Fuel Gauge / Totalizer Miscompare?

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Jroseund
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Fuel Gauge / Totalizer Miscompare?

Post by Jroseund »

Out of curiosity, I’m seeing what others primarily use for accuracy for fuel remaining; fuel gauges or the totalizer?

My prior gig was a Cirrus so I was used to using the totalizer for fuel burn / remaining as those fuel gauges were very inaccurate.

I have the Legacy G1000 avionics. I have noticed that when my gauges say I have 15 gal left each side, it makes sense that I have burned 20 gals total. However, the totalizer says 24 gal have been used. When I’m at 13 gal per side remaining it should be 24, but reads 26.8 used.

Seeing if others have experienced this and it’s the norm, or possible a recalibration is in order or just a Legacy G1000 vs NXi avionics.

Thanks everyone. Fly safe!
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MarkA
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Re: Fuel Gauge / Totalizer Miscompare?

Post by MarkA »

My experience is the fuel totalizer on my legacy G1000 has always been very accurate. Note, I believe the gallons used is the gallons used since the totalizer was last reset. The gallons remaining is what the sensors in the tanks are reporting.

I normally reset the totalizer and gallons available to 48 when someone else fills the tanks just in case the did not fill them to the top. The gallons used plus gallons available will therefore not always equal 50 in my case w extended range tanks.
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Boatguy
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Re: Fuel Gauge / Totalizer Miscompare?

Post by Boatguy »

After a top up, I inspect my tank levels before the next departure and reset the totalizer. If I think the "top up" was not quite to the top, then like Mark, I'll discount it and use the "DEC" button to reduce it by 2gal.

On my 40NG, I've found the totalizer's "Gallons Used" to be very accurate. However, if I've been overly cautious by adjusting down 2 gal, then the next top up may take less than the reported "Gallons Remaining". If they were in fact topped up (to the bottom of the tabs on my plane), and I reset to the full usable tank capacity, then the next top up quantity is always within .5gal of the "Gallons Used".

The tank gauges are accurate to within a gallon, once the level is below the gauges "blind spots" which are different on each model. It's mandatory to understand the configuration of the tanks and fuel level sensors on your airplane. If the true fuel level is somewhere in the sensor's blind spots, the gauges can only be relied upon to tell you the minimum fuel you have, the totalizer will be a more accurate indication of the actual fuel remaining.
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Rick
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Re: Fuel Gauge / Totalizer Miscompare?

Post by Rick »

Jonathan,

You might want to read this post for additional information. It sounds like you have the 50-gallon 'extended range' tanks, so you actually have 3 interconnected tanks in each wing. The middle tank doesn't have a fuel sensor in it, so the fuel gauge for each side has an area in the middle where it doesn't know the actual level. You can see this on the display as an area from about 15 to about 20 gallons where the green arc stops. If you happen to catch it, you will see the gauge drop slowly through this area in flight when the tank reaches about 20 gallons, then sit at 15 gallons for a long time until the tank gets there, and then read correctly from there on down.

I have found the totalizer to be very accurate in my DA40, always within a gallon, and I use the gauges to cross-check the totalizer.
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Jroseund
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Re: Fuel Gauge / Totalizer Miscompare?

Post by Jroseund »

Thanks everyone for the input about the dead zone in the middle tank. I was aware of that however.

This is a great example. Finished doing a 4.2 flight, 700 nm trip yesterday. Before I left I made sure the line personnel did their best to fill her up as best as they could. I still selected to depart with around 84.5 gallons once I reset the fuel. Once I completed the flight the fuel gauges were reading 14 gal per side, however the fuel remaining said only 22 gallons, a difference of 6.

I have noticed that once the fuel gauges get out of the dead zone and get to about 15 gallons, then the gauges start to drop slightly more quickly. It seems for my aircraft that with 10 gal remaining in each tank, it is pretty darn accurate with the fuel burn on the totalizer.

Guess during the next annual if it still bugs me I can do a recalibration. Just wanted to see if I was the only one with this quirk. Planes are like boats. I swear each one has a different soul and personality.

I will go and read that post you mentioned Rick. Thanks again for everyone's input.
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Rick
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Re: Fuel Gauge / Totalizer Miscompare?

Post by Rick »

Jroseund wrote: Tue Sep 06, 2022 4:01 pmI will go and read that post you mentioned Rick.
I completely missed that you have a DA62, not a DA40, so you may not find it as informative as I originally thought... :oops:
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