Fortunately our airport is very
ideal for flight testing, with 3 separate, long runways and a relatively low
amount of traffic. I try to do my flights when there is little traffic and I
always maintain gliding distance to a runway. One of the benefits of
the turbocharger and the constant
SNIP
I think that by ducting cool air through a fuel
cooler at the inlet to the shroud around the fuel components, it should
adequately cool the fuel without significantly heating the cooling air
allowing plenty of cooling for the pumps and filters. I just have to find a
small enough cooler to do the job. I also use a gascolator on one of my fuel
lines, which I'm considering removing. I have water drains on each tank and a
sump with a drain on my header tank, so I've never seen a single drop of water
when draining my gascolator.
How large is your cooling duct to your shroud over the
fuel pumps? Where do you have your inlet for this cooling air? I
originally considered ducting from the rad inlets, but I don't want to be
stealing any of this cooling air, so am considering a small NACA duct on the
side.
My shroud is fed
by a 2" dia scatt hose that route air from a small NACA scope (about the same
size as on the side of an RV aircraft) the duct opening is under the cowl
about 2/3 of the way back from the front. I concluded that during high
power climb would be when I would need the cooling air the worst. Seems
to work for me. Interesting, I have had two power out events - but,
neither due to fuel/vapor lock {:>). INterestingly, its not high
power that is generally the problem. At high power, you generally do not
recirculate much fuel, much more of it is being consumed and replaced with new
fresh cool fuel. Its after you throttle back after a hard climb and stay
a lower airspeeds like in the pattern, then much more fuel is recirculated
back to the headertank (and bringing with it the heat build up).
Should it
happen again, I would suggest opening the throttle wide open. This would
tend to quickly get rid of either the fuel vapor or heated fuel as the
injector remains open longer. The engine would of course, cought and
sputter until the fuel flow returned to normal, but it just might get enough
cool fuel back into the tank to help. On the other hand, I believe you
have a much larger header tank than I do, so if your fuel got to that point,
it would take much longer to restore conditions than my less than 1 quart
header tank. Quick to empty and quick to fill.
Leon has sent me an off-line reply with a few additional suggestions as
well. I'm considering replumbing the header tank vent line (which is normally
closed), back to one of the wing tanks, instead of to the vent line header.
This would allow the boost pump to continually recirc cool fuel to the header
tank rather than just pressurizing it. This would also allow me to close this
vent/recirc line when I do want to pressurize the header
tank.
Sounds like
a reasonable approach.
The reason that I originally opted to use a header tank
was it seemed at first to be the simplest way to manage 6 fuel tanks without
the hassle of returning to a single tank and transferring fuel as others have
done. I've now found that it requires much more management than anticipated
and is becoming much more complicated. If I was starting over again, I
would certainly reconsider this idea.
That is also why I
went the same route. Simplicity and only one valve to be concerned
with. But, clearly there are risks associated with it. I have over
200 hours and never had the engine quite (due to heated fuel), but my smaller
header tank might mean there is less of a resovior of heated fuel and vapors,
so corrective action may bring quicker results. Just some
thought.
Sounds like a
great airport for test flights!
Stay alert out
there!
Ed
Anderson