Part I - Meteorology

• ED Decision 2015/008/R found in: CS-25 Amdt 27 - Large Aeroplanes (Jan 2023)

Part I – Meteorology ED Decision 2015/008/R Appendix O icing conditions are defined by the parameters of altitude, vertical and horizontal extent, temperature, liquid water content, and water mass distribution as a function of drop diameter distribution. (a) Freezing Drizzle (Conditions with spectra maximum drop diameters from 100 μm to 500 μm): (1) Pressure altitude range: 0 to 6 706 m (22 000 feet) MSL. (2) Maximum vertical extent: 3 656 m (12 000 feet). (3) Horizontal extent: standard distance of 32.2 km (17.4 nautical miles). (4) Total liquid water content: Note: Liquid water content (LWC) in grams per cubic meter (g/m3) based on horizontal extent standard distance of 32.2 km (17.4 nautical miles). Figure 1 – Appendix O, Freezing Drizzle, Liquid Water Content  (5) Drop diameter distribution: Figure 2 – Appendix O, Freezing Drizzle, Drop Diameter Distribution  (6) Altitude and temperature envelope: Figure 3 – Appendix O, Freezing Drizzle, Altitude and Temperature  (b) Freezing Rain (Conditions with spectra maximum drop diameters greater than 500 μm): (1) Pressure altitude range: 0 to 3656 m (12000 ft) MSL. (2) Maximum vertical extent: 2134 m (7000 ft). (3) Horizontal extent: standard distance of 32.2 km (17.4 nautical miles). (4) Total liquid water content: Note: LWC in grams per cubic meter (g/m3) based on horizontal extent standard distance of 32.2 km (17.4 nautical miles). Figure 4 – Appendix O, Freezing Rain, Liquid Water Content  (5) Drop diameter distribution: Figure 5 – Appendix O, Freezing Rain, Drop Diameter Distribution  (6) Altitude and temperature envelope: Figure 6 – Appendix O, Freezing Rain, Altitude and Temperature  (c) Horizontal extent The liquid water content for freezing drizzle and freezing rain conditions for horizontal extents other than the standard 32.2 km (17.4 nautical miles) can be determined by the value of the liquid water content determined from Figure 1 or Figure 4, multiplied by the factor provided in Figure 7, which is defined by the following equation: S = 1.266 – 0.213 log10(H) Where S = Liquid Water Content Scale Factor (dimensionless) and H = horizontal extent in nautical miles Figure 7 – Appendix O, Horizontal Extent, Freezing Drizzle and Freezing Rain  [Amdt 25/16]