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Fuel gauges vs. Fuel Totalizer

The only time I look only at the totalizer is when the tanks are near full. Since the tank senders don't reveal level til something less than 13gal, the totalizer tells the story. Once the senders are doing their thing, they become my primary telltale.

Your link is a good reminder, Bill.
 
A fuel totalizer does not account for miscalculations, leakage upstream of the transducer, siphoning due to loose fuel caps, etc.

I primarily use my totalizer, but I cross check with the gauges. If for some reason they disagree, I go the most conservative route.
 
What Mel said. I use both and cross-check to make sure they agree. So far (in my very limited experience) they have stayed very close, but both are electronic devices... and as such are never to be completely trusted.
 
There are probably even more accidents of fuel starvation with aircraft that only have fuel gauges which I would bet is majority of the GA piston engine fleet.

IMO proper flight planning and pre-fighting is the primary defense against these types of scenarios. However, once in the air I'm of the mind that it would be foolish to rely on a single system for fuel management if multiple systems are available. As I have posted before, my totalizer is more accurate then my gauges so it is what I use when I start looking at options when winds aren't as forecast and an unplanned fuel stop is required. But I still look at the gauges most of the time as they are constantly displayed whereas my totalizer is not. In the end, the foundation is my Nav log and doing the math enroute crosschecked against what the instruments are saying. This approach hasn't let down in almost 30 years of flying. YMMV...
 
Most of us have an EFIS or GPS with a flight time reminder. Mine is set for 2.5 hours as an in-my-face reminder to assess fuel state, i.e. cross check levels, totalizer, and range/time to destination.
 
Tripple check

I go along with what Mel said. I fly by what fuel totalizer, fuel gauges, and timer say. If any one of the three does not agree, I stop and get more fuel. The only time you have too much fuel is when you are on fire.

I am sure that everyone flying Amateur Built aircraft understand that 91.205 applies to our aircraft by the operating limitations for Night and or IFR operation. 91.205 states "Fuel gauge indicating the quantity of fuel in each tank." The latests OpLims require that 91.205 be complied with for Night and or IFR operation. Your OpLims most likely say something along the lines of: "After completion of phase I flight testing, unless appropriately equipped for night and/or instrument flight in accordance with 14 CFR ? 91.205, this aircraft is to be operated under VFR, day only."
 
Like Mel said.

For me, three things:

Totalizer,
Tank gauges,
Estimated flow rate and time (you know, dead reckoning).

I accept the most conservative one of these and disregard the other two.

Dave
 
David Paule said:
Like Mel said.

For me, three things:

Totalizer,
Tank gauges,
Estimated flow rate and time (you know, dead reckoning).

I accept the most conservative one of these and disregard the other two.

Dave
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In addition, I also added a sensor that alerts when there is five gallons left in each tank. This will solve the notification issue if the tanks are venting fuel.
 
If you have fuel flow rate in gph, or pounds per hour, and total fuel burned, plus a known quantity at the start, you should be good.
The plane I fly has all the above. Plus I always set a reminder for a remaining fuel level, i.e., when a preplanned quantity is reached, it is time to land, period.

When flying light planes it is standard practice to add one extra fuel stop on a long x-country. There is nothing worse than being in the air, and wishing you were on the ground...
 
Two things about a fuel totalizer...

The obvious one already mentioned... It cannot detect a fuel tank/line leak upstream of the fuel flow measuring device. While rare and unusual, you still need to know and that's one point of continuous measuring other than with dip sticks.

2) If you forget to use the "fuel added" feature, you will be reminded by the low fuel warning setting. Now you have to guess how much you bought/added and add it to the totalizer while doing all the other flying tasks or mental gymnastics. Either way it's a distraction. If you're wrong, you have inaccurate fuel level indication and will be wishing you had the floats which are great for the lower fuel levels.

Bevan
 
TXFlyGuy said:
If you have fuel flow rate in gph, or pounds per hour, and total fuel burned, plus a known quantity at the start, you should be good.
...
Click to expand...

As Gary pointed out earlier, if you fly at night or IFR having just (one) totalizer doesn't meet the letter of the law - unless you have just one fuel tank. Which tank would you select for landing? I agree this question can be answered by careful record keeping, but that's a lot of extra work.
 
If I don't turn off the boost pump on takeoff my fuel totalizer is off. If turned off the totalizer is always within a 1/4 gallon at refuelling.
 
We have 6 tanks, 5 quantity indicators, plus a fuel totalizer (G3X). Are we good to go? The 6th tank is a small header tank that everything feeds into before going to the fuel pumps.
 
newtech said:
If I don't turn off the boost pump on takeoff my fuel totalizer is off. If turned off the totalizer is always within a 1/4 gallon at refuelling.
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I've experienced similar things with my totalizer, but best I can figure, I get an inaccurately high FLOW reading, but the total quantity used figure seems accurate.

I believe the cause of this is fluctuations in fuel pressure caused by the pump making the wheel in the flow sensor rock back and forth across a count.
 
The military jet that I work on has a single totalizer as the only method of indicating fuel level to the pilot. This totalizer is set prior to flight by hand, following direct measurement of fuel level with a dipstick.

Personally, I'd be perfectly comfortable in a homebuilt with totalizer as long as I had a "5 gallons" and "empty" light for each tank.
 
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My EFIS, as Im sure many others do, shows combined fuel gage data as a dot on the fuel totalizer bar. Theoretically it should match the top of the bar at all times. Mine does not because the data from the tank level sensors is not linear (there is a kink in the middle which I suspect is either coverage of the outboard capacative sensor or simply tank volume geometry). I have things set for accuracy at the lower end, towards empty.

This is all moot if one follows the mantra:

Take off after filling the tanks and then drinking 2 cups of coffee. Then the fuel gages don't matter anymore. :)
 
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In 12 Years and ~1,200 hours that little Floscan has been off less than a few tenths of a gallon when I fill up the tanks.

If one of my fuel gauges showed empty when I thought it shouldn't be, I suspect a bad wire to the sensor.

Of course, I always look in the hole before every flight, I always know how many hours it's been since the last time I filled the hole up with gas, and I always abide by the golden hour rule (almost).

Your mileage may vary...:D
 
I’d like to point out that unless you have a means to directly observe the fuel level such as with a sight gauge or transparent tank, any other method will only give you a derived value. Does not matter if it is a FF meter, a capacitance probe, a cork and a wire, or hands on a clock, all derived methods have a failure mode which can lead to fuel mismanagement.

So the real question remains: of the derived methods, which of them have demonstrated an “acceptable” probability of failure, and which are unacceptable? All pilots are taught that the classic variable resistance float senders that are the mainstay of light aviation are NOTORIOUSLY unreliable, so obviously the bar for “probability of failure” is not very high. Does the FF method have a DEMONSTRATED probability of failure higher than the derived fuel level provided by floats, resistors and needles?

Does anyone have any data, or are we just debating what we are personally comfortable with?
 
I have had a resistive sender failure, a fuel flow sensor failure, and even a cork bobber failure. But my guess is most fuel starvation accidents are a result of not knowing how much fuel is on board, not systems issues.
The idea of a leak suddenly appearing short of a cap left off is pretty far out there. However, I have had a pin hole leak on a primary hard line that was discovered in the hangar, but could have happened during flight I guess.

I draw some comfort in having two tanks, two senders, a totalizer, and a clock. As others have mentioned, if they don't add up in the same ballpark....

For those who have a known system issue, like a totalizer that reads differently when the boost pump is left on, fix it. It may not be your airplane forever. I friend of ours bought a used motorhome not knowing the fuel gauge stopped reading at 1/4. Guess what happened? He just had to pull over. Not an option for us.
 
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