O-470....what are the pros and cons in cruse and climb?
I don't run over square, but have been considering it.
I also use auto fuel and that could be a factor. The 91 octane I burn seems adequate?

Just fly it he way it feels the best to you and ballance that with fuel economy. And lean the heck out of it when at 65% and below.

Tim

Some of what I have heard on newer aircraft engines. I think yours is considered newer Terry. My overhaul company wanted over square for break in. They like their engines run hard every time you take off for the life of the engine. Full throttle even at sea level

Now my opinion as a gearhead my whole life. Aircraft engine 75% to TBO I will take it easier. Mogas on 90* plus days I will take it easier.

Good day

Operating over squared on take off is pretty common, and operating over squared with a turbo variant of the same motor is SOP. I suppose reasonable limits must apply, and some enigine / prop combinations have limitations of their own. For example MT doesn't want you to run beyond 2" over squared on the O-470, but the standard adage of 'don't ever run it over square' is generally something that 250 hr CFI's preach to new commercial pilot candidates because they have yet to understand for themselves the relationship between power and RPM. I suppose they'd shat themselves if they ever saw the MP / RPM in a big round motor :lol

Most engine builders will tell you on an O-470 break in, if you have any doubt what to do with the levers, shove them all fwd .

Some good reading:
http://www.avweb.com/news/airman/184483-1.html

YMMV, Rob

Isn't the concept of "squared" just a coincidental rule of thumb anyway? There's no real mathematical or engineering correlation between manifold pressure expressed in inches of mercury, and RPM in revs per minute. It just works out with our engines that the numbers and their units of measure align and appear to be power * 100 = rpm, and that happens to be a safe/effective setting. Easy to remember for boobs like me.

Is there a power chart available for the 470 showing the factory approved settings? The usual mention for cruise is 22,23,or 24 squared, or some slightly under-squared variation on this -- 21"/2300 seems popular. I don't know if this is by choice, or by necesity due to no more MP being available at altitude.

There is an excellent series of articles on the internet about operating engines. Google "Pelican's Perch, putting it all together". Very informative!

I love BCP but when you ask questions like this you open yourself to alot of speculation by non experts like me. The bes thing you can do is Google
http://www.avweb.com/news/pelican/182081-1.html

^^ Great article link Russ, thanks for posting!

http://dixiehigh.org/~gwhicker/index_files/1969%20Lycoming%20O-470%20Engine%20Manual.pdf
Of course, they've 'updated' certain areas since, but still interesting.....

Rob wrote: 'don't ever run it over square' is generally something that 250 hr CFI's preach to new commercial pilot candidates because they have yet to understand for themselves the relationship between power and RPM. I suppose they'd shat themselves if they ever saw the MP / RPM in a big round motor

Haha isn't that true... along with every other fallacy in aviation

Right in your POH will be the charts for allowable power settings, and with the normally arpirated O-470 you can "oversquare" all day long.

Gump

Vick wrote:^^ Great article link Russ, thanks for posting!

Too much reading for me can you summarize for me Vic