The turboshaft engine for a rotorcraft includes a low pressure spool having a low pressure compressor and a low pressure turbine section, and a high pressure spool having a high pressure compressor and a high pressure turbine section. The spools are independently rotatable relative to one another. The low pressure compressor section includes a mixed flow rotor. A set of variable guide vanes (VGVs) are discposed upstream of each of the low pressure and high pressure compressors, the VGVs being configured to be independently operable relative to one another.

A rotor assembly comprises a rotor having annular flange including a plurality of protrusions axisymmetrically disposed about the annular flange, each protrusion having a mounting aperture for selectively receiving a balancing feature, and a plurality of slots axisymmetrically disposed about the circumference of the annular flange between adjacent protrusions. Each slot has a pair of converging flat portions extending axially inwardly from an adjacent protrusion end, an inner flat portion at an inner end of each slot, and a pair of curved portions respectively joining each converging flat portion to the inner flat portion in each slot. Each slot has a depth at least as great as an adjacent mounting aperture depth extending normally from the adjacent protrusion end to a far end of the corresponding mounting aperture.

An aircraft propulsion system is disclosed and includes a first gas turbine engine including a first input shaft driving a first gear system, a first fan driven by the first gear system, a first generator supported on the first input shaft and a fan drive electric motor providing a drive input to the first fan, a second gas turbine engine including a second input shaft driving a second gear system, a second fan driven by the second gear system, a second generator supported on the second input shaft and a second fan drive electric motor providing a drive input to the second fan and a controller controlling power output from each of the first and second generators and directing the power output between each of the first and second fan drive electric motors.

A system includes a gas turbine engine of an aircraft, the gas turbine engine having a low speed spool, a high speed spool, and a combustor. The system also includes a low spool motor configured to augment rotational power of the low speed spool and a high spool motor configured to augment rotational power of the high speed spool. The system further includes a controller configured to cause fuel flow. The controller is configured to control a thrust response of the gas turbine engine to a thrust target between zero and a thrust level to move the aircraft during engine start and during engine idle. The controller is also configured to control the low spool motor to drive rotation of the low speed spool responsive to a thrust command while the controller does not command fuel flow to the combustor.

A rotor of a fluid machine includes a wheel with a plurality of blades. Furthermore, the rotor includes an inter-blade area defined circumferentially between a first blade and a second blade of the plurality of blades with respect to the axis of rotation. Moreover, the rotor includes a balancing mark on the wheel and within the inter-blade area. The balancing mark is elongate and has a first end and a second end. The first end and the second end are stepped axially into the inter-blade area. The balancing mark extends arcuately between the first end and the second end. The balancing mark has a depth that varies as the balancing mark extends arcuately between the first end and the second end. The balancing mark has a width that varies as the balancing mark extends arcuately between the first end and the second end.

A turboshaft engine for a rotorcraft includes a first spool and an independently rotatable second spool. The first spool includes a low pressure compressor, a first set of variable guide vanes disposed at an entry of the low pressure compressor, and a low pressure turbine drivingly engaged to the low pressure compressor. The second spool includes a high pressure compressor, a second set of variable guide vanes disposed at an entry of the high pressure compressor, the second set of variable guide vanes independently operable relative to the first set of variable guide vanes, and a high pressure turbine drivingly engaged to the high pressure compressor. One or both of the low pressure compressor and the high pressure compressor includes a mixed flow rotor.

The gas turbine engine for an aircraft includes at least a low pressure spool with a low pressure turbine shaft operatively connected to at least one turbine, the low pressure turbine shaft rotatable about an engine axis, and a low pressure compressor operatively connected to a low pressure compressor shaft that is independently rotatable relative to the low pressure turbine shaft. A differential gearbox has an input operatively connected to the low pressure turbine shaft, a first output and a second output, the first output of the differential gearbox operatively connected to the low pressure compressor shaft and the second output of the differential gearbox operatively connected to an output shaft of the gas turbine engine. The differential gearbox permits the output shaft, the low pressure compressor shaft and the low pressure turbine shaft to rotate at different speeds.

An air turbine starter that includes a housing. The housing can circumscribe a turbine coupled that is coupled to a gear train in a gear box via a drive shaft. A primary air flow path is defined between a primary inlet and a primary outlet. Air in the primary air flow path can flow into a secondary air flow path or rotate the turbine, that converts energy from the air flow to rotational mechanical energy. Air in the secondary air flow path can pass through at least a first cavity and first passage before rejoining the primary air flow or joining ambient air.

Method to operate a vacuum system comprising at least a first vacuum pump and a second vacuum pump wherein the first vacuum pump and the second vacuum pump are connectable to a vacuum chamber to maintain a set pressure inside the vacuum chamber. The first vacuum pump is a Variable Speed Drive pump wherein the first vacuum pump and the second vacuum pump are connected in series. The method comprises the steps of controlling the performance of the first vacuum pump and the performance of the first vacuum pump is controlled to be equal to or higher than the performance of the second vacuum pump while maintaining the set pressure in the vacuum chamber.

A rotating assembly for a gas turbine engine has a balancing ring mounted to a first rotating component having a rotating unbalance about an axis of rotation. The ring is clocked at a circumferential position about the axis to counteract the rotating unbalance. A spacer is axially abutted against the first rotating component to set an axial position of the first rotating component relative to a second rotating component. The balancing ring is locked against rotation relative to the first rotating component in its circumferential position by the dual use spacer.