ORIGINAL: proptop
One of my childhood mentors always said "break it in on the airplane" because it will get better cooling airflow and the engine will be operating in it's intended environment.
I agree with that...usually...unless it's an engine that I feel might benefit from a little bench "testing"...besides, sometimes I just want to hear it's "voice" and maybe bug the neighbors a little...
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I'm not argueing with you, so don't take my comments that way, please.
I used to fly control line exclusively when I was young. All I could afford.
Ever have a new engine get off (launched) just right, then something changes and the engine goes unmercifully lean? It's happened to me and it is why I won't break-in an engine on a model airplane. To have to listen to your engine melt itself down for an entire tank full of fuel can be agonizing.
Yeah, R/C is different. We can throttle back and land. It's just something with me, I guess. I like knowing exactly what is happening to my engine during its initial runs. Once proclaimed as "broken-in", my attitude changes in a most curious fashion. It just doesn't matter as much any more.