Reducing to 25/2500

[Shadrach]

On May 7, 2016 at 5:26 AM, teejayevans said:

More power requires more fuel burn which gives off more heat, and if climbing with reduced cooling, you're going to get hotter temperatures.

In 1960s they didn't have engine monitors, if you can keep your CHTs below 400 (I use 390 as warning level), go for it

My engine talks to me, at 2700 it sounds like it is working hard,at 2600 its a lot quieter.

The above somewhat oversimplifies what is happening. The difference in actual fuel burned (not fuel flow) is pretty small.  How much heat is conducted to the cylinders is affect as much by how power is made as it is by how much power is being made.  One can make 80% power and depending on the setting have cooler or hotter CHTs.  Think about these two hypothetical power settings:

28", 2700  and 80ROP

WOT, 2700 and full rich.  

Number two is burning more fuel, making more power and yet generating lower CHTs.

The only thing your engine is "telling you" when you reduce from 2700 to 2600 is that a 100RPM reduction sure makes a difference in prop noise.  

Reducing RPM at a given throttle setting typically increases internal cylinder pressure.

 

[M20F]

A lot of the heat issues on climb I find from an overly aggressive pitch more than anything else.  Flying 120mph or better in the climb and slowly moving towards Vy when you start losing manifold helps a lot.  

If I am going to 8-9K I leave it at 2700 because the power fades unless I put the turbo in.  If I am doing a local run I generally dial back to 2600 and then to 23/23 quickly because it's a lot quieter and cheaper. 

[mooniac15u]

On May 5, 2016 at 0:27 PM, N33GG said:

Let's see... imagine as a CFI I am requested to give a complex endorsement.  Therefore, by simple logic, the pilot has not yet even received a complex endorsement, and is likely low on the complex experience curve.  However, upon showing up for the complex endorsement flight, the pilot is going to show me he has a deeper understanding of engine management than just memorizing the POH, from reading forums on the web.  I'm not sure this would favorably impress me.  In fact, it might make me nervous and wanting to find out if there is anything flat wrong or dangerous in his head, that this pilot has picked up during his browsing, before I sign him off with my name in his log book.  It would likely extend the ride, at the very least.

I stand by my original statement.  Stick to the POH until you get the endorsement.  

again, just my two cents

The OP said he is doing 5 hours of transition training with a CFI, some of which will result in a complex endorsement. So, rather than asking operational questions your advice is to blindly quote the POH until you can get the signature and then decide how to operate based upon the collective wisdom of the Internet? Is that what you would want your students doing?

[DXB]

On 5/7/2016 at 5:36 PM, Skmoore63 said:

DXB, you reminded me of one other issue I have been chasing too, the baffling. When I replaced spark plugs last summer, I did a lot of baffle work but did notice my bird was missing the front baffling that goes around the starter in the nose bowl. Mine has the Lasar cowl mod, don't know how much this impacts the cooling, but will fix it in the annual in a couple of weeks. I do definitely like the climb performance better at WOT/2,700. Will report back, pray for my checking account.

I have the same cowl closure  - doesn't do much to improve cooling or speed, just looks.  It does make it miserable to seal up around the alternator and starter by blocking access - mine was missing the seals around both.   I managed to get the alternator taken care of with some cut strips of baffle material, RTV, and contortionist skills.  I also closed the gap around the outer exposed half of the starter, but the big gap toward the crankcase seems utterly inaccessible with the cowl closure in place, so you must drop the bottom cowl.  Too big a job for me- I'm still trying to get my shop to address.  

BTW, I recall someone once posted here regarding high CHTs after installing Powerflow exhaust. They described calling Marvel Schebler about it, and the company immediately knew what the carb issue was that is specific to this exhaust- sorry I can't recall the details, but it might be worth the phone call. 

 

 

[steingar]

2 hours ago, mooniac15u said:

The OP said he is doing 5 hours of transition training with a CFI, some of which will result in a complex endorsement. So, rather than asking operational questions your advice is to blindly quote the POH until you can get the signature and then decide how to operate based upon the collective wisdom of the Internet? Is that what you would want your students doing?

The problem for the student is verification.  The POH is a verified source, no one will question adherence to its dictums.  Which of our participants is speaking out of expertise and which are blowing smoke is not easily verifiable.  

Indeed, the only person on the internet to who's musings on the subject I ever paid the slightest bit of attention is an engineer who worked for Lycoming. And I still take his musings with a healthy grain of salt.

The only person I can really speak for is myself, and you can bet I'm blowing smoke.

[Raptor05121]

On 5/8/2016 at 10:13 PM, ryoder said:

I used to do that but based on this site and the mapa doc here http://www.mooneypilots.com/mapalog/M20C%20Evaluation/M20C_Evaluation_Report.html plus my flight instructors advice I no longer do.  I have a 1000 foot checklist which includes shutting off fuel pump, dialing back the prop to 2600 and pitching for 120mph for better cooling.  I fly like this until I get to my altitude but monitor CHT closely and pitch down if it gets too warm.  I also start leaning once I hit 2000 feet even while still climbing.

 

I touch nothing on the engine until 1000 feet and call out "though one thousand" when I get there.

Thanks for the link. If I may quote:

" Notice that the climb was performed at full throttle, max rated RPM and the mixture leaned to 100-125 degrees rich of peak. If you want to climb your C model the most efficiently, that's the power you'll consider using. The idea of reduced power climbs (the old '25 squared' myth) is old school thinking. There is no technical data anywhere from any of the engine manufacturers that shows reducing power after takeoff makes the engine last longer or makes it run cooler or helps it make TBO easier. The engines we fly in Mooney airplanes are all rated for operations at maximum continuous power. Note the word 'continuous'. A power reduction after takeoff (especially with a normally aspirated engine) only serves to 1) reduce climb performance when you need it the most, 2) slows the airplanes progress across the ground during climb, 3) can actually make the engine run hotter - at max power you can climb at an airspeed well above Vy. So, with a normally aspirated engine, keep the power up during climb, keep the mixture leaned to 100-125 degrees rich of peak EGT and keep the speed up higher than Vy. If you do, you'll be getting your Mooney to altitude in the most efficient manner and operating the engine at peak efficiency. "

[Shadrach]

35 minutes ago, Raptor05121 said:

Thanks for the link. If I may quote:

" Notice that the climb was performed at full throttle, max rated RPM and the mixture leaned to 100-125 degrees rich of peak. If you want to climb your C model the most efficiently, that's the power you'll consider using. The idea of reduced power climbs (the old '25 squared' myth) is old school thinking. There is no technical data anywhere from any of the engine manufacturers that shows reducing power after takeoff makes the engine last longer or makes it run cooler or helps it make TBO easier. The engines we fly in Mooney airplanes are all rated for operations at maximum continuous power. Note the word 'continuous'. A power reduction after takeoff (especially with a normally aspirated engine) only serves to 1) reduce climb performance when you need it the most, 2) slows the airplanes progress across the ground during climb, 3) can actually make the engine run hotter - at max power you can climb at an airspeed well above Vy. So, with a normally aspirated engine, keep the power up during climb, keep the mixture leaned to 100-125 degrees rich of peak EGT and keep the speed up higher than Vy. If you do, you'll be getting your Mooney to altitude in the most efficient manner and operating the engine at peak efficiency. "

I think that's reasonable advice. I would amend that setting to an initial take off EGT of 200°ROP (preferably 250°) or richer on all cylinders; your engine may already be running there at full rich.  

[mooniac15u]

1 hour ago, steingar said:

The problem for the student is verification.  The POH is a verified source, no one will question adherence to its dictums.  Which of our participants is speaking out of expertise and which are blowing smoke is not easily verifiable.  

Indeed, the only person on the internet to who's musings on the subject I ever paid the slightest bit of attention is an engineer who worked for Lycoming. And I still take his musings with a healthy grain of salt.

The only person I can really speak for is myself, and you can bet I'm blowing smoke.

Exactly why I suggested bringing this up during transition training. I never suggested deviating from the POH, just that it would be a good opportunity for a discussion. The CFIs and DPEs that I've flown with have always seemed to appreciate questions that go beyond the rote memorization. 

I was thinking something along the lines of "The POH says X, which is how I plan to operate, but I've heard some other pilots say they do Y. Do you have any thoughts about that?"

[Shadrach]

^^^^This.

TImes have changed and we have a lot of solid data to that improves upon if not contradicts what our old POH/AFM/Owner's manuals say.  My 67F came with an owner's manual from the factory.  I can say without question that it's a kind of cobbled together mess. Many of the performance tables are close to real world if not a bit optimistic, but I can plainly see where they attempted to extrapolate performance data and did so poorly (very poorly), especially in the fuel burn data.  All of the climb tables state that they were performed at Full Throttle, Full Rich, Ram Air Open and Max RPM. Yet under operations there's a blurb about reducing to 26'X 2600 at 1000'.  If you're like my Dad is, you'd read that and think if 26"X 2600 is kind to the engine, than 25"X 2500 must be even kinder!  Talk to your CFI, if he's not a complete dinosaur, he'll be willing to talk about it.

[steingar]

32 minutes ago, mooniac15u said:

Exactly why I suggested bringing this up during transition training. I never suggested deviating from the POH, just that it would be a good opportunity for a discussion. The CFIs and DPEs that I've flown with have always seemed to appreciate questions that go beyond the rote memorization. 

I was thinking something along the lines of "The POH says X, which is how I plan to operate, but I've heard some other pilots say they do Y. Do you have any thoughts about that?"

While it can be discussed between student and instructor (or even examiner) do keep in mind that CFIs and DPEs are only rarely engineers.  Hence their opinion on the subject is suspect.  They got it from somewhere, but where?  Was it a trustworthy source?

Most of the advice in this thread (mine included) is what people were taught or what they do.  While the latter is actually quite valuable, it is also entirely anecdotal.  What works in one aircraft may very well not work in another.  Moreover, I'll bet no one really has a clue how their practices fall out in cylinder or engine failures.  My guess is people do what they do and get the results they get.  While not an inherently bad approach, it does have limits.

I assume that when they wrote the POH an engineer was involved somehow, so there is some real world basis for the procedures dictated.  Then again, for all I know it wound up there because someone had some "wisdom" based on something they'd heard.  But you have to start somewhere.

To be honest, I suspect Lycoming substantially overbuilt the 0360.  I wouldn't be surprised if there's really not that much you can do to bollux it in normal operations, and that ascending WOT and 25 squared give you roughly the same results vis a vis engine longevity.  But I have to now admit to fully blowing smoke.  I am no engineer nor do I design or built airplane engines or airplane anything else.