What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Thoughts on dual senders in each tank

PilotjohnS

Well Known Member
I am curious what y'all think about using dual senders in each tank? I was thinking of installing another sender in the outer bay. Seems really easy to do before the baffle is installed.
1) can the G3x calibrate with a resistance range from 64 to 480 ohm? If not I guess i could put a resistor in parallel.
2) is it worth the trouble?

Thanks in advance.
 
So the fuel gauge comes off of full sooner. A friend of mine has a Bonanza that has 2 float-type senders in each tank for just that reason. A non-issue for me with the advent of accurate fuel totalizers but it could be done.
 
Just wondering about the value of the added complexity just to know the tank is nearly full......

If the second sender ever needed service the tank would have to be removed.
 
Reason? We dont need no stinking reasons.....

I was thinking of using two senders so that i would start reading the fuel usage and true gallons remaining earlier. This would give me a more accurate range reading as I finish climb out and start cruise. So as soon as i get lean, i could have a accurate range reading.

I guess if I use enough fuel in climb to start dropping the stock fuel senders, it wouldnt matter because until I set the cruise fuel flow, any range calcualted based on fuel flow and galoons remaining wouldnt be accurate anyway.

Maybe i am over thinking this; maybe pre flight planning would tell me when I would start seeing the gauges come off the pegs?
 
I was thinking of using two senders so that i would start reading the fuel usage and true gallons remaining earlier. This would give me a more accurate range reading as I finish climb out and start cruise. So as soon as i get lean, i could have a accurate range reading.

I guess if I use enough fuel in climb to start dropping the stock fuel senders, it wouldnt matter because until I set the cruise fuel flow, any range calcualted based on fuel flow and galoons remaining wouldnt be accurate anyway.

Maybe i am over thinking this; maybe pre flight planning would tell me when I would start seeing the gauges come off the pegs?

Everything you are trying to accomplish is good - full knowledge of your fuel state relative to your trip plan is a huge comfort, and takes a lot of worry of the pilot's shoulders. Which is why fuel flow gauges and totalizers have become pretty much standard in today's digital environment. Even the simplest engine monitoring part of any EFIS (or a standalone EMS) will have a totalizer. And they work great, for not very much money. Rather than reinventing the wheel with a double gauge system that might take a lot of tweaking, you might look at how such a system would serve your purpose.

From your signature, you've got a ways to go - and when people have completed their aircraft, and are looking back at what they thought were significant expenses in the early days, they wonder why they were worried about a couple of hundred bucks. A drop in the bucket when looking at the final big picture.
 
Recommendation?

Paul,
Thanks for the very thoughtful answer. So if you were me, would you put dual senders in, or just rely on fuel totalizer?
 
I am not Paul, and would never pretend to be. BUT, I have inspected many, many fuel system modifications and I would NOT recommend this mod. It adds unnecessary complexity, cost, and weight to a system that has been proven over decades with literally thousands of flying aircraft.
 
Don't get fooled

So at the end of the day the question will always remain: do you trust the fuel gauges? Regardless of how many ways we try to measure the fuel, the best indicator is your watch.

You can fool the indications by parking on a ramp with a slope that is ever so slight that you think both tanks have an equal amount of fuel in them. Even when you check them visually, they can look the same. The reality is that one tank can be much lower than you think.

I just had a friend loose his airplane to this scenario. The tank ran dry much earlier than anticipated due to reliance on an indication.

As Mel said, don't mess with the fuel system. It's proven itself over many flying RV's. The other thing that has been proven is that the resistive floats do fail and need replacing. MUCH easier to just do the one at the wing root.

Vic
 
Last edited:
Thanks all

Ok thanks everyone for the quick and thoughtful repsonses.

So I have decided no mods on the fuel senders, I will stick with what is tried and proven.

You are all right, what was I thinking?
 
Your thinking was fine!

There's absolutely nothing wrong with thinking outside the box. You did the right thing by researching before you jumped in.
 
I installed a fuel flow meter (red cube) in my aircraft, and now that i've used it I regret not installing two of them... One on each tank. I use an MGL gauge to read left and right levels (from the resisitive senders) and the fuel flow (from the red cube). Flow is used to show a total used number (which is combined for both tanks). The total used matches what I put in at the pump to within 1L out of a full tank. I only look at the levels as a rough guide, even after repeated calibrations and tweaking of set points I haven't managed to get them to read accurately (like, 3-4L off at some points).

Two flow meters would be mounted outside the tank, saving more volume inside for fuel. Less things to fail inside the tank, less holes through to the tank that might leak later, etc. etc.
 
I installed a fuel flow meter (red cube) in my aircraft, and now that i've used it I regret not installing two of them... One on each tank. I use an MGL gauge to read left and right levels (from the resisitive senders) and the fuel flow (from the red cube). Flow is used to show a total used number (which is combined for both tanks). The total used matches what I put in at the pump to within 1L out of a full tank. I only look at the levels as a rough guide, even after repeated calibrations and tweaking of set points I haven't managed to get them to read accurately (like, 3-4L off at some points).

Two flow meters would be mounted outside the tank, saving more volume inside for fuel. Less things to fail inside the tank, less holes through to the tank that might leak later, etc. etc.

Works great until it doesn't. i have had a fuel flow sender fail slowly. I discovered it while I was flying a long leg. My fuel level senders are amazingly accurate once they get off the top of the tank. I noticed the issue through my normal scan, checking my level against the totalizer. I have four fuel status relative checks - fuel totalizer - fuel level - clock and brain - and to a much lesser degree, fuel flow.
I wouldn't want to give up any of them.
 
Fuel level senders (one per tank) and a separate fuel totalizer system when used together are unbeatable in my opinion. Granted, the fuel level senders don't sense the top of the tank but that's not all that useful anyway. Sensing the bottom levels and comparing that to what the totalizer is telling you is useful.

Bevan
 
I am extremely pleased with the accuracy of the stock Van's resistive system combined with Skyview's fuel flow totalizer. The red cube has been amazingly accurate and the resistive fuel measurement is a good gross confirmation that I don't have a leak in addition to also being accurate compared to the totalizer and refuel totals after they come off the top. I have more confidence in the fuel measurements in my RV than I did in the military or airlines.
 
I am extremely pleased with the accuracy of the stock Van's resistive system combined with Skyview's fuel flow totalizer. The red cube has been amazingly accurate and the resistive fuel measurement is a good gross confirmation that I don't have a leak in addition to also being accurate compared to the totalizer and refuel totals after they come off the top. I have more confidence in the fuel measurements in my RV than I did in the military or airlines.

Same here. I started with capacitive senders in the tanks and had nothing but trouble with them, ended up going back to the standard resistive floats. My Red Cube totalizer is my primary fuel instrument though, with the resistive floats as a backup to guard against a leak somewhere before the totalizer. The resistive floats won't read the top 4 gallons in each tank and I really don't care anymore. I set the fuel computer to 36 gallons each time I top off, and it matches gallons pumped extremely well.
 
I have duel senders in each tank - I used the senders provided by CIES (think Cirrus/Beechcraft among others). Works great and is incredibly accurate. I get readings all the way to empty. Never have I experienced any deviation in reading versus actual! Highly recommended.
 
Another approach

Although resistive float senders are endorsed above, I read many negative comments in the archives about accuracy and reliability. In fact as installed, either the sender or the gauge didn't work. Yes, that could been resolved . But, I stripped them out and replaced them with simple optical sensors ( referenced here in archives) that trigger flashing lights with " yes/no" simplicity. I never leave the ground without measuring fuel levels and update the totalizer. The Red cube has been very accurate, two might be an enhancement but which one would you believe ? Then you look at your watch and flow rate for truth anyway. Bottom line, the low level sensor lights tell you accurately how much time is left in that tank or " don't land " on that tank if you have set the sensor low. I have set mine at about 2 1/2 gallon.
 
I have duel senders in each tank - I used the senders provided by CIES (think Cirrus/Beechcraft among others). Works great and is incredibly accurate. I get readings all the way to empty. Never have I experienced any deviation in reading versus actual! Highly recommended.

The single sender will provide good readings all the way to empty. It is readings from full down to about 3-4 gallons burned where the single sender is not accurate. I have flown the EI dual digital fuel gauge with the standard senders in the RV-6 since 1999 and they have been very accurate except for the top three gallons.
 
I have the standard Van's single resistive senders providing a signal to a Dynon Skyview. They appear to give a very accurate reading from 14+ gallons down to 0. As the gauge changes from 11 to 10 gallons, you can bet you have burned 10 gallons from the 21 gallon tank. If the senders were hooked to an analog gauge I would not expect that accuracy.
I had a Bonanza for years with two senders per tank. Left side was pretty good the whole scale. Right side would rapidly move from full to 1/2 tank as the first 5 of 40 gallons were used. Fairly accurate for the remainder of the scale. Could have made it better for a couple AMUs.
I am convinced accuracy has to do more with what is getting the signal rather than the sender. Thank goodness for the red cube.
 
Back
Top