Taildragger Fuel Level - Visual indication.

This applies more to the -7 than the 7A, but I've noticed that when on the ground, the fuel level indicators on the EFIS are more or less useless: Parked, they both read full unless I've got less than 10 gallons. In flight they're fine.

I understand fully that I should be able to keep track of my fuel by various means, such as basic arithmetic using time, flow rate, etc. But this doesn't really help on the ground before the first flight of the day. Any number of things could happen between the time you walk away from the aircraft and the next time you fly it, up to and including a bunch of teenagers siphoning out your avgas to put in their jalopy (does that sound dated or what?).

So the obvious answer would be like everyone is taught on day 1 of flight instruction in a Cherokee or Skyhawk: Check the fuel visually, by looking in the fill hole or with a dip tube.

Doing this in the RV is easy enough, with its low-wing configuration, and I can't be the first person to have this question, so does anybody have a set of photos looking inside the tank at various fuel levels with gallons-remaining numbers attached?

Maybe just some rough indications of what I should be looking for in there at 5, 10, and 15 gallons? Full is fairly obvious, but the ground attitude and dihedral throws off my guesstimates for the remaining graduations quite a bit.

Thanks!

I used a paint stirring stick, Painted it flat black and from empty put in 5 gallons at a time and marked the stick. Use it all the time. I think many of us use a stick of some sort. Larry

Larry,

How much fuel did you add before it got up to the stick?

I did exactly what you describe, but I do not trust my eyeball for something his critical.

I emptied one tank with the tail down and calibrated a dipstick by adding 5 gallons at a time. You could also use smaller increments for more precision. The size increments on the stick vary considerably as the tank is filled.

I had previously calibrated the Dynon fuel gauges by levelling the aircraft and adding 2 gallons at a time. Because of the dihedral it only shows > 14 gallons when the tanks are above this level.

The fuel gages in my RV-6 work great. They indicate full when the tanks are full and they indicate empty when empty. Those are the only two places where youy could reasonably say that the tank and the gage agree, in flight or not. It's not exactly what I'm used to to be sure, I miss having a totalizer reading down to the pound that I can depend on.

So yes, I made a dipstick. I ran a tank dry to verify empty indication/usable fuel, then filled two gallons at a time, carefully measuring as I went. I transcribed those measurements onto an Aviation Approved Stick (AAS). Fuel is on the stick at 4 gallons. I've also installed a red cube and Flight Data Systems FC-10 fuel computer. It's not a quantity indication, but it is a very accurate measure of fuel consumed so I just need to know where I've started and I have to pay attention to tank switching to manage fuel levels. Starting out full is easy and the the AAS gives me good numbers to compare to the FC-10 when less than full. I would love to have a reasonably accurate in flight quantity indication in flight, maybe I'll upgrade someday.

Doug

My eyeball test is that if the airplane is on a level surface, the "water line" on the fuel is roughly below the fuel filler neck when the tank has 4-5 gallons.

Brantel said:

Larry,

How much fuel did you add before it got up to the stick?

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5 Gal will show at the very bottom of the stick. Larry

LARCO said:

I used a paint stirring stick, Painted it flat black and from empty put in 5 gallons at a time and marked the stick. Use it all the time. I think many of us use a stick of some sort. Larry

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NOTE: I have a -6.... -7 may be different.

Same as Larry here. Didn't paint the stick. I added 5/10 gallons and marked same. I put the paint stick in as vertical as I can.

For reference, when I have 5 gallons the level is at the bottom of the lower stiffener.

We use a dipstick - as we share the airplane, we always leave it to a mark which represents sufficient fuel to allow two of us to get airborne and then do aeros at the allowed weight.

If we want to go somewhere, we fill before departing.

Always allows at least 90 mins flying.

My 2c

I too made a dipstick out of wood with a wooden handle on the "dry" end so that it can´t fall into the tank. I filled the tank from empty and measured the wet part on the dipstick every two gallons. I lean the dipstick on the most rear end of the filler opening and vertical. Here is the table which came out. Convert cm to inch and you should have a reasonable indication of the fuel in your tanks. There might be a slight difference with other tail forks or wheels.
Below about 5 gallons the fuel level doesn´t reach the tank bottom below the filler opening as you can see on the table, so this too is good to know.

My gauges also read funny from time to time, depending on temperature, ground flatness, etc. However, the totalizer provided by my red cube has been 100% accurate in telling me exactly what i've burned. If I need to know exactly what's left on board, I check it.

[edit]I also have a dip-stick that I use on the ground... Just in case anyone thinks I don't dip the tanks before flight, and just look at the totalizer.

I also have the Red Cube installed and know exactly what I have burned and when refueling I can calculate how much fuel will go in - maximum difference about a quarter Gallon. However the simple dipstick has still it?s place because you don?t know if you have lost fuel somehow - stolen, fuel leak or whatever. So the dipstick at least gives you an estimate of fuel on board. Also I don?t want to miss the old "unaccurate" fuel level senders, because with them you can crosscheck the fuel level in flight. A fuel leak will show as a difference between the fuel quantity indication and the Red Cube values (fuel used or onboard).

Clear Plastic

I use the clear plastic stick that you place your thumb over. It is marked 0-14 and I always stick it in the bottom outboard corner to be consistent. The numbers are roughly 8 gals less than the total. In other words, it reads 10 when the 18 gal tanks are full and 2 when I have 10 gals left.

SuperCubDriver said:

I too made a dipstick out of wood with a wooden handle on the "dry" end so that it can?t fall into the tank. I filled the tank from empty and measured the wet part on the dipstick every two gallons. I lean the dipstick on the most rear end of the filler opening and vertical. Here is the table which came out. Convert cm to inch and you should have a reasonable indication of the fuel in your tanks. There might be a slight difference with other tail forks or wheels.
Below about 5 gallons the fuel level doesn?t reach the tank bottom below the filler opening as you can see on the table, so this too is good to know.

Click to expand...

Would it be possible for a picture of the stick you made and also a picture of the stick inserted into the fuel filler opening(ie: Showing how you use it). Thank you in advance!!