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7110.65R
AIM
AIM      CHG 2                                                                                                  3/15/07
                                                                                                                5/26/16
                                                                                                               12/10/15


                                                   TBL 7-1-9
                                              Icing Conditions
Appendix C Icing Conditions      Appendix C (14 CFR, Part 25 and 29) is the certification icing condition standard
                                 for approving ice protection provisions on aircraft. The conditions are specified in
                                 terms of altitude, temperature, liquid water content (LWC), representative droplet
                                 size (mean effective drop diameter [MED]), and cloud horizontal extent.
Forecast Icing Conditions        Environmental conditions expected by a National Weather Service or an
                                 FAA-approved weather provider to be conducive to the formation of inflight icing
                                 on aircraft.
Freezing Drizzle (FZDZ)          Drizzle is precipitation at ground level or aloft in the form of liquid water drops
                                 which have diameters less than 0.5 mm and greater than 0.05 mm. Freezing drizzle
                                 is drizzle that exists at air temperatures less than 0C (supercooled), remains in
                                 liquid form, and freezes upon contact with objects on the surface or airborne.
Freezing Precipitation           Freezing precipitation is freezing rain or freezing drizzle falling through or outside
                                 of visible cloud.
Freezing Rain (FZRA)             Rain is precipitation at ground level or aloft in the form of liquid water drops which
                                 have diameters greater than 0.5 mm. Freezing rain is rain that exists at air
                                 temperatures less than 0C (supercooled), remains in liquid form, and freezes upon
                                 contact with objects on the ground or in the air.
Icing in Cloud                   Icing occurring within visible cloud. Cloud droplets (diameter < 0.05 mm) will be
                                 present; freezing drizzle and/or freezing rain may or may not be present.
Icing in Precipitation           Icing occurring from an encounter with freezing precipitation, that is, supercooled
                                 drops with diameters exceeding 0.05 mm, within or outside of visible cloud.
Known Icing Conditions           Atmospheric conditions in which the formation of ice is observed or detected in
                                 flight.
                                 Note-
                                 Because of the variability in space and time of atmospheric conditions, the existence
                                 of a report of observed icing does not assure the presence or intensity of icing
                                 conditions at a later time, nor can a report of no icing assure the absence of icing
                                 conditions at a later time.
Potential Icing Conditions       Atmospheric icing conditions that are typically defined by airframe manufacturers
                                 relative to temperature and visible moisture that may result in aircraft ice accretion
                                 on the ground or in flight. The potential icing conditions are typically defined in the
                                 Airplane Flight Manual or in the Airplane Operation Manual.
Supercooled Drizzle Drops        Synonymous with freezing drizzle aloft.
(SCDD)
Supercooled Drops or /Droplets   Water drops/droplets which remain unfrozen at temperatures below 0 C.
                                 Supercooled drops are found in clouds, freezing drizzle, and freezing rain in the
                                 atmosphere. These drops may impinge and freeze after contact on aircraft surfaces.
Supercooled Large Drops (SLD)    Liquid droplets with diameters greater than 0.05 mm at temperatures less than
                                 0C, i.e., freezing rain or freezing drizzle.




7-1-42                                                                                                    Meteorology