Ovation with Monroy Tanks - Wing Gauges reading

[shorrick mk2]

Very good morning everyone!

 

A point puzzles the new Ovation owner that I am - there is a conversion factor to be applied for the cockpit fuel gauges when the Monroy tanks are installed. However I've found nothing with regards to the wing tank gauge readings.

 

Obviously some correction needs to be applied, but how to determine it? Same ratio as for the cockpit gauge? Different ratio?

 

Help and pointers greatly appreciated!

[BorealOne]

The wing gauges are accurate below 30 gallons. No conversion required. Above 30 gallons they simply read 'full', which is less helpful but still reassuring.

Proper use of the fuel totalizer is the solution for knowing how much fuel remains on board with accuracy.

Sent from my iPhone using Tapatalk

[shorrick mk2]

Thank you! Does that mean that below 30 gallons nothing flows into the extra tanks?

[triple8s]

The aux tanks drain into the mains continuously as the fuel level goes down. Once the the level is down such that the fuel is no longer in the aux tank there is remaining fuel in the main, how much? I guess if the gauges are accurate then what ever they say. I was taught to NEVER trust a fuel gauge so I look at it like what's it even matter? I make it my business to know how much is on board before take off and I know how much she burns an hour and I have a watch. The best gauge is a stick they never fail.

[carusoam]

Welcome aboard Shorrick...

What is the total fuel capacity for your plane?

130 gal?

Things that come to mind....

1) Has your POH been updated with details from the STC?

2) the STC may say something simple like you may have more than or equal to indicated....

3) can you contact the Monroy company directly?

4) can you wait a few hours, possibly, a guy named José (Piloto) might be able to answer this with really good extended fuel tank experience?

Best regards,

-a-

[shorrick mk2]

Thank you for the welcome!

 

Total is 120 gal. Short of trusting the gauges, I have no means of knowing for sure what I begin with short of draining the tanks and pouring it all back in (which I would rather avoid...). Once the initial figure is known, I have no issues relying on fuel totaliser / hourly burn etc. I just need to figure out where I start from

[carusoam]

The POH may also indicate the proper way to make sure the tanks fill properly...

Best regards,

-a-

[Cris]

Do you not have a fuel totalizer like a Miniflow L or an engine monitor with fuel flow? If so you can check the accuracy of the totalizer after a few flights since all of the long bodies hold 100 gals when fueled to the top of the wing skins. I'd then suspect the aux tanks to hold 10 gals/side. Just an educated guess on my part but you can make a fuel stick to enable you to check that amount of fuel in the aux tank.

[DAVIDWH]

Just reprogrammed my Shadin Miniflo to 89 Gal. usable fuel. Was previously programmed to read out full at 95 gal.

 

Sure you are aware that wing gauges are accurate on ground, but inaccurate in air while interior gauges are inaccurate on ground, (Read High)  but (more or less) accurate in cruise level flight.

 

The fuel gauge I rely on most is the read out on the fuel truck meter.

 

Best,

 

DH

[FBCK]

I have a 231 with Monroy 110 gallon tanks and I have the same problem you do, I never know the absolute quantity of fuel I have on board, so I always error on the safe side and find I have more fuel then I think I do.  I use the fuel totalizer method. I the STC paper for my plane there are dip stick measurement for the external tanks to give you an accurate starting point.

[Piloto]

There are some concerns about the total amount of fuel the long bodies will take. Here are some notes that may help:

 

All long bodies (except the Porsche) fuel tank total volumetric capacity is 100 gallons (both wings) no LR installed

The different fuel capacities is determined by the depth of the filler conduit inside the tank. The conduits limits the amount of fuel you can quickly fill in. But if you are patient and slow the fuel nozzle flow to fill to the skin you will end up with 100 gallons even on the M20S. This causes sometimes the fuel totalizer not to agree with the panel gauges. The gauges indicating more fuel remaining than the totalizer.

 

When you add LR tanks the volumetric capacity expands to 130+ gallons when filled to the skin but 120 when filled to the bottom of the filler conduit. This explains why the placard indicates 59 gallons for previous models instead of 65 gallons like on the Acclaim (no conduit). 

 

To simplify things. If the plane has LR tanks the amount of fuel onboard is greater than that indicated by the panel gauges from the mid scale to the Full mark. From the mid scale to the Empty mark the fuel indicated is the actual fuel onboard. So you will always be on the safe side. If filling to the skin top set the totalizer to 100 gallons or 130 gallons if equipped with LR tanks. This way you will get a more accurate correlation with the panel gauges.

 

The wing sight gauges are only accurate below 30 gallons down to 10 gallons.

 

With a 130 gallons the plane becomes heavy to taxi. Have the tires fully inflated and avoid taxing on grass. The nose wheel may get stuck.

 

When contemplating a non-stop full range flight top off also the oil level in the engine. And check your bladder is totally empty.

 

José 

[aviatoreb]

How about this.  Bring both tanks down to something safe, like say 15gal or 10gal on each side.  Then depart and fly around burning on right tank until it goes dry - this is a perfectly safe procedure.  If you anticipate it you can flip the fuel selector at the very first indication of empty - either by engine noise or fuel flow indication.  This is hotly debated as a proper flying procedure but anyway many people do it, to extend range knowing exactly where your fuel is.

 

Now land while you are running on left tank with an empty right tank.  Fill that right tank and note exactly how fuel fills it.

On another occasion do the other side.  I would say depart and do the other tank right away, but now you would be extremely unbalanced with 65gal on one side and 10 gal on the other side.  But you could.

[carusoam]

The point of the question, I think...

Do the LR tanks run dry first? Answer: no, they get used at the same time. The bottom of the wing is higher because of the small dihedral angle.

When the external gauge is reading 30 or less, is there fuel in the LR tank? Answer: yes, some.

The LR tanks will be the first to be empty because of wing geometry.

Rough fuel calculations can safely be performed using the gauges.

Precise fuel calculations can be performed from the fuel flow computer that has been calibrated and confirmed.

Sticking the tank is a great way to know how much the pilot is starting with on the ground. Calibrating a stick is required.

Best regards,

-a-

[Danb]

Jose gave an excellent answer to the question of why the fuel gauge does not read as to the amount in the Monroy when full or over about 66+ gal. Using the fuel totalizer helps quite nicely, my tanks do do agree with all the gauges unti about 30 per side. At first it bugged me but as everything you get accustomed to it. In addition to Jose's remarks when full and sitting around for awhile puts a lot of stress on the donuts. I still feel the Monroys have been the best upgrade to my Bravo, after 8 yrs I'm sure they have paid for themselves in unnecessary landing for fuel, with the M model being so much a gas hog the additional gals. Is a must on long cross countries.,Just landed today and flew over icing for quite some time and was happy not to have to descend for fuel threw 21000 ft of ice.

[marcusku]

My question is similar to the beginning of this thread.  I have a new to me Ovation and am trying to figure out how much fuel I have in the tanks.  The Moritz gauges aren't working properly and the JPI fuel remaining wasn't matching what the site gauges were reading.  Earlier this week the site gauges read 20 & 25 gallons, I filled to the bottom of the standpipe as shown in the picture but only 61 gallons went in suggesting that the site gauges weren't indicating enough fuel.  (45+61=106, 12 gallons short of 118)  I did wait a couple of minutes to make sure the fuel had made it everywhere in the tank.  I reset the fuel computer to full or 118 gallons.  Currently the computer says 40 gallons left while the wing gauges say 35 total.  At this point I don't know if the fuel computer is accurate either but I'll have a better idea on that if I fill it the same next time around.

My question is, should it have been 59 gallons to the bottom of that standpipe?  Maybe the wing gauges actually aren't accurate until a lower level, say 15 gallons remaining or something?

 

[Schllc]

There should be a supplement in your poh with how to read the gauges. 
But my experience with Monroy tanks is that you only really know exactly when you fill up. 
You can actually usually put a little more than the poh says which doesn’t help either. 
the only confidence I have had with a higher than 5 gallon accuracy was the totalizer. 
if that isn’t working it should be easy to fix. 
the analog and digital gauges will be all over the place, and I only used for general reference. If I wanted anything close to precise I used  the totalizer. 

[wombat]

Empty one of your tanks completely by running it until the engine stops while the aircraft is at a normal cruise attitude.   This could be done in the air or on the ground.

Then start adding fuel in known quantities and record the gauge measurements at each increment.    After the first 20 gallons or so, be sure to give the fuel enough time to move between tanks every time you add fuel.

 

Here are the results of when I did this on my plane:  https://docs.google.com/spreadsheets/d/1eCCiLBGDNsSlQaziJ_DnWsNmMHbi8wbwifmRALW9uVo/edit?usp=sharing

[Pinecone]

IIRC my 252 with Monroy has fuel in the aux above 17.5 gallons total 

I calibrated a FuelStick and a Fuel Hawk for my airplane. 
 

BTW, you need more than a couple of minutes for the fuel to flow.  It is only a Dash 4 hose and fitting

[Z W]

19 hours ago, Schllc said:

But my experience with Monroy tanks is that you only really know exactly when you fill up. 
 

This has been my experience too, and with useful payload dropping to 300 lbs with full aux tanks, I don't do that very often.

Usually I will "top the mains" which is supposed to be 75 gallons.  That doesn't account for 1) the amount that doesn't go in because you (or the line guy) have to be patient and fill slowly to really top the tanks (minus), or 2) the amount that slowly flows out of the mains and up into the aux tanks during the fueling process (plus).

I then fly around knowing roughly how much I have, within 10 gallons or so.  The in-dash gauges are inaccurate until the aux tanks are empty, then they get pretty accurate again.  They also disagree with the sight gauges in the wing, which also are inaccurate while there's fuel in the aux tanks, then pretty accurate for a while, but under 10 gallons or so just suddenly drop to zero.

I just make sure I error on the side of too much fuel and don't push it.  Usually I keep an hour of fuel in each main tank as my personal reserve minimum, and then "top the mains" or buy enough for the planned flight just prior to departure.  If ever in doubt land and get more.  

[marcusku]

Earlier in this thread it was suggested that sight gauges remain accurate once down to in my case 30 gallons, but it sounds like that's not the case.  So there must still be fuel in the aux tank area when the level gets down to a level the site gauges can pick up.

At some point I'd like to replace the Moritz gauges with a JPI 900.  If one replaces fuel senders at the same time, will they read the whole range of fuel levels?  Or will they only be accurate once down to a certain level?

[Pinecone]

The gauges will read the same every time the tank is at a given fully level.  It is just that the numbers are not correct.

With an hour or two in the hangar, you have make a cheat card that tells you how much fuel is in the tank at each sight gauge and fuel gauge reading.

Here is mine for my 252 with Monroy.  I did not calibrate the electric gauges, as I knew I was getting Cies senders installed and they would be calibrated to actual levels.

[wombat]

3 hours ago, marcusku said:

Earlier in this thread it was suggested that sight gauges remain accurate once down to in my case 30 gallons, but it sounds like that's not the case.  So there must still be fuel in the aux tank area when the level gets down to a level the site gauges can pick up.

At some point I'd like to replace the Moritz gauges with a JPI 900.  If one replaces fuel senders at the same time, will they read the whole range of fuel levels?  Or will they only be accurate once down to a certain level?

If you can calibrate multiple points on the JPI 900 fuel level, they can be accurate at most fuel levels.   If you have the long range tanks they last 'few' gallons cannot be measured since the top of the long range tanks are higher than the top of factory tanks and the fuel level sensors are only in the factory tanks.

 

 

[Fly Boomer]

On 10/21/2014 at 4:30 AM, shorrick mk2 said:

there is a conversion factor to be applied for the cockpit fuel gauges when the Monroy tanks are installed

There is no conversion factor.  If you have Monroy tanks, keep in mind that there is no fuel level transmitter (the term Mooney uses) in the AUX tank.  You can see in this conceptual diagram that the AUX tank can be anywhere from full to half full, and it won't change the fuel gauge (wing or panel) because the MAIN will remain full.  IRL the relationship isn't so clear cut, but in this conceptual diagram, until you burn enough fuel to empty the AUX tank, the fuel gauges can't tell you how much fuel is in the MAIN, and until you empty the AUX tank, you will have more fuel on board than the gauges indicate.  If your fuel totalizer has been calibrated, it will help you know how much fuel you have on board, and you should maintain generous margins.

 

[Jetpilot86]

I'm still sorting this out so take with a large grain of salt.

There is a thread around here that gives the fuel stick calibration for the 59gal tanks.  It's good for my 118gal Bravo.  FuelHawk stick is less than $20, get the 16" one so it's harder to drop in the tank!  If the cockpit gauges worked, the Monroy POH supplement would tell you that above 22 gal, 1 gal on the gauge = 2 gal in the tank.  Mine stick between 22-33 gal and are useless.  I'm still working on the numbers for the wing sight gauges, but that same ratio is looking pretty good, 2 for 1 gal over 22 gal.  I've yet to do the empty tank verification method yet.  I'm within a couple of gallons between the two now.

What I am doing to work on calibration is the reverse.  Start with a full tank, log the burn on one side precisely, both is possible when completely full, and calibrate the digital fuel gauge by topping one side off after the flight to compare burn/stick/shadin(or other digital).  The caveat on this one I've figured out is you can't just top off one side and forget about it.  The plane will "roll" to the full side and when you put whatever you need in the other side, then you'll need to top of the "full" side again because the airplane rolled back a bit.  Basically, I figure out what the "full" side will need to top off, then put whatever extra I want after that in the other tank.  What I'm going to start doing is the reverse.  Add the lesser tank fuel first, maybe not quite all of it, if I'm close to takeoff/landing limits; then top off the fuller tank to verify the burn, then go back and finish off the lesser tank until I'm happy with the numbers.

Here is the thread with the 59 gal fuel stick calibration numbers:  6th post down on page 1.

Cheers,