operating at low RPM

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awash2002
A2A ACE
Posts: 2977
Joined: 01 Aug 2013
Location: KCZL

operating at low RPM

Post awash2002 »

What advantages will I get by running the Bonanza at a low rpm say 2300 to 2100 or even 2000 rpm?
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DHenriquesA2A
A2A Chief Pilot
Posts: 5442
Joined: 27 Mar 2009
Location: East Coast United States

Re: operating at low RPM

Post DHenriquesA2A »

awash2002 wrote:
12 Dec 2022, 18:30
What advantages will I get by running the Bonanza at a low rpm say 2300 to 2100 or even 2000 rpm?
There is nothing wrong with operating a modern aircraft engine oversquare. There are limits however and that means the number one rule for proper engine care and performance is to read the POH carefully and just stay within the recommended limits.

As for A2A and our coding. We coded the Bo using the engine manufacturer's recommendations for engine operation. Use the manual or if available get the manufacturer's recommendations for power settings. You will see immediately that oversquare settings are common. Just don't exceed them.
Dudley Henriques

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Piper_EEWL
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Location: Germany

Re: operating at low RPM

Post Piper_EEWL »

I think one of the advantages will be that it’s going to be quieter in the cabin due to the lower rpm. So if you can achieve your desired power setting at lower rpm I would always go for that.

That’s how I do it in real life with constant speed propeller airplanes as well.
B377&COTS, J3 Cub, B-17G, Spitfire, P-40, P-51D, C172, C182, Pa28, Pa24, T-6 Texan, L-049&COTS, Bonanza V35B

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Paughco
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Joined: 30 Nov 2014

Re: operating at low RPM

Post Paughco »

I wouldn't cruise at less than 2,300 rpm. Check out Continental's TCM SB07-08A: https://www.peter2000.co.uk/aviation/en ... B07-8A.pdf.

Here's the gist of it:

Teledyne Continental Motors (TCM) has examined recent occurrences of crankshaft counterweight
release and consequent engine stoppage with four high time IO and TSIO-520 engine models. Initial
investigation and service history lead us to believe that these occurrences are associated with engine
operation at sustained cruise engine speeds of less than 2300 RPM. While power settings of less than
2300 RPM are within the recommended cruise range allowed by TCM’s model Specifications, TCM
believes that the population of aircraft (equipped with the affected engine models) that operate using the
aforementioned low RPM for extended cruise operation is limited. TCM will continue to evaluate the
root cause of the counterweight release including any connection with power settings. TCM is not aware
of any other confirmed occurrences of this type.

Effective immediately, TCM strongly recommends the following limitation be observed
on all the models affected above:
Engine cruise RPM settings should be no lower than 2300 RPM.

Seeya
ATB
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AKar
A2A Mechanic
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Joined: 26 May 2013

Re: operating at low RPM

Post AKar »

Paughco wrote:
13 Dec 2022, 19:08
I wouldn't cruise at less than 2,300 rpm. Check out Continental's TCM SB07-08A: https://www.peter2000.co.uk/aviation/en ... B07-8A.pdf.
The publication in question has since been superseded and elevated to "Critical Service Bulletin" CSB09-11A.

To my knowledge, not much has been written or discussed over the alleged issue. Curiously, Lycoming, on the other hand, warns us to "[...] avoid high engine speed, low manifold pressure operation." I guess there are various ways to have issues with the crankshaft counterweights.

-Esa

awash2002
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Location: KCZL

Re: operating at low RPM

Post awash2002 »

I'll stick to 2300 rpm since I can set it up initially at 75% cruise power at 2500 rpm and just pull it back to 2300 rpm and just take what that rpm setting gives me
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