I've just read of another near-death experience in the last US AOPA mag.
The weather briefer reported a fast-moving cold front .... as we crossed Oklahoma, the cold front pushed across our route, bringing a report of possible icing in northwest Arkansas .... a quick weather briefing disclosed that icing on the route home was at higher altitudes ...
I wonder where this idea of "ice forecast at X so Y should be OK" comes from? The fact is that you can get icing in any solid IMC between 0C, and some lower temperature which depends on the convection but which is usually -15C or colder. And if you stay in the stuff for long enough (any likely enroute sector) you will get ice.
IFR pilots continue to struggle to get meaningful forecasts of IMC enroute at a given altitude, and sites like GRAMET deliver something reasonably usable. But this is quite recent and anyway almost nobody uses them. People still talk about "icing forecasts" or "icing SIGMETs". Maybe I am missing something but to me that is all bollocks. Where does it come from?
The German Weather Service (DWD) offers icing forecasts. This is what pilots consider to be the "icing forecast". Other sites have similar charts. The algorithm is very pessimistic, you better do your flying in MS Flight Sim if you make your decisions based on this forecast.
The bottom line is that we are not able to provide meaningful forecasts about icing. Whether it's DWD or GRAMET, it's highly unreliable when temperatures are below freezing. Regarding your PIREP, I think one can say that it's generally a very stupid idea to cross a cold front in a GA airplane and Darwin tends to filter out those kind of pilots over time.
The bottom line is that we are not able to provide meaningful forecasts about icing
Exactly my point, so why are these bogus forecasts being offered and also, apparently, feature in flight training?
I have seen plenty of icing charts for Europe (the USAF German Sembach site used to run them) but never saw anything which would not be immediately obvious from the MSLP chart i.e. a banal "here is a nasty looking front = there will be icing" approach.
Peter, I fully agree with you here. I never understood how people do rely on either no ice being forecast (despite IMC sub-zero conditions) and ice being forecast.
I understand the DWD charts mostly as that: they analyse where (and at which altitudes) you will likely encounter a combination of visible moisture and sub-zero temps and in these cases they show an icing warning for these areas. This, even though possibly a little pessimistic, is IMHO the right approach.
I have said it before and will repeat it: my experience of over 12 years of IFR flying in SEPs (below FL200) has shown me that in visible moisture, below 0 degrees, one will have some ice in maybe 95% of all cases. I understand orher people have different experiences (for example Aeroplus who even happens to fly the same airframe that I do...), but again, that is my personal experience, of over 12 years of IFR.
The advantage of having black boots on the wings is you can easily see ice build up. I agree that you will almost always see something in cloud in the minus single digits range. Usually just looks matt vs shiny. Sometimes it is lines running back like frozen drips. Equally, the leading edge of the horiz stab will usually pick up a little line of ice in those conditions. In those conditions we wouldn't do anything about it (deice etc) but it would be almost impossible to see on a white wing.
What is the point being argued here?
That we should have no icing forecasts at all, because they are erroneous and may cause a pilot to take off believing he/she is safe from the stuff while it may be lethal? Or, that they are meaningless so let pilots make their own judgement and fly at their own whim, which they do anyway?
Flying in weather conducive to icing without having the gear to protect you is not very intelligent, imho. There are times when a preceding aircraft reports moderate icing while the guy behind experiences nothing, or vice versa. It just isn't a very predictable phenomenon.
The advantage of having black boots on the wings is you can easily see ice build up.
Unless it happens to be clear ice. This has caught me once or twice, thinking there was nothing until I cycled them to check...
Don't know others points but mine was that you should essentially assume icing is likely in visible moisture between 0 and -15.
Unless it happens to be clear ice. This has caught me once or twice, thinking there was nothing until I cycled them to check...
Agreed, but I was more making the point that some aircraft may well be accumulating ice (albeit perhaps a small amount), without even realising it.
Like Krister L, I struggle to get the point. You can assume that there will be bumps in any Cu, but don't you look at the CAPE and the lifted index before you plan a flight.
The US has much more sophisticated modelling of icing, e.g. in the CIP charts
I wouldn't bet my life on any cloud below zero being ice-free. Nor would I trust any cat not to bite me, though I'd appreciate a bit of information on whether it's a tiger or a tabby.
but don't you look at the CAPE and the lifted index before you plan a flight.
I've heard of those but have never met anybody using them. What are they and how would one use them, practically, to tell if a given layer of IMC will contain SLDs?
the CAPE and Lifted-Index are in our weather app and give you information about the potential convective energy in the cloud layer enroute. It is very helpful and will give you some good information, next to other information. We have the CAPE and Lifted-index values for all locations worldwide as a forecast of up to 24 hours. After that, the forecast is less reliable.
That said, I noticed in a post above that boscomantico mentions my IFR flying in the same airframe. Just to be sure, I fly through some frontal weather but not all and I do experience ice when flying in sub-zero clouds, but can cope so far with these situations and agree that it is virtually impossible to correctly predict ice in clouds.
To me, it seems that if the clouds are CBs or convective clouds (think CAPE and Lifted-Index, CBs forecasted) then there is more likely to be ice in the clouds than with stable stratus clouds, but that is no guarantee that there will be no ice in stratus cloud layers as Peter once already mentioned.
Bottom line is that we all do our best to look at the weather forecasts and then make our personal decision to fly or not, depending on personal factors (how much risk are we willing to take basically) and the equipment (FIKI aircraft of not).
