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Engine management / leaning / peak / lean of peak (merged)

Frankly, John Deakin and his people are folk to listen to. I certainly, do, I have known John online for more than two decades and he makes a heck of a lot of sense. So do the other folks at the outfit in the course.

I had a conversation with him a couple of years ago about LOP in carbureted engines. We did have a lot of spark plug fouling on our plane, so reading what was possible in injected engines I got kind of grumpy that it should not work on carburetted ones. One of John's associates came up with a method using leaning to the onset of roughness, then to apply a bit of carb heat until the engine runs smooth again and then lean again. Result is, at identical airspeed a flow of about 3-4 lph less. Works fine and we have never seen a foul plug since and also CHT is lower this way

I will try to visit one of his seminars once I have a passport to enter the US again... so far, I just could not be bothered with the hassle of US immigration anymore. But I reckon John's seminar would make it worthwile.

LSZH, Switzerland

I too am not sure I'd go to the USA unless I had a really pressing reason, due to the cockup from 2006 when a certain US flying school (which I never even visited) falsely registered me with the TSA as having trained there but not completed the training i.e. "trained to hijack a plane". I got a 3hr lock-up and interrogation in a detention centre last time, which is not fun if you have another flight to catch. I've not been able to sort this out because both the school and the TSA washed their hands of it.

I would never advise anybody to not get educated on engine management but equally I don't think the subject is rocket science and the reality of engine management is that it is very simple IF you have the instrumentation (and difficult - a bit of a guesswork - otherwise).

An EDM700 costs ( of the order of €1000 plus installation which for a SE is about 2 days' work and most of that is hacking metal and pulling wires through. Worth every penny.

Shoreham EGKA, United Kingdom

I see four "camps" on this issue:

Camp one = Don't care push all the knobs in and go, I rented it, someone else is paying the costs. Forget them.

Camp two = Likes to learn, morally would like to treat the plane the best, and save a bit of operating cost, but is not going to get carried away - or exceed approved operating limitations or instructions.

Camp three = Owns the plane, equips it well, and enjoys finessing performance, though with caution.

Camp four = Really going to go to the effort to economize hourly operation. LOP seems to be one attractive tool for camp four pilots.

I'm in camp two. I always lean, but just to ROP. Both my planes are carburetted, and with all cylinder engine monitors. I know that I cannot achieve the same mixture in each cylinder, so I err to the cautious side (ROP). I know I can afford the fuel. The annual cost of the fuel I waste is still less than even just my labour to re 'n re a cylinder.

I do respect that other operations, and aircraft types (injected in particular) are different, and I don't seek to be critical of other types of operations, when conducted within limitations, but I take the conservative path on this.

Home runway, in central Ontario, Canada

I take the conservative path on this.

Only that I have never seen anything showing that running Peak EGT below 75% BHP is risky, reckless, pushing the limits, not conservative or in any way worse than ROP. So when facing the choice between wasting fuel and not wasting it it's clear what I go for.

I think camp four includes people who can afford the fuel but think LOP is the right way to run the engine for longevity. LOP is scary and "not conservative" because we are all trained to be terrified of the mixture knob.

EGTK Oxford

I suspect a good part of the 'camps' is also defined by the type of aircraft engine operated. Carbureted tends to be in the traditional ROP to peak camp and most LOP guys fly more expensive injected engines in aircraft with more sophisticated engine instrumentation (and probably as owners/partners)

I can't really imagine fussing with a c152 trying for some perfect (but impossible to achieve) mixture using ear and single point CHT gauge, where as in my JPI instrumented TNIO-550, LOP is a far more sensible operating methodology than ROP.


Pilot DAR,

Your labour must be really expensive. I only fly 100 hours or so a year, but at 17gph ROP vs 14.5gph LOP (same power output) and 3 USD / litre, I would spend $3000 / year extra on fuel if running ROP.


The best line I have heard regarding mechanics that say that running LOP will damage the engine goes like this:

"The concert pianist doesn't ask the piano tuner for advice on how to play the piano."

When the mechanic starts paying for my fuel and the maintenance, I might reconsider their advice on engine mixture management.


Well, yes, I'm expensive, but my fuel burn is not. 100 hours per year at 20LPH, maybe saving 1-2LPH with very precise leaning. Gas for the 150 costs me $1.05 per litre, so I could save $200 or so. That won't cover the four or so hours to re 'n re a cylinder, let alone the cost to repair it.

If I were paying the cost of the gas for a Navajo or C310, I probably would have a different opinion, but then as said, different plane. Fortunately, when I'm flying those types, I'm not paying for the gas, and that cost is very minor to the project anyway.

Early in flying I was told that fuel is the cheapest coolant you can use. I'm not suggesting careless wasting, and absolutely pilots need to be trained to lean, but I don't mentor pilots to really worry about it, and if in doubt, err to ROP.

Home runway, in central Ontario, Canada

Your labour must be really expensive. I only fly 100 hours or so a year, but at 17gph ROP vs 14.5gph LOP (same power output) and 3 USD / litre, I would spend $3000 / year extra on fuel if running ROP.

My calculation for 50 hrs/year at under 75% power on an 0-320 with 1 gph saved would be 50 x $6.00/gallon = $300/year. Not worth worrying about one way or the other. Less than a day of take home pay.

Actually, in many cases, the cheapest coolant you can use is air. It is available for free, at least here in the US. LOP operation on my aircraft drops the CHT's by 20 degrees C.

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