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how can you tell if avgas is ok?


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Put about 50ml in an old 5 litre can. Take it down the back of the yard. Light a cigaratte on the end of a long stick & while hiding behind something solid put the lit cigarette in the top of the can. If there is a huge bang & the can pretty much disappears the fuel is still good. chill_out.gif.cee4903a35751abb602feb480645ccbb.gifbomb.gif.8dfedc171d37efc22ba0dd32e933ffc0.gifsplat.gif.4fe5615d47cdda8649f5910181ed23f2.gif

 

 

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t

 

Put about 50ml in an old 5 litre can. Take it down the back of the yard. Light a cigaratte on the end of a long stick & while hiding behind something solid put the lit cigarette in the top of the can. If there is a huge bang & the can pretty much disappears the fuel is still good. chill_out.gif.cee4903a35751abb602feb480645ccbb.gifbomb.gif.8dfedc171d37efc22ba0dd32e933ffc0.gifsplat.gif.4fe5615d47cdda8649f5910181ed23f2.gif

i thought you need an open flame or spark ?

 

 

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Depends on the ambient air temperature. Flash point is a very low -40C. This is the temperature at which the vapour will cease to burn by itself. The vapour pressure will be about zero at -40C and increase to atmospheric pressure at the boiling point. Auto ignition temperature is 450C for 100LL so the cigarette would need to be that hot at the tip. The vapour will stratify in the can and vapour will leak out. On a cold day the vapour will be correct for a "bang" closer to the bottom. On a hot day the air/vapour mixture will be correct near or outside the top of the can. The range if flammability is quite narrow when compared to hydrogen gas.

 

The cigarette in question needs to burn to keep hot and putting it in an air fuel vapour mixture will starve then cool it. You see the old western movies where the cowboy tokes on a big FAT cigar a few times before applying it to the fuse string for dramatic effect. Nobody in their right mind would drop a lit cigar into a tin of petrol. Waste of a cigar.

 

There is a very real chance the cigarette will go out before the bang because there just isn't enough of it that is hot, invalidating the experimental result. This is why petrol chemists use a "b0mb calorimeter" and a bucket of water.

 

Seriously. DON'T try this at home.

 

Best I can offer is add a 50/50 mixture of the sample fuel and PURE water in a fuel tester. If the sample separates cleanly and still reads 50/50 by volume it is good to go. Avgas stores for years with a vent to the atmosphere and regularly separates out water at the bottom of its container by design of the chemistry. Just don't agitate the container and ensure a good in line filter does catch the water by the effect of gravity. The last 10% of any fuel container will have some contamination including the tanks in your plane.

 

Caveat. If you follow this advice I am not responsible for the result.

 

 

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I cant remember where I read it, but it was a "real source" not a forum posting, and that source said AVGAS is fine for 12 months. Where as I believe 98 Octane Mogas may well be fine for 12 minutes or 12 metres which ever occurs first.......

 

Back to Avgas...the interesting thing with what we do is that we don't fly to empty and refill with a completely new batch, rather we fly and top up, fly and top up...repeat for as long as you can.....some of the fuel must be very old in the wing tanks.....

 

Andy

 

 

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are you saying don't try a sample of fuel to water .,or don't try and set up a system with drums and water drains?

 

sorry , I'm a bit thick sometimes !

 

there's no water in the drums ,and our ambient humidity here in Hawker averages 4%. the dry old desert,

 

but hot in the summer !

 

mike

 

edit ::: I get it , don't try the cigar thingy.

 

told you I was a bit thick ( generally on Saturdays )

 

 

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Yes you can try mixing a sample of fuel and pure water, shaking it then letting it settle for maybe 30 minutes. Look at where the water meets the petrol and see it it's a neat line. If not, the fuel is toxic waste. All of it. A "GATS" jar will help you separate the fuel and re-use the good part.

 

My ground instructor told me fuel contamination happens a lot on the coast when a plane is parked outside in the rain overnight. All tanks breathe in the moisture by the effect of the fuel and air inside cooling and getting smaller. When it's raining an aircraft tank can breathe in a lot of moisture - we are talking 100 mL for a 100 gallon wing tank.

 

Pilot comes along, sumps out the now liquid water until the fuel runs clean and that's it.

 

Gravity at work. If you're in a desert, the fuel will most likely last forever.

 

 

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Club aircraft used to be filled to top before going into the hangar overnight to reduce the amount of moisture that would be available from the air in the tank. This can't be done where a plane may be required to be operated with less than a full fuel load, which is often the case with charter etc. Highest moisture is in tropics, as cold air doesn't carry much even at saturation..The poles are the driest places on earth. Nev

 

 

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Back to Avgas...the interesting thing with what we do is that we don't fly to empty and refill with a completely new batch, rather we fly and top up, fly and top up...repeat for as long as you can.....some of the fuel must be very old in the wing tanks.....

Andy

The remaining old fuel will mix completely with the new each time you fill so the amount of "oldest" fuel remaining will be repeatedly diluted very quickly until negligible.

 

For example : Hold 120 litres of fresh fuel starting with empty tanks, use 60 and refill, amount of oldest fuel remaining 60 litres ie 50%

 

Use 60 and refill . Amount of oldest fuel remaining is 30 litres (60 x 50%)

 

Use 60 and refill. Amount of oldest fuel remaining is 15 litres, etc etc

 

After 5 fills the oldest fuel is essentially gone.

 

The moral of the story is to fly a lot!

 

Kaz

 

 

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so I'm assuming that avgas remains usable unless it has been contaminated with water ?

 

I'm also assuming that there is no degradation of the avgas itself ?

 

mike

 

 

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so I'm assuming that avgas remains usable unless it has been contaminated with water ?I'm also assuming that there is no degradation of the avgas itself ?

mike

That's what you originally asked wasn't it Mike? Before the thread side slipped.....

My understanding is that avgas lasts and lasts and lasts since it is made out of petrol and lead - no aromatics or chemicals that can evaporate off leaving low octane stuff. I know years ago I was given a 200 litre drum of avgas (130) athat was a couple of years old and it seemed to work fine. Laurie

 

BTW, the unleaded I use is Shell 95.

 

 

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I've had a drum of a gas for 10 months (opened) . was wondering if it's still ok to use??smells & looks ok

mike

Hi Mike,

 

There's a very good chance it will be ok... However there is a chance it won't be. Stored in a sealed container in correct conditions 10 months won't be a problem, but when it's exposed to the atmospher many things can (and do) go wrong.

 

Personally I would find another use for it and buy some new fuel.... This will be a lot cheaper than testing or doing some damage to an engine or possibly worse!

 

Fresh is always best.

 

Cheers

 

Vev

 

 

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Hi Mike,There's a very good chance it will be ok... However there is a chance it won't be. Stored in a sealed container in correct conditions 10 months won't be a problem, but when it's exposed to the atmospher many things can (and do) go wrong.

 

Personally I would find another use for it and buy some new fuel.... This will be a lot cheaper than testing or doing some damage to an engine or possibly worse!

 

Fresh is always best.

 

Cheers

 

Vev

Yes Vev , that what I'll probably do ,

 

The old landrover runs well on it . But I tried mixing up some up for the chain saw & mower but I couldn't get them to start , that's what made me suspicious .

 

The avocet runs alright .

 

It's been sealed and doesn't smell like Rotten egg gas , as I have heard .

 

I don't really want to run the water cooled heads with avgas in the plane

 

( runs pretty cool , 95 deg ish .)

 

I had planned to start running 95 ulp and shandy a 25% mix of the avgas

 

Thanks for your reply

 

Mike

 

 

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I would say you don't need the avgas at all with LCH, if the valves and seats are of a suitable material. There is always a risk with lead that a deposit will build up on the seats with a cool running head, if the Rotax's are any guide. Other's may comment. Nev

 

 

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Yes Vev , that what I'll probably do ,I had planned to start running 95 ulp and shandy a 25% mix of the avgas

 

Mike

Mike

 

You may already be aware, but if not (for your info) JSL 007-4, warns against using shandys

 

  • This practice is unsafe. Jabiru Aircraft do not endorse it and may void any warranty of an engine or aircraft which has been operated using such a fuel.
     
     
    A full explanation is contained in the JSL.
    I have no expertise in the area - just drawing your attention to the JSL, incase you haven't seen it.
     
     

 

 

 

 

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Thanks F/M, I think I'll use it in the old land rovers .Thanks for all the info every one .

Cheers mike

They will be reminiscing the old days of 'Super'

 

 

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