A Different Airplane
There was some degree of risk involved with every one of the clean-sheet choices that the company made, but without a doubt the biggest gamble was Cessna’s selection of a new airplane engine from a brand-new manufacturer. The 1,900-pound-thrust Williams International/Rolls-Royce FJ44-1A was exactly what Cessna was looking for: a light, economical and small turbofan of approximately 2,000 pounds of thrust. At the time, there were no alternatives. To be fair, Williams wasn’t new to building turbofans, nor was the basic FJ44 design a new engine. The Michigan-based company had been building engines for the military for years. This might have been more reassuring except for the fact that Williams’ engines all wound up in cruise missiles. As long as the TBO was at least five hours, an observer quipped, everyone was happy. The involvement in the process of commercial engine manufacturing giant Rolls-Royce must have been a comfort. In fact, Rolls did much of the development on the high-pressure turbine, which was seen as a critical step in making the engine fuel-efficient and reliable enough for the manned aviation world.
With 1,900 pounds of thrust, the FJ44s sacrificed 600 total pounds of output compared with the 2,200-pound Pratt & Whitney JT15Ds. But they were substantially smaller in diameter than the Pratt & Whitney engines on the Citation, cutting down on drag. The FJ44s had better specific fuel consumption than the Pratts, and they were 14 percent lighter. To top it off, they were far less mechanically complex than the Pratt & Whitney engines. The FJ44 features, to name two noteworthy parts-saving components, a one-piece titanium fan that requires no internal cooling and a single fuel-slinger ring that feeds the combustion process instead of individual injectors. The Williams engine has about 70 percent fewer parts than the JT15D.