252 Cruise Power Schedule?

[Rick7576]

252 Cruise Power Schedule?

Looking at the 252 POH  “Cruise Power Schedule”

Looking for the best explanation on cruise power schedule.  Can anyone explain what power settings are best for eng. Longevity, Best speed, and any other explanation you can come up with.

Example:  At 12,000 ft. -9 C   65% per. (136.5 BHP)

    2200 RPM          10.5 GPH             26.9  MP                                                                                                                                                                                                                                          2400 RPM          11.0 GPH             24.6  MP                                                                                                                                                                                                                                  2600 RPM          11.0 GPH             23.1  MP

These charts are for 78% 70% 65% 60% 55% all the way down to 35%     All are for running engines lean of peak. And standard temperature.

I’m just trying to find out whats best for long eng. life!!!!!           Ready fire aim !!!                       Cheers  Rick

 

Edited April 12, 2020 by Rick7576
line up the numbers

[carusoam]

Rick,

Starting with ‘schedule’ that is a fancy name for a chart...

A chart of MP, RPM, TIT, °F (LOP or ROP), %hp...

from the book of common practice...   Low power, LOP is best for engine life...

How much time do you have to keep your engine in top condition...? (read this in at least two different ways)

Running anywhere high power (above 65%) near peak would be bad...

 

There is lots of room for judgement...

there is no one true answer...

There is one true flaming dragon mode... great for max speed all the time.... at the cost of a set of cylinders every 1000 hours or so... but that is an ordinary practice for some...

Stand by for other TC’d Mooney drivers to fill in how they operate their engines...

Keep in mind there  are a few threads around here about operating TC’d Mooneys that cover lots of ground... this will help you form really tough questions...  

Find some writing from an MSer named Paul... @gsxrpilot he is technically talented, writes plenty, owns a 252...

Best regards,

-a-

 

 

[MooneyMitch]

Non-engine specific recommendations for engine longevity.....follow correct engine operating procedures, perform regular maintenance and FLY regularly and consistently.  

My experience only.

[MooneyMitch]

6 minutes ago, carusoam said:

Rick,

Starting with ‘schedule’ that is a fancy name for a chart...

A chart of MP, RPM, TIT, °F (LOP or ROP), %hp...

from the book of common practice...   Low power, LOP is best for engine life...

How much time do you have to keep your engine in top condition...? (read this in at least two different ways)

Running anywhere high power (above 65%) near peak would be bad...

 

There is lots of room for judgement...

there is no one true answer...

There is one true flaming dragon mode... great for max speed all the time.... at the cost of a set of cylinders every 1000 hours or so... but that is an ordinary practice for some...

Stand by for other TC’d Mooney drivers to fill in how they operate their engines...

Keep in mind there  are a few threads around here about operating TC’d Mooneys that cover lots of ground... this will help you form really tough questions...  

Find some writing from an MSer named Paul... @gsxrpilot he is technically talented, writes plenty, owns a 252...

Best regards,

-a-

 

 

And Paul Kortapates.

[gsxrpilot]

I'm a veritable newbie compared to the other Paul @kortopates who owns a 252, is a CFI, A&P/IA, with both Mooney and Savvy on his employment resume.

But I do fly a 252 and have been pretty successful with it so far. I'm at about 1600 hours on the original cylinders and turbo. I think power settings on a turbo are much easier than a NA engine. The turbo doesn't care about the altitude. So that variable can be ignored. One note, I have a JPI EDM900 engine monitor that displays %HP and I use that figure to help with my engine management. So here it is...

Climb - Full, Full, Full (Or close to that.) I'll typically climb from the runway to my cruising altitude regardless of how high that is at 36" 2700 26gph. 

Cruise - Set MAP at 65%HP or about 26", 2500 RPM, and pull the mixture back to 9.5 gph. That gives me a very gentle 62% power at about 30° LOP.

ROP Cruise - I use this very rarely as it is a lot more fuel for not much more speed. 29" MAP 2500 RPM 14.5 gph.

Descent - Same as Cruise, just trim the nose down and go fast.

[kortopates]

Paul @gsxrpilot gives great advice on safe power settings to promote longevity above.

When it really comes down to it, its not the power setting that get's us into trouble but rather its how we lean! With a turbo its possible to burn up an engine in literally seconds with improper leaning. Can't do it that fast in a NA aircraft and you can't do it at all at altitude in a NA aircraft.

With the turbo its critical to operate at full rich while above max cruise power settings which will be the full power take off and climb. Like Paul above, I prefer WOT to what ever cruise altitude I need. But if you use cruise climb power keep it full rich as well. (No leaning till % power is at or below max cruise power.) I'd rather lower the nose a bit at WOT and climb at around 120 kts to my cruise altitude than reduce power in the climb. (Operating a bigger engines like the fire breathing Acclaim I would reduce power in the climb.)

In cruise (and descent) is where leaning gets critical, since to protect the engine, we need to be a certain number degrees richer than peak when operating ROP and a certain number of degrees lean of peak when operating LOP. We do that to keep out of the "red box" of harmful ICP (internal combustion pressure) when the engine is operating at 65% or above. So that is the beauty of operating just below 65% since the redbox is gone and we can't hurt the engine wherever we leave the mixture. But with a couple caveats, while meeting that target mixture setting whether ROP or LOP, we also don't want CHTs above 400F (many will limit to 380F - pick your personal cutoff) and TITs in excess of 1600F (I pick 1580F for a little buffer). So learn all about leaning at the lower power settings up into the low's 60's%. That's kinder for this engine as well since its relatively small engine for what we're asking from it afms-gamijectors rev ir.pdf - but that also results in very efficient low fuel burns at high cruise speeds when we climb up to altitude.

For how to set mixture, there are many articles out there but Gami's FAA approved AFMS for their injectors is about the best guidance you'll find anywhere and conservative as well. I've attached it here.

Now go read up on how to manage your mixture applying the concepts for both mixture management that you can read here in MS as well as many great articles on avweb by Busch and Deakin. Learn it solidly before venturing to cruise power settings above 65%. It goes without saying if you really are serious about treating your engine kindly and learning to be in a position to hear your engine when its speaking to you, that having a modern engine analyzer with FF and all the other sensors (at least a EDM-830 or equivalent) is essential and your first priority if you don't already have one. 

Incidentally above the OP says "All are for running engines lean of peak" - i think you meant All are "running at peak". That's really bad advice for engine longevity till you're at a power setting below 65% but it results in a very efficient fuel burn and long range and thus exactly what the marketing folks wanted for numbers to sell airplanes. As an owner though your priorities are different even though we all bought Mooney's for speed and efficiency.

afms-gamijectors rev ir.pdf

[Stephen]

On 4/12/2020 at 1:07 PM, gsxrpilot said:

 

 

1) Cruise - Set MAP at 65%HP or about 26", 2500 RPM, and pull the mixture back to 9.5 gph. That gives me a very gentle 62% power at about 30° LOP.

2) ROP Cruise - I use this very rarely as it is a lot more fuel for not much more speed. 29" MAP 2500 RPM 14.5 gph

 

 

Paul, 

 

Could you share what airspeed you typically true-out at for the above settings (understood there will be altitude and OAT dependency scenarios). 

[gsxrpilot]

5 minutes ago, Stephen said:

Could you share what airspeed you typically true-out at for the above settings (understood there will be altitude and OAT dependency scenarios). 

 

5 minutes ago, Stephen said:

1) Cruise - Set MAP at 65%HP or about 26", 2500 RPM, and pull the mixture back to 9.5 gph. That gives me a very gentle 62% power at about 30° LOP.

2) ROP Cruise - I use this very rarely as it is a lot more fuel for not much more speed. 29" MAP 2500 RPM 14.5 gph

With the turbo, the higher you go the faster you go and the engine settings and fuel flow don't change. But here's some data, all TAS. These are all individual flights so not an average.

10,000 - ROP 167, LOP 152

12,000 - ROP 173, LOP 158

18,000 - ROP 185, LOP 173

20,000 - ROP 191,  LOP 177

25,000 - ROP 202, LOP 188

 

[Stephen]

Very interesting numbers the efficiency is pretty amazing in the flight levels.