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#1
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Leaning using EGT - Lycoming O-540 (Aztec)
On my first flight in the Aztec with a fellow pilot who was doing the
flying, he stated to lean using the EGT (a recently installed Electronics International digital single probe device)to circa 1300 and no higher than 1350. The aircraft does not have a CHT. I am totally new to operating larger engines like the O-540 (no fuel injection here) and want to ensure I dont damage anything. I hear a lot of talk and hearsay about LOP/ROP leaning procedures. Like most owners, I want to operate my aircraft efficiently, but not to the detriment of engine reliability. Any advice is welcome. Regards, Dean |
#2
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Take it up to 10,000'. Push the throttle and prop full forward. Lean to
maximum rpm. Note your EGT. Now, for ALL operations, lean to that EGT (or as high an EGT as you can get). You will be running rich of peak. Quite a bit rich at high power settings, to running at peak at the power setting at 10,000'. This is usually about 1350 F on the EGT. |
#3
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Dean, check out this pps. And as others have said in other "leaning"
threads, check out John Deakin's articles on avweb. http://www.avweb.com/other/Leaning.pps Without an electronic engine monitor in our Aztec, I usually lean to 75-100 ROP using the EGT and sacrifice some fuel. My primary goal is to keep our CHT below 400 and the oil temp below 200, using cowl flaps as necessary Jim .. |
#4
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Dean,
absolute values of EGT are irrelevant with respect to leaning. Completely and totally so. What is relevant is the relation to peak EGT you are at, regardless of what the absolute value for peak is. Thus, when you have set cruise power, you lean until the EGT indication peaks and then falls again. That is your peak setting. Then, under consideration of what the POH says and what people like John Deakin say, either continue operating at peak (or lean of it, if your engine will do that) or enrichen to 100 to 150 rich of peak, that is, until the EGT falls from peak by that amount of degrees. Again, absolute value is irrelevant. Your engine is carburetted, so it will probably not run lean-of-peak without considerable roughness. Also, you should aggressively lean during taxi on the ground. You cannot harm the engine at all by leaning at taxi power settings. Lean at taxi power until the RPM just rises a little bit. If you lean further, the engine will stumble or quit. That's where you want to be. Now, should you forget to enrichen again for take-off (or even the mag check), the engine will stumble or quit since you have leaned it so aggressively. This prevents you from taking off leaned accidentally. -- Thomas Borchert (EDDH) |
#5
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Doug,
Now, for ALL operations, lean to that EGT Why? This is usually about 1350 F on the EGT. Why is that number relevant? -- Thomas Borchert (EDDH) |
#6
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Thanks for the information. I'm already leaning on the ground quite
aggesively as i've been told the O-540 plugs foul really easily with the very rich mixture the Aztec is set-up for full rich. One last question (sorry for the ignorance) but how do I know that that particular EGT is the highest reading. i.e. is it taken off an individual exhaust outlet or further down the exhaust (i.e. common/averaged reading). Just wondering what the case is if the EGT is out, and you lean to an incorrect EGT figure? Dean |
#7
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Doug wrote: Take it up to 10,000'. Push the throttle and prop full forward. Lean to maximum rpm. No good. He has constant speed props. The rpm won't change until he pulls the mixture control all the way out. |
#8
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Just pull the side cowls and look to see where the probe is installed.
Jim "Dean" wrote in message oups.com... Thanks for the information. I'm already leaning on the ground quite aggesively as i've been told the O-540 plugs foul really easily with the very rich mixture the Aztec is set-up for full rich. One last question (sorry for the ignorance) but how do I know that that particular EGT is the highest reading. i.e. is it taken off an individual exhaust outlet or further down the exhaust (i.e. common/averaged reading). Just wondering what the case is if the EGT is out, and you lean to an incorrect EGT figure? Dean |
#9
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Works on my plane (a Husky with Constant Speed prop). The idea is that
at 10,000' you can lean all you want and it won't hurt anything, at full power for that altitude. Now, you will be rich of peak, just a little rich at 8000' full power, and so on down to Sealevel where you will be 150 or so rich of peak. Works great. You are leaned enough to be rich of peak and you don't even have to go to peak, at Sealevel (which can cause detonation), to find out where peak is. You will be leaned enough rich of peak to be safe, but not so rich as to waste fuel. |
#10
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Unfortunately, for a carb'd O-540 like that, having an EGT gauge isn't too
terribly useful for leaning in cruise. It *is* useful for progressive leaning during a long climb. That is, note the full-rich, sea-level, max-power takeoff EGT and lean during the climb to hold that (e.g. 1300). For cruise, however, you'd be better off ensuring running at 70% or less, and leaning as much as possible, all the while ensuring that CHT never goes above 375. If it does, enrichen so it doesn't. If over 75%, enrichen to that same "full-rich" EGT (e.g. 1300). Likely the O-540 will run with a few cylinders lean of peak, a few at peak, and a few richer than peak when leaned fully to roughness. That's as good as you can do... just keep the power at 70% or lower. flame suit activated -Cory Dean wrote: : On my first flight in the Aztec with a fellow pilot who was doing the : flying, he stated to lean using the EGT (a recently installed : Electronics International digital single probe device)to circa 1300 and : no higher than 1350. : The aircraft does not have a CHT. : I am totally new to operating larger engines like the O-540 (no fuel : injection here) and want to ensure I dont damage anything. I hear a lot : of talk and hearsay about LOP/ROP leaning procedures. : Like most owners, I want to operate my aircraft efficiently, but not to : the detriment of engine reliability. : Any advice is welcome. : Regards, : Dean -- ************************************************** *********************** * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * ************************************************** *********************** |
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