Method of operating an aircraft bypass turbofan engine having variable fan outlet guide vanes

Claim 1

A method of operating an aircraft bypass turbofan engine, said engine including: a generally longitudinally extending axis extending forward and aft; a longitudinally aft-most row of generally radially outwardly extending fan rotor blades; a core nacelle disposed longitudinally aft of said blades and having a longitudinally forward end defining a flow splitter; a fan nacelle circumferentially surrounding said blades and at least a portion of said core nacelle; and a row of variable-pitch fan outlet guide vanes radially disposed between said fan and core nacelles and longitudinally disposed aft of said flow splitter, and said method comprising the steps of: (a) sensing an engine out condition for said engine; (b) repeatedly measuring fan rotor speed during said engine out condition; and (c) adjusting the pitch of said vanes to a predetermined value as a function of the current fan rotor speed measurement to generally maximize airflow through said vanes during said engine out condition.

Claim 2

A method of operating an aircraft bypass turbofan engine, said engine including: a generally longitudinally extending axis extending forward and aft; a longitudinally aft-most row of generally radially outwardly extending fan rotor blades; a core nacelle disposed longitudinally aft of said blades and having a longitudinally forward end defining a flow splitter; a fan nacelle circumferentially surrounding said blades and at least a portion of said core nacelle; and a row of variable-pitch fan outlet guide vanes radially disposed between said fan and core nacelles and longitudinally disposed aft of said flow splitter, and said method comprising the steps of: (a) sensing an engine out condition for said engine; (b) repeatedly measuring fan rotor speed during said engine out condition; and (c) adjusting the pitch of said vanes to a predetermined value as a function of the current fan rotor speed measurement to generally maximize airflow through said vanes during said engine out condition.

Claim 3

A method of operating an aircraft bypass turbofan engine, said engine including: a generally longitudinally extending axis extending forward and aft; a longitudinally aft-most row of generally radially outwardly extending fan rotor blades; a core nacelle disposed longitudinally aft of said blades and having a longitudinally forward end defining a flow splitter; a fan nacelle circumferentially surrounding said blades and at least a portion of said core nacelle; and a row of variable-pitch fan outlet guide vanes radially disposed between said fan and core nacelles and longitudinally disposed aft of said flow splitter, and said method comprising the steps of: (a) repeatedly measuring fan rotor speed; (b) adjusting the pitch of said vanes to a preselected value as a function of the current fan rotor speed measurement to generally minimize engine noise during a noise reduction mode of engine operation, and (c) adjusting the pitch of said vanes to a preestablished value as a function of the current fan rotor speed measurement during a mode of engine operation different from said noise reduction mode, wherein said preselected value is different from said preestablished value for an identical fan rotor speed measurement.

Claim 4

A method of operating an aircraft bypass turbofan engine, said engine including: a generally longitudinally extending axis extending forward and aft; a longitudinally aft-most row of generally radially outwardly extending fan rotor blades; a core nacelle disposed longitudinally aft of said blades and having a longitudinally forward end defining a flow splitter; a fan nacelle circumferentially surrounding said blades and at least a portion of said core nacelle; and a row of variable-pitch fan outlet guide vanes radially disposed between said fan and core nacelles and longitudinally disposed aft of said flow splitter, and said method comprising the steps of: (a) repeatedly measuring fan rotor speed; (b) adjusting the pitch of said vanes to a preselected value as a function of the current fan rotor speed measurement to generally minimize engine noise during a noise reduction mode of engine operation, and (c) adjusting the pitch of said vanes to a preestablished value as a function of the current fan rotor speed measurement during a mode of engine operation different from said noise reduction mode, wherein said preselected value is different from said preestablished value for an identical fan rotor speed measurement.