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Defueling a Tank

GigAir

Active Member
While calibrating my fuel tanks, my EFIS shut down unexpectedly, after I had filled one tank with 22 of the 25 gallons. All data was lost, and I am faced with de-fueling a near full tank, to start the fuel calibration over. Any advice or techniques regarding the safest way to drain a fuel tank would be highly appreciated! I know this has been done before many times.....just not by me.

Greg Novotny:D
RV-14a N14ZP
KTIW
140209
Dues gladly paid
 
Provided you aren't in a rush... (and you shouldn't be)

Assuming you have gas cans ready, some safety wire and a nut... Wrap safety wire around the fuel drain and run into bottom of whatever gas can (through funnel is applicable) with a nut tied on the end. This should reduce the potential between aircraft and can.

Well ventilated area...no fans running etc etc.

Take your time, don't don't leave aircraft when defueling.
 
Went through this exercise myself about 2 weeks ago and had the same problem with the efis shutting down on me while on my last 2 gallon pour. In my case I have a capacitive sender and knew ahead of time I would have to drain the tanks once so I was prepared (cal the sender, empty, then cal the efis).

Anyway, I got some 1/8 NPT ball valves and installed them in place of the little sump valve, got a bunch of 5 gallon gas cans and drained the tank. When my efis went dark, the normal sump valve was already installed because I didn't expect I'd need to drain the tank a second time. Anyway, I got the ball valve ready and removed the sump valve and quickly put in the ball valve. Some fuel sprayed out but not very much. Just be quick about it, be sure there's nothing nearby that can ignite the fuel and have some paper towel around to clean the fuel of your hands and arms.

Picture here:
http://airplane.athomeinthewilburness.com/2017/06/30/engine-start-and-other-stuff/
 
Caution

Don't do this in dry conditions or in a hangar. Many aircraft have burned up due to static electricity spontaneously igniting. Ground your plane to a tie down or hangar rail.the metal cans also. Have large fire extinguishers handy and a helper.
 
Greg,

Assuming everything is grounded as stated above, don't forget you are also a static electricity generator. Ground yourself to the airframe by touching it before touching the fuel can.

I always get the willy's when it comes to transferring fuel.

Since I dumped FB I've missed your progress reports on the -14. Post a pic when you can.
 
Just did this to get to empty tanks for a full calibration.

Lowes sells a siphon/hand pump which worked well to get most of the tank emptied into 5 gallon fuel containers.

Drain the rest - probably only 2-3 gallons - by simply removing the tank quick drain with a funnel and gas container under the wing.

Put a paint filter cone in the funnel to catch the quick drain plug and also to see if there was any sediment/debris in your tanks.

Ask around your local airport, I'm sure you can find a bunch of 5 gallon containers around that have been used for 100LL. Typically plane tanks are drained before being put on the scales for a W&B.

As stated previously - ground everything, only use approved fuel containers and work outdoors with a fire extinguisher handy.
 
Drain fuel

5 gallon Homer Buckets from Home Depot , if you go to the paint dept they also have a calibrated gallon pail
 
I have a metal storage for filling up my planes when the airport fuel is closed. It has a ground wire on it for filling. I grounded the tank as per usual and removed the fuel line from the fuel flow meter (red cube) and added a length of fuel line I have and put the end into my tank. I made sure the fuel tanks were absolutely clean before adding fuel in the first place. Then with everything grounded I just turned on the boost pump until the tank was empty.
 
Connect a 20' long hose with approprate fittings to the fuel line that feeds your carb or injector servo. Put a ball valve on the other end of the line.

Use your aircraft fuel pump to transfer fuel from either tank to a portable gas can or other wing.

Easy, minimal spillage and uses electrons for their intended purpose. Also, filters the fuel.
 
Connect a 20' long hose with approprate fittings to the fuel line that feeds your carb or injector servo. Put a ball valve on the other end of the line.

Use your aircraft fuel pump to transfer fuel from either tank to a portable gas can or other wing.

Easy, minimal spillage and uses electrons for their intended purpose. Also, filters the fuel.

While you do this, measure the fuel flow to verify it exceeds that required by the engine.

Carl
 
Curtis drain valve.

We keep the Curtis type drain valve for just this reason. The one with the pin-lug that can be looked open. We just stick a peace of clear plastic tubing over it " I think it is 3/8" " and open the valve and let it run tell the can is full. Snap the valve closed change cans and go again. I like to just start off with 25 gallons of Mo-gas, do the work, then drain it back out and put it in my pick-up truck. Hope this helps, Yours, R.E.A. III #80888
 
I'm glad these guys chimed in before I described how I did this a couple weeks ago. I missed a couple safety steps.

Reason I did this was that my fuel sump kept getting stuck in the up/on position. The culprit was the end of a drilled off rivet getting stuck in the sump. I was also getting occasional drips after sumping from both tanks. I took the opportunity to change out the O-rings on both tank sumps. I was surprised at how the original o-rings had shrunk to almost useless. New o-rings and good to go.

As stated before, running a fuel flow test after the pump/red cube and calculating/verifying fuel going to the carb is a good verification of not only fuel flow but also any leaks in the system. My DAR required this test prior to his inspection and by golly I discovered a leaky connection in doing so. The fuel would sort of sputter out of the hose on one tank but a solid stream off the other. Some troubleshooting and discovered the culprit.

The fuel system / sealing in its entirety was definitely one of the better learning aspects of the build.
 
.....

Reason I did this was that my fuel sump kept getting stuck in the up/on position. The culprit was the end of a drilled off rivet getting stuck in the sump. I was also getting occasional drips after sumping from both tanks. I took the opportunity to change out the O-rings on both tank sumps.
.....

Again, why I liked removing the sump drain entirely to get the stuff out that you can't siphon.

In my mind, a flush of each tank after a fill or two is a good idea. :)
 
Tube

Make a guide tube/drain for a curtis push-type quick drain.

Take a 1/2 pipe about 18 inches long, drill a hole in the side near the top, insert a few inches of stiff bailing wire or hinge pin so it pokes up thru the center of the pipe, hose clamp and RTV/JB Weld the wire in place. Stick the pipe in a gas can, place under the wing, push the pipe around the drain valve so that the wire pushes the quick drain and put a vise-grip on the pipe at the gas can hole to keep it going. This setup keeps the fuel sorta-contained, more or less, and is easy to turn on/off. Also does not require tampering with anything on the fuel system.

Caution caution caution! Gas is dangerous!
 
Another good way, assuming you're already airworthy, is to just go fly until the fuel is down near zero in that one tank. Your last landing will require some aileron to keep wings-level but you'll only need to drain a gallon or two when you're done.

Just did this before fixing weeping leaks at the sender covers on my fuel tanks, so I know it works... :) Fixed one side and then the other and only needed to drain 3-4L from each tank.
 
Again, why I liked removing the sump drain entirely to get the stuff out that you can't siphon.

In my mind, a flush of each tank after a fill or two is a good idea. :)

Agreed. Pulling the sump plug allowed me to flush out the system, including a drilled off rivet head that I otherwise would not have found and would have continued to be problematic down the road.

I flew until I had perhaps 6 gallons in one tank and 10 in the other, low enough that i could manage draining the fuel into a couple 5 gallon cans. Stuck a socket on the plug and pulled it out, drained into the cans.
 
Just had to defuel also last week in order to deal with leaks. So once you have all this fuel out into 5-gallon cans... what do you use to refuel in one gallon increments to recalibrate?
 
Yep, defueling sucks! A coupla months the ago we had to change the electric boost pump on a T-28A, which means you gotta drain the tanks. We had 140 gallons on board... ugh; not a fun time.
 
Just had to defuel also last week in order to deal with leaks. So once you have all this fuel out into 5-gallon cans... what do you use to refuel in one gallon increments to recalibrate?
The gas pump. Save the 5 gallon can until you've flown off 5 gallons worth after you've calibrated.
 
Just had to defuel also last week in order to deal with leaks. So once you have all this fuel out into 5-gallon cans... what do you use to refuel in one gallon increments to recalibrate?

I poured from the 5 gallon cans into a calibrated 2 gallon can (I had to do 2 gallon pours) then from the 2 gallon into the tank.
 
That was my hope to do also. I'm just drawing a bit of a blank on where to source a calibrated 1 or 2 gallon can. Googling around at the moment.
 
That was my hope to do also. I'm just drawing a bit of a blank on where to source a calibrated 1 or 2 gallon can. Googling around at the moment.

I went to Tractor Supply and bought a 2 gallon can (which has a 2 gallon 8 ounce mark on it). Then I calibrated it to 2 gallons with a nice black mark around the outside. I calibrated by weight. 1 gallon of AVGAS weighs 6.01 lbs.
 
That was my hope to do also. I'm just drawing a bit of a blank on where to source a calibrated 1 or 2 gallon can. Googling around at the moment.

Don't rely on the markings on a 2 gallon red plastic fuel container from the auto parts store.

I did my initial, partial calibration that way and found the molded in marking was about 10% off.
 
Gil - exactly my fear. I /know/ those markings aren't right.

Joe - Thanks for the idea about calibration by weight. That sounds more probable for me to do. And yes, I'll zero-out the weight of the can itself beforehand. ;)

Rob - Heh. That might be a while when you have a full 36 gallons sitting around in cans and you're still a few months away from first flight. Might as well just sell it off to the others on the field and hope the FBO doesn't notice. :D

Thanks for letting me hijack the thread!
 
5 gallon Homer Buckets from Home Depot , if you go to the paint dept they also have a calibrated gallon pail

NO!!! Not only is that large opening inviting trouble of all kinds, but some plastic does not tolerate gasoline. Don't count on the cheap 'pickle-bucket' cans being consistent. The five-gallon jerry cans specifically manufactured for fuel are not prohibitively expensive, and the plastic ones are pretty safe to use. I got four red ones for my avgas and labelled them 100LL, plus two blue diesel cans for the Jet-A that goes in my kerosene shop heater. 10 years and no leaky cans or other problems.
 
From the movie Die Hard with a Vengeance:

"Next to the brief case you will find a 3 gallon jug and a 5 gallon jug. Fill the 5 gallon jug with EXACTLY 4 gallons of water and place it on the scale. if you fail the bomb will go off. You have 5 minutes to comply...."

Sorry guys, I just couldn't resist a little humor around this seriously very important and informative topic! Do it safely and have a great day! :D
 
The Holy Gas Can of Airportdom?

"Three shall be the number thou shalt count, and the number of the counting shall be three. Four shalt thou not count, neither count thou two, excepting that thou then proceed to three. Five is right out."
 
Fuel drain

NO!!! Not only is that large opening inviting trouble of all kinds, but some plastic does not tolerate gasoline. Don't count on the cheap 'pickle-bucket' cans being consistent. The five-gallon jerry cans specifically manufactured for fuel are not prohibitively expensive, and the plastic ones are pretty safe to use. I got four red ones for my avgas and labelled them 100LL, plus two blue diesel cans for the Jet-A that goes in my kerosene shop heater. 10 years and no leaky cans or other problems.

Yes , HDPE , look it up , same plastic used in Fuel Tanks .
 
I think I opened a can of worms. Wow, what a great range of inputs, all sincerely informative and appreciated. Thank you for sharing....for the next round of guys faced with a similar dilemma.

Greg Novotny:D
Airworthiness Certificate Awarded TODAY 7/13/17
RV-14a N14ZP
KTIW
Gig Harbor, WA
 
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