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Don’t use EGT as a leaning reference!

Says Mike Busch in this article here Obsessed with EGT

Nothing really new in the article, but still a very good one IMHO

Interested parties, and there are quite a few when I stop at some places, usually ask the same questions:

  • what is it? A Vans RV-6.9i
  • uh? Officially a -6, but outfitted with the tail feathers of the -8, the engine mount/landing gear/engine cowling/canopy of the -7, and it’s the intercontinental version
  • did you built it yourself? Nope, but I bought it myself
  • what’s the engine in it? Last time I checked it was an uncertified Lycoming O-360, 180hp, carbed, with dual electronic ignition
  • how fast does it fly? Well, depends how much gas I wanna waste, or how much money I wanna spend, but I could high speed cruise at a TAS of 170kts. But since I enjoy flying in itself, and love to crown the act with efficiency, I usually cruise at Carson speed or slightly higher since it also is my Va. This results in low power and low RPM settings, and a fuel burn of slightly less than 21l/h for a TAS of 130kts

Back to the title of the thread… and always a good subject for hangar talk, what is your leaning technique?

Same as Mike Busch, I don’t look at the EGTs. Different than Mike Busch, I don’t look at the CHTs neither. Same as Mike Busch, I look at the final fuel flow figure.
Now, and contrary to what a lot of people think, of the two straight options to increase an engine’s efficiency, namely injection (vs carburettor) and electronic ignition (vs magnetos), the electronic ignition wins by a substantial margin (and yes, the top option is an electronic injection such as an SDS system + an electronic ignition). But I digress…
The major tools one can use on a ship he has some experience with, are one’s butts, and one’s ears
On the airplane described above, the mixture lever is pulled to an indexed position, and then slowly more, until a net power loss is felt, a slight increase in roughness and accompanying vibrations occurs, and the engine tone has changed. Then, a very slight push of the mixture will get rid of the symptoms, but for the power which will still be slightly lower. And the final verification follows with a read of the FF. Easy peasy

A more scientific method is leaning using an AFR (Air Fuel Ratio) meter, and I know quite a few people have been experimenting with such devices in the homebuilt world.
IIRC @eurogaguest1980 was doing some testing with such a device, any feedback?

Dan
ain't the Destination, but the Journey
LSZF, Switzerland

Playing the devil advocate, how do you know you are not ROP50 without EGT? didMike Busch say it’s “the worst place, because I want your engine to live long and prosper”

Last Edited by Ibra at 24 Jan 22:43
Paris/Essex, France/UK, United Kingdom

Dan wrote:

Back to the title of the thread… and always a good subject for hangar talk, what is your leaning technique?

……What the flight manual says to do, which is commonly for more recently manufactured airplanes, to refer to the EGT!

Mr. Busch has made a name for himself over the decades, generally in a favourable way, but suggesting away from following the airplane manufacturer’s approved procedures is a less than great position to advocate in my opinion….

Home runway, in central Ontario, Canada

Rather than using the airplane manufacturers’ recommendations, I would use the engine manfacturer as the go-to expert. (Different to cars and motorcycles, airplane manufacturers are not engine experts, but depend on the three established players there)
And Lycoming’s recommendation for leaning (shortened) pull back the mixture lever until the engine runs rough, then enrichen a little so it runs smooth again For my IO540 that comes very close to Mike’s method.

Last Edited by ch.ess at 25 Jan 06:36
...
EDM_, Germany

how do you know you are not ROP50 without EGT?

Because I used to quickly have a look at the EGT dropping from peak when first learning about my motor. Now I don’t even use it anymore, and the fuel flow is confirmation as it could not be that low if ROP.

Last Edited by Dan at 25 Jan 07:47
Dan
ain't the Destination, but the Journey
LSZF, Switzerland

Now I don’t even use it anymore, and the fuel flow is confirmation as it could not be that low if ROP

If you know required fuel flow that delivers 50%-60% power it’s easy to judge LOP based on that low fuel flow (it won’t matter where you set mixture if you set throttle & rpm with max 60%)

You still need to know if fuel flow is accurate but it’s part of “you now know your aircraft” and you know how far to pull the red thing

On new aircraft, you will need EGT and FF to do it and confirm it, still an art not science: most of the time it does not matter how you lean if engine is not stressed when it naturally runs smoothly with low fuel (most of them do), you will still get load of opinions on how to get there

You should get zero thermal & mechanical stress with zero fuel flow, a good starting point

Last Edited by Ibra at 25 Jan 08:12
Paris/Essex, France/UK, United Kingdom

Pilot_DAR wrote:

Mr. Busch has made a name for himself over the decades, generally in a favourable way, but suggesting away from following the airplane manufacturer’s approved procedures is a less than great position to advocate in my opinion….

Not sure he is advocating away from the manufacturer’s (airplane or engine) procedure, but more of inferring a different procedure.
Last century, most aircraft had very little engine instrumentation. When I went to the US to rent some “cheap”, no doubt thanks to the exchange rate and low cost of gas, complex airplane to crisscross the continent, those were mostly equipped with a single EGT indicator, some of them with the luxury of cylinder selection. Also the vast majority of people were taught to lean 50 ROP, and no leaning below 5’000ft. No oversquare operation, leaded fuel requirement, and further myths helped fuel (pun intended) a non-economical and wasteful use of aero engines.

Now I’m not saying disregard what the engine’s manufacturer say, the more so if your pride and joy is still under warranty… but I think that a reframing of antiquated procedures, the availability of precise engine instrumentation, and an associated understanding of how an engine operates, the Red Box range being a perfect example, helps operating our airplanes greener and with more efficiency.

Dan
ain't the Destination, but the Journey
LSZF, Switzerland

Ibra wrote:

you will still get load of opinions on how to get there

Absolutely. Line up 1’000 pilots on the subject, and you’ll get 1’001 opinions

Dan
ain't the Destination, but the Journey
LSZF, Switzerland

ch.ess wrote:

And Lycoming’s recommendation for leaning (shortened) pull back the mixture lever until the engine runs rough, then enrichen a little so it runs smooth again For my IO540 that comes very close to Mike’s method

I was using the same method for a long time until I noticed that it puts my engine very deep into LOP territory. Well past optimal BSFC

Dan wrote:

A more scientific method is leaning using an AFR (Air Fuel Ratio) meter, and I know quite a few people have been experimenting with such devices in the homebuilt world.

Lambda sensor integrated with electronically controlled fuel injection would be the ultimate solution. AFAIK SDS are already testing such devices

Poland

Ibra wrote:

You still need to know if fuel flow is accurate but it’s part of “you now know your aircraft”

Absolutely. And know your fuel flows and power tables. It is frightening how many people don’t care.

When I first got my airplane (O360 carburated) I was told to fly 25Sqare for climb and afterwards 23Square for cruise. Nobody bothered much about other settings.

While the 25Square power reduction after take off may have some benefit in noise abatement, it has long been put to bed as a myth to be good for the engine unless specifically limited by the manufacturer or given as a procedure in the AFM.

It is also remarkable that older AFM’s don’t have tables organized by % power or even give you specific data for Best Power, Best Economy in a reasonable way. In the end, people either simply fly without power setting tables or use “memory settings”. Which most definitly is not the most efficient way to fly.

As for mixing, the procedure mentioned by Mike Bush and Dan here was what I was taught as well when starting out on a lowly but lovely C150. Worked well then, works with the Mooney too. Actually, pretty much that is also written in many older AFMs.

LSZH, Switzerland
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