A power transmission gearbox having at least one driving gear with spur teeth presenting a large radius. The gearbox includes at least one mechanical outlet drive system suitable for driving an accessory, the mechanical outlet drive system having a gear with face teeth referred to as an accessory pinion, the accessory pinion presenting a small radius (R2) lying orthogonally between each face tooth and its axis of rotation, the small radius (R2) being smaller than the large radius (R1).

A system and method for controlling an inlet door of an auxiliary power unit (APU) are provided. It is determined whether a condition to inhibit a start of the APU is present. If no condition to inhibit the start of the APU is present, a door-opening signal comprising instructions to cause the inlet door to be commanded to an open position in advance of a prospective command to start the APU is output. If the condition to inhibit the start of the APU is present, a door-closing signal comprising instructions to cause the inlet door to be commanded to a closed position is output.

There is provided a method and a system for controlling an inlet door of an auxiliary power unit provided on an aircraft. Input data indicative of whether the aircraft is on ground or airborne is received. If the aircraft is on ground, a first control signal comprising instructions to command the inlet door to a fully open position is output. If the aircraft is airborne, a second control signal comprising instructions to command the inlet door to a partially open position. When a current value of a rotational speed of the auxiliary power unit reaches a predetermined threshold indicative of an end of a start sequence of the auxiliary power unit, a third control signal comprising instructions to transition the inlet door from the partially open position to the fully open position is output.

The invention refers to an APU compartment, and a method for extinguishing a fire in an APU compartment. The APU compartment (1) comprises an APU (2), an exhaust (5), an aperture (7) providing a passage between the APU compartment (1) and the inside of the exhaust (5), and a fire detection system, wherein the APU compartment (1) of the invention is constructed as an air tight compartment, and additionally comprises a conduit (9) for providing external air to the APU compartment (1), a door (8) for closing the conduit (9) inlet, and a control unit (6) configured to close the door (8) when a fire is detected, such that when the door (8) is closed and the APU (2) is in operation, the air contained in the APU compartment (1) is sucked through the aperture (7) to be expelled out of the APU compartment (1) to extinguish the fire.

An air duct arrangement (58) for an aircraft (40). The arrangement (58) comprises an environmental control system (ECS) (50). The ECS (50) comprises an air inlet (60) arranged to ingest a low velocity portion of a boundary layer flow adjacent the aircraft fuselage (44), and to deliver a flow of air to an environmental control system air intake (66). The arrangement (58) further comprises an ejector (70) arranged to receive an ECS exhaust (76), and boundary layer air from an aft region of the aircraft (40), and to exhaust air to the ambient airstream at an aft portion of the aircraft (40).

The invention relates to an aircraft incorporating an enhanced power unit for generating electric, pneumatic and/or hydraulic power for the aircraft during all stages of the aircraft operation. The power unit (1) comprises: a heat engine (14) with a drive shaft (2) and a combustion gases exhaust (7). The power unit (1) also includes a Rankine cycle system (12) for recovering thermal energy from a heat source of the power unit (1) for the assistance of the heat engine (14). The heat source for the Rankine cycle system can be taken from the exhaust gases of the heat engine, from the oil coolant circuit of the heat engine or from the output of a compressor driven by the heat engine. Preferably, the aircraft cabin air is reused as a source of oxygen for the combustion. The invention reduces bleed air extraction from the aircraft main engines thereby reducing fuel consumption.

A method and apparatus are presented. An active flow control system comprises a flow control valve, a manifold, and a temperature control system. The flow control valve is configured to control a flow of air into the manifold. The manifold is operatively connected to a number of actuators. The temperature control system is configured to heat at least a portion of the flow of air.

A method and system for operating an inlet door of an auxiliary power unit are provided. A control signal comprising at least one inlet door command is output. In response to the at least one inlet door command, at least one feedback signal is received and compared to the at least one inlet door command. If the at least one received feedback signal matches the at least one expected feedback signal, operation of the auxiliary power unit is allowed. Otherwise, operation of the auxiliary power unit is inhibited.

A method and apparatus are presented. An active flow control system comprises a flow control valve, a manifold, and a temperature control system. The flow control valve is configured to control a flow of air into the manifold. The manifold is operatively connected to a number of actuators. The temperature control system is configured to heat at least a portion of the flow of air.

Herein provided are methods and systems for detecting blockage of an inlet of gas turbine engine. An oil temperature measurement of the engine and an ambient temperature measurement is obtained. The oil temperature measurement is compared to a threshold based on the ambient temperature measurement. Blockage of the inlet of the engine is detected when the oil temperature measurement exceeds the threshold.