A forecast and warning scheme for aircraft icing is presented. The scheme is based on results from in-cloud measurements with an instrumented aircraft during an icing research campaign in Southern Germany in March 1997.The flights were part of the European funded project EURICE on aircraft icing. The aircraft was equipped with two optical scattering spectrometers (FSSP 100-ER, range 5-95 mm, FSSP 300, range 0.4-20 mm ) to measure drop size and an optical array probe (OAP-2D-C, range: 20-750 mm) to determine shape and phase of the particles, together with a temperature sensor and a Johnson-Williams liquid water probe. Ice accretion on the wing and on an exposed cylinder was documented with video cameras. Measurements with optical cloud probes and the video documentation of ice accretion on a cylinder show the existence of supercooled large drops (SLD) in the size range up to 500 mm with related ice accretion rates of maximum 4 mm/min. The SLD formed in convective cells embedded in a mixed-phase stratus cloud through the coalescence process in zones of high liquid water content near cloud top. Conditions which favour the development of SLD in this situation are: (i) vigorous convection, advecting high amounts of liquid water,(ii) relatively warm cloud top temperatures suppressing the natural glaciation of the cloud, (iii) mixing with ambient saturated stratus air, avoiding the usual reduction of liquid water content. Embedded convection defines one situation where SLD are likely to occur. A forecasting and warning method for this situation is presented which together with conventional weather data is essentially based on radar and satellite observations. The scheme is part of the ADWICE system (Advanced Diagnosis and Warning system for aircraft Icing Environments) which is currently under development
The 8th Conference on Aviation, Range, and Aerospace Meteorology