METHOD FOR SETTING A GEAR RATIO OF A FAN DRIVE GEAR SYSTEM OF A GAS TURBINE ENGINE

摘要

A gas turbine engine includes an engine centerline longitudinal axis and a fan section including a fan with fan blades and rotatable about the engine centerline longitudinal axis. A low corrected fan tip speed less than about 1400 ft/sec and the low corrected fan tip speed is an actual fan tip speed determined at an ambient temperature divided by [(Tram ° R)/(518.7° R)]0.5, where T represents the ambient temperature in degrees Rankine. A bypass ratio greater than about 11 and a speed reduction device having a gear system with a gear ratio. A low and high pressure turbine in communication with a first and second shaft, respectively. The first and second shafts are concentric and mounted via at least one of the bearing systems for rotation about the engine centerline longitudinal axis and the first shaft is in communication with the fan through the speed reduction device and the low pressure turbine includes four stages.