Sunday, September 12, 2010

Considering an Alternative Engine

The wing kit is about to get delivered and so Van's charged my credit card with the outstanding amount. This black hole that was blown into my account made me open up my little spreadsheet to see again what else I will have to spend to finalize the RV-12 under LSA certification.
I'm not sure if I mentioned it here before, I certainly did in the Van's Aircraft Forum, but I'm not really happy with the avionics package that Van's chose for the -12. It might have been a nice set of electronics when they first developed it but this stuff is developing almost as quickly as computers (which they essentially are) and so by now there are much more capable alternatives on the market. I.e. a Dynon Skyview is much more attractive to me than the D180 Flightdek. Then I have the Garmin aera500 GPS that I use in my Rans S-12S and it is such a better unit than the dated Garmin 495 that I can not imagine why I should go back to it.
I'd also love to add essential backup gauges to the instrumentation in case of a complete electric failure and so on and so on.
Regardless of what these changes are that I am considering the unfortunate constraint with building to LSA certification is that any deviation from the plans and the certified SLSA prototype would require a written approval by Van's in order to be accepted by a DAR during inspection. Van's would have to certify (and be liable for) that a change you've made doesn't adversely affect the airworthiness of the airplane in comparison to the SLSA prototype. For smaller changes I could image that they do that, for a complete change in avionics they certainly wouldn't.
So the options you have as a builder at this point are pretty limited. It comes down to a digital decision. You either build to LSA standard, get the certification done and do all your changes after the certification which then are completely legal and do not change the LSA certification (isn't that kind of hard to understand?). Or you choose to deviate from the plans and even leave out complete sub kits and brew your own. In that case you cannot certify the plane as an ELSA but as an Experimental - Amateur Build or E-AB.
The difference is that you will have to prove to the FAA that you built the airplane according to the 51% rule, the majority of the plane must be amateur-built. So you need a detailed builder log and photos proving that you built the different stages. You also will be required to fly off significantly more hours before you're allowed to leave the test area and before you can bring a passenger with you. The standard for E-AB is 40 hours for Phase 1.
This all stands against the option to save a lot of money and/or to get a much better airplane.

So while I was considering these avionics options I now also see the option for saving a large amount of money which essentially means that I could get airborne with the -12 a whole lot sooner.
When I was researching airplanes to build and looking at my budget I was coming across Jan Eggenfellner's new LSA engine project called the Viking HF-110 engine. Back then when I was considering the Rans S-19 he was in the earlier development stages flying this engine on his Zodiac and making a lot of progress. This engine is a Honda engine as it is used in the Fit and Jazz models and produces 110hp continuous and has weight and size parameters that make it compatible to the Rotax 912S.
What makes this engine really interesting is that appears to run fine and reliable for quite a while now (yes, with Jan's prototype) and the price tag is about half of the 912S while the weight is in the area of 25lbs heavier than the 912S. Fuel consumption appears to be 5 gal./hr.
Well, back then I dropped the idea as the prototype was about 50lbs heavier than the Rotax and the S-19 already had (and still has) a weight problem so you were exceeding gross weight with two 190lbs humans and full tanks for traveling on board. And that was with the Rotax! So, I forgot about the engine a bit as I wanted to go LSA with the -12, but the money issue came back and so I checked on the status of the project and Jan seems to be coming along very quickly with this new engine. He showed it at Sun'n'Fun 2010 and also at this year's Oshkosh.
I've heard from Jan that two RV-12 builders are currently working with him to put the engine in and will soon be flying. The official delivery of the engine starts in December this year which means that by summer next year there should be some realistic feedback about the qualities of this engine available. And that is when I could make the decision to go for E-AB, do my own avionics and with an alternative engine.
So, I'm pretty excited about this possible new option while I am trying to sip the KoolAid very slowly and see if this engine can fulfill my reliability requirements.

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