'Unleaded' For G/A..??
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Andy RR
I had the good fortune to attend a GAMI forum with George Braly in Oshkosh on Friday. What TEL does is delay the start of fast burning of fuel at the spark event (thus making peak cylinder pressure occur where it's easier on the engine somewhere after TDC. Peak pressure is lower but occurs where it's mechanically more effective.) It also slows down the start of pinging because it takes a while for the pinging fire to get its act together in the presence of TEL. Once the fire gets going leaded fuel burns just as fast as unleaded. It's similar to burning large green wood piles. They take a bit to get going but once they do they burn hot and fast. This slow start is called "latency"
JABBA
Same forum. G100 UL is now approved as a drop-in fuel for all aircraft using 100 LL. Now all they need is for someone to start making it. Probable scenario is a state by state roll out. Greens or Govt will apply pressure and a state, perhaps California will outlaw unleaded. Before whenever a push came FAA pulled the safety card and said there was no known replacement. Well now there is.
All
I've seen the best and the worst over here. Innovation and lateral thinking in aviation everywhere. (They are too numerous list here.)
I've also seen Australia under Tony Abbot . The richest country in the world has beggars in the street (many ex military), a v--e--r--y s--l--o--w internet and in some populous places non existant and a crap hospital system. The wages are very low for people in semi and unskilled jobs and the unions have been legislated almost out of existence so there is no effective voice to fight unfair practices.
On a brighter note the Americans we've met have been very friendly and helpful.
Cheers RA
I had the good fortune to attend a GAMI forum with George Braly in Oshkosh on Friday. What TEL does is delay the start of fast burning of fuel at the spark event (thus making peak cylinder pressure occur where it's easier on the engine somewhere after TDC. Peak pressure is lower but occurs where it's mechanically more effective.) It also slows down the start of pinging because it takes a while for the pinging fire to get its act together in the presence of TEL. Once the fire gets going leaded fuel burns just as fast as unleaded. It's similar to burning large green wood piles. They take a bit to get going but once they do they burn hot and fast. This slow start is called "latency"
JABBA
Same forum. G100 UL is now approved as a drop-in fuel for all aircraft using 100 LL. Now all they need is for someone to start making it. Probable scenario is a state by state roll out. Greens or Govt will apply pressure and a state, perhaps California will outlaw unleaded. Before whenever a push came FAA pulled the safety card and said there was no known replacement. Well now there is.
All
I've seen the best and the worst over here. Innovation and lateral thinking in aviation everywhere. (They are too numerous list here.)
I've also seen Australia under Tony Abbot . The richest country in the world has beggars in the street (many ex military), a v--e--r--y s--l--o--w internet and in some populous places non existant and a crap hospital system. The wages are very low for people in semi and unskilled jobs and the unions have been legislated almost out of existence so there is no effective voice to fight unfair practices.
On a brighter note the Americans we've met have been very friendly and helpful.
Cheers RA
Akro, those figures you mention are for LL. Is that all you can buy these days? Serious question as I'm not a pilot. It was only a quick and dirty calculation to answer a question - production was the figure I found so I used it.
As to the 300,000t, it's quite probably a little dated - feel free to read the source paper or find alternate data
As to the 300,000t, it's quite probably a little dated - feel free to read the source paper or find alternate data
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rutan around you havent seen australia under tony abbot at all.
postscript.
if you mean that america is like australia will be under tony abbot then that is nonsense.
there is actually a study out there that shows that more people commit suicide under a liberal government than under labor governments. the study is a fact.
however I have had the experience of being in the welfare system under John Howard and under Labor. in my experience the welfare system actually worked better under John Howard than it has since. the government was managing the books and the money that the current government is wasting on interest payments was available to pay the welfare system.
the suicide statistics are because some people cannot handle the freedom to get out there and achieve and they feel abandoned. freedom isnt welcomed by some people.
you are sprouting bulls**t mate.
postscript.
if you mean that america is like australia will be under tony abbot then that is nonsense.
there is actually a study out there that shows that more people commit suicide under a liberal government than under labor governments. the study is a fact.
however I have had the experience of being in the welfare system under John Howard and under Labor. in my experience the welfare system actually worked better under John Howard than it has since. the government was managing the books and the money that the current government is wasting on interest payments was available to pay the welfare system.
the suicide statistics are because some people cannot handle the freedom to get out there and achieve and they feel abandoned. freedom isnt welcomed by some people.
you are sprouting bulls**t mate.
Last edited by dubbleyew eight; 5th Aug 2013 at 14:26.
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Latency: the time period between the ignition event and the formation of a flame front.
This is why differing fuels will have differing EGTs and CHTs when used in the same engine. The G100UL has a latency very, very close to 100LL so there will be no need to change the timing on the engines. It is a drop-in replacement for 100LL and can be mixed with 100LL during a transition to unleaded fuel. And, it requires no special handling as 100LL does.
Knowing the latency of the fuel is important in the calculation of where the ignition event is engineered so as to produce the peak combustion pressure at about 15-16dAFTDC where the con rod-crank geometry transfers the most mechanical power from the chemical reaction inside the combustion chamber to the crankshaft.
This is why differing fuels will have differing EGTs and CHTs when used in the same engine. The G100UL has a latency very, very close to 100LL so there will be no need to change the timing on the engines. It is a drop-in replacement for 100LL and can be mixed with 100LL during a transition to unleaded fuel. And, it requires no special handling as 100LL does.
Knowing the latency of the fuel is important in the calculation of where the ignition event is engineered so as to produce the peak combustion pressure at about 15-16dAFTDC where the con rod-crank geometry transfers the most mechanical power from the chemical reaction inside the combustion chamber to the crankshaft.
those figures you mention are for LL. Is that all you can buy these days?
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100 LL is the only AVGAS you have been able to buy for maybe 20 years. Suggest you research a little better.
Dexta
I'm stunned. Its been a while since I landed at Parafield, but at Adelaide International I only have the option of 100LL. Same at Port Pirie, Port Augusta, Whyalla, Olympic Dam, Coober Pedy, Murray Bridge, Waikerie, William Creek, Ceduna, Mt Gambier, Kangaroo Island. I think that's the total of My SA experience.
I'm stunned. Its been a while since I landed at Parafield, but at Adelaide International I only have the option of 100LL. Same at Port Pirie, Port Augusta, Whyalla, Olympic Dam, Coober Pedy, Murray Bridge, Waikerie, William Creek, Ceduna, Mt Gambier, Kangaroo Island. I think that's the total of My SA experience.
It's interesting to review the AVGAS MSDSs on BP Australia's website.
There are three.
One of them is for '100', and it says the colour is 'green'.
The others are for '100LL', and they say the colour is 'blue' (but each of these has different benzene levels than the other).
Perhaps BPA is still producing green (as well as LL blue).
There are three.
One of them is for '100', and it says the colour is 'green'.
The others are for '100LL', and they say the colour is 'blue' (but each of these has different benzene levels than the other).
Perhaps BPA is still producing green (as well as LL blue).
I am getting confused with the terms in this discussion. Latency? Time between spark and start of flame front????
See if I have this right, in a perfect stoiciometric mixture of avgas and air in a confined space at normal ATM. A spark is introduced resulting in a flame front propagating evenly in all directions at about the local speed of sound...340m/s.
if I increase the pressure in said closed vessel to a point where said stoic mixture ignition event turns from a nice steady 340m/s to a point where mixture begins to spontaneously ignite in front of the flame front increasing pressure and causing a supersonic 2000m/s shock wave induced detonation.
...adding TEL to this mixture keeps the stoic mixture happy to keep burning nicely at said higher pressure....where does latency come in? The ignition event occurs the flame propagates at the instant of the spark.
If you change the stoic mixture to one of NitroMethane and air under even higher compression...the flame front is happy to burn along at a sedate 100m/s...hence the need to run three times the advance in spark timing. 60+degrees advance....latency?...or just where you have to ignite the stuff to get peak pressure at the right point ATDC?
Happy for a link on "latency"
See if I have this right, in a perfect stoiciometric mixture of avgas and air in a confined space at normal ATM. A spark is introduced resulting in a flame front propagating evenly in all directions at about the local speed of sound...340m/s.
if I increase the pressure in said closed vessel to a point where said stoic mixture ignition event turns from a nice steady 340m/s to a point where mixture begins to spontaneously ignite in front of the flame front increasing pressure and causing a supersonic 2000m/s shock wave induced detonation.
...adding TEL to this mixture keeps the stoic mixture happy to keep burning nicely at said higher pressure....where does latency come in? The ignition event occurs the flame propagates at the instant of the spark.
If you change the stoic mixture to one of NitroMethane and air under even higher compression...the flame front is happy to burn along at a sedate 100m/s...hence the need to run three times the advance in spark timing. 60+degrees advance....latency?...or just where you have to ignite the stuff to get peak pressure at the right point ATDC?
Happy for a link on "latency"
As Walter Atkinson said, latency "is the time it takes for the flame front to become organized after the spark event. ... After the flame front is organized the flame front moves at the same speed with or without the lead." 
It makes sense that way...but....TEL keeps acting as a chemicals reaction within the flame front to "steady" the reaction..or, at least the way I think it goes.
100/130 will still detonate in a high compression, highly loaded up performance engine....thats when you need to think about changing to burning alcohol instead of drinking it....sorry for the thread drift.
100/130 will still detonate in a high compression, highly loaded up performance engine....thats when you need to think about changing to burning alcohol instead of drinking it....sorry for the thread drift.
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Oz
Normal flame front is no where near the speed of sound. A quick calculation will show you that even if you don't believe the data produced by others. Based on a IO 520 engine with a 4" stroke and a 5.25" bore operating at 2400 RPM and set to fire at 22 degrees of crank angle BTDC so the fuel burn finishes around 14 degrees ATDC. the following can be calculated.
The fuel burn lasts for 36 degrees of crank rotation. At 2400 RPM the crank rotates 40 times / second and one rotation (360 degrees ) takes 0.025 seconds. This means the fuel burn takes 0.0025 seconds. With both plugs firing each flame front only has to travel about half the the piston/ bore diameter ie 2.625" or 0.06667 metres .Using only my I- phone here on the shores of Lake Superior I make that 26. 67 m/sec or 96 kilometers/hr average.
Remember also that even in the best of engines the fuel air mix is far from homogenous. Pinging starts randomly in places where the temp and mixture most favor auto ignition. The TEL delays any auto ignition event from getting properly started . If an event does get going properly no amount of TEL will stop it.
Cheers RA
Normal flame front is no where near the speed of sound. A quick calculation will show you that even if you don't believe the data produced by others. Based on a IO 520 engine with a 4" stroke and a 5.25" bore operating at 2400 RPM and set to fire at 22 degrees of crank angle BTDC so the fuel burn finishes around 14 degrees ATDC. the following can be calculated.
The fuel burn lasts for 36 degrees of crank rotation. At 2400 RPM the crank rotates 40 times / second and one rotation (360 degrees ) takes 0.025 seconds. This means the fuel burn takes 0.0025 seconds. With both plugs firing each flame front only has to travel about half the the piston/ bore diameter ie 2.625" or 0.06667 metres .Using only my I- phone here on the shores of Lake Superior I make that 26. 67 m/sec or 96 kilometers/hr average.
Remember also that even in the best of engines the fuel air mix is far from homogenous. Pinging starts randomly in places where the temp and mixture most favor auto ignition. The TEL delays any auto ignition event from getting properly started . If an event does get going properly no amount of TEL will stop it.
Cheers RA
OK, seems there is somewhere from 36 to 47 tonnes annual use of lead in Oz avgas. For the exercise perhaps we can go worst case and use 47 tonnes.
What happens to it ? i guess it does its job and flows thru the engine and out to the atmosphere.
I see a comment on the lead accumulating in the engine oil. What percentage of the 47 tonnes of lead get changed out via the 25 hour oil changes. 5%, 20%, 50% ??? ...lets say two tonnes stay in the oil.
When the remaining 45 tonnes makes it out the exorst pipe, do this 'emitted' lead do the dust trick and float around for months at a time finnally settling somewhere mid Pacific ocean. Or do the heavy lead just fall to the ground in a matter of days ? Probably a bit of both.
Lets keep it a really bad worst case. Forty tonnes of lead gets put out over Oz. How bigs Oz... about 8,000,000 square kilometres. Where do avgas burning aircraft fly in Oz - from servicing remote Aboriginal communities to doing mail runs around regional centres to the local flying school. Just about every where. So its fairly evenly spread, though lead do accumulate, or so they say.
Now, i got straight F's in maths for the short time i were at school so yer better check me. Lets see, 45,000kg divided by eight million square km = .005625 Hmmm... bit hard to comprehend that amount over a square km, perhaps we need to work it to a square metre: .005625 divided by 1,000,000 =
Fleck ! me calculator caint work it out. Not enuf decimal place zero's.
...Anyway, there is an easier way to think about it. Next time yer open the box containing the latest wiz bang gadget from China - take a wiff, yer probably just got more lead inta yer in one go then a life time of sniffing avgas will do for ya.
Lead in avgas - Much ado about nothing...
.
What happens to it ? i guess it does its job and flows thru the engine and out to the atmosphere.
I see a comment on the lead accumulating in the engine oil. What percentage of the 47 tonnes of lead get changed out via the 25 hour oil changes. 5%, 20%, 50% ??? ...lets say two tonnes stay in the oil.
When the remaining 45 tonnes makes it out the exorst pipe, do this 'emitted' lead do the dust trick and float around for months at a time finnally settling somewhere mid Pacific ocean. Or do the heavy lead just fall to the ground in a matter of days ? Probably a bit of both.
Lets keep it a really bad worst case. Forty tonnes of lead gets put out over Oz. How bigs Oz... about 8,000,000 square kilometres. Where do avgas burning aircraft fly in Oz - from servicing remote Aboriginal communities to doing mail runs around regional centres to the local flying school. Just about every where. So its fairly evenly spread, though lead do accumulate, or so they say.
Now, i got straight F's in maths for the short time i were at school so yer better check me. Lets see, 45,000kg divided by eight million square km = .005625 Hmmm... bit hard to comprehend that amount over a square km, perhaps we need to work it to a square metre: .005625 divided by 1,000,000 =
Fleck ! me calculator caint work it out. Not enuf decimal place zero's. ...Anyway, there is an easier way to think about it. Next time yer open the box containing the latest wiz bang gadget from China - take a wiff, yer probably just got more lead inta yer in one go then a life time of sniffing avgas will do for ya.
Lead in avgas - Much ado about nothing...
.
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you can look at lead dispersal another way.
if I take 23litres of avgas that is 23,000cc of avgas. I then spread it over 222km it ends up being a thread about 12lb fishing line. (I did work it out once quite accurately, but I forget the specifics) so of that 5% is lead.
5/8ths of stuff all really so go flying.
if I take 23litres of avgas that is 23,000cc of avgas. I then spread it over 222km it ends up being a thread about 12lb fishing line. (I did work it out once quite accurately, but I forget the specifics) so of that 5% is lead.
5/8ths of stuff all really so go flying.
Next time yer open the box containing the latest wiz bang gadget from China - take a wiff, yer probably just got more lead inta yer in one go then a life time of sniffing avgas will do for ya.
Lead from car batteries / wheel weights has one of the highest recycling rate of any material (presumably behind metals like gold & silver!!).