By John Deakin ©June, 2013
This article may be copied, printed and posted anywhere,
PROVIDED it is quoted in full.
A Little History
In the year 2000, Lycoming wrote a paper titled:
Rick Moffett, the VP of Engineering at the time, probably wrote it.
I did a rebuttal column on it, and it was posted on AvWeb as “Pelican’s Perch #42.” shortly thereafter, in May of 2001. George Braly, of GAMIjectorTM fame begged me to withdraw it, as he felt Lycoming was having a change of heart, and the column might make the situation more difficult. I did so.
Now, more than 10 years later, that dreadful document is still on Lycoming’s website, in spite of several promises by the top executives to take it down. Ignorant people skim it, and say “I follow the POH and use this document to fly my aircraft, not the advice of some fellow on the Internet.”
In my opinion, Lycoming should be writing this rebuttal, and apologizing to the GA community and George Braly for publishing it the first place.
So, here is that long-suppressed column, updated to reflect my thoughts today.
I find Lycoming's treatise ignorant of the facts, condescending to the reader, insulting to the intelligence, and full of "fuzzy logic." I'd like to tell you why. I'm going to extract snippets here and there, place them in italics, and then comment in normal typeface, much as we commonly do in email.
In order that you may judge for yourself whether I have taken anything out of context, the entire document is available at:
(The link is broken, apparently removed by Lycoming. Please stand by.)
Dumb and dumber
Make no mistake, I like both companies! Both build fine engines that last a long time, and operate with fuel specifics that are better than the most modern automobile engines. But both companies have problems with quality control, and their warranties are questionable.
Neither company has the expertise to properly operate their engines. Let me illustrate with a quote from our APS course:
CMI (nee TCM) and Lycoming ARE experts when building an engine, and telling us what the limitations are! But they are NOT expert at anything to do with FLYING those engines, because they do not fly them. They are limited to very primitive test stands with none of the sophisticated Engine Monitor Systems (EMS) owners install today. In fact, neither company has even mentioned them in official publications of which I am aware. It’s been 30 years and more!
The official attitude seems to be (figuratively and condescendingly patting us pilots on the head), “Just operate the way we tell you and you’ll be ok.”
I am often asked in reference to LOP (Lean of Peak EGT) operations: "But what will this do to my warranty?" Both companies have stated, in writing, that operating their engines LOP will NOT invalidate the warranties. They waffle a bit by going on to say, “improper operation will.” This word has apparently not trickled down to the “Tech Reps.”
While I'm at it, let me take a swipe at "field tech reps."
Lycoming and TCM field tech reps seem to me to serve but two purposes. First, if the engine is running at all, no matter how badly, they must be able to look you right in the eye and keep a straight face and say, "Oh, that's normal." Second, if the engine has failed catastrophically, it is their job to find any scrap of evidence that will allow them to say: "Pilot abuse, not covered by warranty."
I’ll never forget the Lycoming “Tech Rep” at the Arlington WA airshow somewhere around 20 years ago whose sole contribution to the discussion was literally screaming, “I wouldn’t recommend lean of peak to my worst enemy!” He said this over and over as if bombast and volume made his point.
As with any rule, there are exceptions -- and I suspect the good field tech reps will mostly agree with the above.
But I digress...
Okay, enough of that, let me walk you through Lycoming's white paper on LOP operations.
There are many "experts" today with new products and techniques to help customers in the operation of their engines.
Thank goodness for that! The factories sure aren't doing anything! Notice the condescending quotation marks around "experts." It is astonishing to me that TCM and Lycoming don't JUMP on some of the latest research, with an attitude of "Tell us more!" We can all learn something from almost anyone -- and believe me, those two factories could learn a lot!
One that is receiving public attention by way of aggressive advertising is a company manufacturing fuel injection nozzles and espousing an operating technique that is "better" than that recommended by the engine manufacturer.
Gosh, whom DO you suppose they mean? Could it possibly be George Braly and the GAMI/TAT gang down there in three-letter town (Ada, Oklahoma)? Could they be referring to the aeronautical engineer who built and refined the most sophisticated piston engine test stand in the world? The folks who found a wonderful niche market making precision fuel injectors that the factories (TCM and Lycoming) can only dream of? The GAMIjector folks who will quietly read an Internet message from one pilot to another about a slight imbalance in a customer's engine, and will overnight a new injector or two for a try, without even being asked directly? Or the Tornado Alley Turbo folks who thought there might be a problem with a turbo mount, published a bulletin, and sent out parts to all customers, without even being asked? (One customer complained loudly about parts sent that he didn't order. Takes all kinds, I guess.) The folks who spend prodigious amounts of time online and at (free) seminars, patiently answering the same questions, over and over again, responding with REAL DATA and REAL SCIENCE instead of regurgitated old wives' tales?
George Braly having a little fun at Sun N' Fun
"Aggressive advertising"? I see modest ads in a few publications, and a LOT of word-of-mouth advertising by happy customers, who now own about 22,000 engines equipped with GAMIjectors. The TAT shop is booked for months in advance for turbo installations, too.
The newly discovered method of operating on the lean side of peak exhaust gas temperature has been known since Charles Lindbergh employed it to navigate the Atlantic Ocean and Max Conrad established distance records in his Comanche.
Well, we might quibble over Lindbergh, although he certainly did long-distance flying pretty well! The CONCEPT of "lean of peak" wasn't around then (no EGT gauges), but leaning by the color of the exhaust was very common, and the end result was the same. Lindbergh did indeed tweak his three carburetors for a balanced fuel flow for smooth LOP operation. Widespread understanding and use of LOP didn't come until later, towards the end of the era of the great piston airliners, and even then, it wasn't called that, because there were still no EGT gauges. I first saw an EGT gauge in about 1960, and they did not become common for many years after that.
Whether you use the exhaust color (at night), the old BMEP/Torque drop method, or lean of peak EGT, the final mixture setting is about the same, with only minor variations. There are literally hundreds of millions of hours of LOP operation, even if it wasn't called that.
Why not LOP?
In fact, those old manuals were part of the inspiration for the current trend towards better operation, much of it in spite of the Lycoming and TCM factories. During development of GAMIjectors and the techniques to use them, the question was, "Why can't we run these flat engines the same way?
There are two reasons. Primarily because TCM and Lycoming themselves forgot the old methods, AND they did not know how to make engines that would run properly LOP! This was compounded by sloppy specifications, and exacerbated by poor quality control. (For example, TCM injectors, for which the engineering specs are far too loose to begin with, are manufactured so sloppily that they often don't even meet TCM's own specs right out of the box.) To cap it all off, TCM and Lycoming just didn't care, because "fuel is cheap," "that's the way we've always done it," and "pilots are too stupid to do it right."
This procedure was employed on large supercharged and turbocharged radial engines effectively during the era of large transport aircraft such as the Lockheed Constellation and Douglas D-6 (sic).
[Deakin note, Lycoming probably meant the Douglas DC-7.]
Yes. In fact, in developing these techniques, the airlines discovered that these techniques DIRECTLY allowed previously impossible flights (trans-Atlantic operations, for one example), helped to nearly double TBO (to as much as 3,600 hours in some engines), and DIRECTLY saved prodigious amounts of fuel. This was the historical precedent that seemed to hold so much promise for LOP operations in GA aircraft, and I find it nearly criminal that Lycoming and TCM didn't incorporate this knowledge into their engines and manuals decades ago.
Of course those of you who are knowledgeable about that part of aviation history know that there was a full time member of the flight crew, the Flight Engineer, responsible for engine management.
Not so fast! Engine management was indeed a part of the old-time flight engineer's job, with four often-temperamental engines. But the airplanes also had monstrous systems that needed constant attention, and some of the tools were pretty primitive and time-consuming to use. I would also point out that some later airplanes like the Martin 404 I fly today had all those systems, and were quite successfully operated with two pilots.
He did not have to worry about flying the airplane or dealing with complicated ATC clearance instructions. There was a full panel of engine instruments and controls directly in front of him ...
There was indeed a panel full of engine instruments, mostly because there was a wing full of engines! Some had four manifold pressure instruments, and none, to my knowledge, had more than two needles per instrument. Of course there was a panel full! The PRIMARY function of a professional flight engineer is to run the systems and assist the pilots in the overall operation of the aircraft, to spot and correct the mistakes made by the pilots (and we do make them!), and to help watch for traffic at low levels. Sadly, the industry has gotten away from Flight Engineers in favor of automation, and some of the recent accidents may give mute testimony to the wisdom of that. But that is another subject.
My Bonanza has far more INFORMATION available, in a much more usable form, with automatic alarms, most of which is made possible by modern electronics. Many of the functions that used to be performed manually by a human are now fully automated, and transparent to the crew (oil temperature control, for example), and many will now show an alarm if pilot-preset limits are exceeded.
... including a detonation monitoring system ...
If this is referring to the "vibration detector" that came with some of the old "ignition analyzers," (Oscilloscopes) they were a joke, and all but useless. In fact, the ignition analyzers themselves were more trouble than they were worth. Properly used, they were a big help, but far too many flight engineers (and pilots) buried their heads in the hoods, and looked for a problem until they thought they found one, then fiddled with things to "make it better." I have personally witnessed many occasions where an FE would see a perfectly normal power check and runup, then fiddle with the ignition analyzer for long agonizing minutes, in the belief that he could see something wrong. Meanwhile, plugs were fouling, engines were getting hot, and time was a-wasting. In each case, the order was finally given, some variation of "Get your face out of that ^%$#$# thing, and let's go!"
(To be fair, the old "Chinese TV" was useful when there was indeed something wrong with the engine. The FE could sometimes tell the ground crew exactly what was wrong, and with which cylinder.)
... and, in some installations, a torquemeter to avoid critical operational areas.
No. The major purpose of the torquemeter (or BMEP gauge) was to set cruise power by leaning to peak power, then on to the lean side of peak power to some value of power loss. Some said "12 BMEP drop" (R-2800 on the M-404), while others said "10% drop in power." The power sensor was in the nose case of the engine, picked off the outer "floating" ring gear of the prop reduction gearing. We generally don't have that in flat engines, and where we do the gearing system is different, so we cannot easily measure pure power or torque.
Once everything stabilized with the power drop, manifold pressure was added back to regain the lost power, at the leaner mixture. CHT was monitored closely, to make sure the mixture was correct and remained that way.
However, by knowing the relationship of EGT, CHT, BHP and fuel flow, we can now accomplish the same results even more easily with modern instrumentation, monitor it with electronics, and even flash a warning to the pilot if limits are reached, all without the need to set it for lower power first. No more “add back.”
How to run hard and hot while wasting fuel
For optimum service life, Lycoming suggests operating 50 degrees rich of peak EGT or TIT.
It always boggles my mind to see that recommendation from the factory, while they criticize LOP. It's true, if you're at 65% of power or so, 50°F ROP probably won't get you in trouble, and will give you pretty close to maximum power for that manifold pressure and RPM. But the fact is 50°F ROP (give or take a few degrees) will produce the absolute hottest possible temperatures for all parts of the engine.
On an engine like the TIO-540-AE2A, this translates into a difference in cruise fuel economy of approximately 2-3 gallons per hour compared with peak or lean of peak operation.
This is (roughly) a 10-15% savings in fuel, for a small airspeed loss! Airline executives would murder their mothers for a 1% fuel saving! If 15% doesn't seem like much to you, think of nearly a $1.00 discount on all fuel purchases. A permanent discount. Does that sound better?
With a normally aspirated engine, if leaning is initiated at 75% power and leaning past peak EGT is accomplished, it is unlikely (but not impossible) to induce detonation by opening the throttle to regain power.
Where is the DATA for this ridiculous statement? In fact, I have a pretty strong suspicion that the person who wrote this document has consistently ignored DIRECT evidence to the contrary!
In the first place, it is very difficult when running conforming fuel to deliberately induce detonation in the normally aspirated engines, even for a test. You have to work really, really hard at it. Go full-bore with an IO-540 at sea level, and reduce the RPM to 2400 or 2300 while 50°F ROP, cowl flaps closed, and CHTs well over 460°F, and you'll see the beginning signs of detonation. That's about the only way I know to demonstrate it. On the other hand, set the same power and 50°F LOP, and there is no chance of detonation.
Second, by leaning past peak EGT, the detonation margin is greatly expanded. Lean of peak, detonation becomes impossible in any normal flight regime, assuming good fuel. I'd like to experiment with gear down, full flaps, and a prolonged slow-airspeed climb, cowl flaps closed, and 50°F rich of peak EGT, I suppose that might eventually get things hot enough to get some detonation. Maybe.
Thirdly, in all cases, detonation will not occur without a dramatic rise in CHT, which will be obvious with an Engine Monitor if the pilot has set it to alarm at 400°F.
In our initial examples, both Lindbergh and Conrad were operating engines that had little potential for detonation based on the fuel they were using.
You know, I'd love to go back in time and put an Engine Monitor in Conrad's record-setting Comanche. He usually took off at more than double the max gross weight of the airplane, and had to use pretty high power settings at first. He knew all the tricks, but low airspeed, super heavy weights, and high power (at first) are more likely to induce detonation. If he didn't get it, no one would!
What about turbos?
A highly turbocharged engine is another matter.
Spark-fired, gasoline-powered engines have identical combustion characteristics, whether in a lawn mower, a garden tractor, or the old B-36, with six giant R-4360s (4,360 cubic inches of displacement). The RELATIONSHIPS between BHP, EGT, TIT, CHT, and BSFC are identical.
Employing this same technique will put the engine into a narrow operating envelope where detonation is possible if the mixture is richened slightly.
Wait. There is a terrible fallacy, here. Start with a 75% "book" power setting, at the factory- recommended 50°F ROP. I shudder at this near-criminal recommendation, but never mind, that is what the factory says, right? (Actually, it's what MARKETING says, because they want nice big cruise speed numbers and reasonable range.)
Remember, 50°F ROP is the worst possible mixture setting from a detonation standpoint, from an overall heat standpoint, and from a stress standpoint, because the peak pressures are occurring very soon after TDC, beating on that poor piston like the hammer of Thor.
At that 75% power setting, NOTE THE CHT. Remember, this is the HOTTEST it can possibly be for 75% power!
Leaner is cooler and cleaner
Simply leaning from that setting to 50°F LOP will reduce fuel flow and cost you power. It will save substantially more fuel (in percent) than it will cost you in reduced power output and lost airspeed (in percent) and is therefore more economical (makes more horsepower per pound of fuel and more miles per gallon), but ignore that for the moment. The CHTs will be MUCH cooler and the EGT will remain the same (50°F ROP and 50°F LOP are the same EGT). The internal stresses will be FAR less, because the peak pressure has shifted away from TDC, giving longer but gentler "pushes" on the piston and power train.
Now, continuing with our example, assume we're 50°F LOP, less power, further from detonation, and much cooler. Now add back the MP (about 3”) to come back up to 75% power (just recover the lost airspeed on a smooth day). In all the engines we've seen, the actual mixture ratio will remain unchanged, or will get very slightly leaner. The person who probably wrote the Lycoming document has seen specific data on the IO-540 engine that demonstrates this, and continues to ignore all the evidence. But you can prove it to yourself with a little thought experiment, or by actual testing!
(George Braly says: "There is no data I have ever seen that supports that idea that adding back 2 -3" of MP during cruise flight, with the CHTs limited to the same value as when the engine is ROP, is going to induce detonation. So long as we add back only a few inches of MP, and limit the CHT to the same value we had when ROP, we cannot possibly cause detonation!")
In fact, testing proves that if you set exactly 75% power at 50°F ROP, and note the CHT, then set up (by whatever means) 75% power anywhere LOP, the CHT will be LESS, by at least 30°F!
In our example here, if we add a few inches of MP to recover the lost IAS, the CHT will be about 30°F cooler than we were when ROP.
Same power, cooler CHT. Same power, cleaner exhaust. Cooler and cleaner is better. MUCH further away from detonation than the 50°F ROP suggested by Lycoming.
Note that it is NOT necessary to go through all this foolishness to set LOP on your engine! On yours, merely set the MP where it will ultimately be, and do the “Big Mixture Pull” to the LOP side in three or four seconds, and be done with it. That brief transit through “The Red Box” won’t raise the CHT by even 1 degree, and again, without a hot CHT, detonation is impossible with conforming fuel.
Richer is cooler and dirtier
Remember, there are an infinite number of MP, RPM, and mixture settings to produce a given HP. Most people have seen just one power chart for their airplane for a given power, and this gives them the idea there is one and only one combination of settings to get that power. Most also believe that MP and RPM are the major players. The truth is there are MANY reasonable ways to get any power setting, and ALL of them absolutely require a proper mixture setting.
For example, you can be ROP, and set 75% power with a "best power" mixture (as Lycoming recommends). That's one setting. It will produce the hottest possible combustion temperature and pressure, and CHT.
Now, think about this: You can go RICHER, and that will cause a slight power loss. You can, of course, add a bit more MP, and regain the power. Richer still, and add even more MP, and still have 75%. The power to the crank/prop is the same, but the pressure peak is further from TDC (richer mixture burns more slowly), and the STRESSES are less at the same power. I wouldn't recommend running this rich, since it's very "dirty" combustion, very likely to develop valve guide problems in the future. It makes the oil dirtier sooner, it produces lots of carbon monoxide, it fouls plugs, it costs more money in both fuel and maintenance bills, and it probably reduces TBO.
Continuing our example and starting from 50°F ROP and 75%, you can also lean it a little, lose a little power, regain the power with a little extra MP. Lean it more, add more MP, and still pull 75% power with all settings (if you have enough MP available). In fact, even with a highly supercharged engine, if it will run lean enough, you could run WOT (Wide Open Throttle), with extraordinarily high MP settings, and still be at 75% power, cooler than ever, much further from detonation, with a more efficient engine! But few engines will run this lean and remain smooth, or run at all.
The only reason the engine does not experience detonation is that the mixture is too lean to support it.
No. To be more accurate, a too-lean OR a too-rich mixture slows the combustion event down, putting it further after TDC, where the chamber volume is higher, and growing larger faster, with a greater mechanical advantage. It is at 50°F ROP where detonation is most likely, for that is the mixture setting (roughly) that produces the fastest possible burn, placing the pressure peak the closest to TDC.
At this point, there are a number of factors that can assume control over your engine and cause problems. If the initial leaning is not accomplished carefully it is possible that the engine is not really set at 50 degrees lean of peak where intended.
Yessir, boys and girls, that old evil ole LOP genie is just a-settin' there, waitin' to assume control of your engine. Let me get this straight, Lycoming. Pilots can "carefully" lean to 50°F ROP in accordance with the factory recommendation, but they are not capable of "carefully" setting 50°F LOP? What am I missing, here?
Properly leaning an engine is undoubtedly the least understood area of power management.
Yes, that's true, especially at the factory. I don't see either TCM or Lycoming making any efforts at education of pilots on this subject. In fact, they have been known to denigrate and ridicule those who ARE trying to educate.
During the attempt at power recovery, it is a major assumption that opening the throttle to regain power will not cause a richening of the mixture.
No, it is NOT a major assumption -- it is an empirically determined fact, backed up by readily available data obtained from the very engine we are discussing. On a fuel-injected Lycoming engine, opening the throttle to regain power DOES NOT in fact cause a richening of the mixture. Lycoming has the data that proves this (George sent it to Rick Moffett), but apparently either they don't know how to interpret it, or they don't care. (Even if Lycoming's suggestion that opening the throttle does cause detonation did turn out to be true on certain engines, it would be easily caught and corrected by reference to the CHT on the engine monitor.)
Unfortunately, some fuel metering units tend to provide richer fuel schedules as the throttle is opened and manifold pressure is increased.
This is another incorrect statement, at least in regard to the cruise power range. On all the engines I've seen so far, fuel flow increases with throttle movement, maintaining about the same fuel to air RATIO (mixture) until the climb power area is reached. There may be minor deviations, but again, all the data I've seen suggests the mixture goes LEANER, not richer.
Operating an engine “on the edge” is possible provided the pilot is extremely precise, has good instrumentation, and monitors the engine condition full time.
Lycoming considers LOP to be “on the edge.” In fact, the opposite is true, and here’s why.
Assume the 350 HP TIO-540-J2BD in the Piper Chieftain, with NO ENGINE MONITOR at all, just the way Lycoming likes it, as we don’t want to confuse the poor pilot with all that messy data now, do we? The pilot carefully establishes climb power and leans the engine to 1500°F on the TIT gauge by the POH. Remember, there’s only one TIT probe, and one factory CHT probe that may or may not be on the hottest cylinder.
This is a ROP setting, but in my opinion, it is much too hot! The engine is operating on the edge of light detonation, perhaps even in and out of detonation. Now a little detonation can be a good thing, but I don’t recommend it, as it can lead to medium and heavy detonation, and even preignition, which is definitely not good!
Now suppose one injector becomes clogged? The same fuel flow exists, but now one cylinder gets even less fuel, while five others get a little more. This puts that one cylinder right in the middle of what we call “The Red Box,” which leads to more and more detonation, rising CHT in that cylinder, preignition, and a catastrophic engine failure. Unless that one cylinder happens to be the one with the single CHT probe, the pilot will remain blissfully unaware of the event until preignition eats a hole in the piston, and the engine begins to run rough. This was one of the causes of the Wyalla (Australia) crash in 2001.
Now let’s reset. Cruising along, same airplane, still no Monitor System installed, but now LOP and one injector becomes fouled. That cylinder will suddenly begin running leaner! That will be harmless to the engine, and also it will instantly run rough, due to the leaner mixture. The pilot will instantly know there is something wrong, and can take steps to correct it, with no harm done.
The real experts say, “The ROP pilot needs an engine monitor far more than the LOP pilot does!”
It bears repeating here. If you are at the 50°F ROP mixture setting recommended by Lycoming for ANY power, you are just about as close to detonation as you can possibly get with ANY mixture setting at that MP and RPM. Enriching OR leaning from 50°F ROP will REDUCE the likelihood of detonation and increase the detonation margin.
The instrumentation issue
Unfortunately, many of these variables are out of the control of the operator who is relying on the premise that this is just a simple leaning technique.
Oh, rubbish! The above notwithstanding, NO ONE is recommending these techniques without FIRST having a good engine monitor. NO ONE is suggesting that an ignorant pilot lean without KNOWING what he is doing, and UNDERSTANDING the process. Besides, the 50°F ROP setting is the most critical setting for the ignorant pilot!
If a pilot is NOT prepared to invest in a good monitoring system AND to understand what he is doing, then my best advice is to use full rich for climb, never exceed 65% MP and RPM settings, and lean to any setting that seems about right. For the really abysmally ignorant and unequipped, just leave it full rich all the time! (Sadly, many "modern" CFIs teach exactly that: "See that red knob? Red means danger, don't touch it." And we wonder why people run out of fuel!)
As the last strike, once the engine has been established in the lean of peak condition, and the throttle has been advanced for power recovery, there is no means to confirm that the mixture is properly leaned.
Wrong. The temperatures on the engine monitor will tell the tale. It is TRIVIAL to do this.
The only way would be to richen the mixture to confirm peak TIT. This could move the engine into detonation.
No. It takes TIME to develop conditions for detonation. From a stable cruise condition with the CHTs in a proper range (around 380F or less, for example) it is trivial, and harmless to enrich momentarily to see where peak EGT lies. EGT response is nearly instantaneous, and the readings can be taken before the CHTs move more than a few degrees higher. This has been confirmed time and time again in the test cell at GAMI in Ada. In fact, it is possible to go from full power full rich mixture, straight to LOP in one stroke, without a trace of detonation, provided one does not linger near the 50°F ROP area for any significant period of time. By “significant” I mean one or two MINUTES.
It is also not possible to confirm what margin remains between the setting and the onset of detonation.
Lycoming is being seriously disingenuous here. Think about this. It is equally impossible to confirm what the detonation margin is at 50°F ROP! What's their point?
At least when operating LOP the CHTs will be at least 30°F F cooler, and that alone creates a better detonation margin. An intellectually honest analysis would seem to indicate that trying to set 50°F ROP is far more hazardous to the engine's health than trying to set 50°F LOP.
But it certainly is possible to check the detonation margin in the test cell! From that, some rough guidelines emerge that maintain a HUGE margin LOP, FAR more margin than 50°F ROP will!
The lean of peak methodology places strong emphasis on proper pilot techniques, accurate calibrated engine instrumentation...
What's wrong with that? Flying itself depends on that. No one ever said otherwise. Besides, if you are setting LOP, the actual accuracy of the instrumentation is not nearly as critical as when setting ROP.
...does not allow for confirmation of the proper mixture setting.
Wrong. I'll bet the folks who wrote that document have literally never been in an airplane with these techniques in use. The techniques are easier and much safer than the factory recommended techniques. In fact, I've had passengers comment, "Gosh, you sure don't seem to fiddle with the engine much!"
Any lapse in either can be financially costly or worse.
Especially operation at 50°F ROP!
The punch line
Lycoming is in complete agreement that it is possible to operate an engine on the lean side of peak TIT. It is done on engines in our well-instrumented Experimental Test laboratory every day. There is nothing detrimental in operating an engine in this manner.
Thanks for that, Lycoming! Some honesty at last, although this doesn't go the distance. LOP is cleaner and cooler, and cleaner and cooler is better for the engine.
Let me repeat what Lycoming states:
There is nothing detrimental in operating an engine in this manner.
How then, can the author of that Lycoming document threaten loss of warranty for LOP operation?
In the sales literature provided for this "new" technique, it is stated that Lycoming recommended this operational procedure in an owner's manual that dates back to the late '60's. No mention is made why it is no longer recommended on our present engines.
There seems to be a logical explanation for that. That's because Lycoming (and TCM) won't bother to do the quality control and set the specs high enough to ensure that the engines will operate smoothly when LOP. It's that simple. The stock engines usually CANNOT be operated LOP because of uneven mixture distribution among the cylinders, except a few, like those on the Malibu, and even those often require adjustment (with GAMIjectors) to run properly lean of peak.
The fact is that the technique of operating lean of peak and power recovery was discontinued due to the resulting increase in service issues. Burned pistons, valves, ruined rod and main bearings were traced to the inability of pilots to utilize this technique with the instrumentation and distractions found in the typical general aviation aircraft.
Wrong, again. The reason was that Lycoming (and TCM) did not EDUCATE pilots as to the real processes at work. LOP was a scary idea then, and far too many pilots would set the book power settings, discover temperatures that were hotter than they liked, and would ENRICH (rather than further lean) just a little (to be "safe") over book settings, without regard for the actual results if they could read them at all on the factory-supplied instrumentation. By enriching a bit from the lean side at the very high power settings (recommended by the factory), owners and pilots INCREASED the heat produced, increased the power produced, and increased the stresses on the engine. Had the factories emphasized, "Try a little leaner," there might be a lot more Malibu’s today.
The end customer might be assured that if there is a problem resulting from engine mismanagement, the "experts" with their fuel nozzles and leaning recommendations will not be offering to pay the warranty to repair or replace the engine.
Neither does Lycoming or TCM, no matter what the cause! Well, that's a bit strong. Both DO pay warranty claims, if grudgingly, and sometimes even in cases of mismanagement, because they often cannot prove it.
When asked about this warranty policy in the event of a problem, the answer came back that this is regarded as a "improper operation on the part of the operator".
What? "... the answer came back..." From whom? Who asked? WHO gave that answer? Where has Lycoming or TCM made that statement, in writing, as official policy? Exactly what was covered by this purported statement? "Improper management," or LOP operations? I hear a lot of ignorant claptrap from tech reps that continue to parrot the OWTs (old wives' tales) they learned from who-knows-where, but if this is official policy, it's the first I've heard of it.
Operating an engine "on the edge" is possible provided the pilot is extremely precise, has good instrumentation, and monitors the engine condition full time.
Yes, especially if you're going to operate at the factory-recommended "edge" at 50°F ROP!
In the year 2013, AOPA published the results of a poll asking whether respondents thought LOP or ROP was “better for the engine.” Fifteen years ago, the answer would have been overwhelmingly in favor of ROP, perhaps approaching 100%. Today with better education, better instrumentation (and higher fuel prices) it’s about an even tie. As more and more people become more knowledgeable, that will continue to shift in favor of LOP operation. In fact, there is research going on that will make ROP operation an artifact of history, like the dinosaurs.
This article may be copied, printed and posted anywhere,
PROVIDED it is quoted in full.