Contaminated fuel
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Contaminated fuel
Refueling Discipline Crucial for Pilots and FBOs | BCA content from Aviation Week
This is an article about fuel contamination. But, how many of you have ever insisted on taking a fuel sample from the truck itself and if so, under what circumstances.
This is an article about fuel contamination. But, how many of you have ever insisted on taking a fuel sample from the truck itself and if so, under what circumstances.
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Interesting. Our club operates its own small (2000 litre) bowser which is refilled from the mobile one as required. We recently introduced a requirement for a daily fuel sample to be taken and logged, and kept for 7 days, and having read that I feel better about the extra time it takes up.
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The part about condensation forming in any above-ground tanks that have low fuel levels is a very important issue.
It becomes even more important when the tanks cycle through wide temperature variations over 24 hrs, and there is high humidity present.
Even the lowliest, but well-trained operator of any ground-based item of powered machinery, knows about refuelling at the end of the working day to ensure no room for condensation to form overnight in the tank of the parked machine - which will happen if left with low fuel level. Emptying any above-ground tank on a daily basis, and leaving it empty overnight on a repeated basis, will lead to a sizeable volume of water in the tank, if not drained very regularly.
Below-ground tanks suffer much less from condensation problems, due to the fairly constant temperature of the soil.
It becomes even more important when the tanks cycle through wide temperature variations over 24 hrs, and there is high humidity present.
Even the lowliest, but well-trained operator of any ground-based item of powered machinery, knows about refuelling at the end of the working day to ensure no room for condensation to form overnight in the tank of the parked machine - which will happen if left with low fuel level. Emptying any above-ground tank on a daily basis, and leaving it empty overnight on a repeated basis, will lead to a sizeable volume of water in the tank, if not drained very regularly.
Below-ground tanks suffer much less from condensation problems, due to the fairly constant temperature of the soil.
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How big a sample?
Taken when and from where?
What do you do with the fuel after 7 days?
What would you do if an aircraft crashed that had been refuelled 6 days ago?
Taken when and from where?
What do you do with the fuel after 7 days?
What would you do if an aircraft crashed that had been refuelled 6 days ago?
2. Daily, before first delivery of the day, from the forecourt unit ( the thing with the nozzle and trigger on). It's dispensed to an approved glass jar for inspection then kept in a blue tin marked with the day of the week.
Weekly, ALL the several drains at the bottom of the tank are sampled, inspected for contamination, then re-cycled. The only sample we don't recycle is from the bottom of one of the filter units, which we keep for fire training.
3. Daily, last week's sample returned through the filter system
4. Impound the sample from that day awaiting collection by the AAIB. Sadly, we had a fatal crash at an event I was helping with, a few years ago. We immediately sealed the fuel system and impounded all the samples until the AAIB arrived. We were able to say from the fuel dispensing records exactly when the fuel had been put in the aircraft and which was the relevant sample. In the event, the accident wasn't fuel related.
All our fuel activity is recorded, including SG checks of bulk deliveries. We don't deem it necessary to check SG of fuel in the tank, but would happily do so if a customer or Club member asked for it.
We have an above-ground tank and are mindful of the issues surrounding contamination from water. However, the regime of sampling we have shows that in fact we don't suffer from condensation. The fuel is actually taken by a floating device from the top of the fuel. The tank has a 200-litre 'un usable' space at the bottom, from which we draw the weekly test samples. This is where we would expect to see the first indications of contamination. We don't just rely on visual inspection for water; we use a water-finding paste which is very sensitive.
Being right on the coast, our diurnal temperate range is small. However, the downside is everything rusts like crazy in the salt air.
Another point about above-ground versus underground tanks - insurance. Apparently it's cheaper to insure an above-ground unit as any likely accident to it is going to be a single, insurable event, whereas an underground unit might leak into the surrounding soil un-noticed and the owner might be faced with an big un-insured clean-up bill.
TOO
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Thanks, TOO, very interesting.
Just to follow up, out of interest, what do you look for in the samples you take?
You mention the water sensitive paste used for the weekly samples and an SG test, but do you do any other checks as well (with the objective of potentially spotting unsafe fuel before it is dispensed - as opposed to waiting for a closer inspection after an accident)?
Thanks,
B.
Just to follow up, out of interest, what do you look for in the samples you take?
You mention the water sensitive paste used for the weekly samples and an SG test, but do you do any other checks as well (with the objective of potentially spotting unsafe fuel before it is dispensed - as opposed to waiting for a closer inspection after an accident)?
Thanks,
B.
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Just to follow up, out of interest, what do you look for in the samples you take?
Bright, Clear and Blue (in the case of AVGAS)
It's similar for Jet fuel though of course the dye is straw-coloured.
If you hold a glass sample jar up to eye-level, any solid contaminant will be apparent swirling about, settling to the bottom of the jar. Water shows up in AVGAS as small droplets. Really, it's just the same as the pre-flight samples we all take from the aircraft drains, though the plastic tubes we use aren't as good as a clean glass container.
A dullness to the sample might indicate the presence of microscopic contamination or biological growth (another issue not mentioned in the article) I think this is mostly an issue with Jet fuel, rather than AVGAS and is a consequence of having water contaminant. We don't have a test for bio contamination but keeping the fuel as water-free as possible is a good preventative measure.
Of course, apart from keeping everything clean the best thing to do is to use the fuel and keep replenishing - very difficult at this time of year!
Incidentally, the article mentions the use of a white bucket for checking fuel samples. We use a clean glass jar or a stainless steel bucket with a static line attached to it.
TOO
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I forgot to mention the fuel is also tested with a Shell water detection capsule.
Why?
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Doesn't work like that. We are a self-help club. Pilots refuel themselves, and the first of the day does and signs for the daily sample.
So, anyone who wants to can inspect it in the fuel store; and can see the record of the check in the fuel log.
So, anyone who wants to can inspect it in the fuel store; and can see the record of the check in the fuel log.
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You should always take a sample from the hose nozzle before allowing fuel to be added to the aircraft. The plastic sampler that you use for the preflight water check is fine for this.
The main reason for this sample is a final colour check to make sure that you are getting the correct fuel, any contamination should also be obvious.
There have been several fatal accidents due to turbine fuel being supplied to piston aircraft. The engine typically fails at around 50 feet as the bad fuel works its way through the pipes, gascolator etc and reaches the carb.
The main reason for this sample is a final colour check to make sure that you are getting the correct fuel, any contamination should also be obvious.
There have been several fatal accidents due to turbine fuel being supplied to piston aircraft. The engine typically fails at around 50 feet as the bad fuel works its way through the pipes, gascolator etc and reaches the carb.
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[QUOTE]You should always take a sample from the hose nozzle before allowing fuel to be added to the aircraft. The plastic sampler that you use for the preflight water check is fine for this.
QUOTE]
Well, I must say I've never been asked for this when I've been re-fuelling aircraft. I would imagine it's quite hard to get a small enough sample from the nozzle for it not to get spilt all over the place. What do you do with the subsequent sample? I NEVER put a sample from the preflight check back in the tank - I treat it as contaminated. I find some concrete and let it run out so that I can watch it evaporate. If it doesn't, then it was pure water - it can still smell like AVGAS and have a faint blue tinge to it. With our rig, we could always put it back through the filtration system.
What I ALWAYS do when re-fuelling other people's aircraft is to ask three questions - what grade of fuel do you want, which tank do you want it in and what quantity do you want in each tank? We once had a French registered C182 arrive and I'm glad I asked as it was a diesel, not immediately apparent at first glance.
TOO
QUOTE]
Well, I must say I've never been asked for this when I've been re-fuelling aircraft. I would imagine it's quite hard to get a small enough sample from the nozzle for it not to get spilt all over the place. What do you do with the subsequent sample? I NEVER put a sample from the preflight check back in the tank - I treat it as contaminated. I find some concrete and let it run out so that I can watch it evaporate. If it doesn't, then it was pure water - it can still smell like AVGAS and have a faint blue tinge to it. With our rig, we could always put it back through the filtration system.
What I ALWAYS do when re-fuelling other people's aircraft is to ask three questions - what grade of fuel do you want, which tank do you want it in and what quantity do you want in each tank? We once had a French registered C182 arrive and I'm glad I asked as it was a diesel, not immediately apparent at first glance.
TOO
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Context is important here, you are unlikely to get the wrong fuel when there is only one pump, it should have been checked before the tanker was allowed to put it in the tank.
OTOH when there is a row of 3 pumps each with long hoses lying on the ground it is very easy for mistakes to be made. I once found that the hoses for the 80/87 and 100/130 pumps had become crossed and the nozzles hung on the wrong pump at FAGC in the 70s. The scary bit is that the 3rd pump was turbine fuel - potentially nasty.
OTOH when there is a row of 3 pumps each with long hoses lying on the ground it is very easy for mistakes to be made. I once found that the hoses for the 80/87 and 100/130 pumps had become crossed and the nozzles hung on the wrong pump at FAGC in the 70s. The scary bit is that the 3rd pump was turbine fuel - potentially nasty.
Overall though, an appearance test for Avgas and/or Jet is a perfectly acceptable way for either a technical or non-technical person to determine whether fuel dispensed from a bowser may be contaminated. More subtle contaminations that can only be determined by analysis are unlikely to arise once the product has reached the airfield tank.
M9 (Investigates fuel contaminations for a living, currently in Mozambique sorting out $5mill worth of contaminated gasoil)
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Thanks for the answers but it appears that no one has actually asked for the fueling truck to do a test itself prior to fueling the aircraft. I am talking about the drains at the bottom of the fuel truck. I never have.
The article makes it sound like we should be doing this on a regular basis. Not realistic in my opinion.
The article makes it sound like we should be doing this on a regular basis. Not realistic in my opinion.
