How to measure fuel for gauge calibration?

[kcameron]

My RV-4's refit is rounding the bend to completion. I can barely see the light at the end of the tunnel. One of the remaining tasks is to calibrate the AF-3400 fuel level indicators. To do that, I'll need to accurately add 1 or 2 gallons at a time to each tank. I don't know the best way to measure the fuel though. I'm sure someone here has a good method.

Thanks in advance.

[Tomasz]

Originally Posted by kcameron

My RV-4's refit is rounding the bend to completion. I can barely see the light at the end of the tunnel. One of the remaining tasks is to calibrate the AF-3400 fuel level indicators. To do that, I'll need to accurately add 1 or 2 gallons at a time to each tank. I don't know the best way to measure the fuel though. I'm sure someone here has a good method.

Thanks in advance.

milk bottles?

[rvbuilder2002]

Originally Posted by kcameron

My RV-4's refit is rounding the bend to completion. I can barely see the light at the end of the tunnel. One of the remaining tasks is to calibrate the AF-3400 fuel level indicators. To do that, I'll need to accurately add 1 or 2 gallons at a time to each tank. I don't know the best way to measure the fuel though. I'm sure someone here has a good method.

Thanks in advance.

One way is to get a 5 gal gas jug that is translucent enough to see the fuel level through it (not all of them are).
Set the jug on an accurate scale.
Add 6 pounds of fuel (it's actually 6.02 pounds per gal at 15 deg C. but 6 pounds is close enough).
Use a marker to mark the fuel level on the jug.
Add another gallon and mark, if you are using 2 gal increments.
You now have a measuring jug.
Or you could pull the airplane to a fuel pump (the pump meters are generally quite accurate) or you could make the above jug and test the value of teh pump meter

[az_gila]

Originally Posted by kcameron

My RV-4's refit is rounding the bend to completion. I can barely see the light at the end of the tunnel. One of the remaining tasks is to calibrate the AF-3400 fuel level indicators. To do that, I'll need to accurately add 1 or 2 gallons at a time to each tank. I don't know the best way to measure the fuel though. I'm sure someone here has a good method.

Thanks in advance.

Easy... just put in 2 gallons at a time at wherever you buy 100LL.

They will have had your local county/state Weights and Measures folks calibrate it regularly.

If you can read the dial to the nearest 1/10 gallon, and you burn around 8 gallons per hour when you fly - that will give you an accuracy of better than 30 seconds flying time - certainly good enough for the job... .... and probably much better than the rest of the system.

[Mel]

I buy my oil in 5 qt. jugs. They are marked in 1 qt. segments. I used these to pour 2 gals. at a time into 5 gal. jugs.
Worked for me.

[ao.frog]

I did this a few weeks ago and Rob at AFS recommended 6 calibration points.
I had planned on 11 points, but he said that was way too many and recommended 6 points: 0, 15, 30, 40, 60 and 80 litres. (we use litres in Norway)

I started with empty tanks and had the fueltruck fill the amounts, one after another, calibrating the gages one step at the time.
I've a TD, so I did "lifting thing" on each filling to.
(I'm sure you've seen the description how to do it in the manual)

I elected to trust the airport fuel truck gages since they calibrate their gages regurarly.

The gauges on my -7 seems to work very well.

PS: so far AFS has given me SUPERB customer support! They're really helpful and nice to work with!

[N941WR]

I used two milk jugs, which I calibrated at home with water and a messuring cup. Once I had them filled with exactly a gallon I marked the level line with a sharpie.

At the airport I would fill both with 100 LL, pore it in the tank and hit the button on the Dynon. I had to repeate this nine times for each tank.

Go to a boating store and purchase a funnel with a micro screen in the bottom. That way you can drain your tanks and strain out all the junk (pro-seal, aluminum shavings, etc.) before your first engine start.

Good luck and be careful, remember 100 LL has been known to catch fire when fueling aircraft tanks. Keep a fire extinguisher close by.

One other thing, if you are going to purchase five gallon gas cans to hold your fuel while doing this, buy the kind with a vent plug. I have four cans, two with this plug and two Blitz can's that vent through the pour spout. These do not work well and aren't worth the plastic they are made out of.

[robertcs]

Unless I missed it I didn't see any mention of the airplane's attitude in all of this. I haven't looked at it closely to this point, is it not an issue?

[rvbuilder2002]

Originally Posted by robertcs

Unless I missed it I didn't see any mention of the airplane's attitude in all of this. I haven't looked at it closely to this point, is it not an issue?

It definitely is for a taildragger, it causes a slight error on tri gear depending on the model. For example, an RV-6A has a lot more positive angle of attack on the ground than an RV-7A or 9A.

If you want absolute accuracy in flight you need to calibrate in level attitude.
One thing good to know is if you calibrate in level flight attitude, the gages read a higher than actual value when sitting on the ground (amount varies with model).

[kcameron]

The advantage of using the fuel truck is that it eliminates cumulative errors. That is if I can get the truck to stick around for the whole procedure. Probably not a problem on a week day.

Thanks guys.