Kris_Adams

Bladders, CiES, and calibration

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Hi Everyone,

I had CiES senders and EI CG-30P/C installed in my J.  The fuel flow measures perfectly but the tank readout very quickly show 5-8 gallons lower than actual.  I've read many threads and it sounds like it could be a calibration issue.  I'm traveling and don't have my manuals with me, but as I recall, I have 1.2 gallons unusable per side.  I had 64 gallon bladders installed in Oct 2016.

Here's the question:  when calibrating the CG-30P, should we:

  • Show the unusable fuel as 0 and then start adding fuel to each tank until 32 gallons are added

                                                OR

  • Show the unusable fuel as 1.2 gallons per side and then start adding fuel to each tank are added

Any suggestions or ideas would be greatly appreciated.  Right now I've spent a good bit of $$$ on the setup and my gauges are worse than before!

Thanks

Kris

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2 minutes ago, Kris_Adams said:

Hi Everyone,

I had CiES senders and EI CG-30P/C installed in my J.  The fuel flow measures perfectly but the tank readout very quickly show 5-8 gallons lower than actual.  I've read many threads and it sounds like it could be a calibration issue.  I'm traveling and don't have my manuals with me, but as I recall, I have 1.2 gallons unusable per side.  I had 64 gallon bladders installed in Oct 2016.

Here's the question:  when calibrating the CG-30P, should we:

  • Show the unusable fuel as 0 and then start adding fuel to each tank until 32 gallons are added

                                                OR

  • Show the unusable fuel as 1.2 gallons per side and then start adding fuel to each tank are added

Any suggestions or ideas would be greatly appreciated.  Right now I've spent a good bit of $$$ on the setup and my gauges are worse than before!

Thanks

Kris

@Marauder and I just went through the same issue.

You want to drain your tanks completely, then add unusable fuel to each side. After this you cant start the calibration. Take your 0 reading with the unusable fuel in the tanks. I think its 1.25 gallons per side unusable for the bladders. The CiES senders are a huge pain to get in and get wired correctly, but they seem to be pretty easy to calibrate once everything is wired correctly. They are definitely very smooth. 

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Kris -- check to make sure the 64 gallon system has 1.25 gallons unusable. It may be more.

Also make sure the plane is level. My mechanic was only able to get 50 gallons in during the initial installation of my JPI. By leveling the plane, Terry and I were able to get 52 gallons in with it level.

The next morning I was able to get another 1/2 gallon per side in. Still less than the STC's 54.8.


Sent from my iPad using Tapatalk Pro

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57 minutes ago, Marauder said:

Kris -- check to make sure the 64 gallon system has 1.25 gallons unusable. It may be more.

Also make sure the plane is level. My mechanic was only able to get 50 gallons in during the initial installation of my JPI. By leveling the plane, Terry and I were able to get 52 gallons in with it level.

The next morning I was able to get another 1/2 gallon per side in. Still less than the STC's 54.8.


Sent from my iPad using Tapatalk Pro

52 gal + (2 × 1/2)  + (2 × 1.25) = 52 + 1 + 2.5 = 55.5 > 54.8, so you aren't "short" at all. Unless your bladders list usable capacity and not total capacity, in which case you are short by 19 ounces per side. How accurate was your 1.25 gal addition for unusable fuel, and how complete was the pre-fill draining of the tanks?

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52 gal + (2 × 1/2)  + (2 × 1.25) = 52 + 1 + 2.5 = 55.5 > 54.8, so you aren't "short" at all. Unless your bladders list usable capacity and not total capacity, in which case you are short by 19 ounces per side. How accurate was your 1.25 gal addition for unusable fuel, and how complete was the pre-fill draining of the tanks?


The STC shows total fuel in the bladders to be 57 gallons (might be a little more) with useable being 54.8 and the rest unusable. That should leave around 1.1 unusable (Terry - I don't have the STC on my iPad, can provide those numbers?).

Even with leveling (something you most likely wont be able to do at a pump), the total should be 54.8 useable. The best I could do is ~53. This includes letting it sit over night to squeeze in another gallon total.


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Ok, they drained my tanks and re-calibrated and it seems like I'm in the same situation.  On my right tank according to fuel flow (which is normally very accurate) I burned 20 gallons...according to my EI/Cies, I burned 26 gallons.  I'm going to fill up tonight but I'm sure the tank will take ~20 gallons matching the fuel flow usage. 

As I understand they drained the tanks empty and then started adding and calibrating.  I think I understand that they should have added 1.25 gallons per side then started calibrating, but this difference still doesn't appear to explain why I'm off by 6 gallons.

This is super frustrating.

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My EI starts flashing a warning when either tank is below 8 gallons...since the EI/Cies is off by 6 gallons at that point, I'm getting a yellow warning light when the tank really has 14 gallons left. I can acknowledge the caution light but it tends to come back on as the fuel sloshes around and goes above 8 gallons again.

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1 hour ago, Kris_Adams said:

As I understand they drained the tanks empty and then started adding and calibrating.  I think I understand that they should have added 1.25 gallons per side then started calibrating, but this difference still doesn't appear to explain why I'm off by 6 gallons.

This is super frustrating.

Not necessarily. The Zero fuel calibration point is most important. By not adding unusable fuel before they started the calibration, they screwed up not just the first, but all of the readings. That could easily account for the 6 gallons. Check for good grounds, and then start over by draining all fuel, adding unuseable, then start your calibration. Seeing how rock solid and smooth the CiES senders are once installed, I'm thinking it is more than likely the methods that your mechanics used, not the equipment. 

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3 hours ago, Kris_Adams said:

Ok, they drained my tanks and re-calibrated and it seems like I'm in the same situation.  On my right tank according to fuel flow (which is normally very accurate) I burned 20 gallons...according to my EI/Cies, I burned 26 gallons.  I'm going to fill up tonight but I'm sure the tank will take ~20 gallons matching the fuel flow usage. 

As I understand they drained the tanks empty and then started adding and calibrating.  I think I understand that they should have added 1.25 gallons per side then started calibrating, but this difference still doesn't appear to explain why I'm off by 6 gallons.

This is super frustrating.

You have wet wings or bladders? On the bladder system there is at least 2.5 gallons of unusable (probably more like 3 to 3.5). And I think you would be hard pressed to get 27.4 gallons of useable in each side.

I’m resolved to the fact my 54.8 gallon useable airplane is really a 50 gallon useable airplane.

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1 minute ago, Marauder said:

You have wet wings or bladders? On the bladder system there is at least 2.5 gallons of unusable (probably more like 3 to 3.5). And I think you would be hard pressed to get 27.4 gallons of useable in each side.

I’m resolved to the fact my 54.8 gallon useable airplane is really a 50 gallon useable airplane.

I think he has the 64 gallon bladder system Chris. 

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Just now, N6758N said:

I think he has the 64 gallon bladder system Chris. 

I wonder if the “rules of fuel” apply to the wet wings as well. It’s clear that there is no way you can get full fuel quantity into a bladder equipped plane unless it is leveled. Something that just isn’t going to happen unless you filled up with the nose pointed slightly downhill. 

I wonder if the wet wings are subject to this phenomenon as well. Can’t se why they wouldn’t be.

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The interesting thing about both the wet wing and the bladders is the vent is in the forward, outboard portion of the tank. So you would think at some point it would start to drain fuel from there if you tried filling it in a nose low attitude. 

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Just now, N6758N said:

The interesting thing about both the wet wing and the bladders is the vent is in the forward, outboard portion of the tank. So you would think at some point it would start to drain fuel from there if you tried filling it in a nose low attitude. 

I do know that if big Bertha steps on my wing on a hot summer day with a full fuel tank, it does comes out the vent.

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5 hours ago, Kris_Adams said:

Ok, they drained my tanks and re-calibrated and it seems like I'm in the same situation.  On my right tank according to fuel flow (which is normally very accurate) I burned 20 gallons...according to my EI/Cies, I burned 26 gallons.  I'm going to fill up tonight but I'm sure the tank will take ~20 gallons matching the fuel flow usage. 

As I understand they drained the tanks empty and then started adding and calibrating.  I think I understand that they should have added 1.25 gallons per side then started calibrating, but this difference still doesn't appear to explain why I'm off by 6 gallons.

This is super frustrating.

Although you need to find out if they started with 0 fuel after adding back in the unusable, (i.e. 0 fuel level includes unusable added), but I doubt a licensed mechanic would make such a mistake.

But make sure the plane was leveled for calibration - both longitudinally and laterally. Keep in mind if fuel is added to only one side at a time, it will be no longer be level laterally. Thus during fuel calibration, fuel should be added in the same amounts to both sides to keep the wings level. That could introduce a huge error at around 1/2 full while little to no error near empty and full.

Also, your fuel gauges, calibrated for level flight, will be a bit off on the ground since no longer level. 6 gallons difference doesn't seem likely though. 

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3 hours ago, kortopates said:

Although you need to find out if they started with 0 fuel after adding back in the unusable, (i.e. 0 fuel level includes unusable added), but I doubt a licensed mechanic would make such a mistake.

But make sure the plane was leveled for calibration - both longitudinally and laterally. Keep in mind if fuel is added to only one side at a time, it will be no longer be level laterally. Thus during fuel calibration, fuel should be added in the same amounts to both sides to keep the wings level. That could introduce a huge error at around 1/2 full while little to no error near empty and full.

Also, your fuel gauges, calibrated for level flight, will be a bit off on the ground since no longer level. 6 gallons difference doesn't seem likely though. 

I suppose it would be easy enough to snug wing jacks to keep the wings level while calibrating.  

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Tank volume seems to be affected by the location of the fill hole...

If I fill up in the level hangar,  fuel level with the top of the wing skin...

does the fuel level rise and touch all points of the fuel neck ring at the same time?

Or, does it touch the front of the hole or back of the hole first?

These are subtle hints that there is a gallon or more available space that is not getting filled because the cap hole isn't located very well compared to where the ground is.

putting the cap further uphill near the tank vent would have given a few more gallons of volume more as well.

Our dihedral makes a nice air buffer for temperature related fuel volume changes. 

Thinking out loud,

-a-

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21 hours ago, Marauder said:

You have wet wings or bladders? On the bladder system there is at least 2.5 gallons of unusable (probably more like 3 to 3.5). And I think you would be hard pressed to get 27.4 gallons of useable in each side.

I’m resolved to the fact my 54.8 gallon useable airplane is really a 50 gallon useable airplane.

64 gallon bladders

 

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18 hours ago, kortopates said:

Although you need to find out if they started with 0 fuel after adding back in the unusable, (i.e. 0 fuel level includes unusable added), but I doubt a licensed mechanic would make such a mistake.

But make sure the plane was leveled for calibration - both longitudinally and laterally. Keep in mind if fuel is added to only one side at a time, it will be no longer be level laterally. Thus during fuel calibration, fuel should be added in the same amounts to both sides to keep the wings level. That could introduce a huge error at around 1/2 full while little to no error near empty and full.

Also, your fuel gauges, calibrated for level flight, will be a bit off on the ground since no longer level. 6 gallons difference doesn't seem likely though. 

I'm going to verify the unusable fuel situation.  I suspect it was not on jacks (level) for calibrating.  I'll double check that too.  Thanks for the ideas!

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I've mentioned several times my data point, Twin Lakes Avionics installed my JPI EDM 930 at which time the fuel level senders were sent to Lock Haven for o'haul. They carefully filled the tanks and assured me that they could only get 26 gallons in each side. They nevertheless calibrated to the O&N STC value of 27.4 per side. When I think about it I override the full tank value to 52 on board. 

I'll be interested in what the new STC holders determine the real capacity to be.

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On 9/27/2017 at 12:58 PM, Kris_Adams said:

I'm going to verify the unusable fuel situation.  I suspect it was not on jacks (level) for calibrating.  I'll double check that too.  Thanks for the ideas!

Sorry I've been away for a bit and then we've been trying some other things with 79H

...so the plane was on jacks and level when they calibrated the gauges.  They've callibrated 4 times now so I'm pretty sure it's not the shop, plus they've installed a ton of JPI's and EI's.  The last time they calibrated a gallon at a time and the tank was completely full...still getting the same thing:  the right tank after burning 10 gallons actual (confirmed by fuel flow and a re-fill) shows -16.  The left tank gauge shows 5 less than actual after 10 gallons burned.

I did run the right tank low (according to the gauge).  The discrepancy closed from -6 to -4 when I had burned 25 gallons out of the right tank.

Still hoping to hear from @fuellevel.  I'll call him later this week hopefully.

I think our next step is to drain the tanks all the way and verify 32 gallons are going into each side.  Needless to say I'm still pretty disappointed but keeping my hopes up!

-Kris

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Sorry  this thread went completely around me.   We are dealing with a few issues internally with a major health issue with my production manager that has been a large distraction 

The calibration does sound wonky   - do you have the information they put into the EI for calibration values.  and was clearance checked on the outbd sender as it has hit things  - should be less in the bladder install. 

I am around, but in Vegas for NBAA - but I am available  

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On 10/9/2017 at 11:23 AM, fuellevel said:

Sorry  this thread went completely around me.   We are dealing with a few issues internally with a major health issue with my production manager that has been a large distraction 

The calibration does sound wonky   - do you have the information they put into the EI for calibration values.  and was clearance checked on the outbd sender as it has hit things  - should be less in the bladder install. 

I am around, but in Vegas for NBAA - but I am available  

Scott the outboard senders are definitely unobstructed.  We were able to verify full movement and no obstacles. 

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Does this process sound correct?:

1) drain fuel at the fuel drains

2) level the plane

2) add the 1.25 gallons unusable fuel per tank--this is the amount listed in the O&N STC doc's

3) calibrate this as the zero fuel level

4) begin adding fuel and calibrating the EI?  I should be able to get an additional 32 gallons per side on this step?

Thanks again for hanging in on this thread!

-Kris

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