Janitrol – I dont know why this arent more common.
There is never a lack of heat, in fact toasty hot, and it is the perfect solution especially when the engines arent in front of the cabin.
The answer to fuel icing in petrol engines is 1% isopropyl alcohol. When bought in bulk, this has a similar cost to Avgas. I took 40 (or was it 60?) litres with me on the North Pole trip. It is relatively easy to deal with.
In jets, the answer is Prist. It is a different beastie and it unpleasant and quite difficult to work with, though you need much smaller quantities.
I have no idea about paraffin burning piston engines, I am afraid.
Janitrol – I dont know why these aren’t more common.
There is never a lack of heat, in fact toasty hot, and it is the perfect solution especially when the engines arent in front of the cabin.
They are terribly unreliable.
I do have the advantage in one of the PA31s I operate of an auto reset circuit breaker, but most of them need to be reset on the ground, and they pop all the time.
Timothy wrote:
The answer to fuel icing in petrol engines is 1% isopropyl alcohol.
That’s interesting. Would this prevent icing in the fuel servo too? I’m a little concerned to have discovered that this can occur as high as -5C. It sounds like a rather serious issue for winter flying…!
A search here on PRIST digs out various threads. You can use it with avgas too, and the advantage is that much less needs to be used, so it is popular with ferry pilots. On long trips IPA has to be carried in huge amounts. The point is that it is not avgas that freezes; it is any water in it. I carry 2 litres of IPA (it is a very useful cleaning fluid) and would pour half a litre into each tank if filling up at a place where I suspect the avgas has been sitting around for a long time – like a lot of airports in southern Europe (where most GA operates “off grid” and the bigger places get little traffic – example) and I am expecting a high altitude flight afterwards – notably a certain airport in the Adriatic whose avgas turned out to contain a lot of water in 2014 (they changed their practices after that).
Most Janitrol owners seem to complain about them continually, when they have them, and then even more when they have to send them for an overhaul 
There is also their fuel consumption which is normally regarded as insignificant on the old large twins but would not be quite so on a smaller plane.
Would this prevent icing in the fuel servo too?
No. That is just moisture in the intake air (needs to be IMC) freezing up the fuel servo sensing pipes; see that thread I posted. It needs an OAT of around -15C. There is a delta T of about 10C in the intake (documented in that thread) which results in -5C seen at the fuel servo inlet. Maybe due to a geometric coincidence the DA42 has the same issue.
Understood. Thanks.
Timothy wrote:
[Janitrol circuit breakers]……most of them need to be reset on the ground, and they pop all the time.
By that you presumably mean the overheat protection cut-off?
I found that keeping the heater off on the ground or, if you must run it, with air fans on “high”, and turning it off as part of the of the approach checks, significantly reduces the rate of that happening. That might not be realistic in very cold weather, though.
Timothy wrote:
They are terribly unreliable.
Cant recall the last time it popped or stopped working, so perhaps very lucky. It is brilliant I always find, instant heat and as much as you want. Something vaguely similiar is used on boats and in lorry cabs (Eberspacher). I hear similiar unreliability issues from time to time, but I have never had a problem.
Cobalt – you are correct, and that is the usual reason. Fan always on, and vents open and all off as part of landing checks. I havent had a problem on the ground either.
It varies a lot. On some aircraft, like the Chieftain I currently fly, and my Aztec, it pops all the time, on others it’s more reliable.
And it’s not just a question of maintenance. They get returned for factory overhaul very regularly (every 24 months?) and you can report that it pops all the time and still it comes back the same.
Surely that is a muppet “overhaul”, or there is a mistake in the IM and the CB is the wrong rating. The CB is just for the fan, no? Or is it some other kind of “trip”? We put up with so much of this crap in GA…
