What drugs are you on man? I never said I was the font of all knowledge, but I do similarly agree that the texts and flight school training is full of incorrect myths...Old Wives Tails if you will.

The source of the best training package is in Ada OK, USA, some 15-16 hours of B747 direct travel distance away. If you must find the one guy who has done more research than anyone in the modern era, he lives right there! Take your flat earth theories down there and try them out, let us all know how you go. I can't wait.:ok:

I think you tried to be a smart a$$ with your previous "waste of bandwidth" comments on "code for not knowing what I was talking about" and when subsequently found short of the mark you have decided to go to ground.

Funny how you claim you can't run carby engines LOP, I say you can, in fact I do and several different types, and when I explain how it is not something I am prepared to do via a pprune post, you acuse me of not knowing what I am talking about. :=

I asked some serious questions, did I not answer yours? And no I cant give a 2-3 day seminar of pprune, not even the APS guys could pull that off.

Have you ever made the effort to travel to Ada for a training seminar? I believe not but willing to be corrected.

When the student is ready, the teacher appears. Perhaps those who seek the knowledge will gain something anyway.

I am sorry I added anything to this thread, wasted a lot of my time it seems. Strangely enough from the PM's I get wanting one on one tuition and help with concepts of this topic, I usually discover these folk don't post their questions for good reason. Those who want some guidance and pointing in the right direction feel free to PM me at any time

Ciao!

[Pilot DAR in black, other poster's response in red]

'Not kidding, these are Lycoming engines - just about all of them.

I do not peak or LOP operate Lycoming engines, because I have read Lycoming's Service Instruction No. 1094D, which is applicable to: "All Textron Lycoming Opposed Series Engines" (which I am certain would cover a Piper Navajo Chieftain - Though I have only flown "regular" Navajos). It states on Page 6 of 6: "TEXTRON LYCOMING DOES NOT RECOMMEND OPERATING ON THE LEAN SIDE OF PEAK EGT". So I just operate the engines in accordance with the manufacturer's recommended procedures - it's simple!

I have never operated "big" radials, as I have never encounterd any on aircraft associated with Private Flying. When I operated little radials, I did so in accordance with the deHavilland instructions!

I have detonation tested a carburettor modified Continental IO-520D and IO-470F engine. As a result of my detonation (and a lot of other) testing, both these engines were STC approved in C-180 series aircraft to be operated on Mogas. The bulk of my testing was on the ground (where I did purposefully detonate, and observe it), but I did some verification in flight. This modification reduced fuel economy over the injection systems, but the other benefits balanced this out well. Anyone who would like to know how I did it is welcomed to inquire about my DAR (= DER) services for this work.

Poor or bad? - Well they are FAA approved, perhaps you should apply for an STC to change them if you know better....

No. There a lot of very informative and valuable training courses "out there" and I have taken some. However, those which are associated with a design change, or operating change, which are authoritative, are also likely associated with an STC approval for the associated change (if it's applicable to a certified aircraft).

For those pilots who do not have the time or resources to travel to Oklahoma, just read the instructions which come with your engine and aircraft, and do it that way. Yes, you might waste a bit of gasoline - it's just the cost of flying - live with it! You can do a lot of flying with a waste of $10 an hour in fuel, for the cost of a "15 hour" flight to Oklahoma and several day seminar!

Has anyone completed that APS online course? The overview suggests it will make you comfortable using an engine monitor to diagnose a wide variety of engine problems, but for most GA aircraft that isn't exactly applicable. Would it be a useful course for pilots with more typical instrumentation?

With regards education, the JAA/ EASA CPL/ ATPL syllabus adds very little about engine management over the PPL and next to nothing of practical use. It seems very much like a pilot is expected to only ever operate the engine as detailed by the POH and to not think anything else about it: keeping an engine in good condition is something the engineers do!

It sounds from reading my Lycoming manual like they would rather provide a one-size fits all solution with regards leaning to keep things relatively simple. They don't recommend operating at LOP and they don't recommend leaning above 75% power, although they make some exceptions along the lines of if the POH says so! I can quite believe there are more efficient ways to operate an engine in the various conditions that may be encountered in flight than the fairly hard line of the POH, but for most private pilots in single pilot aircraft, ultra-fine engine management is probably a little too much to ask. It's good to aspire to fly as well as possible though, so for anyone that wants to learn how to improve on the manufacturers operational recommendations it's probably definitely worth spending money on extra education even if you aren't going to recover the cost through fuel savings. There probably should be a disclaimer here about not ignoring your POH because you THINK you know better. Make sure you KNOW what you are ignoring and more importantly why.

Anyway this thread was about engine checks and someone mentionecd a static RPM check.

Lycoming:
Something else: Sticking valves - almost always indicated by rough-running on start up which may then smooth out as the engine warms up. There may also be considerable oil leakage. Can be caused by overheating, frequent long periods of inactivity and oil deposits like lead sludge from incomplete combustion.

Fix/ avoidance: preventative maintenance (oil/ air filter). Operate within specified temperature range and check/ top up oil as required. Lean mixture for more complete combustion.

(my bold).

This seems to imply that these are both fixed when the airspeed rises, i.e. that there is no reduction in airborne power, just a reduction during the static test.

Does anybody know how this works?

Surely, truly blocked induction and/or exhaust systems must actually reduce power. Is there no way to tell on the ground whether it is real or apparent?

Genuinely curious - I know zilch about engines apart from my "Aircraft Technical".

I think there is a subset of pilots who are LOP nerds and I mean that in the nicest possible way. That is they have spent the big bucks to buy and install an engine analyzer and learned how to understand what it is saying so that they can achieve measurably more efficient flying with respect to the only metric that really matters, Miles of flight per Pound of fuel.

However for the average PPL flying a trainer/tourer with a simple carburated engine IMO 80% of the maximum possible fuel efficiency can achieved by simply leaning to engine roughness and then pushing the mixture knob up to smooth operation plus a little bit. But most people just seem to fly around with the mixture full rich all thr time :ugh:. The engine should be leaned anytime the aircraft is in cruise. I don't think it is well understood that excessively rich mixtures can be just as bad for the engine as too lean a mixture.

With respect to the static RPM check I will abort any takeoff where I do not see the initial RPM within the POH range. Yes it could be a out of tolerance RPM gauge but it could be something more serious and if it is the gauge the unit should be fixed as it will be impossible to accurately set any power.

BPF
Well said! :D

The500man
Absolutely, and it has been my recommendation they make it a requirement to complete that prior to attending the live course. The online one fills the bucket of knowledge with rocks, the live course ours in a heap more sand, then adds a little water. When the masters course comes out this should almost fill the bucket with water!

I usually find that the only folk who ever knock the course, have never actually attended. :ugh:

500 man and DAR
Some history and it is brief, so dont go getting carried away due lack of details.
Lycoming and TCM (CMI now) have written many manuals, then the aircraft manufacturers incorporated them and modified them to suit specific agenda's at the time. Why did we get the 75% power performance comparisons? To sell aeroplanes! Magazine test articles. So how do you get the best from your plane at 75% or more power? Run at 75-80 ROP of course.

Engineers say hang on a minute, we don't want that, we want more like 150-00 ROP, but that does not satisfy the economy and speed comparisons. So a tug of war begins.

In the old days, operating on the Lean side of Peak was well known and widely practised. The problem TCM and Lycoming had was their carby engines and later the injected engines were so poor in F/A ratio that running LOP was not easy, nor was the instrumentation good either. In one Lycoming publication they basically said pilots were not smart enough to do it!

So.....Factory can't produce a good reliable LOP performer without rough (scary) running engines, so lets just remove the whole LOP side of the graph...Don't Go There! Next problem is without accurate gauges and pilot training the Rich side of Peak is far more dangerous to engine health if mishandled, so lets go full rich until TOC even though we know its full of deposit causing excess fuel, it is just easier. So hence we got the manuals we did.

Next problem is so many manuals contradict each other. I do not have time nore space in this thread to post them all, but believe me, I have them, and its weird :hmm:

As for LOP operations, well they are coming around full circle....and DAR's quote about Lycoming does not recommend....... well that just depends on which publication you read. :rolleyes:

Poor or bad? On second thoughts BOTH!! Yes they may be FAA approved, but check out the FAA A&P exams :ugh::rolleyes: And why would I want an STC for a manual? :ugh:

I am interested in the sensors you used for detonation testing, were they precise pressure sensors with a data capture rate well over 20kHz or even up to 1mHz buried in the heads or were you using a Delta T method on CHT? Accoustics can work of course but in an aero engine not so well. Just curious, as I like to learn anything I can, and this is certainly interesting.

I will let you into a secret :)

LOP does not give you more MPG :)

Once you are stochiometric (peak EGT, or close) you are getting all there is to be had out of the fuel.

People who fly LOP and claim great MPG are simply getting more MPG because they are flying slower.

I don't fly LOP.

The "manual" for an aircraft (and there will be several) is an extension of the aircraft's Type Certificate (TC). The TC usually says something like "The aircraft must be operated in accordance with applicable placards and manuals", which removes the pilot's choice about whether to fly it the way the manufacturer specifies. So if you want to operate beyond the TC - by doing something which the manual says don't, you'll need to supplement the TC with that additional information. An STC, which could be nothing more that a supplemental manual.

It's quite common for STC's to be obtained to approve the operation of an aircraft beyond what the manufacturer approved or recommends, yet without mechanically changing the aircraft. Some gross weight increase, or Mogas STC's are two of many examples of doing this, as well as three STC's I hold that cover hundreds of aircraft types. The aircraft you fly probably has many approved supplemental manuals.

From a Lycoming Type Certificate Data Sheet (with my bold)

"Engines of models described herein conforming with this data sheet (which is a part of type certificate No. 1E12) and other approved data on file with the Federal Aviation Administration, meet the minimum standards for use in certificated aircraft in accordance with pertinent aircraft data sheets and applicable portions of the Civil Air Regulations/Federal Aviation Regulations provided they are installed, operated and maintained as prescribed by the approved manufacturer’s manuals and other approved instructions."

Lycoming's Service Instruction 1094D is FAA Approved

Derrrrrr :ugh::ugh: now tell us something we don't know! Just because they are approved does not mean they are not dumb, full of contradictions or errors. Many are, despite their FAA acceptance. Get over it.

I repeat: lycomings and Tcm's publications often contradict each other,and more recently are endorsing LOP ops. Fact. If you are still in the early 90's, time you started researching again.

Now how about the interesting suff I asked about?

Peter, please show me a reliable data source that backs up that ridiculous statement.

If you want to look at a properly set up engine at say 1000 feet, And it is set up for 80% power with whatever MP & RPM you choose, that engine is say a Lycoming IO540D4A5 all 260 ponies. The airplane speed is say V80 because no matter how you twist it, 80% power will give you a constant result. So if speed is derived by power delivered, and we have the 80% power, what do you think the fuel flow will be for this engine when run properly ROP?*

I have the answers if you are unsure, and I am happy to help, but it is not hard to calculate.

*So then tell me what you think the LOP speed and fuel flow will be?

What do you think the CHT and Internal Cylinder Pressures will be like compared to each other?




Nitery nite;)

I don't know who you are, Jabawocky, but I think you have been to too many seminars :)

I like John Deakin and he has done a huge amount to educate pilots and extract them from the Lyco-Lawyer dogma, but I think they go a little too far in commercialising their courses :)

To back up my statement (LOP does not produce more MPG than peak EGT) I have done extensive flight tests. I can measure fuel flow to 0.1USG/hr resolution, and similarly for the TAS (using the 3-leg GPS GS method).

There are possible second order savings to be had from burning a very lean mixture if running at a low RPM, say 2200, which given the fixed ignition timing we have can produce a better result. I have used this on long trips (example) where one is able to fly at low level (say FL100) where the engine is happy at such a low RPM. But the improvement is really very small and I don't bother anymore. Anyway I often have to go to FL140+ to stay above wx and one cannot fly below ~2400 up there anyway (no turbo).

The manual for the 1980 PA31-325 I fly approves LOP. It even details how to do it. Didn't do it with the stock single point EGT & CHT gauges except once to show the owner and recommend have an EDM fitted. Now I nearly always fly LOP with much cooler CHTs than ROP.

Peter,
hehehheheh ;)

It matters not who I am, it is data backed facts that matter. Play the ball and not the man they say! :ok:

Too many seminars :} Perhaps, but I think like always, you and many others have been to too few! :ooh:

Answer my question please.

I measure my fuel flow down to 0.026GPH, that is irrelevant. The tradeoff for fuel flow Vs Lost Speed is not niminal and hardly worth the effort.

For example at high altitudes as you do, if I go from 37.0 to 40.5 LPH do I go 10% faster? No. I am lucky to see 4%. This is around peak or just ROP, been so long I dont recall the exact numbers. If I go to a high altitude ROP setting burning say 40% more fuel, I am lucky to go 10% faster.

If you do not find similar things, you must be doing it wrong! :uhoh: It just does not make sense.

Now back to my question please, and these numbers I do remember because I took photos.

Back to engine monitors and education for a minute.

Private pilot in his ....say C421, boring along fat dumb and happy. He or she notices the MP on one engine dropped a bit, inch or so.

What should he/she do and when and why?

This is all the info you need. Simple one. By the way even without an EMS, this question applies.

... perhaps a broader applicability that just aircraft publications....

No one is perfect.....

We who write and approve these documents do so in an industry agreed format, and with appropriate quality and conformity checks along the way. It is with the intent of providing properly trained pilots and maintainers the information they need to assure that they can operate and maintain the aircraft safely, and the way it was approved.

If pilots or maintainers do things a different way, it's theirs to justify to whomever should inquire.... I'm not inquiring - I'm not in enforcement or warranty!

DAR,
agreed:ok:

So I gather you also concede thet they are often poor or bad in terms of scientific facts, data and recomended practises then? ;)

So how about a crack at either of my questions? You blokes (blokettes) don't play fair! :E

Unfortunately I cannot concede to such a broad statement. I have found and reported a few errors in approved documents over the years.

Otherwise, the documents are the intellectual property of the Type Certificate/STC holder. They are required to be compliant with the design requirements, not perfect in the estimation of people at large. Indeed, and I certainly have done it, they may be written to be conservative and to provide the required margins of safety and durability. There's often more than the obvious that determines the wording. Let me give you a non engine example:

The Cessna Grand Caravan flight manual states the "normal climbout speed of 85-95 KIAS". You might say: "I can get airborne, and climbout, at a slower speed than that - the plane will do it!". Indeed it will, and I had to demonstrate this at 80 KIAS, instead of 85. It sounds trivial, and the plane handled it fine. However, when the authority then required that I demonstrate a "Vref-5", which meant flying the departure and approach at 75 KIAS, it was un-nerving. Then I was required to demonstrate a land back from an engine failure at 50 feet at the slower speed. That was downright scary (much worse that the 14 spins I'd had to demonstrate in it!).

The book does not say 85 KIAS 'cause that's the best the plane can do, Cessna has built in the Vref -5, and the land back ability margins to the "average" pilot skill, into the speeds. You will never know those margins were there, unless you suddenly find yourself in that situation, and you manage to get yourself out. You'll think it was your surerior skill, but in part it was built in margins of safety.

Eager aftermarket salesmen love to show you what the airplane/engine will really do, and often it will - but with greatly reduced margins. That means super pilot skill may be/is required to compensate. Aircraft are approved to "average" pilot skill, not super skill. If these eager salesmen went to certify (STC) these techniques, they might find that the required margins of safety or durability could not be demonstrated, and for that reason, certification is not available. There's a message there for users - why is it not STC'd?

Going back to the original question I think we instinctively know when something is not quite right in an aircraft we know well!
It is about decision making and part of that decision maybe to do nothing but concentrate on flying the aircraft to a forced landing and not be pulling this or that while loosing the plot on what you should be doing.
If you know the aircraft so badly that you need a fly by numbers instruction sheet then you have to question the pilot not the problem!
I fly jets! We have memory items and we have an emergency checklist.
Any emergency item and its straight to the emergency checklist for that fault!
The main thing is to fly the aircraft! If the engine stops at 1000 feet chances are you will threaten your chances of a successful forced landing by opening checklists and wading through restart items when you should be concentrating on selecting a suitable landing site and flying the aircraft down to a successful landing.
Ok in the cruise and one engine runs rough or there is a vibration and you have plenty of time to experiment, check everything is where it should be and make decisions on whether to divert while keeping the engine going.
As in the jets there could be an argument for having an emergency checklist which is quickly and easely available for different scenarios.
I stress the word quick and easily available as priority is always flying the aircraft not being distracted by wading through books!

Pace

Pace, absolutely a pilot should fly the airplane first, but keeping the engine running or knowing when something is wrong and what that might be shouldn't be excluded altogether if there is time to do something about it. I agree any emergency checklist should be a memory one where possible, but for a rough running engine or if you notice some strange vibration or a power loss, a simple checklist could prove useful.

Pilot DAR, that's a good example. I don't think it's uncommon for pilots familiar with a particular aircraft to start flying it in their own way because they feel they know better than the flight manual. In some ways they may be right, but you can guarantee there is some knock on effect that they would never have even considered. It does make me wonder why all of the applied safety margins aren't detailed in the flight manual though?

DAR, indeed. And that discussion is worthy of a thread of its own.

What concerns me here is, you are reluctant to accept my statement based on multiple manuals from various manufacturers, that are literally three feet away from me and I assure you they are contradicting each other, and known science. Science that pre dates the manuals themselves. Yet you speak and expect the punters here to believe your authorities words.

This has very little to do with the comparison you have just tried to make. Aerodynamic performance is a fairly steady state of knowledge, as best I know the manuals are accurate and the data as you explained is achieved through certification testing. A C208 pretty much behaves the same as all it's brothers assuming no serious mods are done to airframe.

The same cannot be said of engines. The manufacturers manuals vary, and vary a lot, and in some cases are so bad, it makes you wonder how they got published.

To the youngsters reading this thread and easily impressionable think about this for a minute


It is not what you don't know that will hurt you, it is what you know that isn't so!

Still waiting for a couple of questions to be answered.

Seems to me that you are talking out of both sides of your mouth.

When professional highly experienced jet pilots have a rough running engine they go straight to the emergency check list starting with the memory items and then consulting the checklist. Sure sounds like "a by the numbers instruction sheet" designed to deal with a problem to me

So does that mean when a 100 hr PPL has a rough running engine and goes to a checklist that will ensures he methodically runs through the potential causes in a logical order without missing anything, which is exactly my response to the question posed by 500 Man in the first post, you "have to question the pilot not the problem" ?

Sorry I just don't follow your logic. :confused:

You know of all the posters who have contributed to this thread it would seem to me that the quote best applies to you....

As for answers I am still waiting for an explanation on how you seem to be the only person I have ever heard of who could get a simple horizontally opposed carburated engine to run smoothly at a true lean of peak mixture. I have personally never been able to do that, not have any of my very experienced pilot friends had any success with LOP operation on these engines.

So what is the secret ?

BPF

I am not talking out of both sides of my mouth;) We are talking about engine problems which could or could not lead to a forced landing in a single engine piston.
Obviously in a single engine piston an engine problem is more critical than in a jet as the jet will not be contemplating a forced landing into a field.
The Jet and its systems are more complex and the emergency checklist covers many other areas other than engine problems.
The fact that an engine problem in a piston single opens up the prospect of a forced landing means that the forced landing part becomes more critical.
As I posted if you have time then yes go through check lists, experiment with different settings etc but not at the expense of jeopordising the outcome of the forced landing which could be fatal if you get it wrong.
The last scenario I would want is for some pilot to be fiddling around head in books and in the aircraft with an aircraft gliding down to lower levels when he should be selecting a suitable landing area and adjusting the profile estimating winds etc as priority number one.
You cannot compare the two as other than complete fuel starvation the jet is unlikely to ever be force landed the piston single is.
Even so I see nothing wrong with a mini emergency checklist for the single piston as it could be very useful especially if it is readily at hand and actually speeds up the thought process allowing more time to carry out a successful forced landing.
Aiding decision making not hindering it is the key to the use of a checklist in such a situation.
But the best decision making is the pilot who knows every beat of his aircraft and through experience knows where the problem lies and whether it is fixable or not.

Pace

This applies to EVERYONE you included and now I think the punters might be making the judgement call for themselves. Your attempt at insults really does your argument no good at all.

I have told you repeatedly, there is not enough space to sit here and debate how it works with a bunch of flat earthers, holocaust deniers and whatever other descriptions for non believing folk there are.

Plenty of people do it around the world. I am more stunned you have never heard of it and can't accept I am telling the truth. You lot are so bigoted that you believe that everyone else should take your word as gospel and others do not deserve that privilege also.

I promise you, it works on many engines. Most can achieve a level of effective LOP operations in the most economical range 10F LOP +/- a bit if they have a "Conforming engine" strategic use of the throttle position and a scientific application of carby heat. An EMS of some sort with digital fuel flow carb temp etc is damned handy to have also. Not essential but really good to have.

Perhaps if you sucked your pride in for a bit, and realised a weekend in Ada in October was a good idea, you could learn a whole heap more. Maybe you could teach George and Walter a thing or two!

Now how about a quick answer to my questions. If you ever fly a twin and could not answer that question in the first 3 seconds of reading it.... I will not let anyone I know fly with you. I would, because I would know what we saw.

For a certified aircraft, the "gospel" is what the regulatory authority has approved. Other than simple good airmanship, there is not other gospel.

Any "others" who wish the privilege of their word also being gospel, should go through the process to create, and have approved, a modification and/or supplemental instructions. That way, pilots will know what they have as authoritative instructions with which to operate the aircraft.

For those older large radial engined aircraft which I am aware were operated LOP, 'cause I had a friend who used to do it, I'm certain that there was an approved document describing that procedure - why not so for GA aircraft?

Well some were even 25 years ago. If you really knew your stuff, you would know the exact model I refer. I am not saying you do not know stuff, but clearly there you are talking out your.. :mad: again.

As for several others, in the POH's some say do then a page later contradict. You tell me why? Its baffling to me.

As for the rest of the manuals, the manufacturers are either too lazy, too incompetent or just do not want to admit they got it wrong. Mind you I have seen an email from one prominent employee of a major manufacturer openly admit the manual writing was in fact.....very poorly written. He should know, he approved it!

It is about time you came out of the dark ages, circa mid 80's and stopped being so hard of learning.

And what is your answer to my questions?:ok:

I can't run LOP with our carb engine, and we have an EMS. Runs rough as hell.

Absolutely no argument there, but my posts on this thread are aimed at a low time pilot that is flying a rental aircraft for possibly the first time in that particular airframe. So what do advise for them ?

Not one attempt at answering a few simple questions. Very disappointing indeed. I would have thought with such a strong technical base on this forum there would have been several pages of replies.

Anyone wanna have a guess? :zzz:

Well, the only question that needs answering, as far as I'm concerned, is this one:

So by all means go ahead, Jabawocky, and answer that one, instead of pretending to be the wiseguy without actually delivering.

(The aircraft I fly most often has an induction system that's so unbalanced that the POH doesn't even have instructions for setting the "best economy" mixture. All it does is "best power" (max RPM), and all the performance tables, including cruise, are based on that. So getting that one to run LOP properly would be a major breakthrough.)

Disappointment happens Jab.

My participation on Proone is voluntary, as is my choice to not be further drawn into nonsense. I find many questions I believe to originate from the desire of a pilot to broaden their knowledge, and improve their skills. Where I can, I help. In other cases, I charge for the same service to the aviation industry, and I then often sign an STC for the modification.

Some questions on Proone I suspect are not "true", and asked in an honest spirit. I generally ignore them. Some statements on Proone I judge to be more unhelpful to new pilots than helpful to anyone, and perhaps leading the unwary pilot into troubled aircraft operation. Where I have experience, I will challenge those (as several other extremely skilled Prooners have here). The challenge not so much toward the poster, but more so everyone else sees the challenge, and takes the offending statement with a grain of salt. It is each reader's responsibility to judge the credibility of answers in their personal flying context. But, a few credible challenges could be the "red flag popping up" for those pilots who are impressionable.

For me personally, lean of peak operations pop up a lot of red flags. But, that is now well evident to readers here.

Does that answer your question about your being disappointed?

Two STC's were issued, based in part on my ground and flight detonation testing, which was done by my real time observation of cylinder pressures, measured by a piezoelectric sensor. This was my third detonation measurement system design (and the first which worked well). These tests were ultimately supervised by a national powerplant expert, and witnessed by a Transport Canada powerplant engineer, to his satisfaction. With their concurrence, and two STC's, I'm satisfied with my work. If others are not satisfied, I'm not worried.......

DAR

I am genuinely interested in your detonation data aquisistion, mainly because very few people ever go to the length to measure that properly.

Just because I challenge the comments of other matters does not mean I am taking the same challenge to this topic.

So were your pressures recorded in a digital logger at a high frequency? There is some interesting work being done considering the detonation event and the pressure waves bouncing around after the peak event. Your experience might make for good reading.

Now as for the questions I posed, which were challenging the comments about pilot education.....I am disappointed nobody bothered.

As they say, you can lead a horse to water, you cant make it enjoy the view.

Another matter altogether, but that just means a greater degree of understanding is required. Especially with students and owners.

More red flags should show up with ROP ops, as it is well known and your ICP traces would also prove this, that engine longevity reduction through mixture mismanagement is far more a problem in Rich Mixtures, than in Lean Mixtures.

And before you choke on your lunch there, remember this. Rich Mixtures are ALL settings on the rich side of peak. To a scientist and engineer, they are all rich mitres. Lean Mixtures only exist on the leaner side of peak. This is a concept most people fail to understand.

A mixture that at high temps, high ICP that can cause detonation is most likely a rich mixture., Sure at very high MP's and say 10LOP you are still in the zone, but it takes very little extra leaning to get out of the zone.

These are concepts that scientists and engineers since Lindbergh have understood, pilots have not.

Anyway back to the questions, for the educational benefit of new pilots. :ok:

Backpacker

Which engine and aircraft is it you fly? There are some combinations that will be very hard indeed.

So how far once you get to peak RPM, can you get before severe roughness sets in?

I would happily help folk who perhaps do not construct their posts with comments like "So by all means go ahead, Jabawocky, and answer that one, instead of pretending to be the wiseguy without actually delivering." And take a far more healthy and polite method of questioning.

I do not have time in my life for coming on here making false claims in the attempt to educate folk, and then having stupid debates forever and a day. You can actively engage me and learn, or stay in denial. Your choice.

To respond to your last post, I have already given you as much as a post on pprune can convey. The process of teaching is not achieved by one or two posts on pprune. Do you think you could successfully teach a student to fly to solo by a few posts on pprune? No, surely not. So the same applies here. To understand the answer for some folk requires considerably more. And when some bozo goes off half educated, and gets it all wrong, who do you want to blame.

Sorry, not going to happen.

If you are suitably equipped with knowledge and understanding, plus your aircraft equipped (makes it easier), I have already given enough info. Just for your benefit, I will give you a clue, read posts #28, #33, #46 and #65. The answers are there. Let me ask you to contemplate, Lindbergh crossing the Atlantic and the Doolittle raiders. Two famous pieces of history. Neither possible without carby engines running LOP. Your very freedom today depended upon LOP Carby engines.

Now will I give you a cookbook approach to running an engine LOP that could potentially have you do it wrong? 10F LOP at a high HP is not the same as 10LOP at 8500', so a cookbook approach will never be good. You need to understand this stuff, and I can not be sure you or any other reader understands it on a thread that is ambushed by flat earth society folk all the time.

I have given you enough to go and learn properly yourself. The rest is in front of you if you wish to embark upon the journey.

Now my questions were not that complex. What would you do in that C421 with a change in MP?

Clearly this demonstrates my point. Flying schools, hangar talk, and pprune have not educated even the very well experienced and qualified folk. I do make the assumption a few of the posters here have lots of qualification and experience. That I have no doubt. But I do have doubts about a system that has allowed a great number of people get through with poor understanding of the very thing that gets them airborne in the first place.

So just for fun, have a go at the questions, you can only gain something, never lose.:ok:

It's the Robin/Alpha R2160, with a Lycoming O-320-D2A engine. I can get it probably 25-50 RPM on the lean side of best power (max RPM), before it starts running rough. But between max RPM and 25-50 RPM lean of best power the mixture knob movement is less than two mm and there is a bit of "give" in the mixture control system, so it's pretty tough to find the "best power" mixture in the first place.

As for the rest of your comments: I visit this place to learn something, or to teach others about the areas I think I know enough about to answer their questions. Not to engage in a pop quiz where the person asking the questions already knows the answer. And not to answer rhetorical questions either.

Best power will be in the EGT range of 100 to 125 deg F rich of peak. Your 25 to 50 RPM drop will still very likely leave you on the rich side of peak although probably pretty close to peak on at least one cylinder, just exactly the place you do not want to be as operating at peak generates the highest CHT's and will stress the exhaust valves and could even result in detonation developing.

Theoretically heating the induction air should improve the vaporization of the fuel and therefore make the distribution of the fuel to air mixture to each cylinder more even, as it that unevenness which causes the engine roughness preventing LOP operation in carburated engines.

In practice I have never personally had much luck trying a bit of carb heat as I leaned. When the dust settled I did not think I was able to go appreciably leaner with the carb heat then without and still have smooth engine operation. Also I found that the Micky Mouse Cessna carb heat control made it hard to accurately set stable partial carb heat settings.

Interestingly though pilots who operate Cessna 180's with Continental O 470 engines in the Canadian North, an engine notorious for poor fuel/air distribution, find that in extreme cold weather the engine quite likes a bit of carb heat at all power settings.

The bottom line from my POV is that for the ubiquitous carburated engines found in small Cessna's/Pipers/Grummans/Robins, it is pretty hard to hurt the engine with the mixture knob. If it is running smoothly its OK. The only caveat would be low altitude, slow full power climbs with the mixture leaned.

As a general rule, all of the common simple carburated engines can and should be leaned in cruise at or below 75% power at any altitude. The flight school urban myth that it is dangerous to lean below some arbitrary altitude is wrong. In addition the engine should be leaned in a full power climb at and above the altitude specified in the aircraft POH. If no data is available then leaning above 5000 feet is a conservative practice.


A much more common problem for these engines is cylinder overheating by prolonged climbs on hot days at low speeds ( ie Vy). Even at full rich mixture damagingly high CHT's can be developed due to the lack of airflow over the engine at low speeds.

Jabowacky

Just for grins I will answer you question. One day flying a 421C I did in fact notice the MP of one engine drop an inch or so. Pulling the alternate air handle fixed the problem........but I am guessing that is not the answer you wanted to hear :E

If I was really bored I would add up the word count for all of your numerous and lengthy "it is all too hard to explain on the internet" posts. Since the concepts are not exactly rocket science, I bet that the same number of words could indeed be used to craft a post with a pretty useful description of the factors involved in leaning aircraft engines........but of course to do that you would actually have to know what you are talking about, something which you have yet to provide much evidence of.

For those interested in learning more about all aspects of aircraft engine operation I highly recommend the book by Kas Thomas "Fly the Engine"

Finally as the topic of this thread is "engine checks" and the original poster was interested in the actions to be take in the event of a loss of power/rough engine, then to get back on topic and away from feeding antipodian egos's, a poorly adjusted mixture can cause a rough running engine. The most likely cause is the mixture had been leaned for cruise and then the throttle advanced, but forgetting to enrichen the mixture first. Another scenario is that at high altitudes full rich could be so rich that the engine is choking on the excess fuel and so in this case leaning the engine is required for its smooth operation.

BPF/Back Packer

The good little O-320D2A, The exact same engine (D1A) as I use LOP and it runs smooth. We are talking about at cruise altitudes of typically above 5000' or if lower, start at a MP/RPM that is around 75% and by the time you achieve LOP you are then around 65%. Fuel flow instruments are a big help. around 27LPH is the number and it sits there all day sipping away and performing book numbers doing so.

Back to science though, BPF, we are splitting hairs here a little but best power is actually at 75-80 ROP, and the power starts dropping away at 30-40 and anything noticeable probably around 30 or less, so the fact is Back Packer is probably LOP on some and peak on some doing what he says. At 65% or there about there is no problem there at all. You are quite right about not doing this at high HP down low, but that is not what we are trying to achieve.

Your comment about operating at peak EGT and the worst place because of high CHT is false. Let me tabulate this for you for future reference and for the benefit of others. The order of peaks from Rich to Lean
1. HP peaks first 75-80F ROP
2. ICP peaks about 35-40 ROP
3. CHT peaks about 35-40 ROP and it responds directly to ICP, nothing else.
4. EGT peaks at........ 0F ROP/LOP (where else :O)
5. 1/BSFC peaks last and depends on the power setting, from 20LOP at low powers to 75-90LOP at high power.

Assuming we are at cruise powers, detonation on an O320 can not exist, and even at full power on that engine the chances of doing it are pretty hard. With Conforming fuel and a conforming engine. However, running high ICP and hence high CHT for long periods and with poor cooling gives the valves a hard time not so much from direct heat, at the valve but for stress on the cylinder head itself.

The exhaust valve is at ts hottest at 25F ROP, and it is at the same temperature when at 125ROP or 50LOP so even peak EGT the valve is cooler if you are worried about that.

Now we are onto it, ;):D the process is now working. plenty more to be discovered. It is determining the right amount of heat and the throttle plate cocking that is the key.

Back Packer, in short your engine will most likely do it, you just need to do a bunch of things right. Plugs, ignition system and chase all the induction leaks out. Again an EMS and knowing what to do helps this process big time. Maybe yours will be one that is forever a pig and not able to, but in general, most can. I have better things to do than make this stuff up.

ABSOLUTELY :ok:

Any N/A engine in a Full power climb, should be leaned every couple of thousand feet, as has been described elsewhere. A Turbo or TN engine is full rich to match full MP and leaned only when appropriate, or when doing LOP climbs, but these are not that common as the time/distance/climb is only a bit of a saving and pilots like to be lazy.

Nope, that was not the answer i was looking for. Your actions were a lucky one, although I assume you had an icing problem perhaps, and nowhere in my question did I mention anything about icing or any other influential factor. Simply with no 100% certain good reason for the MP drop, what should you do? This is not a time to mess around and plenty of people have died from this, and I personally know of two cases where the pilots did the right thing, through good engine training and survived.

SHUT THE ENGINE DOWN & DIVERT

Chances are you had some minor problem, however unless you are 100% guaranteed you know exactly what the problem is you can not be sure you have not had a exhaust leak from a failed tube/joint. This will soon and it does, start burning through all manner of things until you have a fuel fed fire that you can't stop and a wing burns off. Sounds nasty hey! From the folk I know, they thought it was too and the photos prove it.

Lastly BPF..... I am not here to prove anything knowledge wise, least of all to you. When you get your fundemental facts straight, as I have corrected above for you on just what happens with EGT/CHT and the transition from Rich to Lean, then maybe you can start the "mines bigger than yours" willy wagging.

Clearly I have stumbled into your turf on this forum, where your supposed knowledge, and I am sure the majority of it is very sound and in some areas superior to mine for sure, but now that I upset the status quo you have been biting back with cheap shots like that.

Go ahead, I am happy to bug off again to my corner of the world and let the Old Wives Tales spread around some more. But for the sake of new students and private pilots/owners how about we aim to educate them sans the OWT's. :ok:

Sorry guys I could not resist feeding the jabowacky. I think it is time to put a fork into this thread, it is definitely well done.

Well, yes, it is well done Big Pistons, but it's like a horror movie, I can't look away...

If you've ever had to lift one out of the back of a truck, they're not all that little...

However, for an engine like most carb'd opposed engines, in which getting even two, much less four (or six) cylinders within 100F EGT of each other is near impossible, how could you ever manage to lean so as to be within 20 to 70 LOP?!? Which cylinder are you measuring?, what are the other's temps while you're doing that. That even precision is not possible on your average carb'd engine.

Well, maybe this has happened, though in 35 years of flying anf maintaining light aircraft, including 8 years working in an engine overhaul shop, I have never heard of anything other than exhaust gasket, flange, or baffle damage resulting from an exahust leak. That area within the cowling, by design, does not have vulnerable fuel lines close to the exhaust, and has lots of cooling air rushing around there. I'm not saying you can't have an engine fire, but I bet an exahust leak did not cause it. Perhaps Jab has had experience with these failures, and will warn off the impressionable with stories.

My O-360 powered aircraft has cowlings which make an visual inspection of the exhaust to cylinder connection difficult during a standard preflight. The first clue I had that I had an exhaust leak, (because of the nuts falling off, and that side's exhaust dropping down 3/8") was my wife telling me that when I took off it sounded different the past few times. I investigated more deeply, and sure enough saw exhaust soot where I should not. It must have been that way for some time - no fire or other damage. I just inspected it, and did it all back up again.

Like anything leaking or falling off a plane, exahust leaks are bad, and should be repaired without delay. But, I doubt that they are a cause for an inflight diversion, if suspected during a flight, with no other abnormalities in the engine. Oh, and if I'm wrong, and you do have a fire in the engine compartment, because somehow the fuel line was burned through, pull the firewall fuel shutoff, and it will self extinguish for lack of fuel.

There are many things I would be worrying about long before I worried that an exhaust leak might cause a fire.

Pilot DAR

Exhaust failures in turbocharged engines which have resulted in catastrophic in flight fires has been an issue in the past and resulted in a AD mandating continuing exhaust system inspections for all Cessna turbocharged twins.

Failure of the tail pipe is particularly bad as it points aft towards the firewall before making a 90 degree turn down right next to the firewall. Failure at the flange out of the turbo or at the bend will result in the exhaust jet impinging directly on the firewall. The Turbocharged Lances had the same system for their turbocharged Lycoming and the same vulnerability.

The Navajo has a much superior layout of the exhaust IMO. But the bottom line is these kind of failures are invariably associated with poor, or probably non existent, maintenance of the exhaust system. Exhaust leaks at the joints will also result in tell tail soot trails on the cowling or in bad cases discoloured paint on the surface of the cowling. Any discolouration or paint blistering on the cowling is a grounding snag. Still abnormal operation of any turbocharged engine should make the pilot alert for the potential for fire.

However for your average carburated non-turbocharged engine the good news is fire risk from exhaust leaks is much much less and as you pointed out there are a lot of other more likely problems you might encounter then an exhaust leak induced fire.

The even better news is I have yet to find a case of an inflight fire where the fire did not immediately go out if the engine was shut down at the first positive indication it was on fire. All the tragic accidents I have seen reported involved the pilot keep the engine running even though it was on fire

All that being said I have a fair bit of time on twin Cessna's, including C 421's and there is no way I am going to mindlessly shut down an engine just because it shows a loss of 1 inch of MP. Do a fault check, sure but immediately shut down, probably not, well that is the difference between actual operating experience and deciding that you are the expert because you took a course....