Aero Momemtum AM20T for Bearhawk 5

[PilotDebug]

Came across this engine: https://aeromomentum.com/am20t-230hp-300hp/

Also came across this one where this is very little info: https://aerovolare.com/av43t-300hp-350-hp/

Thoughts??

[predragvasic]

At the risk of igniting yet another endless debate, I'll try to summarise the most common concerns with auto conversions in general, and the Aeromomentum in particular. The main issue is almost complete lack of track record.

There are numerous independent auto-conversions, dating back to the early days of VW bug engines, Subaru Legacy conversions, and there have recently emerged startups that buy low-mileage used auto engines from totalled cars, overhaul them, slap on a PSRU and sell it as an aircraft engine for far less than a comparable Lyco/Conti equivalent. The appeal is quite understandable, with the considerably lower acquisition price, usually lower total weight, ability to burn auto gas, and in some cases, lower fuel consumption.

Ron Wanttaja (of Kitplanes fame) compiles an up-to-date database of GA accidents, and according to his records, auto-conversions built by these companies (Eggenfeller, Viking, Aeromomentum, etc.) seem to have a very poor reliability track record, failing in flight at a disproportionately high rate. Now, people like Jan Eggenfeller will tell you that those engines failed because builder added a "modification" that the company did not certify or approve, but the argument is rather weak, since the failures often point to builder knowing very well what he was doing, and accident not having much to do with the modification.

The bottom line is, the E in E-AB represents the idea of experimenting, and there's nothing wrong with trying to save some money by installing an auto-conversion, as long as the builder is fully aware how much on his own he will likely be with such an engine. Not many A&Ps will feel comfortable doing any work on such an engine, if they are expected to sign off on it later. And to be fair, there ARE people who have been flying their auto conversions for decades without a single incident. The odds aren't all that favourable, though, that you won't ever have any issues.

[Have-Purple]

Couple of thoughts on this. I'm in Utah and my mission includes cross countries to Oklahoma, etc. with my wife. This means traversing rough terrain in high DA and precious cargo. I'm waiting on my Companion kit so my HP requirements aren't the same as yours and I have a lot more options in the 200hp range.

I did a hard look at the UL520 both turbo and non along with the aero momentum motors. I even considered viking/ other car conversations and the fancy turbo'd snowmobile engines Steve Henry has run. All of these engines put out serious power and have hp/lb numbers that are impressive. They all use "modern" efi engine controllers which is cool too. The advertised pricing is also attractive.

Some things to consider however..... Most of these engines make the big HP numbers with high rpms. This means using a gear reduction system. Rotax has a good system in this regard as does Teal Jenkins of Skytrax who makes gear boxes for the Yamaha engines. Other than these two companies, not much info is available on the other offerings. They might be great, but who knows?

I'm pretty handy with an engine, as I've done a V8/transmission/transfer case/axle swap in an old CJ jeep. The knowledge base was already out there and I wasn't doing a one off custom job. With any of the non traditional engines, you are committing to a custom install.

I almost pulled the trigger on a UL520T after conversing with the US based support located in Florida. They were going to make me a custom engine mount and help with all the little stuff. They genuinely seemed like they would be a good source for support after the sale. I was even close to securing the tech manual for the engine. Then it occurred to me that no one in Utah or anyplace I might fly knows anything about the UL motor or had access to parts other than the folks in Florida. This meant, I was my own first responder if my motor ever went tit's up. Sure, I could probably handle it, my knowledge is wide, but not very deep.

For me another consideration was that I wanted and adjustable/constant speed prop for the cross country flying. With these non lyco/cont motors it usually means using an electrically controlled prop which you can find, but you are very firmly in custom, unproven territory.

Ultimately I chose to go with an IO-390 via the nice folks at Bearhawk. I am already flying an "Experimental" airframe. I ultimately did not want to hassle with an experimental engine. If my mission was more akin to owning a rock crawler jeep that I can wrench on during the weekends and it doesn't matter if it goes down for maintenance, then sure, I might have gone all in on one of those 200 HP Apex yamahas.

Having said all that, I vote you get one of the new Deltahawk motors that are coming to Bearhawk. I suspect they will be well supported.

[TJ_Slice]

The UL520T is like a supermodel. From the outside, it looks perfect in every way, especially for the Companion. But when you dig deeper, maybe it isn't quite as attractive. I don't think I could really trust it yet. The 50 hour crankshaft failure on the Rans S-21, and then the Velocity crash don't give me the warm fuzzies about it. It sure looks good though.