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Fuel tank quantity 48 or 52?


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I own a 1964 M20C.  Serial number 2799.  The POH says that I should have the 52 gallon tanks.  However it also says that I should have the pull ring to drain the fuel selector.  I do not have that.  Mine is like the 62 and 63 models that have 48 gallons.  Is there any way to check this without draining the tank and refilling it?

Also in the POH which cruise performance numbers should I use?  The ones in the front of the manual or the ones in the very back?

I am using the POH that says it is for a 1965 but with the supplements for the 62 63 and 64 in the rear…

 

The way it is written is as clear as mud.......

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What do the labels on the tanks themselves say? Right beside the fuel type, mine says "Capacity 26 US GALS" on each wing.

 

You can figure out the performance tables. Set power using one of them and see what you get. Write down your power settings, altitude, altimeter, OAT and airspeed. Then on the ground you can compare the results against all of the tables and see which one is closest. You may want to try two different power / altitude combinations.

 

Personally, if yours is a 64 model, I'd go with the set labeled for 1964 rather than 1965. Mooney liked to tweak the planes between model years.

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I suspect you have 48 usable and that's how you ought to plan.

 

But I have not found anything documented in Ball's or Garrison's books on which serial number the change to 52 was made. Your's is a late '64 ('64 serial numbers: 2623-2806). That "generic POH is not evidence one way or the other. 

 

This summary page (note 4) indicates '65s should have 52 but I see typos so I would not take that is definitive... 

http://www.lasar.com/userfiles/file/Mooney-Specification-and-Performance-Guide.pdf

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your serial number was right arounf the time the changed over to 52 gallons so there is a possability you ended up with an older wing, there is also the possability that your wing was damaged at some point in time and replaced with an older wing. as stated earlier you can tell by the fuel caps, 52 gallons flush mount, 48 gallon stopper caps with door.

Brian

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I have flush mount caps so I assume 52 gallons ........

 

Just looked at a picture of my gauge.  It says 156 lbs so I assume 52 gallons,,,,but it could be wrong...like I said earlier I have the old fuel selector when I should have the later one.

 

I usually land with a ton of fuel so its never been an issue....however I will be taking it coast to coast soon with some longer max endurance legs coming my way...

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Jim-

I have SN 2673 and I have 52 gallons.

My first M20C was "modded" to remove the pull ring. Not sure if it was legal, but I left it alone. Any chance yours was changed?

I can't find the change in the log books but the cutout in the floor interior suggests that it may have had it at one time....

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  • 6 years later...
On 2/16/2015 at 5:17 PM, Jim Peace said:

I can't find the change in the log books but the cutout in the floor interior suggests that it may have had it at one time....

I know I'm resurrecting a 6 year old post here, but I couldn't help but share an interesting fact. My M20C is the next serial number in line as yours (S/N 2800) and I do have the oil drain with labeled 52 gallons. I was trying to figure out what my actual usable fuel was. That's how this skeleton was pulled from the crypt. 

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49 minutes ago, Huitt3106 said:

 I was trying to figure out what my actual usable fuel was. That's how this skeleton was pulled from the crypt. 

I do not think there is a unusable/usable fuel number....

I plan to land with 10 gallons....I installed a JPI900 and have the CEIS fuel senders....pretty accurate....

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2 hours ago, Huitt3106 said:

I know I'm resurrecting a 6 year old post here, but I couldn't help but share an interesting fact. My M20C is the next serial number in line as yours (S/N 2800) and I do have the oil drain with labeled 52 gallons. I was trying to figure out what my actual usable fuel was. That's how this skeleton was pulled from the crypt. 

Next time you go on a long cross country do this, assuming you start with two full tanks:

- take off and run 1 hour on one tank

- switch tanks 

- fly on that tank until the engine starts to quit due to fuel starvation

- quickly turn on boost pump and switch to the fuel tank you took off on

- land at your fuel stop.  

-  fill up empty tank.  Reading on gas pump is how much useful fuel you have in that tank.

Fill up 6 gallons at a time is a good opportunity to collect data for calibration of fuel senders if you have a digital engine monitor.  You can avoid engine starvation and startling passengers by having co-pilot stare at fuel pressure gauge and tell you when it starts to plummet.

Repeat at convenient time for the other tank.  

This is a good thing to get to know your ship.

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I do not think there is a unusable/usable fuel number....
I plan to land with 10 gallons....I installed a JPI900 and have the CEIS fuel senders....pretty accurate....

The installation of the JPI includes calibration of the fuel senders which greatly improves the accuracy no matter which fuel senders you have.
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When I resealed the tanks in my C, the FBO charged my for 52.5 gallons. Both were full enough that some ran down each wing when I opened them on inspection. 

Memory tells me that the type Certificate says 1/2 gallon unusable. 

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2 hours ago, Hank said:

Memory tells me that the type Certificate says 1/2 gallon unusable.

 

1 hour ago, Raptor05121 said:

IIRC I had 0.3-0.5 gal unusable.

From the TCDS, 3.4lbs or 0.56gal for the b, c, d, e, and g models. (Thanks Hank)

image.png.a0f46231e455cedcab206cfb2efa2037.png

Edited by Mooney Dog
Incorrect info
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13 minutes ago, Mooney Dog said:

 

From the TCDS, 15lbs or 2.5gal for the b, c, d, e, and g models. 

image.png.a0f46231e455cedcab206cfb2efa2037.png

We read differently. Let me zoom in:

Screenshot_20210820-200226_Chrome.jpg.9d69539691393aaafb1ee0e0b6573f3e.jpg

I  see 3.4 lbs for M20-B, C, D & E, which is 0.57 gallons. 

But I also see 15 lb. for M20-F and J, which have 64 gallon tanks.

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9 minutes ago, Hank said:

We read differently. Let me zoom in:

Screenshot_20210820-200226_Chrome.jpg.9d69539691393aaafb1ee0e0b6573f3e.jpg

I  see 3.4 lbs for M20-B, C, D & E, which is 0.57 gallons. 

But I also see 15 lb. for M20-F and J, which have 64 gallon tanks.

DOH. Absolutely correct. I was reading the F and J numbers. Thank you for double checking. 

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