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A gas contaminated with jet a

bryanflood

Well Known Member
So today I had less than a cup of jet a mixed into one of my tanks of 16 gallons of 100ll on accident when someone grabbed the wrong fuel hose. The pump was not on but there was residual fuel in the nozzle. Surprisingly they seemed to completely mix and not separate. I always thought that jet fuel would separate out but the mechnic at the field said that jet-a and 100ll mix. Weird, does anyone have an idea what to do with this? if I have to dump 16 gallons of 100ll gas, where does it go? My guess is the engine wouldn't even notice this small amount of jet a, anyone had experience with this? I'm sure lycoming has a bulletin advising what to do?

Bryan
 
Jet A

Fuel contamination is fuel contamination. There is no published data anywhere that I know of that allows jet A mixed with 100ll to be used by a piston engine. For what it's worth, I would, without hesitation, drain that entire tank and refill with 100ll. As for disposal, a call to your local fuel supplier would probably get you the answer. Alternatively, let your lawnmower decide if it likes the mixture. A failure there will result in a unmowed lawn rather than an unplanned arrival on top of someone's BMW.
 
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100LL/Jet A mix

Your lawnmower, 65 Mustang and a whole host of other engines will love you for bringing it home.
 
One of the big fuel suppliers bought a lot of brand new engines in NorCal somewhere around the late 80s or early 90s for failures due to Jet A getting into the 100LL supply chain.

IIRC, couple crashes also happened-----not sure about any fatalities.

Drain it would be my choice.
 
Understand the danger: Jet A has essentially zero anti-knock properties (e.g., very low "Octane number"). Engines run on substantial amounts (how large is substantial? I don't know) detonate severely, with the typical failure mode being melting a hole thru the aluminum piston, about 1/2 mile from the takeoff runway.
 
Drain it. Don't use it in your airplane. Don't even think about it.

AvGas and Jet A will mix very easily with no easy way to tell without letting it sit for hours or days.
To test for the presence of Jet A in AvGas there are a couple simple things you can do.
1. Smell it. AvGas should smell like, well, AvGas. It shouldn't smell like kerosene.
2. Pour some on a piece of paper. If it is all AvGas it will evaporate and leave the paper completely dry (possibly dyed blue and a little wrinkled but you get the idea). If there is turbine fuel the paper will never dry completely out because turbine fuel will leave a little ring of oil stain wetness on the paper.
Since you know for certain that this one tank is contaminated it will be simple to drain and flush.

Yep, back in the mid 90s a major oil company had a mishap and sent Jet A contaminated 100LL all over Northern Ca. They did the right thing and bought hundreds of new engines including a complete set of four for a B-17. No surprise that about 10 years later the same company announced they were getting out of the AvGas business.
 
Once upon a time far away from home I borrowed several jar cans to get to the village only gas pump. The jars were used for diesel fuel and were supposedly empty. I caught it timely and managed to dump the diesel ( a quart total) before filling them up. Still had some mix up engine told me that. Drain it and use elsewhere.
 
Just curious, lots of folks advocate using Marvel "Mystery" oil (mineral spirits mostly) in their fuel, so why would a cup of Marvel be ok but a cup of Jet A (kerosene) will definately kill you?
 
A full cup in 16 gallons is 1/256, or about 4 tenths of a percent. It would be interesting to conduct the standard field test for jet fuel contamination of avgas. Place a few drops of a sample on a white piece of paper and allow to evaporate. An oily ring evident after evaporation indicates jet or diesel, while an unmarked paper indicates a clean avgas sample.

Is 4/10's of one percent detectable?
 
Just curious, lots of folks advocate using Marvel "Mystery" oil (mineral spirits mostly) in their fuel, so why would a cup of Marvel be ok but a cup of Jet A (kerosene) will definately kill you?

It's not the total fraction: the trouble with kerosene is it will slowly separate and concentrate near the fuel inlet, right where it can cause explosive combustion at takeoff. If the OP let it sit long enough to solicit advice here, he'll be playing lottery no matter how small a quantity got in--it may not kill him today, but there's a high enough probability of permanent engine damage that may get him, or the next owner, some months later. Just flush it.
 
Walt asked a darn good question. And he did not advocate flying with the OP's mixed fuel, although I suspect we share the same thought; there is a point below which jet fuel would have no practical effect on detonation margin. The problem is that the limit is hard to define for all aircraft, so we use general prohibitions. Nothing wrong with that approach, but it doesn't mean we can't aim for a deeper understanding.

Misfueling accidents typically involve a lot of jet fuel...like 50 percent. High percentages won't pass a paper check. Will less than one percent go undetected?
 
Watsonville, CA

1994, Mike. I was there for some fly-in. Chevron supplier mixed A with 100 to some some immense degree. I didn't refuel with many gallons, but the blend was still way more than one cup A in 16 when combined with the residual fuel in our 172's tanks, but I didn't detect anything odd in the sump sample. Happily droned home for 3 hours behind 7:1 cylinders with no apparent issues, but this was without a four-cylinder engine monitor. Soon word got out, Chevron immediately stepped up to their responsibility and later received accolades for doing the right thing rather than trying to dodge the issue. The ticket was having proof of purchase. (I received several offers to buy my credit card voucher!) For this I received a zero-time 320, new hoses, carb O/H, even a prop O/H, gas of course, labor paid.

So I'd say our OP has no worries. Burn it off rich at low altitude, or put it in the mower. The lesson? Get a receipt and go through the tedious process of keying in your N number at the self-serve pump!

John Siebold
 
If I got one cup of Jet A in 16 gallons of avgas, I wouldn't think twice about flying with it. 100LL is 100 octane. Pleople routinely run 91 octane mogas without detonation issues. While not a scientist, I can't see how the .4% dilution of the diesel with an octane rating of 45 (don't know the octane rating of Jet A but suspect it is in close proximity to diesel), can bring the octane rating of the total 16 gallons below 91.

I suspect it would take some time for the Jet A to settle out and light agitation should easily mix it again. If I was concerned with settling, draining a gallon from the tank drain should get rid of it, just as it gets rid of water that settles out.

Just a differing opinion for consideration.

Larry
 
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I will accept the challenge. Will jetA and 100LL mix? Are they miscible?


Will they separate? I don't think so, any more than alcohol poured in water will separate. Thats why we don't have to shake the beer before drinking, right?
 
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Will Avgas Mix with Jet A

Gee....All these years I thought the JP-4 I burned a jillion gallons of in the T-38 was a mix of Avgas and Jet A. I could be wrong! If I'm not, then they mix just fine.

Update: According to Wikipedia, JP-4 was a 50-50 kerosene-gasoline blend. It had a lower flash point than JP-1, but was preferred because of its greater availability. It was the primary U.S. Air Force jet fuel between 1951 and 1995.
 
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Thanks Danny!

Thanks Danny, I think the gasoline does not include the lead additive as it plates on the hot components, but this shows it is miscible and supports my assertion.

THANKS!!!
 
So today I had less than a cup of jet a mixed into one of my tanks of 16 gallons of 100ll on accident when someone grabbed the wrong fuel hose. The pump was not on but there was residual fuel in the nozzle. Surprisingly they seemed to completely mix and not separate. I always thought that jet fuel would separate out but the mechnic at the field said that jet-a and 100ll mix. Weird, does anyone have an idea what to do with this? if I have to dump 16 gallons of 100ll gas, where does it go? My guess is the engine wouldn't even notice this small amount of jet a, anyone had experience with this? I'm sure lycoming has a bulletin advising what to do?

Bryan
Just read "Mike Busch on Engines" book and he has a fairly detailed account of a 'misfuel' situation in which Jet A was "being fueled" into his plane when he saw it happening. They did an extensive drain and purge because of the amount but he also covers the required Jet A nozzle shape (designed to prevent this) and the filler port restrictions designed to keep from accepting these Jet A nozzles on Avgas aircraft. Both details were news to me but worthy of note.

Further, the mixture was not detectable by looking at the fuel sump sample. He says they are 'highly miscible' and 'takes nearly forever to separate'. And he recommended always smelling the sump sample to detect any Jet A. Finally, he describes the paper test and its effectiveness. (Pages 192-195)

I'd recommend Busch's book for further details, as well as good advice.

Personally, I'd sump a sample, smell it, do the paper test, and decide on the evidence, if nothing more you'll have the benefit of a 'real life' story at a very low %-age of contamination to report to us. Would be surprised if less than a cup in 16 gallons is of serious concern (but it's not me or my passenger in your plane). You know best the operation of that engine and what your personal capabilities can handle. On a high DA day, full tanks, bags, and a passenger in AZ it might be different than your decision.

Let us know your findings please?
 
When I was a kid, I accidentally topped off our Chevy suburban with diesel and we ran it out of the tank. The thing ran horribly, but it ran well enough to get us home and to run the tank dry on a country road before we put in regular fuel and brought it home.

What we discovered was a little surprising and that is much of the diesel ended up in the oil. Since it didn't burn as fast as the gasoline in the mix, the gas would ignite raising the pressures in the cylinder to drive the piston down, and the pressures were high enough to drive the unburned diesel down past the rings where it collected into the sump. When you'd drain the oil, you'd drain diesel and then oil (I think that was the order).

It took a number of oil changes to get through that tank

Ultimately we had to overhaul the engine later on down the road, because diesel doesn't lubricate quite as well oil and our wear rate was accelerated during the time the diesel ended up in the oil.

So even a little bit of diesel, while it may not affect the combustion inside the cylinder, could find its way past the rings, into the oil, where there could be other consequences that go beyond 'its ability to run'.

Phil
 
Anyone have a little time on their hands? Put some 100LL in a clear jug and put a small measured of jet A and mix. let it set a couple days and take a picture for us. See if it mixes. I'm guessing it does. Any takers? I would like to know. You can't tell me this hasn't happened before to a lot of pilots.
 
Todd, I was just thinking the same thing. While I totally agree with the people that say drain the tank, I also totally agree with the others that noted that the percentage of fuel is very very small. It's not as in the mis-fueling incidents. This is a very small amount. I have kerosene and 100LL on hand, along with jars, at my hangar. When I'm out there again I'll mix 50/50 and see what happens over a couple weeks.
 
I'm not a petro engineer, so I cannot make a knowledgable comment on the effect. I do know this however: it's not worth my life to find out, even in the long run. I would always harbor a slight suspicion towards the motor as to whether or not the jet fuel had some detrimental effect that may or may not surface at a later time. Like right after takeoff in a densely populated area.
Just adding my two cents, not making assertions to the decision of the owner. YMMV.
 
When I was a kid, I accidentally topped off our Chevy suburban with diesel and we ran it out of the tank. The thing ran horribly, but it ran well enough to get us home and to run the tank dry on a country road before we put in regular fuel and brought it home.

What we discovered was a little surprising and that is much of the diesel ended up in the oil. Since it didn't burn as fast as the gasoline in the mix, the gas would ignite raising the pressures in the cylinder to drive the piston down, and the pressures were high enough to drive the unburned diesel down past the rings where it collected into the sump. When you'd drain the oil, you'd drain diesel and then oil (I think that was the order).

It took a number of oil changes to get through that tank

Ultimately we had to overhaul the engine later on down the road, because diesel doesn't lubricate quite as well oil and our wear rate was accelerated during the time the diesel ended up in the oil.

So even a little bit of diesel, while it may not affect the combustion inside the cylinder, could find its way past the rings, into the oil, where there could be other consequences that go beyond 'its ability to run'.

Phil

I had the same experience with an automotive engine. IMO conservative assumption is you're putting that cup of jet fuel kerosene into the crankcase.
 
18 hours after mixing 100LL and Kerosene. Zero separation. It's been kept very stable, with no vibrations or disturbances.
 
Fuel contamination

Well,

Thanks for all the advice. Last night i drained the tank containing the one cup of jet-a. There was no evidence of separation in the drained fuel. I also performed the paper test on the drained sample and some pure 100ll out of the other tank. There was no difference between the two, niether left stains on the paper. I even took the paper out into direct sunlight and looked through a magnifying glass. As far as i could tell the 1 cup of jet-a was totally undetectable by these methods. My own opinion is that i could have used the fuel in the plane safely, especially in cruse flight where the effective compression is lower. However, since my opinion is based on assumptions not testing i have refueled the plane with fresh 100ll.

I would be interested to figure out how the jet-a in such a low concentration affects the octane. I think it would also be interesting to learn more about how much marvels mystery oil people are running in their fuel, might have similar properties.

Thanks,

Bryan
 
I would be interested to figure out how the jet-a in such a low concentration affects the octane. I think it would also be interesting to learn more about how much marvels mystery oil people are running in their fuel, might have similar properties.

Thanks,

Bryan

The bottle of MMO that I have recommends 4oz per 10gal of gas. Sounds like that is close to what you had in your tank.
 
I would be interested to figure out how the jet-a in such a low concentration affects the octane.

Thanks,

Bryan

someone posted this on your thread. 2% Jet A mixed with 100LL drops your octane rating 1 point. Most standard compression Lycomings require an octane rating several points below 100.

Larry
 
After leaving the 100LL and Kerosene sit undisturbed for 3 days now, it's still 100% unseparated. I don't believe it actually will ever separate. I see it highly unlikely that even after a long amount of time it would separate and collect at the bottom of the tank by the inlet. I have nothing better to do with my jar of fuel, so I will just continue to let it sit and see what it looks like in a few weeks.
 
Glad to see you drained and then refilled with pure 100LL.

Used to work in a refinery as a crude unit operator and then was promoted to the hydrocracker unit.

The diesel was pulled from the crude tower into a "stripper" which had two levels, bottom level was No. 2 diesel, next level up was No. 1 Diesel or Jet-A here in Alaska. From the very top of the stripper, lighter end vapors continue back into the crude tower to continue their upward journey to the proper levels before they were condensed and removed as a liquid.

It isn't as clean as 100LL, burns hotter and has different properties than the Avgas. Turbine engines can burn almost anything liquid that will maintain a fire.
Used to fly helicopters for the military, back of book had lots of different options for emergency fuel; only one that needed an inspection/rebuild after burning was Shell gasoline that had the TC3 additive.

I would not even try 1/2 cup of Jet-A mixed in Avgas in my Lycoming.

Best regards,
Mike Bauer
 
Well after this much time I have to call BS on having it separate out. My jar 100LL + Kerosene is still completely mixed and left undisturbed. I doubt it'll ever settle out.

I happened to talk to an FBO person this weekend that fills gas for a large scale aerobatic performer. One that most of you have seen before. They actually use the aux tanks as smoke oil tanks, and then after the show once the smoke oil is used up, they refill the tanks with fuel for the trip home. I would think that if the tiny bit of smoke oil was going to make a big difference, they'd never do that.

So while I support the idea of draining the tanks, I really doubt anything would have ever come of it had it not been drained. The percentage is just too low, and the mixture would have stayed mixed plenty long to burn down the tank and refill with fresh fuel.
 
Thanks for the report Tim. I figured they would at least mix. I doubt if such a small amount in your tank would even be noticeable. Everyone has to do what is comfortable for themselves.
 
After leaving the 100LL and Kerosene sit undisturbed for 3 days now, it's still 100% unseparated. I don't believe it actually will ever separate. I see it highly unlikely that even after a long amount of time it would separate and collect at the bottom of the tank by the inlet. I have nothing better to do with my jar of fuel, so I will just continue to let it sit and see what it looks like in a few weeks.

It will be the same in 3 months. :D

Thanks for doing it. Many will still not believe it. Silly.
 
Kerosene, gasoline, diesel, Jet A. All petroleum distillates. Came from the same barrel. They had to be *distilled* to be separated. I'm just an engineer and not a chemist. Even worked in a refinery for a number of years. But these products will never spontaneously separate.
 
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