"Al G" wrote in message
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"Peter" wrote in message
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"John R. Copeland" wrote:

Cold avgas should be no problem, assuming no suspended ice crystals.
Take care to keep your fuel clean and dry.
I often fly in the low flight levels where temperatures can be even
lower.
The cold-soaked fuel flows just fine, including using a transfer pump to
move wing-locker fuel out into the tip tanks.
I've never had any avgas problems at those temperatures,
but cranking the starter against very cold oil has defeated me too many
times.
Heated hangars are my favorite choice.

This is Europe, where heated hangars are a luxury available to the
chosen few

The specific concern wasn't the stuff flowing into the tank. It is
freezing in the pipework, especially in the injection tubes (IO540-C4
engine, in my case) which are very thin and exposed to the full 150kt
airstream.

There have been various cases of avgas freezing in fuel pipes, and the
pilot having to descend all the way down to god knows where to restart
the engine(s). And it's happened to twins too; one pilot I met
recently had to descend (a Duchess) with a dual engine failure from
25,000ft to 2,000ft over the sea, 100nm away from any coast, before he
could restart. The initial temp was -25C.

I've had the "Twin glider syndrome" in a C-340. South of Klamath Falls,
Or., at FL 220, -30C, The fuel flow for the left one started to twitch,
and whithin 3 minutes, the engine quit. The right one followed about 5
later. Tops were about 20,000, and the 340 wouldn't stay on top, because I
had picked up a little ice, so after one quit I had to descend. I got the
right one lit at about 8,000, say 2500 agl, and right after breaking out
VFR. After landing in Reno, a quick drain of the tip tanks, showed
hundreds of tiny ice crystals. The sample look like one of those "Snow
scenes" that you shake up and watch the white stuff settle. Yes, I had
drained all of the sumps prior to takeoff. No, I didn't find any liquid
water, but it was -2C in the hangar during preflight. The fuel truck
checked out as well. Even after fueling in Tuscon, warm and dry, I still
had "snow" in the sample the next day. While in Reno, we sprayed a little
avgas prist into the tank, and immediately drained out almost a cup of
water. After doing this to all tanks, the mechanic said I was good to go,
and I left, with no more problems.

Prist = Good

Prist before the engine(s) quit=Better

It does appear that "Pucker factor" on the pilots seat can extend your
glide. I think we are not counting all available sources of lift.

Al G

Some of the later model Cessna 340/A, 414/A and 421C had "heated" fuel
manifolds. The manifold (or spider) has a reservoir at the bottom that hot
engine oil flows through to prevent this.

Allen