Determining Fuel Quantity

[Steveolyo]

I have a '69 F model with bladder tanks. It burns about 9 gallons an hour. In the past I have flown with full tanks but now my teenagers weigh more so I need to fly with less fuel on trips. 

I don't know an accurate way to gauge the fuel in the wings. Because the bladder tanks don't show any gas when there is still 7 or so gallons left and I don't have a stick that is calibrated, I would like to know what other mooney pilots have used to determine less than full tanks. Like say 20 gallons in each wing.

I've thought of getting a scale like those used on race cars to weigh 4 wheels simultaneously. Then I would be able to calculate how much fuel I have based on weight. Has anyone heard of that? 

Oh, I've also used the gauges, not sure how accurate they are on the bladder tanks.

I'd like to hear your ideas and comments.

[Oldguy]

Sounds like the simplest thing to do would be to fly a tank empty (or almost and then drain it) and calibrate a stick. If you do it a few gallons at a time, you can also have someone check the fuel gauge for the wing you are filling and see how it reads at the different levels.

Just a thought.

[skydvrboy]

Aside from installing CiES fuel senders and connecting it to new fuel gauges, I think the best solution is to make your own fuel sticks.  The process is very simple and yields accurate results to within a gallon. 

Step 1: Fly one tank empty.

Step 2:  Fill tank and record how many gallons go in.

Step 3: Repeat steps one and two for the other side.  Now you know your exact fuel capacity for each tank. (if they are different mark one side of your fuel stick for each tank)

Step 4: Go fly and before refueling make a mark on your fuel stick of how much fuel is in each tank.

Step 5: Fill each tank up and note how many gallons it took.  Now subtract that number from the total for that tank.  Record on your stick how many gallons you had in the tank at that mark (to the nearest 1/10th of a gallon).

Step 6: Repeat steps 4 & 5 on every flight until you have lots of marks on your fuel stick.

You will have VERY accurate fuel sticks that are customized for  your specific tank/bladder combination.

[skydvrboy]

@Oldguy's method works well too, but you have to be patient to let the fuel flow through all the little holes and equalize before you mark your stick.  I did it that way first and wasn't patient enough which caused me to have more fuel than the stick would show.

[M20F-1968]

The most reliable way is a fuel totalizer, a pen, some paper and simple math, crossed referenced by the other suggestions above.  I think you will find the fuel totalizer to be the most accurate of them (and of course the CIES senders and JPI 930 which you do not have).  

If you are using the original 69 F model senders, you should upgrade to at least the Rochester senders.  I recently changed to the CIES senders and have several rebuilt Rochester senders for sale with certification of the rebuild by Airparts of Lockhaven).

John Breda

[carusoam]

3 hours ago, Steveolyo said:

I have a '69 F model with bladder tanks. It burns about 9 gallons an hour. In the past I have flown with full tanks but now my teenagers weigh more so I need to fly with less fuel on trips. 

I don't know an accurate way to gauge the fuel in the wings. Because the bladder tanks don't show any gas when there is still 7 or so gallons left and I don't have a stick that is calibrated, I would like to know what other mooney pilots have used to determine less than full tanks. Like say 20 gallons in each wing.

I've thought of getting a scale like those used on race cars to weigh 4 wheels simultaneously. Then I would be able to calculate how much fuel I have based on weight. Has anyone heard of that? 

Oh, I've also used the gauges, not sure how accurate they are on the bladder tanks.

I'd like to hear your ideas and comments.

Steve,

You are asking an age old question... but have done it using different words.... and a lot of them... 

1) Filling the tanks...

2) Partial filling...

3) Calibrating a fuel stick...

4) Using a fuel stick...

5) Getting mechanical fuel gauges on the wing to read directly the fill level...

6) Getting Ceis fuel level instruments... (for use in flight)

 

These are some of the different variations to help you find your answer...

Best regards,

-a-

[Ragsf15e]

Until you do all the stuff above, can you just use the metal tabs that hang down from the filler neck?  Mine doesn’t have bladders, so you’ll have to figure yours, but if the fuel is touching the bottom of my tab, that tank has 25 gallons.  If you do both tanks at tabs, you’ve got 50 gallons.  Buys me 84 lbs more useful than topping it off.

[M20F]

3 hours ago, Oldguy said:

Sounds like the simplest thing to do would be to fly a tank empty (or almost and then drain it) and calibrate a stick. If you do it a few gallons at a time, you can also have someone check the fuel gauge for the wing you are filling and see how it reads at the different levels.

Just a thought.

+1

[Hector]

Fuel stick. Keep it simple. Empty one tank then add 2 gallons at a time while making marks on a paint stick. Save that stick as the master to keep in the hangar and make a duplicate using the master for daily use. I use mine before every flight to compare with my fuel totalizar.


Sent from my iPad using Tapatalk

[Ned Gravel]

On 10/26/2020 at 10:30 PM, Hector said:

Fuel stick. Keep it simple. Empty one tank then add 2 gallons at a time while making marks on a paint stick. Save that stick as the master to keep in the hangar and make a duplicate using the master for daily use. I use mine before every flight to compare with my fuel totalizar.


Sent from my iPad using Tapatalk

+1.

Fuel stick reads (confirms) quantity during walk around.  Wristwatch tells me what fuel remains while in flight. Always plan on 10 gph. Often experience less, but the planning is sufficiently conservative (without going overboard) to keep calculations within the margins.  
 

Looking at the gauges is never a satisfying activity. 

[carusoam]

As far as weighing the plane to determine how much fuel is in it...

I can’t think of a more complex way to get a randomly wrong answer...
 

Did your remove all the baggage before you fill the plane, or was that after? 

So is that baggage you have in the calculation or is that fuel?

Are you going to jack up the plane to lift it on the scales or do you have to push it up onto the scales...

Got a pic?

Sure sounds harder than using a fuel stick, and less accurate with no way to share the experience...

But, if you want to be an inventor, and use a unique system, and not let somebody else find the short comings... this could work perfectly! 

The advantage of the factory built airplane... All the quirkiness has been defined already... minimizing surprises...

If you like surprises... start doing things differently.... kind of a factory built conundrum...  

PP thoughts only, not a mechanic...

Best regards,

-a-

 

[Steveolyo]

15 hours ago, Ragsf15e said:

Until you do all the stuff above, can you just use the metal tabs that hang down from the filler neck?  Mine doesn’t have bladders, so you’ll have to figure yours, but if the fuel is touching the bottom of my tab, that tank has 25 gallons.  If you do both tanks at tabs, you’ve got 50 gallons.  Buys me 84 lbs more useful than topping it off.

I don't have metal tabs hanging down. Maybe they were taken off when the previous owner upgraded to bladder tanks, or maybe they were. not originally there.

[ArtVandelay]

Because the bladder tanks don't show any gas when there is still 7 or so gallons left...

If I can’t see fuel, I consider the tank empty.

I have wing mounted gauges, but I doubt they could be retrofitted to bladder tanks.

[TTaylor]

Sent P-message with my data for a 54 gallon bladder stick.

Here is what I have if others are interested complied and averaged from several aircraft:

 

	Bladders	Reg
Inches	54	62
0	6	6
2	13	15
4	19	23
6	24	28
8	27	32

 

 

Edited October 27, 2020 by TTaylor

[Steveolyo]

12 hours ago, carusoam said:

As far as weighing the plane to determine how much fuel is in it...

I can’t think of a more complex way to get a randomly wrong answer...
 

Did your remove all the baggage before you fill the plane, or was that after? 

So is that baggage you have in the calculation or is that fuel?

Are you going to jack up the plane to lift it on the scales or do you have to push it up onto the scales...

Got a pic?

Sure sounds harder than using a fuel stick, and less accurate with no way to share the experience...

But, if you want to be an inventor, and use a unique system, and not let somebody else find the short comings... this could work perfectly! 

The advantage of the factory built airplane... All the quirkiness has been defined already... minimizing surprises...

If you like surprises... start doing things differently.... kind of a factory built conundrum...  

PP thoughts only, not a mechanic...

Best regards,

-a-

 

Yes that does seem like a strange way, but we're all strange in different ways. I would have the plane completely empty. I probably wouldn't do this. But it would be good to know the weight of the plane from an actual measurement to be sure its not overloaded. Every summer there is at least one local problem or crash from an overloaded plane and for me and my family our weights have gone up. My two kids and wife and myself have a combined weight of 640 lbs, 80lbs for baggage, the plane weighs 1701, that brings the total to 2420, and the max takeoff is 2740 so that leaves 320lbs for fuel or 53 gallons. 

So as an experiment, or final check, I'd like to actually weigh the plane loaded and see if the weight matches the calculated weigh

[MBDiagMan]

Unless you want to spring for a JPI and the ultra precision sensors, a fuel stick is the only way to go.

[Steveolyo]

10 hours ago, TTaylor said:

Sent P-message with my data for a 54 gallon bladder stick.

Here is what I have if others are interested complied and averaged from several aircraft:

 

	Bladders	Reg
Inches	54	62
0	6	6
2	13	15
4	19	23
6	24	28
8	27	32

 

 

Thanks. I'll be emptying tanks and marking a stick. I'll see how it matches with yours. 

[carusoam]

6 hours ago, Steveolyo said:

Yes that does seem like a strange way, but we're all strange in different ways. I would have the plane completely empty. I probably wouldn't do this. But it would be good to know the weight of the plane from an actual measurement to be sure its not overloaded. Every summer there is at least one local problem or crash from an overloaded plane and for me and my family our weights have gone up. My two kids and wife and myself have a combined weight of 640 lbs, 80lbs for baggage, the plane weighs 1701, that brings the total to 2420, and the max takeoff is 2740 so that leaves 320lbs for fuel or 53 gallons. 

So as an experiment, or final check, I'd like to actually weigh the plane loaded and see if the weight matches the calculated weigh

That would be a cool WnB automation step! 

There are a few things you can do... when you own the hangar...

Some people store their planes jacked off the ground for long periods.... good for donut health, and tire cords...
 

Cutting holes in the concrete to allow the installation of scales would be interesting... getting data wifi’d  Out of the scales would be a nice touch...   

The heights would need to match pretty closely to allow the plane to roll on/off the scales....

Some people have Heated their hangar floors... yours could automatically do the WnB!  

 

Nothing more important than good WnB data... especially when the plane is new to you... or when it is at MGTW... or a hot day... or a high altitude departure...

Nothing like good fuel info... we/MS has lost a few planes over the years due to empty tanks...

PP thoughts only, not a CFI...

Best regards,

-a-

 

 

[Steveolyo]

1 minute ago, carusoam said:

That would be a cool WnB automation step! 

There are a few things you can do... when you own the hangar...

Some people store their planes jacked off the ground for long periods.... good for donut health, and tire cords...
 

Cutting holes in the concrete to allow the installation of scales would be interesting... getting data wifi’d  Out of the scales would be a nice touch...   

The heights would need to match pretty closely to allow the plane to roll on/off the scales....

Some people have Heated their hangar floors... yours could automatically do the WnB!  

 

Nothing more important than good WnB data... especially when the plane is new to you... or when it is at MGTW... or a hot day... or a high altitude departure...

PP thoughts only, not a CFI...

Best regards,

-a-

 

 

I have the plane in a nice hangar. The scales are wireless and only about 1" thick. I know there is an A&P who does W&B with scales out of Evanston, WY. With all the changes to a plane over the years a real number would be nice to have vs. calculations which I know aren't 100% accurate. For example when I look through the logs at radio installations, the arm is sometimes calculated from the front of the radio and sometimes from the back. Probably should be calculated from where the COG of the radio is. I'm sure these are minor differences especially compared to whether you sit in the plane with the seat scooted all the way back, vs all the way forward. On the other hand, scales can be off a little as well so getting a true calibrated weight might be near impossible.

I've had the plane for 6 years, so it's not new to me, but I usually fly well within the envelope with full tanks. It's only the times with 4 people in the plane that I obsess over W&B and need to know the true fuel weight.

Thanks for the advice. I'll mark a stick now that I need to know.2

[carusoam]

Getting the actual weights for a good WnB requires extra effort... 

There is a procedure for each Mooney, available from the maintenance manual...  

Anybody can do it... getting it right, takes the extra effort...
 

There are a few threads around here regarding proper weighing techniques... emptying the tanks, where to put that fuel safely... 

We have seen a few WnB calculations that made mistakes from the factory...

Oddly, our reference point is a bolt on the front nose gear... the plus and minus from this point is critical...

The complex sign handling has been a challenge for some people...
 

When you have all your data cleanly written out... share it around here... it makes an excellent conversation... 

Best regards,

-a-

[RobertGary1]

I can count on one hand the number of times I’ve filled the tanks of my F to the top in 20 years. I have a calibrated stick but it’s for sealed tanks not bladders. Not sure if it’s the same. I have 32gal/tank.  
 

-Robert 

[ArtVandelay]

I have the plane in a nice hangar. The scales are wireless and only about 1" thick. I know there is an A&P who does W&B with scales out of Evanston, WY. With all the changes to a plane over the years a real number would be nice to have vs. calculations which I know aren't 100% accurate. For example when I look through the logs at radio installations, the arm is sometimes calculated from the front of the radio and sometimes from the back. Probably should be calculated from where the COG of the radio is. I'm sure these are minor differences especially compared to whether you sit in the plane with the seat scooted all the way back, vs all the way forward. On the other hand, scales can be off a little as well so getting a true calibrated weight might be near impossible.

I went through all the W&B changes, about a 100 of them, approximately 20 mistakes, in the end they mostly canceled out, and was off by only 2 lbs. I have a spreadsheet with actual vs corrected entries.

[Jim Peace]

you are flying your family onboard.....the answer is simple

JPI900 and CiES fuel senders......and the ultimate calibration

It is so nice to know to the gallon what you have on board

 

[MikeOH]

10 hours ago, Jim Peace said:

you are flying your family onboard.....the answer is simple

JPI900 and CiES fuel senders......and the ultimate calibration

It is so nice to know to the gallon what you have on board

 

I look at the super accuracy of the CiES system as a 'nice to have,' not need to have equipment.  Here's my reasoning:

I make sure I land with at LEAST 1 hour fuel; that's only 10 gallons, even though I burn 9 gph, or less, based on actual history.  If you're not a fan of running a tank dry, that 10 gallons isn't even in one tank.  

My fuel totalizer (FS450) is within 2 gallons at fill-up (that's only 12 minutes of flying time!!).  And, I stick the tanks before each flight and cross check with the totalizer; always agrees to within 2 gallons.

Bottom line, if I'm down to NEEDING to know "to the gallon" then I've screwed up, BIG time!

[carusoam]

Ceis is nice...

But, if you don’t have an accurate FF gauge...

It is really hard to tell you have leaned the engine properly...

Goofing up the leaning procedure can easily add a gallon or two to the burn rate...

Or... if something isn’t working properly... the FF can really be wrong...

Some old schoolers like that lean til rough, then add some mixture knob twist back in....
 

One semi blocked FI... lean til rough may be burning 14gph... enriching from there will be 14+... while expecting it to be near 10gph...

With precision instruments we get choices...

Without precision instruments...we get different choices... that aren’t as good...

Going Ceis is an optimum thing to do... it requires having a Decent engine monitor to support it properly...
 

So... by the time you have an engine monitor That supports primary engine information... Have the FF instrument connected to it... backed up with the Ceis fuel level instruments... and connect it to the WAAS gps...

There is one good thing.... downloading and sending data to savvy is still free... 

Don’t run out of fuel....  Whatever works is good. If it doesn’t work, that’s bad...

Best regards,

-a-