Abstract: A method for designing a variable cycle gas turbine engine having a fan assembly with a maximum air flow there through and a maximum pressure ratio there across during operation at a fan speed and a plurality of variable pitch vanes, which method includes the steps of selecting a first operating point of the variable cycle gas turbine engine at a fan speed having about maximum air flow through the fan assembly at a pressure ratio substantially less than maximum pressure ratio and selecting a second operating point of the variable cycle gas turbine engine at about the fan speed, wherein the second operating point has about the maximum pressure ratio across the fan assembly at an air flow through the fan assembly substantially less than the maximum air flow. A reference point having a reference air flow through the fan assembly and a reference pressure ratio across the fan assembly is selected.

Abstract: A variable cycle gas turbine engine has, in axial flow serial relationship, a fan assembly, a core engine, and an exhaust assembly. The core engine includes a compressor, a combustor, a high pressure turbine and a first shaft interconnecting the compressor and the high pressure turbine. The fan assembly is connected to a low pressure turbine by a second shaft which is coaxial with the first shaft. The fan assembly includes a plurality of variable pitch inlet guide vanes, variable pitch stator vanes, and variable pitch outlet guide vanes, the pitch of which are adjusted to regulate the airflow through the gas turbine engine and the pressure ratio across the fan assembly as controlled by the exhaust assembly.

Abstract: An aircraft bypass turbofan engine subassembly for ground deceleration (e.g., thrust reversal). A fan nacelle has a through passageway connecting its inner exterior surface and outer exterior surface. A passageway end is located on the inner exterior surface aft of the aft-most row of fan rotor blades. A row of pivotable fan outlet guide vanes is located radially between the fan and core nacelles and longitudinally aft of the flow splitter and the passageway end. Apparatus is provided to pivot the vanes to block passage of bypass air and to open the passageway for ground deceleration.

Abstract: A method of operating an aircraft bypass turbofan engine having variable fan outlet guide vanes. In a first embodiment, an engine out condition is sensed, fan rotor speed is repeatedly measured, and vane pitch is adjusted to a predetermined value as a function of the fan rotor speed to generally maximize airflow through the vanes during the engine out condition. In a second embodiment, vane pitch is adjusted to a preselected value as a function of fan rotor speed to generally minimize engine noise during a noise reduction mode of engine operation.