Turbofan engine including a fan actuation system

A turbofan engine for an aircraft, the turbofan engine comprising:

• a fan having a plurality of fan blades coupled to a fan shaft having one or more fan bearings, each of the plurality of fan blades being rotatable about a pitch axis and extending from a fan hub;
• a nacelle that circumferentially surrounds the fan;
• and
• a fan actuation system disposed within the fan hub and including one or more actuators for rotating the plurality of fan blades about the pitch axis and one or more radial thrust bearings, wherein the fan actuation system is characterized by a fan actuation system length envelope in a range of 8.5 to 13, the fan actuation system length envelope being given by:
• N
• FB
• ×
• D
• FT
• L
• AXIAL
• ×
• (
• R
• TB
• N
• FB
• )
• wherein NFB is a number of the plurality of fan blades, DFT is a fan tip diameter of the plurality of fan blades, RTB is a thrust bearing radius of the one or more radial thrust bearings, and LAXIAL is an axial length from a fan hub tip of the fan hub to the one or more fan bearings, wherein LAXIAL is given by AFH+AFB, AFH being a fan hub axial length from the fan hub tip to the pitch axis of the plurality of fan blades and AFB being a fan bearing axial length from the pitch axis of the plurality of fan blades to the one or more fan bearings, AFH is in a range of 25 inches to 40 inches, and AFB is in a range of 17 inches to 20 inches.

A turbofan engine for an aircraft, the turbofan engine comprising:

• a fan having a plurality of fan blades coupled to a fan shaft having one or more fan bearings, the fan being an open fan, and each of the plurality of fan blades being rotatable about a pitch axis and extending from a fan hub;
• and
• a fan actuation system disposed within the fan hub and including one or more actuators for rotating the plurality of fan blades about the pitch axis and one or more radial thrust bearings, wherein the fan actuation system is characterized by a fan actuation system length envelope in a range of 8.5 to 24, the fan actuation system length envelope being given by:
• N
• FB
• ×
• D
• FT
• L
• AXIAL
• ×
• (
• R
• TB
• N
• FB
• )
• wherein NFB is a number of the plurality of fan blades, DFT is a fan tip diameter of the plurality of fan blades, RTB is a thrust bearing radius of the one or more radial thrust bearings, and LAXIAL is an axial length from a fan hub tip of the fan hub to the one or more fan bearings, and RTB is a thrust bearing radius of the one or more radial thrust bearings, wherein LAXIAL is given by AFH+AFB, AFH being a fan hub axial length from the fan hub tip to the pitch axis of the plurality of fan blades and AFB being a fan bearing axial length from the pitch axis of the plurality of fan blades to the one or more fan bearings, AFH is in a range of 25 inches to 75 inches, and AFB is in a range of 16 inches to 23 inches, and DFT is in a range of 120.0 inches to 180.0 inches.