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Climb Power Setting


Glen Davis

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My J is new to me, about a month. The book says climb power after takeoff should be reduced to 26 square.  My check-out instructor suggested 25 square.  Any thoughts or suggestions?  Will 26 square and a climb at 500 FPM create CHT's too high?

Thanks

Glen

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Do you have an engine monitor in your plane? 

I climb WOT, roll the RPM back to 2650 until I get to my desired altitude unless I am trying to reduce noise for the neighbors then I'll roll the RPM back to 2500 until I clear the noise area then back to 2650 and continue my climb.

Depending on my final altitude, >= 5000, once at cruise altitude all I do is roll back the RPM to 2550 and lean it out.

If you are experiencing high CHTs early in your climb you might check your fuel flow at take off on the ground.

If you really want to start some conversation start into LOP vs ROP.

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49 minutes ago, Glen Davis said:

My J is new to me, about a month. The book says climb power after takeoff should be reduced to 26 square.  My check-out instructor suggested 25 square.  Any thoughts or suggestions?  Will 26 square and a climb at 500 FPM create CHT's too high?

Thanks

Glen

In my J I use WOT until at cruise altitude and just wind the prop back to 2600 after I'm 1000' AGL.  I rarely have trouble with CHTs being too high except occasionally in the summer months when it is 95+ degrees and then I still leave the engine setup the same but just lower the nose a little bit to increase airflow.

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This is a lot like asking how fast you should drive down the highway.  There are some limits, but as long as you're within those, do whatever you want.  Are some speeds more efficient than others? Yep.  Are some speeds faster than others? Yep.  Does it make you wrong if you don't drive the fastest or most efficient speed? Nope.

That said, unless you have high CHT's, full throttle and max RPM gives you the most power and will get you to your cruise altitude the fastest.  Some say that is also the most efficient since you can reduce power for cruise sooner.  I believe the current school of thought is that there is no benefit to reducing RPM during climb, but also no harm.

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Well everyone above pretty much covered it.  The 26/26 or 25/25 thing is basically an old wives tale.  You can leave wide open throttle and 2700rpm. I tend to go to 2600rpm for noise reduction but that’s not required.  The engine is good at 2700 continuous.  Now you probably want to cruise around 75%power or less, but if you climb to 5 or 6,000’, the thinner air will take care of that for you. 

You do need to keep an eye on CHTs but you shouldn’t have to reduce power unless there’s something wrong with your setup.  If you have good fuel flow (starting full rich) and you climb at a good airspeed (I like 120mph) and your baffles are good, then you will have CHTs around 350-380 during climb depending on outside temps.

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I'll +1 that full throttle and a comfortable rpm is a fine way to operate a fuel-injected, naturally-aspirated Mooney.   I climb at either full-forward (usually about 2680) or 2600 rpm and typically cruise at 2500 rpm.   Throttle goes to full at takeoff and generally stays there until descent to landing (this technique is blessed by Mike Busch, fwiw).

CHTs can usually be managed with the cowl flaps.   Sometimes in the summer I need to leave them 1/2 open at cruise once in a while, but usually once I'm at cruise they can be closed and the CHTs will be about where they should be.   During climb they should be full open or 1/2 open if CHTs get on the cold side.    Mixture settings will naturally also affect CHTs.

If you can't manage your CHTs with the cowl flaps, the first thing to do is make sure your engine baffling and baffle gaskets are in good condition and are where they should be, and other things affecting air flow (e.g., cowl flap rigging) are where they should be as well.

Edited by EricJ
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1 hour ago, 201Mooniac said:

In my J I use WOT until at cruise altitude and just wind the prop back to 2600 after I'm 1000' AGL.  I rarely have trouble with CHTs being too high except occasionally in the summer months when it is 95+ degrees and then I still leave the engine setup the same but just lower the nose a little bit to increase airflow.

This is similar to my procedure. WOT until descent.  I dial Rpm back to 2600 after 1,000’ for noise and cruise at 2500 RPM.  Also reduce fuel flow in climb  to maintain takeoff EGT.  Lee

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Hmmm...

Is it too late to get a different Transition Trainer?

1) It helps to have an engine monitor...

2) it helps to have a FF instrument...

3) it helps to know your Gami spread...

4) it helps to know what your engine monitor is telling you during the run-up...

5) It helps to know what the results of the inflight mag check were...

6) Were you still running full rich through the climb?

7) With normally aspirated Mooney engines... Most Often full power is used to climb, keeping the mixture ROP by about 2-300 °F, as determined by the EGT...

8) Power comes down quickly as altitude is gained...

9) RPM is typically set to a nice smooth setting to avoid noise and excess vibration....

There is soooo much to know... transition Training is a great way to start.... a really good safe way to start...
 

Just a few more details to pick up in the first year...

ya know?  :)

PP thoughts only, not a CFI...
 

Best regards,

-a-

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WOT and 2700 RPM, full rich at sea level, use "target egt" to lean on the way up starting at around 3000' density altitude. 25 square destroys your climb performance. Fly the Vz profile, lots of posts here on that, basically 1.3 * Vy or 115 KIAS to start.

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I have a good presentation on Vz now, am crunching a video to be Mooneyspace friendly for the files section. The presentation as I recorded it a couple weeks ago was almost 4 gb at full resolution. Will make a new post when it is up. About 57 minutes long.

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For NA powered engines -

According to former Mooney test pilot Bob Kromer, after takeoff power is applied, leave the throttle and RPM as is until at cruise altitude.  Anything less is costing you prop efficiency and performance.  Don’t forget to lean in the climb.

Bob also says that 105 KIAS is the most efficient climb speed in reference to the Mooney wing.

I do almost all of the above except for the climb speed as I prefer cooler cylinders by setting a 500 FPM ROC on the AP until cruise.

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I do something close to Vz, WOT 2700rpm. Keep target EGT close to takeoff which will put you near 200 ROP - lean to that target as you climb out.  

There are a lot of things from the 1970s that are flat wrong that make it into the POH.  
 

Ask your CFI why 25/25 and I bet he/she couldn’t actually give you a reason. The only actual reason is noise. I’ve done comparison testing and the only thing that 25/25 does compared to WOT/27 is decrease your VSI by about 150 fpm.  
 

I consider initial climbing a critical phase of flight where I want to get up to a glideable altitude as quickly as possible.  I’ll take that extra 150-200 fpm 

 

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10 hours ago, Mooney in Oz said:

For NA powered engines -

According to former Mooney test pilot Bob Kromer, after takeoff power is applied, leave the throttle and RPM as is until at cruise altitude.  Anything less is costing you prop efficiency and performance.  Don’t forget to lean in the climb.

Bob also says that 105 KIAS is the most efficient climb speed in reference to the Mooney wing.

I do almost all of the above except for the climb speed as I prefer cooler cylinders by setting a 500 FPM ROC on the AP until cruise.

^ This. I find 120MPH statute  105 kts cools cylinder heads well for my plane, gives good over the nose visibility. Consider an EDM 9xx if you don't have 4 cyl engine monitoring already.

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For safety's, the best rate climb (full throttle, 2700 RPM and Vy) procedure has nothing inherently wrong with it.  Instructors teach different things, my instructor said "pshaw, the IO-360 could run at full power for weeks without a problem as long as you have enough air, fuel and oil."

The indirect problems it causes, as noted above, is less visibility, less engine cooling, and lost time to destination.  Mooney's are pretty good for cooling, and a lot of times I can climb at best climb all the way to altitude without cooling problems.  Making small S-turns mitigates the visibility issue, and lost time isn't always an issue.

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  • 3 years later...

My G says 25/25 or 26/26. My engine overhaul shop says stick with the book. I’ve read a lot about this lately so I’m confused. Flown thousands of hours squared so I’m old.

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37 minutes ago, hoot777 said:

My G says 25/25 or 26/26. My engine overhaul shop says stick with the book. I’ve read a lot about this lately so I’m confused. Flown thousands of hours squared so I’m old.

We've learned a thing or two in the 50+ years since your manual was written. 25 squared (or any number squared) and 50º ROP have been disproven as proper techniques since before I started flying. That was only 30 years ago, though.

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My C climbs well with all three levers as close to the panel as I can push them. No trouble in 16-1/2 years' ownership. 

When I remember, I use Target EGT to lean in the climb.

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3 hours ago, hoot777 said:

My G says 25/25 or 26/26. My engine overhaul shop says stick with the book. I’ve read a lot about this lately so I’m confused. Flown thousands of hours squared so I’m old.

25 square is very old school and is no longer recommended.

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In my opinion lowering the nose if able and increasing airspeed that you climb at is far more effective in controlling cyl head and oil temps than reducing power, reducing power can have the effect of making you slow down to best rate of climb speed in order to maintain climb and push temps higher.

We don’t have this issue if we are fuel injected but many carbureted aircraft especially have an “economizer” feature that automatically leans the mixture when you reduce power which may not be what you want. I was corrected on that because I thought our fuel injection had the power enrichment at full throttle but it apparently doesn’t. Most engines do even auto and outboards go extra rich near full throttle.

Holley carburetors for autos for instance

https://documents.holley.com/techlibrary_power_valves.pdf

Aircraft specific below 

https://www.aopa.org/news-and-media/all-news/1998/april/flight-training-magazine/the-economizer

Reduced power takeoffs and climbs have cooked many an R-1340 for instance by Ag pilots trying to be kind to their motor.

The argument of reduced vs full power climb is the first memory I have of pilots discussing a technique at the FBO my Father kept his airplane at, roughly 1968 or so, maybe earlier.

Its been around forever. 

While the POH takes precedence I believe Lycomings take is full power, full rich until 5,000 ft then begin to lean if roughness is noted, but that’s from memory not sure I can find that in print

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On 2/7/2024 at 7:28 AM, hoot777 said:

My G says 25/25 or 26/26. My engine overhaul shop says stick with the book. I’ve read a lot about this lately so I’m confused. Flown thousands of hours squared so I’m old.

No risk in telling you to stick with the book. What could we have possibly learned in half a century? 

Everyone else has covered the simple answer. 

I would say that temps are the second most important consideration next to terrain clearance.  Does your G model run hot in the climb? In my experience, the O360 powered Mooneys run hotter than I would like at max power. Some have no choice but to reduce power to maintain comfortable CHTs. Some say that CHTs as high as 420 in climb are acceptable. If I were you, I would make a decision about what you think is acceptable and manage to those metrics, not some arbitrary "blah blah squared". Climb as rapidly as you can within the temp range that you find acceptable.

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I climb my C at WOT/2700. If necessary for engine temps, don't reduce power--lower the nose a bit and climb at slightly higher airspeed. Reducing power will also reduce air flow over the engine, and therefore reduce engine cooling. 

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