David Brown

Darin, I am not sure how well you know or work with the guys at GAMI, but lets get something straight, the numbers are fuzzy numbers, and you are wanting to split hairs. But lets shall we. No they do not. The rest others have already explained.

Brian, TCM do not publish a minimum, but Lycoming do at 175dF. Interesting the TCM water cooled cylinders had the thermostat set to 225, and the cylinder underneath is the same as all the 520/550 otherwise. So it is safe to assume that even if the POH says nothing, this is OK. Max temps is another matter. And this gets some folks in a spin. By the way, having complete and blind faith in POH's is a fatally flawed position. I assume that was not what you were trying to say, so just for clarification for anyone reading consider this. When one critically examines many POH's and engine manuals, you find data that is contradictory to each other, to themselves one page to the next, or at complete odds with the laws of physics. We know of one OEM employee who when he saw his work being displayed in the APS class as something needy of critical thinking, he even put his hand up and declared he was embarrassed to admit he wrote it and it was wrong and should not be in circulation. So using critical thinking is prudent. Faith without careful consideration is sub optimal. Hope that helps.

Darin, CHT will reflect ICP, as ICP is the driver of CHT. As you change the ambient the raw value of CHT will change, but the general relationship remains, until such a point as it is so cold that considerable ICP change seems to be immeasurable. Just a small correction if I may, best power mixtures are around 75-80dF ROP, where as the peak ICP is found at 35-40dF ROP. Not much in it, granted, but you are someone who likes to be accurate, so I hope this helps. You are 100% correct in that the ICP in the cockpit is not readily available, but the data contained in the APS Red Box graphic or the Mike Busch Red Fin is all the pilot needs. Anything more is like the effect of a fairy tap dancing on a pin head. Cheers!

Aaron, I would bet that at 330dF CHT you are not near or over 700PSI. Tell me your typical cruise method and I can do a guesstimate. But you are almost correct in that CHT plays an important factor, but CHT has nothing to do with the loadings on piston, rods, crank, bearings, gudgeons etc. So the focus on CHT at the expense of all others is like looking for only Zebras when you hear a stampede of hoofs. In the mid-west this could be flawed, they will be horses! I hope you get what I mean. As a rough idea, the strength of the alloy in the head at 380dF is about 78% of the strength at room temperature. At 320dF it is about 90% of the strength. So it is true the same pressure at lower temps is far better, but you rarely get that in practise. The ICP drives the CHT. By the way Mike would be blushing for sure with your accolades. But it is fair to say he is on the money most of the time except this idea of the 380dF CHT target. He is correct in terms of his engine o his plane. It just cant get bad enough. By the way, there is one famous A&P who learned a massive amount by doing the APS course three (3) times. No names . He is the only one in history to have done this. He is a clever fellow indeed and does much good work. Join the dots. By the way I admire his work too. But I can't for all the logic and science agree with the target CHT.

You are in a happy place! If you get down to below 175, then think about it as a problem.

Ross, I have no idea about your background, but it affects the science none, nor does mine. You are correct in saying that there are differences in CR and RPM and ultimately the typical working pressures, but they vary the science of fuel combustion not one bit. Peak power is still achieved at around 75dF ROP no matter which engine. The fuel does not know which cylinder it is inside. The curves and data we use apply to all. The red box theory is one which has very fuzzy edges, we actually teach this in the class. If you are operating one of the engines that has bigger margins, sure, poke away inside it, but use the concept to make an educated decision about it. If however it is a Chieftain engine, stick outside. I think we both agree here, but I do wonder if you actually know what is taught in class, as the comments above indicate otherwise. As for having data presented for every engine in the fleet you have got to be kidding me. But we do teach with a focus on the science as it applies to all engines, where questions are asked specifically about a type it is rather funny how the answer still applies to the rest, except when say it relates to fuel delivery systems, which are different. Funny enough they are quite happy with the Turbo Lycoming, and the TN cross flow Cirrus engine on the stand at the moment. Even stranger the folk who have Carby O360 & 320 engines are just as happy. We even talk about fixed pitch props and carby engines at times. I am not here to be prickly, nor upset you or anyone else, but perhaps my direct and less warm & fuzzy delivery is what is bothering you. Sorry if that is the case. John Deakin would perhaps be more softly written, and he does spend an hour carefully crafting what I type in 5 minutes. He has the luxury of time. Again I apologise for that. Walter however, you would either need your flame suit on or more likely he would ignore you. Walter is far more direct and far less warm and fuzzy. But a brilliant educator. We are all different, as are the folk here on MS. Some will be bothered by a direct response other not. So unless I have missed the point again......what we teach in the APS class is deliberately not engine specific because it matters not. We do show data from various engines, and the course is not Bonanza/TCM oriented, despite what you think. But no amount of me explaining that will likely change your perception. Sorry about that too. All the best.

OK folks, this could turn into one of those posts that goes on forever, so brace yourself for a rambling response. I will try to do it justice. First of all much of the material posted above is very good but there is more to clarify. What I see here is people wanting to micro-manage the situation, and not be big picture managers. Question from Aaronk, it is true that the cooler the cylinder the more pressure you can give it, however the more ICP you give it the temperature will rise, these two things go hand in hand. If you get ICP high enough often enough you could do damage, but it is a function of time/cycles, and in normal operation you would not do that. In a N/A engine this is hard to achieve. In a Turbo engine it is much easier. But you have to do some things that would be akin to stabbing your mother to death with a parker pen, cruel and would take a while. I can't see most folk doing that. But let me tell you a story where I think that has been happening. One of the countries best engine shops down here has had a TIO540 from a new 206, it has a couple of trashed cylinders from a 400 hour aircraft, I suspect the owners have been flying it by the old method of 50dF ROP, which might have been fine at 23/2300 but this thing cranks serious MP. Of course with a glass cockpit they can set 50dF ROP with considerable accuracy. Well the engine is showing a couple of cylinders in distress and failure of one with a valve broken, due to severe guide wear and the valve ratting into its seat has fatigued the stem. So is it possible, yes, will it happen overnight, no. But lets think about every engine. Out of six cylinders one will have the worst valve guides, one will have the worst oil flow, one will have the worst rings, one will have broken in the worst, one will have the worst tappet clearance......on you go through every facet. Now what happens when the cylinder that also happens to be the hottest is also coincidental with one or a few of the above mentioned. even if they are all in tolerance? This is now the cylinder that is most likely to live a shorter life. Give it more pressure and more heat and it will expose a weakness far sooner than if you do not. Even the large number of poorly built TCM cylinders that are out there never fail. Why? because one does and the others get ripped off at the same time. But one has to show signs of trouble first. Some IO520/550's go anywhere from 400-1200 hours and out of six there will be maybe three removed, and the others go to TBO, but if there is one thing that will help propagate the damage over time, it is higher CHTs coinciding with ICP. You can heat it to 500dF and 15PSI and it will live forever, but give it lots of cyclcles at a 50dF ROP setting at 32"/2400 and it will likely expose its defects just like the Turbo 206 did. Remember four out of six cylinders were still in one piece, and may have stayed that way for another 2000 hours, or maybe only 200, we will never know. So in closing your question, in theory can a cylinder survive 1100PSI at 330dF, sure it can and it does, when we detonate an engine on the dyno it starts there, and it survives, but the CHT's rapidly rise even with an impressive forced airflow. So you can't have one extreme with another like that. And in an airplane it is not possible to do that. Temperature - Pressure - time/cycles. TomK, can I clarify a few things, not all POH/engine manuals are well written and are often contradictory to themselves and the science. So do not place good faith in them, you need to critically think them through. We actually spend a bit of time Sunday afternoon on this very topic with several examples to teach folk how to spot them. It is farcical to say the least. #2 You are 100% correct when you say that spending a short period inside the red box will hurt nothing. This is 100% true. Again some people miro manage the science here thinking that during the time it takes to even do a GAMI lean test will hurt things, no it will not. But refer the Turbo 206 example above, we believe spending a long time in a bad place does eventually shorten life. I think I have explained the accumulation effect on the worst combination of tolerances above so hopefully that fits in with the rest of your post. As for spending some time in the red box......heck some times it is fun, or necessary. Let me tell a little story. Last year I had Walter Atkinson and his wife Sonya out here and we were touring around the outback with another friend in a G36. Walter and David were in the G36, Sonya was flying my plane and my wife was asleep in the back. We depart BNE IFR and once out in class G in VMC we were a few miles behind the G36, and we have identical TAS. ATC could not see us any longer outside radar and ADSB, so I said to Sonya, let's sneek up and formate on them. So how do I do that? I wound her up to 2700, we had 24.6" anyway, and this was about 85% power for the day. We were fuel limited, so I could not throw a APS ROP setting at it, so I did what Walter would do....cheat! So we had around 125-150 ROP across all cylinders, this was obviously way better than 75-100, but it did use more fuel. CHT's went up but not above 370ish and it was winter and cool. Was I catching them....yeah, 11% more speed and 60% more fuel burn. We caught them after 20-25 minutes, which was also not far from the point where the extra burn was going to hurt reserves, so it worked. Did we surprise them...NO. I forgot to turn my transponder off and they were watching us all the time on TCAS! DOH! DOH! Were we stressing the engine a lot more than before? Yes Sir! Did it fail? No. And it has not done so since. I am confident that it will make beyond TBO, this is a very healthy engine. So the point here is it is a function of all things. Potential for accelerating the weakest point of failure by continued and prolonged use of high ICP and temperature. We APS believe that if you can minimise these things and still get the same performance desired, you can operate in two ways. One is more likely to yield longer service life. There is no instant trashing of an engine, unless you preignite it for a few minutes. This graphic is derived from real data. Same HP on each curve. Pick your poison! Hope this helps, and if you keep all things in perspective it helps too. Quick shameless advert for any Australian viewers, hopefully nobody takes offence.

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.

Some of us would suggest that full rich is better indeed. Run around at say WOT 2500 and full rich, or if you can fly a bit lower do it at say 2500' and WOT/2500 and 40-50dF LOP. Much better way to break in the engine.

Great tip.......but Byron, why make it so complicated ?

Just a couple of points here regarding the above posts. Small bore or big bore......the fuel knows no different. The theorhy is the same whether it is a 360TCM or and IO550, a Lyc 540 or a P&W radial. so no need to worry about that. At 75% power ROP you should be aiming for something like 180dF ROP to stay out of the red box, at the fuel flow you talk about the 100dF ROP is not enough. Alternatively about 40dF LOP would do, As for adding back MP, when you do this the F/A ratio is already set, and the extra MP increases the mass airflow and the fuel flow at the same time to maintain the same approximate F/A ratio. The mixture is not getting richer except if there is a bit of non linear behaviour which is only small any way. Do not stress about that. How you are operating, fearing that you are avoiding something you are not sure of, by doing exactly the opposite of what the science and data shows is less stressful, is somewhat confusing to me. Makes me cringe actually. Perhaps another visit to the course. Email John Deakin and ask can you do it again and how much. He will cut you a pretty good discount for sure.

Erik, PRIST is a good idea indeed. We have more problem with vapour lock at the moment. Putting down in the outback might not be much more survivable and maybe a quick frozen death is better??? 102dF might have happened in one or two spots and I think 110dF was a bit more common, and plenty of places over 100dF. I do not have to shovel sunshine off my driveway though. You guys be careful over there!

The freezing point for Avgas is -50dC or -58dF, and now I understand why Perhaps it would have been warmer down here this last week! Aluminium Foil Tape is the answer to coolers, and it tends not to leave the cooler all sticky and gooey to collect dirt and grass etc later in Summer. Sorry you guys call it Aluminum Foil.

Byron, 19.X is acceptable and remember that the RSA system is a very goo MASS AIRFLOW device, so when you depart with a DA of say 1500' it has already accounted for that. If it was a DA of '0' it would flow more. You can change jets on the Carbs and you can change the flow of the fuel servo, however you need the gear to do it and this is best done by a shop with the shims the data and a flow bench set up to do it. Recently I have seen some AVSTAR fuel servo's on new engines (not the Precision Airmotive) and they have not been flowing the correct flows. Go figure! As Brian has calculated above a good BSFC is around 0.58-0.59 and at a DA of sea level on an ISA day, that gets you the fuel flows mentioned in this thread, the mid 19's and 17's for the 180HP. Brian, I am perplexed as to why you say all you will get is 90%. I regularly get 98-102% and it is all based on DA of course. Today it is 41dC where I am so I would not expect anywhere near that

Gentlemen, lets get something straight right from the start. At SEA LEVEL on a standard ISA day, the 200HP Lycoming should be drawing around 20GPH and no less than 19.5 USG/hr. The concept of CHT exceeding 400 degrees without an alarm and letting it go beyond 410 for any period is not harmonious with good engine break in. If any mechanic, hangar buddy or anyone else says otherwise I have a big cheque for them if they can provide data that proves otherwise. Your new engine deserves way better than this. TCM often have flow issues but a Lycoming is most often correct. I would be checking for induction leaks already, and insisting the mechanic sorts out your fuel flow. If he refuses, find a mechanic who will. As for not understanding this and engine monitors telling you things, I would urge you to attend the APS class in Ada OK in March. You will learn a heap and save yourself a fortune longer term. Actually likely the short term. If you want to discuss further please let me know. But please put an end to the engine abuse.