Fuel Calibration question

brinzlee

brinzlee

I love flying!
Joined
Dec 2, 2016
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17
Please could somebody point me in the right direction in order to calibrate the dynon. I have a 59 litre fuel tank which has a saddle in the middle of the tank with a fuel sender that is not quite conventional in so much that it has eight settings, from full to empty. It must have reed switches in it with an appropriate resistor across each switch that has been calibrated for the 59 litre tank. When I calibrate the dynon it is asking for 5 litre increments which comprises 12 x 5 litre increments. But the problem I have is the sender has only 8 possible outputs. How does this correspond with the 12 button increments for calibration. Some will be reading the same as I increment until the next reed switch is triggered.
I am very confused
 
I may be wrong, but I believe that the Dynon will compensate for the lack of changes in the sender. Just do the calibration per the instructions and the Dynon will take care of the rest.
 
more info on the sender would be useful ie what make & type , resistive or capacitive ? Do you have a link to the manufacturer ?
 
I don’t have a brand I think it was custom made for a europa xs. It has, as I have mentioned before 8 calibrated positions with resistors across reed switches. The float has a magnet in it which triggers the appropriate reed switch. So the unit is resistive in nature.
 
Interesting, we've never run into this before. You should be able to set it by fussing with the values. This assumes you are willing to be careful, think through the process, and then verify the final results so that they are accurate. (Side note: SkyView automatical picks the amount and number of levels. You cannot change them manually. It is not always 5 liters and 12 levels. It depends on the tank size. For some tank sizes it will pick 2 liters or gallons per pour.)

Did you discover that you can adjust the values at each level? We think this will work:
1) Calibrate the tank normally. (You could stop there. But some discrete levels will be off by quite a bit.)
2) Go in the setup table for the tank, and look at the fuel levels and values. You should be able to get an idea of what the steps of the voltages vs. fuel levels should look like.
3) Adjust the voltage values and fuel amount for each level.
- Effectively remove four of the levels by setting the values of those four levels to be equal to the one above or below it.
- Adjust the voltage values for all the levels so they match what the values should be.
4) Be careful to verify your calibration in actual use before trusting it.

Note that the best accuracy and resolution you will obtain is 7.3 liters, since the input levels are discrete and not analog.
 
Brinsley, it sounds as though you have the same type of fuel sender as I do, and I am currently in the process of calibrating the fuel on my Skyview, installed in my Europa XS. I have attached a copy of the basic data sheet I have for the sender, in the hope that it is of some help to you.

My Europa has yet to fly, and I am in the final stages of preparation. I followed the wizard in the Skyview, but mistakenly quoted the fuel quantity as 68 Ltrs., As it turned out, I had loaded approx. 52 Ltrs. when the tank overflowed (I am assuming that 10Ltrs. were in the reserve tank). I did notice during the filling process that at a couple of steps, the voltage indicated remains the same between two 5 Ltr fills, and I assume this is the mismatch between the 8 position sender, and the 11, 5 Ltr. steps in the wizard process. If I read the response from Dynon Support correctly, this is in effect doing what they suggest as point 3).
I have decided to start again, to get as accurate a measure as possible. I have fully drained the main tank, and now mean to drain and measure the reserve to check the reserve quantity accurately. I then plan to refill the reserve to this quantity, and start the calibration process for the main tank, probably quoting 52 Ltrs. as the full quantity.
My sender installation is non-standard, in that it is located in a separate cylinder, behind the tank, in the baggage bay, and this has a sight gauge located against the cylinder, so it should be visible by the pilot. I manually calibrated this during my first attempt.

Hope this helps.
 

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Thanks for your input. I have all the voltage settings now for the eight points. So will now amend the 11 fills to suit.
I will let you know Bob how I get on. The sender is identical but located in the main tank. We emptied the tank then filled with approx 11 litres of fuel to fill the reserve only. Then drained the main tank. That way we knew there was exactly 10 in the reserve. Then carried on with the fills for the main tank.
We are using a 912is so the pumps enable a quick drain when it all goes wrong. Lol
 
I tried again to calibrate my system a day or so ago, then put this message on the Matronics Europa forum, but no repsonse as yet.

I am trying to manually calibrate my fuel sight gauge, and also the fuel sender, attached to my Dynon Skyview. The fuel sender is the Lyndhurst LTS3a, which I understand is no longer in production. It was purchased and installed by the original builder, when the project was started back in 1999. The sender is not located in the tank, but is in a separate cylinder behind the passenger headrest, so it is easy to access. I have attached a pdf with instructions on how to calibrate the sender when it is attached to a VDO type fuel gauge, but I have not fitted a VDO gauge, as I want to provide the information via the Skyview.
The instructions for calibrating the sender states that it should be calibrated downwards from a full tank, whereas the Skyview instructions state the calibration is started from an empty tank, upwards, which is the procedure I have followed. At the same time, I manually calibrated the sight gauge, which is next to the fuel sender cylinder. Skyview recommend filling the tank in 5 litre stages, and the Skyview “wizard” records the change in voltage at each stage, to calibrate the gauge to the fuel added. At a couple of stages, there is no change in the voltage, probably because the sender has only 8 switches, and the tank takes 11 x 5 litre fills before becoming full at 56 litres.
All seemed well as I filled the tank, marked off the sight gauge, and followed the wizard. However, as I empty the tank, again in 5 litre drains, both the sight gauge, and Skyview readout exaggerate the amount left in the tank at various stages. I have drained off 40 litres of fuel, yet the sight gauge, and the Skyview gauge read 30 litres when my maths tell me there is only 16 litres left in the main tank (I have separately measured the contents of the reserve tank at 9 litres). This would seem to indicate a faulty fuel sender, maybe the float is sticking in the cylinder ? Before I dismantle the sender from the cylinder, I wondered if anyone else has come across a similar problem, and if so, what sender has been used as a replacement. I read from a search on here that the MOD 60 from Europa for this type of sender now uses one that has 16 switch positions (so should be more accurate) ; has anyone experience of retro fitting this type, or can recommend an alternative sender ?

A question for Dynon Support : Is it possible to retrospectively amend either the voltage or quantity at each of the fill points listed by the wizard once the calibration has been completed ? I didn't discover that it was possible to adjust the values at each level, could you please explain how ? I recall that the window showing each fill would not scroll down following fill no. 7, and the cursor button seemed to do nothing ? This may be my inexperience with the screen operation, I am still getting used to it.

I have a 912ULS, so draining via the electric pump is probably slower than on the 912iS. The other problem I have is that I only have jerry can capacity of 40 Litres, so have to burn off the fuel remainder through my car after each fill & drain. I am really racking up the mileage  :)
 
I believe you can manually adjust the voltage and volume level afterwards. I also have the same problem trying to get to anything after measurement 7. The scroll does not work....I’m glad it’s not just me. Sounds like we have the same sender. We have been calibrating from empty upwards. And also had the same problem as you with two 20 litre jerry cans. Got the third for Christmas with a calibrated 8 litre jug. Life can only get easier.
 
I removed the fuel sender from its cylinder today, and it looks OK, certainly the float moves very freely up and down the tube. I also found on Skyview how to alter both the quantities and voltage level, so I guess I just have to make alterations to more accurately reflect the measured fuel quantities. I did notice that the sight tube display varied by about 5 litres depending on whether the sender was in the cylinder or not, so I think I will manually mark the quantity displayed on the sight gauge from the top downwards, rather than bottom up (as this seeme mor accurate), and also ensure that if anything, I understate the fuel amount showing on the sight gauge.

I read somewhere that the newer fuel sender from Europa has 16 rather than 8 reporting positions, so I will consider changing to  the newer one.

One final thing I did on Skyview was to change the setting suggested on page 7-51 to FUEL LEVEL (RESISTIVE FASTER RESPONSE), as when filling/emptying the tank, this reduces the delay in waiting for the fuel indicator to move.

Brinsley, have you seen the AIL from the LAA about the requirement to check the Rubber Filler Pipe between the cobra, and the tank ? As I emptied the tank (again) today, I took the opportunity to remove and check my Filler Pipe, and it looks OK, but I will be changing to the aluminium one once the MOD is approved by the LAA.
 
Hi Bob
Yes I changed the software to faster response, as you say makes things a bit quicker to calibrate on the ground....
I didn't know about the new Sender though.....If this calibration doesn't work that's the next best option I think.
We haven't checked the rubber filler pipe yet but is on the todo list.....There's always something...
My pet hate is the fuel system on this plane.....Using the Rotax 912iS makes things even stickier with the extra fuel filters and higher pressures involved.....
Where are you based ?
 
I spoke to Karen at Europa today, and she checked and told me the new current Fuel Sender from Europa (FS10) has 18 read points, and is available at £60.80 + VAT. She is going to have someone photograph the top of it, so that I can see if it will fit in my current flange (I hope so, as to change over would then only involve unscrewing the current sender, and screwing in the new sender, rather than replacing the whole unit).

I do get weird readings, not so much from the the filling up action, but the draining down of the tank. I have attached a spreadsheet showing the readings. You need to read the first table from the top down, then the second table from the bottom up. I guess if I am to continue with the present sender, I will just have to amend the Skyview Voltage/Litres table to something that will err on the side of understating the quantity of fuel left, for safety purposes, Someone else has advised me not to stress too much on the Skyview Fuel Quantity readout, as the Fuel Flow calculation is a better indication of fuel available.

My aircraft is currently at my house in Sheffield, but I hope to transfer it ti Gamston/Retford in the next week or so, as I now have my Permit to Test from the LAA.
 

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That's interesting we had similar ambiguities. I'm not sure what is going on with the way Dynon calculates the curve with reference to the volume vs voltage. Because as you know the sensor has already been calibrated to take into account the saddle at the bottom of the tank. I'm not sure how the Dynon can cope with that.
Would be very interested in your findings if the new 18 point sender fits in the original flange. Do you not think we will have another problem though if that was fitted, in so much that we won't be able to use all 18 points as the Dynon wants 12-13 read points, so then we are left with 5-6 that won't be accounted for.
I thought about using a capacitive sender, I see there is a mod for one, but then we have the same problem trying to account for the saddle versus depth throwing out the calculation on the Dynon.
I wonder why you were told not to worry about it too much and concentrate on the fuel flow.....In our build, we have two red cubes to consider as we are pumping fuel back into the tank from the fuel that's not used from the fuel rail. Surely this fuel flow calculation has to deduct from the fuel contents so if its not right the fuel will never display correctly....
We are currently  building in a garage in Southend, Essex....
Good luck with the Permit to Test....we are about to submit to do ours.
 
I have attached the photos Karen sent me for the new fuel sender, and it does look as though it is threaded, so "should" just be a straight replacement. However, as you said, I think we will still have a similar problem because of the 18 points reading versus the 11 from the Skyview, so I have decided not to go with it at present. I am going to see how I get on in the flight testing with the present set-up. Unfortunately, my flight testing has been delayed by approx 4 weeks due to my Inspector being away for a couple of weeks, and then I am away for two weeks.
Very frustrating - another delay - I should be used to them by now !
 

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Thanks very much for the photos....I will take a view on ordering one too....I am going to do another couple of tests on the old one just to confirm my suspicions....
I feel your pain regarding the test flight....It all takes so long doesn't it....Lets hope they are all resolved for a long summer of flying !!
 
Hello brinsley and bob, my name is frank and I am in the test flying phase off my mono wheel build. I am just about to calibrate my fuel senders (I have 2, 1 per side of the tank) and am pretty sure I have the 12 segment resistive type. The instructions in the manual aren’t that great I don’t think. Do you have any words of advice?

Many thanks frank
 
Hi Frank,

If you'd like some personalized advice, give our technical support team a call at 425-402-0433 and they can help go through what the calibration procedures entail.
 
Hello brinsley and bob, my name is frank and I am in the test flying phase off my mono wheel build. I am just about to calibrate my fuel senders (I have 2, 1 per side of the tank) and am pretty sure I have the 12 segment resistive type. The instructions in the manual aren’t that great I don’t think. Do you have any words of advice?

Many thanks frank
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Hi Frank,
The advice from Dynon is good, especially as you have two senders. I'm not sure why you would fit two, or how to connect them to Skyview, are you planning to display as two "Virtual" tanks rather than one ? It will be interesting to see what difference if any you find in the readings.
Be prepared for lots of fills/empties of your tank as you calibrate both the sight guage and Skyview ! I ended up with 20 Ltr, 5Ltr, and 1 Ltr bottles, and much swapping of contents between them in trying to measure accurate quantities. I also became an expert in disconnecting/reconnecting the fuel line in the engine bay to facilitate quick emptying of the tank with the electric fuel pump turned on. I drew up the attached table to show the displayed quantities against actual when filling up/draining down the tank. Both the sight guage and Skyview were fairly accurate in filling up from empty (but that is unlikely to happen in real life, as who waits until the tank is empty before refilling !), but the draining down readings consistently over-read at each 5 Ltr drain. You need to read the Draining Down Columns from the bottom up.
I have now finally got my PTF, so will start monitoring the actual performance of the Skyview, and Visual Guage in real terms. Obviously, I will be keeping a close eye on this. I have drawn up a simple manual table I will fill in after each flight showing the starting quantity, quantity added, and fuel used (based on time & consumption), always veering on the conservative side of things. We used a similar document in the C182 shareoplane, as the Cessna guages were also not know for their accuracy, and the manual system worked well (KISS !).
When W&B allow, I will be filling the tank to the top for each flight, so I can more accurately monitor the usage, and of course, to give me the maximum safety margin.

Good look with you building and testing  :)
 

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Hey Bob. I contacted Karen today and she has said that I do in fact have the 18 segment probe. Any different words of advice?
 
Hey Bob. I contacted Karen today and she has said that I do in fact have the 18 segment probe. Any different words of advice?
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Hi Frank,
I don't have anything else to offer, but it will be interesting to hear you results after calibration using the 18 point probe. I fear you will have the same problem we had, as you can see from my table, the voltage didn't change at various points, even when a further 5 Ltrs were added. I think you may find that the same will happen with the 18 point probe, just at more points.
I hope I am wrong, and you get a more accurate calibration, so do let us know the  results.
 
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