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New to me 47 140 Question
Posted: Thu May 03, 2018 4:58 pm
by 8209
What pitch determines cruise prop vs climb prop? C-85 engine
Thanks,
Brent
Re: New to me 47 140 Question
Posted: Thu May 03, 2018 9:30 pm
by 6643
Well, it depends... If you have a McCauley metal prop, 71" long, then the rule of thumb is 46" is climb and 50" is cruise. In general, a climb prop is the one that gets you the highest allowable static RPM whereas the cruise prop is the one that gets you the minimum static RPM.
Re: New to me 47 140 Question
Posted: Fri May 04, 2018 6:35 am
by 8209
Thank you very much, that's exactly what I wanted to know. Mine is a 71/46. My static rpm is around 2100 and I wanted to make sure I was chasing the right thing. The prop should be good, the rpm just seems a bit low.
Thanks again,
Brent
Re: New to me 47 140 Question
Posted: Fri May 04, 2018 7:33 am
by 6643
First thing to check is the tach. It's basically a 70 year old automotive speedometer...
Some props have been re-pitched but not remarked with the new pitch. Check your logs, 337's and look on the prop hub for any marking, like P1 or P+, to indicate it has been re-pitched.
Re: New to me 47 140 Question
Posted: Fri May 04, 2018 8:53 pm
by 8209
Thank you. Yes I will be double checking the rpm with an electronic tach tomorrow. Great advice.