When do you drain fuel?

Marcsamo said:
Hello guys,

do you drain fuel before fueling, after, or both? And why?

Thank you
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I usually refuel at the end of a flight before I put the airplane back in the hanger. I drain the fuel to check for water immediately before I pull the airplane out of the hangar for the next flight.

If I did not refuel before putting the airplane to bed, and have to add fuel before a trip, I check the fuel drains after adding that fuel. The Aztec gulps fuel and it takes a while to fuel the four tanks so there's plenty of time for any water to separate (I have only once recovered water from any of the fuel drains on the airplane).
 
GRG55 said:
I usually refuel at the end of a flight before I put the airplane back in the hanger. I drain the fuel to check for water immediately before I pull the airplane out of the hangar for the next flight.

If I did not refuel before putting the airplane to bed, and have to add fuel before a trip, I check the fuel drains after adding that fuel. The Aztec gulps fuel and it takes a while to fuel the four tanks so there's plenty of time for any water to separate (I have only once recovered water from any of the fuel drains on the airplane).
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Thank you, there's people who say that it must be drained before fueling the aircraft because once you add fuel, water would mix with fuel and you would not be able to see it after fueling. And there's people who say you gotta do it after fueling so you can check how's the new fuel added. I agree in fueling the aircraft before you take it to the hangar.
 
Marcsamo said:
Thank you, there's people who say that it must be drained before fueling the aircraft because once you add fuel, water would mix with fuel and you would not be able to see it after fueling. And there's people who say you gotta do it after fueling so you can check how's the new fuel added. I agree in fueling the aircraft before you take it to the hangar.
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Water and fuel really don't mix so any substantial volume of water will settle quite quickly.

Always good to check after refueling since, while rare, the pumped fuel could be contaminated. But never hurts to check more frequently.

Ever time I actually found water it was after heavy rains on a tank that had a loose seal on the wing.
 
It doesn't hurt to do fuel checks anytime. But me is normally after fueling.
 
Marcsamo said:
Thank you, there's people who say that it must be drained before fueling the aircraft because once you add fuel, water would mix with fuel and you would not be able to see it after fueling. And there's people who say you gotta do it after fueling so you can check how's the new fuel added. I agree in fueling the aircraft before you take it to the hangar.
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If the tanks don't normally indicate water when drained I believe the greatest danger is introducing water into the system while refueling. I will never fly a refueled airplane without checking the fuel drains.

As for water already in the tank mixing while fuel is being added, I would suggest a check of the POH fuel drain check procedures for your specific airplane and follow them. Perhaps it is an issue for some airplanes with smaller fuel tanks if insufficient time passes between topping up the tank and checking the drain?
 
Before the first flight of the day, on my daily flight check.

If I'm suspicious of a fuel pump or don't have a quality letter (for work) I'll white bucket test it before it hits my tanks.
 
After fueling ,before first flight of the day.
 
I think we all ask ourselves this all the time. Does my tanks have water in them? We also ask ourselves should I check before or after fueling. I hate guessing at anything. If you have ever watched me, I have been known to check my tanks before fueling, after fueling, and after setting. I have done all the above.

More then once I have found water in my tank. I solved the problem by avoiding fuels with any ethanol. After switching to this type of fuel, the water issue has never came back. I use auto fuel.

If you have a question as when to do something like this, do it. Do it before, during and after, if that makes you feel all fuzzy inside. Maybe its a little over the top but who gives a darn if it makes you feel all warm and fuzzy. One thing for sure, you checked for water.

Let me as this. You found no water, what do you do with the fuel you just removed?
 
I am very picky when it comes to fuel. I check before and after. This week when I called the owner he said he just flew and filled it I still checked the levels even though the gauges said full too. I still sumped the tanks even though it flew an hour or so before I got there. If I have the FBO fill it I ask them to leave the caps off and I still stick the tanks then test after.

For the few seconds it takes why not.
 
DFH65 said:
I am very picky when it comes to fuel. I check before and after. This week when I called the owner he said he just flew and filled it I still checked the levels even though the gauges said full too. I still sumped the tanks even though it flew an hour or so before I got there. If I have the FBO fill it I ask them to leave the caps off and I still stick the tanks then test after.



For the few seconds it takes why not.
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Why have the FBO leave the caps off?
 
JoseCuervo said:
Why have the FBO leave the caps off?
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He says he filled it I still check that it is really full. I know really anal but when it comes to gas I don't want to be that guy.

I normally fly a 172M with 48 gallon tanks if I stick the tank and it is much less than half even for my typical one hour local flights I fill it up. I am paying wet so how much fuel I carry unless weight is an issue doesn't really matter to me.
 
"You found no water, what do you do with the fuel you just removed?"

If no particulate is in the fuel I return it to the tanks. If there is water or particulate I discard. Be aware that some states are not good with the later.
 
Not as often as I should. I do always check it if the airplane has sat outside when it has rained.
 
I have 13 sumps!! 5 each wing and 3 under engine. Wears on the old knees but still done 1st flight of the day and after refuel
 
DFH65 said:
I am very picky when it comes to fuel. I check before and after. This week when I called the owner he said he just flew and filled it I still checked the levels even though the gauges said full too. I still sumped the tanks even though it flew an hour or so before I got there. If I have the FBO fill it I ask them to leave the caps off and I still stick the tanks then test after.

For the few seconds it takes why not.
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Leaving the caps off is an invitation to insects. They love the smell of gasoline, for some reason, and crawl into the tank. I can tell which pilots are doing that; their sump drains are slow to drain and they leak, their little seals and passages contaminated with bits of bug. It takes time and costs money and makes a dangerous mess to remove that drain valve from a tank and clean or replace it and drain some of the fuel to flush out the bug bits.
 
Dan Thomas said:
Leaving the caps off is an invitation to insects.
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It's an invitation for a lot worse too. My policy is to never walk away from an airplane leaving it in an unairworthy condition. Things like exterior control locks that you intend to remove before takeoff, keys in cargo doors, dipsticks removed, oil filler caps off, etc. It's all an invitation for disaster when something distracts you from your good intentions.

dtuuri
 
DFH65 said:
He says he filled it I still check that it is really full. I know really anal but when it comes to gas I don't want to be that guy.



I normally fly a 172M with 48 gallon tanks if I stick the tank and it is much less than half even for my typical one hour local flights I fill it up. I am paying wet so how much fuel I carry unless weight is an issue doesn't really matter to me.
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How many good things can happen by the FBO leaving the caps off? I can't think of a single one.

How many bad things can happen with the FBO leaving the caps off? I can think of quite a few bad things.

Water gets in.
Debris gets in.
Caps roll off the wing.
You forget the caps.
Caps scratch wings.


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I drain fuel before every flight.
 
Sump fuel with Gats jar before leaving hanger. Put fuel back in after I stick for fuel quantity. Also sump after top off and discard.
 
Ya'll know that sumping right after fueling or flying is pointless, gotta let things settle first.
 
1600vw said:
I think we all ask ourselves this all the time. Does my tanks have water in them? We also ask ourselves should I check before or after fueling. I hate guessing at anything. If you have ever watched me, I have been known to check my tanks before fueling, after fueling, and after setting. I have done all the above.

More then once I have found water in my tank. I solved the problem by avoiding fuels with any ethanol. After switching to this type of fuel, the water issue has never came back. I use auto fuel.

If you have a question as when to do something like this, do it. Do it before, during and after, if that makes you feel all fuzzy inside. Maybe its a little over the top but who gives a darn if it makes you feel all warm and fuzzy. One thing for sure, you checked for water.

Let me as this. You found no water, what do you do with the fuel you just removed?
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I agree with you and so I do. I do it before and after, but in my head there's always the same question, you know I'm still a student pilot and different instructors tell me different things. And because of that, some tell me to put the fuel again in to the tanks and some to throw fuel away.
 
Water is found in three forms in the fuel: free water, the stuff we find when sumping. Entrained water, which is very hard to see, being tiny, suspended droplets, and is usually only noted in cold weather when it freezes and forms "snowflakes" in the fuel sample. Dissolved water, which will pass through unnoticed, and all fuel has a bit of it.

Get the free water out. In AD 84-10-01, Cessna calls for rocking the wings VERY vigorously (10 inches up and 10 inches down, 12 times, with the tail pulled close to the ground) to dislodge any water from wrinkles in the floor of the fuel bladder and to get it to the sump drains. If that amount of shaking brings the water to the sumps instead of dispersing it through the fuel, I can't see that we have to leave the airplane sit for long to let the "water settle out."

http://www.airweb.faa.gov/Regulator...7CA32CBFD7107A87862569B9004D1566?OpenDocument
 
James331 said:
Ya'll know that sumping right after fueling or flying is pointless, gotta let things settle first.
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Have you ever tested MoGas for ethanol using a clear jar? This is done by putting about an inch of water in the bottom of a jar, mark the level with a sharpie. Then fill the jar with gas. Shake, shake, shake, shake. Set it down. If the gas has ethanol in it then it will migrate into the water and the water level will rise.

If you had ever done this test then you'd have seen that the water has settled out of the gas and the level is back to the line in 3 to 5 seconds and it won't fluctuate from there even if left to sit for another hour.

I've always been amazed at how quickly it re-separates.

Yes, fuel tanks are larger and it might take a bit longer but I have no doubt that any water you pumped into your tanks while fueling will have settled out before you even get the hose reeled up.
 
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dtuuri said:
It's an invitation for a lot worse too. My policy is to never walk away from an airplane leaving it in an unairworthy condition. Things like exterior control locks that you intend to remove before takeoff, keys in cargo doors, dipsticks removed, oil filler caps off, etc. It's all an invitation for disaster when something distracts you from your good intentions.

dtuuri
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Reading too much into what I said. First of all I am standing right there. I don't let people fuel unless I am there. Say the guy drops the ladder or the fuel hose I am not taking the blame for the possible resulting damage.

I don't know how many insects can land in there when I am watching him fuel the plane. I generally climb up the ladder before he moves it make sure it is full then close it then help the guy move the ladder. So they are open maybe 20 seconds longer a risk I am willing to take.

Anytime the plane is out of my sight bathroom break whatever. I do a quick walk around basically an abbreviated pre-flight and I also do a stand back and look to make sure I am getting the big picture and not missing anything.
 
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If I'm standing there while someone fuels my plane, I just as well do it myself, then there's no reason to leave the caps off. ;)
 
bluerooster said:
If I'm standing there while someone fuels my plane, I just as well do it myself, then there's no reason to leave the caps off. ;)
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I would be happy to pump it actually would prefer it. In the past at this airport you might have been able to do it yourself although it was not set up for self service and the guy had to come unlock it anyway.

Recently they got rid of the fuel tanks and now just use a fuel truck. So the guy has to do it.

Honestly since renting this plane I have not had to fill it many times usually there is enough gas in it when I get it. It isn't flown all that much. I think I may actually be one of maybe two people who rent it. The owner gives lessons in it but only has a few students. A busy month might be 10 hours. Typically any flight that takes it under a half a tank he fills it.
 
I sump after fueling. In the time taken to put away the hoses and pay the bill the fuel/water will separate enough to be noticeable if there is water.

Beware to sump enough that you don't get a cup of water and no fuel. You won't see a line and think it is all fuel.

I used to use a GATS jar but after the third one broke I got a straight one from Sporty's. Now if I see water or particles I pour it in my lawn tractor (tow motor) otherwise I return it to the tank.
 
cgrab said:
[snip]
Beware to sump enough that you don't get a cup of water and no fuel. You won't see a line and think it is all fuel.
[snip]
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I hold the clear tube/jar up next to the white paint on both planes I fly. If I on't see the blue tint I know I've got something other than 100LL (i.e. water). Having so much water that I get a full sample hasn't happened to me yet, but I still check.

John
 
If you have to hold the jar against a white background to determine the color, I would highly suspect the fuel.
Maybe if you are sumping MoGas, but the blue in AvGas is so blatant that any background other than light blue should make the color obvious.
 
Two times

1. before every flight.
2. if i add fuel, i wait 5 minutes and then sump them all
 
What do you folks with Comanches do? Use a bucket?
 
The first time I sumped my Cherokee (after taking ownership of it back in May last year) it had water at all three sump points.

Hasn't ever happened again.I sump everytime I go up or anytime I add fuel. There have been times that I've said meh..I don't wanna bother, but I force myself to do it. I'm not going to be a statistic because I didn't want to spend a minute sumping.

I live in FL and I've seen people drop entire sumps onto the pavement at my airport. All of the fuel I sump I put back in thanks to the GATS. The only thing that stays behind in the jar is water and/or bugs/dirt that get sucked into the tank.

In FL if you are caught dumping fuel onto the tarmac you can be fined up to $50,000 I believe, so "some" people have been super lucky to not get caught.
 
Anyone know why so many sumps? I liked the older 172 where you pull a handle for under the engine sumps and looked for evaporation and anything left behind. The new plane has 13 and the 10 on the wings are easy but I hate getting down on my knees on the Tarmac to check the three under the engine. Will still do it for safety but will moan and groan during the process
 
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