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Raven Honda Fit Engine Conversion(Pt. 2)
We're now on: 'How do we plan to optimize and streamline the auto engine to aircraft process' from our initial outline below.
Come New Years we enter our 19th year of converting auto engines for aircraft. After doing both Reduction Drive Kits and Complete FWF Engine packages and working with a lot of great builders of all different skill sets, my number one observation of the homebuilt aircraft build process is that if you as a first time builder were to do another build of the same aircraft- you could do it all over again in much less time. Problem is- you as a hobby builder won't, so everyone starts off with a steep learning curve and 'relearns' the same build out process over and over again. An example of the process would be like having a building contractor who hired only workers who had never built a house before and then just after they finally figured out how to build out the first one, he would let them go and start off with a new inexperienced crew for the next one- go figure.
Differences in cowling, cooling, fuel delivery, weight and balance, exhaust, mounting, wiring, and the legion of other details needing to be completed (and done right) add to the complexity of the task for each different aircraft design or kit. Only when you hit the "80% done - only 80% left to go" builder's wall in terms of the overall project and its complexity do you really understand the scale of difficulty of an owner-built aircraft project.
Add one more element to the mix, the bane of all designers, which is the "need" that some of us have to make 'small' changes and 'improvements' to the original design. In terms of engine packages this can come in the form of a much larger propeller, custom gear ratio, new and untested cooling system, a cowling that looks racier but negatively affects cooling air flow, just wanting to 'bolt on' a turbo for high altitude power, etc. Generally speaking I would have to say that aviation is one arena where following precisely in the footsteps of those who have gone before us (at least until we know from experience "why they did what they did") is most important.
In the airframe department companies have streamlined the build process by using CNC routing to cut and pre-punch all the aluminum sheet metal components, now offer pre-welded motor mounts and landing gear assemblies, and even have builders groups where people can learn directly from other builders experience with a particular airframe. Some of this has carried over into the alternative engine arena, but IMO it has still not been fully optimized. We are still penciling in the factors that would best allow our company to produce our product at the lowest possible cost and optimize the build process.
The other factor that really dampens the streamlining the auto engine to aircraft process itself is something that is often overlooked in today's Sport Pilot market. With the exception of the old school VW auto engine, all other modern auto engine candidates for conversion that are light enough for weight and balance with adequate HP will be 3 or 4 cylinder inline power plants. The only modern liquid cooled flat 4 design that will replace a Rotax® 912 series or small Lycoming®/Continental® under the cowl is the Suburu whose weight and HP make it suitable for larger homebuilt aircraft only. Perhaps if Suburu® made a lightweight newer version of its old 1.6L/1.8L we would be having a different conversation.
So, in order to follow the industry leader Rotax® and fit easily in the cowling of the vast majority of the Sport Pilot kit plane marketplace, an auto engine conversion company like ours has two choices.
The first one we pioneered 10 years ago now when we tested and proved up our adaptation of the Geo®/Suzuki® 1.3L 16 valve engine turned sideways and laid down flat for aircraft (our 'SideWinder' 1300SVS package) to fit in the same profile as the Rotax® 912. We have had great success with our proven layout and it is still in production. Viking also seems to be having success in doing their own version of this idea with the Honda® Fit and have adapted their engine package to a number of different aircraft to date. It is a proven workable solution to making a modern upright inline 4 cylinder engine that can compete with the Rotax® 912 and allows a fit (pun intended) into all sorts of aircraft cowling's and layouts. For a number of reasons, however, we did not choose this direction in our company's own development of the Honda® Jazz/Fit engine.
For our newest engine package (our Honda® Jazz/Fit 1500XV 115HP/ XVT 140+HP Turbo) we chose another development path which we will now refer to as option two. You could say that we simply woke up to the fact that all these years we have been working very hard to 'adapt' our engine package and layout to emulate as closely as possible the industry leader Rotax® in terms of fit and function at a fraction of the cost. What would happen if we really optimized our new Honda® engine design and played to this engines strengths- using it as much as possible as it was designed originally by Honda®? What if we start from the prop back to the firewall and optimize every detail of this complete engine package? What if we let go of the need to compete with Rotax® (or any other engine conversion company for that matter) and do what we do best? What would it look like to build a cutting edge FWF engine package using our already flight proven components
the lightest, most powerful, reliable, fuel efficient, and let's not forget affordable, product to date? And... keep it simple, quick build, and performance oriented.
More to come in Part 3.......
Raven ReDrives Inc.