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Commander
15th Jun 2005, 13:15
Well guys and girls; I would like to investigate a little. We all know that after refuelling the fuel has to settle before we're able to draw any water if there is any. But the reality is that this could take hours... days even. So - do you instruct your students to draw fuel after refuelling or do you tell them the truth about it?

FlyingForFun
15th Jun 2005, 13:50
If re-fuelling then going flying, I sample the tanks straight away. Sure, any water probably hasn't had time to settle - but it's better than not checking at all, and it will also highlight other problems, for example if you've accidentally put jet fuel into your aircraft. And in one case a few months ago, I did find water in my fuel sample, although it may have dripped into the tester from somewhere other than the fuel tank since the aircraft was wet from rain.

If not flying straight away, then taxy back to the hangar and leave sampling until the pre-flight before the next flight. I always make sure I check the fuel strainer in this case, too, since anything that was near the fuel pickup line immediately after refuelling will by now have found its way to the strainer.

I also sample fuel on the first flight of the day (the A-check), and any time the aircraft has been left standing out in the rain.

FFF
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jamestkirk
15th Jun 2005, 15:30
I too am a little worried about the first refuel of the day out of the fuel tanks into the aeroplane.

I place I used to fly at had a tank that was notorious for collecting water overnight.

However. If you fly at a larger airport where the fire crew are re-fuellers. They will generally check the tanks for water,density etc every day before anyone pulls up.

If this is representative i would suggest having a word with them about the checks they do as its quite interesting.

If not, i am not too sure that it takes hours or days for water to settle in a tank. I certainly, from the example above cleared water from the tank after re-fuelling, relatively quickly.

Although, i could find myself being stood correctly

Miserlou
15th Jun 2005, 16:06
I'd like to ask where this water has come from. Water doesn't usually just appear. Take a sample of the fuel you're about to tank, if you like.
So if you check the fuel supply before refuelling, and have already checked the aircraft, it is not unreasonable to assume that you have a clean supply.

When I was responsible for a fuel supply I always used to show the samples which I'd taken from the bowser each day and keep them for a number of days so that I could prove the supply to be clean.

By all means get students to check the fuel until it becomes second nature to be sure of the quality of the fuel but it is counter-productive to go through actions which, as you point out, don't make sense.

Top tip. If you pull a sample which is free of water, put some water in it (spit if need be). You won't get anything out of a fuel tank that doesn't smell and feel like fuel (the glass may also be stained by the dye) so the only way to be sure that your sample is clean is to see that the two fluids don't act like each other.

BigEndBob
15th Jun 2005, 20:53
Only time i've seen water in fuel is after a heavy downpour of rain or aircraft has stood outside for several weeks.

Always used to rock aircraft gently, then drain fuel long before student got his hands on it.

Put water in sample to show student what he might see, as it is rarely seen. Also the pour sample onto paper, avgas will evaporate, but jet fuel will leave a greasy spot.

Warn student not to get avagas onto hand, good way to get dermatitus.

bookworm
17th Jun 2005, 18:55
We all know that after refuelling the fuel has to settle before we're able to draw any water if there is any. But the reality is that this could take hours... days even.

I'm not sure it does, you know. If you introduce a drop of water into a jar of AvGas, it settles to the bottom pretty quickly. OK, in a large tank the fuel will tend to swirl around for a while, but I think it dissipates quickly too.

If there's a significant amount of water in the fuel, enough to affect your engine, say, 20 minutes after refueling, you should be able to detect some of it after 10 minutes, I think.

2close
18th Jun 2005, 08:59
I seem to recall reading (within the last year or so) that an aircraft's CofA is invalidated following refuelling until a fuel sample has been taken and checked.

If this is the case, it stands that fuel samples must be taken after every refuelling.

Maybe the most appropriate time to refuel, wherever practicable, would be at the conclusion of flight A, which would probably give any contaminant time to settle before the next flight; the only a/c movement between refuelling and the next pre-flight check (and flight) would be taxi-ing.

Saying that, how long would it take water contamination at the bottom of the fuel tank to get into the engine and cause a stoppage?

Or is that like asking, 'how deep is a hole?'

Regards,

2close

Miserlou
18th Jun 2005, 22:53
Like I said. Check the bowser is clean before re-fuelling from it!

And that can be just as important when using JET A1 from an infrequebtly used supply. An infection of algae is a pig to get rid of not ot mention the nukber of times you'll have to change the filter. More important now that diesels are becoming so popular.

bookworm
20th Jun 2005, 07:21
I seem to recall reading (within the last year or so) that an aircraft's CofA is invalidated following refuelling until a fuel sample has been taken and checked.

If by "an aircraft" you mean a specific type, I cannot contradict that. If you mean any aircraft, that is certainly incorrect. There is no such general requirement.

The commander is required to ensure that any pre-flight check system established by the operator and set forth in the operations manual or elsewhere has been complied with by each member of the crew of the aircraft.

If that pre-flight check system includes a sampling after refuelling, then it must be carried out.

Onan the Clumsy
21st Jun 2005, 16:33
Not much of a problem in Texas :}

Julian
22nd Jun 2005, 09:51
well check the fuel for tumbleweed then :D

Gerhardt
6th Jul 2005, 01:30
*looks up* Now that's funny! And from a Brit, too. Probably just sore about us celebrating yesterday.

1. Always take a sample. There's no downside and it is possible you'll find something.

2. Do tell your students that it's likely to take a while for the water to settle. Probably when he's about 200 ft AGL.

Keygrip
6th Jul 2005, 03:37
As an ex-military (helicopter) refueller - we always checked every aircraft during the morning "Check A" (which was signed for) - we always checked every fuel bowser every morning, with a 1 liter withdrawal - which was also signed for.

If an aircraft was subsequently refuelled from that (or any other) KNOWN CLEAN SOURCE then water checks were not done until tomorrows Check A.

jamestkirk
8th Jul 2005, 17:46
What harm would it do just to check a fuel tank for water a little time after the A/C has been refuelled.

Or, am i just adding to the plethora of opinions.

And always remember that fuel burns and water does not. As you can see, i am an excyclopedia (yeah ,whatever about the spelling) of knowledge

-IBLB-
8th Jul 2005, 20:43
If there are large amounts of water, it should settle within a minute of ten-fifteen. If it is clear after that time, there is probably (!! i am not liable for anything here...) not enough to do alot of damage.

Personally, i drain before each flight, fueled or not, rain or not, you never know if the person before you did a proper job, unless you own your own plane, but even then...)

The water can come from different sources.
-water in the fuel
-watercondensation in tanks (overnight, no full tanks, etc...)
-watercondensation in fuel truck
-leaking seals/rain

-IBLB-

ShyTorque
11th Jul 2005, 22:12
^The minimum settling times for AVGAS and turbine fuels are 15 minutes and 1 hour, respectively, per 30 cm depth of fuel. Settled water will become suspended if the fuel in the tank is agitated, for example, when fuel is added.^

Not my personal quote, but that of the South African CAA.