Fuel tab quantity

[m100psi]

Probably an easy one:  For Mooneys with 32 gallon tanks and 25G tabs, is the 25G usable mark at the bottom of the tab, or the drill hole that’s about 3/4” above it? Not trying to make my destination on the difference, but would be good to know. 
 

Thanks,

Matt

[201Mooniac]

I always thought it was the drilled hole but I've never seen it documented.

[N201MKTurbo]

I always thought it was the bottom edge of the tab. I have found if you fill it till you get to the hole, it will be at the bottom of the tab after it settles down after you shut the pump off.

[carusoam]

Expect to find the drilled hole means something…

Probably mentioned in the POH… possibly in three different places…  from limitations, to refueling…

By the time Mooney was using the drilled hole method… their construction techniques were very stable…. Few variations go on inside the fuel tanks…

 

Like any fuel tanks… the only way to know your useable fuel is to actually fill it and use it all….

So… while filling it make notes on how many gallons you put in, to the bottom edge of the fuel neck, how many more to to the calibrated hole, then finally filled to the top in contact with the wing skin…

There are so many variations that can occur after the plane leaves the factory… like simple blocked vent holes in the ribs… top and bottom…

PP thoughts, not a mechanic…

Best regards,

-a-

[Ragsf15e]

7 hours ago, m100psi said:

Probably an easy one:  For Mooneys with 32 gallon tanks and 25G tabs, is the 25G usable mark at the bottom of the tab, or the drill hole that’s about 3/4” above it? Not trying to make my destination on the difference, but would be good to know. 
 

Thanks,

Matt

I swear mine has “25gal” written on the tab with an arrow pointing at the bottom of the tab, below the hole.  Anecdotally, I use the tabs a lot and find that it’s very very close to 25 gallons at that point.  I have a pretty accurate setup that I’ve checked.

[m100psi]

Looks like it does have the arrow pointing to the bottom of the tab.  Good to hear it matches well with measurement. Thanks all for the feedback.