Turbofan engine including a fan actuation system

A turbofan engine comprising:

• a fan having a plurality of fan blades coupled to a fan shaft, the fan being an open fan, and each of the plurality of fan blades being rotatable about a pitch axis;
• a turbo-engine having a core inlet and including a low-pressure shaft, wherein the turbofan engine has a longitudinal centerline axis, and the core inlet is annular about the longitudinal centerline axis;
• a gearbox assembly, the fan shaft that being coupled to the low-pressure shaft through the gearbox assembly, wherein the low-pressure shaft, the gearbox assembly, and the fan shaft are coaxial along the longitudinal centerline axis;
• and
• a fan actuation system including one or more actuators for rotating the plurality of fan blades about the pitch axis and one or more thrust bearings, wherein the fan actuation system is characterized by a fan actuation system envelope in a range of 660 to 1860, the fan actuation system envelope being given by:
• N
• F
• ⁢
• B
• ×
• D
• F
• ⁢
• T
• ×
• M
• cruise
• (
• R
• T
• ⁢
• B
• N
• F
• ⁢
• B
• )
• wherein NFB is a number of the plurality of fan blades in a range of ten to fourteen, DFT is a fan tip diameter of the plurality of fan blades in a range of 120.0 inches to 168.0 inches, Mcruise is a Mach number of the turbofan engine at cruise operating conditions, and RTB is a thrust bearing radius of the one or more thrust bearings in a range of 20 inches to 27 inches.