Bravo’s with Monroy LR Tanks

[DVA]

It’s Father’s Day so I thought I'd relax and share something with other dads that I know I wish I could have found this easily - a way to tell how much fuel a Bravo with Jose Monroy’s LR tanks really has in it!

Thanks to the great guys at Weber Aircraft Service in Lancaster PA., who were very happy to help me solve the mystery, I have here a chart which can be used to get a very close reading of the amount of fuel in a wing.  The disclaimer here is simple: Use this at your own risk, and it’s up to you to verify the results.  A brief background:

The M20M has panel fuel gauges that can (in most installations) be adjusted for three conditions: 1) to show empty with unusable fuel in the wing; 2) to annunciate a “low fuel” condition which should be, according to the Maintenance Manual, be about 2.5-3.0 gallons of useable fuel remaining; and 3) to show full tanks. I am told these setting drift over time and the gauge becomes less and less accurate. The panel gauges are adjusted to be “calibrated” for use in level flight, which means they will be different on the ground. To solve for this, Mooney has an option for wing gauges that show the approximate fuel level in each wing, calibrated for use only on the ground when the airplane is on a flat and level surface, which means they will read differently in the air.

Stock Bravo’s have a total fuel load of 95 gallons, with 89 gallons considered usable. That’s 44.5 per side.

Monroy cleverly designed a system for many models that adds tank space for additional fuel to extend the range of the aircraft. For the M20M with speed brakes the Monroy tanks add 29 additional useable gallons, 14.5 per side. So a Bravo, with speed brakes, and Monroy LR tanks will have a useable capacity of 118 gallons or 59 gallons a side.

The **only** issue with this is that the Monroy Tanks are designed to feed from and flow out of the main tank system, and they do this in a non-linear fashion as it relates to fuel quantity. The problem is that the panel and wing gauges are calibrated for a linear fuel drop and as such become inaccurate (as shown) when fuel fills and drains from the LR tanks.

Jose has little stickers that are affixed to the panel gauges that show this error and the correction needed, but if the panel gauges are not calibrated correctly in the first place, then all bets are off.

Weber did two things for me - they calibrated the panel gauges which were “way off”, and they calibrated an old fashioned fuel stick for me so I never have to guess again. To get this done, I spent all of my Father’s day allowance.

First you need a Universal XL 16” Fuelhawk fuel stick, here's a link to Aircraft Spruce they are available at most pilot shops and on Amazon.

Next, print the attachment: Remember this is only for the Mooney M20M TLS Bravo, with speed brakes and Monroy LR tanks.

Happy fueling!

Dave

[Edit: Please also remember that you must wait a few minutes after fueling to allow the fuel to settle into the Monroy tanks. Fuel seeps in by a rather small opening and you need to give this time to equalize for an accurate reading]

 

 

Edited June 19, 2016 by DVA

[Piloto]

Models M20M, M20R, M20S and M20TN all have the same tank cavity volume. What make them different in fuel capacity is an internal conduit at the filler hole that limits the amount of fuel you can put in with a normal hose nozzle at full flow. As the fuel reaches the bottom of the conduit the conduit will quickly fill up giving the impression of full tank. When the hose nozzle is closed the fuel level in the conduit will gradually come down. If you slowly fill the tanks to the skin top all the models will hold 100+ gals. With the Monroy LR they will hold 130+ gals. This why in many cases the fuel flow computer indicates a smaller fuel amount in the tanks than the actual amount onboard.

José

[Godfather]

16 minutes ago, Piloto said:

If you slowly fill the tanks to the skin top all the models will hold 100+ gals. With the Monroy LR they will hold 130+ gals.

I took a long time to fine tune the FF on the JPI.  With this calculation and carefully filling the tanks after max usage in level flight I came up with ~102.5 gals of usable fuel in my 2001 stock 89 gal tanks.

[DVA]

Just for clarity - the chart above, using the Fuelhawk stick, was based on actual gallons added to the tank. At “7” on the stick, the tank is “full” per the POH plus the extra capacity as shown in the Monroy supplement, but will look like it can hold more - hence José’s explanation.

10 hours ago, Godfather said:

I took a long time to fine tune the FF on the JPI.  With this calculation and carefully filling the tanks after max usage in level flight I came up with ~102.5 gals of usable fuel in my 2001 stock 89 gal tanks.

Godfather, I am curious why you had issues tuning the FF? I have not seen a modern fuel transducer that was not spot on if you use the K-Factor stamped on the device?

[Danb]

Jose you explains mine, if I get it to the skin I get approx. 134 gal., generally about an inch from the skin I get 120 gal, based on this do the tanks hold differing amounts i.e.. Dave's Bravo 118 gal mine 130 gal. if so the his calibration would not be useful for me?

[DVA]

On 6/20/2016 at 10:03 AM, Danb said:

Jose you explains mine, if I get it to the skin I get approx. 134 gal., generally about an inch from the skin I get 120 gal, based on this do the tanks hold differing amounts i.e.. Dave's Bravo 118 gal mine 130 gal. if so the his calibration would not be useful for me?

The calibration stick and method will apply to all M20M’s with LR Tanks. Remember, the 7” mark is derived from actually filling 59 gallons on the wing, which is  “full” given the stock tank POH capacity PLUS the Monroy extra capacity. You can stuff more in for sure as Jośe points out - all that would do is show a higher reading than 7” on the stick; which I did not attempt to calibrate. 7” or below has proven to be accurate per the chart above.

Best regards,
DVA

[Danb]

Hey Dave saw your bird at Weber's this afternoon, I made sure Dorns taking care of it.

[DVA]

LOL - Ya and it’s taking care of Dorn! Dorn’s mortgage, Dorn’s car payment, Dorn’s bone-in ribeye with truffle butter...

[Tony Armour]

29.5 gallons and above. That's nice but it's the "below" 29.5 gallons that will kill you 

[1Germaican]

So is it safe to say that the external wing fuel gauge is accurate for quantities below the stick measurements?  Say 20 or 10 gallons remaining?

 

[LANCECASPER]

48 minutes ago, 1Germaican said:

So is it safe to say that the external wing fuel gauge is accurate for quantities below the stick measurements?  Say 20 or 10 gallons remaining?

 

I would say yes generally, but it never hurts in an airplane new to you to start out with a dry tank and put 5 gallons in at a time and see how accurately the wing site gauges display.

[carusoam]

58 minutes ago, 1Germaican said:

So is it safe to say that the external wing fuel gauge is accurate for quantities below the stick measurements?  Say 20 or 10 gallons remaining?

 

Their design, intent, and use….

Is all about accuracy for partial filling of the tanks….

They are calibrated for being on the ground…

Simple and effective.

As usual… check that your system is still working as designed…

 

Attitude on the ground is different than attitude while flying…

 

Combined with calibrated Ceis digital fuel floats… your knowledge of fuel status does’t get any better…

PP thoughts only…

Best regards,

-a-

[Schllc]

Aside from when I topped off my Monroys, and by topping off, I mean going from tank to tank three or four times to let the fuel settle, I NEVER knew how much fuel I had. 
the reason was mostly because you don’t want to carry fuel, so you put 10 gal here, 25gal there and eventually you forget to update the totalizer until after starting, and you’re back to guessing. 
im always overly cautious when taking fuel (by cautious I mean I take more), so I never even come close to fuel exhaustion, but my anal retentive nature didn’t like knowing down to .1 gallons. 
The totalizers on all of my Mooney’s have been far more accurate than any of the gauges. 
It is fun reading the poh supplement regarding the LR tanks while flying tho!

That being said, if you need the capacity it is an awesome upgrade, and…

I think if the day ever comes that we get the UL increase with new gear, Mooney’s with LR tanks are going to be even more coveted than they currently are. 

[carusoam]

1 hour ago, Schllc said:

Aside from when I topped off my Monroys, and by topping off, I mean going from tank to tank three or four times to let the fuel settle, I NEVER knew how much fuel I had. 
the reason was mostly because you don’t want to carry fuel, so you put 10 gal here, 25gal there and eventually you forget to update the totalizer until after starting, and you’re back to guessing. 
im always overly cautious when taking fuel (by cautious I mean I take more), so I never even come close to fuel exhaustion, but my anal retentive nature didn’t like knowing down to .1 gallons. 
The totalizers on all of my Mooney’s have been far more accurate than any of the gauges. 
It is fun reading the poh supplement regarding the LR tanks while flying tho!

That being said, if you need the capacity it is an awesome upgrade, and…

I think if the day ever comes that we get the UL increase with new gear, Mooney’s with LR tanks are going to be even more coveted than they currently are. 

Have you ever had the Cies digital fuel level sensors in any of your Mooneys?

They are a way to back-up the fuel flow system you currently use…

My biggest disappointment with the FF system… forgetting to reset it prior to flight…

With the old analog gauges… they are +/- a few gallons just in interpretation error…

I don’t think Ceis made it into production Mooneys….  They have only been around for a handful of years…

PP thoughts only not a mechanic…

Best regards,

-a-

[Schllc]

14 hours ago, carusoam said:

Have you ever had the Cies digital fuel level sensors in any of your Mooney’s  

I have not, I have said if I ever have to open a wing for a fuel gauge problem I would do it while I was in there. 
but ive been lucky enough so far to not need that step.

 

I have  read a lot of good reviews. 

[carusoam]

11 hours ago, Schllc said:

I have not, I have said if I ever have to open a wing for a fuel gauge problem I would do it while I was in there. 
but ive been lucky enough so far to not need that step.

 

I have  read a lot of good reviews. 

Chances are you won’t need to fix one…

But, the Ceis ones offer increased accuracy… to go with your FF computer…

Getting them installed… would be good during the annual down time…

There have been a couple of learning experiences getting them installed in various Mooneys…

The leader at Ceis has been updated along the way… he is an engineer/sales guy/CEO for the company…

PP thoughts only, not a mechanic or sales guy…

Best regards,

-a- 

[rbp]

I had the CEIS centers installed recently. I will be comparing them to the fuel flow over the next few months

[alextstone]

On 6/19/2016 at 3:56 PM, DVA said:

It’s Father’s Day so I thought I'd relax and share something with other dads that I know I wish I could have found this easily - a way to tell how much fuel a Bravo with Jose Monroy’s LR tanks really has in it!

Thanks to the great guys at Weber Aircraft Service in Lancaster PA., who were very happy to help me solve the mystery, I have here a chart which can be used to get a very close reading of the amount of fuel in a wing.  The disclaimer here is simple: Use this at your own risk, and it’s up to you to verify the results.  A brief background:

The M20M has panel fuel gauges that can (in most installations) be adjusted for three conditions: 1) to show empty with unusable fuel in the wing; 2) to annunciate a “low fuel” condition which should be, according to the Maintenance Manual, be about 2.5-3.0 gallons of useable fuel remaining; and 3) to show full tanks. I am told these setting drift over time and the gauge becomes less and less accurate. The panel gauges are adjusted to be “calibrated” for use in level flight, which means they will be different on the ground. To solve for this, Mooney has an option for wing gauges that show the approximate fuel level in each wing, calibrated for use only on the ground when the airplane is on a flat and level surface, which means they will read differently in the air.

Stock Bravo’s have a total fuel load of 95 gallons, with 89 gallons considered usable. That’s 44.5 per side.

Monroy cleverly designed a system for many models that adds tank space for additional fuel to extend the range of the aircraft. For the M20M with speed brakes the Monroy tanks add 29 additional useable gallons, 14.5 per side. So a Bravo, with speed brakes, and Monroy LR tanks will have a useable capacity of 118 gallons or 59 gallons a side.

The **only** issue with this is that the Monroy Tanks are designed to feed from and flow out of the main tank system, and they do this in a non-linear fashion as it relates to fuel quantity. The problem is that the panel and wing gauges are calibrated for a linear fuel drop and as such become inaccurate (as shown) when fuel fills and drains from the LR tanks.

Jose has little stickers that are affixed to the panel gauges that show this error and the correction needed, but if the panel gauges are not calibrated correctly in the first place, then all bets are off.

Weber did two things for me - they calibrated the panel gauges which were “way off”, and they calibrated an old fashioned fuel stick for me so I never have to guess again. To get this done, I spent all of my Father’s day allowance.

First you need a Universal XL 16” Fuelhawk fuel stick, here's a link to Aircraft Spruce they are available at most pilot shops and on Amazon.

Next, print the attachment: Remember this is only for the Mooney M20M TLS Bravo, with speed brakes and Monroy LR tanks.

Happy fueling!

Dave

[Edit: Please also remember that you must wait a few minutes after fueling to allow the fuel to settle into the Monroy tanks. Fuel seeps in by a rather small opening and you need to give this time to equalize for an accurate reading]

 

 

 

"I made a thing"... please read above first....

I now own the local small aircraft maintenance shop at my home field in south MS.  Among many other things, we upgrade avionics from time to time with JPI engine monitors, etc. and I cannot STAND the look of stick on labels on panels so I invested in a laser engraver.  As a side project,  I made a placard of the above, see photos below...If anyone wants one, I'm firing it up tomorrow again and I'll make one for you.  You will need to order your own fuel level gauge (shown below for SKU number at Aircraft Spruce).

 

 

 

 

 

 

 

 

[Fly Boomer]

I'm a big believer in sticking the tanks.  I would love to have one of those placards.  How much?

[alextstone]

I'm a big believer in sticking the tanks.  I would love to have one of those placards.  How much?

Nada. PM me an address.


Sent from my Pixel 5a using Tapatalk

[carusoam]

Way to go Alex!

Got any pics of your local establishment?

Best regards,

-a-

[Fly Boomer]

@alextstone BTW, which filler do you use to get the total fuel on one side.  I always thought the factory tank would just be full all the time until the Monroy tank was empty, and then start going down?

[carusoam]

Just now, Fly Boomer said:

@alextstone BTW, which filler do you use to get the total fuel on one side.  I always thought the factory tank would just be full all the time until the Monroy tank was empty, and then start going down?

Boomer,

It helps when everyone knows which Mooney you are flying…

Some Monroy tanks are separate from the mains… but, not by much….

Others are essentially a larger main tank…

Chances of emptying a tank before drawing from the next are really slim…

They gravity feed… and one is not very high compared to the other…

Best regards,

-a-

[Fly Boomer]

1 minute ago, carusoam said:

It helps when everyone knows which Mooney you are flying…

It's a 252.  I guess I don't understand how quickly or slowly the fuel migrates from the Monroy tank into the factory tank.

[carusoam]

4 minutes ago, Fly Boomer said:

It's a 252.  I guess I don't understand how quickly or slowly the fuel migrates from the Monroy tank into the factory tank.

The fuel migration only has to be faster than the engine burns it…

You can experiment while filling the tank from the uphill end… and watch what is going on in the downhill end…

See if you have a layout drawing of your tank set-up… 

It is a POH requirement, so an STC will have the updates….

If you have speed brakes there may be a space between your mains and your Monroys…

M20Ks probably have the most revisions to the fuel system… including the flapper valves on the fill holes…

When filling… some slowness near the top is expected… tiny holes in the tops of the ribs allow air to move from one area to the next… this can take several minutes to settle out…

Some poor reseal jobs have accidentally filled the small holes….  Same for fuel draining through the bottom….

PP thoughts only, not a mechanic…

Best regards,

-a-