Fuel Gauge calibration

[AlanR]

Hi,
Twin 10'' Skyviews.
Tomorrow I am going to do the first time calibration of my fuel gauges so I am just reading the manual to see how to do it. It will probably be obvious once I get into it but just asking the question...
It say I have '10 pours'. Is this 10 pours total ( I have two wing tanks) or '10 pours' per wing tank?
The tanks hold 60litres each ( total 120litres).
Any other useful tips for getting an accurate result from doing this would be greatly appreciated?

Thanks,

Alan

 

[mmarien]

They may have changed that or ten is all that you need to get it accurate. I have a single 130 litre tank and I have 14 calibration points. I believe I did 10 litre adds so empty plus 13 pours. You could probably do 12 five litre pours per side. Each side is a separate calibration so you do them independently.

I was already flying and had my attitude set level at cruise so I leveled the plane to cruise attitude so that the fuel gauge was reading correctly at cruise attitude. The fuel gauge reads slightly different on the ground.

I pulled up to a pump rather than using jerry cans. Not always possible at a busy pump.

I had a fully charged battery. I tried it once with a low battery and ended up losing power half way through.

I have to admit I did mine at least three times. I had a cork float that couldn't measure the bottom forty litres so I changed to a capacitive type sensor. So one battery failure attempt, one cork float sender calibration and finally the capacitive type sender calibration. It gets more efficient each time.

One more thing. My tanks have a number of baffles so I gave it plenty of time to level off before I pushed the button after the add.

 

[Dynon]

So SkyView will take the size of your tank that you provide and then ask for pour quantities by dividing that into a reasonable number of pours, which won't always exactly be 10 pours but it gets in that ballpark. IE, for a 10 gallon tank it may ask for 1 gallon pours, for 20 gallons 2 gallons, etc etc. It does't use that number for any hard quantity measurement, just to set the pour interval.

 

[Carl_Froehlich]

Don't forget to level the plane before starting the calibration.

Carl

 

[AlanR]

Thanks for all the tips...
Thinking about what mmarien says about ensuring battery not low when doing this I assume that I only need one of my two Skyviews fired up when doing this? I have an EarthX lithium battery and now concerned about running it low during the calibration process.

 

[airguy]

Put a battery charger on it if you are concerned about running it down, it could take 30 minutes or better to do this calibration. Make sure the airplane is in level flight attitude when you do it, as Carl mentioned - that should be the main longerons of the fuselage level, and level side-to-side.

 

[mrdaud]

AlanR, per Airguy's suggestion, do not put a standard battery charger on the lithium battery! Only use the special charger provided with the batter (I assume you received one). The battery will accept an alternator charge through a voltage regulator, or you can use a regulated DC supply similar to what you can get at Radio Shack (30 Amp) to run in parallel while you do the calibrations. I also have a lithium battery that weighs 4 lbs and it really cranks my IO-360. Again, I was told by the vendor, Aero Lithium, to never use an automotive charger. Your fears are also well founded regarding running the battery down too far. If you get below 30-40%, it becomes a paper weight and will not recharge. I know from experience!

 

[AlanR]

Well I did it, carefully writing down each 5litre pour and pressing the button. 2x 60 litre tanks on a Bristell NG5. However when I had finished and exited the calibration pages I got a message saying there was a mismatch between the two wing tank readings and did I want to accept this or not. I said 'Yes ' but now I wonder if I did the right thing?
I can see me draining and starting again!

 

[KRviator]

I'm in a similar boat. I flew today to empty the right tank and on finishing the calibration routine (65L tank, 5L pours) I pushed full, it had a think about it, then pressed DONE (think that was what it said), powered off the plane while I reeled in the hose and it looks like SkyView didn't save the calibration table for some reason. The table is blank, and I still have a CAL? over the RHS tank quantity.

Dunno what I did wrong, but it looks like I get to do it again, too...

 

[Dynon]

Alan - The mismatch dialog (assuming we're talking about the same thing) is a feature that allows the fuel computer to compare its state against the totality of your in-tank sensors, and prompt you to match the fuel computer to the in-tank state. It's not comparing your tanks against each other.

 

[Dynon]

KRviator: Did you fully exit setup mode before you shut SkyView down? Calibrations and other changes are sometimes not fully commited to memory until you completely exit setup.

 

[KRviator]

No, I didn't. I was still in the setup screens (Hardware Calibration, IIRC) when I powered down with the master switch. I kind of suspected it'd turn out to be operator error!

 

[jakej]

FWIW, I do a screenshot of the cal or other items just in case

 

[AlanR]

Alan - The mismatch dialog (assuming we're talking about the same thing) is a feature that allows the fuel computer to compare its state against the totality of your in-tank sensors, and prompt you to match the fuel computer to the in-tank state. It's not comparing your tanks against each other.

OK Dynon, Thanks for that I wrongly it turns out assumed it was comparing the two tanks. So maybe I am good to go after all. Time will tell I guess.

Thanks again,

Alan

 

[KRviator]

Okay, so now I have another question (that is also more than likely Operator Error)...One of my Fuel Level senders is not showing full when the tank is. And just to be sure, I repeated the fuel calibration today (and exited setup before I powered down the display this time, too! )

Here, we have Exhibit A, a quick screenshot taken after I've put the plane to bed this afternoon. Note the two fuel quantities, they are both full, both have 67L in the tank, with the RHS gauge correctly showing 60+. But the LHS gauge shows 49+.

Here are the two relevant setup screens, both mirror each other, so I am buggered if I know why one is normal, and the other isn't.

 

[dynonsupport]

This has to do with your calibration, not your "max displayed" in the sensor setup.

We are not getting a high enough voltage to consider that tank to be 60L. Give us a screenshot of the calibration screen for the left tank, with that tank full, and we can show you why.

 

[preid]

I may be thinking something different here, but with my RV the maximum the tank will show with the floats all the way up to the top is 24 gallons. I can carry 30 gallons but the way the wing is there is room for 6 gallons that is a higher level than be displayed. So your 60 may be for a full tank but 49 is all the floats can raise to in your tank and hence that is all that can be calibrated for.
No worries, it will show 49+ until it reaches 48, than it will display correctly.

 

[KRviator]

This has to do with your calibration, not your "max displayed" in the sensor setup.We are not getting a high enough voltage to consider that tank to be 60L. Give us a screenshot of the calibration screen for the left tank, with that tank full, and we can show you why.

Will do. I re-did the calibration yesterday to try to remove this, but given it hasn't changed makes me think the way I've bent the float arm in the left tank must be limiting its' travel compared to the right tank.

I may be thinking something different here, but with my RV the maximum the tank will show with the floats all the way up to the top is 24 gallons. I can carry 30 gallons but the way the wing is there is room for 6 gallons that is a higher level than be displayed. So your 60 may be for a full tank but 49 is all the floats can raise to in your tank and hence that is all that can be calibrated for.

That's what I get with the right tank, and as you've said, it's known and expected as the float reaches its' max upwards travel before the tank is actually full. But what has me puzzled is the difference in the two tanks.

I'll have another look at the calibration tables after the weekend and see what's going on, and if it all checks out, I'll redo the green band to remove the black portion of the gauge.

 

[airguy]

I am using capacitive senders in my inboard mains, and floats on the outboard aux tanks - both have a maximum level they will sense, and they will just display a + above that point. My inboards are 18 gallon capacity and they only show "16+" and my outboards are 16 gallons each, they display "15+" when full.

 

[jakej]

Its the level near the bottom of the tank that concerns me, that's where gauging is more important IMO.