1. I appreciate it depends on the adiabatic rate etc. but has anyone been "iced" before (and was it slow and steady or fast and terrifying) and presumably, you just declare a "pan" and get down sharpish?
Airframe icing (as distinct from carb icing which is a very different piece of physics) happens when you fly through supercooled water droplets (which basically requires flight in IMC). These droplets can exist between 0C and about -15C, possibly a bit lower in convective clouds.
I don't think the adiabatic rate is related to this.
The extent to which aircraft performance (wing lift, drag etc, and prop efficiency) is affected depends very much on the aircraft. Old designs tend to be less affected, whereas something like a Cirrus are reportedly strongly affected.
The existence of supercooled water is highly statistical. You could fly along for 10 mins and get not a drop. Next 10 mins, you pick up 5mm (which is usually enough to impact performance). In extremes, in convective cloud especially, you could pick up inches in minutes (freezing rain e.g.). Thin stratus cloud is normally OK for a bit...
Strategy depends on the aircraft deice equipment and varies between pilots, from "never touch IMC below 0C", through "OK to climb/descend through it, but never fly in IMC enroute (that's me; I will climb to FL200 if necessary to stay above rising tops), to pilots who always go (
some of whom fly deiced planes) but only occassionally write about it...
2. Flying IFR this of year generally, do you just simply avoid the clouds as much as possible? If so, what do you do if you ask for vec ILS at your destination which then takes you through clouds?
You are descending so should be out of it pretty quick.
But yes, the winter is a problem because on cold days your primary escape route (a descent below the 0C level but without hitting the ground etc) is closed off, and whatever ice you pick up you have to land with. That's the price you pay for not having a jet
3. Forecasting cloud tops - is it possible? Other than Synoptic forecast, do you just assume cloud tops are out of your reach - period?
There are various methods but none are that great. The UK Met Office does not release its 3D model other than to commercial weather repackagers so one has to turn to the U.S. run GFS model e.g.
here. You have to use data like Soundings. But tops forecasts are rarely accurate; let's say the tops are forecast for 6000ft, you should assume they could be at 10000. I will scrap flights if the tops are forecast above 16000 because my economical ceiling is 18000 and max is 20000.
Occassionally, especially in a large high pressure area, the tops are accurately forecast, and the layer is very thin e.g. base at 1500ft and top at 2500ft. But usually in those cases you can see blue sky in holes, and then it's obvious.
Generally, in warm front conditions, you can forget it because the tops will be say 25000ft and the climb in icing conditions will be too long/risky unless you have the full deice kit. In those conditions you have a fairly uniform sky colour - indicative of a great thickness. But - frontal conditions aside - most clouds can be climbed through because the layer is so obviously thin.
In practice, in the UK, due to controlled airspace bases, cloud tops are normally too high for VMC on top flight to make sense unless one has an IR.
imtaylor - I will send you an email with more stuff.