An example embodiment of a turbine engine assembly includes a low spool including a low spool accessory drive gear driven by a low rotor shaft, a high spool including a high spool accessory drive gear driven by a high rotor shaft concentric around a portion of the low rotor shaft, and a differential gear assembly adapted to offtake power from rotation of one or both of the low spool and the high spool to drive one or more accessory loads. The differential gear assembly includes a differential bullgear and one or more idler gears each including a plurality of teeth meshed with the low spool accessory drive gear and the high spool accessory drive gear, and a bearing surface. The differential bull gear includes a plurality of teeth and a corresponding at least one bearing surface engaging with the bearing surface of each of the one or more idler gears. The plurality of teeth are adapted to mesh with an accessory drive system to transfer the power offtake and drive the one or more accessory loads.

A turbomachine engine including a high-pressure compressor, a high-pressure turbine, a combustion chamber in flow communication with the high-pressure compressor and the high-pressure turbine, and a power turbine in flow communication with the high-pressure turbine. At least one of the high-pressure compressor, the high-pressure turbine, and the power turbine comprises a ceramic matrix composite (CMC) material. The turbomachine engine includes a low-pressure shaft coupled to the power turbine and characterized by a midshaft rating (MSR) between two hundred (ft/sec).sup.1/2 and three hundred (ft/sec).sup.1/2. The low-pressure shaft has a redline speed between fifty and two hundred fifty feet per second (ft/sec). The turbomachine engine is configured to operate up to the redline speed without passing through a critical speed associated with a first-order bending mode of the low-pressure shaft.

A turbomachine engine including a high-pressure compressor, a high-pressure turbine, a combustion chamber in flow communication with the high-pressure compressor and the high-pressure turbine, and a power turbine in flow communication with the high-pressure turbine. At least one of the high-pressure compressor, the high-pressure turbine, and the power turbine comprises a ceramic matrix composite (CMC) material. The turbomachine engine includes a low-pressure shaft coupled to the power turbine and characterized by a midshaft rating (MSR) between two hundred (ft/sec).sup.1/2 and three hundred (ft/sec).sup.1/2. The low-pressure shaft has a redline speed between fifty and two hundred fifty feet per second (ft/sec). The turbomachine engine is configured to operate up to the redline speed without passing through a critical speed associated with a first-order bending mode of the low-pressure shaft.

A turbomachine engine includes a fan section having a fan shaft, and a core engine having one or more compressor sections, one or more turbine sections that includes a power turbine, and a combustion chamber in flow communication with the compressor sections and turbine sections. The turbomachine engine includes a low-speed shaft coupled to the power turbine and having a midshaft that extends from a forward bearing to an aft bearing. The low-speed shaft is characterized by a midshaft rating (MSR) between two hundred (ft/sec).sup.½ and three hundred (ft/sec).sup.½. The low-speed shaft has a redline speed between fifty and two hundred fifty feet per second (ft/sec). The turbomachine engine includes a gearbox assembly that couples the fan shaft to the low-speed shaft and characterized by a gearbox assembly mode less than 95% of a midshaft mode of the midshaft or greater than 105% of the midshaft mode.

A turbomachine engine includes a fan section having a fan shaft, and a core engine having one or more compressor sections, one or more turbine sections that includes a power turbine, and a combustion chamber in flow communication with the compressor sections and turbine sections. The turbomachine engine includes a low-speed shaft coupled to the power turbine and having a midshaft that extends from a forward bearing to an aft bearing. The low-speed shaft is characterized by a midshaft rating (MSR) between two hundred (ft/sec).sup.½ and three hundred (ft/sec).sup.½. The low-speed shaft has a redline speed between fifty and two hundred fifty feet per second (ft/sec). The turbomachine engine includes a gearbox assembly that couples the fan shaft to the low-speed shaft and characterized by a gearbox assembly mode less than 95% of a midshaft mode of the midshaft or greater than 105% of the midshaft mode.

In an embodiment, a gas turbine system is provided. The gas turbine system may include a supplementary air system and a flow diffuser configured to receive compressed air from the supplementary air system. The gas turbine system further comprises a gas turbine compressor downstream the flow diffuser, a combustor downstream the gas turbine compressor, a turbine downstream the combustor, and a turbine haft. The turbine shaft comprises a thrust bearing and a clutch. When the gas turbine system is operating, the gas turbine compressor does not consume electricity.

In an embodiment, a gas turbine system is provided. The gas turbine system may include a supplementary air system and a flow diffuser configured to receive compressed air from the supplementary air system. The gas turbine system further comprises a gas turbine compressor downstream the flow diffuser, a combustor downstream the gas turbine compressor, a turbine downstream the combustor, and a turbine haft. The turbine shaft comprises a thrust bearing and a clutch. When the gas turbine system is operating, the gas turbine compressor does not consume electricity.

The present disclosure relates to gearboxes for aircraft gas turbine engines, in particular to arrangements for journal bearings such gearboxes, and to related methods of operating such gearboxes and gas turbine engines. Example embodiments include a gearbox for an aircraft gas turbine engine, the gearbox comprising: a sun gear; a plurality of planet gears surrounding and engaged with the sun gear; and a ring gear surrounding and engaged with the plurality of planet gears, each of the plurality of planet gears being rotatably mounted around a pin of a planet gear carrier with a journal bearing having an internal sliding surface on the planet gear and an external sliding surface on the pin.

The present disclosure relates to gearboxes for aircraft gas turbine engines, in particular to arrangements for journal bearings such gearboxes, and to related methods of operating such gearboxes and gas turbine engines. Example embodiments include a gearbox for an aircraft gas turbine engine, the gearbox comprising: a sun gear; a plurality of planet gears surrounding and engaged with the sun gear; and a ring gear surrounding and engaged with the plurality of planet gears, each of the plurality of planet gears being rotatably mounted around a pin of a planet gear carrier with a journal bearing having an internal sliding surface on the planet gear and an external sliding surface on the pin.

A method and system for diagnosing a condition of an air-breathing aircraft engine are described. The method comprises obtaining a sample of lubricating fluid from the engine, filtering the sample to obtain a plurality of particles from the lubricating fluid, obtaining chemical composition data for the plurality of particles, determining a quantity of volcanic ash in the lubricating fluid by considering each one of the particles as composed partially of volcanic ash and partially of at least one other material and determining a first percentage of surface area of the particles covered by the volcanic ash and a second percentage of the surface area of the particles covered by the at least one other material, the volcanic ash having associated thereto a predetermined chemical composition, and diagnosing a condition of the engine based on the quantity of volcanic ash found in the lubricating fluid.