Leaning Basics

The topic tonight is pitch and let me start with the topic of fear because I have realized over four and a half decades of being a pilot and flight instructor that many pilots are afraid of pitching and are afraid of red. and I thought it would be instructive to maybe start by talking a little bit about why that is and then hopefully by the time we're done everyone will feel very comfortable with the red knob. I have some theories as to why so many pilots are afraid of lean and I think a lot of that has to do with how they were trained as elementary school students because I think a lot of the fear that pilots have of the red knob comes from their instructors. flight, we'll talk a little bit about why that is. but there are many problems with flight training;

There are also a lot of old wives' tales about things like detonation, pre-ignition and blow-off valves that suggest you know if you lean too aggressively you're going to blow up your engine, one of the most popular sayings I hear and I think comes out of the mouth From many flight instructors is that fuel is cheaper than engines, so don't do it, if you want to keep your engine happy, give it enough fuel. Some of that stuff turns out to be very bad advice and operating engines without tilting them properly turns out to be doing the engine no favors and the best way I can think of to illustrate this is to talk a little about a few things. that happened in flight schools because I think a lot of these problems that we have with the pilot lean procedure come from their primary training when a pilot, when a student pilot first learns to fly, flight instructors tend not to talk about tilt because The poor student is so busy trying to master the basic rudder and stick skills and you know, keep the dirty side down and don't damage anything that you don't want to distract the student with more than is necessary for him to notice. account.

We'll deal with the red knob later and then after a while what's called the law of primacy comes into effect, which basically says that the way you're taught to do something first is the way you remember it to the rest. of your life and once you learn something wrong, it is very difficult to unlearn it, so if as an elementary school student you are taught, you know, leave the red knob alone, it is very possible that you have that notion of leadership to leave the red knob alone . knob alone throughout your entire racing career unless someone corrects it and it's hard to unlearn something like that once you learn it.

Some very interesting lessons were learned at the world's largest flight school at Embry-Riddle Aeronautical University in Daytona Beach, Florida. I guess it must have been about fifteen years ago, in the 1998-99 contest winner, M Riddle operates the largest fleet of primary trainers in the world and at that time, about fifteen years ago, they were in the process of replacing their aging fleet , which was primarily Cessna. 150 and 152 and so on with a new fleet, at least what at the time was a new fleet of airplanes coming out of the newly restarted Cessna factory in Independence Kansas, Cessna 172 RN airplanes powered by Lycoming o-360 l2a engines.

Large simple trainer planes, fixed propellers, they were simply equipped with the standard instrumentation that Cessna was putting on those planes back then, there were no fancy engine monitors or anything like that and, as had been the tradition at Embry-Riddle for For a long time, flight instructors were generally I taught not to distract elementary students with mixture handling and to teach them that they should basically leave the red knob alone unless they are at an altitude above 5,000 feet and when you are training Florida, where everything is at sea level, doesn't spend much time above 5,000 feet, so basically the students didn't lean at all and that's how they were when they started training on this fleet of beautiful new airplanes that they had just acquired. none of these Cessna 172 RN aircraft.

They started having problems and the problems got so bad that in the winter of 98 99 each puzzle grounded most of their fleet of new Cessna airplanes because they were playing with engine problems and a lot of people were scared, there were engine questions . They were having problems with engines that were running poorly, they were fouling the spark plugs and they didn't know why, so they ended up calling Cessna and Cessna was very interested in this because Embry-riddle had the largest fleet of these airplanes in the world and Cessna called them over there. his friends headed home because they were powered by Lycoming engines and before long a tiger team of Cessna and Lycoming experts flew to Daytona Beach to try to figure out what was going on and began investigating the situation and eventually determined the reason.

Of all the problems that Embry Riddle was having with these airplanes is that the instructors and students were running the engine too rich, so they went to look at the Poh and determined that the Poh really wasn't doing very well for them. tipped advice and that part of the problem was that the Poh was training these people to fly these engines pretty poorly and causing all these problems and as a result, I think it was August of '99. I called her and she issued something called service instruction 1497 which was subsequently amended to 1497 a to give a different set of instructions on how to manage these engines specifically how to manage the mixture and what was in 1497 was finally incorporated into a revision of the 172 Poh and so Now, the guidance given to the pilots of these airplanes is much better than back then, but what 1497 was asking for is basically this: First, it said don't use more priming during engine start than is absolutely necessary.

These guys were preparing these engines all the way, although when they were starting up they said that once the engine started, it tipped the mixture to maximum rpm. These were fixed pitch propeller aircraft during all ground operations including restarting. The previous procedure had been to always have the mixture completely rich on the ground during taxiing, idling and starting and, in fact, that is what the Poh had previously requested, but now they wanted the engines to be resting on the ground for maximum rpm, they also called for

leaning

during all climbs above 3000 feet and

leaning

during crews at all altitudes, even at very low altitudes, so this guidance was a very radical departure from what the Instructors had been teaching and using the previous version, Poh said, and of course, once they started following these procedures, all these engine problems magically disappeared. away, and so, if you want to write down what that reference service instruction says, it basically says that we want the engine to lean at all times, except: we, the only time we want the mixture to be completely rich is when starting the engine. when the engines are cold and on takeoff, if you take off from an airport with a density altitude less than 3000 feet, at any other time we want the engine to be lean and, again, this was diametrically opposed to what the flight instructors They had been teaching. and the students had been doing and, frankly, it's diametrically opposed to what I was taught when I was a student pilot in the sixties.

I was taught, yeah, you know, leave the mix control on unless you're above 5,000 feet, that was the conventional wisdom. was not very prudent so if we take the lycoming service instructions we can create a very simple minimum pitch checklist and let me go over it with you and this is a checklist that would be appropriate for a simple airplane that has a The instrumentation basic engine doesn't have an engine monitor or anything, you just know a simple type of airplane with a fixed pitch propeller, whether it's a Cessna 172 or a Piper Cub or whatever, but let's talk about a minimum pitch checklist which will keep it in a reasonable ballpark for a simple airplane and then once we've done that, we'll get into more complicated things and talk about, ultimately, how I fly my own airplane, which is a very sophisticated turbocharged airplane with fuel injection. of fuel and with fuel position adjustment. injectors all sorts of things but let's start with something simple so a minimum lean checklist would basically include the following, firstly as I said rich mixture should only be used in two situations to start the engine cold and for full power operations which basically means taking off from a low altitude airport and then only other words should be used, full rich could only be used for a minute or two at most we want to operate at full rich very occasionally only for very short periods of time and only under these two specific conditions when we first start the engine cold and when we take off from a low altitude airport and are basically pulling something close to 100% power.

The second rule is that for all idle taxi ground operations, start. anything like that we always want to lean, we always want to lean into the ground and lean at maximum rpm, maximum rpm by definition is the best mix of power. In fact, I lean a little more than that on my airplane, but lean at maximum rpm. It's something that's easy to do, it doesn't require any fancy instrumentation, you can do it on any aircraft no matter how simple and it'll keep you in the ballpark, so if we're all in ground operations, including preparation, we want us to support it.

Maximum RPM most Poh's in the world say make your feed completely rich like homing actually said that until a couple of years ago when they revised their guide, but we don't want to do that, we want to be Lean to the best mix of power, which is the maximum rpm. When we are doing our pre-flight preparation for takeoff and climbing above a density altitude of 3000 feet, we want to lean to achieve maximum rpm, so if we take off from a high altitude airport, I want to be lean to get the better power mix, this assumes a fixed pitch support for a more sophisticated player playing egt, etc., we will have a different rule, but again, this will keep you in the ballpark and you can do this on any cruiser plane. at any altitude we want to lean to the start of engine roughness, in other words, lean until the engine starts to whine and then rich enough to restore smooth running, no more than that, we don't want to be as lean as possible without the engine complains and that's the entire checklist, so if we want to summarize this on one slide, fully rich just for cold start and takeoff for ground operations, leaning at maximum rpm for takeoff below 3000 feet, we want be completely rich to take off above. 3000 feet, that's the altitude we want to tilt from EXOR p.m.

For climbs above 3000 feet we want to rely on the Mar p.m axis. and for cruising at any altitude we want to lean as much as we can without the engine complaining about leaning to the start of the roughness and that if you fly a really simple airplane you're excused, we're done, that's all you need to know. I'll keep you out of trouble now, as you can see, this is rocket science, but since it's still early, we'll go a little deeper into rocket science and get a little deeper into the topic and get started. talking about how you could tilt a more sophisticated airplane, so I'm going to go from cookbook mode to theory mode for a while, talk about the things you really need to know to understand why we do what we do and then towards the end. , I'm going to go back to cookbook mode and give you a cookbook for all the sophisticated ones out there; that's the plan here, so let's start by talking about power rich mode and why running the engine in rich mode is a terrible idea.

It's a terrible idea because Full Rich is too rich. Our airplane engines have their mixture set to be insanely rich which makes their control all the way to the Full Rich position and the reason they are an airplane there, they are set that way. The road is really too crowded. First of all, we need a tremendously rich mixture to start the engine when cold. Now most of us are used to car engines, lawn mower engines, and all kinds of other engines, and literally every other type of engine we work with. In addition to airplane engines, they have some enrichment device that is used to start older cars.

Nowadays it is called a choke. Many of our cars have computerized fuel injection and the computer has an algorithm that knows the engines are cold and gives it an extra boost. mixture to start if you start your briggs and stratton lawnmower you know to pull the choke lever before pulling the starter track otherwise you can walk away forever and the engine will not start because these engines require a rich mixture to be able to start when they are cold, butWe also know that once we start the engine we have to get rid of that abnormally rich mixture if you know if you started your Briggs & Stratton lawnmower and then forgot to turn the choke and try to go mow the grass, the poor lawnmower would be spewing black smoke from the exhaust, I would be very, very unhappy.

I'm old enough that the first car I learned to drive in was a Plymouth 259 or something like that. It actually had a manual choke control, you don't see that anymore, but it was like a lawnmower. You had to pull the choke out to start the engine and then once the engine started you would push the choke back on airplane engines. The few gasoline engines we've dealt with that don't have a choke, so they're just set up to be very, very, very rich and once we start the engine we're supposed to remove the mixture control if we don't.

Don't make yourself running the engine with this abnormally rich mixture and it's not good for the inch. The other reason we set up a very rich mixture in aircraft engines is because, unlike almost every other type of engine we deal with, whether it's many engines, automobile engines or whatever, we run aircraft engines. the planes at one hundred percent power, we do them regularly, we do it literally every takeoff, as long as the airports have a fairly low elevation. and when you run an engine at one hundred percent power, you need to give it an extra rich mixture to achieve what's called a proper knock gear to prevent the fuel from knocking because you're pushing it correctly - its octane limit, so We need this extraordinarily rich. mixture for both cold starting and full power operation, but we must understand that that very rich mixture is completely inappropriate for any circumstance other than those two things and we must make sure that we do not run the engine completely rich at any time. time apart from those two strokes and during those two strokes we will do it very briefly, we are just going to have the engine to mix everything rich, you know, maybe 30 seconds when we start the engine cold and then we will lean it once the temperature of the cylinder head starts to register and we're only going to have full rich mixture on takeoff for a couple of minutes at most, so that's really important, so again if we use full rich mixture at any time.

Other times besides those two, it's like trying to drive your old car or lawn mower and forgetting to tighten the choke. It's really bad. Here's an interesting thought experiment to get our heads in the game. Imagine that you have a bucket of gasoline, make it one hundred low, let you, if you want, light a match, throw it in the bucket, what happens, nothing happens, the match goes out, you can't light a bucket of gasoline with a match, the bucket of gasoline is very Rich mixture is too rich to burn, so if you drop a match into a bucket of gasoline, the match goes out and then, and it's a very short story, nothing happens.

If we want this gasoline to really burn, we have to mix it with air. and we have to get a fuel-air mixture that will actually sustain combustion, so one way to do this is to saturate a rag and then drop a lit match onto the rag. That saturated rag is giving off gasoline vapors that are a mixture of air and fuel, and usually if you saturate a rag and then drop a lit match on the rag, the rag will start to burn, they call it Molotov cocktails or something like that. , it is not a very pleasant burn, it tends not to be a very hot flame, it tends to be very dirty and produces a lot of ugly black smoke but it burns a mixture of fuel and air, that is, it is a rich mixture but it is capable of sustaining the flame well. combustion and if we want to make that burning rag burn hotter and and get rid of all that ugly black and black smoke coming out of it, we can blow air on the burning rag, call it.

By fanning the flames by blowing air on that burning rag, we are creating a leaner mixture, there is more air for a given amount of fuel and if we blow air on that burning rag we will find that the flame gets very hot and the dirty smoke becomes much less dirty because we are now much closer to a chemically correct mixture where combustion is relatively complete and there are not many unburned combustion byproducts, however it is a very good idea to light the red egg first and then turn on the fan if we turn on first the fan and then we tried to turn on the cloth.

If we won't manage to burn the rag because to turn on the ignition we need this very rich mixture, then we add a little more air to get an efficient mixture, so if you have that image in mind, you will have an idea. What we're trying to do with mixture control in an aircraft engine: we want to start the engine with a really rich mixture and then we want to lean it so that combustion is reasonably efficient. Here's a diagram that came out a little ugly. an old Pratt Whitney manual for an old radial engine, but it sort of illustrates the kind of general envelope of the air-fuel mixtures that are capable of supporting combustion and I don't know how well you can read this because it's a bit busy, but You will see that on the vertical axis is the percentage of power from zero to 100% and on the horizontal axis or at various air and fuel ratios, start with the really rich ones on the right and move to the really poor ones on the left and you can see from this diagram that gasoline is capable of sustaining combustion over a fairly wide range of air-fuel ratios ranging from about one part fuel to eight parts air on the rich side to one part fuel to eighteen parts of air on the lean side. and virtually any mixture in that fairly wide range of one to eight to one to 18 is capable of burning if the mixture is richer than one part fuel to eight parts air by weight then it will not burn, the mixture is too rich to we burn ourselves if it happens in an engine we say we flood the engine if you drop a match in a bucket of gasoline it will not burn because it is too rich on the other side if we get the mixture to be leaner than about one part fuel to 18 parts of air by weight, the mixture is too lean to burn and that is what happens when we pull the mixture control at the end of a flight, we generate a mixture that is so lean that the engine shuts down because the mixture is too lean to burn , but practically any mixture in that envelope from 1 to 8 to 1 to 18 is capable of maintaining combustion in such a wide envelope, there are several interesting mixtures in approximately one part of fuel to 12 and a half parts of air, we obtain what is called better power. mixture which is a mixture with which we can get the maximum power from an inch, it is not the most chemically efficient mixture, it is actually a little richer than that, it does not provide the cleanest exhaust, in fact, when we operate with the best power mix that exists. a good amount of carbon monoxide in the exhaust, if you have a carbon monoxide detector on your airplane, a sensitive digital one, you can tell the difference with the carbon monoxide readings in the cabin between a full rich takeoff and when you bank the mixture to rise if Observe a dramatic drop in carbon monoxide, but it is the point of maximum power.

Call it better power mix in an airplane with a fixed pitch propeller. It is the mixture that gives the maximum rpm. If we lean a little more than that to about one part fuel to 15 parts air we get what is called a stoichiometric mixture, which is a fancy term in chemists that means the chemically correct mixture. where there is exactly the correct proportion of fuel and air so that the combustion is as complete as possible and at the end of the combustion the least amount of unburned elements remain. combustion byproducts as possible, there is no excess unburned fuel and no excess unconsumed oxygen.

That stoichiometric mixture is what we as pilots generally call maximum egt because it corresponds to where the GT gauge, if we have one, maxes out if we continue leaning just a little bit past stoichiometric and get to the lean side of peak egt or what is called pico lena, we arrive at something called best economic mix. The economy-based mixture is the mixture in which the engine essentially gets the best miles per gallon if all the The cars we drive today run at that maximum Lena rpm, invest it with the best economy mixture, not both because it offers the best economy but because it minimizes the bad stuff in the exhaust and everyone is worried about the environment these days, but if you have a modern car. with a computer controlled engine, it basically runs almost all the time on the lean side, a peak in the region and with the best economy, you notice that when we get to the lean side, the power starts to drop a little if we are operating with the best economical mixture, at a ratio of 1 to 16, the engine only generates about 90 percent of the power it was capable of generating with this power mixture, but it does so much more fuel efficiently and we will get into in some specific details.

There are numbers on that, but anyway the envelope of where an engine is capable of operating and it's a very, very broad envelope and there are some interesting specific points in that envelope that we just talked about, so again, just to review stoichiometry, is the chemically perfect ratio is a useful relationship for us to use as a reference point, we generally don't fly in stoichiometry, but it is an interesting reference point because it is easy to determine if you have a stoichiometric mixture of ETH or if the relationship is chemically perfect occurs at the peak. egt and since this is usually easy to determine from the cockpit, we use it as a reference point and then we talk about operating so far on the rich side of the peak or finally within the peak and when we talk about where we say peak, really mean stoichiometric mixture or chemically perfect mixture, as we said, the best power mixture occurs on the rich side of that chemically perfect ratio, uses about 20% more fuel than stoichiometric and adds only about 3% more power, it is not a good option to use 20%. more fuel to get only 3% more power, it is even worse when you consider the fact that air speed varies with the square root of power, so adding 3 percent or adding 3 percent more power using 20% ​​more fuel only gives you about one and a half percent more speed, so we typically don't want to fly with the best power mix unless we absolutely positively need the absolute maximum power because it will It's about maximum performance in a maneuver, but that's usually not where we would want to run the engine with the best power mix.

I mean, just because it's not very economical, we don't get much airspeed for that substantial amount of excess fuel and today gasoline would be six or seven dollars a gallon, people don't want to throw it up. off the proverbial, although the best power mixture generally occurs between 75 and 100 degrees on the rich side of peak gt if you use egt as a reference, the best economy mixture uses about 20% less fuel than stoichiometric and the price you pay It is a loss. about 10% power or about 5% airspeed, so if we are willing to sacrifice 5% airspeed we can reduce our fuel consumption by 20%, which seems to me a good deal and that's why I usually fly by plane. right in the general vicinity of the best economy combination I operate, I almost always fly my plane on the steep side of the peak and of course I fly with a twin, it uses a ton of gas and every time I fill my plane up or something.

Sticker clash these days, so I'm pretty sensitive to two fuel economy and I tend to be pretty sensitive to that one. I'm flying on a plane. The best mix of economy typically occurs somewhere between 30 and 70 degrees of maximum range pitch if you fly with a carbureted engine, you may not be able to achieve that pitch because the engine will start to rough. We will talk a little later about the carburetor engine. Some are doing quite well. Lena Peak. Others are not doing very well. Lena Peak. We will talk about why, to go very far, Lena, tells you that it is better to have a fuel injection engine with position in any chapter so that each cylinder works very close to exactly the same mixture and with carburetor engines we do not have.

We can't adjust the injector, so we can't get the cylinders to perfectly match the mixture, although some carbureted engines do a much better job with that Norris inherently by design than others. a graph showing four key engine parameters as a function of mixture as a function of fuel flow the fuel flow is at the bottom and we have the tilt left and right and these four curves or mark the temperature of thecylinder exhaust gases CHP cylinder head temperature bhp brake horsepower which is the engine output horsepower if we had a hook to a dynamometer and the bottom curve is called brake specific fuel consumption bsfc and it's kind of of inverse miles per gallon the lower that curve is the more fuel efficient the engine is running the best miles per gallon actually occur with a minimum bsfc and those are the four key engine curves that we look at when we talk about mix management, so let me.

First, point out a couple of Keith's spots on these curves. If he looks at the horsepower curve, he'll notice that I have a little star on that curve where the horsepower peaks. The best bet, by definition, is the best power combination on this particular chart. is occurring at a fuel flow of 110 pounds per hour and you will notice that where that occurs, where the best power is produced on the egt graph, you will notice that it is substantially on the rich side of the maximum egt, in fact, it appears to have about 75 degrees, it seems like a peak can probably read this graph better than you.

It looks like the GT peak is about 1525 degrees and at best the EDT power mix is ​​reduced to 1450 degrees, so it seems like on this particular engine the best power mix. it is occurring at approximately 75 degrees on the rich side of the peak. If you now look at the bsfc curve, the one at the bottom, the fuel brake specific fuel consumption curve, you'll notice that there is a star where that curve is at the minimum. that's the most economical mixture, the best economical mixture where we get the best miles per gallon or the least fuel consumption per horsepower out of this engine and you'll notice that's happening in this case, it's happening about oh, no I don't know 87 pounds. for our fuel flow, a much leaner mixture and you'll notice that if you look at the egt curve, the best economical mixture is on the lean side of the peak, it looks like it's around 50, maybe 60 lena p, so Again, the best economy is occurring on the lean side of the peak, in this case around 60 degrees on this particular graph, the best power is occurring on the rich side of the peak, in this case around 75 degrees on the rich side of the peak, let's see a pair. from other points on this graph obviously the stoichiometric mixing is the mixing that occurs at the peak egt and we have a little star there, the best economy that we just pointed out is that it occurs well on the lean side, the best power if we point out that it occurs on the right side of the peak and this point which is the maximum CHT is occurring at approximately 40 degrees on the equipment assembly on the side of the peak and maxi HT is an important value because it also corresponds to what is called maximum ICP, which is an internal pressure of the cylinder, this is the point at which the engine is at maximum.

Emphasize that it is the least friendly place to operate the engine, so to speak, because you are creating the maximum pressure inside the cylinder, the maximum maximum pressure, the maximum pressure in the connecting rods and the connecting rod bearings and all that kind of stuff. and it is reflected in the cabin too. Being the point at which CH T is maximum, we do not have an internal cylinder pressure gauge in the cabin. It would be great if we had it because it would measure the tension in the engine directly, but the best proxy we have in the cockpit is the CH T Gauge because it turns out that the maximum CH T occurs at exactly the same mixture as the maximum internal cylinder pressure , so we use the cylinder head temperature as the best measure we have in the cabin of how much stress we are putting on the engine and we want to manage our engine to keep that amount of stress within reasonable limits so as not to damage the engine and not shorten the life of the cylinders, etc., so let's summarize for a moment before we begin. go further, except for start and takeoff, which are these two exceptional cases that we want to operate with a rich mixture and rich should almost always be somewhere between the best power mixture and the best economical mixture.

We have this very wide envelope that can sustain combustion, but except for start-up and takeoff. total PTO, we are really only interested in a fairly small section of that envelope, which is the section that is bounded by the best economic combination on the lean side and the best power combination on the rich side, normally not There is a good reason to trade ever. leaner is the best economical mixture, not to mention the engine will complain once we start to get much leaner than that and there is no reason to operate on the rich side of the best power mixture except if we need an extra rich mixture To provide that national headroom for one hundred percent power operation or to allow cold starting, those are the only two times we would operate on the rich side of this power mix, except at very low power settings, we want Try to stay away from the maximum temperature area of ​​the cylinder head. which is also the area of ​​maximum ICP or maximum stress on the engine if we want to be kind to the engine and we want to get maximum longevity from the cylinders, etc., we want to be what we want. to try to stay away from that area of ​​maximum internal cylinder pressure or maximum CHT which, as we saw, usually occurs somewhere around 40 degrees on the rich side of the peak now, unfortunately, many pilots were taught to operate almost exactly there, a lot of old pilot operating manuals that were written before people had a very good understanding of these things, it is recommended to operate, you know, 50 rigid peaks and many pilots still do it because that's how they were taught and the primacy of the law was activated and that is the habit they acquired. in that turns out to be the worst possible place to operate an engine, it's very abusive to the engine and it's a real recipe for requiring premature work on the cylinders and burning valves and things like that we don't want to operate in the 40 50 Richard Piech area, unless we're operating at a very low power setting doing a slow flight, you know, Pipeline Patrol or something, where we're flying around it at 50% power or something, but for normal operations, that's the place where we want to stay. far from because that is the most abusive mixture in terms of stress on the and again, if we start with the best power mixture and lean from there, which is say 75 to 100 Richard Piech and lean to maximum GT, we reduce the flow of fuel by about 20 percent and it's only sacrificed when they have airspeed percentage, so it's not really like that, there's not much point in cruising with the best power mix because we burn a lot of gas and don't get much additional performance . to burn that extra gas if we are able to continue leaning from the EGT peak to the best economical mixture that occurs somewhere on the lean side of the peak and which can reduce fuel flow by another 20% while sacrificing about five percent of air speed, so unless you're one of those people who just has to go as fast as possible and if you're someone like me who's more concerned about minimizing costs than getting there, you know, two and a half minutes before and running. at best an economical mixture or somewhere in this area on the lean side of peak is probably a very good place to operate again, not all engines can run there if the engine has a really terrible mixture distribution, It may start to sputter before reaching this poor level, but for many of us at least this is a very good place to be well.

We talked about the fact that cylinder head temperatures are a key indicator of stress and it's one of the things we most want to be aware of when managing the engine we don't want to put too much stress on the engine and the way we do it. is to limit cylinder head temperatures. Here's another interesting little tidbit to keep in mind, as cylinder head temperature increases the strength of the aluminum alloy our cylinder heads drop very sharply and quite non-linearly when head temperature reaches 400 degrees Fahrenheit, the strength of the cylinder head has decreased by 50% if you continue to let the temperature of the silver head rise above 400 degrees Fahrenheit and both Lycoming and Continentals have red lines that are considerably higher than that, the strength continues falling precipitously.

The engines that come normally have a CHP redline on the gauge at 500 degrees Fahrenheit and when you get to 500 degrees Fahrenheit, the cylinder heads have lost three quarters of the cell. of its strength, Continental is a little more conservative, they normally mark the redline on the CH DT gauges at 460 degrees and by the time you get to 460 degrees the cylinder head has lost maybe 2/3 of its strength. like putting one at 500, the Continental at 460, they are too hot, we never want to let the cylinders get close to that heat as those are emergency temperatures, they are not prudent operating temperatures, I personally set a red line for and for any engine I'm flying I will never allow the cylinder head temperature to go over 400 degrees, that's my red line and I actually said I'm kind of a mental yellow arc between 380 and 400.

I don't want to let CHT go over 380 if it goes above 380 I start taking steps to bring it down if it goes above 400 I do something drastic to bring it down so that yellow arc, that green and yellow arc down at the bottom of the chart, that's not what it is on your indicator that's what's in my head, that's where my mental red line, my yellow arc and my green arc are. I wish the gauges were marked that way if they were. I think our cylinders would last much longer because many pilots fly with sellers that are too high.

Head temperatures they think is fine and are taken down the garden path by aircraft manufacturers who define how the scales are marked, but we really don't want cylinder head temperatures to get that hot, my goal. is to not allow CHT to go above 380 on my legacy aircraft on modern aircraft that have a really good cooling system, for example my company manages about 8 percent of the services in the world, we try to never allow them to go above 360 or 365. but 380 for most older aircraft except really new designs is a pretty good maximum target to try to use as a CHT limit and 400 is the highest level I would like a CHT to reach if so out. up, you need to do something right now to bring it down, so if we go back to this graph with the four curves, this is the same graph that we saw before, it looks a little different and it's overlaid on top of it.

These are my red, yellow and green mental arcs for the cylinder head temperature gauge. You'll see there's a mixture area here where for this engine running, this is an IO 550. I think with this in this particular box it's off the Continental IO 550 manual and this engine is running at a 25 inch manifold pressure , 2500 rpm. I think it's running at about 80% power or something and you can see there is a mixing area where the CHT is too hot and we want to stay out. from there and then we can draw a red box around that area where the CH T is above 400 and say we don't want to be there when we run this engine, or we need to be very rich or we need to be at least a little bit.

Lena peak to make sure the CHT stays out of that red box in this case with this particular engine running at 25 inches of manifold pressure at 2500 rpm, which is, I'm guessing, probably a cruise climb setup Quite high, you could say. We need to be one hundred and sixty degrees richer or richer or we need 10 degrees Lena peak or thinner to keep the voltage on the motor within the limits that we don't want to exceed, so this is what is now called a red box concept. I said I'm actually more conservative than that and would really like to keep the cylinder head temperature below 380. 400 is kind of a dead number, but for maximum longevity I'd like to be. kinder the engine a little bit and keep the cylinder head temperature below 380, so if I draw in another box a yellow box around that area and say I'd really prefer to stay out of that yellow box, although if I have to I'll definitely go in I don't want to get into the red box, you see to do that at this particular power setting I would need to be 40 peak lean or leaner, which is a very lean blend, or I need to be ultra ultra ultra. rich, so rich that it is off the right side of the chart to keep the HT sexy underneath.

Now this is a pretty high power setting, but I'm using it to illustrate that the point is correct. More or less this is the red box concept and I've extended it to the yellow box and I'm going to be doing another advanced learning webinar in a couple of months so I'll give you the date when to delve into this red box concept and develop something called redfin and get into some of thisin more detail, but these are the

basics

of this red box concept, we will talk a little bit about the ignition process, if we did, if we could look inside the cylinders in slow motion and observe what happens during combustion, we would see something like this and this entire combustion event develops over a period of about 15 to 25 milliseconds, depending on what rpm they were running, but the combustion event would start between 20 and 24 degrees, sometimes 25 degrees before the point top dead center, when the spark plugs fire, most aircraft engines are timed between 20 and 24, there are small omens that are timed at 25 degrees before top dead center.

I think there are other really old engines that have 228 timing, but since homing has changed their specifications, so it no longer does that, but most engines, if you look at the data plate, specify that timing ignition is between 20 and 24 degrees before top dead center, which is when the spark plug fires or both plugs fire or ignite and ignite the air-fuel mixture and and and at this point it is before top dead center, so The piston is actually still going up in the cylinder, but we have to ignite the mixture very early because it takes a long time, at least in engine terms, before the fire really roars and we start to build significant pressure out of the deal. , so we ignite the mixture early when the piston reaches top dead center and the flame fronts are beginning to organize and in an aircraft engine with two spark plugs we have to ignite the fronts that develop and burn towards the center. of the combustion chamber and the combustion event, if all goes well, it reaches its maximum pressure and maximum temperature about 15 to 20 degrees after top dead center if it is... if for absolute maximum power, I think the sweet spot is about 16 degrees after top dead center, at which point we reach the point of maximum dynamic pressure in the combustion chamber or maximum internal cylinder pressure, we were talking about ICP before and then as we pass that and the piston is moving downward and this burning fuel-air mixture begins to transfer some of its thermal energy to mechanical energy and begins to cool, the mixture expands and cools and then finally, a little later, the exhaust valve opens and we basically say Hey, we've taken out everything we're going to get out of this combustion and the rest we just let out the exhaust valve and remove it in preparation for the next combustion event, so this is kind of the time sequence of what happens in the combustion chamber and what's really important is to note that the maximum pressure has to occur about 15 to 20 degrees after top dead center for this to actually work correctly, but if the maximum pressure occurs about 15 or 20 degrees after the cup dead center, then the geometry of the piston rod and crankshaft stroke are such that the combustion energy can be efficiently converted into crankshaft rotation and, in effect, produce a power significant when turning the propeller and propelling us forward, that is what we want to happen if the maximum pressure occurs too early in the geometry of the connecting rod and the crankshaft stroke and so on are not in a position to allow that pressure to be converted into energy mechanics, so all we do is apply extremely high voltages. engine components and create extremely high internal temperatures, but we don't get that energy converted into useful work, so it's kind of the difference between a gun and a bomb, so the maximum pressure point occurs at this sweet.

A point of 15 to 20 degrees after top dead center is absolutely critical for the engine to be able to produce power in any reasonably efficient way and not get overly stressed, so if we put a pressure sensor inside the cylinder we can actually do this. There are some test cells in the world, this data comes from general aviation modifications in the test cell and from Oklahoma where they install special spark plugs and aircraft engines and those spark plugs have small pressure sensors built in that are connected to two computers and they can display all of this in real time and we take a look at what is actually happening instantaneously inside the cylinder, we get pressure traces that look like this, the bottom trace with the little dotted line is what What happens if we just rotate the engine with the starter motor and with the mag off there is no combustion, the piston goes up, the pressure increases until it reaches a peak at top dead center and then of course the piston starts to go down and the pressure decreases? and we get this non-combustion curve if we turn on the chargers and actually start lighting a fire, in this case at 22 degrees before top dead center.

You can see the effect that fire has. That middle curve represents normal combustion where the pressure continues to increase. right up to top dead center and to a peak in this case it's 16 degrees after top dead center which is almost perfect um and then at that point the pressure starts to decrease and in this case we reach a maximum pressure of the internal cylinder. of 800 psi, which is fairly typical for a normally aspirated piston aircraft engine, turbocharged engines sometimes reach around a thousand if, on the other hand, combustion proceeds too quickly or, alternatively, if we actuate the spark plug too soon and the peak occurs too early.

Finish with that top curve and the top curve which is called detonation shows that, first of all, the pressure rises too much, which puts tremendous stress on the engine and when it starts to rise, in this case, above nine o psi , the fuel air mixture actually starts to become unstable and instead of burning smoothly as it's supposed to, it starts to develop little localized hot spots and generates all kinds of shock waves and nasty stuff inside the cylinder that, in reality, if It's bad enough, it can cause real engine damage, uh, but at the very least you end up with too high cylinder pressure.

You can see that there is instability in the combustion event and basically it is generating a lot of heat and a lot of stress and not a lot of power because the peak. The pressure occurs too early at a point where the geometry that connects around the crankshaft is not yet ready to actually absorb that energy and convert it into useful energy, so that's bad, we don't want that to happen a couple more times. I will review the graphics very, very quickly. Here's an interesting graph of what happens when we vary the mixture from full rich.

You can see the number one arrow completely rich and we tilt it to the best power mix and then we continue tilting. to GT peak and then we continue to tilt it to 50 peak Lena and then finally we tilt to one hundred peak Lena and you can see what happens with the pressure curve and what you will notice is, first of all, the maximum pressure increases . and higher until we get to the best power mixture and then it starts to get lower and lower as we lean further into taking this power mixture, but the other thing you'll notice is that the maximum pressure point is more advanced , occurs sooner as we lean upward. towards the best power and then it starts to lag more and more as we lean beyond that and that's pretty key, it means that in the range that we normally have to play with, which is between the best power and the best economy , the more efficient we run, the slower the mixing. burns and later the peak pressure occurs, so with mixture control we actually have some control over the rate of the combustion event and where that peak pressure point occurs and therefore whether the peak is occurring too soon and if you look closely at this graph, you'll notice that curve number two, at best, power mix, you'll notice how it's getting a little unstable up there, it's actually right on the cusp of light detonation. , it wouldn't be harmful, I would never do it.

Notice that, but with this sophisticated instrumentation that we have in the test cell, you can see that as soon as the detonation starts, if you can see that the curve is not smooth there, it starts to get a little bit wavy, but it goes from The best power mix is getting leaner and leaner, we slow down the combustion event and cause the maximum pressure point to be later and later, so it's important to remember that here is another curve where we multiply the pressure and basically keep everything else identical, but We go from a 25 inch pressure amount to a 30 inch pressure amount and you can see quite dramatically when we do that, that the maximum pressure increases a lot and the peak comes much earlier and we are starting to have a little detonation.

Again, it's not enough to damage anything, it's not enough that you can tell it in the cockpit or through any kind of instrumentation that we have in an airplane, just enough that you can see it in this fancy test cell setup, but something else. which is kind of interesting here, take a look at for example the T's at 25 inches of manifold pressure, the EDT is 1,400 degrees at 30 inches of manifold pressure, we're right on the verge of detonation, look at the egt, it's 39 degrees, it's 100 degrees lower and you I know if I asked a bunch of honor riders if I go from 25 inches of manifold pressure to 30 inches of Mountain Pro pressure, what will happen to the EGT? 99 of them would probably say it's going to go up and be wrong, it went down because there's a fundamental misunderstanding of what it means egt ett is a measure of how much energy we're wasting down the exhaust after the exhaust valve opens it's not a measure of tension in the engine is not a measure of anything bad it's just a measure of how much energy we are wasting on the exhaust valve and with the 30 inches of manifold pressure because we are, the peak is occurring earlier than it should when the valve opens. exhaust valve, which is a good way to On the right side of this graph, most of the excitement is over and there is not as much heat in the gas that we ultimately send to the exhaust, so the notion that the high egt somehow corresponds to high stress on the engine is not only incorrect. but it is almost completely backwards, the measurement of the voltage in the engine is in the cabin, it is in the CHT indicator in the EGT cage, finally here is another table where we vary the RPM and basically leave everything else the same and when reducing our PM, this is obviously a higher 27 rpm controllable image prop plane at 2500 rpm and as we reduce the RPM, you will notice that the maximum pressure increases a little bit, but the peak occurs earlier, why does the peak occur?

Before, because we've slowed down the crankshaft, the combustion event doesn't know that it burns at the same rate as always, but in terms of crankshaft rotation it peaks sooner because the crankshaft rotates slower, so basically we're. By changing the RPM, we are changing the timeline, so by reducing the rpm we make the peak pressure point occur sooner. By leaning the mixture, we make it happen later if we do both at the same time, if we reduce our MP and lean. mixing at the same time the two will probably cancel each other out, it's important to understand, so just to summarize some key points here, if peak pressure happens too early, this is a really bad thing.

Cogeneration will be excessive, that's how we will know at the peak of the cabin. the pressure will be excessive it will be very hard on the equipment if it is so bad that it can happen that the engine components are overloaded if the maximum pressure occurs too late that is not a really bad thing we lose a little power we lose more energy the exhaust valve, so it will probably go up if it is very extreme, where the combustion event is still strong, when the exhaust valve opens we may hear a popping sound, it is called after the shot, where the combustion event is actually complete, eating out of the cylinder. in the exhaust pipe it usually doesn't hurt at all, but it often scares the pilot, but that would only be in a very extreme case where the maximum pressure came very, very late, but the early maximum pressure is a very serious condition, so from the cabin We have the ability to adjust when this maximum pressure point occurs in several different ways.

First of all, we can't do this from the cab normally unless we have had electronic ignition, but the mechanic can adjust the timing by testing the charger timing when sparking. the plug goes out how many degrees before top dead center obviously has a profound effect on where the maximum pressure point will be from the cabin, we can vary the mixture and as we Linnaean the mixture from the best power the combustion event becomes slows down and therefore the maximum point comes later and we can vary the rpm of the propeller if it is a controllable pitch propeller and by reducing the rpm of the propeller we can make the maximum pressure point moreearly, so if we want the peak to be earlier we can reduce the prop rpm, if we want it to be later we can tilt the mixture to have a certain amount of control in the cockpit, even with our silly fixed timing, Magneto , etc., okay, let me, we're running a little late, so let me go over this pretty quick to get the best economical cruise, like I said, leaning the Lena Peak mixture retards the peak pressure point, lowering the rpm does. move forward and therefore if we do both, we keep the maximum pressure point right where we are.

I want to be and so when I go into cruise I will normally substantially reduce the rpm and also substantially lean the mixture to a very lean mixture if we run Lena peak and high rpm which will cause the maximum pressure point to arrive quite late and If It's late enough, we may even get this effect after the shot, which we see from time to time on saree planes and which gets the pilots very excited. It usually doesn't hurt at all, but it makes them quite excited because the engine runs so strange. It sounds like so let's go through another cookbook now and we'll talk about a cookbook for a more sophisticated aircraft with good instrumentation again to start taxi and ground operations.

We want the mixture to be completely rich when the engine is cold and we're cranking it, but as soon as it starts and we start to register any cylinder head temperatures we want to immediately lean into the maximum rpm for break-in we want to stay at the maximum rpm for cranking. that is the best power make more for takeoff if it is a normally aspirated engine Takeoffs will be performed with all controls fully forward, wide open throttle, maximum rpm and rich mixture at maximum except for altitude takeoffs high-density, if we are doing a high-density altitude takeoff and we need an ET meter, we will do that.

We want to lean the engine to achieve the same egt we normally see during a sea level takeoff and if we do that we will be in the right ballpark on a turbocharged engine. Turbocharged engines don't care what the elevation of the field is. They always think they are taking off from sea level because there is a turbocharger that tricks them into thinking they are at sea level, so all takeoffs with a turbocharged engine, regardless of the elevation of the airport, are always done with all the controls. go full throttle rich and full throttle full throttle maximum rpm if you do that and you get an overboost don't try to compensate for it in the cabin a short term overboost is normal if the oil is cold just accept it, it's not an event It's not going to hurt at all if the overboost doesn't go away as the oil warms up, make a note of it and ask the mechanic to adjust the turbo system, but don't try to adjust these things from the cabin, we all interpret the load.

On an airplane we always want all the controls to be fully forward, the only exception to that would be something like a Cessna TR waiting where you don't have an automatic controller on the turbo system and you're actually controlling it manually with the throttle, but the The vast majority of turbocharged airplanes have automatically controlled wastegates and we always want all controls to be fully forward on takeoff and climb. We want to climb at full power up to at least a thousand AGL for safety and then consider depowering to a lower cruise climb power. You don't need to do that, almost all of the engines we fly behind, with very few exceptions, are rated to operate at 100% power, so there is no need to reduce power, but generally, if the airplane is high performance, power will be reduced. to climb once we run out of a thousand AGL just to minimize fuel consumption and minimize noise, you can climb Richard Piech or Lena Peak, but the climbs to Lena Peak are complicated for reasons I won't go into tonight, we'll talk about that. in our advanced lean exempt webinar, so I generally don't recommend them, they're in it, they're there, an advanced maneuver for someone who is very, very comfortable with the Lena Peak operation.

Occasionally I will climb Lena Peak but not very often, I generally recommend climbing a rich peak in a normally aspirated plane, the mixture will normally get leaner i.e. it will get richer as you climb and you will have to compensate for that, so on a normally aspirated engine normally once we get there. than a thousand rpm, if we want to make a reduction, do it with the propeller control, reduce the rpm but leave the throttle completely open. All the manifold pressure reduction you need will be done by Mother Nature as you climb, if it's a normally aspirated airplane and you don't need her help, so at a thousand feet if you want to reduce power, reduce rpm if engine rpm. takeoff is 2700 that's maybe reducing the climb from 2504 but leave the throttle all the way in and just let the manifold pressure drop normally without trying to help it if your fuel system doesn't have automatic altitude compensation and some do but most don't, you have to lean while climbing to keep the egt constant normally in a normally aspirated airplane, in most of them the mixture will. it gets richer as you go up, the egt will decrease as you go up and you need to turn the mixture control back on to keep the ETP constant and therefore keep the mixture constant once we get to cruising altitude it's time to decide what you want to do.

Do you want to cross Richa Peak or Lina Peak and do you want to go fast or do you want to go far? In other words, are you trying to get the most speed out of the airplane or are we trying to get the most fuel economy? of the plane most of the time when I'm flying I fly closer to go far mode than to go fast mode but that's my personal preference but you have to decide what your goal is if you want to go as fast as possible. You want to clean as close to the best power mix as possible without exceeding your EHT goals, like I said my CHT goal is 380 degrees.

I don't want to get hotter than that so if I lean towards the best power mix and my CHT is hotter than 380 I need to lower it like you lower it well if you're Lena peak you lean more if you're richer peak you're rich in more but we want get out of the red box and in my case I want to get out of the yellow box and we know from the previous graphs that we see how that is done, if you are on the thin side of the peak you need to lean to reach further just inside a peak and if you are on the right side of the peak you need to go further, another excited peak usually requires a lot of enrichment and just a bit of incline to lower the CHP due to the slopes of the corners we saw before if you want to go far, which is usually what I want to do I want I want good fuel economy lean the engine until it starts to get rough like we talked about in the very simple checklist this will probably be a pretty Lena peak for most engines it could be close to a GT peak for some cranky carbureted engines like the feel for the 70's and elevated lanes that have notoriously bad mixture distribution, um and then once you've gotten a very lean peak fuel mixture, then if you have a GPS coupled fuel totalizer that calculates what your fuel reserves will be at the destination, which is a very useful device if you fly cross country a lot, you can look and see how much fuel reserve it predicts you're going to have and if there's more fuel reserve than you need and that's normally I always want to have one of ours. fuel reserve, then you can consider using a little more power and going a little faster as long as you still have an adequate fuel reserve, but to start in go-far mode, you should basically go to the best economical mixture, which It is usually inclined. the motor as far as it can lean before it starts to get rough and then you can adjust it from there depending on what your mission requires.

Okay, it's time to descend, put the nose down now if you're in a turbocharged airplane. like mine or one with a fuel pump with altitude compensation then you don't have to do anything the mixture will take care of itself and you just put the nose down and descend if you have a normally aspirated airplane and it doesn't have altitude compensation which most vacuum planes don't, so the mixture will get leaner as you descend, so you'll have to manually richen it as needed and again we'll use the same procedure we did on the way up, only richer. in the mixture it is necessary to maintain a constant egt if you forget to enrich the mixture it is not a big deal because the engine will become leaner and leaner and eventually it will become strong enough to start complaining about you it starts to run rough and you say oh, I forgot. something and then you will enrich it so if you forget to enrich on the descent the engine will remind you but optimally you will enrich it as needed to keep the egt constant whether turbocharged engine or one with altitude compensation fuel pump it does it automatically for you no, i touch nothing when landing, there is a problem here, almost all the Poh say to get completely rich to land Poh SR written by lawyers who fear that if you have to take a turn or miss approach, you may Forgot to turn on the blend control, so they want it to go completely rich for landing.

I say don't get completely rich by landing. First of all, it is abusive for the engine. We learned that from embry-riddle we don't. we want to run these rich engines. Second, we're optimizing for the one-half of one percent case, so we're going to do a loop instead of optimizing for the ninety-nine and a half percent case, meaning I'm going to land and my philosophy is that if you don't trust yourself to remember to press the blend control, if you have to go for a spin, then you need to practice a little more with the CFI until that happens. it becomes automatic, you know, if I have to make a missed approach, I open my hand and push all six levers forward on my calf and everything happens automatically, it's just a reflex.

I practiced millions of times on the simulator, there is absolutely no chance. I'm going to forget to do it, but I don't believe in getting completely rich upon landing. I think it's bad for the engine and that's not the way I teach, although almost all the employees say to do that just for a brief summary to talk about how I fly my own airplane, which is a turbocharged twin and, as it is turbocharged twin-cylinder, the engines are particularly easy to operate. I start with a full rich mixture as soon as the cylinder head temps start to rise after cranking I lean the engine brutally, in fact I lean a little higher than max rpm.

I like to run very, very inclined on the ground. I keep it tilted brutally during the pre-flight phase and then during takeoff because it is a On a turbocharged airplane, everything is always at full throttle, with the throttle wide open, which in my airplane is a 32-inch redline, powerful pressure, rich and maximum mixture, which in a lighter aircraft is 2700 rpm. After getting out of a thousand feet I will reduce the rpm to 2500 maybe 20 350 if I'm not in a big hurry to get up, leave the throttle at full throttle and the manifold pressure at 32 inches. I simply reduced the RPM to reduce fuel consumption and reduce the amount of noise.

I'm doing when I get to cruise, I almost always want to be in go mode so I pull the fuel flow back with a tool up to a nice safe maximum Lena setting and then I look at the fuel totalizer and fine tune the flow of fuel is what I want depending on if I want to go fast or far when the time comes to descend under the nose I will have to carry something else because it is a turbo airplane and the mixture will do itself for me and then when it is time to land I accelerate backwards I lower the gear and the flaps I don't touch the mixture I leave it lean and I land and then that's what I want in the plane keep in mind that the way I fly my plane I open the throttle full take off and I never touch the throttle again throttle until it's time to land, the throttle is wide open for climb, the throttle wide open for cruise, the throttle wide open for descent and if I could find a way to land the plane with the throttle wide open I would do it , but I haven't figured it out yet, but I basically push the throttles all the way down and once I get to altitude I go to Lena Peak cruise and then I usually never touch the engine again, the mixture controls again until I shut down, let the Lena Peak mix to descend and land to the taxi until it is time to turn off the engine.

The fact that my engines are turbocharged with an automatic waste gate and an automatic trim fuel system keeps things very simple, although My Aircraft is considered a very, very complex aircraft from an aircraft workload standpoint. pilot. It is a very simple airplane because practicallyeverything takes care of itself. We review a couple of frequently asked questions. Does not limit CHP to 380 degrees. It's very conservative. Yes. I'm crazy about engine longevity as most of you know my engines are two hundred and five percent tbo right now. Col CH T's translate into long cylinder life and the way I run my engine.

I'm more concerned about a good engine. longevity than I have to get a few more knots, not everyone does it, not everyone has that philosophy and if you want to go fast and you're willing to change a few cylinders along the way, that's fine, but my philosophy is to keep the motor. in a nice low voltage area and it pays a big dividend in terms of longevity. Is it possible that cogeneration is too low? It is possible, but it is very rare. The only drawback to very low cylinder head temperatures is that if the cylinder head temperatures are low enough, there will not be adequate head cleaning and you will start to have some lead deposits inside the cylinders and on the piston crown. and especially on the spark plug, so when the plugs come out for maintenance, check them if they don't.

If you don't have a lot of lead deposits, it's okay if you have a lot of lead deposits on your spark plugs or particularly if you see plugs full of caps, then maybe your cylinder head temperatures are too low, which we rarely see. that's a problem, except on planes in loitering mode, like pipeline patrol planes or surveillance planes or things that fly at 40 or 50 percent power all day long, they can run on a Lenape carbureted engine, it depends on how good or bad the mixture distribution is on my Most carburetors like Cummings can run Lena Peak quite well except some of the experimental ones that have a carbon deduction system which provides more power but ruins the mixture distribution mix.

Certain carbureted Continentals, particularly the old ones from the '70s used in Cessna 180s, notoriously have horrible mixture distribution and are very difficult to operate Lena Peak, sometimes you can get them to run a little Lena Peak with some tricks that don't I'm going to look into it, but your mixture timing is basically horrible due to the design of the induction system, but most carbureted Lycomings run pretty well on a peak, don't lean on a peak, risk burning the exhaust valves not at all, it actually reduces the risk of exhaust valves burning out. High cylinder head temperatures and excessively rich mixtures are the two main risk factors that cause exhaust valves to burn again.

I my engines are a perfect example of the type of tremendously good longevity that can be obtained from operating I Lena pico mis engines. tees, for example, run higher when I drive Lena people who are the engine I think I've already taken care of that, it's a common misconception that high GTS IIs are bad for the engine, but that's not the case , it is the high CH T that is detrimental to the engine. If you want to be kind to your engine you need to pay attention to cylinder head temperatures and keep them at or below a reasonable target, don't try to keep for example low T's, that's just a mistake for turbocharged engines.

Normally we will have a turbine inlet temperature gauge that has a red line typically 1650 or 1750 depending on the turbocharger and we normally want to keep TI t below that red line except for short periods of time, such as when we are doing transitioning from peak Lena to rich and vice versa will normally produce a lime red gobo, it doesn't hurt anything unless we keep it there for a while. over a long period of time, if you are interested in this topic, there is a wonderful course available on advanced pilot seminars, advanced pilot communication, it is expensive, they do a live course, usually twice a year, it costs a thousand dollars, they offer a course two and a half days. a very good online course that will take you several days to complete and will cost four hundred dollars, but if you want to become a real guru on this topic and go much deeper into this than we will be able to do, this is a great course.

I'm doing a follow-up webinar in July, an advanced class on learning where we go into some more elaborate stuff and I go into the red box and read Jen's material, so we'll do that in a couple. months and with that Tim, I'm sorry we're a little late, I'm not sure if we're going to have time for questions or not, but okay, Mike, good man, that was very, very good information. There are a lot of misunderstandings out there, I can see it even by the questions we ask, we have a lot of questions, but I'm sorry folks, we won't be able to reach you tonight, we're past our leave, I'll just make you an offer.

Mind you, I tried to answer before answering some of the questions strongly in my FAQ, but for those of you who had questions that weren't answered and I'm sorry we ran out of time for Q&A, go ahead and send me a email. questions, my email address is on the screen right now and I will do my best to answer each one of them, as I mentioned I am actually having minor surgery so I may be out of order for a couple of days but I'll get back to you with any questions. Email me and I'll get answers.

Thank you very much for that offer, Mike. I'll pick a question here that's been repeated several times and that is, what about new engines and leaning on a new engine? What kind of recommendation? Would you take it to mean break in, yes, break in, okay, break in is an interesting topic, it might even be one we do a webinar on someday, but to make a possibly long story short. To install a new engine, we want to run it at very high power and we want to run it and it will run at very high cylinder head temperatures because there is a lot of friction in the cylinders, so we basically want to run it at the same speed. power as we can while limiting the CH T to a reasonable value, but one that is a little higher than we would normally accept.

I set a maximum cylinder head temperature for taxi flights of 420, which is higher than my normal pop-up temperature or My normal limit of 400 is obviously within the manufacturer's redline, but it is higher than I would normally like to see , but the key is that if you run the engine very hard, most of the break-in should be completed within an hour, so my break-in method that has worked many times very successfully is to run the engine as hard as possible. as close to full takeoff power as possible for about an hour, doing whatever is necessary to keep the cylinder head temperature at 420 or less, which is typically a rich, high mixture. air speeds very flat rises Cal flaps fully open if you have Cal failures basically all you can do to keep the cylinder head temperatures cool and you should start to see the cylinder head temperatures drop noticeably within the first hour, hour and a half approximately the time at which 97% of the settlement process is completed.

I think that's probably all I should say. Well, good information and a webinar on that would probably be an interesting topic for a lot of people. Well, Mike, thank you very much for your For your time tonight, great presentation and, as you pointed out, the advanced learning class as it stands on July 3, which will be Wednesday night at 8 p.m. Central Time, so with that folks, thank you all for tuning in tonight.