Wonder just how much of a benefit this conversion is? Sounds nice but with respect to useful load and speed how much better is it? Would require a lot more fuel, so the useful load might not be increased dramatically. Reliability and TBO are better, but your looking at 6 figures for overhaul.
This particular "Mark I" STC is an old one, utilizing a helicopter turboshaft engine driving, through a driveshaft, a unique and heavy transmission. Soloy has a much more recent STC that uses a more compact engine package that saves weight and provides additional operating capabilities, a much more practical design IMHO. Plus the wing tip fuel allows a gross weight increase. All in all, a practical airplane.
The turbine engine weight is about a third of the piston engine. Even tho the fuel burn for a given horsepower may be higher, unless flying maximum range, the additional fuel weight is not a problem. Later engine versions have improved economy. Plus the turbine is more aerodynamicaly efficient. Fuel burn per mile is close to a piston engine. A turbine is self-cooling so there is no cooling drag from air having to push past cylinders and cylinder heads. Fuel is lower priced. Still a pricey conversion. Have heard that the engine alone is about $420K.
There are benefits to turbine power that many do not recognize, such as: 1) engine reliability is superior to a piston engine; 2) in case of an accident the fuel is far less volatile; 3) cold weather operation (eg starting the engine at 20 below) is much simpler with a turbine; 4) there are many parts of the world where avgas cannot be obtained. And my favorite 5) just the raw power! Example, once I got a clearance from Olympia, WA to FL170. I was level at 170 exactly 10 minutes after receiving takeoff clearance.
