Abstract: The invention relates to a method and an apparatus for determining the risk of ice deposition due to precipitation. According to the invention the measurements of precipitation known so far are combined with measurements of the actual amount of ice deposited from the precipitation. Said measurements are combined in a combination unit that is able to receive further parameter information, eg the amount and type of anti-icing liquid. Compared to previously a considerably more reliable determination of the risk of ice deposition is accomplished, eg on the wing of an aeroplane applied with anti-icing liquid, and so is reliable determination of the holdover time, HOT, during which one can be sure that the aeroplane is free from ice in the current weather conditions.

Abstract: An apparatus and a method for local measurement of an icing factor for atmospheric air containing supercooled water, and wherein the apparatus comprises at least one surface element made of a material suitable for ice in atmospheric air to freeze on, and said surface element having a predetermined surface area, and wherein the apparats further comprises means that are configured for moving the surface element through the atmospheric air at a predetermined rate and for a predetermined period of time, and wherein means am also provided that are configured for measuring the thickness or mass of the ice frozen fast onto the surface element after the predetermined time interval during which the element is moved through the atmospheric air.