Hey All,

First and foremost, still in my early stage of the 750 Cruzer built so have lots of time for engine choice; AM15 however really caught my eyes.  Did all the reading and videos I could find online... also posted a post here about a year ago, to my disappointment without much traction at all.  This may be being a flag already.

That said, please have a look at "Andys RV12 AM15" channel on YouTube... he posted a review this week about his experience with the AeroMomentum.  I must say (even if I don't want to) that this is either an "eye opener" or at least a "do you due diligence".

Any one here using the AM15 for aircraft, if yes flying it of still in staging process?

Something in me find this engine attractive; but the engine can be as good as it's being promoted however if the aux parts are not up to par with minimal-to-no support and also no full package and/or quality instructions what would I get into?  I think I'm pretty handy but gotta be realistic with my skills level... are we still way too early in the game for AM15 in aeronautics (for first time builders)?

Would like to hear from anyone or Mark about that YouTube review video.

Cheers and good luck to all!


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I do not remember for sure but I think Andy tested his thermostat and it tested good.  I think he replaced it anyway since he was not confident in the thermostat.  We have also seen many times where the thermostat tested good but others thought it must be the thermostat.  What we have found for sure is if you have air in the system the engine will overheat.  The actual method that air causes the overheating is speculation.

Andy did not first test fly without a cowling.  I also think that is a good idea to first test fly without a cowling and we have done so with out CH701. Some of our customers have also done so.  I am a little hesitant to make it a blanket recommendation since maybe some aircraft could have control-ability, stability or performance issues without a cowling.

How likely (or unlikely) is it that once the air has been properly purged from the cooling system, that air will later enter the system and cause a catastrophic failure. What might cause that to happen?

The system has a small pressurized tank, pressure cap and overflow bottle.  As the system gets warm the coolant expands and what is in the top of the tank is pushed into the overflow bottle.  If there was a little air it would get pushed first.  As the engine cools the valve in the cap opens to suck the coolant back from the bottom of the bottle.  The bottle is kept about half full.  This cycling will slowly purge the system and keep the system air free as long as there are no leaks.

If there is a leak, not only will it expel coolant but it will not suck the coolant back from the bottle.  That is why you check the coolant level before each flight just like you check the oil level.

I found it pretty funny Andy put the fuel pump switch by the trim. That has been a concern of mine and I think I will put in 2 guarded switches to test the pumps. Don’t want to bump a switch and become a glider during a critical time of flight. 

For contrast, I'm installing a Lyc 0-320 (150hp - regular car gas). Total weight FWF is about 320# - Lightweight components and wood prop. This is about the simplest and easiest engine install possible. Fewest parts, easiest fuel system, 2 mags, and carburetor. Zenith approved and engine mount available.

WHY?  dependability, proven, and most important: I had one laying around my shop looking for a home :)

Used mid-time engines are available quite reasonable all over the place, and maintenance  is easy, every mechanic knows them. Parts available everywhere.

Gas consumption (seems to be a Big concern) to me is a moot point as I use auto gas and burn 8 gal per hr at economy cruise. No big deal, only putting on less than 100 hours or so a year. Simplicity of mags is also a benefit.

With 100 extra pounds install weight over a "conversion"  on average, the extra Hp (say 20 hp)  will easily and with enthusiasm haul that 100 lbs around.

The Lyc O-320 is a great well proven engine and if you having one laying around it makes sense to use it.

I am not so sure mags with mechanical points and carbs are all that reliable and they do seem to require more maintenance.    Overhauls, parts, rebuilds and maintenance can get expensive.

Modern fuel injection, 4 valves/cylinder, high compression geared engines do have more complexity.  But they also have a lot more efficiency.  They not only are more fuel efficient for the power they produce but also produce more thrust for the power due to the slower turning prop having less drag.  So a Lycoming burning 8gph should have about the same delivered thrust as a 147 HP AM15h-HP burning 5.5gph.  At $2/gal gas this saves you about $5000 in 10 years.  At $4/gal this saves you about $10,000 in 10 years.  Over the life of the engine you save $20,000 at $4/gal.  Plus your range is increased by about 30%.  Your useful load is increased by 100 lbs at the longer range or by 145 lbs at the same range.  This is about a 25% increase in useful load at the same range.

Good to see the Mark responded to this thread.

I can't say much about the quality of the components installed on the engine yet, as we still haven't installed ours.

I can however attest that Mark always answered my calls and spent a LOT of time answering all of my many questions. He was also always willing to elaborate in great detail on topics of which we had different opinions, like the electrical system or whether to install a header tank or not.


I will have to second Oliver's comments. Mark has always answered my questions promptly and intelligently. We are getting close to engine first start, so I will posting updates as we put everything together.

I’ll third what Oliver and Tim have said about Mark, he’s always been very helpful to me. The only suggestion I would like to make is, it would be nice to have your install/maintenance manual and a service bulletin(or technical tips) section that would be kept current, on your website. For example, the new and improved method of the expansion tank install and drilling and tapping the induction system to make getting the air out of the system much easier. I have done this mod to my engine but wouldn’t have known about it if I hadn’t watched Andy’s video. There are a number of us installing your engine and getting information about updates/changes/improvements would be very helpful.

Just a thought!

Great suggestion.

Also, I didn't want to imply that Aeromomentum had issues with poor communication, I has just heard that criticism in the past, which may have been isolated incidences. It's good to hear that questions are getting answered promptly.

That is a great suggestion and we will add it to our web site.  Some is already available here:


Andy posted an update. Seems like he is happy now: https://youtu.be/Y60b4bFXUx0


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