Backcountry Pilot

[Battson offline]

So in talking about prop sizing for our installation I have learned a few things (perhaps obvious things), and as always more questions have come:

So the Lycoming IO-540-A4D5 taps out at 2700RPM, and the recommended prop is a 2-blade 84" of some description (yes I would LOVE the MT which solves all problems, but financial planning prevails) and that 2 blade prop would be super-sonic at the tips by 2700, it probably starts screaming around 2575-2600. I am looking at an "new in the box" McCauley on Barnstormers, 82". If you can help with these questions I'd really appreciate it:

Is running the prop supersonic for short periods (takeoff only) unacceptable from an operational standpoint in terms of safety, causing mechanical damage, or stressing the blade roots? I grew up beside a 185F with 88" and understand the effects on the neighbours....
If so, governing the engine at 2600 loses about 4%-5% hp.

Would I be better to get a slightly smaller prop and run at full horsepower, or a larger prop and run at 95% power in terms of developing maximum thrust at takeoff?

I realise this is splitting hairs to some extent, but it's as much curiosity as going for best performance.

[Glidergeek offline]

Battson do your props turn clockwise or counterclockwise down under?
http://www.pponk.com/HTML%20PAGES/propcalc.html

[Battson offline]

Awesome thanks.

So that suggests that 86"-88" is about right for 2700RPM....? (warm day)
Me thinks that would be a screamer??

Rotation direction - It depends on the day of the week, flying at Sunday midnight is exciting...
Our compasses are backwards too.