2500 RPM Cruise

[Newmooneyguy]

I have a 3 blade prop, and 2500 rpm is a bit less vibration than 2400. Is sustained cruise at 2500 OK?

[jetdriven]

Sustained cruise at 2700 RPM is OK.  Its in the manual too.

[jelswick]

I'm not expert at various combinations of props or engine sizes, but I have a 201 with two blade prop and asked the Mooney rep one year at Oshkosh about best settings and he told me 25 squared is a sweet spot for Mooneys, at least mine from a speed and vibration standpoint.  He told me basically to firewall it on take off and leave it there until reaching cruise altitude (I'd always previously reduced it to 25 squared shortly after getting to about pattern altitude).  I don't think all, but some do have a yellow line on the RPM that you're not supposed to go into for any sustained period.  I know if I let it get into that on landing the vibration is very noticeable, not horrible, but enough to recognize I've let it get that low and get it back to just above that setting. 

[scottfromiowa]

2500 RPM IS my cruise RPM.  I also have a three blade prop.

[KSMooniac]

"25 squared" is such a silly and antiquated power setting for those that don't know.  What does the "25 squared" crowd set for cruise at 8,000' (in a non-turbo plane)?  

[jetdriven]

I bet it ain't 30" and 2200 RPM!    And that is actually a low cruise power setting in a PA-31-350 Cheiftain. 

[scottfromiowa]

i guess I'm NOT silly 'cause I can't get 25 inches of MP at 8,000'...

[danb35]

Quote: jelswick

He told me basically to firewall it on take off and leave it there until reaching cruise altitude (I'd always previously reduced it to 25 squared shortly after getting to about pattern altitude).

[jetdriven]

If you limit FF to 10.0 GPH that limits power to 75%.  Useful below 5000 feet.

[jelswick]

Good point about the squared at altitude.  Yes of course it depends on altitude and can't get 25" above about 5-7K feet in mine depending on density altitude which is why I'm guessing the comment about leaving throttle firewalled.  Just running around Ohio or next over states at those altitudes, 25 squared works for me leaned to around 11.5 ff and I'm consistently getting TAS according to the Aspens of 160-165, calibrating the temp/alt on the other airspeed indicators agrees with those numbers.