And what is the likelihood of electric thermal (Thermawing) type STCs coming to the market?
I fully support that idea... and had a discussion over the idea down the pub with a fellow pilot on the same issue... but we couldn't seem to get figures that would make it viable from an energy consumption point of view... Obviously there were a few WAG assumptions in there, but we did not believe that it could run off of a standard electrical fit because of the energy transfer needed to melt rime ice and you would need to bolster the electrics up to retrofit. If there was a second alternator that ran it directly then it seemed to work, but the market of aircraft with second alternators is very small...
I had thought, also about, a retrofit rubber boot for light aircraft along the leading edge... I think there is some technical merit in that, but the costs for certification and the potential uptake rate given that most of the GA fleet is VFR would mean that it doesn't (yet) make business sense. Maybe it is time to look at it again, and in more detail.
So currently these ideas to take over the world are on the shelf... but if you want to start a company to build either and the laws of physics/economics work in our favour, I'm interested :D
@italianjon: such a system has been available for a few years, it's called Thermawing.
@Achima cool, I never knew - learn something everyday. That's pretty much exactly what we were discussing. Seems our calculations may have been right (even after a few pints of beer) as all the aircraft types it is certified for are dual alternator.
I would imagine that system would also only be good for metallic airframes. Composite might be ok depending what they are made of. Plastics I assume are no go.
Would that system ever get EASA approval?
Why not? It was the original system for the Columbia 400 and after some initial problems (delamination comes to mind) gained a bad reputation as so often with innovation in aviation. After its acquisition of Columbia, Cessna switched back to a traditional TKS system. I don't see anything fundamentally wrong with the system and I if it was an available option, I would very much like to have it fitted to my aircraft.
You an get a TB20 with full TKS, a friend of mine in Austria flies one. There are TKS systems available for Cessnas, although I have never seen one in Europe.
A full TKS system for C182 is STC'ed in Europe and there are several planes flying with it. However, it adds weight and take up half of the baggage compartment. Also the TKS fluid is quite messy to deal with. The electric system would be very elegant.
The thermowing looks like a great system. The benefit as far as I can tell is that the only running costs are really the slightly higher fuel consumption you would encounter when the alternators are working hard... but the additional weight/drag would be negligible; if fitted to a mid-drag airframe (say Grumman territory)
That's what got us talking about it in the first place. The other idea I mentioned was to fit rubber boots along the leading edges of the wings, stabilisers and tail plane, and then run those from a compressed air system, which could either be charged on the ground or fit a small pump to maintain the pressure (think pneumatic brakes on buses)... but the additional weight would mean a permanent penalty.
Granted the higher end GA IFR machines such as TB20s do have good systems fitted. When I spoke about these ideas it was during my IMCr training, and now I can fly IFR (albeit in UK airspace) it would be good to have access to something a lower end PA28/C152/C172 with the ability to fly into known icing.
As 172driver said machines like this are few and far between in Europe, and TKS seems to be the solution, but not necessarily of choice, for EASA-Land.
I think unfortunately the cost of known-icing fitouts means that only higher end GA singles get fitted with it and I assume almost nothing in the rental fleet would have it.
It's indeed true that I avoid icing conditions 
But I do it by
My experience is that on a flight of any significant length, IMC, 0C to -10C, icing is virtually guaranteed. The question is how much... I have had a few mm after an hour and also I have had 30mm in 5 minutes in a perfectly smooth stratus! There is no way to forecast it in any useful way.
Some other pilots disagree and bore through icing conditions happily, and occassionally write up some pretty scary stories.
I have a TKS de-iced prop which I think is brilliant. It was about £3k (factory option) and also protects the front window. In my "30mm" incident there was no ice on the window. I switch it on every time in IMC below 0C.
I can get TKS for about €40k but it drops the payload about 50kg. It's worth having if you want to fly through frontal weather, but the stuff will run out after 1-2hrs and it is very expensive - of the order of €200 for a refill (if you use the stuff they actually specify). I paid €200 for 20 litres of the fluid for my prop TKS but in that it lasts for ever (get through about 2 litres a year).
The Thermawing system uses a 2nd huge alternator, which from memory is 50V/75A or something like that. They had problems with the elements overheating and burning out. I recall Air Touring were playing with it during their brief "Lancair dealership" period (till Cessna took over Lancair's certified part and terminated AT's dealership) and from memory there was some dispute between them and Lancair as to whose fault it was, with Lancair claiming AT wired it up incorrectly. It didn't go anywhere in the end. It definitely does work to protect the leading edges but there were concerns about runbacks freezing further back on the wing. Airliners with bleed air heated wings get around the runback issue by making the leading edges so hot they vapourise the droplets.
The extent to which one needs to penetrate icing conditions depends largely on one's mission profile.
If you fly for pleasure then you can pick non-frontal conditions and those are usually (~95%) OK to climb through a layer, and if you make sure the surface temperature is about +3C or warmer then you have an escape route anyway from anything unexpected.
The satellite IR images can be used to determine, with a high degree of reliability, if VMC can be maintained enroute. Some notes here. I have used these for a few years, together with tafs and metars and very little else, and have never had an "eventful" flight. This method has never let me down. But then my despatch rate is perhaps only 75%.
However this method works only for a plane which can climb to FL180 or so, because the IR images are quite inaccurate and if your ceiling is say FL120 then you need to pick altogether better weather. So choosing a TB20 all those years ago was most fortunate... but most 250HP planes can get to FL180-200 and FL240 or so with a turbo.
If you fly on business then you need more serious hardware. I can't comment from experience but I think full ice protection is a must, but if you fly through known-convective weather then you might fly into something nasty so radar is a good idea. A stormscope (I have one) picks up a lot of stuff but misses a lot of other stuff which would be really nasty in terms of icing.
Flying on business can be tricky anyway because one can't really use light piston GA for formal customer visits, due to not turning up not being an option, and due to the usual need (in the UK especially) to conceal your expensive hobby from your customer However a lot of "business" flying can be done visiting suppliers, exhibitions, conferences, etc.
I think the VMC on top method won't work well if you try to outclimb warm fronts because they often have tops ~FL250 and oxygen is impractical up there. This leads to a PA46 being the entry level for that sort of thing. This is also why I think the only logical upgrade from a TB20 is something like a PA46 Malibu or preferably a PA46T (Jetprop), and not another unpressurised single like an SR22 which is not more capable versus weather in reality.
If you don't fly on business then you probably won't want to fly somewhere if the weather there is going to be crap. Even walking around a nice city like e.g. Prague is miserable in the rain. So it tends to take care of itself.
Flying on business can be tricky anyway because one can't really use light piston GA for formal customer visits, due to not turning up not being an option, and due to the usual need (in the UK especially) to conceal your expensive hobby from your customer However a lot of "business" flying can be done visiting suppliers, exhibitions, conferences, etc.
Well you can use one for business (ignoring the hobby point) if you have full known icing protection and still accept a small number of flights may have to be cancelled. That is what I am doing now. But I have heated prop, windshield and boots and can fly at FL250. As Peter says, even with ice protection if I had to fly down at FL120 there would be some flights I have done so far that I would have cancelled due to not wanting to sit in an icing layer for hours (even if happy to go up and down through that layer).
