Think less: “Airplane”
Think more: “circa 1950 British mortorcycle”
Now that your head is in the right place, cooling is primarily done by air entering the intakes and being directed by the cowling and engine baffles straight down around the cylinders and out the bottom of the cowl. Oil is cooled by an air-cooled oil cooler that is usually located in one of the intake inlets.
That’s a fair assumption but I think it is optimistic. They get their data from the Lycoming and Continental maintenance manuals which are themselves not very in-depth. These engines have been pretty much unchanged since the war. They are simple as dirt and as dependable as a sunrise. There is little reason to confuse the pilot with a lot of fiddly engine parameters. Just…
- Don’t overheat it,
- Don’t overrev it.
Make it more complicated than that and the lawyers double their billable hours after each accident. That is at least until the 90’s when very sophisticated engine monitors became available. They were expensive but they came with the promise that the owner could now safely maximize power and minimize fuel burn, quickly paying for the cost of the technology. But this sophistication was a bit much for us ignorant pilots and soon cylinders and exhaust pipes began to crack with increasing frequency. To bring us up to speed, pilot/mechanics like Mike Busch reached out to fill the vast gaps in our knowledge with pilot-friendly articles that have probably saved millions in maintenance to those who took the time to get educated. Today we are (FINALLY!) starting to add electronic ignition to the mix which will greatly increase the benefits of all this sophisticated leaning and monitoring. But electronic ignition is still pretty rare in certified machines. So the current situation with our 1920’s-technology magnetos is that ignition happens at a fixed crankshaft position (around 25deg btdc) regardless of power-setting or atmospheric conditions. All this tweaking with the prop and mixture is a little like using a mainframe to aim a snowball down an incline.
The good news for most of us is that a Lycoming or Continental carbureted or injected 4-cylinder motor is basically bullet proof. Run it however you want to run it. More harm is arguably done by sitting on the ramp on a hot day idling while you program the Garmin 1000. Or taxiing in after a bunch of heat-inducing touch and goes and shutting down immediately without letting the cylinders cool below 300.
Mike Busch and others are really speaking to the pilots flying tightly cowled IO-540s in high-performance singles and light twins. These engines cost $25,000 apiece to overhaul. So proper care is especially important.
I’ll end by repeating the point that Busch and others have made: 50 degrees ROP often results in the highest CHT. So for those people who were taught (by ME!) that this was the most conservative setting, he made the case that we were flat wrong. Were our students slowly destroying their engines? No. But nor were they doing the great good that they probably thought they were doing. 50 LOP for most motors is probably cooler. And if the engine is running smoothly, it is probably better. The only way to know for sure is to get a nice engine monitor and pull the plugs out for inspection between annuals.
One simple thing I forgot to add. Even though I said “carbureted” I am really talking fuel-injected only. I haven’t flown a carbureted motor since the 90’s. This is a total WAG on my part but if I were flying with a carburetor I would avoid LOP ops.