leaner = hotter, richer = cooler is for the combustion chamber.
Wouldn't that would make LOP operations impossible, because the engine would get too hot?
http://www.warmkessel.com/jr/flying/td/jd/images/pelperch_aps_leaning_chart.jpg
This chart is the similar to those published by Lycoming, Continental, and various regulators.
What damages an engine? Heat.
Quite simply, the data shows that around peak EGT, the cylinder head temperatures, and so the internal pressure (pressure and temperature being directly proportional) are at their maximum. The reason that people keep making a big deal out of all this LOP/ROP thing is that it shocks us that the engine manufacturers give advice that is EXACTLY opposite to what the data suggests.
On other matters: While I'm no expert, I am willing to debate the concept of LOP in a carburetted engine, or without an engine monitor.
I think either is perfectly acceptable.
If you operate where the POH suggests you are already operating at the worst possible place. If you're flying at 50ROP you are producing the highest CHTs, and coupled with a high-ish power setting these may be too high. If you fly at 50ROP at high altitude or with a low setting, then that of course may be fine.
My point is, if you have no idea what your EGTs/CHTs are, and you lean as per the flying school "till the engine is rough, then richen till smooth", you likely have cylinders that are LOP, and some that are ROP. The roughness was the leanest "falling off" the BHP curve as shown in the graph. So if you mixture distribution is good you may have part of your engine LOP anyway! This being without intending to operate beyond peak, because as everyone know, engines explode there.
So you have two options:
Lean as far as possible for fuel economy and to keep your engine clean, and at a sensibly low power setting to ensure that the cylinders close to peak are happy.
Or, fly conservatively rich at whatever setting you want. Noting of course that mixture alters the power produced, and most tables include the condition that best power is set.
These are only my opinions, largely collected from reviewing the data available, so feel free to disagree.
Last edited by Aerozepplin; 19th Oct 2011 at 02:54.
Reason: quoting failure