Mike, good question about the calibration
of the probes at ~12v. with no charging going on. My sky sports probes in my
LongEZ were quite a bit off … so much in fact the mfg sent me a chip to
cure the problem without charge. I don’t have my LNC2 operational yet so
can’t do the test. But that’s a good question, the answer to which
should be determined.
Saying that, it might be a “relative”
answer. Like they say, the important time to know your fuel quantity is when
you are close to not having any. That was exactly the problem with the sky
sports units. Idle the quantity was calibrated to zero and in the air it showed
more when in fact it was empty. Not the best. I did not learn the hard way but
probed the tank showing fuel when I arrived at a distant destination and the
physical probe had no fuel on it. Scary.
Jim
From: Lancair Mailing
List [mailto:lml@lancaironline.net] On Behalf
Of mikeeasley
Sent: Wednesday, January 06, 2010
8:51 AM
To: lml@lancaironline.net
Subject: [LML] Re: Fuel Planning -
Capacitance probes
Since the capacitance probes seem to be fairly reliable in
our small sampling, but the potential for inaccuracies is there, I'm
curious about a couple things.
If we calibrate our probes with the engine off, at ~12V in
my airplane, how would the fuel level readings change in flight with ~13.8V in
the electrical system?
How much does temperature effect the fuel level
readings? Say from 30F to 80F.
Also, I did some digging on water being dissolved in
100LL. It appears that they have an additive that causes dissolved water
to separate from the fuel and collect at the bottom of the storage container
(at any step along the way including our wing tanks). I hate to use the
word "practical" when talking to an engineer, but from a practical
sense how much water can we have dissolved in our 100LL? And is this a
bigger problem for the turbine guys?