Climb settings on a 252

[Will.iam]

On 7/6/2021 at 7:21 AM, jlunseth said:

The desired value should be in your Pilot Operating Handbook. It is in mine. My POH requires 22.5 - 24 GPH at full power. 24 is better in a hot weather climb. I do not have your SB engine though, I have the LB.

My 252 is the MB engine i wish i had the SB engine but I can’t upgrade to that engine until i do the encore upgrade.  

[Will.iam]

On 7/6/2021 at 9:48 AM, kortopates said:

the high number should be considered the absolute minimum, preferably 0.5 to 1.0 GPH above the high number is preferred.


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Do you know why my FF goes down in the summer temperatures like 90 dF? It was perfect in winter time showing 24gph but as the temps rise my max fuel flow has gone down. 

[kortopates]

4 hours ago, Will.iam said:

Do you know why my FF goes down in the summer temperatures like 90 dF? It was perfect in winter time showing 24gph but as the temps rise my max fuel flow has gone down. 

I would have to see your data to be sure. But this normal since with the higher temps, oil temp goes up and oil temp directly affects your Max WOT MAP. FF in turn just follows your MAP. Your controller is set to achieve redline MAP right at normal oil temp of 175F, and do to the nature of hydraulic controllers working with oil pressure, you'll see overboost when the oil temp hasn't yet warmed up too full operating temp and underboost when the oil temp is over normal operating temp. Since FF is just following your MAP, if there is some underboost in the MAP (lower MAP) FF will also be lower. This is normal but you may not have your controller set exactly to give redline right at an oil temp of 175F either. Also, just like Winter vs Summer differences,  you should notice that on the first take off of the day, before oil temp is fully warmed up that MAP and FF are highest at takeoff and then a subsequent takeoff this time of year, with oil temp > greater than 175F will show a bit lower MAP and thus lower FF. Its entirely normal.

Edited July 8, 2021 by kortopates

[Parker_Woodruff]

As others have stated, with this engine you should fly max manifold and max RPM until cruise.  Enjoy!

And I highly recommend the Encore conversion coupled with a 3-blade metal Hartzell propeller for when you need a new prop.

[Will.iam]

Thanks for all the additional info. Why the 3-blade metal hartzell prop instead of the lighter TC prop? I too suffer from the nose heavy syndrome of a K model. I wish they made a light composite 2 blade prop. That way i would get the higher cruise speed and better CG for a more efficient flight. 

[Will.iam]

2 hours ago, kortopates said:

I would have to see your data to be sure. But this normal since with the higher temps, oil temp goes up and oil temp directly affects your Max WOT MAP. FF in turn just follows your MAP. Your controller is set to achieve redline MAP right at normal oil temp of 175F, and do to the nature of hydraulic controllers working with oil pressure, you'll see overboost when the oil temp hasn't yet warmed up too full operating temp and underboost when the oil temp is over normal operating temp. Since FF is just following your MAP, if there is some underboost in the MAP (lower MAP) FF will also be lower. This is normal but you may not have your controller set exactly to give redline right at an oil temp of 175F either. Also, just like Winter vs Summer differences,  you should notice that on the first take off of the day, before oil temp is fully warmed up that MAP and FF are highest at takeoff and then a subsequent takeoff this time of year, with oil temp > greater than 175F will show a bit lower MAP and thus lower FF. Its entirely normal.

this also would explain as i climb my FF pressure would drop by 2 gph. I was thinking why would it drop climbing since i have the automatic waste gate controller maintaining a constant pressure but it does drop but only by 2 and then holds that steady for the rest of the climb. Now that you explained that the oil is cooler on initial T/O and gets to operating temperature as i climb and the controller is set based on oil temperature. this explains the drop and then no further drop as i continue to climb to altitude. Thanks for the explanation.    

[shawnd]

On 7/5/2021 at 2:47 PM, LANCECASPER said:

Here's the guy that helped develop the 252 and what he has to say:

Thanks for sharing this @LANCECASPER. I recently started flying full throttle all the way to cruise after PaulK nudged me to doing so. Works like a charm! Also, the numbers pretty closely match what the Mooney Safety Foundation folks say as well.

 

PS. What was the source of that article?

[Will.iam]

Interesting that the article said they could climb at 1/2 cowl flaps. They must have been ok with temps over 400 back then because at full open cowl flaps i struggle to keep cht’s below 400 when it’s 95 dF outside. Also noticed they specified for cruise setting of 28” 2500 12.8 ff that combination on my chart sets squarely in the 78.6% 165HP section of the charts. Too bad they never revised a chart for LOP operations for 78.6% power. I like Paul’s setting of 25” 2500 9.5 ff. The TIT rises above 1550 but settles back down to right at 1550 after a few mins and is below the 65% power setting so I can’t hurt the engine if the mixture goes lean on a cyl like say a fuel injector gets partially clogged etc. My TAS  varies with altitude and temp but at 10k i usually see 150kts. Wish it was faster but with a tired engine, trying to go past TBO, im ok with the wear on the engine and turbo at that setting. 

[LANCECASPER]

5 hours ago, shawnd said:

Thanks for sharing this @LANCECASPER. I recently started flying full throttle all the way to cruise after PaulK nudged me to doing so. Works like a charm! Also, the numbers pretty closely match what the Mooney Safety Foundation folks say as well.

 

PS. What was the source of that article?

MAPA magazine

[carusoam]

56 minutes ago, Will.iam said:

They must have been ok with temps over 400 back then because at full open cowl flaps i struggle to keep cht’s below 400 when it’s 95 dF outside.

There are plenty of people that use redline for guidance…

Plenty of people that fly in flaming dragon mode…

Using 380°F is a common method to minimize cylinder wear…

 

But, is it realistic to be able to maintain 380°F in the climb?

 

Going over 400°F is not a death sentence for cylinders…

And climbing with a high powered Mooney isn’t many minutes of the flight…

Guess it comes down to how much you know about your plane… and how you want to operate it…

There aren’t any hard rules to follow…. Just some good guidance…. Use it when able…

What is the worst than can happen?   Cylinders wear out prior to TBO, or half time….

If you have to make a set of cylinders go the distance…. Fly often, and keep the CHTs low…

So many random things can occur on the way to TBO… 

PP thoughts only, not a mechanic…

Best regards,

-a-

[kortopates]

15 hours ago, Will.iam said:

Interesting that the article said they could climb at 1/2 cowl flaps. They must have been ok with temps over 400 back then because at full open cowl flaps i struggle to keep cht’s below 400 when it’s 95 dF outside.

When the air temp isn't hot as it is this time of year, climbing at 1/2 cowl flaps is standard practice for me as well and CHTs aren't even near 380F. This time of year the engines needs a lot more cooling in cruise and I am probably 1/4 to 1/3 cowl flaps closed in climb.. Its hot out there! But make sure the nose is lowered to at least 110 KIAS. Airpseed is the real cooling factor.

Edited July 12, 2021 by kortopates

[jlunseth]

Me too. There are times of the year when half cowl flaps and even no cowl flaps works fine. The key is the CHTs, I use the flaps to keep the CHTs at or under 380 if that is possible. Airspeed is also important as Paul says. There are occasionally days, usually out west in the hot days of summer, when none of that works really well and I will see one or two cylinders above 400 dF. Don't like it, but there are only so many things you can do.

[Will.iam]

Thanks guys I’m really hoping at my first annual for me with this 252 this august the A&P can find a intercooler baffle or baffling around the cowl that is not sitting correctly as it sounds like i should be able to keep the temps down lower than they are currently. 

Edited July 13, 2021 by Will.iam
Misspelled word from auto correct.

[jlunseth]

I should clarify that my climb outs are nearly always with cowl flaps full open. In the winter it gets so cold here sometimes that it is necessary to protect the engine in the opposite direction from summer. Fall climbouts with the temps in the 40s F or cooler might be half cowl flaps, you will quickly be in below freezing temps just a couple thousand feet up. Real winter temps where we can be 20 dF down to -35 dF on the ground and the air is very dense, it is very important to keep the engine compartment as warm as possible, so I might climb with no cowl flaps at all. Can't let the OT fall below 100 dF and I have one cylinder that likes to run cold, below normal operating temp of 240.

[Will.iam]

1 hour ago, jlunseth said:

I should clarify that my climb outs are nearly always with cowl flaps full open. In the winter it gets so cold here sometimes that it is necessary to protect the engine in the opposite direction from summer. Fall climbouts with the temps in the 40s F or cooler might be half cowl flaps, you will quickly be in below freezing temps just a couple thousand feet up. Real winter temps where we can be 20 dF down to -35 dF on the ground and the air is very dense, it is very important to keep the engine compartment as warm as possible, so I might climb with no cowl flaps at all. Can't let the OT fall below 100 dF and I have one cylinder that likes to run cold, below normal operating temp of 240.

That wouldn’t be cyl #2 would it? I have that one that runs 40d cooler than the rest and i keep hoping that is the one that has the piggy back sensor since I don’t have a jpi primary instrument for chts. Eventually i will get a jpi 900 just have higher priorities this first annual that have to be addressed like starter adapter overhaul and surefly ignition. 

[jlunseth]

No, my cold cylinder is 6, it sits right in the intake hole. You are lucky if your 2 is cold, that is hiding in the back behind all the other cylinders, last to get cooling air.

[Warren]

In my 231, #2 routinely runs much cooler.  40-50 below the average of the other cylinders.  I have checked baffling, checked spark plugs, measured gami sweeps and still can find no logical reason for it to run so cool.  On my engine, the piggyback sensor is on #5 so I know it is not this.  Not sure where the factory sensor is on the 252.

[carusoam]

Will…

if you are having difficulty with an intercooler and related baffling…

We have an intercooler guy and a baffle seal guy around here…

Both have been incredibly helpful for MSers…

Best regards,

-a-

[shawnd]

11 hours ago, Will.iam said:

Thanks guys I’m really hoping at my first annual for me with this 252 this august the A&P can find a intercooler baffle or baffling around the cowl that is not sitting correctly as it sounds like i should be able to keep the temps down lower than they are currently. 

Might be a good idea to take some a look under the cowling through the openings in the front and checking if there are gaps between the baffle seal and the cowling. If there are, the top of the engine wouldn't build up air pressure which then forces air down by the cylinders to the bottom of the engine. This is what cools the cylinders. Instead air will blow past the baffle over the seals and "leak" to the back of the engine or around the engine cowling to the bottom. As you can imagine, that doesn't help cool things down.

You can put a flash light from one of the openings and your phone through the other and take some photos. Easy thing to check before moving forward. If you do notice gaps, and want to replace the engine baffle seals - check with @GEE-BEE AEROPRODUCTS. His pre-cut seals are recommended as you can stretch them properly to give it the right curve so that it always folds forward the right way when putting on the cowling. I personally found the McFarlane seals, although very high quality and slippery, hard to achieve the right curve.

Here's mine I did this year:

 

As you can tell, we love photos on MS - so do post photos :-)

[shawnd]

30 minutes ago, Warren said:

In my 231, #2 routinely runs much cooler.  40-50 below the average of the other cylinders.  I have checked baffling, checked spark plugs, measured gami sweeps and still can find no logical reason for it to run so cool.  On my engine, the piggyback sensor is on #5 so I know it is not this.  Not sure where the factory sensor is on the 252.

Factory sensor on my 252 was installed on cylinder #2.

My engine also tends to run cool, even with old hard baffle seals. After suggestion from a local pilot, at 78% power and leaned ROP, I can now maintain 330-370 in cruise. This is now my go-to setting. Enjoy cool running engines when able. Usually its the other way round.