Leaning in the Climb

[Ironflight]

OK, let me set one rule - this is NOT an LOP thread - OK? You can start your own thread to argue that topic, if you are tired of the old ones....

This is about leaning in the climb...

Most of us probably learned to fly in simple planes with minimal engine instrumentation. Since there were no EGT's or CHT's, we were taught some basic rules of thumb:

1) in cruise, below 75%, lean to roughness, then enrichen until smooth.
2) Don't lean at full power (greater than 75%) below 5,000 - above that altitude, lean until smooth.

These rules were no doubt designed to protect the engine from folks who had no instrumentation, and therefore no better insight into engine operation.

Now let me ask a question about the second rule, and hopefully some knowledgeable engine guys (Mahlon?),will chime in. What exactly, does this rule protect? Is it keeping cylinder head temperatures below limits? Is it to keep EGT's reasonable? To stop from overheating valves? Prevent detonation?

The reason that I ask is that many of us are now flying heavily instrumented aircraft with real-time graphs and alarms for many of the parameters. Given this additional insight, is it, for instance, OK to lean, as long as we keep the temps in limits? 5,000' and 70% power seem like very arbitrary numbers (kind of like the mystery of running "square" or "oversquare" - both of which are really accidents of the units being used...), yet I find myself still sticking to them - even though the engine seems very happy in climb when I do break the rules.

Anyone want to take the first swing at this topic? I am truly curious, as an engineer, if we can manage the systems differently with better instruments!

Paul

 

[Yukon]

Detonation

OK, let me set one rule - this is NOT an LOP thread - OK? You can start your own thread to argue that topic, if you are tired of the old ones....

This is about leaning in the climb...

Most of us probably learned to fly in simple planes with minimal engine instrumentation. Since there were no EGT's or CHT's, we were taught some basic rules of thumb:

1) in cruise, below 75%, lean to roughness, then enrichen until smooth.
2) Don't lean at full power (greater than 75%) below 5,000 - above that altitude, lean until smooth.

These rules were no doubt designed to protect the engine from folks who had no instrumentation, and therefore no better insight into engine operation.

Now let me ask a question about the second rule, and hopefully some knowledgeable engine guys (Mahlon?),will chime in. What exactly, does this rule protect? Is it keeping cylinder head temperatures below limits? Is it to keep EGT's reasonable? To stop from overheating valves? Prevent detonation?

The reason that I ask is that many of us are now flying heavily instrumented aircraft with real-time graphs and alarms for many of the parameters. Given this additional insight, is it, for instance, OK to lean, as long as we keep the temps in limits? 5,000' and 70% power seem like very arbitrary numbers (kind of like the mystery of running "square" or "oversquare" - both of which are really accidents of the units being used...), yet I find myself still sticking to them - even though the engine seems very happy in climb when I do break the rules.

Anyone want to take the first swing at this topic? I am truly curious, as an engineer, if we can manage the systems differently with better instruments!

Paul

Gosh, Paul, with all those caveats, I hesitate to reply, but I'm certain even
Mahlon will agree.........excess fuel at high power settings provides a buffer against detonation.

 

[L.Adamson]

2) Don't lean at full power (greater than 75%) below 5,000 - above that altitude, lean until smooth.

Out here in the mountain west at 4600' msl, we'll assume you're going to lean the engine, everytime, before the takeoff roll.

If you don't, you'll loose a good percentage of takeoff power before ever leaving the ground. This has also been cited as contributing cause in numerous departure accidents around here.

Those from "sea-level" cities along the U.S. coast and places such as U.K., seldom seem to believe, will once and a while argue, but it's a fact! -LEAN BEFORE TAKEOFF-

P.S. --- there is one guy around here, who claims he needs full rich in his factory airplane; but we know he has screwed up cables!

 

[flyeyes]

OK, let me set one rule - this is NOT an LOP thread - OK? You can start your own thread to argue that topic, if you are tired of the old ones....

This is about leaning in the climb...

<snip>
Given this additional insight, is it, for instance, OK to lean, as long as we keep the temps in limits? 5,000' and 70% power seem like very arbitrary numbers <snip>
I am truly curious, as an engineer, if we can manage the systems differently with better instruments!

Paul

Hi Paul.

I'm not an engineer, but unless my understanding of this is deeply flawed, this one is pretty simple.

First, you have to make sure your engine is set up properly (many aren't). This means that each cylinder, at sea level and full power under standard conditions, is at least 200 degrees rich of peak EGT. This is very important, and if your engine isn't set up this way, fix it. A little too rich at WOT is OK, a little too lean isn't, even if it's only one cylinder. You can figure this out in a single flight by noting the EGTs just after takeoff, and finding peak EGT after the power is below 75%. Do it more than once to check your numbers.

One you have established that you are rich enough, the takeoff EGT at sea level is your target EGT in the climb. In other words, as you climb (without changing the mixture) the EGTs will gradually fall as the MP drops. It is OK to lean to maintain the EGT you had at takeoff, as long as it's 200 below peak.

In the past couple of weeks, I have made high density-altitude takeoffs (leaving GCN and AEG) and it is very helpful to know, on the takeoff roll, what target EGT to lean to for max performance.

As an example, the first cylinder to peak in my RV-8 peaks consistently (with both ignitions firing) at about 1320 indicated EGT. In the climb, I just ensure that it remains at or below 1100 or so. I probably tweak the mixture every 1000-1500 feet.

I'm sure Walter or somebody with a deeper understanding of this will jump in, but this seems to be working well for me.

James Freeman

 

[n468ac]

We lean as follows - assumes going to 6000' or higher and climbing at 135 to 140 kts...

Start leaning once you get to pattern alt. - we can pull the mixure a 1/2" out before the EGT shows any changes.

Lean to EGT is 1390 on the hotest cyn
Lean during the climb to keep the hotest EGT to 1390
Once at flight alt lean to 50 ROP

 

[AlexPeterson]

My method is to keep full rpm/throttle until about at 1000 agl. I then pull the MAP to about 23 or so, and the rpm to 2400 (usually brings the MAP up to about 24). I then pull the mixture from full rich to around 8 gph, which is lean of peak. I watch the CHT's fairly closely, and lower the nose (from normal climb of 120 kt) if any cylinder thinks about going over 400. If cylinder temps don't behave, I'll put full rich back in (about 11 or 12 gph), and that will promptly cool things down significantly. Power will be less, of course.

Deakin recommends keeping the mixture full rich on the way up to keep things cool, but he also writes that it is generally ok to lean below 75% power, given one stays out of the "red zone" between, I think, 100F ROP and 50F LOP.

What say you, Mr. Atkinson?

 

[dan]

I lean as aggressively as possible while still keeping CHTs stable. My mixture control is my CHT control. If I see CHTs dropping, I lean further. If I see CHTs rising, I enrich. This "policy" assumes constant airspeed in the climb and ROP.

This is with fuel injection. YMMV.

 

[fodrv7]

'Normal' EGT Display Mode

Morning Paul and all,
For you and others who have GRT engine monitor (or similar) if you accept the Deakin advice to lean on the climb to manitain Take-off EGT, then shortly after TO select 'NORMAL' on the Engine Monitor. As you climb the engine monitor will display degrees Rich from the Take-off EGT and you can simply lean back until the difference is zero.
This method, which came to me one night at 3am (sorry 0300hr), has two advantages.
1/. You don't have to memorise the T/O EGT.
2/. Instead of using an arbitary figure of say 1400 degrees, you are using the figure for the conditions of the day.

Pete.
PS. By the way, here is a page from the Lycoming maual that graphically displays what happens to Mixture and fuel flow when you lean below about 80%.
P.

 

[penguin]

Deakin recommends keeping the mixture full rich on the way up to keep things cool, ...

Pelican's Perch #64 is the relevant reading material here, http://www.avweb.com/news/columns/182176-1.html. Although this is written for a Continental fuel injected engine, the principle is the same. Deakin advocates maintaining the EGT you had at (about) 1000' using the mixture control.
Pete

 

[n468ac]

Morning Paul and all,
For you and others who have GRT engine monitor (or similar) if you accept the Deakin advice to lean on the climb to manitain Take-off EGT, then shortly after TO select 'NORMAL' on the Engine Monitor. As you climb the engine monitor will display degrees Rich from the Take-off EGT and you can simply lean back until the difference is zero.
This method, which came to me one night at 3am (sorry 0300hr), has two advantages.

THANKS! ... I never though about.

 

[Ironflight]

My favorite Lycoming Graph!

Peter - that figure you posted is one I have laminated on my kneeboard - with the GRT display of percent power, and the fuel flow meter, it is a no-brainer to see if I am in the correct neighborhood when setting up for cruise!

I like the idea of using a constant EGT (take-off EGT for instance). Someone else mentioned 200 degrees below peak - is there a reference for that? I am always suspicious of absolute EGT numbers, because they depend so much on exactly how far from the exhaust valves they are placed - and that id generally different for different airplanes. but using a value relative to takeoff, or what is "normal" for your plane sounds like a good idea.

Most of these techniques sound good, and are essentially controlling EGT - so once again, what is that protecting? Detonation margin was mentioned - is it that, is it metallurgical (keeping things from being heat damaged? )

Generally a good discussion!

Paul

 

[dan]

Just want to point out that flying by reference to EGT is all well and good...as long as you keep a close eye on CHTs. You might be holding a constant EGT but your CHTs could be going through the roof. Maybe I'm stating the obvious here, and if so, pardon my reiteration of this point. But I haven't heard many people even mention "CHT" yet. Kinda worries me.

 

[flyeyes]

Just want to point out that flying by reference to EGT is all well and good...as long as you keep a close eye on CHTs. You might be holding a constant EGT but your CHTs could be going through the roof. Maybe I'm stating the obvious here, and if so, pardon my reiteration of this point. But I haven't heard many people even mention "CHT" yet. Kinda worries me.

In my case, the CHT sort of goes without saying, as it tracks EGT closely and my baffles seem to work well. I use a self-imposed "redline" of 400 degrees for my CHTs and rarely see it.

The RVs climb so well, and over such a broad range of speeds, that I typically climb at Vy +30 knots, which really helps the temps. If CHT is getting near 400, I either slow down leaning, increase the airspeed a little, or both.

James Freeman

 

[n468ac]

Just want to point out that flying by reference to EGT is all well and good...as long as you keep a close eye on CHTs. You might be holding a constant EGT but your CHTs could be going through the roof. Maybe I'm stating the obvious here, and if so, pardon my reiteration of this point. But I haven't heard many people even mention "CHT" yet. Kinda worries me.

Since we have a fixed prop, i'm leaning to maintain RPM and power during the climb ... but you are correct we watch the CHT, but CHT responds slower than EGT or RPM to mixture changes.

 

[aadamson]

Start here

Paul,

Walter can fill in the blanks as he catches up on his forum reading. But here is his site and the information on "Target EGT". It's an excellent starting point to this disucssion.

http://www.advancedpilot.com/assist.html

 

[Walter Atkinson]

Gentlemen:

John's article on Mixture is a good place to start.

On *most* NA engines (8.5:1 CR), the ideal takeoff EGT at sea level on a standard day is 1250-1300dF. On the 7.5:1 turbo'd engines, the Target EGT will be about 100dF higher) If you hold that temp by leaning as you climb, you will maintain good HP and cool CHTs to altitude.

Go to <http://www.advancedpilot.com> and go to the TECH page to download a free PowerPoint presentation on leaning by Target EGT. It will explain it all.

The advice not to lean below 75% is based in keeping the detonation margin when ROP. It's reasonably good advice to the lowest common denominator of pilots. That does not hold when leaning above 75% if leaning to a LOP setting.

Using peak at 75% does NOT work to find the proper degrees ROP (200?) as mentioned earlier in this thread.

If your sea level takeoff EGT when full rich is above about 1325 in a NA engine with 8.5:1 CR, you do NOT have enough FF.

Take a look at the PowerPoint and I'll be happy to answer any questions anyone might have on it.

(You NEVER lean a TC'd engine in the clmb. Keep that sucker full rich.)

((reducing MP at 1000 feet agl is a suboptimal way to manage the engine. It will result in higher internal cylinder pressures!))

Walter

 

[tin man]

My engine guru (lycon) told me that no two egt probe installations are ecxactly the same, so don't use absolute numbers to set your egt range.
I was told to go to 12,000 DA, full power (65%) and lean to roughness. Use that egt number as your target do not exceed value.
BTW I have yet to see a measurable cht rise do to poor leaning altho I agree it is a good idea to monitor all engine functions.
Tom
RV3
0320, carb, fp prop,

 

[Bill Dicus]

Leaning

For many yeaars we operated a Commanche 260 and then a Lance (300 HP), both with CS props. We spoke fairly extensively with Joe Diblin, the then current guru @ lycomjing. His recommendation was to lean before TO to 100-200 ROP at higher altitudes, to climb at 100 ROP and cruise at peak EGT for 75% power or less. CHT's were always to be monitored - don't exceed published limits. The 260 in the PA-24 was o'hauled at 2160 hours and met factory tolerances except for bearings, which were significantly worn (both crank and cam). The 300 HP Lance also went over 2000 hours with no problems except a crankcase crack which was welded and one bad exhaust valve stem/guide at 600 hours. The formula seems to work OK for these Lycs and the plugs stay clean. From what I've heard Continentals take a different approach. Both our Lycs have 8.5:1 comp. My RV-8 by Lycon will have 10:1 pistons and I have no idea how best to lean that. Any imput would be welcome. Ken @ Lycon seems to like operating rich of peak. LOP op's if done properly may not narrow detonation margins from what I've read, but make me nervous. More of us will be considereing LOP now that gas costs are so high. The GAMI folks may save us a lot of fuel for not much speed loss. I hope there will be lots of real experience published to help us all with leaning. Bill

 

[Ironflight]

Thanks Walter!

Walter - thanks for chiming in - I know you've done a lot of work in this area. I liked the powerpoint presentation, and understand what it is saying, but I still have the question "what are we protecting?" Is it detonation margin? If so, I can understand why we still need what are essentially "indirect" methods of control (without very expensive ground test instruments, we don't know it directly, so we have to use something like EGT...)

I must admit that I am a bit skeptical about absolute EGT's, as I have always been TOLD that measured EGT depends so much on where the probes are placed. Have you got any data that shows how EGT varies with probe placement (ie: for a fixed engine/mixture setting, how the EGT drops as you increase distance from the exhaust flange?). Maybe the variation is not as much as I have always been told!

....and this is still just a thread on leaning in the climb...not about LOP or ROP for cruise...

Paul

 

[N91CZ]

Questions

Go to <http://www.advancedpilot.com> and go to the TECH page to download a free PowerPoint presentation on leaning by Target EGT. It will explain it all.

If your sea level takeoff EGT when full rich is above about 1325 in a NA engine with 8.5:1 CR, you do NOT have enough FF.

Take a look at the PowerPoint and I'll be happy to answer any questions anyone might have on it.

Walter

Walter,
A few questions:
1. How far down the exhaust pipe was the EGT reference of 1325 degF measured?
2. How would one increase full rich fuel flow in a MA4-5 carb (on an O360-A1A)?
3. The Power Point sample data showed an average EGT slightly higher than 1325 (peaked at 1350 in the full rich climb example). Did this IO520 need more fuel also or was it close enough?
thanks
Chris

 

[Walter Atkinson]

The recommended distance from the exhaust flange to the probe is 2 - 4". I shoot for 3" but would rather they all be equidistant if that's not possible. At those insatllation ranges, the data shows reasonable consistency. Closer is hotter, farther is cooler. That's why I gave a range of acceptable Target EGTs on the 8.5:1 CR.

It definitely gets cooler as it moves away from that range and the gasses expand. (Boyle's Law)

In the example PPT, the Target EGT was a teeny bit higher than we'd like and after that data was collected the FF was turned up a small amount to improve it.

We are protecting several things. The engine was certified at the lower FF where detonation margin passed the FAA cert. run..... BUT, we know from hard data collected that that is really not quite rich enough at takeoff power and that adding FF to the mixtures recommended by the OEMs do offer better protection. We are also protecting CHTs and, therefore, the integrity of the metal and its strength under high power.

The beauty of this Target EGT method of leaning is that it works for ANY DA takeoff, winter or summer. ONce you Target is identified, simply lean to that EGT on the takeoff roll and you assured of good HP and being rich enough to keep the detonation margin AND CHTs in line. It's just waaaay too simple to use any other Kentucky windage method.

As for adding FF to a carbed engine, it requires a larger jet. I enlarged the jets in my Twin Beech carbs until they were rich enough. I could tell no difference int he HP produced, but it ran a LOT cooler on takeoff and in climb. BEWARE, it's VERY easy to over-do it.

Walter

 

[gvgoff99]

Detonation?

I have heard a lot about detonation since I started flying but never has anyone told me how to recognize it. In an auto it is the pinging we get when loading the engine (rapid acceleration, going up a hill, etc.) which if done over a long period probably screws up the engine but does not seem to do much harm over a tank of "bad" gasoline.

What are the signs and symptoms in a Lycoming? What harm does it do if it is occasional (undetected?)? If once someone describes it in an aircraft engine several of us may think, "Oh no, that has happened to me" what should we do? MOH, keep flying, pray a lot before and during flight ?

I am presuming that the "pinging" in an auto would be pretty undetectable in any audible way in an airplane. Thanks

 

[Kevin Horton]

I have heard a lot about detonation since I started flying but never has anyone told me how to recognize it. In an auto it is the pinging we get when loading the engine (rapid acceleration, going up a hill, etc.) which if done over a long period probably screws up the engine but does not seem to do much harm over a tank of "bad" gasoline.

You recognize it by the damage on the piston that you see when you pull the engine apart following the sudden engine failure.

There is too much vibration and noise to feel detonation from the cockpit.

 

[gvgoff99]

Detonation?

Kevin, I think my question is a valid one and I assume that you have the same concept as I about detonation. (That there is no good way to recognize it prior to some sort of engine failure.) Are we both wrong?

I was wondering if someone actually has done some research on the subject and if there is some indicator one could look for prior to catastrophic failure. Is the first detonation event going to crater the engine or is there some warning that would show up on the CHT, RPM, EGT or other engine parameter that would tip us off so that we might take some preventive action PRIOR to your scenario? I have heard that CHT goes up but do not know if that is an accurate concept or if the CHT change would be rapid enough to be of any use. I acknowledged in my first post that cockpit noise would most likely drown out any subtle sounds that one experiences in an auto.

My reason for inquiring is that with the various new ignition systems leaning is only one parameter with which we must deal. With the variables introduced with the newer EI's of having our engines advanced well into the 30's BTDC combined with a choice of 100LL or mogas and then throw in leaning it would be nice to hear from someone on ways to recognize detonation (if any exist) prior to the scenario which you portrayed.
Thanks to everyone on the advice on ways to avoid problems.

 

[Yukon]

Detonation

George,

As Kevin said, there is currently no way of detecting detonation in lightplane engines other than by evidence of catastrophic damage. Having said that, I'm sure we will hear from Walter Atkinson about the FADEC GAMI is working on to detect and control detonation.

My question to you is why do you seek to run so close to the detonation point in your airplane? Even if such equipment is eventually brought to market, it could malfunction and put you down. For a gallon an hour, why take the chance?

 

[gvgoff99]

Detonation

John, Thanks for the answer. Not comforting but a good answer. Actually, I do not choose to run close to detonation but "stuff" happens. People build these things, people set the timing, people make the fuel and some choose to use mogas (I use 100 LL), Timing gets set improperly, fuel can be contaminated (though 100 LL is probably about as standardized and clean as fuel gets) and most of the newer experimental EI's are in a test stage on our aircraft and it is VERY conceivable the timing could drift into the detonation area.
I was looking for some hope of detecting detonation in the event some human error creeps in with my P-Mags. The human error could be mine, the manufacturer of the ignition system or more remotely the fuel distributor?s error. It also could be a lethal combination of errors. Hopefully none of the above ever occurs. I tend to run rich below 8000 DA. I do lean pretty aggressively when I know that I am below 75% on the power curve in cruise flight mode.

 

[Yukon]

P-Mags

George,
Good, you're the guy to ask! What's this P-Mag, E-Mag buzz? Why would I want to give my ignition system the authority to advance my ignition to 40 deg BTDC, ever? How much fuel is saved? Seems like the downside of uncontrolled advance is awfully steep???

I've spent 35 safe and sane years behind dual magnetos, can't imagine anything better! Tell me where I go wrong.......

 

[dan]

Yukon, on another thread you wrote:

...I objected strenuously to Dan Checkoway's promotion of leaning at initial climb power.

I came back to this thread and found your "strenuous objection" reply was deleted. I was actually kind of surprised by that.

Do you need clarification of what I was saying I do technique-wise? If you feel that I'm endangering myself or others, or causing potential engine damage, please speak up with a CONSTRUCTIVE suggestion.

Walter & Deakin's advocacy of leaning to a "target EGT" is almost exactly what I do. Cyl #1 gets leaned to about 1275, and then I watch CHTs like a hawk. It's the rate of CHT change that I'm watching, and that I feel is most important -- and to be honest I'm surprised I'm the only person hear preaching about CHT rates.

My CHTs never exceed 370F, so I'm not too worried about the metallurgical impact of "running hot." But I am concerned about the potential consequence of aggressive leaning under high power, that being detonation.

So while "target EGT" is not my primary reference, it's essentially the technique I'm using, plus or minus. I am "regulating my CHTs" with the mixture control. Don't get me wrong...I'm not "chasing" the CHTs around with mixture, but I do make small adjustments.

And different conditions warrant different responses. The "target EGT" thing is all well and good, but it's such a broad stroke that I can't recommend that technique across the board. All things being equal...that is, OAT for altitude, airspeed in the climb, rate of climb, etc., sure, "target EGT" works just fine.

But toss in a non-standard day or non-standard conditions/constraints, and the "target EGT" method is too broad a stroke for my taste.

Case in point...I'm departing out of a strip with terrain pretty much all around, and I'm climbing at Vx for a bit and then Vy for a while. Normally I climb at say 115-120 KIAS, but on this particular day I need to climb at say 100 KIAS for some brief (5-6 minutes) but relatively extended period of time.

Target EGT is NOT how I lean my engine. It's a starting point, but I'm feeding in more fuel if the CHTs are running either hotter than normal, or climbing at a discernable rate.

In my book, it's CHT rate that is the BEST indicator of the onset of detonation. Perhaps I'm naive in thinking that.

 

[dan]

I don't need clarification of anything. Your posts speak for themselves, many if not most in direct contradiction of Lycoming directives.

I dare not say anymore though, as this too may evaporate into thin air.

As often as we seem to disagree (or more appropriately put: butt heads), I hope your posts don't get deleted.

I hear you loud & clear now. You're advocating what Lycoming advocates. Understood.

 

[Yukon]

Butt Head

Yes Dan, as popular as it is to challenge authority nowdays, I still see the designer, builder and distributor of the Lycoming design as my authority.
I feel very strongly, as does Lycoming, that your insistance in dredging up the last drop of fuel efficiency from these engines will ultimately result in tragedy for some poor newbie.

Just listen to these guys naively disussing how to detect and skirt detonation,
as if it were an easy task. This is a disturbing trend.

Who you calling a Butt Head?

 

[aadamson]

If I could chime in.

Yes Dan, as popular as it is to challenge authority nowdays, I still see the designer, builder and distributor of the Lycoming design as my authority.
I feel very strongly, as does Lycoming, that your insistance in dredging up the last drop of fuel efficiency from these engines will ultimately result in tragedy for some poor newbie.

Just listen to these guys naively disussing how to detect and skirt detonation,
as if it were an easy task. This is a disturbing trend.

Who you calling a Butt Head?

Isn't Democracy and the freedom we enjoy a wonderful thing... As they say, "to each their own".

As for me and my money, I think I like the practicality of todays science and engineering and it's application to 40+ year old engine designs. BTW, I don't think Lycoming invented the HO engine, but they certainly did apply it to an airplane and thankfully so.

Just because it's been documented for 40 years, doesn't mean it's the Best way. It just happens to be a way that Lycoming feels is Risk adverse from todays Letigius environment. In fact, and I'll let Walter quote chapter and verse,, but I believe Lycoming publishes differening documentation for differing engines. My IO-540 in my 2004 C182 for example, advocates running at "peak lean" for cruise and all of Cessna's charts are based upon Peak.

Also, there is a placard in the cockpit with climb performance. It's listed in fuel flow for every 2K feet. Just for kicks I looked at the EGT/CHT's for those flows at the altitudes given. You'd be shocked to know what they are..... and I found them when in level flight at the given altitude. Probably much worse in climb.

Using the Target EGT method, I check the EGT/CHT's for those same altutudes and they were *way* better with lots less stress on the engine.

Ok, so back to each his own. Just because one person believes and opperates a specific way *does not* mean it's wrong! It just may be counter to whats been published for 40 years! But certainly *not* wrong.

 

[David-aviator]

George,

As Kevin said, there is currently no way of detecting detonation in lightplane engines other than by evidence of catastrophic damage. Having said that, I'm sure we will hear from Walter Atkinson about the FADEC GAMI is working on to detect and control detonation.

My question to you is why do you seek to run so close to the detonation point in your airplane? Even if such equipment is eventually brought to market, it could malfunction and put you down. For a gallon an hour, why take the chance?

John,

This is why the Subaru H6 is so cool. There is no knock or detonation with this engine. Sensors tell the ECU what's going on and ignition and injector timing are adjusted to prevent it.

Lycoming says it is OK to lean anytime when at 65% power, at least that's what the Flyer said some years ago. On a very hot day, it doesn't take much throttle reduction to be at 65%. On that premise alone, I leaned the engine (in my Lycoming days). Another indicator was fuel flow. With an accurate rate indication, there is no way the engine needs 15-16 gph on a hot day. The fuel air ratio is probably running at 8:1 when it should be 11 or 12:1 for take off.

Anyway, didn't mean to rattle your cage again re the H6. But could not resist jumping in.....

dd

 

[Yukon]

Hot Momma

David,

On a "very hot day", I would imagine high cylinder head temps alone would preclude very much leaning. But see David, this is why Lycoming establishes
conservative guidelines for it's operating parameters. Where's the harm in operating an engine a little rich when detonation is a concern?

As for the ability of the Subaru to detect and limit detonation, you can have it! From what I've been reading, you're still running a little "hot under the collar" (cowling).

 

[fodrv7]

Questioning Autority

John,
I don't think Dan (nor I or others here) are Challenging the Authority of the engine manufacturer. We all recognise that they have built a big lazy slow revving engines for reliability and also that they have offered, over the years, a simple way of running the engine (Leaning) so as to ADD to the inherent reliability.

If there is any challenging going on here it is being done by those with vastly more knowledge of the combustion proccess than us. Deakin and Atkinson to name a couple. But, even they are rather adding to the knowledge rather than challenging it.

But most of the kowledge has been around for decades. It is just being bought to our attention.

The knowledge that has been around since the massive radials on DC-6/7s and Super Connies and applied by professionals, then of course FEs, and now we are adapting it to our engines
The reason it was able to be done on the DC-6/7s and Super Connies was because they then had the instrumentation. As a youth I sat in a DC-6 and watch the FE check the ignition of every spark plug on all engines on a CRT like they use to tune your car in the better workshops. They had an Engine Analyzer onboard.
Now that we have almost the same information on our engines we can adopt some of those techniques and dispense with those that the engine manufacturer developed for the Cessna pilot with one CHT (With just Green and Red calibration), no Fuel Flow nor an EGT.

But we aren't challenging them.

Maybe, if it was not for the modern obsession with litigation the manufacturers would come out with a detailed proceedure for running their engines for those equipped with engine monitors.

Pete.

 

[David-aviator]

David,


As for the ability of the Subaru to detect and limit detonation, you can have it! From what I've been reading, you're still running a little "hot under the collar" (cowling).

Yep, just like my 0360 friends are bumping 243F with their oil temp on these hot, rotten days.

Yesterday on a 200 nm cross country, the thing got me up to 10.5 in 14 minutes without ringing a single over heat bell, OAT was 82 first leg, 95 the second. It also got me to and from OSH without an off field landing. Things are looking up

dd

 

[Yukon]

Humor

Got to give it to you David, you've got a great sense of humor!

 

[gvgoff99]

Detonation

John, Actually, that is why I have been looking for an early warning for detonation. I have been running my P-mags for about 48 hours and the fuel consumption is about 3/4 of a gallon less per hour in my O-320 E2D (160HP)with a Catto two blade prop than my other RV friends with mags. The first 40 hours were trouble free the last eight have been an increasing amount of roughness. I have removed the mags and sent them to Brad at E-Mag. Fortunately, E-Mag is very service oriented. Once they look at the mags I will know for certain if that is the problem (everything points to them). Hence from this experience my inquiry about detonation arose. Have I experienced it? Especially it would be good to know what symptoms detonation produce prior to engine failure that one might recognize.
My symptoms were occasional engine hesitation in climb and smooth running in cruise. Of course this happened on a trip to North Carolina and 1000 miles from home! I have mailed the mags back to E-Mag but will have to borrow my son-in-laws truck to get home. He is in Iraq (AF pilot) so does not need the truck.
As for the P-Mags I like them. Timing is a piece of cake, start up is flawless, economy is good (at the price of fuel I think they will pay for themselves in about 400 hours IF all goes well with the engine) but I would probably recommend a combo E (or P)-Mag with a regular magneto at this point. That opinion could easily change over the next year in a + or ? way. I like the technology of advancing ignition timing but would like to see some advanced notice of detonation before the engine clunks to a halt at the worst possible moment! Like an auto I suspect the engine is most apt to detonate when under a load (climbing at full power).
I was hoping that someone had some subtle signs of early detonation that one could recognize. It seems that it is a mystery subject that is unexplored except to recognize that eventual engine failure is the result.

 

[Yukon]

Boroscope

The only thing you can do if you suspect detonation is to pull the cylinders. Before doing this, possibly someone at your airport has a boroscope and could examine your pistons for damage through the spark plug holes.

So if I understand your post, you are using these mags to save 3/4 of a gallon per hour??? Is there any other benefit??? More power????

Have you checked for other causes of roughness like plugs, induction leaks,
carb faults, wires etc.

Mahlon???????

 

[Ironflight]

Flight Data (Somewhat Qualitative)

"In God We Trust - All Others, bring Data!"

That is the motto we live by in space flight operations. Stories, opinion, assumptions.....all carry little weight, unless you can back them up with actual test data. These are machines, after all, and they should behave in a predictable manner!

So I decided it was a nice evening to go flying, and with nothing better to do, it seemed like taking a look at some actual climb data might be helpful. Just so folks don't mis-understand, I basically fly the engine the way I mentioned in the first post of this thread - keep it full rich above 75% power, unless I've gotten above 5,000', and then I lean a bit.

But I was very curious about this "target EGT" idea, so after applying full take-off power, I noted the EGT's. As I climbed, I then watched for them to drop, and sure enough, they did - but fairly slowly. As a matter of fact, after a climb to 5,000' (which took about 3 minutes), they had only dropped about 50 degrees- not a heck of a lot. At that point, I leaned until I got the 50 degrees back - and lo and behold, I was right dead smack on the fuel flow line shown in the chart that Peter posted a few pages back in this thread! As I said...I really like that graph. (Note that I was climbing out from Sea Level with an air temp of 91 degrees F - it just doesn't want to cool of around here!)

Now something has always bothered me about that chart, because it has a feature that I just wasn't smart enough to figure out - the "knee" in the curve between 72% and 82%. Below that point, the line is basically straight, as it is above. So what is the "physics" that causes the knee?

Now I'm leaving the realm of data here...just making an educated guess - but I'd say that that is the point where the Lycoming guys said "OK, let's add some fuel for the higher power setting!" It still makes me wonder, however, if this was done mathematically (there is some numerical relationship that defines the best mixture), or if it is simply empirical - they tested a lot of different power/mixture points, and arbitrarily added a certain fuel flow at higher power to cover against detonation. I'd sure like to know...but I bet the guys that generated those curves have long since retired...

Paul

 

[gvgoff99]

More power?

John, I do not have means of checking if I am getting more power. GAMI folks do that sort of stuff. The fact that I fly as fast as other RV-6 folks at the same RPM using less fuel implies, I guess, that I get more energy per gallon than they are getting. That leaves me to believe I am getting equivalent HP using less energy (fuel).
Unfortunately, this does not take into account a lot of other variables like drag, age of the engines, leaning techniques, weight of the plane (pilot) etc. So without a dynamometer I will remain ignorant.
I do like the variable timing of EI. Flying behind a technology equivalent to the most simplistic lawn mower engine has always seemed arcane to me. I recognize that such companies as E-MAG are going to have problems developing their product but I am willing to be a ?test pilot? so that others will have something better in the future. I also like fuel efficiency in everything so that future generations will have a world that has enough oil so that they can fly too.

 

[Yukon]

John, I do not have means of checking if I am getting more power. GAMI folks do that sort of stuff. The fact that I fly as fast as other RV-6 folks at the same RPM using less fuel implies, I guess, that I get more energy per gallon than they are getting. That leaves me to believe I am getting equivalent HP using less energy (fuel).
Unfortunately, this does not take into account a lot of other variables like drag, age of the engines, leaning techniques, weight of the plane (pilot) etc. So without a dynamometer I will remain ignorant.
I do like the variable timing of EI. Flying behind a technology equivalent to the most simplistic lawn mower engine has always seemed arcane to me. I recognize that such companies as E-MAG are going to have problems developing their product but I am willing to be a ?test pilot? so that others will have something better in the future. I also like fuel efficiency in everything so that future generations will have a world that has enough oil so that they can fly too.

Keep us posted!!!!

 

[gvgoff99]

Data

Paul, I too like data and most of my posts have been trying to find what data to look for to see if one is getting detonation. It seems that if such data exists it is unknown to all of us reading this forum; imcluding me. I would think that there must be some engine monitor reading that would give a hint prior to detonation giving a coup de grace to the engine. As it stands now in this forum the only way one would know detonation is happening is sudden engine stoppage. I find that scientifically hard to believe though it may be as far as the knowledge base on this subject goes.
There are several good posts on ways to avoid detonation.....but if engine failure is the only indicator of detonation how do we know that we are avoiding it until it is too late? We could be leaning conservatively and because the timing is all screwed up, presto the engine disintegrates before our eyes without warning? I doubt that is the case so I am still looking for answers to how to detect early signs of detonation. Engine roughness, I would think, might be a sign in lieu of any other symptom but the roughness should affect the engine monitoring gauges.

 

[gvgoff99]

Posted

Keep us posted!!!!

John, I will. Thanks, George

 

[gmcjetpilot]

Not the same fuel system

As a matter of fact, after a climb to 5,000' (which took about 3 minutes), they had only dropped about 50 degrees- not a heck of a lot.

BINGO!!

I noticed that as well. Very little change to 5,000 feet DA (which fits Lycomings recommendations).


First some one mentioned wide open throttle climbs are the best thing to, I think Walter. That may be true on a Continental but not the Carbed O-360 Lyc. The fuel metering systems on a Lycoming (Carb or Fuel Injection) are different than many (most) Contenentals. This feature both in the Carb and fuel injection found on Lycomings does some limited compensation for altitude. This reduces the need or benifit of manual leaning in climb. With WOT you OVERRIDE this economizer feature.

You observation Ironflight and mine as well is there is little change in the first 5,000 feet. This has to do in part with a fuel system (carb) that "automatically" compensate as you climb. Not all do this (e.g., Continental). You certainly can do WOT climbs all day, but you are by-passing the fuel economizer feature of the carburetor. This feature leans for you!

Also FI systems on Lycs are fundamentally different than many (most?) Contenentals. They also lean naturally as you climb because the air is less dense. Lyc FI is an air-mass system. Continentals are often mechanical and only look at engine RPM and throttle postion. That is why "Target EGT" is of more benifit to those operators of fuel systems that don't lean or "economize" as you climb.



Here is typical MA-4-5 carb. These carbs have an air-bleed economizer.


The lean as you climb featyre only works if the throttle is off the full WOT stop. A Carb is naturally an air mass system anyway, providing less fuel as you climb. The economizer enhances this natural characteristic. Cool, so don't worry about leaning in climb too much. If you want to fly or climb wide open and manually lean you are making work for yourself.


Usually after take off I go 25 square and add throttle as I climb to maintain 25". Once at full throttle and manifold pressure starts to drops to 24" (about 5,000 feet), I crack the mixture back from rich to get the EGT to move but no more. As you mentioned Ironflight the EGT was only 50F off from takeoff peak to 5,000 feet. So it does not take a lot of leaning since the Carb is doing it FOR YOU!



Why not lean with the "Target Method"

We are still at about 83% power, and I don't spend time perfecting a "Target EGT" in climb. Lycoming tells me that I should not LEAN above 75% power. Why? detonation. (see ** note **)

It's a moving target and I'll be leveling off and setting cruise power/mixture in minutes anyway. Also with the self leaning feature of most Lycs the need to manual lean is not there, like it is with Contenentals.​

"Target EGT" does not make as much difference in RV's with small Lycs. First many fuel metering systems are leaning already for you (except may be Continental). Second there's very little change till you get to 5,000 feet DA. Also we climb very fast and are not climbing for long.

My technique has always been to always leave it rich until about 5,000 feet and crack the mixture just to get the EGT to move. My next lean is usually after leveling off at my typical cruise altitude of 8.5 or 9.5, below 75% power. If climbing to a much higher altitude, I lean for best power (peak) and than enrichen (100F) or use fuel flow (which I have). This is a variation on the "Target EGT" technique, but it's in line with Lycomings recommendations. Here is Lycs recommendation:
Lyc leaning at altitudes about 5K

Basically you can lean for take off, climb or cruise if above 5,000 feet or below 75% power, using fuel flow or EGT or last smoothness (not every one has EGT gauges).

My two issues with the "Target EGT" method is between sea level and 5,000 is we above 75% power, and you should be flying the plane not monkeying with the mixture. You have to look down a little, right. It may not be a big deal but what is the gain in a Lyc powered RV (not a Bonanza). We are at 5,000 feet in just a few minutes.

If you follow Lycomings recommendation you will see they allow leaning for "high density altitude", takeoff, climb and cruise. In climb it's transient. Not saying don't or not worth it (for you), but just be realistic in what you are getting for your effort. At least with LOP in cruise you have a longer period of steady state flight to benifit.

Is the target EGT is a bad idea? No. Just know what you are getting into and how your fuel metering works. What works for Continental does not apply to a Lycoming.

Read AFM's (Airplane Flight Manual) for certified planes with a similar engine to your Lyc. These are certified procedures that many smart people have looked over. You can blow it off as fear of law suites but that is a simplistic comment. Things like reducing power on takeoff (with economizing Carbs) is not an arbitrary thing as we see.


Cheers


FOR YOU CARB GUYS HERE IS SOME GREAT INFO:

If you want an operation manual for your Precision Airmotive Carb MA-4-5, MA-3 or MA-4

http://www.precisionairmotive.com/

Select:

Support
MSA float carburetors
MSA Float Carburetor Handbook
Read the Book
(also a trouble shooting guide)​

I have heard a lot about detonation since I started flying but never has anyone told me how to recognize it.

** NOTE **
(Detonation: Can you tell if you are detonating? No. Yes EGT goes down and CHT goes up during detonation, but than it's a little late, and are you sharp enough to notice? You may get distracted. Water cooled little bore engines are not big bore air cooled engines, so cars can tolerated detonation better and besides you can hear it. Walter talks about combustion pressure probes, which will indicate a detonation by a pressure spike, but we don't have this info. I doubt pressure probes will ever be practical for daily flying. The longevity of these probes is in question. One big issue is there's no room for a pressure probe in the cylinder head. Pressure probes that piggy back on spark plug are custom and are inaccurate. Car's use piezo microphones to listen for the "PING", but they don't work on aircraft due to noise. So what is the DATA? Let's be conservative and follow good practice based on 100,000's hours test cell and flight test the manufacture did to protect ourselves. The RULES of operation is what gives you the protection. 75% power is key. Is 79% OK? May be on a good day. May be is not good enough for me.)

 

[fodrv7]

Huh!

Next Please!

Pete

 

[gmcjetpilot]

You have a question?

Next Please!

Pete

What don't you get Pete.

Fuel systems (not all) lean automatically as you climb?

Target EGT is not a big savings for systems that lean or "economize" in climb, which is most Lycomings with both Carbs and fuel Injection. Go out and fly and tell me how much EGT rise you see from sea level to 5,000 feet.

Target EGT requires or suggest you lean above 75% power, against Lycoming recommendation due to detonation margins.​

I think they are all good points. The point is the target egt method may work better or more dramatically on a Continental engine, which as no altitude compensation in its fuel system. I think that is a cool observation.

What don't you get? Do you have a useful comment or question ?

Sorry if you don't like my comments but there are 3,999 other readers and some have MA-4-5 carbs with economizers. I'll do better next time.

 

[fodrv7]

Sorry George.

Sorry George. You once told me to offer something rather than just criticise. And I should have.
I just don't understand why you go out and do a flight test to confirm a reported phenomona, confirm it and then argue against what you saw.

The EGT does decrease on the climb.
The carby may have a degree of pressure compensation but it is not a "Pressure Compensated Carburettor".
There is no 5min limit on TO power that there is on so many aircraft you have flown and besides that within 5 mins an RV has climbed so high that you are no longer at TO power.
Lycomings do operate excessively rich above 80%. I posted a graph to show it. So I am sticking with Deakin on Full throttle climbs.

As so many have said, it is not about contolling EGT, BUT USING EGT to maintain cool and constant CHT.
So to answer your question again. "What don't I get?"
I just don't understand why you go out and do a flight test to confirm a reported phenomona, confirm it and then argue against what you saw.
Pete.
Apologise for my unwarranted sarcasm.
Pete.

 

[Yukon]

Down Under

George,

Informative post, George. Where do you get the time and patience to create such works of art? Too bad it's wasted on the penal colony

 

[fodrv7]

Us convicts

Now, John that made me laugh.
Pete.

PS. Unfortunately my ancestors came here during the Gold Rush, not earlier as convicts. I say, unfortunately, for 'convict' heritage in Australia affords a certain desirable status. Fit's in with the Aussie refusal to respect autority just because it's there, without it earning respect.
P.

 

[gmcjetpilot]

That is all

Sorry George. You once told me to offer something rather than just criticise. And I should have.
I just don't understand why you go out and do a flight test to confirm a reported phenomena, confirm it and then argue against what you saw.

The EGT does decrease on the climb.
The carby may have a degree of pressure compensation but it is not a "Pressure Compensated Carburettor".
There is no 5min limit on TO power that there is on so many aircraft you have flown and besides that within 5 mins an RV has climbed so high that you are no longer at TO power.
Lycomings do operate excessively rich above 80%. I posted a graph to show it. So I am sticking with Deakin on Full throttle climbs.

As so many have said, it is not about controlling EGT, BUT USING EGT to maintain cool and constant CHT.
So to answer your question again. "What don't I get?"
I just don't understand why you go out and do a flight test to confirm a reported phenomena, confirm it and then argue against what you saw.
Pete.
Apologise for my unwarranted sarcasm.
Pete.

Actually you are right and it was poorly worded, I trimmed.

I agree with everything you said. I looked at the AVweb article and it was enough to prompt me to call Lyc but could not get a hold of the main man. It is a dramatic graph they show, but I think it is unique to that engine they tested. I don't think that it applies to a Lyc AT ALL.

I get the concept and think it has merit. However if your EGT only drops 50F in 5,000 feet with out your help, than what is all the fuss about?

That is why we are talking. The other important point is leaning at higher power. Just be careful. That is all I have to say; it is not a big benifit to use who have Lycs (with altitude compensation fuel metering Carb or FI).

The other point is I have other things to do below 5,000 feet than constant engine management. Some eagle eye might call me on my hypocrisy, because I do milk the throttle an inch at a time in climb, but I can do that in my sleep with out looking in the cockpit. I am sure others can make the same argument, that they can lean with ease as well. Fair enough.

My last comment, point or observation is FI Continentals which pump out the same fuel at sea level as they do at 8,000 based on RPM and throttle position only, GET real RICH as you climb. YOU HAVE TO LEAN THEM. I don't think you would see charts like what you saw in the AvWeb article for the Continental, if it where a Lyc powered RV. HEY I COULD BE WRONG.

So my point is we would test this on our planes and engines. I don't think all engines and airframes are the same. I don't think Deakin talks for our little dinky 4 bangers. Just my opinion. When Walter says WOT to cruise alt, fine, but is he talking about a Carbed Lyc with an economizer or a mechanical Continental.

Really that is all I got. If you want full throttle climbs COOL BEANS. However if you have a Carb'ed O-360 and if you would just pinch the throttle back a little after takeoff the Carb will do most of the leaning for you, at least to 5,000 feet.

Cheers G

PS your flight engineer story with the oscilloscope was cool, useless but very worthy. I talked to a B-36 guy about 6 years ago and they had lots of plugs to watch. I would have loved to see that.