'Unleaded' For G/A..??
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Andy, it could be either, but only one requires no modifications and is drop in (fleet wide). One is able to be produced readily at just about any decent refinery the other is not.
Time will tell but which horse would you put money on?
Time will tell but which horse would you put money on?
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Andy, I was being rather broad sweeping in my statement and not singling out any particular option for special treatment, however over the last 10 years there have been hundreds of fuel options tested by the FAA. Very few came even close and then the issue is that for any fuel to be a drop in replacement without hardware changes it needs to be not just an equivalent octane rating. A lot more to it.
What is critical besides the required performance parameters and material compatibility is that you can swap from one to the other and blend them in any ratio in the wing or the FBO tanks. Anything else than complete 'blendability' with existing 100LL is not going to work for the period of time it takes to change over. This is no easy task, and if it was easy, it would have been done long ago.
In summary any replacement for 100LL needs to be;
1. MON99.6 and supercharge rich rating of 130, or higher.
2. RVP of 5.5-7.1 PSI
3. Must not require modification to the aircraft/engine (read certification)
4. Must not have a derating of HP, most twins would be grounded if so
5. Needs to produced in sufficient volume to be rolled out across the USA, Canada, Brazil, Australia, Europe etc.
There are lots of other complex issues. In my opinion, so far only one ticks all the boxes, and that is based on a lot of recent research, more than I ever did at Uni
My head hurts!
What is critical besides the required performance parameters and material compatibility is that you can swap from one to the other and blend them in any ratio in the wing or the FBO tanks. Anything else than complete 'blendability' with existing 100LL is not going to work for the period of time it takes to change over. This is no easy task, and if it was easy, it would have been done long ago.
In summary any replacement for 100LL needs to be;
1. MON99.6 and supercharge rich rating of 130, or higher.
2. RVP of 5.5-7.1 PSI
3. Must not require modification to the aircraft/engine (read certification)
4. Must not have a derating of HP, most twins would be grounded if so
5. Needs to produced in sufficient volume to be rolled out across the USA, Canada, Brazil, Australia, Europe etc.
There are lots of other complex issues. In my opinion, so far only one ticks all the boxes, and that is based on a lot of recent research, more than I ever did at Uni
My head hurts!
fuel options tested by the FAA.
There is an existing alternative to AVGAS for a large number of aircraft. Its called MOGAS. It seems to me that most carburetted single engined aircraft have a MOGAS STC available:
Petersen Aviation | Auto Fuel STC
If we really wanted to get at the root of this issue, we'd look to the regulators that make transporting, storing and dispensing fuel for aviation many times harder than fuel for other vehicles.
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Akro, I beg to differ on this one. FAA at there engine test facility are the ones who had done significant testing, the last lot was about 30 odd of the leading brews over the last ten years.
ASTM are an industry body or association if you will. Big difference to what they actually do to what you are suggesting.
There may be MOAGS options for some, but the big users are the big engines and they can't have it. Its that simple. Two fuels on the field will not happen, or not very often.
ASTM are an industry body or association if you will. Big difference to what they actually do to what you are suggesting.
There may be MOAGS options for some, but the big users are the big engines and they can't have it. Its that simple. Two fuels on the field will not happen, or not very often.
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***If we really wanted to get at the root of this issue, we'd look to the regulators that make transporting, storing and dispensing fuel for aviation many times harder than fuel for other vehicles.***
You cannot mix AVgas and other fuels because of the lead. THAT is the reason it costs more to transport.
BTW, if we rely on Mogas to be the replacement, GA is DEAD. The engines that use 75% of the fuel cannot use Mogas.
If any fuel results in the derating of the engines it will mean the death of the twin fleet.
The ONLY answer that can save GA will have to be a drop-in replacement for 100LL, blendable with 100LL at any and all concentrations until the conversion to the new fuel is complete, is transparent to the operator, and keeps all engines operating without ANY modification. Any other notion is destined to failure. There is only one fuel that satisfies all of those requirements which is anywhere close to certification or is being tested in significant quantities by an independent source. Oh, and it can be made by a significant number of refineries--in short order.
You cannot mix AVgas and other fuels because of the lead. THAT is the reason it costs more to transport.
BTW, if we rely on Mogas to be the replacement, GA is DEAD. The engines that use 75% of the fuel cannot use Mogas.
If any fuel results in the derating of the engines it will mean the death of the twin fleet.
The ONLY answer that can save GA will have to be a drop-in replacement for 100LL, blendable with 100LL at any and all concentrations until the conversion to the new fuel is complete, is transparent to the operator, and keeps all engines operating without ANY modification. Any other notion is destined to failure. There is only one fuel that satisfies all of those requirements which is anywhere close to certification or is being tested in significant quantities by an independent source. Oh, and it can be made by a significant number of refineries--in short order.
You cannot mix AVgas and other fuels because of the lead.
Regarding the ATSM, there has been extensive coverage in Avweb on this issue and if I recall properly there has been criticism of the ATSB for delaying the testing of alternate fuels in the US Senate.
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There may be criticism, but ATSM is not there to solve the problem as I see it. ASTM is and industry association which feathers its own nest in order to stay relevant. That is not a slagging off but a bit like "Standards Australia".
It is up to industry to solve the problem and then ASTM to peer review and publish a Standard or cookbook recipe page for the rest of industry to work to.
As Walter will no doubt confirm, not everything that gets printed in AvWeb is wholly reflective of the bottom line.
It is up to industry to solve the problem and then ASTM to peer review and publish a Standard or cookbook recipe page for the rest of industry to work to.
As Walter will no doubt confirm, not everything that gets printed in AvWeb is wholly reflective of the bottom line.
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I have the greatest respect for Paul Bertorelli and have considered him a friend for a couple of decades.
He knows that Mogas cannot and will not replace 100LL nor is that the point of his article. The point is that, yes, most of the low-use, low power, recreational pilots out there can continue to use Mogas as they have for a looong time…. BUT it will not work in the working fleet of high performance singles and twins. He has seen the data on the detonation margins on these fuels and he knows that it simply will not work in the high-powered engines without derating them--and that will kill the working twin fleet instantly. All sources seem to agree on that issue.
There is no Mogas formulation that can be the answer as a 100LL replacement. That's the science. Period. Parade rest.
In the current or foreseeable economical situation FBOs cannot afford the infrastructure of two gasoline products. It's NOT going to happen. We need ONE fuel that will service the entire fleet and allow profitability for the FBOs. If the Mogas crowd wants to continue to use it, fine… they can continue to haul it to the airport like I did for years.
100LL is going to go away and it should. We need a drop-in unleaded replacement to help GA survive--NOW. Without it, GA is dead. It may die anyway.
Based on what I know of the G100UL fuel under development, I doubt it will be priced much differently than 100LL--certainly not significantly higher. Based on what I know of Swift fuel it cannot be mass-produced as easily or economically.
He knows that Mogas cannot and will not replace 100LL nor is that the point of his article. The point is that, yes, most of the low-use, low power, recreational pilots out there can continue to use Mogas as they have for a looong time…. BUT it will not work in the working fleet of high performance singles and twins. He has seen the data on the detonation margins on these fuels and he knows that it simply will not work in the high-powered engines without derating them--and that will kill the working twin fleet instantly. All sources seem to agree on that issue.
There is no Mogas formulation that can be the answer as a 100LL replacement. That's the science. Period. Parade rest.
In the current or foreseeable economical situation FBOs cannot afford the infrastructure of two gasoline products. It's NOT going to happen. We need ONE fuel that will service the entire fleet and allow profitability for the FBOs. If the Mogas crowd wants to continue to use it, fine… they can continue to haul it to the airport like I did for years.
100LL is going to go away and it should. We need a drop-in unleaded replacement to help GA survive--NOW. Without it, GA is dead. It may die anyway.
Based on what I know of the G100UL fuel under development, I doubt it will be priced much differently than 100LL--certainly not significantly higher. Based on what I know of Swift fuel it cannot be mass-produced as easily or economically.
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According to:
http://www.lycoming.com/Portals/0/Up...ed%20Fuels.pdf
most low powered Lycoming aircraft engines (O-235, O-290, O-320, O-360 and most injected versions of the above) can use 93 "AKI" fuel. There are also a few other additional specifications relating to vapour pressure and oxygenate content.
AKI = (RON + MON)/2
From the regular fuels available in Australia from my brief research
Unleaded 91 RON = 87 AKI - ie unsuitable
"Premium" unleaded 95 RON = 90-91 AKI - ie unsuitable
Premium unleaded 98 RON = 93-94 AKI - quite possibly suitable
So there is some possible respite for flying schools with these fuel types... Of course, we need a new fuel truck and tank to handle it... which would possibly chew up all of the savings.
Lycoming's service instruction has this information though:
(sorry about the *s - a copy and paste from a PDF).
Current average price for 98 RON in Perth is $1.60
AVGAS at Jandakot is $2.16
http://www.lycoming.com/Portals/0/Up...ed%20Fuels.pdf
most low powered Lycoming aircraft engines (O-235, O-290, O-320, O-360 and most injected versions of the above) can use 93 "AKI" fuel. There are also a few other additional specifications relating to vapour pressure and oxygenate content.
AKI = (RON + MON)/2
From the regular fuels available in Australia from my brief research
Unleaded 91 RON = 87 AKI - ie unsuitable
"Premium" unleaded 95 RON = 90-91 AKI - ie unsuitable
Premium unleaded 98 RON = 93-94 AKI - quite possibly suitable
So there is some possible respite for flying schools with these fuel types... Of course, we need a new fuel truck and tank to handle it... which would possibly chew up all of the savings.
Lycoming's service instruction has this information though:
Automotive*ground*transportation*fuels*available*direct*to*c onsumers*(e.g.*“pump*gas”)*usually*do*not*have*labels*with*s ufficient*information*to*identify*compliance*with*the*requir ements*in Table*2.*While*indicated*octane*is*generally* necessary*for*display* at*retail*points*of*sale,*octane*rating*methods,* fuel* vapor* pressure,* oxygenate* content* and* ethanol* content* can* vary* widely* and* are*generally*known*only*at*the*wholesale*terminal.
Current average price for 98 RON in Perth is $1.60
AVGAS at Jandakot is $2.16
BUT it will not work in the working fleet of high performance singles and twins.
However, 91 RON MOGAS STC's are currently available for the majority of Cessna and Piper singles and a bunch of Bo's. Collectively, C150, C172, C182, PA28's would represent (In Australia) about 20% of the fleet by numbers and probably much greater in terms of fuel consumed because this is the training fleet.
These aircraft could run on MOGAS within weeks. But why hasn't made any significant penetration? Because no-one has the dual pumps (80/87 & 100/130) that they used to and the unduly arduous regulations for aviation fuel handling make it not worth airports investing the money in additional pumps for MOGAS. This will be an impediment to the introduction of 100LL replacement fuels also.
so, these big twins can't take a lower RON/MON/AKI fuel because they're highly boosted etc etc etc...
...however, if you look at the FAR's you have to, by regulation, run the engines extremely rich to leave a huge knock margin because noone really knows if the engines are going to knock or not under all circumstances.
Now, if you adopt UL fuel of any sort, suddenly, closed-loop fuelling control becomes possible, and with wide-band lambda/oxygen sensors, you can run rich and still be in control - i.e. you no longer need enormously wide margins to allow for component and calibration tolerances. You would have to change the FAR's to allow this though - a legal problem more than a technical challenge.
Add to this some closed-loop knock control and you could readily run within a gnat's cock of the knock limit all the time.
This should allow either an improved CR or a reduced fuel AKI rating (or both) for the same power. Not only that, but its highly likely your fuel consumption for the same power will drop usefully.
I'm guessing that this might be what Lycoming have achieved with their iE2 system, expensive and complicated as it is. I have no idea how successful they have been with it though. Is anyone out there running one?
...however, if you look at the FAR's you have to, by regulation, run the engines extremely rich to leave a huge knock margin because noone really knows if the engines are going to knock or not under all circumstances.
Now, if you adopt UL fuel of any sort, suddenly, closed-loop fuelling control becomes possible, and with wide-band lambda/oxygen sensors, you can run rich and still be in control - i.e. you no longer need enormously wide margins to allow for component and calibration tolerances. You would have to change the FAR's to allow this though - a legal problem more than a technical challenge.
Add to this some closed-loop knock control and you could readily run within a gnat's cock of the knock limit all the time.
This should allow either an improved CR or a reduced fuel AKI rating (or both) for the same power. Not only that, but its highly likely your fuel consumption for the same power will drop usefully.
I'm guessing that this might be what Lycoming have achieved with their iE2 system, expensive and complicated as it is. I have no idea how successful they have been with it though. Is anyone out there running one?
AndyRR
I would love to have a go at that. A Motec system would be relatively cheap and sensational. Half the problems with converting to alternate fuels is the fuel handling. If you could use modern solid state fuel pumps it would be so much better. But just thinking about the grief you'd get from CASA makes my head hurt.
I would love to have a go at that. A Motec system would be relatively cheap and sensational. Half the problems with converting to alternate fuels is the fuel handling. If you could use modern solid state fuel pumps it would be so much better. But just thinking about the grief you'd get from CASA makes my head hurt.
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Geez if it was all that simple.....somebody may have done it by now
Andy, you are onto some of it and yes the GAMI PRISM system will help but there is more to it than that.
I have seen PRISM working on the Dyno, and it works very well at killing off detonation however on premium car gas it works, but not all mogas. This requires pressure sensors not the conventional auto acoustic sensors. Again not that simple.
The problem then is of derating the engine due to massive retardation. The piston twin feet can't cop that, they struggle as it is.
The solution is to build a fuel that works, supply it via a tight quality control delivery service and all is good in the world. This discussion is likely to be very different in a years time.
The problem is their sensors can't handle the leaded fuel, and once that is gone it will be a perfect power plant, and a LOP one at that Mike Kraft (Lycoming)is very keen to see this happen and publicly says so.
Andy, you are onto some of it and yes the GAMI PRISM system will help but there is more to it than that.
I have seen PRISM working on the Dyno, and it works very well at killing off detonation however on premium car gas it works, but not all mogas. This requires pressure sensors not the conventional auto acoustic sensors. Again not that simple.
The problem then is of derating the engine due to massive retardation. The piston twin feet can't cop that, they struggle as it is.
The solution is to build a fuel that works, supply it via a tight quality control delivery service and all is good in the world. This discussion is likely to be very different in a years time.
I'm guessing that this might be what Lycoming have achieved with their iE2 system, expensive and complicated as it is. I have no idea how successful they have been with it though. Is anyone out there running one?
Mike Kraft (Lycoming)is very keen to see this happen and publicly says so.
Yes, I agree that it isn't simple. I'm not suggesting it is, but it is possible!
I'm sure that PRISM is a great thing too (the GAMI one, not the NSA version!), but from what I see, it still is only manipulating ignition angle with no control over air-fuel ratio. The two are/need to be very closely related if you want to reduce your margins to nothing. Also, while it's nice to measure cylinder pressure for knock estimation, it's not the only method out there. Spark ionization can yield some good results and piezo-acoustic knock sensors are also far from useless old-tech.
And as for de-rating, well engines are derated with altitude, temperature and condition all the time, only we have at best a few rules-of-thumb methods to predict and deal with it. At least a FADEC-type system could give you an accurate and real-time power prediction to give you a go-no-go decision point for the take-off roll. Such a system could also include a fuel quality warning based on ground run-up data.
I think GA would be better learning to adapt to an automotive gasoline standard that would be mandated at some known future point rather than waiting for another expensive, low-volume, silver-bullet fuel to arrive.
I'm sure that PRISM is a great thing too (the GAMI one, not the NSA version!), but from what I see, it still is only manipulating ignition angle with no control over air-fuel ratio. The two are/need to be very closely related if you want to reduce your margins to nothing. Also, while it's nice to measure cylinder pressure for knock estimation, it's not the only method out there. Spark ionization can yield some good results and piezo-acoustic knock sensors are also far from useless old-tech.
And as for de-rating, well engines are derated with altitude, temperature and condition all the time, only we have at best a few rules-of-thumb methods to predict and deal with it. At least a FADEC-type system could give you an accurate and real-time power prediction to give you a go-no-go decision point for the take-off roll. Such a system could also include a fuel quality warning based on ground run-up data.
I think GA would be better learning to adapt to an automotive gasoline standard that would be mandated at some known future point rather than waiting for another expensive, low-volume, silver-bullet fuel to arrive.
AndyRR
I would love to have a go at that. A Motec system would be relatively cheap and sensational. Half the problems with converting to alternate fuels is the fuel handling. If you could use modern solid state fuel pumps it would be so much better. But just thinking about the grief you'd get from CASA makes my head hurt.
I would love to have a go at that. A Motec system would be relatively cheap and sensational. Half the problems with converting to alternate fuels is the fuel handling. If you could use modern solid state fuel pumps it would be so much better. But just thinking about the grief you'd get from CASA makes my head hurt.
