Sjoerd’s S22T incident looked very similar but to me more like a turbo/induction issue.
It may apply to any aircraft where the air inlet is bigger than the fuel servo inlet i.e. you get compression heating.
If you google “fuel servo icing” you get practically nothing!
Do you really think you have made this discovery, now, in 2015? No, it’s a phenomenon that’s very tightly restricted to certain installations (if it does exist at all).
Peter probably is the only one taking the normally aspirated TB20 to FL200 so he could have discovered a design flaw that nobody has reported yet.
FL200 is irrelevant. In winter, you can easily get -15C or -20C at FL100-150 – well within the normal operating range of the TB20.
Oh wait – I forgot… almost nobody flies in winter anyway and almost nobody often flies above FL100. Sorry about that.
Peter probably is the only one taking the normally aspirated TB20 to FL200 so he could have discovered a design flaw that nobody has reported yet.
I have not heard of anyone else with a TB20 reaching FL200 or even the FL210 I once did, but that isn’t the main issue because one can get the relevant temps lower down. There are numerous reasons why a serious issue can go unreported (unreported openly). A lot of it is self-interest… for example some people don’t want to talk openly about issues in case they want to sell their plane. I couldn’t care less because I have no wish to sell mine, because the “lowest” upgrade (worth having) for it would be a Jetprop / Lancair Evolution and I am not ready for that for a number of reasons. And any buyer with a brain will rather understand the product’s known limitations.
However, it is rare to find the lower region mentioned i.e. -35C or so. I did once see -38C at FL190 but that (ISA-15) is very rarely seen by the relevant aircraft type community.
Plus, you have to be in IMC.
If you google “fuel servo icing” you get practically nothing!
Easily explained by the above.
Also a great deal of stuff is not on google. Firstly, almost everything before about year 1995 is not on there, unless it appeared in publications which remain open, and most periodicals are closed-access. In my 1st company, 1978-1991, I designed maybe 100 products and only 1 or 2 of them google. The “world according to google” didn’t start till very recently. Plus, google ranks info severely according to how many hits it is getting. Obscure stuff doesn’t appear unless you hit more or less the exact phrase. Plus, indexable info didn’t start appearing till c. 1990 with Compu$erve forums (which AFAIK were never opened for google indexing) and c. 1995 with the rec.aviation.* Usenet groups which were good but had only a small participating community (especially rec.aviation.ifr).
Also, it is highly unlikely that anybody in the GA business would have done these measurements during certification. Most things are done a certain way because they have always been done a certain way.
almost nobody flies in winter anyway and almost nobody often flies above FL100. Sorry about that
What country is that in? I know a lot of people (with IRs mostly) who do both.
Sjoerd’s S22T incident looked very similar but to me more like a turbo/induction issue.
Could be but are we ever going to find out? The aircraft he was flying is up for sale.
It happened twice to you and the weather conditions were not highly usual if I remember correctly. That more points to either a fault in your TB20 or maybe the TB20 line in general but it’s very unlikely that there is a general problem with fuel servos icing up. It would be all over the internet — I don’t believe in any cover-up conspiracy theories…
Peter wrote:
I have no wish to sell mine, because the “lowest” upgrade (worth having) for it would be a Jetprop / Lancair Evolution
You would be surprised how much more capable a SR22T is 
Or a Malibu.
Here is the air inlet on the TB20 – this is an old pic from c. 2001 but they are all the same, right back to 1982 or whatever
The inlet is about 15cm x 25cm – the standard Brackett filter used all over piston GA. You can see how the gas gets compressed in the reducing cross-section
Can anyone contribute similar info for other aircraft types?
There are only so many ways to configure a non-turbo installation for an IO540 or similar engine.
Peter wrote:
The inlet is about 15cm x 25cm – the standard Brackett filter used all over piston GA. You can see how the gas gets compressed in the reducing cross-section
The air pressure at the manifold is below ambient pressure which means there is expansion, not compression.
The air filter (Brackett is a possible option) is attached to an air box.
The air box is equipped with an automatic alternate air door (spring loaded).
The air box outlet is attached to the engine intake.
Pre-1990 M20J are also equipped with a direct air inlet (no filter) in the cowling, opened manually from the cockpit, which goes directly to the engine intake (through the air box).
This is the only case of engine stoppage in cold weather environnement I’ve heard of.
