A gas turbine engine includes a propulsor, a compressor comprising a compressor rotor, and a turbine comprising a turbine rotor fixedly mechanically coupled to the compressor rotor. The propulsor and the compressor are arranged in axial flow series. The turbine rotor is radially outward of the compressor rotor, and the direction of fluid flow through the turbine is generally opposite the direction of gas flow through the propulsor and the compressor.

A gas turbine engine includes a propulsor, a compressor comprising a compressor rotor, and a turbine comprising a turbine rotor fixedly mechanically coupled to the compressor rotor. The propulsor and the compressor are arranged in axial flow series. The turbine rotor is radially outward of the compressor rotor, and the direction of fluid flow through the turbine is generally opposite the direction of gas flow through the propulsor and the compressor.

A highly efficient gas turbine engine is provided. The fan of the gas turbine engine is driven from a turbine via a gearbox, such that the fan has a lower rotational speed than the driving turbine, thereby providing efficiency gains. The efficient fan system is mated to a core that has low cooling flow requirements and/or high temperature capability, and which may have particularly low mass for a given power.

A highly efficient gas turbine engine is provided. The fan of the gas turbine engine is driven from a turbine via a gearbox, such that the fan has a lower rotational speed than the driving turbine, thereby providing efficiency gains. The efficient fan system is mated to a core that has low cooling flow requirements and/or high temperature capability, and which may have particularly low mass for a given power.

A gas turbine engine includes a rotatable first shaft, a first disk connected to the first shaft, a second disk connected to the first shaft, a combustor radially outward from the first disk and the second disk, and a heat exchanger connected to the combustor aft of the second disk. The first disk includes a row of low pressure compressor blades and a row of high pressure turbine blades connected to a radially outer end of the row of low pressure compressor blades. The second disk includes a row of high pressure compressor blades and a row of low pressure turbine blades connected to a radially outer end of the row of high pressure compressor blades.

An hybrid aircraft power plant, has: a gas turbine engine having a high-pressure spool including a high-pressure compressor, a high-pressure turbine, and a high-pressure shaft drivingly engaging the high-pressure turbine to the high-pressure compressor, a low-pressure spool including a low-pressure compressor, a low-pressure turbine, and a low-pressure shaft drivingly engaging the low-pressure turbine to the low-pressure compressor; an electric motor drivingly engaged to the low-pressure shaft; and a torque-transmitting device operatively connected to the HP-shaft and having an engaged configuration in which the torque-transmitting device drivingly engages the electric motor to the high-pressure shaft and a disengaged configuration in which the torque-transmitting device disconnects the electric motor from the high-pressure shaft.

An hybrid aircraft power plant, has: a gas turbine engine having a high-pressure spool including a high-pressure compressor, a high-pressure turbine, and a high-pressure shaft drivingly engaging the high-pressure turbine to the high-pressure compressor, a low-pressure spool including a low-pressure compressor, a low-pressure turbine, and a low-pressure shaft drivingly engaging the low-pressure turbine to the low-pressure compressor; an electric motor drivingly engaged to the low-pressure shaft; and a torque-transmitting device operatively connected to the HP-shaft and having an engaged configuration in which the torque-transmitting device drivingly engages the electric motor to the high-pressure shaft and a disengaged configuration in which the torque-transmitting device disconnects the electric motor from the high-pressure shaft.

An aircraft gas turbine engine includes a fan system having a reverse traveling wave first flap mode, Fan RTW, and including a fan upstream of the engine core; a fan shaft; and a front engine structure to support the shaft and having a front engine structure nodding mode FSN including two modes at similar, but unequal, natural frequencies in orthogonal directions; and a gearbox. The engine includes a gearbox, and a gearbox output shaft to couple output of the gearbox to the fan shaft. An LP rotor system including the fan system and the gearbox output shaft has a first reverse whirl rotor dynamic mode, Rotor RW. A frequency margin of:

[00001]$\frac{\mathrm{the}\mathrm{frequency}\mathrm{difference}\mathrm{between}\mathrm{mode}\mathrm{FSN}\mathrm{and}\mathrm{the}\mathrm{highest}\mathrm{frequency}\mathrm{of}\mathrm{either}\mathrm{synchronous}\mathrm{Fan}\mathrm{RTW}\mathrm{or}\mathrm{synchronous}}{}$

An aircraft gas turbine engine includes a fan system having a reverse traveling wave first flap mode, Fan RTW, and including a fan upstream of the engine core; a fan shaft; and a front engine structure to support the shaft and having a front engine structure nodding mode FSN including two modes at similar, but unequal, natural frequencies in orthogonal directions; and a gearbox. The engine includes a gearbox, and a gearbox output shaft to couple output of the gearbox to the fan shaft. An LP rotor system including the fan system and the gearbox output shaft has a first reverse whirl rotor dynamic mode, Rotor RW. A frequency margin of: $\frac{\mathrm{the}\mathrm{frequency}\mathrm{difference}\mathrm{between}\mathrm{mode}\mathrm{FSN}\mathrm{and}\mathrm{the}\mathrm{highest}\mathrm{frequency}\mathrm{of}\mathrm{either}}{}$

An aircraft gas turbine engine includes a fan system having a reverse traveling wave first flap mode, Fan RTW, and including a fan upstream of the engine core; a fan shaft; and a front engine structure to support the shaft and having a front engine structure nodding mode FSN including two modes at similar, but unequal, natural frequencies in orthogonal directions; and a gearbox. The engine includes a gearbox, and a gearbox output shaft to couple output of the gearbox to the fan shaft. An LP rotor system including the fan system and the gearbox output shaft has a first reverse whirl rotor dynamic mode, Rotor RW. A frequency margin of: $\frac{\mathrm{the}\mathrm{frequency}\mathrm{difference}\mathrm{between}\mathrm{mode}\mathrm{FSN}\mathrm{and}\mathrm{the}\mathrm{highest}\mathrm{frequency}\mathrm{of}\mathrm{either}}{}$