This was sent to me so I thought I’d share it.
The counterpoint:
https://www.advancedpilot.com/articles. ... cleid=1838

dogpilot wrote:The thing with leaning is you can get to detonation. That is the roughness you feel when you over-lean. Gasoline is a very explosive substance, so much so, one of the largest and most destructive non-nuclear bombs is the fuel air bomb. So detonation is an explosive combustion instead of a wave front. It can, if it gets severe do all kinds of things, like bend rods and so on. You would have a whole host of symptoms if that was the case. I'm not a piston guy by any stretch of the imagination, I'm a turbine guy, but my ex-partner was a guru of all things gasoline. So my learning is on the order of the intellectual Robin Hood, steal from the clever and give to the not so. It is all what I observed around my shop, which had some very talented engine guys and what they shared with me.

Yes you could have that movie worthy hairline crack developing on some critical component at some point of lousy timing over long stretches of pointy rocks. But every engine has that potential. As my ex-partner in Islena Airlines, Arturo once said why not fly it (a Birddog) over the Gulf of Mexico to Key West, "the engine don't know its over water." He did pose the question, would you rather ditch or lose an engine of the Yucatan's triple canopy rain forest, only 300' to fall after you hit the tree tops? I flew it over the gulf.

So don't overthink it, you did an inspection, looked good.

Wise words from your ex partner.
I’ve flown over the Yucatán in a ratty 206 at 1000’ agl and would much rather have been over open water.
The thought of a forced landing in that jungle was absolutely terrifying! No way anyone would find you....if they even were looking.

BTW sorry for the thread hijack

I agree with dogpilot. Detonation is what Lycoming is worried about. Detonation is certainly nothing to trifle with, and it is at least theoretically possible to achieve same by IMPROPER leaning. That doesn’t mean that PROPER lean of peak WILL cause detonation. Their point is simply that the margin for error when LOP is not as great.

When operating LOP, you really need to be carefully monitoring engine parameters constantly. So, altitude change, or other change can push the engine into dangerous territory. At least theoretically.

I’ve run Continental fuel injected engines LOP quite a bit. And, with a good bit of healthy paranoia. Because Lycoming says they don’t want you to run their engines, I figure that’s good enough for me. I assume they know quite a lot more about the subject than I do.

MTV

mtv wrote:I agree with dogpilot. Detonation is what Lycoming is worried about. Detonation is certainly nothing to trifle with, and it is at least theoretically possible to achieve same by IMPROPER leaning. That doesn’t mean that PROPER lean of peak WILL cause detonation. Their point is simply that the margin for error when LOP is not as great.

When operating LOP, you really need to be carefully monitoring engine parameters constantly. So, altitude change, or other change can push the engine into dangerous territory. At least theoretically.

I’ve run Continental fuel injected engines LOP quite a bit. And, with a good bit of healthy paranoia. Because Lycoming says they don’t want you to run their engines, I figure that’s good enough for me. I assume they know quite a lot more about the subject than I do.

MTV

If you read the rebuttal that was posted it really shows the opposite of what you are saying. Even by looking at the power charts on the initial lycoming document it makes sense that 50 ROP is worse then 50 LOP. 50 ROP produces higher CHTs and pressure, which actually gives a narrower margin for error the running LOP...

A1Skinner wrote:

mtv wrote:I agree with dogpilot. Detonation is what Lycoming is worried about. Detonation is certainly nothing to trifle with, and it is at least theoretically possible to achieve same by IMPROPER leaning. That doesn’t mean that PROPER lean of peak WILL cause detonation. Their point is simply that the margin for error when LOP is not as great.

When operating LOP, you really need to be carefully monitoring engine parameters constantly. So, altitude change, or other change can push the engine into dangerous territory. At least theoretically.

I’ve run Continental fuel injected engines LOP quite a bit. And, with a good bit of healthy paranoia. Because Lycoming says they don’t want you to run their engines, I figure that’s good enough for me. I assume they know quite a lot more about the subject than I do.

MTV

If you read the rebuttal that was posted it really shows the opposite of what you are saying. Even by looking at the power charts on the initial lycoming document it makes sense that 50 ROP is worse then 50 LOP. 50 ROP produces higher CHTs and pressure, which actually gives a narrower margin for error the running LOP...

A1Skinner that’s my conclusion as well.

George Braley/GAMI and John Deakin have provided a lot more data and evidence to back up their side of the argument than has Lycoming, in my estimation.
Both however seem to also provide quite a bit of rhetoric, which isnt helpful.
My experience w LOP ops kinda showed the opposite Mike. Once I figured out the settings it was a fairly simple process: take off ROP by the book, climb by the book then set up cruise by the book, and finally pull the mixture to the pre determined FF. CHTs were always 30-40 degrees lower than ROP.
Need to climb? Simple as running ROP. Go right to left: cowls open, mix in, prop in, then throttle. Piece of cake.
You make it sound complicated and I respect you so I wonder what I’m missing.

I look at it this way, as said, if the manufacturer says that is how you should operate it, I do. There is an underlying reason for that. You will never be skewered for following normal operating procedures. Now the lads at GAMI have their points, but I have a very personal opinion of GAMI, which I will not share on this board. Meet me, ask me. Besides it would start a poster war akin to oil brand, type and additives. It would transcend religion.

Spent the day tapping out the dent the bat left on my leading edge, coming along nicely. Patience. Now one major difference between the G/F model and the H, I forgot to mention. The H has epoxy primer inside and out, every single piece (along with stamps in various places, "Hecho en Mexico."). The long term longevity of the aircraft is greatly enhanced by proper corrosion protection at the factory. There is really no way to do that, except at build. Like my bud Victor, who builds up fish spotting helicopters for tuna boats. Its life span really depends on the primer. He did a lot of testing.

So the H has better corrosion-proofing?
Wasn’t aware of that.

Sierra Victor wrote:

A1Skinner wrote:

mtv wrote:I agree with dogpilot. Detonation is what Lycoming is worried about. Detonation is certainly nothing to trifle with, and it is at least theoretically possible to achieve same by IMPROPER leaning. That doesn’t mean that PROPER lean of peak WILL cause detonation. Their point is simply that the margin for error when LOP is not as great.

When operating LOP, you really need to be carefully monitoring engine parameters constantly. So, altitude change, or other change can push the engine into dangerous territory. At least theoretically.

I’ve run Continental fuel injected engines LOP quite a bit. And, with a good bit of healthy paranoia. Because Lycoming says they don’t want you to run their engines, I figure that’s good enough for me. I assume they know quite a lot more about the subject than I do.

MTV

If you read the rebuttal that was posted it really shows the opposite of what you are saying. Even by looking at the power charts on the initial lycoming document it makes sense that 50 ROP is worse then 50 LOP. 50 ROP produces higher CHTs and pressure, which actually gives a narrower margin for error the running LOP...

A1Skinner that’s my conclusion as well.

George Braley/GAMI and John Deakin have provided a lot more data and evidence to back up their side of the argument than has Lycoming, in my estimation.
Both however seem to also provide quite a bit of rhetoric, which isnt helpful.
My experience w LOP ops kinda showed the opposite Mike. Once I figured out the settings it was a fairly simple process: take off ROP by the book, climb by the book then set up cruise by the book, and finally pull the mixture to the pre determined FF. CHTs were always 30-40 degrees lower than ROP.
Need to climb? Simple as running ROP. Go right to left: cowls open, mix in, prop in, then throttle. Piece of cake.
You make it sound complicated and I respect you so I wonder what I’m missing.

Yes, and you’re talking about paying attention, which is what I suggested. I’ve watched supposedly competent pilots initiate a climb and /or a descent without bothering with mixture at all. They’re out there, and they have the capability of screwing the pooch, even in something as relatively simple as leaning.

I’m not a big fan of Braley & Company either. Too much calling BS on everyone else.

But, hey.....it’s your engine, and your ass, so make yourself happy.

As I said in my first comment on this, I didn’t intend to start a pissing contest. The bottom line is, Lycoming says don’t run their engines lean of peak. That’s all I intended to point out.

Do what you will with it.

MTV

What I do find interesting is when you old guys, who i respect very much, will say the manufacturer has its operating limits so they follow them. Yet when it come to things like STOL kits and flying off airport, I would be willing to bet you don't continue to fly the numbers that Cessna calls out in the POH from 1970 or when the plane was built... not in a pissing match either, I just find that point interesting.

You caught us. But analyze it a bit. Engines are a bit complicated. Personally I have had 5 complete engine failures, one dual on a Hawkeye. So I have a healthy respect for engine parameters, there is a bit of magic going on there that does not take much to send it over the edge. Based on experience I, which age does give you a wealth of, don't poke certain bears.

Now aerodynamics of your airplane. So you mod your plane with an STC'd STOL kit. Real STOL kits have performance charts or changes in little details like stall speed, climb speeds and so on. Real STOL kits that is. Then every aircraft is a bit different, even adjacent serial numbers. They are hand built and they are all a bit different. They also get subtly bent over time. So you can get a feel for your aircraft, when it actually stalls, which wing stalls first, when your controls stall. There is how much power margin vs weight you have. So we may fly it bit different from the manual, which provide safe speeds for a standard, un-modified aircraft. Those numbers are there to keep Doctors & Lawyers safe from themselves.

Again, old dude experience has shown; there is stuff going on in the engine I will not see the outcome until a rod decides to burst through the engine case, like a face hugging alien. I can see the result of what is happening when I fly and determine my margins. It isn't some fatiguing bit of metal or overtemping blade or burning burner can due to a fuel nozzle having a microscopic fleck of interstellar matter, slightly clogging it causing uneven flow, leading to unconfined blade failure.

I poke horses, not bears.

“normal” and “average” procedures and performance. They aren’t necessarily trying to extract every last bit of performance from a flight test airplane. So the result is limited by the parameters placed upon the test program. Final approach at 1.3 Vso, etc.

It’s actually fairly easy to improve on those numbers. And the manufacturers don’t consider those parameters “limiting”, they are simply offered as “This is what the plane did during the flight test program.”

Now, there are limits the manufacturers do consider “hard” limits. I stay away from those.

And, as dogpilot noted, once the plane is modified, in at least some cases, the Pilot has to develop his/her own performance data. Ever see a Flight Manual Supplement for a Micro VG kit?

But, Robertson did provide a FM Supplement for its kits. So, for example, the Cessna 185 FM from the factory gives around 56 knots as stall speed (going from memory here, and it’s early ) . RSTOL Flight Manual Supplement gives 37 knots Vso for the same airplane. THAT data was developed by a test pilot who was using every bit of skill he possessed.

I’ve had one catastrophic engine failure and two cases where a healthy engine rolled back to idle because of accessory or control failures. The one broken crankshaft was sending signals before it failed, but three great mechanics couldnt find any problem with the engine. So I flew it. Ultimately, after a year and a half studying that engine, the NTSB lab concluded that the crankshaft failed at the # 2 rod journal. I had previously noted that discrepancy...... But one of the best labs of its type couldn’t determine why it failed. As dogpilot says, there is some magic inside these engines. Poke that demon at your peril.

MTV

Mike I certainly wasn’t trying to start a pissing contest either.
I’m honestly curious and trying to gather as much info as I can and of course the internet is full of it! Literally.

I appreciate the feedback you and Dogpilot have provided. I tend to value experience over data, for the most part, so thanks for that.

I agree SV. The experience here is invaluable.
Mike, on the engine that had a catastrophic failure on you, were you running it LOP or IAC with manufacturers spec?

A1Skinner wrote:I agree SV. The experience here is invaluable.
Mike, on the engine that had a catastrophic failure on you, were you running it LOP or IAC with manufacturers spec?

No, as far as I know, that engine had never been run LOP. And I’d flown that engine probably 99% of its 1300 hours. I have always felt that I may have done something wrong with the engine. Unfortunately, after 18 months in the NTSB engine lab, they couldn’t identify anything.

So, magic I reckon. And I hate that shit.

MTV