EGT/CHT vs A/F sensor for Engine Leaning

[normancanderson]

There are now available air/fuel mixture ratio sensors available to aid engine tuning in automotive applications. Aircraft still seem to rely on EGT peaking to get the same result. Since the A/F ratio sensors directly detect the lean/rich condition, isn't this a more accurate approach to engine leaning for peak performance and maximum engine life?

[WLIU]

For better or worse, in airplanes, the pilot takes the place of the engine computer that cars today have. In order to make use of the technology that you are talking about, you will have to have an engine control computer FAA certified. There are a very few single control engine management systems certified at this point, but given the poor state of the aviation industry and the low sales volume, don't expect to see lots of airplanes flying with them.

The FAA certification of electronic engine controls for the existing certified aircraft fleet is way too large a task for any of the manufacturers. In the homebuilt world you do see folks working on electronic ignition systems and between that and the electronic engine monitoring systems out there, I would not be surprised to see someone try to combine all that into a system that makes use of the parts that you mention.

Gluing new technology into airplanes is not for the faint of heart.

Best,

Wes
N78PS

[roxiedog13]

Wow, had not even thought about airfuel ratio and here I am in the middle of trying to buy a engine monitoring system for my airplane that primarily keeps tabs on the
EGT/CHT, OP OT etc. I actually installed a AF meter in my sports car about 3 years ago and it shows a digital readout and also has a circular arc of l.e.ds with red yellow
and green indicators. I will now surely put one of these in my aircraft now, probably not right away but in the near future for sure. First I have to do base line testing
then add a PowerFlow muffler and retest. Once that is done and all is stable I will install a AF meter . A good one will instantaneously give the readings as I recall and that
is a narrow or wide band device. Only problem may be the lead in AvGas, I'll check that out first. Anyway, here is an article that I just copied.....worth a look .


Theoretically, the ideal stoichiometric A/F mixture (the chemically ideal mixture of air and fuel that is required to provide a complete burn) for a properly tuned engine running on pure gasoline is 14.7:1; that is, 14.7 lbs. of air to 1 lb. of fuel. However, because of operating losses in the induction system due to intake runner and cylinder wall wetting, plus the fact that fuel may not fully vaporize in the combustion chamber, a 14.7:1 A/F mixture is often too lean for actual operating needs. A more realistic light-load, cruise A/F mixture for a stock carbureted engine running on reformulated unleaded gasoline is in the 14.1:1 range.
The A/F mixture always varies from cylinder to cylinder, therefore we tend to tune the average A/F mixture slightly on the rich side to avoid engine misfire in the leanest cylinder. It is possible to target an A/F mixture leaner than 14.7:1 for maximum fuel economy but this can lead to driveabilty problems if any one cylinder is leaner than the others. The power mixture we target for maximum horsepower is in the 12.2:1 - 13.5:1 A/F range, depending on the engine package and its combustion chamber design.

[ysifly2]

Ok... But a car is water cooled.
Isn't the reason you use EGT / CHT is to also monitor the temp to ensure you don't burn anything up... Right?

So, you are working to get to the best lean without causing engine damage.

If you did it purely by air / fuel mixture, wouldn't there be a potential of excess heat ?

[steveinindy]

If you did it purely by air / fuel mixture, wouldn't there be a potential of excess heat ?


Isn't the reason you use EGT / CHT is to also monitor the temp to ensure you don't burn anything up... Right?

I'm not an "engine guy" but that's the way it has always been explained to me. Personally, there's a reason why I like FADEC systems so damn much. To me at least, the cost is justified by the reduction in workload in the cockpit and the headache in the build phase (as compared to trying to put a non-standard electronic system on an engine).

[normancanderson]

I have to go along with roxiedog13 - these in cockpit AF meters should help monitor one of the critical engine parameters. I don't think they will replace any of the others (EGT, CHT, etc.) but I have to believe they provide a more accurate and instantaneous view of the A/F ratio. The pilot is still responsible for setting mixture correctly (unless you want to add FADEC), but it just seems more accurate than the ole ' lean of peak/rich of peak' guessing game.

[WLIU]

The discussion above is based on the incorrect assumption that you always want to run the engine at the "ideal" fuel air ratio. For an air cooled aircraft engine, that assumption is not correct.

Aircraft engines work harder than auto engines and as alluded to above, they have different issues. Water cooled engines are heavier, but cool the cylinder heads more efficiently. For air cooled engines, heat removal is a problem. So we run aircraft engines watching temps. If you have a turbo for instance, too high and exhaust gas temp will create the need for an expensive replacement.

The paragraphs above are preparation for explaining that fuel is used to cool the engine. On takeoff, we run excess fuel for cooling. Even in cruise, you may have seen Mr Busch write huge amounts of material about running leap of peak EGT. That is efficient and it creates less heat. Running rich of peak is less efficient but also keeps CHT's OK. You will find no one advocating running at peak EGT, which is a product of the "best" fuel air ratio.

The problem that engine controller designers have is trying to read the mind of the operator. The engine operator who stays in the traffic pattern doing touch and goes is a different operating profile than the guy to takes off, cruises 3 hours as 12,000' and then lands, which is different than the guy who takes off, spends 40 mins at high power pulling positive and negative G's. I would like to be a fly on the wall of the guy who takes an engine controller to the FAA that includes artificial intelligence.

So the problem has complexities in multiple dimensions. A mixture meter is not a one size fits all solution and it is redundant to the gauges that we already have. If it floats your boat then put one on your panel, but if you fly a lot, and you do not simply fly the same hour 1000 times, you will likely find its utility limited.

But building a smart FADEC is a challenge worth attacking. Which one of you has the time and $$ to glue together a EI or JPI unit to something like an Airflow Performance fuel control, an E-Mag, and a computer to make that real for experimental aircraft?

Best of luck,

Wes
N78PS

[steveinindy]

But building a smart FADEC is a challenge worth attacking. Which one of you has the time and $$ to glue together a EI or JPI unit to something like an Airflow Performance fuel control, an E-Mag, and a computer to make that real for experimental aircraft?

I hate to put this argument out there but why would you (unless you're just trying to save money) want to "reinvent the wheel" when systems already exist for many certified engines? Maybe it's just my unwillingness to screw with the firewall forward aspects anymore than "Fuel line A to connection B...." but it just seems to be kind of more of a headache and potential risk than the benefit most of us would get out of it. The breadth of engines that people use also makes it difficult to extrapolate from one to another so at best you're looking at something that might be useful to a small slice of the experimental fleet and at worst you're looking at something that can wreak havoc on the engine of your own aircraft if you aren't very careful.

The simplest choice is if you want the top of the line so far as fuel mixture et cetera goes, you pay for it and get yourself a certified engine with a proven FADEC or something along those lines.

[WLIU]

I'll bite. Have I been asleep? Have I missed a FADEC system for a Continental O-200? Who makes it? Continental does not.

Thanks,

Wes
N78PS

[steveinindy]

I'll bite. Have I been asleep? Have I missed a FADEC system for a Continental O-200? Who makes it? Continental does not.

Did I specify that one? I simply said that they are out there for many of the engines we use.

Honestly, if you're only running a hundred horsepower, why would you need anything but the standard ignition and fuel control system? Adding complexity to one of the most basic pieces of aircraft propulsion gear you'll come across just seems like asking for more trouble than it's worth. I mean, that's a lot of work to replace the carburetor with an injection system and figure out all the other stuff that goes along with the exchange from a traditional fuel metering system. It's worked well (outside of carb icing issues and people not maintaining them properly) for sixty-five years and honestly there aren't many airplanes running the O-200 series that exactly have a high workload given how slowly they fly (the Cassutts notwithstanding but they are more of an anomaly than anything else). If something works well, why screw with it when the alternative is not likely to produce a vast improvement in reliability, safety or efficiency? So far as I am concerned, unless you're doing something beyond doing pattern work or doing $100 hamburger runs there exists no real need for a FADEC or anything more complicated than the standard "throttle/mixture/pitch" controls. Some may want it and think it is worth the effort but we need to be careful in chasing such desires that we do not inadvertently cause more problems than we solve.

Remember Wes, not all of us are as skilled with engines or the underlying science as you appear to be. In fact, most of us probably have little business doing extreme modifications because of a lack of experience with anything beyond the most basic of maintenance. That coupled with a poor assessment of one's abilities- something many of us are guilty of when it comes to actually turning an idea into a reality- is one of the biggest problems that homebuilding faces.

We don't want to unnecessarily quash constructive experimentation but at the same time we have a duty to our fellow pilots and homebuilders to keep them from doing anything too outlandish or risky. It is a very blurry line sometimes, especially when you get into the more long-held dreams of homebuilding. The best example of this is the repeated discussion and attempts to produce an economically viable "flying car". Given that we're a group prone towards looking at the "let's make it fly!" side of the issue, we don't like to be reminded that the biggest hurdles are not the technical ones of making something that you can drive down the road and fly (hell, Taylor proved this was possible decades ago). The thing that is going to kill any flying car project is the need to comply not only with the FAA certification standards but with the federal and international regulations on car safety. Couple that with the cost of a "flying car", the widespread fear of flying, the NIMBY a**holes and the fact that not everyone can be trained to be a pilot in a safe and efficacious manner....there goes that dream. But yet, we have the dreamers who keep on...economic viability isn't everything when you've got a mission in mind sometimes.

[normancanderson]

So here is an excellent example of a simple question getting completely off topic - The intent of the original query was to determine if the modern A/F ratio meters provided any benefit for use in aviation applications. There was never any intent to imply that developing an automated mixture control system was viable for most homebuilders.
WLIU makes a good point about air cooled engines not running at stoichiometric (14.7:1) ratios. But the ironic thing is that I found most of the useful discussion on the application of the A/F ratio meter on the aircooled VW racing engine forums. They agree - the 'best' ratio for engine performance AND lifespan is around 12:1 (a.k.a. - 'rich of peak'); racers have never generally been bothered about fuel economy. I was hoping to get some useful feedback on the relative merits of using only EGT for mixture control vs direct A/F monitoring or a combination of the two. It seems this simple question has hit a sensitive point for many contributing to this forum - but that off-topic discussion has served to distract from the original intent.

[JCosh]

I currently have about seventy hours on my GlaStar since converting it to EFI via a kit sold by Flyefii.com I have a Lyco 360 in normal cruise CHTs are 300-350, EGTs are 1200-1250 and the AF is approx 13.5 -1. I like the EFI since I previosly flew behind a Subaru, and was not interested in going back to changing the mixture for altitude/temperature changes. Also wanted an engine that would restart instantly after a hot shutdown, which I'm sure you know is not the forte of an IO 360. Just my two cents.
Juliette

[normancanderson]

To expand on JCosh comments - there has existed EFI for aircooled automotive engines for over two decades - with no burned pistons, scoured cylinder walls, warped heads, etc.. Since my application (a modified version of an aircooled VW engine) currently uses only non-mixture controllable carburetors, it just seems like either a mixture controllable carb (or better yet, EFI), supported by an A/F mixture sensor would provide much more accurate control over the engine than just EGT peaking. Faster response times, too. I can see the value of also having EGT and CHT to make sure that the mixture setting isn't doing any harm, but those sensors then become more like oil temp or fuel pressure - something to warn the operator of problems, not something you use to prevent them. Or am I missing something?

[Mike M]

So here is an excellent example of a simple question getting completely off topic - The intent of the original query was to determine if the modern A/F ratio meters provided any benefit for use in aviation applications. There was never any intent to imply that developing an automated mixture control system was viable for most homebuilders....that off-topic discussion has served to distract from the original intent.

KA-CHING!!

i installed a Bosch O2 sensor for an '86 Buick (it was economical) running a simple bar graph indicator to show relative mixture settings on my O320 Lyc-powered homebuilt. "calibrated" it by leaning to the setting i wanted to hold and noting the reading. from then on, i could quick-set the mixture to the same point reliably and repeatably as long as i used unleaded fuel. then i burned a few tanks of leaded fuel. that changed the sensitivity gradually until it quit showing the actual ratio. so. if you want to use an A/F ratio meter, i recommend you find one that does not use an automotive O2 sensor from an '86 Buick to sense the ratio if you plan to use leaded fuel.

your mileage may vary.

[Mike M]

In order to make use of the technology that you are talking about, you will have to have an engine control computer FAA certified.

not for an experimental aircraft.

[steveinindy]

there has existed EFI for aircooled automotive engines for over two decades

The question I have in response to that is how hard is it to "tune" an EFI to a particular engine? Wouldn't it require extensive tweaking which would provide a higher risk for engine damage than simply going with the tried and true methods that are used to establish the TBO intervals anyhow?


I can see the value of also having EGT and CHT to make sure that the mixture setting isn't doing any harm,

So are you suggesting that we have a redundant system to allow the pilot to override the EFI if they settings are doing harm? Because unless that is done, you have three choice: land ASAP, risk engine failure or shut the engine down. The latter is obviously not a good choice in anything but the most extreme situations. Option 1 isn't always available unless we're willing to chance a forced landing or never leave the traffic pattern.


but those sensors then become more like oil temp or fuel pressure - something to warn the operator of problems, not something you use to prevent them. Or am I missing something?

Paying attention to them is how you prevent a problem. I'm probably one of the biggest advocates for EFI and FADEC but I also think we have to be cautious before getting in a rush to try to assign a more complicated solution to the problem of engine failure. The problem/question isn't can EFI or FADEC be safely applied to aircraft engines (because the answer is yes) but rather can we safely do it as a post-production add-on to the multitude of engines (aircraft and otherwise) that power experimental aircraft? The technology is there but at the same time we have to remember that not all of us are mechanically or electronically astute as we probably should be for such a task. I say this because I happen to be one of those people when it comes to anything firewall forward other than fire suppression. There's a very good reason why I'm going with something off the shelf for the powerplant and recognizing my own limits- which a lot of other homebuilders likely share- is the best way to keep myself and my passengers out of trouble.

In other words, Michael Crichton got it right in The Lost World when he was talking about the character Dr. Thorne (a Stanford engineering professor) who liked to point out to his students that to engineer you have to understand psychology because while your calculations and everything may be perfect, as soon as you put those plans into the hands of others, they will screw it up all too often. It's not something we like to think about or admit but if we want to grow as a community and as individuals, we must have this sort of introspection inherent in everything we do.

[normancanderson]

cdrmuetzel makes a good point about 'poisoning' the O2 sensor. This is also a concern for the automotive racing community, since they tend to use leaded fuels for high octane applications (like drag racing). Here is a quote from one of those forums "I use the innovate LM-1 with the Bosch sensor and we raced with it for 5 years, on VP C14 fuel (114 octane, leaded) , never had it alter its AFR reading. Engine is tuned well with tan on plugs and it runs at 12.8. Always powered it up, and I replaced it after 5 years for something to do, not because it was necessary, and the new sensor just read the same AFR as the old one, so the old one went into the box as a spare. So it is possible to obtain the time I said. And what I said about the 50 the 100 hours is what Bosch specify." So maybe the Buick sensor was more susceptable to contamination, or the engine was running too rich for that sensor. Definitely something to be addressed in such an application.

In response to steveinindy's comments - Q1- O2 sensors generate a voltage that is used by the EFI controller to regulate the A/F mixture. This voltage can be adjusted to provide control over the actual ratio (essentially tricking the EFI controller into giving the operator the ratio desired). Q2- The concept, whether using EFI or a carburetor, would be to provide mixture control to the pilot to get the desired engine conditions, just like mixture control and EGT are used today. Q3 - I think a lot of folks on this thread are over-thinking the question - O2 sensing can be used with a mixture control system of any kind to more accurately set the A/F ratio than using EGT. No fancy EFI or FADEC is required. This is just another sensor to help with engine management, and the original question was whether or not anyone had tried it. It sounds like a few have , with varied results. The biggest issue having been the leaded fuel potentially altering the readings.

Thank you everyone for your inputs, I think I have a grasp of the potential issues to be addressed. Finally, I have to admit that I'm truly amazed that, on a forum like this, there would be comments saying things like 'don't try something new, because others might try also it and screw things up'. To me, trying something new is what the spirit of the EAA is all about. Otherwise, this would just be the Cessna maintenance forum. Granted, you need to do your homework, and do your the best to mitigate risks. Can you imagine what life would be like if the Wright brothers heeded such advice?

[Mike M]

...comments saying things like 'don't try something new, because others might try also it and screw things up'.

if what i said sounded like that, it's not what i meant. what i was trying to say was, "don't duplicate a system i used without knowing its shortcomings." i've noted that when somebody asks a simple question on this forum, folks with no actual hands-on experience in that particular area will toss a wet blanket on the whole idea. some of us just ignore them. i'll check out that other sensor, thanks.

[steveinindy]

Finally, I have to admit that I'm truly amazed that, on a forum like this, there would be comments saying things like 'don't try something new, because others might try also it and screw things up'.

The problem is that you have to remember that not all EAA members have the requisite brain power and/or experience to go experimenting. A lack of one or both of those- especially in concert without either the restraining influence of the community or the common sense to know when you're in over your head- is a potentially lethal issue when someone starts getting away from strictly following a set of well-tested plans or a kit.

If you think I'm being hyperbolic, I have two words for you: Daniel Lloyd.

The "experimental" moniker for the majority of us is and probably should remain more a reflection the certification category of our aircraft more than an implicit encouragement to try new and untested concepts especially given how many of us plan to haul our family and friends around in our creations. Given that a lot of folks in the experimental community seem to treat the "test flight" period as more of a "get it over with" hurdle rather than a true testing and learning experience once they realize that the aircraft is off the ground and has something that passes for control, I can't in good faith argue that we need to be pushing those same folks to try new things without a lot more support and oversight than we can currently offer. It's better to be sitting around dreaming about possible improvements that are beyond our personal abilities than for our friends to be standing around a freshly closed grave questioning "what the hell was he thinking?".


o me, trying something new is what the spirit of the EAA is all about.

I would tend to agree with the above caveats.



Granted, you need to do your homework, and do your the best to mitigate risks.

Here's my thoughts on that:
1. Most pilots, unless they do test flying or aerobatic flying for a living, tend to kind of ruin their pants and freeze when they either encounter a stall or a sudden engine failure.
2. Most pilots' stick and rudder skills (my own included) leave much to be desired especially when it comes to low speed flight.

How do you suppose we mitigate these risks in the few pilots/builders who are confident enough in themselves to go forward with a serious engine modification? The issue is that people who become pilots tend to be more self-confident in their own abilities than your average person. We tend to be very poor judges of our own abilities and tend to rate ourselves superior to our peers at a rate greater than the general population. Those of us who decide to build seem (I say "seem" purposefully sense I've never seen any psychological cohort study of builders vs. non-builders and am going solely upon my own admittedly anecdotal evidence) to be more self-confident than the rest of the pilot community because of the determination it takes to spend years putting together a craft to bear us into the world of flight.

The problem is that- as a general rule- the more self-confident a person gets, the more driven they are towards a particular goal, the more at risk they are for "tunnel vision" or a selection bias towards those things that will lead them to that goal. It's the same underlying issue with "get-home-itis", scud running and all the other incredibly questionable pilot behaviors we see time and again in NTSB reports. It's also why, while the credit usually goes to one person (such as a Burt Rutan, a Ed Heidemann, a Kelly Johnson to name a few), almost to the point of statistically absurdity, they all had a team around them to keep them grounded or to otherwise provide feedback. Great ideas seldom- contrary to the way it's oft portrayed- spring from a lone genius who is working against all his detractors. Hell, sometimes the person who gets the credit didn't have anything really to do with the practical application of the idea (Alexander Fleming and penicillin anyone?)

Some of the best advice I was ever given came when a professor of mine invited me to lunch with a friend of his who was in town to visit. We get there and I realize that I'm about to have lunch with James Watson- as in one of the guys who figured out the double helix structure of DNA- and I found myself able to ask him what the best advice he had for a young researcher was. It came in the form of two points (paraphrasing here since I was too awestruck to think to write the actual words down):
1. Never be the smartest person in a room. If you think you are, you won't try as hard.
2. You will always learn more from those who disagree with you than those who will tell you that you have it all figured out. Anyone on your team who can't give you at least one reason the current idea won't work should be considered for termination because they are not obviously not giving it their full attention.


Can you imagine what life would be like if the Wright brothers heeded such advice?

I really hate that sort of logic because they are generally strawman arguments. There's a pretty big difference between the exceedingly cautious way the Wrights approached their testing (which explains to a far greater degree their success and survival than a simply pig-headed "you can't stop me" attitude) and development and the often "throw stuff at the wall until something sticks and assume that's the best solution" approach that a more than a few homebuilders currently use. As I said before, the best advice often comes from those with whom you disagree.

[Frank Giger]

My thoughts:

If one is knowledgeable enough about what an additional gauge actually means and can use it in a useful manner, I can't see how it would hurt - though I do wonder if the effort here is going to measureably improve performance or longevity of engine life. I'm the guy Steve is referring to when speaking about guys that don't need another gauge and wouldn't be able to interprete its data properly.

:D

Secondly, the statement that pilots and homebuilders "tend to rate ourselves superior to our peers at a rate greater than the general population" is just plain silly as it a defining characteristic of our nature as aviators - because it's true!

;)

[steveinindy]

Secondly, the statement that pilots and homebuilders "tend to rate ourselves superior to our peers at a rate greater than the general population" is just plain silly as it a defining characteristic of our nature as aviators - because it's true!

You know what's bad is I almost included the phrase "case in point: Frank Giger" in that but decided to let you chime in and point that out on your own. ;)

[Mike M]

i previously posted, "i've noted that when somebody asks a simple question on this forum, folks with no actual hands-on experience in that particular area will toss a wet blanket on the whole idea. some of us just ignore them."

i should have taken my own advice. so i deleted a post i'd meant to be humorous because it was misinterpreted. i promise to someday stop trying to teach pigs to sing. sorry for wasting bandwidth.

[steveinindy]

pilots are like gunfighters. if you don't think you're the best in the business, get out of the business. no brag, just fact.

And the mortality rate for gunfighters is something you want to see repeated in flying? No sarcasm intended but that's an attitude that just makes me cringe.

It would be fine if we were all able to train to a high degree and maintain sufficient hours to be Bob Hoover level stick and rudder pilots. Here's the problem: most of us are lucky to clock 100-200 hours of flight time a year for various reasons (family, work, money, etc). That's barely enough to maintain legal proficiency in a lot of cases. By the very definition of "the business", not everyone can be the "best". You find a lot of people in the middle (good but not stellar) and a few that amaze (Bob Hoover, Patty Wagstaff, Sully, Skiles, Denny Fitch, Al Haynes, Bill Records, that guy with the Beech 18, et al) and a few that just appall you with their lack of basic flying ability (Marvin Renslow, Rebecca Shaw, the crew of Air France 447, et al).

Thinking you're the 'best' when you aren't and especially when you're not and you don't have a lot of recent experience is asking for yourself to get in over your head (to paraphrase Top Gun since you opened the door to marginal analogies) because your ego is writing checks that your flying ability can't cash. That old saw about the dearth of "old bold pilots" is around for a reason.

No offense, but that sort of attitude is, in part, exactly what earned HEMS it's miserable safety record which is one reason why I've buried so many of my aeromedical colleagues. Pilots getting in over their heads because they thought they could outfly whatever they encountered. Let's encourage each other to identify our respective strengths and weaknesses and work on them instead of the "come home with your shield or on it" attitude that led the military to start encouraging pilots to read Tony Kern's book "Darker Shades of Blue" to bring attention to the risks inherent among even the most proficient, experienced, current and well-trained flight crews in the world.

You shouldn't fly like you're afraid but you should know your limits and abide by them while working to address them safely. Many years ago, I heard Bob Hoover give a talk and his comment to a young military pilot who had asked a question about what it takes to be a good test pilot was to the effect of "Being a good pilot is about being lucky, skilled and smart. Success from luck and skill are the product of being smart about when you have to use luck because you've gotten past the limit of your skills." Coming from someone that is probably most people's first choice for the best stick and rudder pilot currently living (if not of all time; not to mention the most humble test pilot ever), I'd say that's a good approach to take on the matter.

[Frank Giger]

Aw, Steve, hardly nobody can touch-and-go on a CAVU morning with 3 mile an hour winds down the runway like I can. I know this based on the number of pilots who will step outside to watch me and make all sorts of gestures with their arms with smiles so big I can see as I go around.

On a gusty crosswind day the A&P joins them. I know I'm the best because he hardly looks at the new car brochures and the Aircraft Spruce catalog he usually brings with him for some reason.

I am a living legend, for I have ground looped a trike (no wing strike, thankfully) - how many pilots do you know that can make that claim?

;)

[Mike M]

deleted by author

[steveinindy]

ABSOLUTELY! Ronnie Howard, John Wayne, Richard Boone, Hugh O'Brian, etc in "the Shootist". one obviously "better" and more experienced than the others. consider how it ended.

I've never seen it. Good movie?


you've hijacked a post and gone off into your own little world. how might available air/fuel mixture ratio sensors be helpful for a more accurate approach to engine leaning?


if you can't contribute ON THE TOPIC, well.....why post?

If you notice, I ended up asking a lot of questions about what it would take to apply this to an engine since I am not an engine expert by any stretch of the imagination. The reason I voiced concern is that I know a lot more folks who are like myself when it comes to certain aspects of the design (such as engines) than the folks who can figure out how to do this.


o far all you've contributed is how stupid, egotistic, and unsafe the rest of us

I tend to fall into that group myself since I'm a middle of the road pilot when it comes to skills and currency. That's why I speak about things the way I do. We have to keep all of our fellow pilots- good, bad and mediocre- safe and we do that by trying to keep people from overstepping their bounds.

I never said anything about assessments of pilot psychology that is not backed up by even a cursory review of the research on the subject so far as self-confidence and rating of one's abilities is


knows you're a legend in your own mind.
Not even close. I'm probably my own worst critic. I'm a mediocre stick and rudder pilot because of the fact that I don't fly enough to improve my skills. Once you get me outside of the human factors and crash survivability aspects of aviation, I'm learning just like the rest of you.


but do you have any actual experience with A/F ratio meters?

Nope which is why I've previously stated:

The technology is there but at the same time we have to remember that not all of us are mechanically or electronically astute as we probably should be for such a task. I say this because I happen to be one of those people when it comes to anything firewall forward other than fire suppression. There's a very good reason why I'm going with something off the shelf for the powerplant and recognizing my own limits- which a lot of other homebuilders likely share- is the best way to keep myself and my passengers out of trouble.

I'm one of those people who you think I look down my nose at. I have zero business trying to muck with an engine which is why I asked so many questions about what does it take to do this or that with regards to electronic fuel control and ignition. Oddly enough, those questions never were answered which leaves those of us trying to


God's gift to aviation safety, design, construction, operations, oh almost anything.

That's your snide assessment of me, not mine. I'm a researcher first and foremost and I only state what the evidence I have indicates so far as safety is concerned. When it comes to crash survivability ("construction"), the information I put forth is simply based on the research myself and my colleagues have conducted (which is able to pass peer review for publication so apparently I'm not too far off the mark) or the various established standards (especially the US Army's crashworthiness standards for helicopters and light aircraft). So if you think I don't know what I'm talking about then apparently the folks who wrote those regulations and standards also didn't know what they are talking about either. You know more about me when it comes to flying helicopters (because I've never flown a helicopter before) and you're not an aviation safety researcher for a living so we each have our respective areas of knowledge. I'm don't even consider myself an expert on the subject so thinking I am "G-d's gift" with regards to something isn't even close to correct.

As for design, I'm still learning. Ask Ron Blum....I talk to him all the time about aerodynamics, etc because whenever I run into aspects of things with which I have no experience, I go find someone with the education or knowledge to learn from.

The rest of this discussion can take place via PM to avoid a further derail. I would still appreciate some information on what it takes to apply these systems to a new engine, etc. Those questions I posed still remain unanswered and I am looking to learn in this case.

[58boner]

If I might be so bold as to interrupt this misguided side tour of the original post I would like to insert my .02 on the subject of fuel/air mixtures as they pertain to air cooled aircraft propulsion systems (piston type).

I use EGT to control mixture at given power settings, and CHT to monitor engine cooling. Using both is a requirement when operating with cowl flaps and a constant speed prop.

I was never a big fan of engine monitors until I bought a plane with a plane with a EDM-730. Great device with enormous potential. I find it is my most used instrument preflight including run-up. It will give you advance warning of a leaking exhaust valve, fouled plug, give shock cooling warnings or tell you when you forgot to open the cowl flaps.

When you start using an engine monitor you will automatically be drawn to your engine operations manual to learn all about those power setting charts and ROP versus LOP arguments and you will get to see the results of the different settings when you fly. It's fun to be a test pilot sometimes!

Last but not least FADEC ain't all it's cracked up to be. Sometimes its better to control your own destiny, sure Sully is a hero for landing in the Hudson, but if he'd been flying an old Pratt he would have landed with dry feet.

[steveinindy]

sure Sully is a hero for landing in the Hudson, but if he'd been flying an old Pratt he would have landed with dry feet.


At the risk of getting branded a smartass for asking this, but might I ask why you say that? I'm not an engine guy and honestly wouldn't know a P&W from a CFM from a Rolls-Royce turbofan if you put all three of them in front of me. Is there something special about the P&W that makes them able to ingest several very large birds and still keep providing thrust and not simple catastrophically fail? I'm obviously missing something here because I don't see what FADEC has to do with an engine's operation once it's major components have been massively damaged.


When you start using an engine monitor you will automatically be drawn to your engine operations manual to learn all about those power setting charts and ROP versus LOP arguments and you will get to see the results of the different settings when you fly. It's fun to be a test pilot sometimes!

Do you have any other advice for those of us looking to eventually use engine monitors in our designs?

[58boner]

Yes, the old fashioned turbines could be run to the point of melting the innards out of them. As long as you poured in fuel they would make thrust to the point of destruction. I have seen many examples where severely damaged old JT-8D engines saved their crews at the sacrifice of everything in the core of the engine. These events never make the headlines because there is no dramatic event to alert the media.

The Fadec on the modern engines will shut them down when operational parameters signal an "Exceedence". It's a self preservation programing thing, personally I would rather be in charge. If I need to melt the innards out of an engine to reach safety I want the option. I'd rather not be at the mercy of some box.

[steveinindy]

As long as you poured in fuel they would make thrust to the point of destruction.

One of bits of information I had passed along to me about the old turbines (specifically the JT-3s as most of what I have learned came from a former 707 captain I met) was that they tended to run and run and run with damage but at the same time if you sucked a large bird into them (the example used was a turkey vulture because that's what the pilot had experienced personally) they would "go to pieces". The way he described it was that if you had some sort of internal engine failure or even took out a flock of starlings or doves that caused the engine to puke, you were good but if they main fan disk was damaged massively, you were looking at shedding large chunks of the engine.

Was I misinformed?


These events never make the headlines because there is no dramatic event to alert the media.

Eh....I tend to ignore most of what the media says and rely on things that come from the various investigatory bodies.

If I need to melt the innards out of an engine to reach safety I want the option. I'd rather not be at the mercy of some box.

Point taken. I would tend to agree.

[58boner]

I have seen them shed flaming chunks all the way to touchdown. I've seen a JT-8 whose turbine blades were burned down to nubs and it was still making power and spewing molten metal out the tailpipe. There is a distinction between blade damage and disc damage. Disc damage is a game stopper.

My previous employer operated over 700 of these engines in scheduled service and I had the privileged of access to the lot where they parked the incoming cores for overhaul. I wish I had taken some pictures.

[steveinindy]

There is a distinction between blade damage and disc damage. Disc damage is a game stopper.

OK, this is going to sound really boneheaded but isn't the disc made up of the blades? I have a basic idea of how a turbine engine works but apparently my terminology is a bit muddled when it comes to "name that part" since I'm not a mechanic.

[58boner]

In general terms the disc is the hub or center part the blades mount to. The blades are separate from the disc and can be replaced when they wear out this way you don't have to replace the disc when you have one little nick in a blade.
The disc can fail separate of the blades usually with catastrophic results ie the Sioux city crash of the DC-10.

[steveinindy]

Ah.....OK. That makes sense and I kind of figured that was the difference but at the same time didn't want to just make the assumption. Thank you for clarifying that.

[weiskopf20@gmail.com]

I was a maintenance troubleshooter in a Vigi (RA-5C) squadron on the Big E during Viet Nam. The pilot of the F-4J spotted next to us gave his Plane Captain a BIG thumbs up when asked if the A/C was up.

We were all amazed as we could see some daylight through the STBD engine. God bless the GE J79-10. The pilot did fess up that temps might have spiked up just a bit - but only for an instant!

Any jet engine will FOD - some try their best to get you home.

Pete

(One of the Maintenance Chiefs on the Nalls Sea Harrier)