My point is and there I support also Peter…What is known icing?
In my book “known icing” is either forecast icing, or visible moisture with OAT in the -20°C to +3°C temperature range. If you encounter icing which was not explicitly forecast, think it would be very difficult to argue that there was no “known icing” if flying into clouds above the 0° isotherm.
I agree with the above. Known icing is visible moisture (clouds mostly) with temps below 0. Icing below -20 is possible but not so common.
I (used to) have to do what Peter often advises against (with good reason if flying for pleasure) by flying in icing for hours at a time. Doing this I find one of the easiest ‘get out’ thresholds is airspeed to maintain level flight. For example if I was normally cruising at FL100 and 160kias and after an hour or more in icing found that I was doing 150 I would know I had picked up a bit of ice, if it further reduced to 140 I would know it is getting worse etc. It takes a bit of experience and trialing to work out what your get out point if for a specific aircraft.
For example if I was normally cruising at FL100 and 160kias and after an hour or more in icing found that I was doing 150 I would know I had picked up a bit of ice, if it further reduced to 140 I would know it is getting worse etc. It takes a bit of experience and trialing to work out what your get out point if for a specific aircraft.
You should see the ice on the leading edges way before it shows up on the airspeed.
Then you can monitor it continuously.
A drop from 160 to 140 is probably a lot of ice, and things will go downhill fast after that.
Interesting. Actually, on the few occasions that I have encountered light icing, the first indication is a 5kt drop in TAS (DA40).
There is an anti-slip ‘mat’ just outside the pilot window: it has a sharp front edge – this is the first place that ice seems to start gathering, so I look there with the drop in TAS.
This was light icing, just below freezing in solid stratus IMC. Dropping by 1,000 ft the air temp went up to +1C and within a few mins the ice disappeared and the airspeed came back up.
That is interesting the worst ice I ever saw was coming back from Eire in very similiar conditions but a little higher. It was in a DA42 and hadnt anticiapted any icing, ducking under the airway as it happened and back into IMC. Running the fluid at full flow dealt with the ice but it was sudden unexpected and built up at an alarming rate. In hindsight the fluid should of course have gone on before ducking under but I had neither anticipated the amount of ice or that the tops had increased east bound so the base had become a few thousand feet more and getting close to being a problem without oxygen. It would have been a very unpleasant experience without fluid as I seem to recall the bases were low and I suspect I may have had a problem getting out of the icing.
On the plus side I would never have set off either in a single or without the anti-ice, on the minus side I would now start using it much sooner and more fully appreciate that a cold laminar flow wing and icing conditons are not happy companions.
Yes Peter indeed these soundings are a good indicator but still I would love to have Pireps as in the US (nobody was in the air over that area …but okay… 
) I think on more laminar airfoils the speed drop is much apparent e.g Mooneys, DA40’s, Cirrus…I flew a couple of time a hi-performance glider through a rain shower and this changes your glider into a flying brick. On another occasion I flew my Motorglider through some rain at 8000 Feet in Summer over the Austrian Mountains in positive temps and the bird was almost unable to maintain altitude (speed drop from 100 kts to 70 kts)
That’s why I would love to be able to install a hot prop as the Beech wing can take some ice better then a Mooney or even Cirrus I reckon. The prop keeps on pulling the thing forward to maintain lift, thus, buying you some more time to decide on the options (climb, descent, turn back etc..)…for sure I don’t go over mountains in IMC in clouds close to 0 degrees (that would indeed mean known icing, as Aviathor mentioned.(though practically sometimes could mean it was NOT known (forecast etc..) but a real time KNOWN experience… 
) .
Well I realize that as a consequence, this may well have been the last flight till Winter is over over these distance, unless a super Hi Pressure system with clear skies are predicted however two weeks predictions are not stable and would mean that I would need to leave the aircraft behind..Hangar issues, possibility of snow on RWY for weeks, etc…
In the above story, If I would not have been able to go on top before reaching significant terrain, then a return to my Dep AD was planned with a lower altitude >above 0 Degr level ..
What stroke me that there was no significant drop in temp btw 3000 and 8000 feet….Which I contributed to maybe some inversion over that area…
Anybody know a FIKI C210 which can handle ski’s…
You should see the ice on the leading edges way before it shows up on the airspeed.
Then you can monitor it continuously.
A drop from 160 to 140 is probably a lot of ice, and things will go downhill fast after that.
Ok, I should have given more detail perhaps. This is flying an aircraft that has boots, albeit not very effective ones. It was not uncommon that we would be firing the boots but over a period of time still seeing an airspeed decrease, simply because of the non deiced bits of the aircraft getting more ice. The other thing was when flying at night, it is much more difficult to detect ice, even with a wing inspection light the artificial lighting can make it difficult to see things, especially when flying in precipitation with strobes going as well.
Of course you should visually be able to see ice build up on certain areas in certain aircraft, but I personally found that airspeed took some of the judgement out of it.
I ran the Wyoming skew for Budapest 12Z and it shows for yesterday a significant spread above 2000m, though the reality was it happened almost 1000 m above that…. The temps show also around 5 degrees which where a bit lower. It shows though indeed not a significant drop in Temps when climbing…Looking back that I took off at 10.45 utc and the 00Z skew shows no break at all till 7000m ( a front passed during the night) a higher ceiling maybe be expected…but okay that’s forensic Met Service..
My understanding is that icing is not possible below -15 C. This is what I read severeal times before. Can one trust on this ? Has anyone ever experianced icing below -15 ?
On a long flight over the alps last summer I encountered some rime ice while climbing through broken stratus at OAT of -3 to -6 C. While climbing higher the ice disappeared below -10 C, I don`t know why. While cruising in a solid stratus at FL 220, OAT -18C for one hour there was no ice at all on the plane.
I have experienced moderate icing at -25C. Don’t believe the books!
I imagine that the icing I got (which was entirely on the windscreen) happened because the outside surface of the perspex was comparatively warm.
