M20E with aux tanks - how do you fuel your plane

[pagirard]

Hi everyone,

I'm a long time reader and first time poster. I've read and learned a lot on this forum and I'm now the proud co-owner of a '74 M20E.

The previous owner was very meticulous and the plane is in great shape besides the usual Mooney squawks like a small fuel tank leak.

Along side other modifications, this plane has the supplemental aux tanks on the wings (+34g of 100LL) and these tanks are connected to the main tanks so when fueling the main after a bit the level goes down. The previous owner developed a method using a universal fuel gauge (graduated acrylic tube) but has only few points in his calibration for each tank.

I was thinking rather to make a removable tab system allowing for a visual guide for refueling. Does anyone has experience with that - or a better method ?

 

thanks in advance for your help

 

Pierre

 

[carusoam]

Welcome aboard Pierre!

1) You have fuel bladders

2) The cells are connected by small tubes… ?

3) You have two fuel caps on each wing… ?

 

4) It is challenging to know the fuel level while fueling… because fuel is trying to flow through the tubes…. Air will be moving in opposite direction…

5) Fill the lower tank first…. While doing this… fuel is flowing to the uphill tank…

6) Fill the uphill tank next… some fuel has already appeared in the bottom…

7) The procedure probably mentions how to top off the tanks…

 

8) I have a Long body… 50gal each side…. The fuel cap is a little further up hill….  No bladders, with air holes in the ribs to allow drops of fuel and air to pass through….

9) When partially filling the tanks… there is some wait time expected for fuel level equilibration…

10) as far as fuel level sticks go… the procedure for marking them is the simple fill the tanks… 2 gal at a time, draw a line…

add two more, allow for equilibration, draw the next line… repeat….  

Every body gets to do this at least once… while proving out their useable fuel numbers…

11) Most Mooney fuel tanks are near rectangular in shape, with few missing volumes… this makes fuel volume calculations a bit easier than shaped tanks… check to see how rectangular (overall) your bladders are from one end to the other…

 

Now look up Ceis fuel level gauges… fancy, modern, 

 
Stand by to hear from people with bladders…. Let me invite @Marauder to the bladder conversation…

 

PP thoughts only, not a mechanic…

Best regards ,

-a-

[mike_elliott]

Was this Jonathan Paul's record setting E by chance?

[kortopates]

CIES fuel senders via an EDM-900 mostly solves the fuel level/remaining question for my mooney with Monroy tanks. it would need another sender or moving the outboard sender to the outboard monroy tank extension to get a better solution.

Before the CIES i relied on the fuel hawk dip stick as well. It works fine as long as wings are laterally level.


Sent from my iPhone using Tapatalk

[carusoam]

@Oscar Avalle… other current discussion of JPI 900 amd Ceis gauges…

Similar, but not exactly the same as your discussion…

Hardware based…

Best regards,

-a-

[Niko182]

On 3/1/2022 at 6:01 AM, mike_elliott said:

Was this Jonathan Paul's record setting E by chance?

His was a 66 i believe. Not a 74.

[Urs_Wildermuth]

On 3/1/2022 at 6:12 AM, carusoam said:

1) You have fuel bladders

2) The cells are connected by small tubes… ?

3) You have two fuel caps on each wing… ?

What he describes looks more like the Monroy tanks. So no bladders, but 2 additional compartments.

[pagirard]

On 3/9/2022 at 3:36 AM, Urs_Wildermuth said:

What he describes looks more like the Monroy tanks. So no bladders, but 2 additional compartments.

That is correct, each wings have 2 tanks and they are connected permanently, when you fuel the main tank, some fuel goes into the aux tank after a while and vise versa. This makes fueling and knowing how much fuel we have on board a bit complicated. The previous owner gave us a nice chart to use on each tank with the universal fuel gauge.

I spent some time and extrapolated (2nd order polynomial worked best with the data available) and got this table:

blue cells are the actual measurement points

 

And this is an example of the interpolation:

 

Meanwhile I've 3D printed a fuel tab that slides and registers against the wing and give us a visual reference about 1in below the top of the main tank.

You can download it here : https://www.thingiverse.com/thing:5300397

This is working so far and I hope to find a better solution later!

 

Thanks

[pagirard]

On 3/6/2022 at 1:27 PM, kortopates said:

CIES fuel senders via an EDM-900 mostly solves the fuel level/remaining question for my mooney with Monroy tanks. it would need another sender or moving the outboard sender to the outboard monroy tank extension to get a better solution.

Before the CIES i relied on the fuel hawk dip stick as well. It works fine as long as wings are laterally level.


Sent from my iPhone using Tapatalk

This sounds very interesting/appealing to me. May I ask a few more details about the senders and your particular configuration ? How many senders are you using in the main and aux tanks per wing ? And how did you program the EDM-900 to teach the fuel remaining based on the main and aux fuel senders reading knowing that the tanks are connected ?

 

We just put a deposit down for a total panel makeover and our engine monitoring will be handled by the G3x, and I was wondering if we should have fuel senders added to the aux tanks.

Thanks in advance

 

 

[carusoam]

A Mooney fuel tab….

Very interesting…

There are so many variations of Mooney fuel cap mounts… very few are the same…

Use caution with plastic devices and gasoline… some polymers have a tendency to absorb gas and swell… or dissolve into gas and redeposit where the fuel is evaporated….

+1 for methods to know how much fuel is actually in there…. 

PP thoughts only. Not a plastics guy…

Best regards,

-a-

[carusoam]

On 3/11/2022 at 11:10 PM, pagirard said:

This sounds very interesting/appealing to me. May I ask a few more details about the senders and your particular configuration ? How many senders are you using in the main and aux tanks per wing ? And how did you program the EDM-900 to teach the fuel remaining based on the main and aux fuel senders reading knowing that the tanks are connected ?

 

We just put a deposit down for a total panel makeover and our engine monitoring will be handled by the G3x, and I was wondering if we should have fuel senders added to the aux tanks.

Thanks in advance

 

 

The best most useable fuel senders are made by Ceis…

They have a really strong engineer that is familiar with GA tanks, and options…

Since you like the math…. Curving fitting over several discrete data points…

Expect a pair of Ceis floats for each wing probably works very well….

calibrating a data point after each gallon added…. Would be the first day’s activity…

We have the Ceis guy around here… @fuellevel…

Best regards,

-a-

[pagirard]

17 hours ago, carusoam said:

A Mooney fuel tab….

Very interesting…

There are so many variations of Mooney fuel cap mounts… very few are the same…

Use caution with plastic devices and gasoline… some polymers have a tendency to absorb gas and swell… or dissolve into gas and redeposit where the fuel is evaporated….

+1 for methods to know how much fuel is actually in there…. 

PP thoughts only. Not a plastics guy…

Best regards,

-a-

I would like to point out that the tab is only used when fueling and therefore the interaction plastic <-> fuel are kept to a minimum

 

Here is a picture in action, the arrow is to orient the gauge toward the fuselage of the plane insuring a constant positioning

 

There is a dimple in the back of the tab to register it against one of the hole in the tank neck

 

Hope this helps

 

Pierre

[carusoam]

Pierre,

Great reply!

Thanks, I missed the fine details…

Thank you!

Best regards,

-a-

[47U]

On 3/11/2022 at 8:05 PM, pagirard said:

This makes fueling and knowing how much fuel we have on board a bit complicated. The previous owner gave us a nice chart to use on each tank with the universal fuel gauge.

I’m curious as to why your right aux tank is full at 10.5 on your dipstick, while the left aux tank is full at 13.0?  What would account for this? 

 

[pagirard]

I asked myself the same questions - in blue and green are the measurement points from the previous owner. My assumption is that the plane isn't sitting flat in his hangar ? But your guess is as good as mine.

 

I'm planning to redo this calibration procedure one day and I'll start with recording the wings angle

[47U]

33 minutes ago, pagirard said:

I'm planning to redo this calibration procedure one day and I'll start with recording the wings angle

Good plan.  Afterward you’ll have confidence in the results.  Perhaps the previous owner hit some wing structure at the bottom of the right tank with the dipstick.  Interesting.  

I like your fuel tab insert.  Nice job.