Abstract: A gas turbine engine including a low speed spool including a low pressure compressor, a low speed output gear disposed on the low speed spool, a high speed spool including a high pressure compressor, a high speed output gear disposed on the high speed spool, a first tower shaft engaged to the low speed spool at the low speed output gear, a second tower shaft engaged to the high speed spool at the high speed output gear, and a superposition gearbox. The gas turbine engine further including a ring gear shaft coupled to drive the ring gear, a ring gear shaft drive gear. A low speed spool drive train gear ratio is between 0.5 to 2.0, the low speed spool drive train gear ratio being measured from the low speed output gear to the ring gear shaft drive gear.

Abstract: A filtration system is disclosed. In various embodiments, the filtration system includes a fine mesh filter configured for disposition within a chamber and defining a first volume, the first volume in fluid communication with a main exit conduit; and a coarse mesh filter configured for disposition within the chamber and at least partially surrounding the fine mesh filter, the coarse mesh filter and the fine mesh filter defining a second volume, the second volume in fluid communication with a first bypass valve, the coarse mesh filter and the chamber defining a third volume, the third volume in fluid communication with a second bypass valve.

Abstract: A disclosed turbofan engine includes a first spool including a first turbine; a second spool including a second turbine disposed axially forward of the first turbine, a first tower shaft engaged to the first spool, a second tower shaft engaged to the second spool, and a superposition gearbox including a sun gear, a plurality of intermediate gears engaged to the sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears. The second tower shaft is engaged to drive the sun gear. A starter is selectively coupled to the sun gear through a starter clutch. A first clutch selectively couples the first tower shaft to the ring gear and a second clutch selectively couples the ring gear to a static structure of the engine. An accessory gearbox is driven by an output of the superposition gearbox.

Abstract: A turbofan engine includes a first spool including a first turbine, a second spool including a second turbine, and a fan. A fan drive gear system drives the fan. A first tower shaft engages the first spool, and a second tower shaft engages the second spool. A superposition gear system includes intermediate gears engaged to the sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears. The first tower shaft drives the sun gear. A main oil pump is driven by the carrier and supplies oil to the fan drive gear system. An auxiliary oil pump supplies oil to the fan drive gear system and is driven by a ring gear shaft coupled to the ring gear. A shuttle valve selectively allows oil to be supplied to the fan drive gear system by one of the main oil pump and the auxiliary oil pump.

Abstract: A seal assembly for a gas turbine engine according to an example of the present disclosure includes, among other things, a rotatable shaft defining a longitudinal axis, and a bearing housing extending along the longitudinal axis to define a bearing compartment. The bearing housing has a first seal land defined along an inner diameter of the bearing housing, a seal carrier fixedly attached to an outer periphery of the shaft, and a seal member extending outwardly from the seal carrier. The seal member defines a plurality of helical grooves facing radially outward to establish a first sealing relationship with the first seal land, and each one of the helical grooves has a major component extending in an axial direction relative to the longitudinal axis. A method of sealing for a gas turbine engine is also disclosed.

Abstract: A turbofan engine includes a first spool including a first turbine, a second spool including a second turbine, and a fan. A fan drive gear system drives the fan. A first tower shaft engages the first spool, and a second tower shaft engages the second spool. A superposition gear system includes intermediate gears engaged to the sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears. The first tower shaft drives the sun gear. A main oil pump is driven by the carrier and supplies oil to the fan drive gear system. An auxiliary oil pump supplies oil to the fan drive gear system and is driven by a ring gear shaft coupled to the ring gear. A shuttle valve selectively allows oil to be supplied to the fan drive gear system by one of the main oil pump and the auxiliary oil pump.

Abstract: A turbofan engine according to an exemplary embodiment of this disclosure includes, among other possible things, a first spool including a first turbine; a second spool including a second turbine disposed axially forward of the first turbine; a first tower shaft engaged to the first spool; a second tower shaft engaged to the second spool; a superposition gearbox including a sun gear, a plurality of intermediate gears engaged to the sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears, wherein the second tower shaft is engaged to drive the sun gear; a first clutch for selectively coupling the first tower shaft to the ring gear; a second clutch for selectively coupling the sun gear to the carrier; and an accessory gearbox driven by an output of the superposition gearbox.

Abstract: A gas turbine engine includes a low speed input shaft connected to a low speed tower shaft, in turn connected to a lower speed spool and a high speed input connected to a high speed tower shaft, in turn connected to a higher speed spool. The low speed input shaft is connected to drive a first plurality of accessories. The high speed input shaft is connected to drive a second plurality of accessories. The high speed tower shaft and the low speed tower shaft are coaxial and rotate about a common axis. An angle drive is provided into the low speed input shaft and the high speed input shaft, respectively.

Abstract: A turbofan engine includes a first spool including a first turbine and a second spool including a second turbine. A superposition gear system includes a plurality of intermediate gears engaged to a sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears. A second tower shaft is engaged to drive the sun gear. A starter is selectively coupled to the sun gear through a starter clutch. A first electric motor and a second electric motor are coupled to the superposition gear system and are operable to input power into a corresponding one of the first and second spools.

Abstract: A gas turbine engine includes a core engine, a fan section, and a superposition gearbox that includes a sun gear. A plurality of intermediate gears are engaged to the sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears. The core engine drives the sun gear and an output from the superposition gearbox driving the fan section. An electric motor is coupled to a portion of the superposition gearbox to provide a portion of power to drive the fan section through the superposition gearbox.

Abstract: A turbofan engine includes a first spool including a first turbine; a second spool including a second turbine disposed axially forward of the first turbine, a first tower shaft engaged to the first spool, a second tower shaft engaged to the second spool and an accessory gearbox supporting a plurality of accessory components and a superposition gear system disposed within the accessory gearbox. The superposition gear system includes a plurality of intermediate gears engaged to the sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears. The second tower shaft is engaged to drive the sun gear; a starter selectively coupled to the sun gear through a starter clutch; a first clutch for selectively coupling the first tower shaft to the ring gear; a second clutch for selectively coupling the ring gear to a static structure of the engine.

Abstract: A turbofan engine includes a first spool including a first turbine; a second spool including a second turbine disposed axially forward of the first turbine, a first tower shaft engaged to the first spool, a second tower shaft engaged to the second spool and an accessory gearbox supporting a plurality of accessory components and a superposition gear system disposed within the accessory gearbox. The superposition gear system includes a plurality of intermediate gears engaged to the sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears. The second tower shaft is engaged to drive the sun gear; a starter selectively coupled to the sun gear through a starter clutch; a first clutch for selectively coupling the first tower shaft to the ring gear; a second clutch for selectively coupling the ring gear to a static structure of the engine.

Abstract: A disclosed turbofan engine includes a first spool including a first turbine; a second spool including a second turbine disposed axially forward of the first turbine, a first tower shaft engaged to the first spool, a second tower shaft engaged to the second spool, and a superposition gearbox including a sun gear, a plurality of intermediate gears engaged to the sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears. The second tower shaft is engaged to drive the sun gear. A starter is selectively coupled to the sun gear through a starter clutch. A first clutch selectively couples the first tower shaft to the ring gear and a second clutch selectively couples the ring gear to a static structure of the engine. An accessory gearbox is driven by an output of the superposition gearbox.

Abstract: A turbofan engine according to an exemplary embodiment of this disclosure includes, among other possible things, a first spool including a first turbine; a second spool including a second turbine disposed axially forward of the first turbine; a first tower shaft engaged to the first spool; a second tower shaft engaged to the second spool; a superposition gearbox including a sun gear, a plurality of intermediate gears engaged to the sun gear and supported in a carrier and a ring gear circumscribing the intermediate gears, wherein the second tower shaft is engaged to drive the sun gear; a first clutch for selectively coupling the first tower shaft to the ring gear; a second clutch for selectively coupling the sun gear to the carrier; and an accessory gearbox driven by an output of the superposition gearbox.

Abstract: A gas turbine engine includes a fan drive turbine driving a fan rotor through a main gear reduction. A primary lubricant system supplies lubricant to the main gear reduction. An auxiliary oil pump supplies oil to the main gear reduction. An auxiliary pump epicyclic gear train drives the auxiliary pump when the fan rotor is rotating in either direction. The main gear reduction is separate from the auxiliary pump epicyclic gear train.

Abstract: A machine has first and second members. A bearing has an inner race mounted to the second member and an outer race rotatable relative to the inner race about an axis. A ring holds the outer race. A radial spring extends radially between the ring and the first member. First and second damper rings extending radially between the ring and the first member at first and second axial sides of the radial spring. First and second damping chambers are radially between an outer diameter surface portion of the respective damper rings and an inner diameter surface portion of the first member.