Known Icing Condition

cimepilot

cimepilot

Well-Known Member
What is everyone's opinion or interpretation of the definition of known icing? Would an AIRMET or SIGMET forecasting icing constitute known icing? How about a PIREP? Just curious. Cannot get a straight or consistent answer from anyone on this one.
 
One of the reasons you cannot get a straight answer from anyone is because the FAA has historically not provided a clearly defined interpretation of what it means by "known icing" I believe that is changing, and the FAA now interprets "known icing" to mean forecast icing. Of course there is now the issue of "what is forecast icing?" AIRMETS/SIGMETS and PIREPS would be strong candidates for "forecast icing" The difficulty lies in the fact that it is difficult to accurately forecast icing, hence the rather general wording of icing AIRMETS. The FAA has approved the use of Current Icing Potential charts for FSS briefers. They are also working on a Forecast Icing Potential chart but are having a harder time getting the degree of accuracy out of that one.

Flying in visible moisture above the freezing level will ALWAYS introduce the possibility of icing, but I don't think that currently would constitute "forecast icing" That is my best guess from a regulation standpoint. From a common sense standpoint, if you're flying an aircraft that has no anti-ice equipment other than a pitot heater, I'd stay out of all visible moisture above the freezing level. Icing, like thunderstorms, is EXTREMELY unpredictable. Even if the FAA would not violate you for it, doesn't mean that you should do it.

Consistency is not a virtue the FAA has had much success at achieving. As with most things in aviation, pilot judgment is of the utmost importance.

Ray
 
I've always (ok, for the two months I have been flying) taken it to mean that PEOPLE actually know that there is ice. Hence a PIREP would do it, but a ARMET or SIGMET wouldn't. But I do agree with Ray that it is mostly pilot judgment and is arguable either way.

Ethan
 
Well, I'm not a Fed, but I did hear from reliable sources that the FAA considers AIRMETS/SIGMETS to be "known" icing. I guess they figure that if an AIRMET/SIGMET is out for icing that you have been forewarned of the possibility of ice and therefore you "know" that it may exist. PIREPS are for sure "known" icing. I don't think the FAA would restrict the rule to PIREPs only because if that were the case, we could just all stop filing PIREPs until enough people die that the FAA initiates a better rule.
 
That's the way the FAA used to enforce it....someone had to have had a personal experience with the ice in order for it to be "known". However that's a very hit and miss way of finding out about icing, so I believe now "known" means "forecast" and that forecast includes AIRMETS and SIGMETS. Who made the policy shift and when it occurred, I have no idea, and you'll probably still get differences of opinion depending on who you talk to.

Ray
 
I got yelled at by my lead instructor for going up into visible moisture below freezing with an AIRMET out, even though all the PIREPs (several of them, we operate a large fleet) for the past 3 hours were saying "IC = NEG"

The way he explained it was:

Is there water in a cloud?
Is the temperature below freezing?

If there is water and freezing temps, you can expect ice.

So now my policy with students is a temp below 32 plus visible moisture = no go, and i can justify it instead of using mushy stuff like "well its a grey zone, some people say we can go and some say we can't"
 
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