Frans Veldman a crit :
> Before I go crazy completely, let me ask a question. Is it possible, that
> while
the pumps are pumping 130 liters per hour through the system, that the
underpressure
on the suction side of the pumps just lowers the boiling point of the
fuel so much that the fuel starts "boiling"? Maybe it is just normal to see
all these bubbles dancing around in the fuel filters? If anyone has noticed this
as well, please let me know, it saves me a lot of time chasing "ghost" air
leaks. Temperature at the moment is a nice 20 Celcius and the airplane has been
standing in the sun for a while. (Yup, I know that sun isn't good for composite
airplanes, but messing with the fuel in a confined space isn't very good for
me).
Frans,
You're spot on. And not crazy at all, by the way ;-)
We also noticed those bubbles in the transparent test lines when testing
our fuel system.
This is normal behaviour for fuel when "sucked" by pumps that are
*above* fuel level.
Aviation fuels, and to a greater extent autogas are a mix of many
hydrocarbon substances, several of which have a very low boiling point.
Autogas can even contain some butane and propane solved. So when sucked
out by the pumps, the most volatile hydrocarbons turn to vapour.
We have flown our airplane up to FL 135/145 with no problem, but I must
admit that a fuel system with pumps below fuel level would be far better.
FWIW,
Best regards,
--
Gilles
http://contrails.free.fr
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