Ultra-bypass (or so-called unducted fan or propfan) engines were developed in the mid-80s. The initial design of MD90 utilized this type of engine instead of conventional turbofan. Boeing had also come up with a twin engine T-tail model called 7J7 that uses ultra-high bypass fans.
But some how airlines were not interested. MD90 switched back to conventional turbofan and Boeing killed the 7J7 project.
Supposing higher the bypass ratio is, more economical and efficient the engines are to operate. Ultra-high bypass engines have a bypass ratio several times higher than the current high-bypass turbofans. Why weren't the airlines interested in such a design? Does anyone know?
Raytheon's Starship executive jets uses unducted fan but that didn't sell very good either.
But some how airlines were not interested. MD90 switched back to conventional turbofan and Boeing killed the 7J7 project.
Supposing higher the bypass ratio is, more economical and efficient the engines are to operate. Ultra-high bypass engines have a bypass ratio several times higher than the current high-bypass turbofans. Why weren't the airlines interested in such a design? Does anyone know?
Raytheon's Starship executive jets uses unducted fan but that didn't sell very good either.
Comment