A Rapid Method of Estimating the Severity of Icing: Calculations That Give a Definite Evaluation of the Most Severe Conditions and Approximate Figures for General Rate of Catch Available to Purchase

A method of three dimensional plotting is adopted, where the ROC at any station on the wing is plotted vertically on a base representing the maximum icing conditions (FIG. 5). This allows a rapid estimate of the ROC at any icing condition. Also, by plotting the isothermal lines on the base and on the surface representing the ROC (FIG. 10), an immediate estimate of the maximum rate of heat supply at a given temperature is possible. (Since the amount of heat lost by convection is constant along an isothermal line.) By plotting those maxima against the ambient temperature, the most severe icing condition may be established. It is then sufficient to consider only the above condition in the design of the de‐icing system, all other combinations of the icing parameters producing a less critical heat requirement. It has also been found that the relation between the drop size (d) and the ROC (at any given speed between 150 and 350 f.p.s.) is almost linear for drop sizes between 10 and 40 microns. (cf. FIG. 6, REF. 3.) A general relation, of the form: ROC=Am(d‐D) is then established between the rate of catch, the liquid water content and the drop size. By using graphs giving the variation of the coefficients ‘A’ and ‘D’ with speed and position along the wing, it is possible to have a complete estimate of the severity of icing in a small fraction of time formerly required to complete the calculations.