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-   -   To drain or not to drain (https://www.pprune.org/private-flying/639674-drain-not-drain.html)

TheOddOne 5th Apr 2021 22:01

I teach NOT to put fuel back in the tank - it's considered contaminated, even if it looks OK. Good habits start with the first flying lesson. We had no end of trouble trying to lighten a big (i.e. fully laden 747) aircraft stuck in the mud at a well-known airport in West Sussex years ago. As it was a foreign carrier no-one would accept the fuel off it (over 100 tonnes) as they considered it contaminated. We had no bowsers on site either (another story) as all fuelling is done from the hydrant system.
I DO teach spill it onto concrete (not asphalt as it melts it) and watch it evaporate. If it's all water, it can still smell of AVGAS and have a blue tinge, but the evaporation test is positive for fuel. We've had one tank on our PA28 annoyingly have remnants of water contamination (admittedly only small globules of water) after being left out in the rain at maintenance.
Also, as above, it's a waste of time doing drain checks unless the aircraft has been stationary for at least a couple of hours, as the contaminant will be in suspension. Fortunately, our AVGAS supply at the airfield has a good filtration system and is checked daily.
We do our drain checks in the hangar, before moving the aircraft, at the start of the day.

TOO

Double Back 6th Apr 2021 06:46

TOO, same here, from my airline Years, if the refueling crew made a mistake having too much fuel added, we were in trouble if MTOWt did not allow for it. Most airports would treat is as chemical waste which was horrendously time consuming and expensive to get rid of it.
I feel the same like You that draining directly after refueling is nonsense, and also our field's underground fuel tanks are checked every morning.
For me, with a full day of flying planned, it would be sufficient to have it checked the first flight of the day only. However most flight manuals don't take that option into consideration and thus doing otherwise You are operating against the POH. I work in a certified environment which has yearly audits and it is difficult to "prove" any drifting away from the manufacturer's manual, as being a safe option. Older manuals do not have any consideration for the environment and take the most "safest" option that would get them the lowest chance of being sued after an engine failure with an ending in a loss of life/high cost case.

Noteworthy tip: a long time ago we had one after the other C150/152/172 getting water after having been in the rain. All of them showed cracks around the fuel tank neck area. At that time the airport used an awkward type of fuel pistol, renters tended to hang it in at a shallow angle, even lean on it to glance inside the tank, so it acted as a crow bar. It took a while before everybody was realizing this and finally the fuel company, only after complaining for a long time, changed the pistols. It is probably more likely to happen with high wings with people balancing on stairs.


Brian Pern 6th Apr 2021 08:12


Originally Posted by ericferret (Post 11022897)
Having a coffee with the KLM station engineer in Dar Es Salaam, I was bemoaning the loss of about 30 gallons of Jet A when defueling. He went on to tell me about a spillage he was involved in at Lagos Airport.
5 tonnes!!!. "However it was Nigeria so nobody cared".

The crazy world of Nigeria!!, always hated going down there! But at the threat of tread creep, there are other ways of losing a few tonnes Jet A in Nigeria, which is why it is wise not to fill up when you leave the plane parked up for a few days!! The locals love it

ericferret 6th Apr 2021 09:38


Originally Posted by Brian Pern (Post 11023195)
The crazy world of Nigeria!!, always hated going down there! But at the threat of tread creep, there are other ways of losing a few tonnes Jet A in Nigeria, which is why it is wise not to fill up when you leave the plane parked up for a few days!! The locals love it


Turbine helicopter pilot reported that the engine flamed out after start and now would not start.
Investigation revealed that the tank was full of water.
Locals had put a water hose into the tank to "float" the fuel out.
At least they didn't punch a hole in the bottom of the aircraft.
Pilot had carried out a visual water check, not used paste or capsules, looked nice and clear!!!!!
Africa, great place if you have a sense of humour.

ericferret 6th Apr 2021 09:45

Can't speak for all airports but one major U.K will defuel into a bowser and will pump it back into an aircraft owned by same company.
Depends on having a free bowser and the fuel passing the normal pre delivery checks..

Guy walks into hangar at same airport and asks "can anybody use some Jet A".
Thinking some of that would go in with the diesel in my car I ask how much?

9 tonnes!!!!!!

Airliner had done a heavy landing and needed wing repairs hence total defuel.
9 tonnes got sent as waste oil, I'm still crying over that one.
Would have powered my central heating for years.

Fl1ingfrog 6th Apr 2021 10:00

It is my experience that draining the fuel regularly also has a maintenance benefit, particularly for aircraft that are picketed outside. This regular flushing keeps the drain clear of sediments and therefore ensures a prevention of drain leaks. I'm surprised that some have never found water or sediment in the fuel because it is extremely common for aircraft kept outside but not only. Much of the water found in the fuel may also be from condensation. It is good practice to always fill the aircraft to maximum for overnight parking if at all possible: W & B requirements for the next flight the following day may prevent this.

anxiao 6th Apr 2021 11:35

When Kai Tak airport, Hong Kong was de-certified and the government wanted to sell it for housing and commercial use, the 'elf 'nd safety bods in the environment department said they better do some checks. 60 years of fuel and oil spills on the concrete had seeped into the subsoil and to bring it back to building standards they had to take two metres off the top of the airport and steam it clean. As I remember it took about six years. Two metres times the size of an airport is a lot of rubble.

So perhaps if you want to make sure that developers cannot economically re-develop your airport, keep killing the weeds with the fuel drains and remind them when they come round to buy it that they will have to clean up the entire airport. :}

Krystal n chips 6th Apr 2021 13:27

Been reading the posts on here with, in some cases, bemused interest . Notably those where the drained fuel is returned to the tank. How much are you actually draining here ?. ..being an engineer, the short and only answer irrespective of the volume would be "no way ! "

I admit, I have had little to with GA over the years, but a lot to do with the airline world and the sample size did vary according to type, but even so, it was minimal.

As for the standards, I can think of two operators who would send the F/E down to physically check the bowser and aircraft sample before fuelling began, another sent a usually disgruntled F/O. To be frank, you can never do enough water drains on fuel tanks. As anybody who has encountered cladosporium resinae, ( that's the extent of my Latin ) inside a tank will confirm, the stench is never forgotten....and then comes the hard work.... inspecting for the corrosion and rectifying the damage.

A slight thread drift. but, on the subject of water and drains, the fuselage water drains are another function that need to be frequently emptied.....again, it's that old favourite silent killer, corrosion, that needs preventing. How many check those as well ?

I agree, that, in a different era as they say, disposal of the sample was to simply tip the sample jar down and onto the ramp....but that's long gone so you would think it prudent for any airport / airfield operator to provide a dedicated container to promote their green / eco credentials.

MarcK 6th Apr 2021 16:41


Originally Posted by TheOddOne (Post 11023006)
I teach NOT to put fuel back in the tank - it's considered contaminated, even if it looks OK.
...
I DO teach spill it onto concrete (not asphalt as it melts it) and watch it evaporate. If it's all water, it can still smell of AVGAS and have a blue tinge, but the evaporation test is positive for fuel. We've had one tank on our PA28 annoyingly have remnants of water contamination (admittedly only small globules of water) after being left out in the rain at maintenance.
Also, as above, it's a waste of time doing drain checks unless the aircraft has been stationary for at least a couple of hours, as the contaminant will be in suspension. Fortunately, our AVGAS supply at the airfield has a good filtration system and is checked daily.
We do our drain checks in the hangar, before moving the aircraft, at the start of the day.

TOO

In the US, if you dump Avgas onto the ground you will get a big fine, and maybe lose access to the airport. GATS jars are very efficient at separating water, and the gas you put back into the tank is the same gas you just tested, so how is it contaminated? Water separates from Avgas in about 10 minutes. Not everyone has a hangar.

ahramin 7th Apr 2021 00:54


Originally Posted by TheOddOne (Post 11023006)
I DO teach spill it onto concrete (not asphalt as it melts it) and watch it evaporate. If it's all water, it can still smell of AVGAS and have a blue tinge, but the evaporation test is positive for fuel.

If it's all water, it will be obvious to anyone paying attention as it drains out of the tank. Water and fuel have very different viscosities and look very different coming out the drain. No need to contaminate the ground with it.


Originally Posted by TheOddOne (Post 11023006)
Also, as above, it's a waste of time doing drain checks unless the aircraft has been stationary for at least a couple of hours, as the contaminant will be in suspension.

OWT. If you're talking about right after fuelling, it's not a likely source of water and can take much more than a couple hours to settle out. If you're talking about water that has already accumulated in the bottom of the tank, moving the aircraft around is not enough to mix the water into the fuel. With high wing aircraft, if the bottom of the tank does indeed hold water you will get more of it out by moving the plane around before sampling. In fact if you do find water in your sample you'll definitely want to rock the wings to help the water make its way to the drain. In the worst cases where rain has been dripping into the tank through the filler cap it is best to start the engine so that the vibration helps the water move down to the drain.

Booglebox 8th Apr 2021 17:08


engine fuel filter from a C172 requires two persons
Nonsense. You just need to work on your technique!

I once drained what seemed like loads of water out of a 172 fuselage drain. I'm not sure whether it was due to preceding rain or whether it just hadn't been done for a while. This is a picture when I was already on the 3rd or 4th tube.
Took about 4 or 5 tubes until it was completely clear. And then I checked again with a non-contaminated tube.

https://cimg4.ibsrv.net/gimg/pprune....a740a9b9fd.jpg


BoeingBoy 8th Apr 2021 17:47

In the commercial world removed fuel was considered waste only because the risk of litigation returning on the fuel company should it prove faulty was deemed too great. Whilst I have no issue with that where public transport is concerned for GA purposes I take a more pragmatic view.

I was brought up to throw the fuel away in an arc, and always did so until doing a check out with a school in Florida. The instructor looked at me aghast and said that apart from the fact that the fuel was perfectly useable before it came out, and given that the little plastic tube I'd just put it into was kept in a wrapper in the aircraft at all times, it was probably safe enough to put it back in. The cost to the school of doing it every flight would be more than noticeable on an annual basis. I duly complied. However it was his next comment that stayed with me.

"Before you throw that fuel away, just remember it might be the last drop that gets you to the field, or to the coast line in the event of you needing every gallon on board".

Seemed like sound advice and whilst I always drain my own aircraft if it's has been standing with partial tanks for more than 24 hours. If it looks okay it goes back in.

B2N2 8th Apr 2021 18:29

It’s ludicrous to consider fuel to be contaminated once a sample has been drained in a clean container that is specifically designed for the purpose.
Its been in there literally seconds before you pour it back in after inspection.
What in Gods green earth could happen to a fuel sample to now make it dangerous to life and limb?!
Jetfuel is a different story as it deals with a entirely different universe of regulations and quantity.
Plane I fly we regularly land with 15-30 TONNES of fuel.
This fuel was pumped onboard in a country half a world away by provider which is not certified to do so at the destination, quality checked by a foreign company whose certification is not recognized ( pilot licenses/certificates anyone?) by the destination and therefor an “unknown” and hence the prohibition against draining/mixing/resale.
You can wear a Airline Capt Uniform while flying a GA SEP but that doesn’t make you so.
You can try and apply big plane regulations or procedures to little planes....doesn’t make it so.

Booglebox 12th Apr 2021 19:01


with a school in Florida
A lot of places in Florida have very strict groundwater contamination laws, with big fines if you get caught slinging avgas across the ramp. (Silly I think, as it evaporates, but there we are)


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