Aero-Tips!

A good pilot is always learning -- how many times have you heard this old standard throughout your flying career? There is no truer statement in all of flying (well, with the possible exception of "there are no old, bold pilots.")

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Aero-Tips 12.08.06

Most pilots are used to the Pilot Report (PIREP) intensity reports for structural ice accumulation. Describing ice as "light, moderate or severe" gives a good idea of whether a pilot may or should venture into those conditions. But sometimes pilots want a little more information about the ice's characteristics -- especially if flying an aircraft that can safely (and legally) plan a flight into "known ice."

The Aeronautical Information Manual (AIM) contains a table that gives standardizes descriptors for an "amplified" icing PIREP. Consider how hearing each type of report, alone or in combination, would affect your decision making before takeoff, and if you first heard the report while aloft.

• 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 on-board 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 back to unprotected surfaces.

Aero-tip of the day: Using the proper terminology helps you better understand icing PIREPs, and for your reports to have more meaning for other pilots.

FMI: Aero-Tips