Red box

[MooneyBob]

Another stupid rookie question :

Can you clarify the term " Stay out of the Red Box" ? Where can I find more about that.

Thanks.

PS. Let me know if I am too annoying.

[MooneyBob]

Ok. That's what I found about the Red Box. The problem is that my POH says to lean 100F rich of peak at 75%.

Now what? Is that because the power decreases with the altitude? At 8000' your max output is less than 65% so you can lean whatever you want?

Red Box = No Fly Zone

At and below about 60% power, there is no red box. Put the mixture wherever you want it.

At about 65% power or so, 100ºF ROP to Peak.

At about 70%, 125ºF ROP to 25ºF LOP.

At about 75%, 180ºF ROP to 40ºF LOP.

At about 80%, 200ºF ROP to 60ºF LOP.

[Hector]

Looks like you have an M20J so I would first search for LOP (lean of peak) operations and you should find lots of threads with useful information. I have a C so can't really run LOP, but if I had a J that's what I would do. In my C I typically cruise at 65 percent power and I lean until she complaints then enrich a tad. I have an engine monitor too so I make sure my CHT's are below 380.

Sent from my iPad using Tapatalk HD

[Bob - S50]

Here are a couple links to pages that have numerous articles or webinars on lot of subjects:

 

http://www.avweb.com/news/pelican/182146-1.html?redirected=1

 

Just articles.

 

https://www.savvymx.com/index.php/webinar

 

A page of webinars plus, at the top of the page you'll find a tab labeled resources.  On that tab you'll find a link to Mike's articles.

 

You'll find info on both pages about Lean Of Peak (LOP) and the red box and even the red fin.  Basically, the red box is a combination of power and mixture settings that are likely to result in a CHT over 400 degrees and puts the most stress on your engine.  The idea is that if you keep out of the red box, your engine will last longer.

 

Bob

[carusoam]

Also look for APS...

http://www.advancedpilot.com

A couple of things to know or keep in mind... The engine manufacturers, plane builders, and pilots are not necessarily on the same page.

Some want to go fast, others want to go efficiently, and some like to pick how to operate by the amount of free cash in their pocket that day.

In some cases the marketing department wrote pseudo technical documents that indicate riding your horse hard and putting her away wet is an acceptable practice...

Hard and wet...

Some pilots can afford a new engine whenever the need arises. Trade the old plane out when getting the new one from the factory...

Hard...

The next level expect to afford new cylinders at 1000 hrs. Typical of a TC'd engine run at highest continuous output levels.

Gentle...

The place where most of us operate is make everything last at least to TBO, if possible, or even beyond. LOP where / when available. ROP with an extra margin for climb or if the engine can't manage LOP.

Two engines known for not handling LOP over a wide range, carbureted or TC'd with unbalanced intake tubes...

Either way APS has a lab facility with instrumented engines that demonstrate the things you want to know about.

David Brown of APS (Australia) appears here on MS frequently.

Best regards,

-a-

[carusoam]

Where's Ross???

Some guys around here have some pretty specialized knowledge of some subjects. Ross (as well as others) is really good on this one.

Search for 'engine timing. You will find some brilliant material regarding the IO360, 25 deg BTDC vs 20 deg BTDC, which one you have vs which one you would prefer vs. how much free cash will stay in your pocket at any one time!

Best regards,

-a-

[Bob - S50]

Where's Ross???

Some guys around here have some pretty specialized knowledge of some subjects. Ross (as well as others) is really good on this one.

Search for 'engine timing. You will find some brilliant material regarding the IO360, 25 deg BTDC vs 20 deg BTDC, which one you have vs which one you would prefer vs. how much free cash will stay in your pocket at any one time!

Best regards,

-a-

Of course, I'd be VERY careful about setting any timing other than that specified by the manufacturer.  I don't think any A&P would do anything different.

 

Or are you saying something else?

 

Bob

[carusoam]

There are two different specifications depending on the hardware you have...

I'm not recommending you go experimental!

But there is some interesting reading on this subject for the IO360 in Mooneys.

Best regards,

-a-

[John Pleisse]

This is a regime of high ICP and potential detonation that one must pass through at least  twice to achieve LOP OPS. Logical, isn't it. Completely absolved by a fancy dime store word called "metallurgy".

[ArtVandelay]

There seems to be a lot discussion on leaning technique, personally I will follow the engine manufacturers recommendations:

For lycoming I found 2 documents, search for service instruction 1094D or part number SSP700.

[aaronk25]

One note on timing....I've noticed that on the io360 200hp dualmag that is set at 25degrees it's better off running 2350rpm or higher and to not run really high mp settings "over squared" and I hate to use use that term.

25degrees is a lot of timing and the slower the engine turns the sooner the fuel mixture ignites.

Willmar timed mine wrong and set it at 20degrees and I could run 2100rpm and 25"mp all day long but bring timing up to 25 degrees and temps go up along with some torsional vibration. With that said at 25 degrees my J is about 5kts faster. We corrected the timing and set it back to 25degrees.

I heard 23 is great compromise.

The IO360 really isn't that smooth below 2350rpm anyway so 2400+ is where I cruise at. LOP of course

[Bob - S50]

We sometimes forget where the 'red box' came from.  Bottom line is it was defined as power settings and mixtures that resulted in CHT over 400 degrees, not an area that will cause immediate detonation.

 

The example we see on the internet is based on a specific engine, an IO540 if I remember right.  Your mileage may differ.  From what I've seen, the odds of detonation happening at power settings of 75% or less are just about zero so passing through the red box is not going to make the engine blow up when we lean for cruise.  Since CHT is the best indicator we have of internal pressures, as long as we keep the CHT in check without extraordinary measures, all should be well.  In the case of our Mooneys, I take that to mean not needing to keep the cowl flaps open at cruise to keep the engine cool.  We can do that by reducing power or running LOP or ROP.  Personally, I'd rather run LOP and burn all the fuel I dump in the engine rather than blow a lot of it out the exhaust pipe.  I hate the idea of leaving a trail of dollar bills behind the plane.

 

Bob

[KSMooniac]

 Since CHT is the best indicator we have of internal pressures, as long as we keep the CHT in check without extraordinary measures, all should be well. 

 

Not true.  CHT is influenced greatly by OAT in addition to the mixture setting and resulting internal cylinder pressures (ICP).  You can be operating at very high ICP on a cold day and have CHTs that are quite cool.  Not a good spot to run.  The only way we currently have to control ICP is via mixture settings as a proxy.

 

Taking the Advanced Pilot Seminar is the most efficient way to learn everything you need to know about operating our engines in a smart manner.  You can try to gather the info yourself, but really the best way to go is just to take the course and let the pros help you learn quickly, and completely.

[jetdriven]

Ok. That's what I found about the Red Box. The problem is that my POH says to lean 100F rich of peak at 75%.

Now what? Is that because the power decreases with the altitude? At 8000' your max output is less than 65% so you can lean whatever you want?

Red Box = No Fly Zone

At and below about 60% power, there is no red box. Put the mixture wherever you want it.

At about 65% power or so, 100ºF ROP to Peak.

At about 70%, 125ºF ROP to 25ºF LOP.

At about 75%, 180ºF ROP to 40ºF LOP.

At about 80%, 200ºF ROP to 60ºF LOP.

Perhaps on a Continental IO-550, but the Lycoming seems to more tolerant if the concept of a smaller "red box". Such as this:

65% power or less, no red box

75% power 80 ROP to 25 LOP

83% power 125 ROP to 40 LOP. LOP is 11.0 GPH while ROP is ~14.

Or 95% power sea level 16 GPH which is close to 100 ROP. Typical air race setting. CHT there is 360.

Of course limit CHT to 400f max prefer 380 continuous. Below 50F OAT subtract 20F from the limits.

Or for those of you that say follow the Lycoming guidance to the letter, peak EGT at 75% power or less.

[David Brown]

I see someone was wondering where I was, sorry folks I have been a busy boy with work, and flying a lot.

 

Let me see if I can provide some clarity to a few points, there are some well intended posts but the details are a bit off course.

 

1. The Red Box was an APS creation. It was a a way of depicting the kind of combustion events which by mixture control gave Internal Cylinder Pressures not above about 700 PSI. It should be noted this applies to ALL engines not just a particular brand. The edges of the red box are very fuzzy, and we think a little bit on the conservative side so do not fear if the appropriate LOP setting is say 25dF LOP and you have some at 30, some at 25 and one at 15-20 or there abouts. That cylinder is not about to fall apart on you. Some folk stress a little too much.

 

Notice nowhere here have I mentioned anything about CHT.....DOH! DOH!  I said it....and that is about all about that. It has nothing to do with it. Do not use CHT as a direct representation of ICP, which is what some folk think when they use a 380dF as a target or acceptable number. Some aircraft and especially in cold conditions will never get a CHT reading of 380dF, but their ICPs are up over 700 for sure. Granted the combination is worse, but I hope you get the point, if the ICP's are right the CHT will be lower than 380 anyway and it is even less stress.

 

CHT tracks ICP as the CHT is a result of ICP but as Scott pointed out a couple of posts up, this notion of using CHT as a surrogate for ICP measurement is fatally flawed. Scott has good advice there! 

 

2. I can't say that anyone from APS would agree that the revised table Byron has posted be adopted, just on the basis of the Lycoming heads seem to be better built than the TCM. Not all Lyc cylinders are as robust as others either.

 

3. There is no chance of detonation in any "conforming engine" be it N/A or Turbo if the pass through the zone from say 75dF ROP to peak EGT is done in a time frame of less than a minute, and most of use would be there no longer than 10-15 seconds even when doing it slowly. In a N/A engine it is a non event completely.

 

4. Bob, in your second post the POH says 100dF ROP, well that is a bit too far inside the box for my liking, it is not rich enough, but do the APS course and watch the data for yourself, make up your own mind with education and data. Remember many of these manuals were written for various purposes, and not all of them are aligned with the economy of your wallet in mind. This is a time to think marketing numbers, speed range economy Vs what the engineers really would like.

 

5. Staying out of the red box on the LOP side also has one other benefit, it puts you right where the engine is at its most efficient. Best BSFC for the power setting. Go to the APS website where there is a short video and a great interactive tool set up to play with and see where the edge of the redbox is compared to the BSFC curve and compare that to the Green Box numbers. There is an infinite number of red boxes ...or if you like one big variable one!

 

http://www.advancedpilot.com/redbox.html

 

 

 

Red Box = No Fly Zone

• • At and below about 60% power, there is no red box. Put the mixture wherever you want it. 
• • At about 65% power or so, 100ºF ROP to Peak. 
• • At about 70%, 125ºF ROP to 25ºF LOP. 
• • At about 75%, 180ºF ROP to 40ºF LOP. 
• • At about 80%, 200ºF ROP to 60ºF LOP. 

 

 

 

 

Outside the Box

• • At 65% power, use richer than 100 ROP, or leaner than peak EGT. 
• • At 70%, use richer than 125ºF ROP, or leaner than 25ºF LOP. 
• • At 75%, use richer than 180ºF ROP, or leaner than 40ºF LOP. 
• • At 80%, use richer than 200ºF ROP, or leaner than 60ºF LOP. 

Please remember that you can share this information, but only in its entirety and with attribution to Advanced Pilot Seminars.

 

Happy to atke questions at any time, if you feel my presence is lacking, send me an email by using the link on the bottom of this page http://www.advancedpilot.com/livecourse-au.html

 

Hope that helps and sorry for taking so long to see the thread.

[aaronk25]

I see someone was wondering where I was, sorry folks I have been a busy boy with work, and flying a lot.

 

Let me see if I can provide some clarity to a few points, there are some well intended posts but the details are a bit off course.

 

1. The Red Box was an APS creation. It was a a way of depicting the kind of combustion events which by mixture control gave Internal Cylinder Pressures not above about 700 PSI. It should be noted this applies to ALL engines not just a particular brand. The edges of the red box are very fuzzy, and we think a little bit on the conservative side so do not fear if the appropriate LOP setting is say 25dF LOP and you have some at 30, some at 25 and one at 15-20 or there abouts. That cylinder is not about to fall apart on you. Some folk stress a little too much.

 

Notice nowhere here have I mentioned anything about CHT.....DOH! DOH!  I said it....and that is about all about that. It has nothing to do with it. Do not use CHT as a direct representation of ICP, which is what some folk think when they use a 380dF as a target or acceptable number. Some aircraft and especially in cold conditions will never get a CHT reading of 380dF, but their ICPs are up over 700 for sure. Granted the combination is worse, but I hope you get the point, if the ICP's are right the CHT will be lower than 380 anyway and it is even less stress.

 

CHT tracks ICP as the CHT is a result of ICP but as Scott pointed out a couple of posts up, this notion of using CHT as a surrogate for ICP measurement is fatally flawed. Scott has good advice there! 

 

2. I can't say that anyone from APS would agree that the revised table Byron has posted be adopted, just on the basis of the Lycoming heads seem to be better built than the TCM. Not all Lyc cylinders are as robust as others either.

 

3. There is no chance of detonation in any "conforming engine" be it N/A or Turbo if the pass through the zone from say 75dF ROP to peak EGT is done in a time frame of less than a minute, and most of use would be there no longer than 10-15 seconds even when doing it slowly. In a N/A engine it is a non event completely.

 

4. Bob, in your second post the POH says 100dF ROP, well that is a bit too far inside the box for my liking, it is not rich enough, but do the APS course and watch the data for yourself, make up your own mind with education and data. Remember many of these manuals were written for various purposes, and not all of them are aligned with the economy of your wallet in mind. This is a time to think marketing numbers, speed range economy Vs what the engineers really would like.

 

5. Staying out of the red box on the LOP side also has one other benefit, it puts you right where the engine is at its most efficient. Best BSFC for the power setting. Go to the APS website where there is a short video and a great interactive tool set up to play with and see where the edge of the redbox is compared to the BSFC curve and compare that to the Green Box numbers. There is an infinite number of red boxes ...or if you like one big variable one!

 

http://www.advancedpilot.com/redbox.html

 

 

 

Red Box = No Fly Zone

• • At and below about 60% power, there is no red box. Put the mixture wherever you want it. 
• • At about 65% power or so, 100ºF ROP to Peak. 
• • At about 70%, 125ºF ROP to 25ºF LOP. 
• • At about 75%, 180ºF ROP to 40ºF LOP. 
• • At about 80%, 200ºF ROP to 60ºF LOP. 

 

 

 

 

Outside the Box

• • At 65% power, use richer than 100 ROP, or leaner than peak EGT. 
• • At 70%, use richer than 125ºF ROP, or leaner than 25ºF LOP. 
• • At 75%, use richer than 180ºF ROP, or leaner than 40ºF LOP. 
• • At 80%, use richer than 200ºF ROP, or leaner than 60ºF LOP. 

Please remember that you can share this information, but only in its entirety and with attribution to Advanced Pilot Seminars.

 

Happy to atke questions at any time, if you feel my presence is lacking, send me an email by using the link on the bottom of this page http://www.advancedpilot.com/livecourse-au.html

 

Hope that helps and sorry for taking so long to see the thread.

 

I want to ask you what you think of the following:

 

I am convinced it is almost impossible to damage a cylinder do to Internal Cylinder Pressures, given the cylinder assembly is at a low enough temperature where the metal isn't substantially weakened from heat.  Example: if I put a metal rod in a vice that was 5' long and hung from one end, it could strictly support my weight indefinitely however take the same example and have someone take a torch and heat it about 1' from the vise while supporting my weight and rather very quickly the bar will begin to bend.

 

We know the only way to get high ICP is to create a bunch of heat and I get that if its cold outside or the airplane has a efficient cowl design the heat can be transferred to the air resulting in lower CHTs, but my point is whether its 700psi or 1100psi, if the chts are 330-360 I believe the cylinders assembly can withstand just about any pressures you throw at it, given the temps stay low.  Even in auto-ignition events the cylinder doesn't tear itself apart until it gets hot 450+ degrees wear it then becomes weak enough from heat that the forces can rip the cylinder apart.

 

That said I also believe that even at lighter power settings running at 420 is destructive.  Isn't it more about the strength of the metal not the ICPs the metal has to deal with?  And strength directly correlates to temperature, especially with aluminum, right?

[jetdriven]

Aaron the piston is the weakest link in detonation and preignition events.

[aaronk25]

Aaron the piston is the weakest link in detonation and preignition events.

 

Byron,

 

Your right, it is.  I should have left the detonation and preigntion alone and talked directly about high power settings and how low temps but high chts aren't was cause damage but rather heat fatigued metal, under high ICP loads if were talking about what causes head to barrel separation and cylinder head cracks.  

[KSMooniac]

High ICP in continuous operation like you practice and preach will shorten the fatigue life of the cylinder assembly.  Heat and pressure (loading) are enemies to aluminum,  Increase either or both and you shorten the life of the part.  Period.  That is just the way it works with metal.  You might get a TBO run out of your cylinders with your High ICP and moderate temps, you might not.  Our cylinders are $2k each, so I'd rather get more life out of mine instead of flogging them...it does make economic sense to overhaul them vs. just chucking and replacing with new like many other cylinders.

 

I'm planning to pick up my newly overhauled and optimized cylinders next week and can't wait to get my engine back together, and hopefully enjoy another 2000+ hours on these cylinders while saving thousands of dollars at overhaul.  YMMV

[carusoam]

David,

Thanks for the follow through.

Best regards,

-a-

[jetdriven]

This is a regime of high ICP and potential detonation that one must pass through at least  twice to achieve LOP OPS. Logical, isn't it. Completely absolved by a fancy dime store word called "metallurgy".

To be fair here if you operate per the POH you go through it twice as well. You lean to peak and then slightly past (how else do you find peak?) then enriched back past peak and then set 50 ROP. Which according to some folks is right in the middle of the red box.

[ArtVandelay]

To be fair here if you operate per the POH you go through it twice as well. You lean to peak and then slightly past (how else do you find peak?) then enriched back past peak and then set 50 ROP. Which according to some folks is right in the middle of the red box.

Not if you reduce power 1st, then you can LOP/ROP all you want.

[carusoam]

The concern is extended periods of ICP...

The confusion is using an external surface thermocouple to define it.

All the logic in the world will not allow for using an external thermocouple to measure internal pressure meaningfully. Especially if the thermocouple is effected by outside instigators such as OAT, cowl flaps and airspeed. That thermocouple has difficulty defining what the actual cylinder temperature is.

APS has done pretty well to measure ICP (which we cannot) and correlate it to Peek EGT and %BHP (wich we can) and define a cautionary area to wich we can avoid for extended periods of time.

I'm good with that. There are engines that follow this guidance and meet or exceed TBO. What more can we ask for?

If I had a TN IO550, I would be looking for a way to extend cylinder life in a reliable manner. But I think they would say to reduce power.

Tough choices...

Best regards,

-a-

[KSMooniac]

There are stories of folks running the TN IO-550 to 3000 hours or more, with routine cruise at 85% and 90-100 LOP.  The ICPs at that setting are less than at 75% and 50 ROP, and the CHT's are dramatically lower.  What's not to love?

[Cruiser]

Everybody............

 

 

some of the beliefs about LOP are just as bad as those about ROP. 

 

#1 Internal cylinder pressure (ICP). Your engine is designed and engineered to run safely according to the operator/pilot handbook. Unless you exceed the limitation of the manufacturer damage is not likely to occur. That being said, there are ways to operate your engine that are better than others. Aaron is correct. ICPs cannot reach destructive values in a conforming engine at engine manufacturers recommended operating settings. PERIOD.

#2. Damage/hurt/fatigue/failure/destroy, shorten the life or make TBO are all used to describe operating INSIDE the RED BOX. Does anybody really believe they will damage their engine by leaning the mixture through the RED BOX for mere seconds or any about of time? Be serious, 

 

No one including Mr. Brown has described what "damage" occurs to the engine when you enter the realm of the "RED BOX"  

Has anyone had to overhaul their engine early because of "high ICP" ??????????? Anyone?

 

I have heard of top overhauls due to burned valves but that is not because of high ICP

I have heard of cylinder replacement due to stuck/broken rings but that is not because of high ICP

I have heard of major overhauls because of low compression or excessive oil usage. (ICP could be a major issue here)

All of these may be because of high CHT which is a byproduct of high ICP and most certainly are achieved by operation in the RED BOX.

 

All of these are results of many hours of operation in demanding engine configurations that can lead to the above type of failures. 

LOP is a better way to run your engine and can extend the life and limit the wear within the engine. You are NOT going to destroy it by slowly moving through the RED BOX or loitering there for short periods of time.

The primary benefit of LOP operations is EFFICIENCY in terms of BSFC. Pure and simple. All things being equal, your engine will like it, the environment will like it and you should have fewer problems.