Drain fuel tanks for w/b...how to do?

[MacCool]

Maybe it's as simple as it sounds, but....maybe not. I'm new at this.

New EFIS, and the fuel tank calibration is TU. The constant "check fuel" warnings are annoying. I need to re-calibrate the tanks, looks like in two-gallon increments. Additionally, I want empty tanks so I can get a new weight/balance. AND...two of my three Saf-Air Cav 110 drains have the drips and got minor squawks from my AP/IA on my recent CI.

My plan....fly the tanks as empty as I dare, then remove the gascolator drain and empty the tanks into a couple of 5-gallon cans. Do the w/b, install new Saf-Air drains, then refill the tanks two gallons at a time each and re-calibrate.

Tips? Tricks? I want to be efficient, but mostly don't want to screw this up.

 

[blaplante]

yup

Yeah, that's pretty much the drill. Only thing I can add is connect a jumper from your fuel can to the airplane before draining. Talk about a place you don't want a spark...
Only difference - I'd pull the tank drain instead of the gascolator drain.

 

[rocketman1988]

Drain

I calibrated my EFIS 3 times. I just removed the CAV110 and let them drain into a large funnel in a gas can. You will be surprised how fast the tanks will drain...

 

[Carl Froehlich]

Take the cowl off. Disconnect the fuel line at the firewall and connect a short piece of 3/8” aluminum tubing, flared for the AN fitting. Connect a 3/8” ID tygon hose to the aluminum tube, then a cheap clear plastic (Walmart) in line fuel filter to 5 gal jugs. Use your boost pump to pump the tanks dry.

Carl

 

[BobTurner]

+1 on the previous posts. Also, although the fuel drains are not too expensive, you may find that a simple O ring is all they need.
When adding 2 gal at a time, rap on the inboard rib a few times before each measurement, to make sure the float isn’t stuck. (In flight, engine vibration seems to be enough to keep them free).

 

[BillL]

Surprised no one used a valve. I wanted to calibrate both tanks with the same fuel so metered out from one and poured into the other. A nipple and valve with some hose facilitated that.

I chased a different height vs gallons for the tanks, and it drove me crazy. Then found that it was due to tilt as the wing got heavy. Jacks to level the wings and keep them there would be perfect.

 

[MacCool]

Yeah, that's pretty much the drill. Only thing I can add is connect a jumper from your fuel can to the airplane before draining. Talk about a place you don't want a spark...
Only difference - I'd pull the tank drain instead of the gascolator drain.

Great tips...thank you all.

The ground wire is smart for sure. I would have grounded the plane, but in this context it does make more sense to wire the plastic gas cans to the plane. I want to zero the potential between tank and gas can, not plane and ground.

As to the gascolator....I admit that I'm not clear on the way my RV-9A is fuel-plumbed (if anyone has the plans diagram, I'd appreciate a link). I was assuming that draining through the gascolator would make the most sense since it's the lowest point in the fuel system, but I have to pull the wing drains anyway (leaking). I realize that I can just replace the O-rings but I already bought some new CAV110's so...

As to disconnecting and draining from the main fuel line....great idea! Let my new $1000 fuel pump do some of the work...

 

[Kyle Boatright]

Whatever you do, do it outside, not in a hangar.

 

[Vern]

Caution

A new RV-7 burned up in my hangar because a little fuel spill and low humidity sparked just right

Take it outside

No dry days which produce static

Ground wires everywhere

Multiple fire bottles and a helper

 

[wcalvert]

Your Fire Marshall will go bananas if he sees you doing the draining into PLASTIC fuel tanks.

They're almost impossible to ground properly and collect a lot of static charge from moving fluids.

If you can find metal cans, all the better!

 

[00Dan]

I used a set of jumper cables when I had to drain my tanks. One cable from a metal hangar post to the airframe, then another from the airframe to my gas can.

 

[bill.hutchison]

Take the cowl off. Disconnect the fuel line at the firewall and connect a short piece of 3/8” aluminum tubing, flared for the AN fitting. Connect a 3/8” ID tygon hose to the aluminum tube, then a cheap clear plastic (Walmart) in line fuel filter to 5 gal jugs. Use your boost pump to pump the tanks dry.

Carl

I followed this somewhat - I removed the sump valve from the bottom of the gascolator and fitted a 1/8" pipe nipple to the bottom with some tubing going in to the gas can. Hooked up power to the airplane and pumped out the fuel with the fuel pump.

I'm likely going to have to replace one of my fuel senders (weird readings on the volt meter and nothing like the "more correct" other one. So not looking forward to that....)