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Fuel Level Sensor

RV3Kev

Active Member
Dear Guys

I'm now working on the left fuel tank and it's time to start considering the fuel senders to be used. I'm considering a number of options:

a) Vans Fuel Senders - Cheap but lowest accuracy and reliability ?
b) CIEs digital Senders- Expensive $450 each but best accuracy and reliability. Accuracy would be restricted by wing dihedral and tank shape and will not read accurately until the level had fallen below a critical level (as per (a) above)
c) Two Red cubes - Measure total flow from each tank assuming that a compatible display.

Any other thoughts?
 
I have used the Vans Sensors for almost 6 years and they have been very accurate! Although, being a taildragger, ground readings are high and anything above 16 gallons they say 16+.
 
I use Vans senders, but the read-out goes thru a GRT EFIS. It (and I think most other efis units) can be calibrated to give very good accuracy. On top of that I have a single red cube, downstream of the selector valve. It’s hard to tell which is more accurate.
 
Remember that float or capacitance senders measures what is ACTUALLY in the tank. Fuel Flow transducers (red cube) calculate what is suposed to be in the tank.....very different in real world applications.
Consider a tank leak....yikes
 
Double trouble

I have the Van's senders with a single red cube.

You'll get general information from the Van's senders, but not accuracy that would make me confident to land with 5 gallons of fuel on board. When K factor is properly adjusted you'll get very accurate total consumption from the red cube which I use to refine quantity readings of the less accurate Van's senders.

Although two red cubes is an interesting modification, it would require additional plumbing and double the chance of failure of a failure prone component.
 
On my old RV-3 I made my own capacitive fuel senders. I think 1/4" tube inside a 1/2" tube, with plastic (teflon) spacers (shaped like washers). Holes in the outer tube to allow fuel to easily enter/exit. I drilled holes in the ribs so the outer tube fit diagonally from lowest point to highest point in the tank.

That was before I saw the simple RV-8 capacitive plates.

I regret I didn't install those in my RV-4 tanks (plus a reference plate near inboard bottom).

I got discouraged by hearing about the varying dialectics of MoGas, AvGas and mixtures of the two. In other words, you calibrate your readings using summer MoGas, then readings are off with winter MoGas or when you mix it with AvGas.

Some time after I had closed the tanks, I realized the obvious solution: install a third reference plate that's always covered with fuel. Use its capacitance to adjust the RV-8 plates' capacitance reading using a microprocessor. This however is a true DIY project. I don't think there are any capacitance-to-voltage units on the market that would do that.

So I'm stuck with Van's senders and engine monitor fuel totalizer. You can adjust Van's senders/gauges so they read zero on empty, so you can at least double-check your totalizer readings when getting closer to empty.

Finn
 
The Vans resistive senders are extremely accurate when used with a modern EMS such as the Skyview. The key here is to calibrate the tank with the aircraft in the flying attitude, not as it sits on the ground.

The fuel flow and totaliser functions once the K factor is calibrated, is extremely accurate. You just need to do it right.

I usually see within 1 litre or so. Thats under half a gallon.
 
The Vans resistive senders are extremely accurate when used with a modern EMS such as the Skyview. The key here is to calibrate the tank with the aircraft in the flying attitude, not as it sits on the ground.

The fuel flow and totaliser functions once the K factor is calibrated, is extremely accurate. You just need to do it right.

I usually see within 1 litre or so. Thats under half a gallon.

What David says above...:) Plus if you have an Advanced Flight Systems EFIS you calibrate in both flying attitude and ground attitude and the floats are accurate in both. (Except as others have said the indicated level doesn't start falling for the first 12 gallons or so on my RV7 due to dihedral). Its a non issue if you have the red cube as you know how much you've burned. As far as reliability, 12 yrs and 850 hours and working like the day they were calibrated. I'd do it again. The older I get the simpler I like things.
 
I like physically measuring the fuel before each flight and using clock to keep track of fuel. Has worked for me for the last 40+ years
 
I like physically measuring the fuel before each flight and using clock to keep track of fuel.

Likewise.

The red cube/totalizer doesn't know if a thief has siphoned some from the tanks (it has happened before to a buddy) so physically dipping before starting up gives most confidence.

I'm conservative so I like to have 2x reserve when I land, which is workable for local flying. I switch tanks in flight each 30 mins. If the instruments don't read 100% accurately then it is good to have more than enough reserve.

The tank gauges give me an indication for which is the fullest tank to select for landing, but I don't really rely on the gauges for reading actual quantities.
 
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I like physically measuring the fuel before each flight and using clock to keep track of fuel. Has worked for me for the last 40+ years

Again the argument for also having level sensors:
Fuel leak developing during flight or fuel being siphoned out during flight (missing or bad fuel cap).

Finn
 
Placed an order for Vans fuel level Senders. Cheapest option and some good feedback on reliability.

I always Dip my tanks before flying and don't rely on fuel level gauges.

Kevin
 
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