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Is it going lean ?

Old 03-20-2012, 11:50 AM
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Ed
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Default Is it going lean ?

Is there any way of telling if an engine is going lean while the plane is flying ? Does it change sound, and slow down, like it's possably over heating ?

ed
Old 03-20-2012, 02:09 PM
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w8ye
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Default RE: Is it going lean ?

I can tell all about the mixture just be listening to the engine in the air.

When they get lean - they get saggy

When they are rich, they start trying to four stroke if it is a two stroke engine. The four stroke engines begin to run rough.
Old 03-20-2012, 02:31 PM
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Default RE: Is it going lean ?

ORIGINAL: Ed

Is there any way of telling if an engine is going lean while the plane is flying ? Does it change sound, and slow down, like it's possably over heating ?

ed
Yes, it changes sound.
Yes, it can slow down (partly because of overheating caused by the lean condition and partly because of the lean condition itself)
Yes, it will overheat.

The truly best way to find out is not a simple answer.
Measure the cylinder head temps in flight - for this you will need something like the Venom Temperature gauge or Eagle tree setup. Ideally measure it at the base of the spark plug (they have a thermocoupe available for this) (Also ideally measure the Exhaust Gas temps but few ever go that far).

Take out the spark plug and have a look at it.

[link]http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp[/link]
[link]http://www.strappe.com/plugs.html[/link]
[link]http://www.theultralightplace.com/sparkplugs.htm[/link]
[link]http://www.bcchapel.org/pages/0003/pg11.htm[/link]
Old 03-20-2012, 02:42 PM
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Ed
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Default RE: Is it going lean ?

" Take out the spark plug and have a look at it. " Yes, I know that's always one of the best ways, but I was looking for some early indication in the air, and getting it backdown on the ground in a hurry, if needed.

ed
Old 03-20-2012, 04:18 PM
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Default RE: Is it going lean ?

Open the needle 1/2 a turn and see if it gets better.
Old 03-20-2012, 06:00 PM
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Ed
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Default RE: Is it going lean ?


ORIGINAL: Scota4570

Open the needle 1/2 a turn and see if it gets better.
Please read the original post. Thank you.
Old 03-20-2012, 06:34 PM
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Default RE: Is it going lean ?


ORIGINAL: Ed

Is there any way of telling if an engine is going lean while the plane is flying ? Does it change sound, and slow down, like it's possably over heating ?

ed
YES
Old 03-21-2012, 02:47 PM
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Default RE: Is it going lean ?


ORIGINAL: Scota4570

Open the needle 1/2 a turn and see if it gets better.

That is quite a lot. Try 1/8 turn.

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Old 03-21-2012, 03:16 PM
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Ed
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Default RE: Is it going lean ?

While the plane is flying ? While the plane is flying ? While the plane is flying ? Read the post ! Sheeech
Old 03-21-2012, 03:42 PM
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Default RE: Is it going lean ?

No need to yell. I was responding to the amount of needle adjustment recommendation.
I did read the original post and yes you can tell by sound while in the air. Someone else already said that so I added the other.
When you adjust on the ground for peak rpm back it off slightly, perhaps 1/8 turn or maybe 100-200 rpm.
I was just trying to point out not to make a very large, 1/2 turn is large, needle adjustment at a time.


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Old 03-22-2012, 02:43 AM
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Default RE: Is it going lean ?

A lean engine will tend to sag or slow down when you go vertical.
Old 03-22-2012, 03:52 AM
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Default RE: Is it going lean ?

No doubt others have better ears than me... but I can't tell about the mixture by the sound while flying. I hear sound changes but think they are due more to the loading of the prop or maybe to a small degree the position of the exhaust stack relative to my ears. Nor can I detect the subtle differences in performance that come from minor over heating. Sure... grossly lean might be noted by poor flight performance but my guess is that for a lot of engines that die too lean, the pilot sensed no warning.

I've had vent lines kink and finally starve a gas engine and kill it lean and sensed no warning until the engine died.
Old 03-22-2012, 05:34 AM
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Default RE: Is it going lean ?


ORIGINAL: AA5BY

No doubt others have better ears than me... but I can't tell about the mixture by the sound while flying. I hear sound changes but think they are due more to the loading of the prop or maybe to a small degree the position of the exhaust stack relative to my ears. Nor can I detect the subtle differences in performance that come from minor over heating. Sure... grossly lean might be noted by poor flight performance but my guess is that for a lot of engines that die too lean, the pilot sensed no warning.

I've had vent lines kink and finally starve a gas engine and kill it lean and sensed no warning until the engine died.
You owe it to yourself to play with the needle a little and then listen to the engine in the air and learn the subtle differences in sound as to the way the engine runs

Old 03-22-2012, 08:01 AM
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Default RE: Is it going lean ?

No doubt you are correct but as a Ham, you might appreciate the variance in the ability to deal with sound. Some ops, can learn 20wpm fairly easy. Many years ago, if I'd known how hard it was to get to 20wpm, I doubt I'd taken the task on. I made it... but only because of being too stubborn to give up... it was really hard. It required a year of work with almost every evening devoted to an hour of practice.

As you say, if I changed the mixtures and flew then I might be able to sort out what sounds were not prop load related or positioning of the exhaust to my ear... and if that was what was needed to ensure good operation, I'd likely put the effort to it. Fortunately, I don't think it is necessary as I believe I can do about the same on the ground without the load changes and positioning changes so that my ears don't have to sort out those subtleties from the telltale sound of an engine wanting a richer mixture.

I completely believe that some can do so... but I also believe that some can't.
Old 03-22-2012, 09:36 AM
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Default RE: Is it going lean ?


ORIGINAL: AA5BY

No doubt you are correct but as a Ham, you might appreciate the variance in the ability to deal with sound. Some ops, can learn 20wpm fairly easy. Many years ago, if I'd known how hard it was to get to 20wpm, I doubt I'd taken the task on. I made it... but only because of being too stubborn to give up... it was really hard. It required a year of work with almost every evening devoted to an hour of practice.

As you say, if I changed the mixtures and flew then I might be able to sort out what sounds were not prop load related or positioning of the exhaust to my ear... and if that was what was needed to ensure good operation, I'd likely put the effort to it. Fortunately, I don't think it is necessary as I believe I can do about the same on the ground without the load changes and positioning changes so that my ears don't have to sort out those subtleties from the telltale sound of an engine wanting a richer mixture.

I completely believe that some can do so... but I also believe that some can't.
I put out the same effort as you to learn 20wpm back 30 something years ago. My one middle aged son has his Extra rating and is lucky to know one letter of code. If he gets interested, I'm sure he will get the computer to decode it?

From what you say, I doubt you ever went through the games of listening to several CW QSO's at once and practicing picking out the copy of just one of them? With CW you can pick out operator mood and temperment, skill, personality, knowledge, equipment, and just about anything else you might notice the same as from a voice conversation.

If you felt the need of being able to learn rich from lean in the air with your engines - you would have practiced and done so by now?

At the field, If I happen to even notice, the way you run your engines - good or bad - I will not say anything to you or anyone else or even consider it unless asked to listen and worry more about how my own engines run as I have for close to 60 years.

The way you run your engines is none of my business.

I just want you to know that the clues are there if you care to listen.

73's



Old 03-23-2012, 09:06 AM
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Default RE: Is it going lean ?

If you want to know if it is running lean in the air you can use a data recorder and check engine temp. With some practice you will find you can tell something about
how the engine is set by listening to it. Just like the guys said it is like learning code it takes some time, I copy CW at 35 words a minute but it took quite a while to get to that speed, AB9K
Old 03-23-2012, 06:05 PM
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Default RE: Is it going lean ?

I'm wondering if someone that believes they can tell in the air by sound if the engine is too lean, describe what sound they are listening to and at what point in flight do you listen for it? Large propellers on gas planes simply offer such a wide variety of noise from when they are loaded, unloaded, and braking... how do you weed out those sounds? The bark of the exhaust stack opposing or facing is different. Even the Doppler shift coming toward or going away plays its factor.

Far more notable to me is time, rather than sound.... whether the engine is failing to spool up quickly as I remember normal for it? This might be a little bit like depth perception, ie depth perception is not the ability of the eye to discern distance... it is the discerning of distance by the input of many senses. Relative size, comparison, sound, clarity, and mental hysteresis or dead reckoning. Some would argue they are doing depth perception with their eyes only... and I'd suggest probably not.

Frankly, for those who feel they can detect too lean by sound only, with all do respect, I wonder if they are not giving credit to some of the other senses that make it possible.
Old 03-23-2012, 06:29 PM
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Default RE: Is it going lean ?


ORIGINAL: AA5BY

Large propellers on gas planes simply offer such a wide variety of noise from when they are loaded, unloaded, and braking... how do you weed out those sounds? The bark of the exhaust stack opposing or facing is different. Even the Doppler shift coming toward or going away plays its factor.

Far more notable to me is time, rather than sound.... whether the engine is failing to spool up quickly as I remember normal for it?

Frankly, I wonder if they are not giving credit to some of the other senses that make it possible.
I think you have the right idea.

Fly a lot - listen to other guys planes, and you will pick up on all this and you will eventually be a expert just like learning the code. I think it is easier to learn than the code actually.


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