After the Lancair there are a number of smaller production experimental aircraft to consider, but the only other one in my opinion would be closest to in cost and performance is the RV10. If you’re new to aviation (and some reading this may be), Vans Aircraft is one of the most popular (if not THE most popular) experimental aircraft supplier in the world. I attended a session at Oshkosh one year around Vans and the speaker stood up on the stage and said “Lets face it, the ‘experiment’ is over on the RV’s” And I don’t think I would disagree with him at all. For those of you who haven’t experienced the RV series of planes, they are very nice and have a fantastic pedigree. The RV10 is their only 4-place aircraft in the lineup. It quite often is mistaken at airports as a Cirrus and it is quite similar in many aspect. But how does it stack up against the SlingTsi?
For the rest of the information, the tradeoff is the RV-10 does have a little wider cabin, higher max cruise speed, and overall a bit more performance. What the RV-10 is though, is it is 600lbs heavier. Keep that in mind as that is going to come into play a bit later on in the discussion.
Price and Build Times
For me though, the build time line item - it is estimated to be 600 hours less to build a Tsi over the RV-10. This primarily has to do with the type of fasters in constructing the airplane. The RV-10 uses buck rivets whereas the Sling uses pulled rivets. This plays a huge factor in the build time. If you aren’t familiar with the differences (I wasn’t other than I drew assumptions based on the name), the buck rivet is where you take a rivet, place it in the rivet hole and use a metal plate on one side and a rivet gun to effectively “pound” the rivet into the hole. This is done through a rivet gun that makes a sound a bit like a machine gun as it molds the rivet into place. It’s actually quite fun to do if you haven’t tried it, but when we’re talking about thousands of rivets the noise can get a little old. I’m sure my neighbors will appreciate the choice of using pulled rivets. As for what a pulled rivet is - the logo for this blog is that of a pulled rivet. You insert the rivet into the hole and then use a rivet puller to extract the center post up and out. When you perform this extraction is pulls the remaining rivet into place. The overall noise generally is a very mild “pop” when the rivet releases.
At the end of the day, as per the chart above the RV-10 is the winner cost-wise, but considering it could add an additional year to my build time I’m not sure I’m that patient.
Given this breakdown and that the Rotax 915is is a turbocharged engine, the two engine performance levels start to converge as altitude is gained. The 915is as designed will maintain sea level performance up to 15,000 tp 16,000 feet (depending on the source of the information as the Sling Aircraft site indicates 16,000, the Rotax 915is wiki page indicates 15,000 feet). If we take the reduction in engine performance as the airplane climbs the SlingTsi with the Rotax 915 starts to overtake the airspeed of the RV-10. I recently found a YouTube video of an RV-10 climbing up to FL200 to show off performance running lean of peak showing a True Airspeed of 152kts with a direct 39kt tailwind. It seems to support the numbers as per the chart below.
There’s a vast wealth of information online on this topic. Van's Aircraft provides documentation on the loss of horsepower as altitude changes:
Garrett Advancing Motion - while there is no relation to myself and Garrett engines (which would be nice actually), they do have a discussion around turbocharging at elevation when it comes to cars in this article. Oddly enough I don’t live too far from Pikes Peak and can see it on a clear day. This reference is more supporting documentation for the delta differences between a naturally aspirated engine and a turbo engine.
The wiki links for both of the respective engines between the Rotax and the Lycoming power plants:
Rotax Engine Wiki https://en.wikipedia.org/wiki/Rotax_915_iS
Savvy Aviation has a couple of great discussions on the state of engines and turbo engines at https://youtu.be/p22FOawoTCM - Turbocharging Systems in which I grabbed this slide.
Overall though, on the surface the RV-10 certainly is a compelling airplane with the heritage of the platform, a bigger cabin and what appears to be a slightly less expensive build, however given the location I’m located, what the mission is and the build times I feel comfortable with the performance the Sling is going to offer when stacked up against the RV-10.
What are your thoughts? Am I missing something? It’s too late for me as I’m committed to building the Sling, but I’m always welcome to feedback to help not just my understanding, but also to share the most accurate information I can with other pilots.