I think the reserve warning is a good idea, not that I have fitted one. In
addition to my magnetic float fuel level indicator I also use my EIS with an
elba sender to monitor fuel flow and fuel remaining etc.. The fuel gauge
together with the fuel computer work very well. However a fuel computer on
its own reporting fuel remaining based on a calculated estimate in turn
based on a human tank contents entry at start would not fill me with
confidence.
In a last minute rush to depart an airfield it would be all to easy for me
to make an error in setting the tank level.
As a third check I also dip my tank before departure so I know fairly
precisely how much fuel is in the tank.
I've flown a little over 200 hours with my system and I wouldn't change it.
In fact I am doing the same thing on my current build project.
For those concerned about a blockage in a fuel flow sender and you should be
concerned. I am trying to source some solenoid type fuel cut off valves that
would facilitate an easy fuel by-pass system past a fuel flow sender.
Jerry
LTS@avnet.co.uk
www.avnet.co.uk/touchdown
----- Original Message -----
From: "John Eckel" <eckel@iname.com>
Subject: Fw: Europa-Fuel contents
> http://www.eaa.org/education/fuel/cessna_study.html
>
> The above site may be of interest
>
> John, A230
> ----- Original Message -----
> From: Nigel Charles <72016.3721@compuserve.com>
> Subject: Re: Europa-Fuel contents
>
>
> > Message text written by "LTS"
> > >Advantages:
> > Inexpensive
> > Very low current draw
> > Not susceptible to fuel density changes (like a capacitance device)
> > Does not break if in contact with water
> > Very well damped
> > Readings are very consistent
> > Very reliable
> > Currently used by four of Europe's leading A/C manufacturers (soon to be
> 4)
> >
> > Capacitance gauges may appear more accurate because they have better
than
> > 1/8th resolution but because of the variations in fuel make up they are
> > often less accurate. The difference being with our gauge if it indicates
> 20
> > litres you have at least 20 litres. Whereas with a capacitance gauge if
it
> > says you have 22.5 litres may have 22.5 litres then again you may not.
> > <
> >
> > I would say that the reliability is the main advantage. I have a double
> > probe capacitance system and will report back if I lose accuracy. The
very
> > low current draw is not an issue as no gauging systems use significant
> > amounts of current anyway. I would suggest that, looking at the
percentage
> > accuracy we are talking about, fuel density is not a significant issue
> > either. Even if there is a difference in fuel density between Avgas and
> > unleaded it is unlikely to amount to much (does anyone have any figures
on
> > this?). In fact one of the reasons for large aircraft using capacitance
> > systems is that fuel weight is more important than fuel volume as energy
> is
> > proportional to weight not volume. Water is without doubt the main
enemy
> > to the capacitance system. Keeping moist air out of the tank and
filtering
> > the water out of the fuel in the first place is important. Damping can
be
> > achieved in any electrical gauging system by using the appropriate level
> of
> > capacitance. Without doubt the magnetic system will be consistent
> > particularly if the fuel quantity is measured at each switch changeover
> > point.
> >
> > I still feel an accurately set up integrator system using a fuel flow
> > sender is likely to give the best results. It still needs a tank gauging
> > system to act as a cross check to guard against misinformation due to
> leaks
> > and must be updated during refuelling. It doesn't need to make
allowances
> > for tank shape and senders are typically calibrated to 2 - 3% which is
> > likely to be much better than any existing gauging system. With large
> > aircraft, where large amounts of fuel in several different tanks over
> large
> > periods of time have to be measured, we find that the guages are often
> only
> > more accurate at full and empty. In between the linear accuracy of the
> > integrator system proves to be more consistent.
> >
> > However we measure the fuel quantity, having a final warning in the
form
> > of a reserve is a useful measure to ensure a landing is achieved before
> > fuel exhaustion.
> >
> > Nigel Charles
>
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