A new interpretation by the FAA of “known icing conditions” could ground GA aircraft during the winter, alphabet groups warn.
The new interpretation says that “high relative humidity” constitutes known icing conditions, so pilots in high relative humidity conditions when the temperature is near or below freezing must fly an aircraft with deicing equipment.
The restrictive interpretation is not consistent with other FAA publications, which state that visible moisture, along with freezing temperatures, is necessary for structural icing in flight.
High relative humidity is not visible, claim GA advocates, who promise to challenge the new interpretation.