GAMI presentation from OSH '24

[Ibra]

1 hour ago, Marc_B said:

But my suspicion is that UND fleet are run way harder than a typically privately owned aircraft would be.

From what I understand (limited), most have said that valve recession was either a detonation event or a microwelding event from lack of lead.  The data presented at Osh was clearly built to detect detonation events.  The initial graphic Braly showed was at 73%HP with CHTs 400-430F in a Continental Engine with 8.5:1 compression and 22 deg timing.  (UND 25 deg timing Lycoming engine).  Next graphic was reported at 69%HP with CHTs still in the 400-430F range with mixture enrichened "somewhat rich of best power mixture".  But clearly looks like UL94 gets into the "red fin" when 100UL and 100LL do not.

Thanks for the details,

Yes, those 400F-430F temps are way higher than what one see running Archer on Mogas or UL91 in “eco mode”, and these fuels have lower octane than UL94 !

It seems they were really banging those O360 engines at UND: peak EGT on WOT at 75% with 430F CHT, the risk of detonation is real 

AFAIK, PeakEGT at 75% is not allowed with Peterson STC, primarly to keep CHT low when using Mogas (no restriction for UL91) 

Anyway the moral of this story, keep CHT under 380F, especially if one uses lower octane 

Most of us on 360 engines don't venture above 400F (except short 5min in hot days climb), irrespective of fuels used: one muddles and fiddles with controls until CHT is back under 380F 

 

Edited August 1, 2024 by Ibra

[FlyingDude]

My only concern would be the need to readjust magneto timing. One, you need to commit to one type of fuel, which might make it hard on a xc or if coverage is patchy in your area; two, I have surefly and I don't know how easy it is to reflash that. Most probably one will have to send it in or swap units. Still, it won't be possible to alternate between fuels. Best would be an overnight switch. 

[M20F]

15 hours ago, Pinecone said:

Due to the handling of the TEL, no new 100LL refineries will ever come on line. 

https://m.economictimes.com/industry/energy/oil-gas/iocl-exports-avgas-to-papua-new-guinea/amp_articleshow/97403764.cms

[Pinecone]

8 hours ago, M20F said:

https://m.economictimes.com/industry/energy/oil-gas/iocl-exports-avgas-to-papua-new-guinea/amp_articleshow/97403764.cms

You got me.  I meant none in the US.

But maybe India can make it cheap enough to ship 1/2 way around the world and still be a competitive price.

 

[GeeBee]

You do know GAMI's G110UL data is available. All of it via FOIA from the FAA. If you have questions, you can examine it yourself.

[jetdriven]

22 hours ago, Ibra said:

Thanks for the details,

Yes, those 400F-430F temps are way higher than what one see running Archer on Mogas or UL91 in “eco mode”, and these fuels have lower octane than UL94 !

It seems they were really banging those O360 engines at UND: peak EGT on WOT at 75% with 430F CHT, the risk of detonation is real 

AFAIK, PeakEGT at 75% is not allowed with Peterson STC, primarly to keep CHT low when using Mogas (no restriction for UL91) 

Anyway the moral of this story, keep CHT under 380F, especially if one uses lower octane 

Most of us on 360 engines don't venture above 400F (except short 5min in hot days climb), irrespective of fuels used: one muddles and fiddles with controls until CHT is back under 380F 

 

Somewhere on the Internet is a graph of a Lycoming engine engine running at redline cylinder head temperature and if you lean it out and run it severely over square you can start to get light detonation, , but it’s actually pretty tolerant. All this talk of having to modify engines to use specific fuels is basically not gonna work  because you have all these situations that are going to result an engine damage if you’re not super careful and Off airport landings as well. 

[A64Pilot]

On 7/31/2024 at 2:48 PM, FlyingDude said:

So nobody ran UL94 with 5* retard?

It most most probably would have been fine, just as putting a knock sensor with modern ignition system would work fine.

But here is the problem, pulling timing reduces power, now suddenly you can’t make published / Certified takeoff distances or climb rates etc without reducing useful load.

However as I keep bringing up and most seemingly ignore is that with water injection I’m sure both 94 UL and even Premium auto fuel would work and meet power requirements, because it has a Looong history of working.

But there is a problem with that too, highly boosted motors would require continuous injection to work, and while I don’t know how much water that would take I feel pretty sure it’s significant, so there goes useful load again, or performance should for example you restrict the high boot to say 5 min or something.

For me in my NA engine I believe water injection would be my best bet, having spoken with one fuel cell manufacturer he said that aeromatics significantly affect the life of bladders. In fact he contends that even 100LL has increased aeromatics and has reduced life span of bladders.

I think that whatever fuel we end up with will take a few years of actual fleet use for us to truly know what will happen, I’ve been in aircraft testing for most of my life before retiring and can attest that you really don’t know until you field a fleet flown in every kind of weather etc to really know what you have, no lab in the world can fully test every possibility, too many variables, for example not every pilot operates their engine by the book for instance.

 

 

[kortopates]

My only concern would be the need to readjust magneto timing. One, you need to commit to one type of fuel, which might make it hard on a xc or if coverage is patchy in your area; two, I have surefly and I don't know how easy it is to reflash that. Most probably one will have to send it in or swap units. Still, it won't be possible to alternate between fuels. Best would be an overnight switch. 

there is no need to change timing for G100UL nor would it be legal to change timing. The STC doesn't allow for any timing change and nor would there be any reason to want to do so.
And the G100UL can be mixed with 100LL - there is no need to commit to one fuel. 
Unless you were referring to running Swift 94UL on your E model which isn't approved.  In the video, Braley was just demonstrating that detonation on that engine went away with the timing retarded approx 5 degrees (simulated with only 1 mag firing) - which was really to show that 94 should never have been approved for that engine by Lycoming. Besides there is more to it that just backing off the mag timing due to the starting circuit; and with the Surefly its a dip switch setting. Edited August 3, 2024 by kortopates

[Pinecone]

16 hours ago, A64Pilot said:

It most most probably would have been fine, just as putting a knock sensor with modern ignition system would work fine.

But here is the problem, pulling timing reduces power, now suddenly you can’t make published / Certified takeoff distances or climb rates etc without reducing useful load.

However as I keep bringing up and most seemingly ignore is that with water injection I’m sure both 94 UL and even Premium auto fuel would work and meet power requirements, because it has a Looong history of working.

But there is a problem with that too, highly boosted motors would require continuous injection to work, and while I don’t know how much water that would take I feel pretty sure it’s significant, so there goes useful load again, or performance should for example you restrict the high boot to say 5 min or something.

For me in my NA engine I believe water injection would be my best bet, having spoken with one fuel cell manufacturer he said that aeromatics significantly affect the life of bladders. In fact he contends that even 100LL has increased aeromatics and has reduced life span of bladders.

 

Some Lycoming engines have timing at 25, some at 20, in the same airframe.  And there is an SB to set the timing to 20 and modify the data plate.  So can't be a huge difference.

Water injection works fine for take off, but the UND issue was with cruise power settings.  Got to carry a LOT of water to run injection in cruise.

[hais]

On 8/1/2024 at 12:57 PM, tony said:

I found this today....

https://www.avweb.com/aviation-news/lycoming-clarifies-g100ul-warranty-impact/

 

Thanks for sharing. So if you are an engine manufacturer, why wouldn't you take the steps to approve? Is the cost prohibitive? 

[M20F]

6 minutes ago, hais said:

Thanks for sharing. So if you are an engine manufacturer, why wouldn't you take the steps to approve? Is the cost prohibitive? 

If you were an engine manufacturer why would you, what benefit is there?  What risks do you expose yourself to?

[Fly Boomer]

11 minutes ago, hais said:

Thanks for sharing. So if you are an engine manufacturer, why wouldn't you take the steps to approve? Is the cost prohibitive? 

Lycoming has been in a long-running fist fight with GAMI in general and George in particular.  GAMI has perhaps the most sophisticated aircraft engine test facility in the world, and Lycoming has their nose out of joint whenever GAMI/George makes an observation about their engines.  Apparently, the idea that an outsider could collect and publish empirically proven data that Lycoming is unaware of causes them to foam at the mouth.  I know there are some on this forum who operate in lockstep with whatever Lycoming says, but there are many others who are open to twenty-first century research and practices.

[Shadrach]

2 hours ago, Pinecone said:

Some Lycoming engines have timing at 25, some at 20, in the same airframe.  And there is an SB to set the timing to 20 and modify the data plate.  So can't be a huge difference.

Water injection works fine for take off, but the UND issue was with cruise power settings.  Got to carry a LOT of water to run injection in cruise.

5° is certainly enough to be the difference between detonating and not detonating.

The timing discussion is a funny one. People often say there’s no significant difference. This begs the question, then why bother to retard the timing?  The truth is somewhere in the middle. It’s noticeable but more-so when at the edges of the performance envelope. My plane is timed to 25°; climbing on a single mag (good approximation of 5° of retard) certainly makes a difference, especially this time of year. 
 

[BlueSky247]

It would be interesting to find out whether the e mag options help with those marginal fuels/borderline detonation conditions. 

 

Me, I'll be over here waiting for the mogas stc. (and waiting, and waiting...)

[Shadrach]

7 minutes ago, BlueSky247 said:

It would be interesting to find out whether the e mag options help with those marginal fuels/borderline detonation conditions. 

 

Me, I'll be over here waiting for the mogas stc. (and waiting, and waiting...)

As far as I know all current E-mags offer timing advance beyond the TCDS specified fixed ignition timing. None that I know of offer retarded timing other than at start up.  I suppose CHT could be used as a parameter for retarding the timing.

[1980Mooney]

20 minutes ago, BlueSky247 said:

It would be interesting to find out whether the e mag options help with those marginal fuels/borderline detonation conditions.

Not from the ability to change advance. There is no way for the e mag to know if the engine is beginning to enter knock/detonate conditions due to fuel quality issue, load, mixture, etc. There is no knock/detonation sensor.

You are thinking of a liquid cooled automobile engine with a feedback loop that monitors engine noise and can discern a knock or detonation sound signature.  No knock/detonation sensor works reliably on an air cooled aircraft engine.  Too much other mechanical noise. "In an auto engine, the common cylinders and head make a more metallic or audible sound that is transferred to the entire block assembly. That is why they can use only one knock sensor to control knock in an auto engine."

https://generalaviationnews.com/2015/05/27/visser-for-10/

If you have an e mag that blindly retards the engine based on something than actual detonation then you could suffer reduced power just when you need it most.

https://generalaviationnews.com/2011/08/29/knock-free/

The e mag might have a hotter spark but I doubt that will help much with low octane knock.

Edited August 3, 2024 by 1980Mooney

[BlueSky247]

Good points but I should have been more clear. My understanding on at least some parts of the emag is hotter and/or burst sparks. Maybe I’m just doing wishful thinking that a more modern mag would make just enough difference in it’s output to help lesser fuels do less damage. 

[Shadrach]

1 hour ago, 1980Mooney said:

Not from the ability to change advance. There is no way for the e mag to know if the engine is beginning to enter knock/detonate conditions due to fuel quality issue, load, mixture, etc. There is no knock/detonation sensor.

You are thinking of a liquid cooled automobile engine with a feedback loop that monitors engine noise and can discern a knock or detonation sound signature.  No knock/detonation sensor works reliably on an air cooled aircraft engine.  Too much other mechanical noise. "In an auto engine, the common cylinders and head make a more metallic or audible sound that is transferred to the entire block assembly. That is why they can use only one knock sensor to control knock in an auto engine."

https://generalaviationnews.com/2015/05/27/visser-for-10/

If you have an e mag that blindly retards the engine based on something than actual detonation then you could suffer reduced power just when you need it most.

https://generalaviationnews.com/2011/08/29/knock-free/

The e mag might have a hotter spark but I doubt that will help much with low octane knock.

CHT redline could be used as a parameter for retarding timing on an emag.  Another option would be rate based above a certain number; something like 2°/ second at or above 400°.  Could easily have an annunciator that shows when the mag is retarded and a push to cancel. Not as sophisticated as a knock sensor but adequate to save the engine if the pilot is too busy to save it.

 

[1980Mooney]

4 minutes ago, Shadrach said:

CHT redline could be used as a parameter for retarding timing on an emag.  Another option would be rate based above a certain number; something like 2°/ second at or above 400°.  Could easily have an annunciator that shows when the mag is retarded and a push to cancel. Not as sophisticated as a knock sensor but adequate to save the engine if the pilots too busy to save it.

 

High cylinder head temperature can be caused by many things unrelated to fuel octane, pre-ignition or knock.  You could have high temperature in only one cylinder.  You could have an errant temp probe.

But you are right  that a system could be designed which makes changes or takes action without command by the pilot in order to "save something".  And when the pilot realizes why he is losing power, speed or climb he can over-ride it.  There is precedent for it in GA with good intentions (automatic action that can be over-ridden by the pilot when (if) he figures it out)- Piper did this with the "Automatic Landing Gear" on the Arrow.  I am sure it saved a few gear-ups and retracted the gear many times when the pilot forgot.  It also caused many accidents when it happened just as the pilot needed the opposite and the pilot did not realize in time.

[tony]

Does anyone remember back in the 90's when Mobil marketed their fully synthetic oil?  It was so much better than all the existing mineral and ashless dispersant oils on the market at that time.    There was no data for the undocumented feature that emerged of the sledge that developed in those engines.  At least Mobil made good for those owner/operators and paid for a  number of engine overhauls.  

Does GAMI give a warranty like that Mobil did for all those owner/ operators who buy their STC?  Getting a blessing from the FAA is useless.  The current FAA doesn't even know how airplanes work anymore.  Any experts that once worked there, have long since retired.  Today the FAA are just populated regulators.  

I think I'm just going to sit on the side lines and let the GAMI proponents become test pilots and generate the data that's lacking.  I will encourage my home airport not to buy this voodoo juice until we know its safe.  

[Shadrach]

On 8/1/2024 at 8:29 AM, tony said:

So I have been reading this thread and I am so suspect.  This guy is so proud of his data and continually refers to his data which cases me to ask myself, what is he not telling me?  a lot of his focus is on predetonation but there are other things to consider.

Questions I cant find the answers too maybe someone could answer:

• Has continental and lycoming endorsed this as an approved fuel?  Has any engine manufacturer endorsed this as an approved fuel?
• Why does he need an STC?  that means something is different?  If I lived in California, and put this stuff in my airplane, its not airworthy until I purchase an STC from him?  Really?  
• He claims to have more energy density, so I assume that all the performance charts should be better than what's published, If he is so big on data, I'd like to see that testing published.
• Has there been any independent testing?
• What happens to an engine over time, with a fuel that has no lead and more energy density?
• Is the latent heat of vaporization the same as 100LL?

Most of those questions have been addressed over the last several years which you’ll find if you do a deep dive into what has been written and presented. 

You keep referring to him as “this guy”.  George and his colleagues (RIP Walt and John) have done more to educate pilots on the inner workings of reciprocating aero engines and the nuances of the combustion science associated with them than anyone in the industry. 

If anything, Lycoming has been a hindrance to those efforts, but they have come along after embarrassing themselves in writing.

At this time, the engine manufacturers have no incentive to endorse a specific fuel. And indeed I would be suspect of such an endorsement.

George Braly would probably answer all of your questions directly if you emailed him.

Be sure to start off the email with “Dear this guy”…

[Shadrach]

On 8/1/2024 at 3:42 PM, Ibra said:

I still don’t buy low octane argument from UL94 in Archer?

Down here we run same aircraft (Archer) and same engines (O360-A) using Total Avgas UL91 with 91 MON and with Peterson STC for Mogas AKI93, SPUL+ or SP98 (SuperPlus) with octane ratings as low as 88 MON 

If there is something wrong it’s likely with UND fleet and the way how they operate, maintain, measure or lean? 

If’s hard to understand how this engine (1:8.5) runs ok on SuperPlus from car pumps yet can’t handle Swift UL94, I am more inclined to believe Lycoming assessment, “it’s aromatics” 

If GAMI has real hard data that O360-A in Archers do need octane min MON100 octane (100LL or G100UL), then Lycoming & FAA will have to review many similar engines in the same bracket: about 40 other engines with 1:8.5CR in 360 series (O360 , IO360, HO360, LVIO360, AEIO360) are approved for UL94, UL91 as well as Mogas: SP, AKI93, EN228…

Only Lyco O320 series (1:7CR) are left to use UL94, UL91 and Mogas

https://www.lycoming.com/sites/default/files/attachments/SI1070AB%20Specified%20Fuels.pdfOn a side note does anyone know where to find this paper? it seems removed from FAA website 

Schlickenmaier, H. W., Wilkinson, R., & Atwood, D. (2014). General Aviation Engine Fleet Assessment for Octane Requirement

It was far the most balanced paper on octane requirement versus (CR, BMEP) plus sensitivity analysis to bore, strike, temperature, altitude and timing

 

only the parallel valve IO360s are 8.5:1. The angle valve engines are 8.7:1.  The UND fleet was running peak EGT, perhaps to keep things consistent with how they were running 100LL prior to the test.

[Rick Junkin]

This will likely prove to be a red herring but it’s out there. AOPA left their dual fuel Baron at OSH due to stains discovered under the wing with G100UL in it. Lots of interesting speculation but no reliable data yet. Read the comments.

https://www.avweb.com/aviation-news/stains-on-aopa-baron-wing-to-be-checked-by-mechanic/

[Fly Boomer]

1 hour ago, tony said:

I think I'm just going to sit on the side lines and let the GAMI proponents become test pilots and generate the data that's lacking.

Eventually, someone will run their gas, and then we shall see.

[A64Pilot]

7 hours ago, Pinecone said:

Some Lycoming engines have timing at 25, some at 20, in the same airframe.  And there is an SB to set the timing to 20 and modify the data plate.  So can't be a huge difference.

Water injection works fine for take off, but the UND issue was with cruise power settings.  Got to carry a LOT of water to run injection in cruise.

Couple of things here, from my memory it’s one Lycoming that reduced timing, the angle valve. Supposedly and while it’s logical and “smells” right I can’t quote chapt and verse to prove it, but Lycoming found that one engine could reduce timing by 5 deg and still make the spec power. Lycoming has a history of being conservative with their HP numbers so it’s understandable, but unless 25 was too much timing, unlikely as Lycoming aren’t idiots, then a reduction to 20 will reduce power, so bumping timing will give you more power.

But as someone that has built many air cooled race bikes and among other things have played with timing, it’s diminishing returns, meaning that yiu reach a point where cyl head temp increases but very little power of any is achieved, burning race gas detonation just wasn’t an issue like it is on normal fuel.

Some say it was for one aircraft manufacturer who had cyl head temp problems, who knows. I think Lycoming was either having temp problems or for reasons of achieving greater reliability they reduced timing by 5 deg, but it’s not applicable for every or even most engines.

The current STC’s that have been out for decades have water injection on if your above 400F cyl head temp and or above 25” MP.

I don’t know about you, but I don’t cruise above 25” MP, or 400 cyl head temp so for me it’s just for a few minutes in T/O and climb that injection would be on, and those numbers are for Premium Auto fuel, not unleaded Avgas which I strongly suspicion is much more detonation resistant than auto fuel, but running premium auto fuel is attractive to me for several reasons, first the cost of course and second it’s availability.