"Ernest Christley" wrote in message
...
...
I'm glad to add the "(well, mostly?)", because I could read that as "not
at all". What you do have with a certified engine is a situation where
the prop manufacturer has tested their prop with that engine. It's a well
studied combination that everyone knows how to work with.

For instance, you can't cut a metal prop down but so far. Why? Because
everyone knows where that resonant point is, and cutting the prop down to
70" will land you smack-dab in the middle of patooky when one of the
blades comes off.

But build a new prop of your own design, sufficiently different from the
typical prop...then it doesn't matter if you put it on a certified
powerplant or the front of your Oldsmobile. Unless you have the
facilities to test it, its longevity is just guesswork.

That was a problem on some of the early T-18's that were using cut down
propellers - resonance was fatiguing the propeller which would then shed a
blade, which would then encourage the engine to attempt to part company with
the airframe...

--
Geoff
The Sea Hawk at Wow Way d0t Com
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