Having grown up in high performance jets that tend to fly above most of this stuff I don't have a lot of experience dealing with icing that the airplane cannot handle. (My worst experience: No Time to Nap.)
So let me just relate a few facts and leave it at that. For me, dealing with icing has always amounted to avoid it if you can, follow aircraft manufacturer limits and procedures when you can't. More about that: G450 Ice and Rain.
Everything here is from the references shown below, with a few comments in an alternate color.
Ice accretion vs. temperature, from ProPilot.
Figure: Ice types, from ProPilot
[Aeronautical Information Manual, Tble 7-1-8]
|Clear Ice||See Glaze Ice.|
|Glaze Ice||Ice, sometimes clear and smooth, but usually containing some air pockets, which results in a lumpy translucent appearance. Glaze ice results from supercooled drops/droplets striking a surface but not freezing rapidly on contact. Glaze ice is denser, harder, and sometimes more transparent than rime ice. Factors, which favor glaze formation, are those that favor slow dissipation of the heat of fusion (i.e., slight supercooling and rapid accretion). With larger accretions, the ice shape typically includes "horns" protruding from unprotected leading edge surfaces. It is the ice shape, rather than the clarity or color of the ice, which is most likely to be accurately assessed from the cockpit. The terms "clear" and "glaze" have been used for essentially the same type of ice accretion, although some reserve "clear" for thinner accretions which lack horns and conform to the airfoil.|
|Intercycle Ice||Ice which accumulates on a protected surface between actuation cycles of a deicing system.|
|Known or Observed or Detected Ice Accretion||Actual ice observed visually to be on the aircraft by the flight crew or identified by onboard sensors.|
|Mixed Ice||Simultaneous appearance or a combination of rime and glaze ice characteristics. Since the clarity, color, and shape of the ice will be a mixture of rime and glaze characteristics, accurate identification of mixed ice from the cockpit may be difficult.|
|Residual Ice||Ice which remains on a protected surface immediately after the actuation of a deicing system.|
|Rime Ice||A rough, milky, opaque ice formed by the rapid freezing of supercooled drops/droplets after they strike the aircraft. The rapid freezing results in air being trapped, giving the ice its opaque appearance and making it porous and brittle. Rime ice typically accretes along the stagnation line of an airfoil and is more regular in shape and conformal to the airfoil than glaze ice. It is the ice shape, rather than the clarity or color of the ice, which is most likely to be accurately assessed from the cockpit.|
|Runback Ice||Ice which forms from the freezing or refreezing of water leaving protected surfaces and running backto unprotected surfaces.|
|Note: Ice types are difficult for the pilot to discern and have uncertain effects on an airplane in flight. Ice type definitions will be included in the AIM for use in the "Remarks" section of the PIREP and for use in forecasting.|
[AC 91-74A, ¶3-1.]
[Aeronautical Information Manual, Tble 7-1-9]
|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 0_C (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 0_C (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 (SCDD)||Synonymous with freezing drizzle aloft.|
|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 0_C, i.e., freezing rain or freezing drizzle.|
[AC 00-45G, Table 3-9]
|Intensity||Contraction||Airframe Ice Accumulation|
|Trace||TRACE||Ice becomes perceptible. Rate of accumulation slightly greater than rate of sublimation. It is not hazardous even without the use of deicing/anti-icing equipment unless encountered for an extended period of time (over 1 hour).|
|Light||LGT||The rate of accumulation may create a problem if flight is prolonged in this environment (over 1 hour). Occasional use of deicing/anti-icing equipment removes/prevents accumulation. It does not present a problem if the deicing/anti-icing equipment is used.|
|Moderate||MOD||The rate of accumulation is such that even short encounters become potentially hazardous and use of deicing/anti-icing equipment or diversion is necessary.|
|Severe||SEV||The rate of accumulation is such that deicing/anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary.|
[AC 91-74A, ¶3-2.]
[AC 91-74A ¶4-2.a.] [The figure] shows how ice often affects the coefficient of lift for an airfoil. Note that at very low angles of attack, there may be little or no effect of the ice on the coefficient of lift. Thus when cruising at a low angle of attack (AOA), ice on the wing may have little effect on the lift. However, note that the maximum coefficient of lift (CLmax) is significantly reduced by the ice, and the AOA at which it occurs (the stall angle) is much lower. Thus when slowing down and increasing the AOA for approach, therefore, the pilot may find that ice on the wing that had little effect on lift in cruise now causes stall to occur at a lower AOA and higher speed. Even a thin layer of ice at the leading edge of a wing, especially if it is rough, can have a significant effect in increasing stall speed. For large ice shapes, especially those with horns, the lift may also be reduced at a lower AOA as well. Depending on the airfoil section, the lift loss may even be larger if ice accretes behind areas normally protected, such as due to large drop impingement and runback.
The figure is grossly simplified, the shape of the curve is likely to be changed as well. But the bottom line is correct: you will have less lift.
Advisory Circular 00-45G, Aviation Weather Services, July 29, 2010, U.S. Department of Transportation
Advisory Circular 91-74A, Pilot Guide to Flight in Icing Conditions, 12/31/07, U.S. Department of Transportation
Aeronautical Information Manual
Shein, Karsten, "Icing," Professional Pilot, October 2014, pp. 90 - 97.
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