Propeller RPM higher than 2575 on takeoff

[SuperSmash]

Hey folks! Recent Bravo owner, was hoping you all could give me some insight. On takeoff with full forward throttle, prop, and mixture, I'm getting RPM in the 2610 range, POH says it should be 2575. So, I pull the prop back slightly to make 2575. Curious if others have to do the same, or if it's actually something I should be concerned about to bring up to the mechanic.

Thanks!

[alextstone]

That small exceedance would never have been identified using the OEM RPM gauge so I'm assuming you have a digital one.  In any case, it's negligible.

 

I've heard rumors that some pilots manage to talk their mechanics into "tuning" the prop governor such that there prop spins at 2700 on takeoff to gain a bit more horsepower.

[Z W]

There is an adjustable screw on your prop governor that will decrease your max RPM.  Simple enough to have adjusted next time it's in the shop.

[Fritz1]

Welcome aboard, probably varies from takeoff to takeoff, tolerance in the instrument, cycle pro governor at least 3x, better 5x, I like oil at 160F for takeoff, max transient rpm is 2700, a well known dealer in TX is rumored to run his personal Bravo at 2700 for takeoff, if it really bothers you, one turn on the prop governor adjustment screw is 25 rpm, personally I would leave it alone and rather err a tad on the high side, takeoff acceleration on the Bravo does not exactly knock you unconscious

[SuperSmash]

Wow, thank you guys so much! Glad it doesn't cause any extreme stresses then; I guess I'll take and appreciate that little extra bit of power. I also start cycling it 3x rather than just once.

Much appreciated!

[LANCECASPER]

9 hours ago, SuperSmash said:

I also start cycling it 3x rather than just once.

Why?

Your POH just says to cycle it. Doing it more than once just stirs up more things to nick your prop.

[SuperSmash]

On 10/11/2023 at 7:22 AM, Fritz1 said:

Welcome aboard, probably varies from takeoff to takeoff, tolerance in the instrument, cycle pro governor at least 3x, better 5x

Hmm, I guess the question then is for Fritz, why do you cycle it multiple times?

[Rick Junkin]

On 10/11/2023 at 9:22 AM, Fritz1 said:

Welcome aboard, probably varies from takeoff to takeoff, tolerance in the instrument, cycle pro governor at least 3x, better 5x, I like oil at 160F for takeoff, max transient rpm is 2700, a well known dealer in TX is rumored to run his personal Bravo at 2700 for takeoff, if it really bothers you, one turn on the prop governor adjustment screw is 25 rpm, personally I would leave it alone and rather err a tad on the high side, takeoff acceleration on the Bravo does not exactly knock you unconscious

Here, I’m gifting you a period “.”.  Feel free to reuse it as many times as you like. 

I’m curious about your rationale for cycling the prop so many times, and what magnitude of RPM drop you look for with each cycle. I’m at the other end of the spectrum and only cycle once with minimum RPM drop with the rationale that the check is to verify oil flow to the governor. That’s when I’m flying the airplane at least weekly. If the airplane has been sitting for awhile it may take a few cycles to get the prop response I expect to see but I still keep the RPM drop to about 200 RPM or less. 

But I’m always open to hearing other ideas!

Cheers,
Rick

[Rick Junkin]

On 10/11/2023 at 2:15 AM, SuperSmash said:

So, I pull the prop back slightly to make 2575.

@SuperSmash Greetings! Always lots to learn with a new-to-you airplane. Exciting times.

My governor overshoots a bit occasionally but always well below the 2700 transient limit and I don’t mess with it on takeoff. I’ll start dialing things back once I’m up and away and configured for climb, and that’s my recommendation. You’ll find different techniques for climb power settings as well.

Bob Kromer, former Mooney test pilot and CEO, advocates leaving everything firewalled until reaching cruise altitude. That assumes you’re able to keep your CHTs under control at full power in the climb which you can usually do with airspeed and cowl flap adjustments. I learned the book numbers in my transition training and that’s what I use, but really for no good reason other than that’s how I was taught to do it. And it’s what’s in the book . But you’re probably finding there are a few things in the book that you shouldn’t do. Things like running high power at peak EGT, and using TIT and CHT redlines of 1750 and 500 respectively. But I digress.

If you don’t already, you’re going to love your Bravo.

Cheers,
Rick

[Marc_B]

Transient 10-20 RPM over max RPM used to worry me more until I looked at the categories of true "Overspeed" categories.  Now I just dial it back to max RPM when I get a chance.  It's also something you can look for on your engine monitor data to see if you're actually making Max RPM and Max MP on take off.

For Category I overspeed (below), the manual recommends "If the duration of the overspeed event is less than ten seconds, no action is required. If the
overspeed event persists longer than 10 seconds, land the plane and perform the following inspection..." and details the inspection.

[LANCECASPER]

On 10/11/2023 at 8:22 AM, Fritz1 said:

Welcome aboard, probably varies from takeoff to takeoff, tolerance in the instrument, cycle pro governor at least 3x, better 5x, I like oil at 160F for takeoff, max transient rpm is 2700, a well known dealer in TX is rumored to run his personal Bravo at 2700 for takeoff, if it really bothers you, one turn on the prop governor adjustment screw is 25 rpm, personally I would leave it alone and rather err a tad on the high side, takeoff acceleration on the Bravo does not exactly knock you unconscious

And why 160 degrees for the oil when the POH says 100 degrees before take-off?

[SuperSmash]

56 minutes ago, Rick Junkin said:

@SuperSmash Greetings! Always lots to learn with a new-to-you airplane. Exciting times.

My governor overshoots a bit occasionally but always well below the 2700 transient limit and I don’t mess with it on takeoff. I’ll start dialing things back once I’m up and away and configured for climb, and that’s my recommendation. You’ll find different techniques for climb power settings as well.

Bob Kromer, former Mooney test pilot and CEO, advocates leaving everything firewalled until reaching cruise altitude. That assumes you’re able to keep your CHTs under control at full power in the climb which you can usually do with airspeed and cowl flap adjustments. I learned the book numbers in my transition training and that’s what I use, but really for no good reason other than that’s how I was taught to do it. And it’s what’s in the book . But you’re probably finding there are a few things in the book that you shouldn’t do. Things like running high power at peak EGT, and using TIT and CHT redlines of 1750 and 500 respectively. But I digress.

If you don’t already, you’re going to love your Bravo.

Cheers,
Rick

Thank you! Yes definitely paying attention to the engine running tips folks have shared that are different from the POH's recommendations. Cruise I'm doing 30'/2400, which I believe is Bob Kroner's recommendation for turbo Mooneys from a while back.

[SuperSmash]

23 minutes ago, Marc_B said:

Transient 10-20 RPM over max RPM used to worry me more until I looked at the categories of true "Overspeed" categories.  Now I just dial it back to max RPM when I get a chance.  It's also something you can look for on your engine monitor data to see if you're actually making Max RPM and Max MP on take off.

For Category I overspeed (below), the manual recommends "If the duration of the overspeed event is less than ten seconds, no action is required. If the
overspeed event persists longer than 10 seconds, land the plane and perform the following inspection..." and details the inspection.

Thanks for sharing! I dug up Lycoming's similar chart concerning the TIO-540 AF1B, looks like it says 2575 for continuous but doesn't have a takeoff number...

Edited October 12, 2023 by SuperSmash

[tmo]

Thse are two different charts - the Conti one is "overspeed" and the Lyco one you posted is "rated" and only refers to a RPM from which you should compute overspeed - the formula for which is possibly on a previous or subsequent page.

Thank you for the Conti one, will make me sleep better, I get a slight overspeed above 2700 at times as well.

Edited October 12, 2023 by tmo

[jaylw314]

4 hours ago, Rick Junkin said:

Here, I’m gifting you a period “.”.  Feel free to reuse it as many times as you like. 

I’m curious about your rationale for cycling the prop so many times, and what magnitude of RPM drop you look for with each cycle. I’m at the other end of the spectrum and only cycle once with minimum RPM drop with the rationale that the check is to verify oil flow to the governor. That’s when I’m flying the airplane at least weekly. If the airplane has been sitting for awhile it may take a few cycles to get the prop response I expect to see but I still keep the RPM drop to about 200 RPM or less. 

But I’m always open to hearing other ideas!

Cheers,
Rick

I cycle the prop twice, even though I know I only need to do it once.  The second time is to convince myself the first one wasn't just in my imagination

 

[Fritz1]

cycling the prop once does not do it for me, use 100W oil, want warm oil in the prop for takeoff, feels like I need at least two cycles to get quick governor response, also feels like density controller needs at least 160 F do do its job on takeoff, otherwise boost too high when OAT cold and not enough boost increase when OAT hot, density controller just works better when oil above 160F

[LANCECASPER]

3 hours ago, Fritz1 said:

cycling the prop once does not do it for me, use 100W oil, want warm oil in the prop for takeoff, feels like I need at least two cycles to get quick governor response, also feels like density controller needs at least 160 F do do its job on takeoff, otherwise boost too high when OAT cold and not enough boost increase when OAT hot, density controller just works better when oil above 160F

Aeroshell 100 is a straight 50 SAE weight, not 100W.

 

Section VIII of your M20M POH, page 8 - 5,  recommends a multi-weight, not a straight weight, either 15W-50 or 20W-50

Since you're in a turbocharged airplane that operates at a wide variety of outside temperatures at different altitudes why not use a multi-weight oil?

[Fritz1]

Use Shell W100Plus, had the Shell 15W50 for a while, did not like it, too much additives for my taste, 25h oil changes, put in a quart of MMO before oil change, find more carbon particles in the filter when I use the MMO for cleaning, fly for at least 45 min with the MMO, to my best understanding the main purpose of the multi viscosity oil is cold start lubrication, I preheat below 70F, with cold start eliminated I do not see need for multi viscosity oil, think single weight weight W100Plus performs better in everything but cold start, if I had to use multi weight I think I would use the Phillips XC, semi synthetic, less additives than the Shell 15W50, the response of the density controller is about the same with multi weight and single weight, think it needs at least 160F oil temp by design to work correctly, my personal experience running the Bravo for 6 years, typically 120h per year, certainly curious to hear other opinions and learn something

[LANCECASPER]

1 hour ago, Fritz1 said:

Use Shell W100Plus, had the Shell 15W50 for a while, did not like it, too much additives for my taste, 25h oil changes, put in a quart of MMO before oil change, find more carbon particles in the filter when I use the MMO for cleaning, fly for at least 45 min with the MMO, to my best understanding the main purpose of the multi viscosity oil is cold start lubrication, I preheat below 70F, with cold start eliminated I do not see need for multi viscosity oil, think single weight weight W100Plus performs better in everything but cold start, if I had to use multi weight I think I would use the Phillips XC, semi synthetic, less additives than the Shell 15W50, the response of the density controller is about the same with multi weight and single weight, think it needs at least 160F oil temp by design to work correctly, my personal experience running the Bravo for 6 years, typically 120h per year, certainly curious to hear other opinions and learn something

MMO is mainly a solvent (mineral spirits and stoddard), so yes it cleans, but since it's neither FAA approved nor tested and it lowers the viscosity of your oil, what effect does that mixture of oil and solvent have on your prop governor or your turbo bearings?

Phillips XC is not semi synthetic, it's an ashless dispersant mineral based oil with detergents.

Lycoming doesn't recommend single weight for the TIO-540-AF1B engine (Service Instruction 1014N dated July 29, 2020)

A. MULTIGRADE OILS – Multigrade oils, also known as multi-weight oils, are recommended for aircraft engines subjected to wide variations of ambient temperature, particularly for turbocharged engines that use engine oil to activate various turbo controllers. Multigrade oils exist as both non-dispersant and ashless dispersant types. Multigrade oils contain additives in order for the oil to maintain its viscosity through a broader range of operating temperatures than straight weight oils. The additives in multigrade oil extend operating temperature range, improve cold-weather starting, and provide superior lubrication of the engine during the critical warm-up period. Multigrade oil allows flight through wider ranges of climatic changes without the need to change oil. Do not assume that multigrade oils will alleviate all problems encountered in extremely cold environments. At temperatures below +10°F (-12°C), Lycoming recommends pre-heating the engine and oil supply tank regardless of the type of oil used. Refer to the latest revision of Lycoming Engines’ Service Instruction No. 1505 for further information regarding pre-heating the engine.

[Fritz1]

Good point, will look into it, maybe the Phillips XC is the best oil for the Bravo engine, subtle balance

[jetdriven]

1. Lycoming says 5% or less overspeed, correct the problem. Above 10% more involved things happen. But 2575 * 1.05 is 2703 RPM. So, not as big a thing as it may seem.