3 Blade prop RPM

[adamsboomer]

I am flying a 65 4 cylinder C with 3 blade hertzell prop.  I was wondering if the RPM caution range of 2000-2250 should still be avoided?  I typically fly 2300 RPM for effeciency as I am trying to get places but also build time for commercial.  I tried 1800 to see what endurance provided, i didnt like being that slow.  Was just curious if the 3 blade still made harmonics that need to be avoided?

 

Thanks for the responses.

Adam

[Rwsavory]

We have the same set-up.  The RPM caution range does not apply to the 3-bladed prop.  We cruise either at 2300 or 2400 RPM, which seems to be a good range for noise/vibration, performance and efficiency.      

[carusoam]

There probably is a document like the STC that technically removes the yellow arc from the rpm gauge.

A few dollars spent at the instrument shop can refresh the face of the device.

The previous owner may have kept all the important documents in one or more places?

-POH

-Logs

-STCs

Best regards,

-a-

[adamsboomer]

Thanks fellas,

I figured it was no longer necessary but thought I would double check. I will try 10k 2200 rpm next flight just cause I can.  HAHA.

[carusoam]

It is better to know than to assume.

The limitations on the original set-up are not noticeable to ordinary pilots while flying.

But, they are there for a reason...mostly expensive reasons...

Best regards,

-a-

[1964-M20E]

you can always go to the manf. with all the model and s/n and ask them if you cannot find anything in the log books.

[jrwilson]

We have the same set-up.  The RPM caution range does not apply to the 3-bladed prop.  We cruise either at 2300 or 2400 RPM, which seems to be a good range for noise/vibration, performance and efficiency.      

 

I have the 3 blade and it still applies, at least on the 63.  I have a McCaulley prop though, so maybe that is the difference...

[Guest]

According to the Hartzell top prop web site there is a new but different restriction and a required placard.

http://hartzellprop.com/products/top-prop/mooney/m20c-g-all/

Clarence

[Hank]

Interesting. Mine still has redline on the tach, 2000-2250, and the placard for no continuous operations below 15" between 1950 & 2350.

I generally run 2300 down low, 2400 from ~4000-6500, and 2500 above that.

[tony]

Hank's right, you should.  Its a function of the blade passage frequency, so you just scale it down by the ratio

[aaronk25]

At 2200rpm at 10k are you going backwards, I mean really that's got to be SLOW.......

[Cody Stallings]

@2200 RPM, what MP do you utilize?

[adamsboomer]

Thanks for the reference materials I especially appreciate the hartzell prop website.  I have never run the 2200 rpm.  Right now I am running 2300rpm and 18"MP getting 135MPH level @10K I pull back to 15" for 400vvi descent clean, looks like my new setting will be 2400 in the descent to avoid that range.  I am new to this plane and coming from a C152 so I don't mind slow for now.  Sounds like either I have a relatively light or slick plane though as I have only noticed about 5MPH decrease per 100RPM is that around what you guys are seeing at 10K?

[Hank]

When it's time to descend, I leave the throttle alone, push on the yoke for 500 fpm and trim the force away. That's my payback for the slow climb.