Hello, Just wondering how you guys drain the fuel tank. Just finished the 25 hour inspection a few weeks ago and now we are getting prepared to pull the landing gear off for the s.b. Used the electric pump last time, and still got fuel all over me when I took the lines loose. Any good ideas.
Van's Air Force
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Draining the Gas Tank
- Thread starter lewy
- Start date
engineerofsorts
Well Known Member
My "theoretical" approach
I have to pull the tank for the first time after having gas in it. I figure I can empty it down to a fraction of a gallon using the fuel flow test technique of pumping it out of the gascolator output. After that, I'm "hoping" that I can push the tail down and put the nosegear into an elevated dolly (that I used to get the vertical stab down below the height of my garage door when it made its escape to the real hangar). If that tilts the back of the gas tank down sufficiently get get the remaining gas through the baffles and into the back of the tank, I can then disconnect the line on the bottom of the tank and plug it with the cap used for tank testing, without getting appreciable amounts of gasoline in my face. Still a theory--has anyone else got a better/really tested approach?
I have to pull the tank for the first time after having gas in it. I figure I can empty it down to a fraction of a gallon using the fuel flow test technique of pumping it out of the gascolator output. After that, I'm "hoping" that I can push the tail down and put the nosegear into an elevated dolly (that I used to get the vertical stab down below the height of my garage door when it made its escape to the real hangar). If that tilts the back of the gas tank down sufficiently get get the remaining gas through the baffles and into the back of the tank, I can then disconnect the line on the bottom of the tank and plug it with the cap used for tank testing, without getting appreciable amounts of gasoline in my face. Still a theory--has anyone else got a better/really tested approach?
Remember that when building the fuel tank the pickup is in an place where there are baffles with kind of small holes to let fuel in. If you run the pump until it cavitates and turn it off, then take the fuel pickup loose there will still be fuel draining thru the small opening leading to the fuel pickup. So instead of taking the pickup loose, let it sit a while and then run the fuel pump some more. You should be able to get almost all the fuel out.
Tony
Since I very recently did my annual - -
I put my 5 gallon fast-flow gas can under the gascolator, with the drain removed, and turn the pump on. When it starts to change sound, indicating it is getting low, turn it off for 15 seconds, then turn it on again. When the pump really starts to 'hammer', it is done. When I take the fittings off the tank, I get a few drops only. Not a big deal at all.
John Bender
I put my 5 gallon fast-flow gas can under the gascolator, with the drain removed, and turn the pump on. When it starts to change sound, indicating it is getting low, turn it off for 15 seconds, then turn it on again. When the pump really starts to 'hammer', it is done. When I take the fittings off the tank, I get a few drops only. Not a big deal at all.
John Bender
PAP G4
I'm working through the PAP and have completed section G4. The checklist in this section includes the following:
� Filter fuel and put back into fuel can. Measure-out 1 gallon fuel from fuel can and add to tank.
� Turn master switch "ON", turn fuel valve "ON". Measure the time from the fuel valve opening until tank is empty.
� Time required for electric pump to flow 1 gallon: _________seconds (max time: 180 seconds)
When I did this, the 1st 3/4 of a gallon was pumped out in less than 120 seconds, but the last 1/4 of a gallon had to be pumped in stages (see previous entries above) and exceeded the 180 second maximum.
I wondered if this is due to the small holes in the baffles, and if this part of the PAP was to measure fuel flow through those baffles or fuel flow in general. So then after filtering the fuel, I put 2 gallons back into the tank and ran the test again, measuring the time it took to pump out the 1st gallon of fuel. This time, it took under 180 seconds to pump out 1 gallon. With this result, I have to ask, what are my next steps? Are the baffle holes too small?
Slane
I'm working through the PAP and have completed section G4. The checklist in this section includes the following:
� Filter fuel and put back into fuel can. Measure-out 1 gallon fuel from fuel can and add to tank.
� Turn master switch "ON", turn fuel valve "ON". Measure the time from the fuel valve opening until tank is empty.
� Time required for electric pump to flow 1 gallon: _________seconds (max time: 180 seconds)
When I did this, the 1st 3/4 of a gallon was pumped out in less than 120 seconds, but the last 1/4 of a gallon had to be pumped in stages (see previous entries above) and exceeded the 180 second maximum.
I wondered if this is due to the small holes in the baffles, and if this part of the PAP was to measure fuel flow through those baffles or fuel flow in general. So then after filtering the fuel, I put 2 gallons back into the tank and ran the test again, measuring the time it took to pump out the 1st gallon of fuel. This time, it took under 180 seconds to pump out 1 gallon. With this result, I have to ask, what are my next steps? Are the baffle holes too small?
Slane
I have participated in draining the fuel from 3 RV-12s, mine and 2 others. All 3 required shutting off the fuel pump and waiting for fuel to flow through the holes in the baffles, then turn the fuel pump back on, and repeat a few times, in order to drain the last bit of fuel out of the tank. Your situation sounds normal to me. If it takes 3 minutes to drain out the last gallon of fuel, that is 20 gallons per hour. The engine will not burn fuel that fast. If the tank only has 1/4 of a gallon left while flying, hopefully the RV-12 in on final approach. The nose down attitude will help the remaining fuel drain out to the pump.
The purpose of the baffles is to prevent all of the fuel from rushing to the rear during takeoff and uncovering the outlet port. If the holes in the baffles were larger, then taking off with about 4 gallons of fuel would allow too much fuel to slosh aft, uncover the outlet port, and the engine would quit. I would leave well enough alone.
Maybe Scott will give his expert opinion.
Joe Gores
The purpose of the baffles is to prevent all of the fuel from rushing to the rear during takeoff and uncovering the outlet port. If the holes in the baffles were larger, then taking off with about 4 gallons of fuel would allow too much fuel to slosh aft, uncover the outlet port, and the engine would quit. I would leave well enough alone.
Maybe Scott will give his expert opinion.
Joe Gores
DHeal
Well Known Member
When I need to drain a lot of fuel from my RV-12's tank, I temporarily disconnect the fuel outlet hose fitting on top of the gascolator (i.e., the one from the gascolator to the engine-driven fuel pump) and install a homemade "inverted-U"-shaped aluminum tube/AN fitting on the gascolator outlet. Then turn on the electric boost pump and drain out the tank in steps as noted above into a gas can placed beneath the "inverted-U"-shaped tube.
Turn OFF the main fuel valve before you start disconnecting any of the above lines. Be prepared for a bit of residual fuel spilling out when you first crack open the gascolator fitting. Alternatively, you can shut OFF the main fuel valve and run the engine until the fuel lines are empty.
Make sure you have bonded/grounded everything and, as always, have a fire extinguisher nearby.
Turn OFF the main fuel valve before you start disconnecting any of the above lines. Be prepared for a bit of residual fuel spilling out when you first crack open the gascolator fitting. Alternatively, you can shut OFF the main fuel valve and run the engine until the fuel lines are empty.
Make sure you have bonded/grounded everything and, as always, have a fire extinguisher nearby.
If you have access to a fast-flo tank and pump, you can put the hose down in the tank and turn the pump backward and evacuate the tank. You will be left with a gallon or two in the baffle area to pump out with the a/c fuel pump. When pushing the hose into the tank. be careful not to snag the fuel return.
Hey Tim - -
not sure your question was answered. Take the sample test fitting out of the bottom of the gascolator. Turn the fuel valve on with a collector of your choice under it, and turn the pump on. The pump is designed to run continuously anyway, so won't hurt it unless you let it run dry for a long period of time. A 5 gallon fast-flow can fits under the gascolator perfectly. As Dave said, you can do it different ways.
not sure your question was answered. Take the sample test fitting out of the bottom of the gascolator. Turn the fuel valve on with a collector of your choice under it, and turn the pump on. The pump is designed to run continuously anyway, so won't hurt it unless you let it run dry for a long period of time. A 5 gallon fast-flow can fits under the gascolator perfectly. As Dave said, you can do it different ways.
