The turbine engine is impossibly alluring. No thrashing pistons, grinding cams, clicking valves-just far fewer exquisitely balanced parts all whirring in the same direction. But turbines are expensive and they guzzle fuel, which means that with very few exceptions, they don’t work we’ll in small airplanes. One of those exceptions is O&N Aircrafts re-engining of the Cessna P210 and 210 with the Rolls Royce (formerly Allison) 250-B17F/2 turbine engine, a powerplant thats been around awhile and one that Rolls is trying to evolve into more GA applications with the advent of a new version, the RR500. Mooney expressed interest in that engine, but thus far, the project hasnt materialized and it may not for the same reasons that turbines have stumbled before: difficult-to-manage fuel specifics and small airframes with no place to put the fuel. Meanwhile, more than 100 of O&Ns Silver Eagle-modified 210s are flying and we recently visited the companys shop in Factoryville, Pennsylvania, to evaluate the mod and do a flight trial. No sugar coating here: The Silver Eagle, at $980,000 complete, is not a cheap mod. On the other hand, its superbly engineered, performs we’ll and has just enough range to make it practical. The 250 engine has proven reliable and relatively easy to maintain. In fact, given its weight and power output, it has significant advantages over the competing engine, Pratts PT6.
History
This mod is no latecomer, having been perking along since about 1992, when industry veteran Myron Olson made it a signature product of the O&N shop, whose history dates back to 1986. O&N is a general maintenance shop with expertise in the Cessna 210 and P210 models, but with a line of mods including extended-range fuel tanks, control modifications for Cessnas and nacelle wing tanks for Navajos and Senecas.
In order to make turboprop conversions work in light singles, the engine has to meet a narrow set of parameters with regard to weight and fuel consumption. There were only two practical choices, Pratt & Whitneys PT6 and the then-Allison 250, which eventually evolved into the 495-HP 250-B17F/2 when Rolls got hold of it.
For the Silver Eagle, its derated to 450 HP, but thats still a ton of thrust for an airplane that originally had a 310-HP Continental TSIO-520, which some owners complain was never quite up to the task of high-altitude pressurized flight.
The turbine engine was originally developed in the 1960s by Allison as a helicopter powerplant and it found a ready market for that purpose. Like the PT6, its a