Fuel Calibration Advice Requested

[Dynon101]

Can someone please give me some advice on how to calibrate my fuel system?

The airplane has two 40 gallon wing tanks that gravity feed into a 4-ish gallon header tank and from the header tank the engine gets its fuel (no return from engine).

The wing takes will have capacitance probes and the header tank will have a float switch that when the float is up there is no path to ground and then when the float is down the path to ground is made.

So if I pour 2 gallons of fuel into each wing tank then the header tank will fill up and the float switch will raise. I believe I need to make a widget for that is a simple green dot.

So at this point the wing tanks are empty. I assume I then pour 5 gallons into each wing tank and then perform a calibration?

I searched the Installation Manual and Pilot Manual but could not find the procedure. Can you please direct me to the source?

THANKS!!!

 

[jakej]

I'd do as you have suggested - add the 4 ish gal first & then do the individual fuel tank calibration as per SV procedure.
From memory - SETUP MENU > EMS SETUP> HARDWARE CALIBRATION (instructions will be on the screen). Then add the 4 gal to the total fuel in the Fuel Flow computer. SETUP MENU> SYSTEM SETUP> AIRCRAFT INFO.

 

[Dynon101]

THANKS for the advice!!!

 

[Dynon101]

I know this is bit backwards however... Can SV be set up for a fuel tank with a simple on/off float valve switch with the logic being :
- when the float is up the switch is open and no path to ground
- when the float is down the switch is closed a path to ground

If so i can make a fuel tank widget that shows 4 gallons when the header tank is full float up and no path to ground and zero gallons when the float drops and shows ground. Would that work.

Or...if needed I will change the float switch to the opposite so that float up completes the circuit and float down opens the circuit and if I provide a 12 VDC source wire to one side of switch then I can make a widget that is a resistance type fuel gauge with zero resistance when full and maximum resistance value when the fuel tank is empty... in this case the tank will show full but will immediately drop to empty in one step.

Thanks

 

[jakej]

I'd keep it simpler, less chance of 'faults' that way.

There are many ways to achieve a safe outcome, up to you which is suits your situation. If it was me I'd be doing the normal fuel calibration for each tank then set a low level fuel warning (RED colour) which starts at say 2 gals (so when fuel gets DOWN to that level the gauge goes red) for both & maybe a yellow band that starts when down to 6 gallons. Now when you have red just come on (both gauges) after switching tanks you now know there is a total of 8 gallons onboard ie 2 for each tank & 4 in the Header.
You could also use a contact widget controlled by the float switch set at say 3 gallons in the header.
Personally I'd be looking for somewhere to land after one tank goes to red with the other in the yellow.

The above is an example only as I'm not sure of what aircraft or engine you have. PM me if you want.

 

[mmarien]

If so i can make a fuel tank widget that shows 4 gallons when the header tank is full float up and no path to ground  and zero gallons when the float drops and shows ground.

The fuel gauge isn't made to handle just two states but the contact widget will. It can have text that reflects the state in addition to the colored dot on the screen. So make one state 4 with a green dot and the other 0 with a red dot (or black dot to indicate empty).

 

[Dynon101]

Thanks for the advice!!!

The airplane is a Velocity and both wing tanks gravity feed into the header tank with no valves or selector and then the fuel is sucked into the engine from there.

Good idea...

I will design a widget that is called "4 GAL" with a black dot and a red dot for the collector tank and a fuel gauge for each wing tank with a yellow band below 5 gallons and green above.

To test it I will drain all of the usable fuel and then verify that green dot turned red. Then I will pour in 3 gallons then lift that wing to ensure that the fuel gravity drains into the collector, then check the dot, add 0.5 gallons and repeat until the dot turns green (and very the 4 gallons I suspect it is) , then I will repeat the 0.5 gallon pour until I can see the fuel pudding in the bottom of the wing tank. This will be the widget name (say... "5GAL")

Then I will conduct a 5 gallon pour per side capacitance fuel probe calibration until fuel to verify my tank quantity.

Thanks again for the help!!!

 

[Dynon101]

Sorry...more questions

>Generally, you will be prompted to perform up to ten (10) fuel level pours of equal volume; the volume of each pour will be determined by the size of the tank that you input.

I have two 43-ish gallon wing fuel tanks that are interconnected with a pipe.There is no shutoff valve so when one tank is filled the fuel will gravity feed to the other side.

Can I pour in 5 gallons each side,wait a couple of minutes for the fuel to balance and then calibrate the two tanks at one time?

The manual says pours of equal volume and I can do that until the last pour of 3 gallons so the question is will it be OK if the pours are all 5 gallons except the last pour?

Thanks for the help

 

[Raymo]

HomeBuilt,

I think you can but it will require deviating from the standard calibration process.

Rather than doing the pour > tell SV you poured, you will just tell the system that each tank is calibrated then:

Pour 4 gallons (or whatever quantity you want), go to each tank and edit the values to be what is currently registering. Repeat until full.

I have tweaked my settings in a similar way to improve accuracy by noting the tank values prior to fueling. After fueling, I know what WAS in the tank prior to adding fuel. I can then go to that level and confirm or adjust the reading it had.

For example, I note 1.45 prior to fueling, I add 13 gallons (21 gallon tank), I now know that 1.45 is the reading for 8 gallons of fuel. If the value for 8 gallons is not 1.45, I manually set it.

 

[mmarien]

Can I pour in 5 gallons each side,wait a couple of minutes for the fuel to balance and then calibrate the two tanks at one time?

I don't think you can calibrate both tanks at once, but there is nothing saying that you can't pour twice the amount and let it level out in both tanks to calibrate the one tank. Then do the same with the other. On the other hand it may be a lot easier to block the flow between the tanks just for the calibrations.

One thing I did was to put the plane in cruise flight level before I calibrated so that the gauge was accurate in level flight. It sits at a different angle on the gear.

 

[Dynon101]

These are very good ideas...THANKS!!!

I will report back on my progress