Adding a backup fuel quantity indicator?

Discussion in 'Maintenance Bay' started by farmrjohn, Nov 7, 2019.

  1. farmrjohn

    farmrjohn Pre-Flight

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    I have an Alon A2 with two wing tanks joined with a tee that feed via a fuel pump into a header tank that then gravity feeds the carburetor. The header tank has a float gauge and the two wing tanks have a single float gauge in the left tank. The tank gauge is very difficult to see/read in flight, requiring extensive gymnastic or yoga moves in order to see it. It does read fairly accurately in its defense (when you can see it). Would it be possible to add in a pressure sensing sensor like the Belite Radient sensor http://tinyurl.com/y4ldlb96 to an added tee just down stream of the tank line junction such as http://tinyurl.com/y6mr8kke to feed an auxiliary fuel gauge such as http://tinyurl.com/y2ahxwh7 ? This would keep the certificated indicator but provide an easier to read indicator on the panel. Would the fact that the fuel pump would be drawing fuel from the joined fuel line impact the head pressure the Belite sensor would detect, and hence the quantity reading?
     

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  2. Bell206

    Bell206 Pattern Altitude

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    Anythings possible, but regardless which direction you wish to pursue it will be at least a major alteration so perhaps talk it over with your AP/IA for more specific info.
     
  3. Ryanb

    Ryanb Touchdown! Greaser! PoA Supporter

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    Truthfully, I wouldn’t see the need for as much headache as it’s likely to create.
     
  4. Arnold

    Arnold Pre-takeoff checklist

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    My back up fuel gauge is a wristwatch.
     
  5. asicer

    asicer En-Route

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    Fuel totalizer?
     
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  6. sarangan

    sarangan Line Up and Wait

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    The most effective fuel indicator is a clock. Even though it is required under IFR, most airplanes have them hidden away in some corner of the panel. Given the number of fuel exhaustion accidents that happen, I am surprised that we don't have a large visible clock that ticks down, and then starts screaming at you when you dip into your reserves. Even my $500 drone has that, and will refuse to fly if the battery is too low.
     
  7. Silvaire

    Silvaire En-Route

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    While the clock is important it is not an "indicator" It's perfectly accurate so long as everything is as it's supposed to be but the value of the clock and indicator combination is that when something is wrong it will cause you to ask yourself "why is it doing that?" The indicator doesn't even have to be that accurate but will have a known and expected behavior.
     
  8. James331

    James331 Touchdown! Greaser!

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    Ive always flown with a backup, a good chrono watch, heck even a cheap watch or egg timer would work
     
  9. Shuswap BC

    Shuswap BC Pre-takeoff checklist

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    Why not just guess slightly high on fuel burn, and as others said, time it. If for example you have 50 gallons useable, and typically burn 9.7 gph, round it up to 10 gph, so you have 5 hours until empty, or 4.25 hours with 0.75 reserve.
     
  10. farmrjohn

    farmrjohn Pre-Flight

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    Actually I do use a clock (time) as a back up, but timing won't detect a leak or poor engine leaning, and a fuel flow totalizer won't detect a leak prior to the totalizer. Back to my second question, would the fact that the fuel pump would be drawing fuel from the joined fuel line impact the head pressure the Belite sensor would detect, and hence the quantity reading?
     
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  11. JAWS

    JAWS Line Up and Wait

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    This is an Ercoupe, correct? Pretty basic airplane. Run the wings to the fuselage tank. Once the fuselage indicator starts to drop, you know you have xx amount of fuel left.
     
  12. bobmrg

    bobmrg En-Route

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    Right. It is "time in the tank," not "fuel in the tank."
     
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  13. Plano Pilot

    Plano Pilot Pre-takeoff checklist

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    I had a student that bought a Alon A2 years ago. We were on a dual x-country and I noticed the fuselage tank level was going down. We should have had plenty of fuel in the tanks. We lost the fuel pump, had to stop for fuel a couple of times on the way home to fill the fuselage tank. The fuel pump moves fuel from the wing tanks to the fuselage tank.
     
  14. SoCal 182 Driver

    SoCal 182 Driver Pre-Flight

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    ^^THIS^^
     
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  15. Plano Pilot

    Plano Pilot Pre-takeoff checklist

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    Does not work when the fuel pump to move the fuel from the wings to the header tank dies. Generally I agree with you.
     
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  16. Greg Bockelman

    Greg Bockelman Administrator Management Council Member

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    Yeah, that. Or a leak in the tank.
     
  17. Greg Bockelman

    Greg Bockelman Administrator Management Council Member

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    Yabut...

    what if the “clock” that keeps the time in the tank decides to run fast? LOL
     
  18. James331

    James331 Touchdown! Greaser!

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    Farmer John, you’re a wee bit overthinking this.

    Rule of thumb on the conservative side and a watch.
     
  19. Tarheelpilot

    Tarheelpilot En-Route

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    This works great as long as there isn’t a leak.
     
  20. Clip4

    Clip4 En-Route

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    Might be simpler to buy a different airplane.
     
  21. farmrjohn

    farmrjohn Pre-Flight

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    Time = Quantity/rate If you don't have a means of measuring rate, you can't solve time to see what time is in the tank. The plane is not equipped with a flow meter/totalizer, and that still would not account for possible leaks prior to a flow meter, ie. leaking tank, line, or venting cap. Using an assumed flow rate doesn't account for incorrect leaning in cruise or change in engine performance.

    Simpler? Selling the current airplane and finding another? I don't think so considering the hassle of selling the current plane and finding another. I don't see the difficulty in adding a tee to the existing plumbing, connecting the sensor, and running the wires to a gauge.

    That said, I suspect the fact the electric pump will be drawing fuel from the line will reduce the head pressure the Belite sensor registers, making the auxiliary gauge reading inaccurate while the electric pump is running. I don't want to cycle the pump to get a fuel reading so will leave well enough alone. Timing and the header tank float gauge will be good enough.
     
  22. James331

    James331 Touchdown! Greaser!

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    Dude, you are overthinking yourself into a bad spot IMHO

    I’m all for getting fancy, but this is kinda silly
     
  23. wilkersk

    wilkersk Cleared for Takeoff

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    I have yet to fly an airplane that has fuel gauges that I'd trust enough "in-flight" to make that even a thing. A dip stick and a watch are my fuel qty gauge.
     
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  24. wilkersk

    wilkersk Cleared for Takeoff

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    Ahhh..... Now, you've brought up the REAL reason for having fuel qty gauges in an airplane. Its not quantity, its rate of change. Or, more precisely, a change in the rate of change.
     
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  25. Shuswap BC

    Shuswap BC Pre-takeoff checklist

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    That is so extremely true, they are at best, a bad guess.