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#1
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Why is LOP (lean of peak) controversial?
I'm not asking about LOP itself, but why it's so "hot" snicker a topic. It would seem to be a simple thing to me: the cylinders run at decent temperatures LOP or they do not. What else is there? I know at least one person in person, and others from their postings, that are getting success running LOP. I also know at least two persons that think that LOP is some myth that kills cylinders. One of those two people tells a story of someone that bought gami injectors, ran LOP, and then cooked four of six cylinders. What I don't understand - and what that person hasn't answered, BTW, perhaps because he doesn't know - is why that person that "cooked" four cylinders would have failed to see a problem immediately on his CHT probes. So...what am I missing? - Andrew |
#2
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Why is LOP (lean of peak) controversial?
Because in years past, several respected gurus of the GA field had
stated that LOP would "burn the engine up" if you did it, and recommended running ROP. In fact, Lycoming actually recommended running 50 deg ROP at full power operation, which G. Braly's research has shown is the absolute worst place to run. Many are probably just trying to cover their ass for being so wrong in the past. At least that is my take, since I believe as you do that it is either true or it isn't. Good point. Bud Andrew Gideon wrote: I'm not asking about LOP itself, but why it's so "hot" snicker a topic. It would seem to be a simple thing to me: the cylinders run at decent temperatures LOP or they do not. What else is there? I know at least one person in person, and others from their postings, that are getting success running LOP. I also know at least two persons that think that LOP is some myth that kills cylinders. One of those two people tells a story of someone that bought gami injectors, ran LOP, and then cooked four of six cylinders. What I don't understand - and what that person hasn't answered, BTW, perhaps because he doesn't know - is why that person that "cooked" four cylinders would have failed to see a problem immediately on his CHT probes. So...what am I missing? - Andrew |
#3
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Why is LOP (lean of peak) controversial?
On 09/26/06 15:38, Andrew Gideon wrote:
I'm not asking about LOP itself, but why it's so "hot" snicker a topic. It would seem to be a simple thing to me: the cylinders run at decent temperatures LOP or they do not. What else is there? I know at least one person in person, and others from their postings, that are getting success running LOP. I also know at least two persons that think that LOP is some myth that kills cylinders. One of those two people tells a story of someone that bought gami injectors, ran LOP, and then cooked four of six cylinders. What I don't understand - and what that person hasn't answered, BTW, perhaps because he doesn't know - is why that person that "cooked" four cylinders would have failed to see a problem immediately on his CHT probes. So...what am I missing? - Andrew I think John Deakin covered this topic in one of his columns. He explained why most of the POHs are worded the way they are, even when it doesn't make sense. For example, have a look at this article (I think this is the right one - I can't find the index to his articles on the AVWeb site any longer): http://www.avweb.com/news/pelican/186216-1.html My impression of the point he tried to make was that the manufacturers believe LOP operations is hard to get right unless you really know what you're doing (and have the proper measuring equipment, i.e.: EGT) and that ROP operations is "safer" from a legal standpoint. .... but it's been a while since I've read his articles on the topic, so I could be off here. -- Mark Hansen, PP-ASEL, Instrument Airplane Cal Aggie Flying Farmers Sacramento, CA |
#4
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Why is LOP (lean of peak) controversial?
Andrew Gideon wrote:
I know at least one person in person, and others from their postings, that are getting success running LOP. You can add me to the list of aircraft owners who religiously run LOP. I bought my aircraft from a pilot who also operated the engine LOP, and I was able to get about 2,600 hours out of an engine that had an 1,800 hours TBO. In the interest of full disclosure there was some cylinder work done to the engine early on, but I can guarantee it was not because a cylinder got cooked. It probably had to do with the fact that they were Continental cylinders. In my case, my engine's cylinder head temperatures rarely get above 310 degrees F and most times operate in the 285 degree F range during cruise flight. The times they do climb to 310 or 320 degrees F is when I am climbing to altitude on a very hot day. One note: Running LOP requires a meticulously maintained ignition system. Plugs need to be cleaned every 100 hours or so, plug wires need to be inspected and replaced if needed, magnetos have to be operating to capacity, and capacitors cannot fail. Something as simple as one fouled plug can result in unacceptably high exhaust gas temperatures that lead to a higher than desired turbo-inlet temperatures. I also know at least two persons that think that LOP is some myth that kills cylinders. One of those two people tells a story of someone that bought gami injectors, ran LOP, and then cooked four of six cylinders. Without knowing their specifics, I can say with experience of operating a turbo-normalized Bonanza that running LOP does introduce the RISK of cooking cylinders, but this risk is easily managed, in part, by including the engine analyzer in one's scan every minute or two. Leaning to a lean of peak temperature involves pulling the mixture PAST peak temperature to a relative fuel flow, then allowing airspeed and engine temperatures to stabilize (perhaps a few minutes of level flight). Once stable, the mixture is then enrichened to peak temperature in order to discover peak temperature and then steadily but without delay leaned back to about 75 degrees lean of peak. Constant monitoring of the engine analyzer gauge and fine tuning of the mixture knob is mandatory. Changing altitudes (usually descending), even in my turbo-normalized aircraft, does require a slight change in mixture or temperatures can begin to climb. What I don't understand - and what that person hasn't answered, BTW, perhaps because he doesn't know - is why that person that "cooked" four cylinders would have failed to see a problem immediately on his CHT probes. My speculation is that it could be one of three reasons. First, but most unlikely, perhaps the probes were incorrectly installed. Second, maybe this owner failed to monitor his engine analyzer often enough, which could be a result of the location of the gauge in the panel or simply the pilot's weaker instrument scanning discipline. And thirdly, this owner may not have had the engine analyzer high-temperature alarms properly set up? Again, just speculation here. -- Peter |
#5
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Why is LOP (lean of peak) controversial?
"Peter R." wrote:
In my case, my engine's cylinder head temperatures rarely get above 310 degrees F and most times operate in the 285 degree F range during cruise flight. The times they do climb to 310 or 320 degrees F is when I am climbing to altitude on a very hot day. I should have included that 380 degrees F is considered the absolute top end of the safe temperature curve, at least according to Tornado Alley Turbo and GAMI, both of whom have done extensive testing of LOP operations. Even on a hot day at higher density altitude (and effectively less ram air cooling), 320 degrees F is the highest I have seen my cylinder head temperatures reach. -- Peter |
#6
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Why is LOP (lean of peak) controversial?
So...what am I missing? - Andrew Hi Andrew Google Walter Atkinson LOP. He is the most knowledgeable that I know of on aircraft engines and is always happy to discuss engine questions - especially LOP. If you just want to read what he has to say, search the archives in the Cessna and Piper groups. HTH Tony -- Tony Roberts PP-ASEL VFR OTT Night Cessna 172H C-GICE |
#7
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Why is LOP (lean of peak) controversial?
"Mark Hansen" wrote in message ... I think John Deakin covered this topic in one of his columns. He explained why most of the POHs are worded the way they are, even when it doesn't make sense. For example, have a look at this article (I think this is the right one - I can't find the index to his articles on the AVWeb site any longer): http://www.avweb.com/news/pelican/ http://www.avweb.com/news/pelican/186216-1.html My impression of the point he tried to make was that the manufacturers believe LOP operations is hard to get right unless you really know what you're doing (and have the proper measuring equipment, i.e.: EGT) and that ROP operations is "safer" from a legal standpoint. ... but it's been a while since I've read his articles on the topic, so I could be off here. Read #8, 15, 16 and particularly #18. Those are the basis of the Advanced Pilot Seminars http://www.advancedpilot.com/index.html (Well worth a couple thousand $$ to protect a $25-30K engine...not to mention your butt). If applicable, read the Turbo's series, #31-36, and #59, 63,64 as well. -- Matt --------------------- Matthew W. Barrow Site-Fill Homes, LLC. Montrose, CO (MTJ) |
#8
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Why is LOP (lean of peak) controversial?
"Andrew Gideon" wrote: One of those two people tells a story of someone that bought gami injectors, ran LOP, and then cooked four of six cylinders. Another example of how a little knowledge is a dangerous thing. *Improper* LOP operating technique can harm cylinders, even cause catastrophic failure by detonation. -- Dan C172RG at BFM |
#9
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Why is LOP (lean of peak) controversial?
On Wed, 27 Sep 2006 09:20:12 -0500, Dan Luke wrote:
*Improper* LOP operating technique can harm cylinders, even cause catastrophic failure by detonation. Hmm. Detonation, if I follow all this correctly, yields lower EGTs. So someone leaning by EGT could be fooled into thinking that all is well, even while cylinders are being damaged. This is exactly the type of idea I was missing; now I think I see. But CHT goes up, right? Would it go up enough (ie. beyond 400) to raise a pilot's concern? - Andrew |
#10
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Why is LOP (lean of peak) controversial?
"Andrew Gideon" wrote in message news On Wed, 27 Sep 2006 09:20:12 -0500, Dan Luke wrote: *Improper* LOP operating technique can harm cylinders, even cause catastrophic failure by detonation. Hmm. Detonation, if I follow all this correctly, yields lower EGTs. So someone leaning by EGT could be fooled into thinking that all is well, even while cylinders are being damaged. This is exactly the type of idea I was missing; now I think I see. But CHT goes up, right? Would it go up enough (ie. beyond 400) to raise a pilot's concern? http://www.avweb.com/news/pelican/182132-1.html Pelican's Perch #43: Detonation Myths We've all been taught about detonation in piston aircraft engines. It's what occurs when combustion pressure and temperature get so high that the fuel/air mixture to explodes violently instead of burning smoothly, and it can destroy an engine in a matter of seconds. Right? Well, not exactly. AVweb's John Deakin reviews the latest research, and demonstrates that detonation occurs in various degrees - much like icing and turbulence - with the milder forms not being particularly harmful. Heavy detonation is definitely destructive, and the Pelican offers some concrete data on how to avoid it. --------------------- |
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