Total vs Usable Fuel 1966 M20E

[Matthew P]

Sorry to trouble you, searched POH, AFM and MAPA references and only see reference for 52 gallon total fuel, don't see anywhere that lists usable fuel, checked a few comments online and have heard everything from 48 gal usable to 52 gal usable, but no reference for 48 gal and the absence of usable reference to state that all 52 gal is usable.

Doesn't really matter in that I NEVER go 6 gallons in either tank, just curious

What an I missing?

 

TIA

[PT20J]

Check the TCDS

[Hank]

@Matthew P, your E and my C both have a total of 3.4 lb = 0.567 gallons of unusable fuel. At a weight of 6 pounds per gallon, this comes to 36 ounces per wing.

I flight plan for 50 gallons, because it makes the math easier. I also leave ~1/2" of expansion room when filling up, since it gets hot here in the South and I hate to see fuel dripping out the overflow . . .

[AJ88V]

If I read what @PT20J posted correctly, there is a Fuel Capacity of 52 gallons  (USABLE fuel), plus a small amount of unusable fuel “(not included in the fuel capacity)” as specified per model. 

So, 52 gallons is usable.

(Didn’t remember that! Thanks @Matthew P for asking and @PT20J for answering!)

[TheAv8r]

Yeah, I've interpreted it the same way, there's 52gal of usable total fuel, and then an additional 0.5-ish gal of unusable (I have a '65 E with bladders).

[PT20J]

35 minutes ago, TheAv8r said:

Yeah, I've interpreted it the same way, there's 52gal of usable total fuel, and then an additional 0.5-ish gal of unusable (I have a '65 E with bladders).

That’s correct. For the M20J for instance, the TCDS states 64 gal and the POH states 66.5 total, 64 usable. 

[bcg]

The best way to KNOW what you have usable is to fly a wing dry and see how much you can put back in it. I can put 24.7 per side in my plane, the book says 24.4 per side. I'm sure they all vary slightly. Is it enough that it really matters if you're being smart with reserves? No but, I still like to know for sure.

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[Hank]

7 hours ago, bcg said:

The best way to KNOW what you have usable is to fly a wing dry and see how much you can put back in it. I can put 24.7 per side in my plane, the book says 24.4 per side. I'm sure they all vary slightly. Is it enough that it really matters if you're being smart with reserves? No but, I still like to know for sure.

When my tanks were resealed, both were full to the caps and the bill was for 52.4 gallons.

Close enough to 26 per side for me, I still plan for 2:30 per side with knowledge that there's actually a bit more. But I don't like going much over 4 hours, but sometimes head winds and reroutes happen . . .

So far, two flights at 4:45 landed with 11-12 gallons left in one tank, good for 1:15-1:20 more.

[TheAv8r]

On 12/18/2024 at 12:08 PM, bcg said:

The best way to KNOW what you have usable is to fly a wing dry and see how much you can put back in it. I can put 24.7 per side in my plane, the book says 24.4 per side. I'm sure they all vary slightly. Is it enough that it really matters if you're being smart with reserves? No but, I still like to know for sure.

Sent from my Pixel 9 Pro XL using Tapatalk
 

Also strongly advocate for CIES senders properly calibrated. My CIES senders are incredibly accurate, to 1/10th of a gallon, so at all times I know exactly how much fuel is in my airplane. I never fly with less than an hour reserve, but it has brought so much peace of mind when trying to make decisions on fuel planning.