why do some types endorse LOP ops?

Tantalum said:
There was an damning report of epic proportions where a Piper Chieftain had a dual engine failure that was blamed more or less on aggressive LOP operations: https://www.atsb.gov.au/media/1292159/aair200002157_001.pdf

Flying Mag did an article on it too but I can't find it now
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https://www.avweb.com/news/pelican/182152-1.html
https://www.avweb.com/news/pelican/182153-1.html

When you get some time, read the rest of John Deakin's articles - https://www.avweb.com/news/pelican/182146-1.html
 
citizen5000 said:
Auto engines are not designed to deal with extremes of temperature change or extreme changes in air density in short periods of time. Aircraft engines run at 100% power and redline in climbs then 75% cruise for long periods. An auto engine is only designed to accelerate for seconds then cruise at a fraction of total power. Aircraft engines produce a lot of torque at low RPM (2700) but car engines produce very low torque at that RPM level. Car engines are designed to be liquid cooled. Aircraft engines are air cooled. Auto engines produce peak power at 6000 RPM and if used in an aircraft would need extreme gear reduction that would add cost, complexity and maintenance issues.
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it's actually for these reasons that the diesel seemed to make sense... they're happy at high power settings for a long time and have their torque at low RPMs as well...
 
Cpt_Kirk said:
When you get some time, read the rest of John Deakin's articles
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Yep, I remember the articles were pretty "epic" and that Flying after came under some fire too for running with the whole LOP thing. All kind of goes back to though people not necessarily understanding what the mixture actually does to the engine. At least in my training days there was very limited instruction on the mechanics of the engine. My dad was an engineer and my brother is an engineer at Pratt Whitney, so most of what I know about engines came from them, not CFIs...
 
Tantalum said:
it's actually for these reasons that the diesel seemed to make sense... they're happy at high power settings for a long time and have their torque at low RPMs as well...
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Cept they weren't designed to run at >50% power for extended duration. Not a very reliable and durable solution. Also unless it's turbo'd it isn't going to do very well at altitude or in the cold.
 
I mean, ultimately neither gas nor diesel engines were designed from the outset for aviation use. Gas engines are generally lighter so those were optimized for aviation, but most high power for long time low rpm torque applications rely on diesel, those can be optimized for aviation as well like Austro does for Diamond..
 
I don't want to come across as argumentative but ...aviation is application specific. Time and time again the cross overs fail. All technologies have their limitations and need to be designed around for aviation.

You get that desiel working then what prop are you gonna spin? It's no simple answer.
 
Tantalum said:
Yep, I remember the articles were pretty "epic" and that Flying after came under some fire too for running with the whole LOP thing. All kind of goes back to though people not necessarily understanding what the mixture actually does to the engine. At least in my training days there was very limited instruction on the mechanics of the engine. My dad was an engineer and my brother is an engineer at Pratt Whitney, so most of what I know about engines came from them, not CFIs...
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I agree about learning nothing from my CFI's. All my engine knowledge comes from me seeking out the information myself. I'm not perfect, but Im always trying to learn.
 
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Checkout_my_Six said:
I don't want to come across as argumentative but ...aviation is application specific. Time and time again the cross overs fail. All technologies have their limitations and need to be designed around for aviation.
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That's true, but fundamentally you want the most power at the lower RPM settings that closer match propeller peak efficiency. In most torque/RPM curves the diesel wins out over gasoline. Are there limitations to it, sure, and any tech, like you've noted, has to be tailored to be aviation specific since it's a very peculiar and finicky environment

Some cross overs fail, but the Austro Diamonds seem to do okay. I think at this point the bigger reason these things don't exist in the market is not because they're thermodynamically inadequate, it's because the costs are too high to certify and like others have said all the mechanics know their Lycomings and Continentals. Diamond Diesels don't catch on for these same reasons, and because the TWIN market in general is very soft
 
I'm not advocating diesel use in GA, someone else mentioned Austro and how they adapted a car engine and I merely noted that it wasn't apples to apples since that was diesel..
 
Tantalum said:
That's true, but fundamentally you want the most power at the lower RPM settings that closer match propeller peak efficiency. In most torque/RPM curves the diesel wins out over gasoline. Are there limitations to it, sure, and any tech, like you've noted, has to be tailored to be aviation specific since it's a very peculiar and finicky environment

Some cross overs fail, but the Austro Diamonds seem to do okay. I think at this point the bigger reason these things don't exist in the market is not because they're thermodynamically inadequate, it's because the costs are too high to certify and like others have said all the mechanics know their Lycomings and Continentals. Diamond Diesels don't catch on for these same reasons, and because the TWIN market in general is very soft
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Ok....now you're into developing a prop that won't resonate. It just doesn't bolt together. :D

My point is....any of those technologies could work, but it requires special development for them to work in the aviation environment.

But all that is old and passe....electric is where it's at today. :D
 
The issue is tuning. On a Cirrus with the O-550, the fuel, induction and the exhaust are tuned. This results in very similar conditions within each cylinder. Most injected legacy aircraft have fuel tuning and no you cannot run LOP an engine with a carb.
 
I ran a carb'd 0-540 in my Six LOP just fine....In fact a Lycoming engineer ran it that way from MD all the way to Oshkosh one year. :D
 
Experimental involvement tends to confirm what one observes in the certified marketplace. And does so without undue influence from litigation pressure. That is, with easy cheap access to good engine instrumentation and GAMI-like injectors, LOP ops on legacy engines is an obvious winner. No problem with auto engine adaptations is insurmountable but they are clearly many challenges given the preponderance of failures and retired experiments - legacy engines continue to be the go-to solution for people who mainly want to fly.

Otherwise, what Ted says.

My current answer is an RV-10, filled to the brim with stuff, running an IO-540 that I lean in the climb starting at 3000' (not LOP) and cruise between 8,000 - 11,000 at 155knots and 10gph (LOP). I don't touch the mixture until turning the final approach leg. Turning off the runway I go back to the LOP setting to park. After much fooling around, the only time I'm using the instruments to set the mixtur is during the climb, otherwise I know the single setting I fly the rest of my CC flights with.


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