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CFI Instrument Practical Test Standards, FAA-S-8081-9B, June 2001

II. Technical Subject Areas

A. Aircraft Flight Instruments and Navigation Equipment

    3. Anti-ice/deicing and weather detection equipment and their operating characteristics
      a. Airframe - structural icing
        1) Accumulation of ice on exterior surface of aircraft
        2) Requires
          a) Visible moisture (coulds, rain)
          b Freezing temperatures
        3) Types
          a) Rime
            i) Small droplets that freeze immediately
            ii) Milky white, rough looking
            iii) Especially on leading edges of wings and struts
          b) Clear
            i) Relatively slow freezing of large droplets
            ii) Can spread over large surface, changing shape of airfoil
            ii) Clear, hard to see, most dangerous
          c) Mixed
            i) Mixture of clear and rime
            ii) Ice particles embedded in clear ice, very rough
          OAT (°C) range Icing type
          -10 to 0 Clear
          -15 to -10 Mixed
          -20 to -15 Rime
        4) Effects
          a) Control problems due to change in airfoil shape
          b) Changed stall angle of attack and increased stall speed
          c) Decreased lift
          d) Increased drag
          e) Blocked or limited control surfaces
          f) Increased weight
          g) Roll upset caused by airflow separation which induces self deflection of ailerons
          Effects of ice on lift
        5) Inadvertent icing encounter
          a) When operating in visible moisture, anticipate ice by monitoring OAT
          b) Proper use of anti-icing/deicing equipment is critical. Refer to POH/AFM
          c) Activate appropriate anti-icing/deicing when OAT is 5°C or less before entering visible moisture
          d) Use flashlight to check for ice on night flights
          e) Pilot actions once airframe ice ammumulation begins
            i) Move to altitude with significantly colder temperatures
            ii) Move to altitude where temperatures are above freezing
            iii) Fly to an area clear of visible moisture
            iv) Change heading and fly to area known to be free of ice (e.g., consider 180° turn)
            v) Consider immediate landing at nearest suitable airport
        6) Anti-icing/deicing equipment
          a) Not designed for operation in icing conditions indefinitely
          b) Intended simply to allow pilot more time to get out of the icing conditions
        7) Cessna TR-182 and airframe icing
          a) Flight into known icing conditions is prohibited
            "Known icing does not mean a near-certainty of icing conditions, only that icing conditions are being reported or forecast."
            - NTSB
          b) No standard airframe anti-ice/deice equipment
          c) Windshield defrost air is supplied to outlet on top left side of antiglare shield. Activate by rotating DEFROST knob.
          d) Inadvertent icing encounter in Cessna TR-182
            i) Prop anti-ice ON
            ii) Pitot heat ON
            iii) Turn back or change altitude
            iv) Cabin heat full ON, windshield defrost ON
            v) Increase RPM to minimize prop ice
            vi) Beware carb ice. Apply carb heat only as required. Lean mixture if carb heat used continuously
            vii) Plan landing nearest suitable airport or "off airport" site
            viii) Beware: ¼ inch or more on leading edge significantly increases stall speed
            ix) Leave flaps retracted UP
            x) Open window, scrape ice if practical for landing visibility
            xi) Approach with forward slip if needed for visibility
            xii) Approach 85-95 KIAS
            xiii) Land in level attitude

    References:

Greg Gordon MD, CFII
Updated: