100LL

[Inverted25]

So I was reading a article on AOPA about 100LL being phased out eventually. I was thinking about what impact this would have on private owners. Being a half owner of a Cherokee 140 with my uncle I was thinking about how this would effect us. With the O-320 you can use autofuel which we do so it wouldn't effect us any really. Although they say you should run AvGas everynow and then through the engine. Basically everyone with low compression engines would be ok because they could use autofuel in their airplanes. But what about all the high compression guys out there. If it would require a change of cylinders on airplanes to handle whatever new fuel they come up with how many people do you think would just say screw it and sell or scrap their airplane at that point. And overall how many planes do you think would be grounded for life because people would just abandon them. I think they number would be staggering if the conversion was expensive.

 

[mshunter]

But what about all the high compression guys out there.

This is why engineers are trying to find a drop in fuel. The basic GA airplanes will be fine with a lower octane fuel. But Higher horse power/turbocharged airplanes is what the issue seems to be with right now.

And overall how many planes do you think would be grounded for life because people would just abandon them. I think they number would be staggering if the conversion was expensive.

If they can't figure out how to deal with the issue, I think a lot of airplanes won't necessarily be scraped, but they will have to have some sort of performance robbing mod done. I'm going on a bike ride with my sone right now. I'll post more when I get back.

 

[mshunter]

Read this. It's a very good article about detonation and how higher octanes help reduce it.


http://www.motorcycle.com/how-to/wrenching-with-robchemical-soup-the-mystery-of-detonation-3420.html

 

[ackeight]

There are a handfull of 100UL ideas out there. Personally I think this idea will work better than the 96UL ideas, but will take a little longer to approve. The good thing about UL is that we can use normal piplines instead of using only dedicated trucks to deliver, meaning the prices should actually go down.

 

[z987k]

I wouldn't mind going back to multiple octanes. 100UL is not impossible to produce by any means, in fact it currently is for cars. It would be expensive, and for the rest of GA that doesn't need it, lower will work.

Then in the meantime, switch over to diesel(turbo) because it's a better engine for this application in every conceivable way. In fact screw phasing out 100LL, leave it for legacy aircraft and go all diesel. It's not like the lead is causing any meaningful pollution in the very low quantities used.

 

[USMCmech]

75% of the airplanes flying today are running engines that were designed for 80/87 octane. These are your basic 172s, arrows, old mooneys, ect. 100LL is overkill for these motors, they will be just fine on whatever fuel the FAA aproves in the future (94UL, 100UL, mogas, ect).

It's the other 1/4 of the fleet (mainly big turbocharged engines) that is running behind engines that NEED the higher antiknock additive. Furthermore, these guys buy about 75% of the total fuel sold nationwide.

 

[MikeD]

75% of the airplanes flying today are running engines that were designed for 80/87 octane. These are your basic 172s, arrows, old mooneys, ect. 100LL is overkill for these motors, they will be just fine on whatever fuel the FAA aproves in the future (94UL, 100UL, mogas, ect).

It's the other 1/4 of the fleet (mainly big turbocharged engines) that is running behind engines that NEED the higher antiknock additive. Furthermore, these guys buy about 75% of the total fuel sold nationwide.

Yes. Dad's '76 182 was designed for 80/87 and ran that all the way up to their getting rid of the red stuff.

How did the large radials that needed 115/145 purple stuff, how did they get them to run efficiently on 100LL? Anti-detonation additives mainly?

 

[USMCmech]

How did the large radials that needed 115/145 purple stuff, how did they get them to run efficiently on 100LL? Anti-detonation additives mainly?

I'm not real familiar with warbirds, but my understanding is they adjusted the timing some and run at reduced power settings.

They brew up some special 115/145 purple fuel for Reno. I don't even want to think about what that costs per gallon.

 

[MikeD]

I'm not real familiar with warbirds, but my understanding is they adjusted the timing some and run at reduced power settings.

They brew up some special 115/145 purple fuel for Reno. I don't even want to think about what that costs per gallon.

I know some of the Connie's and DC-7s had tanks for Anti Detonation Injection (ADI) fluid, which I believe was 50/50 methanol and water. But they ran that along with the 115/145 they carried. I don't know if something else was used to "make up" for the loss of octane with 100/130 green and worse, with 100LL

 

[mshunter]

The fact is, we still need 100LL to support the economy. Look at the majority of small cargo/small charter stuff. What would AmFlight/FLX/Airnet do?

 

[USMCmech]

The fact is, we still need 100LL to support the economy. Look at the majority of small cargo/small charter stuff. What would AmFlight/FLX/Airnet do?

That's the rub, the guys who buy most of the fuel NEED 100LL.

I think that 94UL is probably the best bet. Blanket approval for any engine that was designed for 80/87. With electronic ignition STCs for the big twins that really need the 100LL.

 

[msmspilot]

Yes. Dad's '76 182 was designed for 80/87 and ran that all the way up to their getting rid of the red stuff.

How did the large radials that needed 115/145 purple stuff, how did they get them to run efficiently on 100LL? Anti-detonation additives mainly?

The Commemorative Air Force has a Sea Fury in Memphis. They keep barrels of the purple avgas for it.

 

[mshunter]

That's the rub, the guys who buy most of the fuel NEED 100LL.

I think that 94UL is probably the best bet. Blanket approval for any engine that was designed for 80/87. With electronic ignition STCs for the big twins that really need the 100LL.

For a company like AmFlight that could BK them. And with how thin tha margins are for FLX/Airnet, with how they have been cutting costs, I'm not sure how they would survive. The thin that bothers me is how low the lead is in the enviroment, even at airports. We had a similar discusion recently and I found a survey that the EPA did at SMO. The levels of lead wer less at the run-up area then they were a mile away from the airport in the city. It's a false premis that 100LL is killing baby seals.

 

[z987k]

For a company like AmFlight that could BK them. And with how thin tha margins are for FLX/Airnet, with how they have been cutting costs, I'm not sure how they would survive. The thin that bothers me is how low the lead is in the enviroment, even at airports. We had a similar discusion recently and I found a survey that the EPA did at SMO. The levels of lead wer less at the run-up area then they were a mile away from the airport in the city. It's a false premis that 100LL is killing baby seals.

This is true. The amount of lead emitted from burning 100LL is not enough to cause harm to anything. We've solving a problem that doesn't actually exist.

 

[Richman]

Yes. Dad's '76 182 was designed for 80/87 and ran that all the way up to their getting rid of the red stuff.

How did the large radials that needed 115/145 purple stuff, how did they get them to run efficiently on 100LL? Anti-detonation additives mainly?

Reduced manifold pressure. When we ran a big old Sikorsky S-58 with a big-old R2800 in the nose, we had to really pull back the power we pulled when we ran 100LL.

But to address some of the other issues.

100LL is the huge, pink elephant in the room for GA. This is huge.

A couple of points:

1) 100 octane from your local tuner shop is in NO WAY equivilent to 100 octane 100LL. Beyond all the nit noid details, like vapor pressure, stability, etc, the way octane is computed is really different.

The label you see on your favorite gas station is the AKI, or anti knock index, which is an average of reseach octane number and the motor octane number.

Avgas octane, on the other hand usually has two numbers: An aviation rich, and an aviation lean octane (which is close to the motor octane number). This is why, in general, you saw Avgas have two ratings in the past (eg 100/130, 115/145, 80/87, etc).

If you tested 100LL to the same standard as autogas, you'd get a AKI of around 115. Avgas also has an extremely tight specification...even min spec avgas is an order of magnitude tigher than autogas.

2) Which brings me to my next point. Autogas is crap. Really. Thanks to ethanol, gas producers have been able to relax their specs on autogas. While ethanol is a really, really crappy fuel by itself, it also has a VERY high octane rating. This allows gas producers to produce really crappy petrol feedstock, and then artificially elevate the octane with up to %10 ethanol.

100LL's days are numbered, and not because of the tree huggers. Studies admit that the lead output from GA is practically indistinguishable from background "noise" in the envrionment.

But 100LL sales have been decreasing year over year. It requires a completely segregated production and distribution system. And there is exactly 1 (one) plant in the entire world that produces tetra-ethyl lead, the stuff that gives 100LL (and all leaded fuels) its awesome anti-detenation properties. If that plant goes blooey, its all over but the shouting.

Economics will kill 100LL before the greenies do.

94UL is not an answer. Even with electronic ignition, just about every engine that requires it will have to operate at reduced power. Take that POH and throw it out the window while you wait for Cessna, Beech and Piper to recertify every aircraft and variant with new performance numbers. For defunct builders, that wait will be forever.

Think this just affects turbocharged engines? Wrong. Contiental IO-360s (Mooneys), O-470U (182s) and IO-520s (Bonanzas), certain variants of Lycomming O-540s (Dakotas, Saratogas) and just about all of the restart Cessnas have high compression cylinders (anything around 8.5:1) and require 100 octane as a minimum.

Even for older aircraft, you can toss that Autogas STC in the trash. Most, if not all of the autogas STCs mandate autogas with NO ethanol. Try to find autogas without it today. Remember economics above? Ethanol lets the refiners produce crappier gas.

So, what can you do? Hope is lost, right?

Well, there are ways to make a nice, tight 100 octane avgas that is unleaded. First, you start with a very decent gas production, with tight specs. That gets you to 94 octane.

Then you can add MTBE to it. That will get you to 100. BUT MTBE is really, really unpopular with the bunny lovers, since it has a habit of getting into the ground water REALLY easily and it stinks to high heaven when it does.

Or you can add ETBE to it. Not quite the same as MTBE, and not near as stinky. Also not quite as effective. I am pretty sure this is how the Sweeds get their no-lead AvGas to 96 octane. But if I recall from their website, even their 96 octane won't work in high compression engines like later model O-470s and O-540s.

Or you can add some funky organics to the gas, like benzene or some of the longer chain alcohols like butanol (4 carbons vs 2 on ethanol). Benzene is a carcinogen, so that will never happen, but some of the other stuff MAY. You can pull some of this stuff out of plant stock (thus you get the Swift Fuel) or you can synthesize it from other organics that come out of petrol feedstock (the G1000 route).

But if you allow me to put on my tin foil hat for a couple of sentences. A LOT of people wouldn't mind seeing GA go away. The governement, the TSA, homeowners and building developers (airports make GREAT housing developments...already graded) and the bunny mafia are only a few. The big BIG money has a vested interest in seeing GA become nothing larger than a oversized ultralight.

Getting rid of 100LL is a great way to do it. Diesel engines are a nice thought, but that's all it is. You going to refit a 50k engine into an airframe worth 50k?

With a huge amount of the fleet parked for no gas. Services will dry up. Whats left will be cost prohibitive. It will become a death spiral that GA won't recover from, at least not in the form we know of.

Richman

 

[Patrick]

I wouldn't mind going back to multiple octanes. 100UL is not impossible to produce by any means, in fact it currently is for cars. It would be expensive, and for the rest of GA that doesn't need it, lower will work.

Then in the meantime, switch over to diesel(turbo) because it's a better engine for this application in every conceivable way. In fact screw phasing out 100LL, leave it for legacy aircraft and go all diesel. It's not like the lead is causing any meaningful pollution in the very low quantities used.

If only the powers that be understood this.....

 

[z987k]

if a 8.5:1 engine needs 100 octane or 115 r+m/2 as you said, then something is seriously wrong with that engine design. Did they put pointy carbon spikes in the combustion chamber from the factory?
If vehicle manufacturers can produce engines that run on 87-93pump at 11:1. I think it's reasonable that an aircraft engine can run on 100 at 8.5:1.

 

[z987k]

If only the powers that be understood this.....

TDI's in aircraft are awesome. 200hp, 25,000ft ss, 180kts+ ~7gph... uh yes please.

 

[Patrick]

Reduced manifold pressure. When we ran a big old Sikorsky S-58 with a big-old R2800 in the nose, we had to really pull back the power we pulled when we ran 100LL.

But to address some of the other issues.

100LL is the huge, pink elephant in the room for GA. This is huge.

A couple of points:

1) 100 octane from your local tuner shop is in NO WAY equivilent to 100 octane 100LL. Beyond all the nit noid details, like vapor pressure, stability, etc, the way octane is computed is really different.

The label you see on your favorite gas station is the AKI, or anti knock index, which is an average of reseach octane number and the motor octane number.

Avgas octane, on the other hand usually has two numbers: An aviation rich, and an aviation lean octane (which is close to the motor octane number). This is why, in general, you saw Avgas have two ratings in the past (eg 100/130, 115/145, 80/87, etc).

If you tested 100LL to the same standard as autogas, you'd get a AKI of around 115. Avgas also has an extremely tight specification...even min spec avgas is an order of magnitude tigher than autogas.

2) Which brings me to my next point. Autogas is crap. Really. Thanks to ethanol, gas producers have been able to relax their specs on autogas. While ethanol is a really, really crappy fuel by itself, it also has a VERY high octane rating. This allows gas producers to produce really crappy petrol feedstock, and then artificially elevate the octane with up to %10 ethanol.

100LL's days are numbered, and not because of the tree huggers. Studies admit that the lead output from GA is practically indistinguishable from background "noise" in the envrionment.

But 100LL sales have been decreasing year over year. It requires a completely segregated production and distribution system. And there is exactly 1 (one) plant in the entire world that produces tetra-ethyl lead, the stuff that gives 100LL (and all leaded fuels) its awesome anti-detenation properties. If that plant goes blooey, its all over but the shouting.

Economics will kill 100LL before the greenies do.

94UL is not an answer. Even with electronic ignition, just about every engine that requires it will have to operate at reduced power. Take that POH and throw it out the window while you wait for Cessna, Beech and Piper to recertify every aircraft and variant with new performance numbers. For defunct builders, that wait will be forever.

Think this just affects turbocharged engines? Wrong. Contiental IO-360s (Mooneys), O-470U (182s) and IO-520s (Bonanzas), certain variants of Lycomming O-540s (Dakotas, Saratogas) and just about all of the restart Cessnas have high compression cylinders (anything around 8.5:1) and require 100 octane as a minimum.

Even for older aircraft, you can toss that Autogas STC in the trash. Most, if not all of the autogas STCs mandate autogas with NO ethanol. Try to find autogas without it today. Remember economics above? Ethanol lets the refiners produce crappier gas.

So, what can you do? Hope is lost, right?

Well, there are ways to make a nice, tight 100 octane avgas that is unleaded. First, you start with a very decent gas production, with tight specs. That gets you to 94 octane.

Then you can add MTBE to it. That will get you to 100. BUT MTBE is really, really unpopular with the bunny lovers, since it has a habit of getting into the ground water REALLY easily and it stinks to high heaven when it does.

Or you can add ETBE to it. Not quite the same as MTBE, and not near as stinky. Also not quite as effective. I am pretty sure this is how the Sweeds get their no-lead AvGas to 96 octane. But if I recall from their website, even their 96 octane won't work in high compression engines like later model O-470s and O-540s.

Or you can add some funky organics to the gas, like benzene or some of the longer chain alcohols like butanol (4 carbons vs 2 on ethanol). Benzene is a carcinogen, so that will never happen, but some of the other stuff MAY. You can pull some of this stuff out of plant stock (thus you get the Swift Fuel) or you can synthesize it from other organics that come out of petrol feedstock (the G1000 route).

But if you allow me to put on my tin foil hat for a couple of sentences. A LOT of people wouldn't mind seeing GA go away. The governement, the TSA, homeowners and building developers (airports make GREAT housing developments...already graded) and the bunny mafia are only a few. The big BIG money has a vested interest in seeing GA become nothing larger than a oversized ultralight.

Getting rid of 100LL is a great way to do it. Diesel engines are a nice thought, but that's all it is. You going to refit a 50k engine into an airframe worth 50k?

With a huge amount of the fleet parked for no gas. Services will dry up. Whats left will be cost prohibitive. It will become a death spiral that GA won't recover from, at least not in the form we know of.

Richman

Excellent post, and all absolutely correct information, except for this. 8.5:1 is absolutely NOT "high compression." My Porsche street car runs 12.8:1 and is absolutely happy on junk pump gas. And yes, I drive it hard The race car runs 12.5:1 on 100 octane (R+M/2) unleaded race gas, and it stays wide open all afternoon and doesn't blow up. Plenty of tuner kids are running 25 lbs of boost on Supras and making 600HP out of 3 liters (in cubic inches that's only 190 cubes kids) at the wheels, and their motors don't blow up. The secret? Modern engine design. Modern engine management. Which means: no magnetos, and no manual fuel control.

If you just installed modern engine management onto these old motors they'd run all day long on 94UL (and yes, even the big "cool" stuff like a TSIO-550), albeit likely making a bit less power at "full power" (due to the brain pulling timing and adding enrichment fuel to control detonation).

I do agree, however, that all leaded fuel's days are numbered due to economics, not the greenies.

 

[Patrick]

if a 8.5:1 engine needs 100 octane or 115 r+m/2 as you said, then something is seriously wrong with that engine design. Did they put pointy carbon spikes in the combustion chamber from the factory?
If vehicle manufacturers can produce engines that run on 87-93pump at 11:1. I think it's reasonable that an aircraft engine can run on 100 at 8.5:1.

There is. It's called 1930's engine design. Look at where cars were at way back when, and then wonder why you still have the same thing powering your airplane today.