed by Richard K. Jeck) (Reference 2.1.22)3.3.1 IntroductionOver the past several years, a computerized database of some 28,000 nmi of inflight measurements of icing conditions has been assembled at the FAA Technical Center. One purpose of this project was to explore new ways to quantitatively describe icing c