[net.aviation] Undersquare/Oversquare Question

glenn (01/17/83)

Does anyone have any information on the various tradeoffs between
RPM and MP used to obtain a given power setting (constant-speed prop
assumed)? For example, suppose you choose to cruise at 65% power.
Your nifty operator's manual gives you several combinations of RPM/MP
which can be used to obtain this power setting. Assuming that you
don't care about fuel consumption (which varies little between 
constant-power settings anyway) and you just want to maximize engine
life, how do you choose the best RPM/MP combination?

I am aware that this is an age-old can of worms; everyone seems to have
an *opinion*. I am interested to hear the opinions, but I am more interested
in objective data or pointers to tests or the like which have been done
to establish the relative merits of "undersquare", "square" and "oversquare"
operation. Specifically, what are the mechanical limits that form the
envelope of allowable engine operation, and which limits are less/more 
damaging to engine life? (The engine in question is a Continental O-470-U
installed in a 1982 Cessna 182, if it matters.)

Thanks in advance!

	- Glenn Golden, ABI Holmdel, 1E-537, 949-6203 (UFN).
	  lime!glenn or houxg!glenn