Severity Definitions MET

There are four categories of icing but only the main three are really of interest for the exam: Trace, Light, Moderate and Severe. The best way to learn these questions is to look at key language for each level and think about the differences, rather than trying to remember the whole thing.

Trace:

Ice becomes perceptible. Rate of accumulation slightly greater than rate of sublimation. It is not hazardous even though de-icing/anti-icing equipment is not utilised, unless encountered for more than one hour.

Light:

The rate of accumulation might create a problem if flight in this environment exceeds one hour. Occasional use of de-icing/anti-icing equipment removes/prevents accumulation. It does not present a problem if de-icing/anti-icing equipment is used.

Moderate:

The rate of accumulation is such that even short encounters become potentially hazardous and use of de-icing/antiicing equipment, or diversion, is necessary.

Severe:

The rate of accumulation is such that de-icing/anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary.