The Europa fuel measurement options are all problematic.
The original sight gauge was difficult to read and inaccurate. The sight
gauge I installed between the seats still has two very significant problems.
One: the vent for the sight tube of necessity must have some bends in the
tubing, allowing fuel to become trapped and preventing the gauge from
free venting. This occurs when line boys are over exuberant about
filling up the filler neck and flooding the vent line (which I have opening
into the top of the filler neck). Trapped fuel then causes the sight tube to
read inches low.
Two: The curious saddle bag design of the tank allows easy, yet
undetectable shifting of what fuel you may believe to be in the reserve
side into the main, potentially leaving nothing for reserve. This has happened
after some gentleman macro and even after some steep turns in the
presence of bumpy air.
The capacitive measurement systems are all non-starters where we are
fortunate to have choices in fuel (av vs. mo-gas).
The remediation I have been playing with involves two honeywell pressure
transducers at the bottom of each fuel bung feeding an Arduino with a
touch sensitive LCD screen. Not quite finished for publication, but the
thought is that it should provide legible, filtered, reliable fuel weight on
each side, calibrated to the funky shape of the tank.
Two design decisions I made in the prototype may come back to force a
revision: I did not use differential transducers because 1) the limited
altitude range I normally fly at would lead to a trivial error by neglecting
head space pressure (also very difficult to find gasoline-tolerant differential
transducers), and 2) by installing the transducers at a tee in the
bungs, there will be a small artifactual pressure drop which varies with
fuel flow.
When I finish testing, I will let you know.
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=439585#439585
Attachments:
http://forums.matronics.com//files/img_2434_115.jpg
|
