A gas turbine engine may include a high speed spool, a low speed spool, a first epicyclic gear system, and a second epicyclic gear system. Generally, the high speed spool mechanically connects a high pressure turbine to a high pressure compressor, and the low speed spool mechanically connects a low pressure turbine to at least one of a fan and a prop via the first epicyclic gear system and to a low pressure compressor via the second epicyclic gear system, according to various embodiments. The first epicyclic gear system and the second epicyclic gear system may include a common sun gear shaft.

A propeller control unit (PCU) has: a pitch angle actuator; a valve operable to selectively fluidly connect the pitch angle actuator with a source of oil for controlling pitch angles of blades of a propeller and with a drain line for draining oil out of the pitch angle actuator for feathering the blades; and a bypass line having an inlet hydraulically between the valve and an inlet of the drain line, the bypass line having an outlet hydraulically between the inlet of the drain line and an outlet of the drain line.

A sensor system includes a rotor antenna, a radio frequency (RF) sensor, a stator antenna, and one or more processors. The rotor antenna and the RF sensor are configured to be disposed on a shaft of a rotor assembly and are conductively connected to each other. The RF sensor generates measurement signals. The stator antenna is mounted to a stator member of the rotor assembly and positioned radially outward from the rotor antenna. The stator antenna is wirelessly connected to the rotor antenna across an air gap. The one or more processors are communicatively connected to the stator antenna and are configured to monitor one or more electrical characteristics of the measurement signals that are received by the stator antenna from the rotor antenna over time as the shaft rotates and to determine rotational speed of the shaft based on recurrent variations in the one or more electrical characteristics.

A carrier assembly for a planetary gear assembly includes a planet frame defining a central aperture therethrough, the central aperture defining a rotation axis, the planet frame configured to rotatably support a plurality of planet gears, and a carrier connected to the planet frame via a stud. At least one of a portion of the carrier proximate the stud and a portion of the stud between the carrier and the planet frame has a dimension reduction, such as a thickness reduction, therein.

A turboprop gas turbine engine mountable to an aircraft has an engine core and a gearbox driving a propeller, the engine core and the gearbox being enclosed within a nacelle. The propeller is located rearward of the gearbox and the engine core relative to a direction of travel of the aircraft. An air intake is disposed within the nacelle and formed to direct ambient air into the engine core. The air intake includes an air inlet duct, having a forward-facing intake inlet receiving the ambient air, with an upstream section and a downstream section. The upstream section is in fluid communication with the intake inlet and extends downstream from the intake inlet. The downstream section fluidly connects to and directs air from the upstream section into the engine air inlet. A second air outlet duct is located within the nacelle and directs air into an air-cooled-oil-cooler (ACOC).

A unshrouded vane assembly for an unducted propulsion system includes a plurality of vanes which have non-uniform characteristics configured to generate a desired vane exit swirl angle.

Provided are an exhaust duct, an exhaust duct assembly, and an aircraft using the exhaust duct. The exhaust duct has a structure that enables combustion gas to be diverged and discharged from an inlet end to a first outlet end and a second outlet end at respective sides of the exhaust duct. The exhaust duct includes a first housing including a first body forming an outer wall of the inlet end, and further includes second bodies respectively extending on respective sides from the first body and respectively forming the first outlet end and the second outlet end; a second housing spaced apart from the first body, forming an inner wall of the inlet end, and extending curvedly toward the second bodies; and a connection housing connecting the first housing to the second housing and including at least one recess portion recessed toward the inlet end.

An electronic control system (35) for a turbopropeller (2) having a gas turbine engine (20) and a propeller assembly (3) coupled to the gas turbine engine (20), the control system (35) having: a propeller control stage (35a), implementing a closed loop control for controlling operation of the propeller assembly (3) based on a scheduled propeller speed reference (Nr.sub.ref) and a propeller speed measure (Nr); a gas turbine control stage (35b), implementing a closed loop control for controlling operation of the gas turbine engine (20) based on a scheduled reference (Ngdot.sub.ref) and at least a feedback quantity. The control system (35) further envisages an auxiliary control stage (35c), coupling the propeller control stage (35a) and the gas turbine control stage (35b) and determining a limitation of the operation of the gas turbine engine (20), if a propeller speed overshoot is detected, with respect to the propeller speed reference (Nr.sub.ref).

An electrical generator is housed in an annular cavity between the casing and the propeller shaft of a turboprop, while imposing little or no additional space requirement and with lightweight ancillary equipment. The rotor of the generator is mounted on an autonomous shaft end. A flange of the outer casing is removable in order to access the generator and to enable its easy removal and remounting.

A multi-spool gas turbine engine comprises a low pressure (LP) spool and a high pressure (HP) spool independently rotatable about a central axis. The LP pressure spool has an LP compressor and an LP turbine. The HP spool has an HP turbine and an HP compressor. An accessory gear box (AGB) is drivingly connected to the HP spool. The LP compressor is disposed axially between the HP compressor and the AGB. A gear train drivingly couples the LP compressor to the LP turbine. The gear train is integrated to the AGB.