Appendix D to Part 33 - Mixed Phase and Ice Crystal Icing Envelope (Deep Convective Clouds)
14:1.0.1.3.17.9.283.1.34 : Appendix D
Appendix D to Part 33 - Mixed Phase and Ice Crystal Icing Envelope
(Deep Convective Clouds)
The ice crystal icing envelope is depicted in Figure D1 of this
Appendix.
Within the envelope, total water content (TWC) in g/m 3 has been
determined based upon the adiabatic lapse defined by the convective
rise of 90% relative humidity air from sea level to higher
altitudes and scaled by a factor of 0.65 to a standard cloud length
of 17.4 nautical miles. Figure D2 of this Appendix displays TWC for
this distance over a range of ambient temperature within the
boundaries of the ice crystal envelope specified in Figure D1 of
this Appendix.
Ice crystal size median mass dimension (MMD) range is 50-200
microns (equivalent spherical size) based upon measurements near
convective storm cores.
The TWC can be treated as completely glaciated (ice crystal)
except as noted in the Table 1 of this Appendix.
Table 1 - Supercooled Liquid Portion of
TWC
| Temperature range - deg
C |
Horizontal cloud length -
nautical miles |
LWC -
g/m 3 |
| 0 to −20 |
≤50 |
≤1.0 |
| 0 to −20 |
Indefinite |
≤0.5 |
| < −20 |
|
0 |
The TWC levels displayed in Figure D2 of this Appendix represent
TWC values for a standard exposure distance (horizontal cloud
length) of 17.4 nautical miles that must be adjusted with length of
icing exposure.
[Amdt.
33-34, 79 FR 65538, Nov. 4, 2014]