Page 16 - Volume 15 Number 1

The Supercooled Large Drop (SLD) field for FIP will remain an uncalibrated field for now. Any SLD potential over 0.05 (on a 0 to 1 scale) is included. On ADDS it will appear as a hatched, red-hatched area that is overlaid on the FIP severity field. On this image taken from the experimental ADDS Web site you may notice what appear to be contours in the SLD field. That’s not the case. You are actually seeing the severity field showing through due to the transparency in the SLD overlay.
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overlay on the FIP severity display.
CIP’s Transformation
If you were paying close attention to the ADDS icing tools back at the end of 2006, you may have noticed that CIP went rather quietly through this same metamorphosis from a potential field to a probability field. The old potential field wasn’t calibrated, meaning that it was not
In other words, if there’s even a remote possibility of supercooled large drops, it’ll show up as an
a true statistical probability. The term “likelihood” was used instead of probability. In other words, it attempted to quantify if the environment was more or less poised to produce structural ice.
At that time the colors were contoured at 95, 85, 75, 65, etc. However, for CIP’s transition from an icing potential to an icing probability, the developers found that when calibrating it, they could not statistically justify probabilities in excess of 75 percent. As a result, the highest probability (ordinarily shown in red) indicates a 75 percent or greater chance of icing. In the end, most pilots would agree that there’s really is not that much difference between an icing event with a 75 percent probability versus 95 percent probability.
14 • ­TWIN & TURBINE
JANUARY 2011