Fuel capacity/useable fuel in an F

[warrenehc]

Hello everyone,

I am sorry for asking this question, but I have conflicting information. What I always believed/ understood was that the F model 1967 had 2.5gal of unusable fuel. With a 64 gallon fuel capacity. I just purchased my new to me Mooney and when reading the POH it said it has 64 gallons of useable fuel. In no other place in the POH does it have any other number besides 64 gallons. 
 

So is the fuel capacity 64 and can use it all?

Does it have 66.5 gal capacity and can use 64 gal?

Or is it really 64 capacity and you really can use 61.5?

I’m sorry for asking, I just want to know for planning and safety margin.

[Pasturepilot]

It’s buried in note 1 at the very end of the TCDS. 

15 lb. unusable  

 

[Greg Ellis]

Not to hijack this thread but 48 lbs of unusable fuel for certain K models?  That is roughly 8 gals of unusable fuel?  Seems like a lot.  Nice to see that my little old C model only has about 1/2 gal of unusable fuel (3.4 lbs).

[gsxrpilot]

My 252 is only about 1/2 gal unusable per side.

[David Lloyd]

The Executive Operators Manual lists the useable fuel at 64 gallons.  The unuseable would be more, see the TCDS quote from pasturepilot.  Unless you have bladders installed, then something different.

In my C, the Operators Manual lists the useable fuel at 52 gallons.  The TCDS shows 3.4 pounds being unuseable.  But with bladders installed, according to the STC paperwork and flight manual supplement, it now has 57.3 total gallons capacity,  54.8 gallons useable, 2.5 gallons unuseable.  When the airplane was reweighed last year, All fuel was completely drained, then 1 1/4 gallons per side were added and then weighed.  Later I ran the engine at idle on the unuseable fuel.  Ran for 10 or so when I noticed the fuel pressure gauge on 0.  I turned the boost pump on and the pressure came back up for about another minute before I shut it down.

[RobertGary1]

It’s just checkride trivia found in the maintenance manual. Nothing a pilot needs to know. Empty weight already includes it. 
you have 64 gal usable until dry. Useless fuel is to collect sediment and won’t be picked up by the fuel system. 

Edited March 10, 2021 by RobertGary1

[David Lloyd]

I got a flight review and IPC from a new instructor a couple months ago.  I think he asked me around 10,000 questions.  Some of which were pretty good, made me think back about 40 years.

[carusoam]

Great question Warren...

There is a real answer that goes with that...

No matter what the book says, or the decals on the instrument panel, or the sticker on the wing... (placards for the MS aficionados...)

The only way to know for sure what the useable fuel is for your plane...

Is to measure it...

There is plenty of that methodology covered for all new owners... often while they are making a calibrated stick...

 

Do it once, get it over with... the data is good for the rest of your plane’s life...

To get a feel for how much unusable  fuel is in there... when the tank is low... get a pic of the fuel pick up screen...

the top of the screen is where the unusable begins... that is the point where air starts entering the fuel line...

Where the unusable fuel ends... find where the fuel sump is... there is about a cup of fuel that can hide below that hole... or water depending on how well you keep your tanks dry...

It becomes a really important piece of information... when you are fighting headwinds...

PP thoughts only, not a mechanic...

Best regards,

-a-

[M20F]

I once put 62.5 gallons in my F after a flight....

[Tcraft938]

20 hours ago, David Lloyd said:

I got a flight review and IPC from a new instructor a couple months ago.  I think he asked me around 10,000 questions.  Some of which were pretty good, made me think back about 40 years.

Maybe he was about to do his instructor checkride and he asked you the 10,000 questions so he could have answers for his ride.  :-)  

[N201MKTurbo]

2 hours ago, M20F said:

I once put 62.5 gallons in my F after a flight....

I’m not sure I’d brag about that...

[M20F]

5 hours ago, N201MKTurbo said:

I’m not sure I’d brag about that...

It was a statement.  

[MikeOH]

9 hours ago, M20F said:

I once put 62.5 gallons in my F after a flight....

I plan never to make such a statement.

[M20F]

1 hour ago, MikeOH said:

I plan never to make such a statement.

The internet and aviation are filled with people who all have a plan till they get punched in the mouth.  
 

PS The original post is a typo, should read 64.5 gallons.  

[Andy95W]

4 hours ago, MikeOH said:

I plan never to make such a statement.

 

2 hours ago, M20F said:

The internet and aviation are filled with people who all have a plan till they get punched in the mouth.  
 

Exactly.

30 years and a whole bunch of hours ago I put 39.4 gallons into a C-172 that held 40 gallons total.  After a night flight.  Because I was stupid enough to listen to a guy just because he was a King Air pilot.

We live, we learn.  If we’re lucky, we survive our mistakes so that we don’t repeat them.  

[ncav8tor]

On 3/11/2021 at 11:28 AM, M20F said:

I once put 62.5 gallons in my F after a flight....

You got robbed Brother! That pump meter was off a bit  

 

LMAO, just kiddin with ya!

[cliffy]

Unuseable fuel and its moment are included in 
empty Weight and CG.

On the other hand-

Any CAR-3 airplane does NOT include the weight of the engine oil in the empty weight of the airplane so the weight of the oil in the engine comes off of your useful load.

On Pt 23 airplane FULL engine oil is figured in to the Empty Weight calculations.