Van's Air Force
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RV15 Engine selection
- Thread starter Jeff B
- Start date
I'm sure someone(much smarter than me) on here can also add in the weight savings into this performance result. Isn't it around 100lbs? I figure around 6K' this engine and the 390 produce the same hp.
Alphalpha
Well Known Member
Because of radically different rpm operating ranges, a gearbox on one and very different torque curves you can’t compare the two systems using horsepower, especially in an airframe where power really only speaks to climb rate. The bottom line is until Van’s and Rotax work together to design a power plant for a specific airframe I’m staying with the engine Van’s and Lycoming did design to go together.
Utah-Jay
Well Known Member
I have flown quite a few 915 and 916 equipped aircraft, and love the engines, so nope - not underatign them at all. I flew the first Sling High Wings in South Africa with the 915, and it was (the factory admitted as well), a but underpowered. The 916 brought it up to reasonable performance levels, and make the airplane a nice cruiser. Its not really a rough-country airplane in my estimation, but they;’ve taken them into many places that folks woudl consider pretty wild…
Again - I am not anti-Rotax. I am PRO-Rotax … I love that we have options other than the standard Lycoming platform. But for the -15 to perform like folks are expecting, you’re going to want at least 200 HP. a 180 HP Rotax? Sure - but what’s the lifetime on that hot-rodded engine? I’ve flown with a few guys that have them, and they chose them for performance, not lifetime. (Oh, that Yamaha when its really turned up is awesome…but it gets trailered to STOL competitions sometimes…)
I can tell you how the -15 will perform on 180 HP BTW - we’ve ben flying our Dream Tundra (roughly the same size and weight of a -15) for ten years now on a 190 (ish) IO-360 (moderately high compression) and it does about 116 knots in reasonable cruise, 120 on a good day. Climbs fine for Idaho back country strips, and its gone in to probably 80% of them. But its not the 140 knot airplane that Van’s is shooting for in the -15.
Hanging a 100 lb lighter motor on the nose of any airplane sounds really great from a climb performance standpoint. But you’re going to have to extend the nose a LONG way to give you the right CG, and that creates yaw stability issues (ask Lockwood….), so now you have to add sail area behind the CG (generally with a dorsal fin) And that adds a touch of weight and drag….its all a compromise.
Yup - I am REALLY looking forward to Rotax engineering and building a true 200 HP engine that will last to a TBO of their standards (which are really high) …. But I am not sure it will be here in my flying lifetime….
That’s fine but if everyone decides to follow instead of lead, then there will be no progress.
The ones who choose to lead should be encouraged, not chastised.
Deltahawk latest spec sheet gives 335lb for all three versions … 180hp, 200hp, and 235hp. Last I spoke to them they said the newest version (and first to go into general production) has had 35lb removed from that which would give a weight of 300lb. Given full power is available up to 12‘000ft, that would seem to be an interesting option.
Alphalpha
Well Known Member
Interesting, mischaracterizing an open dialogue of ideas that are pro and con on a subject as “chastisement” is in fact the very definition of chastising… which also an instance of irony.
Actually, my comment was made in general; there are those here, and elsewhere, that routinely chastise people taking anything other than the established path.
My point was simply that without people willing to take that alternate path, progress stagnates. Those people, who choose to LEAD, even in the face of failure, are the ones who should be encouraged.
There is a difference between open dialogue and chastisement. Don’t believe me? Just do a search on EFII/SDS versus traditional….
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