The Semantics Of "Known Icing Conditions"

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AOPA on Monday reported that wording contained in a June 6 letter from the FAA's Eastern Region counsel attempting to clarify the legal interpretation of "known icing conditions," would, if literally applied, "unnecessarily ground many safe general aviation flights" this winter. A sentence in the counsel's letter reads, "Reduced to basic terms, known icing conditions exist when visible moisture or high relative humidity combines with temperatures near or below freezing," and thereby introduces "high relative humidity" as a factor that contributes to structural icing in flight, according to AOPA. Cryogenics aside, the association argues the wording would place anyone flying any aircraft not equipped for known icing in conditions of high relative humidity and temperatures at or near freezing in violation of federal regulations. Unfortunately for pilots, relative humidity is not an item included in either National Weather Service aviation weather, or FAA reports or forecasts, says AOPA. Fortunately, AOPA has no intention of letting the "new interpretation" ripple through the ranks of general aviation and has already brought attention to the semantic snafu via a Nov. 17 letter to the FAA asking that "the interpretation be rescinded."