M20S actual fuel capacity

[jhbehrens]

Hi

 

I own a '99 Eagle with the 310HP conversion. Hence I can carry 89 gallons of fuel according to the POH supplement.

 

I have always assumed 75 gallons of (usable) fuel is reached when you fill to the bottom of the filler neck (I use the bottom rivet as a marker) and 89 gallons is when you fill it right to the top. I usually only fill to 75.

 

On a recent flight though I left with 75 gallons, burnt 39 gallons according to my totalizer so arrived with 36 gallons remaining. I then refueled, not even quite to the top and took in 60,5 gallon, suggesting that the tanks can actually contain more than 96,5 gallons of usable fuel. I'm now trying to work out whether my totalizer is faulty or whether the tanks actually hold more than 89 gallons of usable fuel.

 

Does anyone know what the full capacity of the tanks on an M20S is? How (other than ensure I add max 7 gallons on each side after reaching the bottom of the filler neck) do I ensure I don't go above 89 gallons? Those with M20S' - do you use a particular spot on the filler neck?

 

Thanks

Jorgen

[tascher]

Jorgen,

I fly a R rather than a S, but I'd believe that all the long bodies have the same standard tanks. The differences are in the filler necks and placarding. The "top of the bottom" of my filler necks get me to 44.5 per side (the bottom of the filler neck is higher closer to the front of the wing - maybe it's level when the plane is level rather than nose high on the ground) for a total of 89 gallons. There's quite a bit of space from there. I don't know if the factory will still sell it, but I'd believe there was an STC to drill a vent hole high up on the filler neck and take the marked capacity to a total of 100 or 102 (current production standard tanks - no different from yours - are marked 100 gal total). To the first part of your question, it's unlikely that anything is wrong with your totalizer - get the air trapped around the filler neck out and fill it right to the very top of your wings and you have over 100 gallons. As to a reliable way to stay at 89 without draining your tanks, filling to 44.5/side and then marking your filler necks, I don't know.

Tom

[tascher]

...and one other difference, the calibration/max displayed quality on the fuel gauges. I can fill to the point where it's sloshing out the filler opening and I'll still see 45/side on the Moritz gauges until I burn off enough fuel for the gauges to come into play on the downside. Is the S max displayed quantity 37.5 (38) per side?

[Cruiser]

"Line guys tell me that ovations come with a 4" neck, a 2" neck or no neck, giving 75, 89 or 102 gallons capacity. According to the supplement above, I am allowed to take up to 51 gallons." 

 

see this thread for more details.

http://mooneyspace.com/topic/12079-selling-m20r/page-2?hl=%2Bovation+%2Bfiller+%2Bneck#entry154556

[PMcClure]

I called the factory about this and asked which serial numbers the supplement applied too. I didn't get a definitive answer. But did confirm the tanks are the same with a capacity of (100 or 102) but the neck limits to 75, 89 or 102 gallons. I have had line guys mistakenly fill past the neck and the fuel gage reads 45 and stays there until below 45. With the neck, air gets trapped in the wing and it is hard to know exactly how much "extra" fuel you have.  

 

I believe the neck was initially installed to limit weight. The R has a max ramp weight above the max landing weight. 

[tascher]

Thanks to Cruiser. I had missed the thread covering this:

"The fuel tank contains 44.5 gal (168.45 li) fuel when level is at bottom of filler standpipe. An additional 5.5 gallons (21.0 li.) of fuel may be added up to the 0.37” hole located top of the neck in the standpipe for a total of 50.0 gallons (189 li.) in each tank."

It would be interesting to know if the 3/8" hole can be added to ease fueling above 89 on planes produce prior to the increase in placarded capacity.

[carusoam]

Discussion on this topic go back about three years...

I recall methods of modifying the filler neck being discussed. In situ drilling can leave pieces of aluminum in the wrong place....

Either way it takes effort and patience and level ground to get the full 100 gallons in the wings...

Use the search key...

Go O!

-a-

[Cris]

The bottom of the filler on the S is 75 gals. and on the R 89 gals. The 310 STC for the S allows for the fuel capacity to be increased to 89 gals. but needs to be measured from an empty tank. There is a Mooney drawing which allows for the tanks to be filled to the top of the wing which gives 100/102 gals. I use a manual fuel tube to determine the actual quantity before flight between 75 gals (bottom of the fill baffle) 89 gals marked on the baffle and and the top of the wing skin.

[jhbehrens]

I can now confirm the M20S will fill up to 102 USG with patience.

[LANCECASPER]

I can confirm that if I overfill my Encore, wanting to squeeze every drop in it for a flight the next day before I store it in the hangar overnight, that it is possible for fuel to seep out the nut plate under the wingwalk. So after having that addressed, I don't do that anymore unless I am taking off right away. Then I feed from that tank first before switching.

[jhbehrens]

Yes - exactly the same in my aircraft.

[carusoam]

Too difficult to drop in to Don Maxwell's from AMS?

Are you able to identify which fastener is allowing the leak?

Patching individual rivets with modern sealants is pretty predictable...

Don Maxwell had taken care of these during the purchase process for my O.

Best regards,

-a-

[jhbehrens]

Too difficult to drop in to Don Maxwell's from AMS?

-a-

 

Yes  and I wouldn't survive the fried chickin'

 

Yes I can. On the 'wingwalk' side its two phillips screws underneath the wingwalk. On the other wing its a line of rivets about mid-wing close to the hull.

[carusoam]

You might want to talk to Mr. Maxwell about the best way to access the rivets...

It might be best from under the wing, removing an entire access panel if you are unable to reach in with a small hand.

Mine was done by Don Maxwell while it was in for it's PPI years ago...

Best regards,

-a-

[kmyfm20s]

I filled my tank the other day until the entire bottom of the stand pipe was covered on my "S" which is 37.5 gal usable. I then added 14 more gallons to give me 51.5 gallons and this is a picture of the fuel level.

I was then able to then add 3.5 more gallons which would make a grand total of 55 gallons in this tank. My next step is to run this tank dry and refill to confirm. I have read other places of tank capacities of 109 but does the picture match other people's fuel levels at 51.5?

[Cris]

The differance is the unuseable fuel which is 3 gals per side. Under perfect conditions you can squeeze 102 gals into the wings plus the 6 gals for a total of 108 gals or so. The 75,89, etc are always useable fuel quantities. I do believe there was a factory option on the R for the Monroy STC which further increased the useful fuel for long range tanks.

[Piloto]

To add even more fuel. Fill up a 5 gallon container for the next day top off. On some Mooneys, specially with LR tanks it takes a day for all the fuel to settle down. Beware that fuel quantity delivered by the fuel truck may vary due to the initial amount in the hose. Not to mention that there maybe discrepancies on the fuel truck meter, they never under read.

 

José 

[PMcClure]

Just a question - is it legal to exceed your placarded maximum fuel amount? 

[kmyfm20s]

The differance is the unuseable fuel which is 3 gals per side. Under perfect conditions you can squeeze 102 gals into the wings plus the 6 gals for a total of 108 gals or so. The 75,89, etc are always useable fuel quantities. I do believe there was a factory option on the R for the Monroy STC which further increased the useful fuel for long range tanks.

So when you get your 102 usable in does the level of fuel look like the picture above or is it to the skins? Following POH I filled 37.5 usable then added 14 more gallons and was left with what is shown in the picture. You can see the vent holes that where drilled per the STC. I'm still going to run the tanks dry and fill from there but I'm curious if I'm getting a more complete fill than others because of the holes.

[kmyfm20s]

Just a question - is it legal to exceed your placarded maximum fuel amount?

I never read or heard that it was not, I also don't see any reason it would be.

[PMcClure]

So we can ignore any placard on the aircraft? I am pretty sure the POH says something like: "the aircraft must be operated within all placarded limits, etc....?  And how to do weight and balance when the POH doesn't show CG of the extra 15 gallons. I hope it is legal, would love to add a few more gallons to the tanks. Personally, I think it is safe, but legal, doubt it. 

[kmyfm20s]

I think if you had a placard that said max allowable fuel it would be different, similar to the baggage compartment. The W&B only goes slightly aft with more fuel. In my plane it hard to to out of the envelope aft I will be well over gross before that would happen.

[PMcClure]

My placard says 44.5 max fuel capacity. I called Mooney and they would not revise the POH or placard unless the plane was within a few specific serial numbers. I don't know why. I agree 100% that envelope, etc.. is well within but legally, you can't do a W&B by the POH if it ain't covered in the POH. 

[kmyfm20s]

If you look at the screen shot the fuel station only goes up to 500 lbs. This is from a newer M20R POH which hold 89 gal usable and at 5.82 lbs/gal it would be 518 lbs of fuel.

My assumption is its ok to carry it out to get the proper moment for the W&B since it's not specifically represented in the POH.

[carusoam]

Limits are in the limits section....?

Early O's POH indicate a limit of fuel per side 44.5 gals. For S/N 29-170 through -199. The decal is above each fuel level indicator on the IP. Another one is surrounding the fuel selector.

My W&B Chart revision is F 9-96...by previous owner...

This chart is the only place in the POH that gives the station addresses in inches. Full fuel (89.0 gal) is over 500lbs and is slightly off the graph....

W&B is critical. But the source of the weight and where it sits is optional... Trade fuel for passengers, or tools in the back...

The chart has limitations to its usability, but it is a standard way for a pilot to do math without the calculator.

What you really want to know is T/O distance for an original Eagle with a two blade prop and compare to the same eagle with 310hp and TopProp...

There isn't much sense in adding extra fuel if it takes too long to get off the ground and over the first tree...

If you fill to the top, you will test how good your cap seals are working. Check your tank vents for critters...

Install more power, install more fuel. STCs are the method of doing so legally, properly and knowledgeably.

Best regards,

-a-