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.

A power management system for a multi engine rotorcraft having a main rotor system with a main rotor speed. The power management system includes a first engine that provides a first power input to the main rotor system. A second engine selectively provides a second power input to the main rotor system. The second engine has at least a zero power input state and a positive power input state. A power anticipation system is configured to provide the first engine with a power adjustment signal in anticipation of a power input state change of the second engine during flight. The power adjustment signal causes the first engine to adjust the first power input to maintain the main rotor speed within a predetermined rotor speed threshold range during the power input state change of the second engine.

Methods and systems for operating a rotorcraft comprising a plurality of engines are provided. A request to enter into an asymmetric operating regime (AOR), in which at least one active engine of the plurality of engines is operated in an active mode to provide motive power to the rotorcraft and at least one standby engine of the plurality of engines is operated in a standby mode to provide substantially no motive power, is obtained. Engine usage data for the plurality of engines, including at least one first engine and at least one second engine, is determined. Based on the engine usage data, one of the at least one first and second engines is operated as the at least one active engine for the AOR, and the other one of the at least one first and second engines is operated as the at least one standby engine for the AOR.

An air intake system for an aircraft, which is switchable between a performance mode and a filtered mode, includes a duct forming filtered air inlet slits. The air intake system also includes interconnected gills adjacent to the filtered air inlet slits. The gills are movable between various gill positions including a closed position substantially covering the filtered air inlet slits and an open position substantially exposing the filtered air inlet slits. The air intake system also includes an actuator configured to move the gills into the closed position in the performance mode and the open position in the filtered mode.

An air supply plenum for an engine, the plenum being disposed upstream of an air intake of the engine, the air intake being provided in a casing of the engine. The air supply plenum includes a first lateral wall and a second lateral wall which together form a conduit in which an air flow flows as the engine functions. Each lateral wall includes a step which forms a transverse recess relative to the direction of the air flow in the air supply plenum, such that an aerodynamic separation occurs in the step when the engine is operating.

A method for quickly stopping the propulsion rotor of a helicopter after landing, comprising, following a request for quickly stopping the engine by a helicopter pilot, the following steps managed by the control unit of the turbomachine: Detecting the absence of the thermal stabilization phase of the gas generator of at least one turbomachine, controlling an extinction of the combustion chamber of the gas generator of at least one turbomachine, maintaining the rotation of the gas generator of which the combustion chamber is extinguished by means of said at least one electrical machine to ventilate the gas generator and stopping the main rotor of the helicopter by means of a mechanical brake.

A method of assisting the piloting of an aircraft. A collective pitch margin of a main rotor is determined by applying a recursive algorithm using a main relationship that supplies said collective pitch margin at each current calculation instant as a function of the quotient of a limiting power margin divided by a denominator, the denominator being equal to the product of a first term multiplied by a second term, the first term being a function of the current collective pitch at said current calculation instant and of the collective pitch limit at a previous calculation instant prior to said current calculation instant, said second term being a function at least of a predetermined coefficient for reducing said power margin of the power plant.

A device and method for precise measurement of erosion of compressors, without removing an engine, and with easy positioning. A centrifugal compressor of a gas turbine with a radial air inlet includes an impeller including blades and a casing for an air stream to flow in the blades of the impeller. The casing, covered with an abradable coating, includes an annular elbow zone in a substantially median part. Marking depressions of predetermined depths, preferably in groups, are machined in the abradable coating of the zone. Examinations by endoscopy are successively performed to provide an image signal of the markers. Processing the endoscopic signal supplies a number of remaining markers and a criterion for decision on removing the engine is applied thereto. Erosion occurs in the elbow of the casing and evolution thereof may enable monitoring of erosion of other components of the compressor, in particular the blades of the impeller.

A gas turbine engine has a housing exposed to a high temperature environment. The housing has a circumferential wall extending around the engine centerline and circumscribing an oil cavity. The wall has a sealing interface at an inner diameter thereof, the sealing interface having a central axis offset from the engine centerline. A boss is formed on the wall on the offset side relative to the engine centerline and a probe is mounted to the boss. The probe projects into the oil cavity. The oil in the oil cavity thermally shields the probe from the high temperature environment.