My plane has an M337AK engine, which is very different from the typical Lycoming / Continental engines found in most Western-built GA types. From the pilot’s perspective the biggest difference is probably mixture control: it has an “auto-leanin” feature, which over-leans at altitude so you use the mixture control knob to enrichen the mixture there. The factory standard engine monitoring instrument has CHT (#5 cylinder), oil temperature, oil pressue and fuel pressure indications.
Of course the engine (and the plane) has its operation manual, and there is a considerable amount of knowledge among current and previous operators, but some topics are simply not really toched at all:
For most of their useful life, these engines have been operated in a highly regulated environment with no concessions for post TBO operation. OTOH, the overly conservative TBO recommendations have been extended multiple times (from 800/1000 h to 1600 h) throughout the production run of these engines.
Also they tended to be highly utilised (and running out of flight time based TBOs), while in private operation utilisation is much lower. Another problem is that actual operating experience is not really shared even between the different countries/language areas in Eastern Europe, further limiting the amount of correct info one could get.
I try to fly my plane once a week or at least once every two weeks (except for the worst part of winter), but I would like to know if I could improve the longevity of my engine by borrowing some techniques commonly applied for Western-built types. Anyone here with experience?
I think the fundamental difference between your engine and a US ‘flat’ engine is mechanical supercharging. Can you turn it on and off as per the brochure you linked? If so, it might be interesting to consider the effect, and advantages and disadvantages of running in either mode. The 6.3:1 compression ratio used on the supercharged engine is low, and that is worth thinking about too. In these ways (and also in having inverted cylinders) the M337AK seems to have more in common with a radial aircraft engine than a horizontally opposed engine.
In terms of non-invasive engine monitoring it might be useful to gather some data on CHT and fuel mixture distribution (EGT) between cylinders as a starting point. Oil analysis and Camguard are used on different kinds of engines, including non-aviation engines, so I don’t suppose there are major issues there.
I would to try flying a Zlin with the LOM engine, if only for the education and experience.
It’s also worth noting that TBO of the old Czech engines was stated for the operation with the Soviet bloc MS-20 and MK-22 oils, which are apparently not up to modern specs. I heard from an AN-2 pilot that switching from MS-20 to Aeroshell 120 (yes, 120, not 100) or Phillips X/C 25W60 in the ASh-62IR radial engine increased engine life by 50-100% in intense operations. On the other hand, if the aircraft was to be grounded for the winter, Aeroshell-filled engines required preservation but MS-20 filled ones could simply be left as is. Not sure about LOM engines, but I can ask – there must be old Czech pilots around here who remember operating on MS-20.
Silvaire wrote:
also in having inverted cylinders) the M337AK seems to have more in common with a radial aircraft engine than a horizontally opposed engine.
Why?
Shorrick_Mk2 wrote:
Why?
Engine driven mechanical supercharger with associated higher manifold pressure and lower compression ratio, and inverted cylinders leading to similar oil control and operational issues.
Silvaire wrote:
Can you turn it on and off as per the brochure you linked?
Yes.
If so, it might be interesting to consider the effect, and advantages and disadvantages of running in either mode.
Oh, yes. Actually then engine and plane POHs (and operating practice) are not in total agreement about the best mode, but I mainly use it in one of the following modes:
In terms of non-invasive engine monitoring it might be useful to gather some data on CHT and fuel mixture distribution (EGT) between cylinders as a starting point.
The research articles I linked basically discuss this. Not surprisingly, cylinders get hotter from front to back with the spread being relatively constant among different planes.
Oil analysis and Camguard are used on different kinds of engines, including non-aviation engines, so I don’t suppose there are major issues there.
Oil analysis: would the lack of baseline data not be a problem?
Camguard: is it never contraindicated?
I would to try flying a Zlin with the LOM engine, if only for the education and experience.
You’ll be my guest if you come to Hungary. :-)
Ultranomad wrote:
It’s also worth noting that TBO of the old Czech engines was stated for the operation with the Soviet bloc MS-20 and MK-22 oils, which are apparently not up to modern specs. I heard from an AN-2 pilot that switching from MS-20 to Aeroshell 120 (yes, 120, not 100) or Phillips X/C 25W60 in the ASh-62IR radial engine increased engine life by 50-100% in intense operations.
That’s very true. AeroShell W100 is the recommended oil for my engine in Central European climate and that is what I use. According to the logbooks the previous operator also used that oil for the majority of the engine’s life.
Not sure about LOM engines, but I can ask – there must be old Czech pilots around here who remember operating on MS-20.
I’d appreciate any info you might get.
Sorry I didn’t look at the links before posting, I was hurrying
Seems to me the supercharger would be quite useful for high altitude takeoffs, then you could disengage it and run full throttle MP in high altitude cruise, eliminating the mechanical losses of the supercharger. A turbo without the hot machinery…
My wife has a single Hungarian lady friend near Baja, you might see me coming a bit further to go flying some day while they are catching up 
@JnsV, I talked about it with an engineer who has been overhauling LOM engines since 1990. He said more or less the same I heard before, but with more specific information. Operating on Aeroshell, Total or ELF instead of MS-20 does indeed reduce engine wear a lot, and the accumulation of soot in the oil is much slower. However, MS-20 is a lot better than Aeroshell for preservation purposes – he saw the innards of an engine filled with MS-20 that had been sitting in storage for 20 years, and they looked immaculate. He also made an important point about oil viscosity: W100 is indeed the recommended grade for new or freshly overhauled engines, but older ones would benefit from somewhat thicker oil – “W110” (W100+W120 50:50) or maybe even neat W120.
I have just scanned and converted to PDF an operator’s manual for LOM engines (M332A/AK, M137A/AZ, M337A/AK). It’s 157 pages in English (not perfect, but fully understandable) and covers operation, inspections, maintenance, troubleshooting, storage/shipping, installation and preservation/depreservation. Whoever wants it, drop me a line. It’s a 13 MB file.
Ultranomad wrote:
He also made an important point about oil viscosity: W100 is indeed the recommended grade for new or freshly overhauled engines, but older ones would benefit from somewhat thicker oil – “W110” (W100+W120 50:50) or maybe even neat W120.
This is an interesting suggestion. I will have my annual maintenance done in a few weeks and I will discuss this with my mechanic.
I have just scanned and converted to PDF an operator’s manual for LOM engines (M332A/AK, M137A/AZ, M337A/AK). It’s 157 pages in English (not perfect, but fully understandable) and covers operation, inspections, maintenance, troubleshooting, storage/shipping, installation and preservation/depreservation. Whoever wants it, drop me a line. It’s a 13 MB file.
@Ultranomad, PM sent.
