Friday, February 14, 2014

Lean of Peak

I enjoyed the presentation given by Alan Koharcheck very much!  "GA Piston Engine Management. (Lean of peak. Something you were told not to do) -".  Thanks to Alan for doing the presentation and for allowing us the use of his facilities.

However, towards the end of the presentation, I was left with the feeling that I should have been operating my two carbureted Lycoming engines (O-360 A4M and O -320 E2A) on a "Lean of Peak" (LOP) air / fuel mixture condition.

Of course this is contrary to what I have been doing for the last 37 years of flying so I have researched the subject a little and here are my conclusions:

1.  If you have a fuel injected engine and have an engine analyzer with graphical display, then it makes very much sense to operate LOP as per the GAMI recommendations as long as your aircraft manufacturer is ok with it.
2.  If you have a carbureted engine and don't have an engine analyzer, follow the manufacturers recommendations on leaning your particular engine.

An observation on engines operating LOP or Rich of Peak (ROP) is that most engines, irrelevant of the operation, reach or exceed TBO.

So what are the general thoughts regarding the leaning of carbureted engines?  I have found this article written by Wayne Westerman that pretty much explains the issues with those engines: (

I have also found another article at the GAMI website: ( written by Dave Hirschman for AOPA Pilot Magazine, it says in part:
"Not all GA engines can run safely LOP.  Carbureted engines, for example, lack precise fuel/air metering systems and typically run rough and lose power LOP. And electronic engine monitors that show cylinder head and exhaust gas temperatures for every cylinder are necessary for safe LOP operations. Graphic engine monitors are even better.
The danger of flying LOP with a single-cylinder CHT or EGT probe is that some rich-running cylinders could become too hot, damaging internal valves and guides, and causing a loss of engine compression that would require a top overhaul."

So, take your time, research and come to your own conclusions when it comes to operating your engine.  I'd welcome any comments regarding this issue on the blog.

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