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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Zenith's member Oliver Reik may be another source for information about AeroMomentum.  He's got one for his 750 STOL.

I watched his recent videos as well, and was disappointed to hear about the quality issues he's run into. It sounds like he got a bad engine from the start, but even after the issues and engine replacement, he still seems happy with the quality of engineering of the engine and gearbox. It sucks to hear that all the peripheral parts are low quality, as well as the lack of communication and support.

I still like the engines, and most new companies having growing pains. Hopefully, all of the FWF parts get ironed out and we have another solid engine option.

It sounds like he got a bad engine from the start ...

Could be, but it could also be it was a good engine that was "started badly!"  What I mean by that is that a builder receives a perfectly good engine, but then cooks it by not prepping it correctly for first start, not providing adequate cooling for a ground run, extensive ground runs in the wrong conditions ... you get the picture.  Didn't the builder in the referenced video make some sort of remark that seemed to imply that he had difficulties bleeding the cooling system?  Anyway, don't take this as criticism of the builder or speculation, but just to point out that it's easy to damage a brand new engine.

Hopefully Mark will chime-in.  He has occasionally participated in the forums and when the Engine Forums were initiated, all the engine vendors were personally invited to participate.



I spoke with Mark about this. There is much more to the story (as there usually is). Expect to see a direct response from him here before too long.

I bet there is more to the story. However, I have no skin in the game, and will not take sides. While I don't want the community to get spammed like Jan with Viking, I have heard more than a few times that Mark at Aeromomentum, is hard to get a response from, though I have not tried myself. I would love to see more participation in the community by Mark, or other AM reps.

Looking forward to hear from Mark on this case.  That said, when I'll be an my engine choice I will certainly come with a looong list of questions & requests... kind of like my post last year but much more enhanced lol.

Having the chance to work on the engine directly at the shop (owner-assist type) could be a game changer in the skills I could gain and without mentioning own confidence in working in a FF package and built.

Hopefully this forum will grow so we can all get a better sense and another option for out build!



Hopefully this forum will grow so we can all get a better sense and another option for out build!

I agree, Luc!  It is likely that every new engine will have some "growing pains" as it is introduced and adapted to various airframes.  We in the Zenith community are very fortunate to have so many different engine choices so that we can find what's best for each of us based on price, weight, performance, etc.  As one of our members said, "It's nice to have options!"  It would be so boring to be locked-in to only one engine! 


Andy did have some issues and I am very sorry for them.  The factory starters are more sensitive to the wiring and there are known solutions to this that are a little different from what most people are used to doing.  We now cover this more extensively in the manual to help others not have these issues.  We have also found that with smaller batteries like AGM and lithium, the alternator can be damaged due to solenoid arcing in the starter depending on how it is wired.  We now put more emphasis on this in the manual.

All of our peripheral parts are from ISO 9001 factories and have additional specific certifications.  The starter is ISO/TS 14001 ISO9001.  The fuel pumps are from a factory that is ISO9001-2015 and SGS certified and makes fuel pumps for Walbro.

On the first flight Andy's engine rapidly and massively overheated.  Most likely this was due to the cooling system having some air.  If there is air in the cooling system it can get trapped at the thermostat preventing heat transfer to the thermostat bulb and causing it to not open.  Purging the air was a little tricky.  We later provided Andy with a new expansion tank to make purging the air quicker and simpler but it was too late and the damage was done.

We offered to repair his engine under warranty at our factory.  Due to shipping costs he declined this offer.  We later offered a brand new long block for half price ($1500) and he accepted this offer.  Most of the cost that he incurred was due to shipping to his remote location.

I am sorry if someone has emailed me and not received a prompt reply.  I am fairly busy but try to answer every email and phone call I receive.  At times they are missed or misplaced so please do not hesitate to call or email again if needed.

Thanks for the response Mark, it's good to hear that your product is evolving as issues come up. I hope all the bugs can be worked out soon, and we can see a lot more of these flying.

I understand that venting air can be tricky.  It is in our Viking 130 as well, but we have a procedure that requires running the engine until the temperature is high enough to open the thermostat, and then we stop the engine to add more coolant.  This may be done several times.

Regarding the comment "If there is air in the cooling system it can get trapped at the thermostat preventing heat transfer to the thermostat bulb and causing it to not open."  If this was the case, seems to me that Andy would have seen high temperatures long before take-off.  

Do your thermostats have a jiggle pin, which allows air to vent through a closed thermostat?  

We also had that exact same procedure and it does work.  Our new expansion tank and method takes less effort.

There is a jiggle pin that should allow air to vent but they do not seem to be 100% effective in preventing the very rapid temperature rise if you go from cool (thermostat closed) to full power.  I know that some racers and airboaters remove the juggle pin and enlarge the hole a little and this can help.  Also aerated liquid is much less effective as a coolant but maybe sufficient for lower power ground running.  I was not personally there so it is hard to know for sure but from past experience and our conversations this is most likely.

We also removed our jiggle pin so that it would vent that much better.  Our use of Evans coolant is another reason we decided to remove the jiggle pin.  The higher viscosity of Evans' may restrict venting through the jiggle pin.  

Once the air is vented out, I don't see the thermostat as a cause for overheating, unless it is wrong thermostat or malfunctioning.  Did Andy test the thermostat?  

Also, did Andy first test fly without a cowl?  In my opinion, liquid cooled auto conversion engines should first be test flown without a cowl.


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