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MIR2018

What's really in there, Fuel-wise?

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    I was shopping for a fuel measuring-stick for my recently acquired '65 C model but realized that there is a point where the fuel is actually much out of sight and I can see the bottom of the tank (bladders installed).  IIRC my the fuel gauge read 1/4 (not positive about that).  Am I missing something here? I've always flown Cessna aircraft so I've never run into this before. It left me wondering how useful a dipstick would be.  Is this a low-wing thing, or a Mooney thing? Or am I nuts? :wacko:

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Yes, a fuel measuring stick is very useful for your M20C. The best fuel stick will be one you make yourself. A wooden dowel, a paint stirrer, or similar that you mark yourself will be the most useful. The max fuel you can have in the tank without reaching it with a fuel stick, is only about 8 gal. And that is probably not enough to consider for take-off purposes. In other words, if there's not enough fuel in the tank to measure with your stick, there's not enough fuel to go fly.

From here it gets more high tech, more accurate, and more expensive. Get an engine monitor with proper fuel flow and (primary) digital fuel gauges. Pair that with CiES digital fuel senders. Now you'll know how much AND where it is at all times. Typically accurate to within 1/2 gallon on each side.

The more accurate your fuel information, the more range you have, the safer you are, and the more peace of mind you enjoy.

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4 hours ago, MIR2018 said:

    I was shopping for a fuel measuring-stick for my recently acquired '65 C model but realized that there is a point where the fuel is actually much out of sight and I can see the bottom of the tank (bladders installed).  IIRC my the fuel gauge read 1/4 (not positive about that).  Am I missing something here? I've always flown Cessna aircraft so I've never run into this before. It left me wondering how useful a dipstick would be.  Is this a low-wing thing, or a Mooney thing? Or am I nuts? :wacko:

On a C model with the 54.8 gallon bladders, when you can just see the bottom of the bladder, you have about 6 gallons left.  I rarely run a tank down past that point, so the stick is very useful.  Somewhere on here there's a post with the measurements from someone with an F that had 54 gallon bladders.  The mark distances from them on a wood paint stirrer have worked very well for me.   Here's a regression analysis from their 5 data paints that gave me several more distances to mark on the stick.  My marks slightly underestimate the amount of fuel on purpose.  

 

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I think my Owners Manual says to select a tank with more than 6 gallons when landing. As you learn your plane, you will eventually want / need the extra range, so run one tank out or close to it, saving fuel in the other to land. This will probably be on a flight where you took off without filling up; with me, no fuel at home, neither I nor the nice guy in charge at my planned stop could make the fuel pump dispense fuel (but it turned on), but I had enough to complete the trip (and several possible stops enroute), landing with 1:15 left per my fillup. I switched tanks at top of descent. Almost everything was in the last tank (couldn't see anything in the one).

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I would consider a tank that has no fuel visible in it to be empty for endurance planning purposes and 10 gallons for WnB. 

Here's how I manage my fuel reserves, starting with how I did it in my M20F prior to the engine monitor. 

Always look in your tanks. Even if you stop for lunch and come back out, look in your tanks. People steal fuel, sump points sometimes stick, line guys fill you to the tab instead of the rim, they fuel the wrong plane, et cetera. A member here didn't place any fuel order and came back to his plane filled with Jet-A; had he not checked, it could've killed him. 

My M20F holds 32 gallons on each side. For long trips, I would start off on one tank, climb out on it and switch after three hours or when the engine stopped (if I run a tank dry, it would usually tank about 34 gallons). That, to me, guaranteed that I had at least 3 hours remaining since you burn more on the climb and I didn't include what I burned on the ground. I wouldn't even notice the imbalance. Some pilots like to switch every so many minutes. I don't like this approach as if things got down to the wire and I were into my reserves, I would not want them split between tanks with uncertainty. I also regard switching tanks as having an increased risk factor. I read an account of a vintage Mooney owner who had the selector handle come off in his hand while turning it. Fortunately he was able to access a pair of vice grips from his toolbag to successfully switch tanks. 

After getting my engine monitor and being certain of its accuracy, I started burning 16 gallons off of one tank, switching tanks, and not switching back until either I burned off 32 gallons or was less than around 12 gallons calculated remaining on that side and coming in to land. 

I do not trust panel mounted fuel gauges, though the wing-mounted gauges are excellent to ensure you have fuel in your tanks if the needles are bouncing. 

I have not yet developed a full methodology for managing fuel in the rocket. Fueling is much more complicated with the long range tanks and flappers on the inboard tanks and I don't yet have it down to any sort of science so I carry more fuel than I need for my trips. 

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I used the measurements that Dan posted at 

 

They are perfect for my 26 gal tanks in my 65 M20C.  

If the link above doesn't work use Google and search for  "site:mooneyspace.com homemade fuel stick"  then go down halfway to the reply by Dan M20E '66.  

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