Mismatched Fuel Sensor Setup Question

[Dynon101]

Does anyone have a suggestion on how to setup the following mismatched fuel tank sensors so that the total quantity indicated by the EMS will be displayed accurately?

I have an aircraft that has 3 fuel tanks (left main/right main/center collector tank). 

The design is such that the two main tanks installed high up on the wings and they gravity feed down to the collector tank that is installed on the floor of the fuselage. Only when the wing tanks are empty will the collector tank begin to drain.

The main tanks have capacitance probes while the collector tank (5 gallons) has a simple on/off float switch.

I was thinking of setting up the main tanks in the usual capacitance probe manner however the collector tank is a question...

Can I set it up the on/off float switch as a simple resistance float type signal and trick SV where I will run 12 VDC to one lead of the float switch and the other lead to a general purpose pin... then that tank will show as full in the display and also be included in the fuel quantity calculations until the main tanks are both empty and the collector tank drains then the collector tank float drops and then the Qty will instantly drop from 5 gallons to zero.

Any suggestions or prior experience would be greatly appreciated!!

 

[dynonsupport]

The level sensors are never used in fuel quantity calculations in SkyView. Every level sensor is just it's own tank.

All fuel quantity is calculated from the fuel flow sender. You tell it you have X gallons on board before departure and it decreases from that. It's independent of the level sensors.

You can put a switch in the collector. No other fancy stuff needed. Just hook one side to ground and one side to the EMS (not one side to 12V) and the EMS can show full/empty. But again, it won't use that for anything but display.

 

[Dynon101]

Forgive me...I used to chew at the lead based paint on my crib so I am a bit slow on this...it was kinda tasty...still like to snack on a flake or two now and again...Anyhoo...

>The level sensors are never used in fuel quantity calculations in SkyView. Every level sensor is just it's own tank.

So when you set it up you can tell each tank how much fuel is in the tank and the bar graph will display green/yellow/red (depending on the setup) and it will also display a number next to the bar with XX.X LBS (LTRS, GAL. KGS)?

If the above is true then the SV does not add up those numbers to "totalize" the remaining fuel registered in the tanks to show a single number of total fuel remaining...instead...I assume each tank is simply displayed as an independent dial/bar?

>All fuel quantity is calculated from the fuel flow sender. You tell it you have X gallons on board before departure and it decreases from that. It's independent of the level sensors.

So I understand that the "fuel computer" makes its predictions of how much fuel remains at XYZ fix on the flight plan based on the current GPH (LPH, PPH) registered by the fuel flow transducer.

>You can put a switch in the collector. No other fancy stuff needed. Just hook one side to ground and one side to the EMS (not one side to 12V) and the EMS can show full/empty. But again, it won't use that for anything but display.

Can the "picture" of this ON/OFF display be a user selectable image (circle/bar/dial) and a number? In other words I would like to make the presentation of the ON/OFF float switch to be a small bar graph with a "5 GAL" between the larger left fuel tank bar graph and the right fuel tank bar graph and then I can watch the two outboard bars drop slowly and then when they are at zero then the small center tank bar would drop from full (5 gallons) immediately to zero (and maybe turn red) when the fuel drains and the float drops.

Is this possible???

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[Dynon]

Forgive me...I used to chew at the lead based paint on my crib so I am a bit slow on this...it was kinda tasty...still like to snack on a flake or two now and again...Anyhoo...

>The level sensors are never used in fuel quantity calculations in SkyView. Every level sensor is just it's own tank.

So when you set it up you can tell each tank how much fuel is in the tank and the bar graph will display green/yellow/red (depending on the setup) and it will also display a number next to the bar with XX.X LBS (LTRS, GAL. KGS)?

If the above is true then the SV does not add up those numbers to "totalize" the remaining fuel registered in the tanks to show a single number of total fuel remaining...instead...I assume each tank is simply displayed as an independent dial/bar?

OK, so first some nomenclature. The graphics with the bars and numbers on them are your individual fuel tank quantity indicators. They are sourced from individual quantity sensors (resistive float or capacitive), and are not added up. When we say "fuel computer" or "fuel totalizer" and "fuel quantity calculations", we're talking about all of the other numerical widgets that SkyView can display like "fuel used", "fuel remaining", etc. These are completely independent from the quantity readings, and use what you tell SkyView you have (after a fill-up typically), and then from there SkyView subtract the fuel used as determined by the fuel flow sensor. Other widgets like range and mpg further take into account other things SkyView knows like speed, etc. But fundamentally it's using flow information and has no idea about what is in the tank except for what you tell SkyView you have at a known point.

Now all of that said, bars are not added up anywhere. But if you have the fuel flow sensor, you basically get a fuel totalizer from starting state minus continuous flow.

>All fuel quantity is calculated from the fuel flow sender. You tell it you have X gallons on board before departure and it decreases from that. It's independent of the level sensors.

So I understand that the "fuel computer" makes its predictions of how much fuel remains at XYZ fix on the flight plan based on the current GPH (LPH, PPH) registered by the fuel flow transducer.

There isn't exactly that readout, but there's a widget for "fuel at waypoint", which is the fuel at the next waypoint, and another for "range", which is how many miles you can go period. You can also compare the time remaining EMS widget and the Time Remaining on the flight plan.

>You can put a switch in the collector. No other fancy stuff needed. Just hook one side to ground and one side to the EMS (not one side to 12V) and the EMS can show full/empty. But again, it won't use that for anything but display. 

Can the "picture" of this ON/OFF display be a user selectable image (circle/bar/dial) and a number?  In other words I would like to make the presentation of the ON/OFF float switch to be a small bar graph with a "5 GAL" between the larger left fuel tank bar graph and the right fuel tank bar graph and then I can watch the two outboard bars drop slowly and then when they are at zero then the small center tank bar would drop from full (5 gallons) immediately to zero (and maybe turn red) when the fuel drains and the float drops.

Is this possible???

Yep, although since you don't really have any real resolution there, you could consider making that center tank a simple on/off ball style light, to have it better communicate that it's an all or nothing thing. When you're in the page layout editor you can simply whip through all of the styles of gauges.

In summary, you can do whatever you want with the individual tanks. They don't affect the fuel computer calculations, and those calculations - provided you have a well-calibrated fuel flow sensor - will be an effective backup and independent way of understanding your fuel state, especially given the all or nothing nature of the center tank switch.


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[Dynon101]

Thanks for your time...really helpful