Jan_Olieslagers wrote:
Why is nobody offering a similar design, powered by a couple of Rotaxes?
Here you go:
I wondered why no one had yet mentioned the DoubleEnder yet, and it’s in the last post :-)
alioth wrote:
I wondered why no one had yet mentioned the DoubleEnder yet,
Wow, that’s one cool airplane! Check out the pic in the FAQs – awesome….. (I think the DoubelEnder is the one in the middle)
Well, it is a push pull, and it does use Rotaxen, so far so good – but it does not have the Skymaster’s twin tail boom. Worse, it is not a tourer, not at all. Worst of all, I heavily mistrust the upgrade of the 912’s to produce 130HP. There are already plenty of indications that the 912(ul)S, squeezing 100 HP out of the original 912 block designed to provide 80, is less reliable, and to little surprise. If somebody manages to force that same block to produce 130HP, more than 50% over the original figure, reliability and lifespan must unavoidably suffer. Neither should there be any need. For a 2500 lbs MGW plane, 2×100 HP ought to be ample. No tweaking of the 912S should be necessary.
NB to top it all, I was not over impressed with the STOL capabilities. It is always hard to judge on a movie, and we do not know at what altitude it was filmed, but my Z701 hangar neighbour needs much less take-off run. I think even my own Apollo Fox might do better.
edited to add [[but of course I will not shoot at the messengers. Thanks for the link! ]]
You can afford to push the power vs reliability of the engines a bit more when you have redundancy.
In terms of STOL performance, it probably has further room for development of the aerodynamics but the overall concept is sound and is innovative in a way that new designs rarely are these days.
ortac wrote:
You can afford to push the power vs reliability of the engines a bit more when you have redundancy.
Agreed as regards reliability, but when passing that amount of money I would be unhappy about compromising on lifetime. Those 912S go for over 15K€ from the factory. Needless to say, the tweaking will cost a good deal over that. I wonder how they do it: add a turbo? Rotax themselves did that to the original 912, to make it a 914, but never to the 912S. Increase rpm? 5800 rpm is a lot, already. And the faster the engine runs, the smaller the prop needs to be, reducing efficiency.
When you order one I am sure they will be happy to provide you with the option of standard spec engines! As you say, you will still have 200bhp. Or 100bhp if you have engine failure on take off over some hostile Alaskan terrain, which is still plenty.
The design has a certain “sci fi” look about it, but the tail boom shape looks a bit crude.
ortac wrote:
the tail boom shape looks a bit crude.
Nothing wrong there, for a bush plane!
ortac wrote:
In terms of STOL performance, it probably has further room for development
It is extremely heavy. Empty weight of 1500 lbs!!! That is the same as the MTOW of an RV-4 (905 empty and 180 HP). In comparison the A36 is 991 lbs and 200 HP. A Carbon Cub is 930 and 180 HP
It should trim off 500 lbs, and it would be OK.
Yep, when an A36 climbs after TO, it is vertical, fighter style! That’s really STOL.
I had the personal A36 of Yuriy Yakovlev, the head designer of Aeroprakt, in front of my plane for 6 years in the hangar.
