actual fuel tank capacity in Tecnam aircraft

[montanapilot]

I've been posting re this topic on the Astore board but it's pertinent to all models and it's a serious safety issue so I'm posting it on this board.

A quick summary - I'm installing a fuel flow system on my Astore. I remembered reading something a year or two ago on the forum that somebody was questioning the stated fuel capacity. So as part of the installation process, I asked my shop to empty both tanks and refill them so that we could confirm, or not, the stated capacity of 14.4 gallons/tank.

My shop did a thorough job of emptying the tanks, and that included disconnecting the line from the tanks to the engine and attaching it to a pump so that any residual fuel would be removed. When they filled it back up, they filled it all the way to the top. The shop also checked the calibration on the gauge on the fuel truck that was used to fuel it. I did not want any excuses so we were aggressive in making sure that the measurements would be accurate.

The fuel capacity in my tanks turns out to be 13.2 gallons, not the 14.4 that's noted in the operators manual. Both tanks took exactly the same amount. That's a total of 2.4 gallons less than what's in the manual and placarded on the fuel tanks. At the rpm settings that many of us use, that's almost 25 minutes of flying. To me, counting on having 25 minutes more fuel than you actually do could create a dangerous situation and it's inexcusable.

What was even more outrageous (and scary) was the answer from the factory, relayed to me by Tecnam US. They said:

1. The fuel capacity is measured "theoretically" using the "effective dimensions" of the fuel tank. They also noted that they didn't deduct space taken up by caulking. It seems like the idea of simply filling up the tanks and seeing how many gallons they took so that it would be actual instead of theoretical did not cross their mind.
Having the capacity of my fuel tanks determined "theoretically" is not acceptable. 
2. They say that there is 1 gallon unusable in each tank.
3. They said that "it would be impossible to have a tank exactly equal to another one".
4. The placard on the fuel tanks on my airplane says that the usable fuel is 14.5 gallons

So, I have ~ 25 minutes less fuel than what's in the manual, the numbers in the manual and on the fuel tanks do not agree, "unusable fuel" is not mentioned anywhere, and somebody else could have a different capacity than I have. I wonder if Cessna and Cirrus measure their fuel capacity "theoretically" and if what their tanks hold, what their manual says, and what the placard on the tank says are 3 different numbers.

Although I don't think that any of us would run our fuel down to only a half hour or so, I'm sure that it happens due to weather or headwinds. If somebody ran out of fuel in flight, I wonder if the ensuing forced landing would be "theoretical". 

[whitey]

That’s a real concern.Normally Tecnam are conservative and my previous and current Tecnams take somewhat more than Tecnam placarded 
I also drained tanks,although not the lines from tank to pumps, and when refilled both sides took 5 litres per side more than the flight manual.Incidentally this is identical to what the local Engineers who assembled it  also reported.
I did this exercise to accurately recalibrate the fuel gauges .Its easy to do and the final result was very impressive as both gauges are now always within a litre or two ,confirmed by dipping and refueling.
cheers

[Ed Midgley]

My P2008 holds a little over 32USG. According to the wing placards it should only hold a little over 26USG.
I assume they did this to make the Light Sport weight.
Some one who didn’t know and filled the tanks would be over thirty lbs heavier than they thought.
Ed

[montanapilot]

Not a surprise. Again, as I was told, "it would be impossible to have a tank exactly equal to another one". Maybe the placards should read "Capacity Somewhere Between 13.2 - 15 US Gal, Take Your Pick".

[buzz]

Montana that was me that was asking questions. You can search back to Jan/11/2018. I basically had the same questions as you because I found inconsistency in the POH and the placards. And I was trying to understand how the unusable was accounted for as well as whether or not the unusable was actually left in the tank or could be drained. Because running out of fuel is one of the common mistakes I think accuracy of fuel information and a clear understanding from the pilots perspective is essential. Bottom line I think most of us 2008 drivers have determined we can cram a little over 16 gals per side. And also I think the general thought is that Tecnam probably uses the same tank construction for US planes as European planes. And since Euro planes can fly heavier Tecnam essentially derated the US tank capacity to meet the US weight limits.

But in the end I agree the manual should give a clear explanation of the fuel situation,

[Flocker]

Mar 6, 2020 0:05:01 GMT Ed Midgley said:

My P2008 holds a little over 32USG. According to the wing placards it should only hold a little over 26USG.
I assume they did this to make the Light Sport weight.
Some one who didn’t know and filled the tanks would be over thirty lbs heavier than they thought.
Ed

+ 1.  My P2008 holds 16 per side, not the 13.7 that's placarded.  For my 912iS, that equates to an extra hour of cruise.

[whitey]

Mine holds 118 litres. That’s almost exactly 31 US gallons if my maths are correct,and I can’t squeeze another drop in.

[TiPi]

I have a P92 Eaglet, bought 2nd hand. One of my first jobs was to drain the fuel tanks through the gascolator drain (down to useable fuel), then refill in 5lt increments and mark my fuel dip stick. The Eaglet holds 90lt by the boook (45 per side), to the factory recommended (invisible) max level, which is about 40mm below the filler neck. I can add nearly 3lt extra per side till the fuel reaches the filler neck but then I have the potential to lose some fuel through the tank vent if the plane is not level.
Bottom line is, you should have a "calibrated" dip stick for YOUR aircraft and use those numbers.

[montanapilot]

Several of us, including yours truly, has a dipstick that came with the airplane. However, I now know that it's inaccurate.

What is your fuel capacity per your manual and the placard on your tanks?

[TiPi]

Manual & placards on the wings list 45lt each as capacity, total useable 87lt. I know I can fit 94-95lt if I need max fuel (6.5h flight time with 30-40lt top up, total usage 110lt, 25-30lt remaining (16.8lt/engine h).

I didn't get a dipstick with my plane so had to make my own. I did both tanks and they were identical.

[bravodriver]

I made my own fuel sticks for my aircraft several years ago.  I created increments in gallon/ inch.   The correlation between actual gallons in the tank and fuel gauge readings are not the same.  I replaced both sending units after one failed and no change.  On top of that, the fuel drop in the tanks is not linear, so a simple fuel sender unit will be in error at various levels.   I  hope there is success with the DER route. Until then I will rely on the fuel sticks for long flights

[montanapilot]

The week before last, I posted my concerns about the fuel capacity in my Astore. As per my post, I had my shop drain all of the fuel out of both tanks and fill them back to the top in order to confirm (or not) that my tanks held 14.4 gallons. My shop found that the tanks only held 13.2 gallons. I grilled the manager of the shop as to how he emptied the tanks to make sure that the numbers were accurate. They did, in fact, do everything that could be done to assure that the tanks were empty.

I now find that the number is in error. Since this is such an important issue, I decided to have them check it once again. I had asked them if they were sure that the meter on the fuel source they used was accurate, and they had assured me that it was.

Nevertheless, I told them to fuel the tanks with another fuel source. The possibility that the calibration on their fuel source was not accurate seemed like a long shot, but it was the only variable for which we only had one metric.

The shop found that my tanks hold 14.5 gallons. They now say that the gauge on the fuel source must have been inaccurate. Quite amazing to me, especially given the grilling that I had done to make sure that they were convinced that the numbers were accurate and the fact that I had told them that I was going to post the results on the forum, which means that others would be relying on these numbers.

I apologize for raising a ruckus about this, but, as I mentioned, I thought I had all of the bases covered and had grilled my shop ten ways from Sunday to make sure that what they told me was accurate. Nevertheless, I just felt like this was important enough to make sure that I wasn’t missing something, and although they felt that draining the tanks again and refilling them was probably a waste of time, I insisted on it.

Whether it’s your airplane mechanic or your doctor, you need to be your own advocate, and this is a great example.

[LSA Flyer]

Thanks for sticking with this! I certainly tip my hat to you for sharing your resolution to get the findings 100% verified. Just yesterday I flew my Astore a few hundred miles back from it's annual at Lockwood and watched as the tanks dropped down to a indicated 8 gallon combined with 45 mins left to destination. The computer said I'd arrive with 5 in reserve but could it be trusted? So, easy call, dropped in at an enroute airport and topped up.... with 20.5 bringing it up to the lower flange lip. Looks like both the gauges and the flow computer are good ( 912is ) and now we know the posted tank capacity is good as well.