Abstract: A multi-spool gas turbine engine comprises a low pressure (LP) spool and a high pressure (HP) spool independently rotatable about a central axis extending through an accessory gear box (AGB). The LP spool has an LP compressor, which is axially positioned between the HP compressor of the HP spool and the AGB. A tower shaft drivingly connects the HP spool to the AGB.

Abstract: A gas turbine engine has a first spool having a low pressure compressor section disposed forward of an air inlet along a direction of travel of the engine, and a low pressure turbine section disposed forward of the low pressure compressor section and drivingly engaged thereto. A second spool has a high pressure compressor section disposed forward of the low pressure compressor section, and a high pressure turbine section disposed forward of the high pressure compressor section and drivingly engaged thereto. The high pressure turbine section is disposed aft of the low pressure turbine section. An output drive shaft drivingly engages the low pressure turbine section and extends forwardly therefrom to drive a rotatable load. A method of operating a gas turbine engine is also discussed.

Abstract: A gas turbine engine including at least one high pressure turbine rotor and at least one high pressure compressor rotor drivingly engaged to a rotatable high pressure spool, a low pressure spool rotatable independently of the high pressure spool, at least one low pressure turbine rotor drivingly engaged to the low pressure spool, and a rotatable load drivingly engaged to the low pressure spool. A fixed rotational speed ratio is defined between rotational speeds of the at high pressure turbine and compressor rotors. A fixed rotational speed ratio is defined between rotational speeds of the low pressure turbine rotor(s) and of the low pressure spool. A low pressure compressor rotor is in driving engagement with the low pressure spool through a variable transmission which defines a variable rotational speed ratio between the rotational speeds of the low pressure spool and of the low pressure compressor rotor.

Abstract: A heat exchanger defines an annulus divided by a plurality of radial plates extending longitudinal along the annulus, into a plurality of channels. A first group of the channels form an oil passage and a second group of channels form a fuel passage. The channels in the respective first and second groups are circumferentially alternately positioned one to another, and heat transfer from the oil passage to the fuel passage takes place through the radial plates.

Abstract: A gas turbine engine with a transmission having a variable ratio is discussed. A first gear train is in driving engagement with the low pressure spool and has a first output gear. A second gear train is in driving engagement with the high pressure spool and has a second output gear spaced apart from the first output gear. A third gear train defines a driving engagement between the low pressure spool and the low pressure compressor rotor with a variable transmission ratio. A fourth gear train is in driving engagement with the first and second output gears, and in driving engagement with the third gear train to determine the transmission ratio. A method of adjusting a speed of a low pressure compressor rotor of a gas turbine engine is also discussed.

Abstract: A gas turbine engine with a transmission having a first rotatable member coupled to an engine spool, a second rotatable member coupled to a compressor rotor, and coupled rotatable members defining at least first and second alternate transmission paths between the first and second members. Each transmission path defines a different fixed transmission ratio of a rotational speed of the second member on a rotational speed of the first member.

Abstract: The described accessory drive system for a gas turbine engine includes a gearbox driving a plurality of accessories including a cabin air compressor to provide cabin air and an engine starter to start the gas turbine engine. An electrical power supply separate from a main electrical power supply of the gas turbine engine is electrically coupled to the accessories. A clutch selectively engages an output of the gas turbine engine to mechanically couple the output to the gearbox. The clutch operates between an electrical drive state where it disengages from the output and only the electrical power supply provides electrical power to the cabin air compressor and the engine starter, and a mechanical drive state where the clutch engages the output and the gearbox drives at least one of the accessories.

Abstract: A gas turbine engine with a transmission having a variable ratio is discussed. A first gear train is in driving engagement with the low pressure spool and has a first output gear. A second gear train is in driving engagement with the high pressure spool and has a second output gear spaced apart from the first output gear. A third gear train defines a driving engagement between the low pressure spool and the low pressure compressor rotor with a variable transmission ratio. A fourth gear train is in driving engagement with the first and second output gears, and in driving engagement with the third gear train to determine the transmission ratio. A method of adjusting a speed of a low pressure compressor rotor of a gas turbine engine is also discussed.

Abstract: A method of adjusting a rotational speed of the low pressure compressor rotor(s) of a gas turbine engine, including rotating the high pressure compressor rotor(s) with the high pressure turbine rotor(s) through the high pressure spool, rotating the low pressure turbine rotor(s) with a flow of exhaust gases from the high pressure turbine, rotating the low pressure spool with the low pressure turbine rotor(s), rotating a load of the engine with the low pressure spool, driving a rotation of the low pressure compressor rotor(s) with the low pressure spool through a variable transmission defining a variable transmission ratio between rotational speeds of the compressor rotor(s) and the low pressure spool, and adjusting the transmission ratio to obtain a desired rotational speed for the low pressure compressor rotor(s). A method of adjusting rotational speeds of a gas turbine engine and a gas turbine engine are also described.

Abstract: A gas turbine engine with a transmission having a first rotatable member coupled to an engine spool, a second rotatable member coupled to a compressor rotor, and coupled rotatable members defining at least first and second alternate transmission paths between the first and second members. Each transmission path defines a different fixed transmission ratio of a rotational speed of the second member on a rotational speed of the first member.

Abstract: A foil-fluid bearing assembly adapted for supporting a shaft within an outer bearing housing and is adapted for accommodating angular misalignment of the rotating shaft relative to the housing.

Abstract: A foil-fluid bearing assembly adapted for supporting a shaft within an outer bearing housing and is adapted for accommodating angular misalignment of the rotating shaft relative to the housing.

Abstract: A foil-fluid bearing assembly adapted for supporting a shaft within an outer bearing housing and is adapted for accommodating angular misalignment of the rotating shaft relative to the housing.

Abstract: A foil-fluid bearing assembly adapted for supporting a shaft within an outer bearing housing. The foil-fluid bearing assembly comprises a bearing sleeve having an outer surface and an inner circumferential surface diametrically sized to receive the shaft therewithin such that an annular clearance gap, radially defined between an outer surface of the shaft and the inner circumferential surface, is adapted for accommodating fluid therein and axially extends along a substantial portion of a length of the bearing sleeve, and has a foil element disposed therewithin. Compliant bearing supports between the outer surface of the bearing sleeve and the outer bearing housing, comprises at least two independent compliant support elements respectively having a first and a second modulus of elasticity, wherein the first modulus of elasticity is less than the second modulus of elasticity. Angular misalignment capability for the foil-fluid bearing is provided by the compliant support elements.

Abstract: A foil-fluid bearing assembly adapted for supporting a shaft within an outer bearing housing. The foil-fluid bearing assembly comprises a bearing sleeve having an outer surface and an inner circumferential surface diametrically sized to receive the shaft therewithin such that an annular clearance gap, radially defined between an outer surface of the shaft and the inner circumferential surface, is adapted for accommodating fluid therein and axially extends along a substantial portion of a length of the bearing sleeve, and has a foil element disposed therewithin. Compliant bearing supports between the outer surface of the bearing sleeve and the outer bearing housing, comprises at least two independent compliant support elements respectively having a first and a second modulus of elasticity, wherein the first modulus of elasticity is less than the second modulus of elasticity. Angular misalignment capability for the foil-fluid bearing is provided by the compliant support elements.

Abstract: A flexible tooth of a tilling device includes several flat "e" shaped blades mounted side by side, one end of the blades being attached to a cross member of the tilling implement, the other ends of the blades being attached to a downwardly extending arm that holds a replaceable tool. The flexible tooth allows the tool to move upward or sideways to circumvent obstacles buried in the ground. The flexible tooth may include a reinforcing blade mounted on the cross member and having an upper curved portion that contacts an upper inner portion of the "e" shaped blades after they have flexed a certain amount to impart greater rigidity to the flexible tooth. The reinforcing blade may also include a lower curved portion that contacts the downwardly extending arm to further increase the rigidity of the flexible tooth.