Pt. 25, App. O

14 CFR Ch. I (1-1-19 Edition)

PART I - METEOROLOGY

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In this Appendix 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 100Sectionm to
500 Sectionm):
(1) Pressure altitude range: 0 to 22,000 feet
MSL.
(2) Maximum vertical extent: 12,000 feet.
(3) Horizontal extent: Standard distance of
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 17.4 nautical miles.
(5) Drop diameter distribution: Figure 2.
(6) Altitude and temperature envelope:
Figure 3.
(b) Freezing Rain (Conditions with spectra
maximum drop diameters greater than 500
Sectionm):

(1) Pressure altitude range: 0 to 12,000 ft
MSL.
(2) Maximum vertical extent: 7,000 ft.
(3) Horizontal extent: Standard distance of
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 17.4 nautical miles.
(5) Drop Diameter Distribution: Figure 5.
(6) Altitude and temperature envelope:
Figure 6.
(c) Horizontal extent.
The liquid water content for freezing drizzle and freezing rain conditions for horizontal extents other than the standard 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 Section 0.213 log10(H)
Where:
S = Liquid Water Content Scale Factor
(dimensionless) and
H = horizontal extent in nautical miles

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