Systems and method for filling a fuel manifold comprising at least a primary and a second manifold of a gas turbine engine are described. The method comprises providing fuel flow to the secondary manifold of the gas turbine engine, the secondary manifold being partly or completely empty; monitoring at least one engine operational parameter of the gas turbine engine as fuel fills the secondary manifold; and accelerating the engine when a transition threshold is reached, the transition threshold being associated with the engine operational parameter and indicative that fuel has reached the combustor.

There is described a method of operating a multi-engine system of an helicopter. The multi-engine system has a first turboshaft engine having a first shaft, a second turboshaft engine having a second shaft, a gearbox having a clutch system, and a range of rotation speeds defined as a placarded zone. The method generally has: rotating the first and second shafts at a flight rotation speed above the placarded zone when clutched to a load; decreasing a rotation speed of the first shaft from the flight rotation speed to a first idle rotation speed above the placarded zone; unclutching the first shaft from the load during the decreasing; and subsequently to the decreasing and the unclutching, simultaneously decreasing the rotation speeds of the first shaft and of the second shaft to a second idle rotation speed below the placarded zone, the simultaneously decreasing including clutching the first shaft to the load.

A device for driving an integrated generator from an accessories relay box of a turbomachine. The device includes first and second electric motors arranged to transfer electric power from one to the other, one or more controllers configured for controlling said electric motors, and an epicyclic reduction gear train. The gear train includes a first element intended to be coupled to the accessories relay box, a second element intended to be coupled to the generator, and a third element driven to rotate by said first electric motor. The control means are configured to modify the speed of rotation of the third element in such a way that the second element is driven to rotate at a constant speed.

In a fuel control system (10) for a gas turbine engine (1) having a gas generator (4) and a turbine (6) driven by the gas generator (4): a main fuel regulator (12) determines a demand (W.sub.fdem) of fuel flow (W.sub.f) to be introduced in the gas turbine engine (1), based on an input request (PLA); and a first limiter stage (14), operatively coupled to the main fuel regulator (12), causes an adjustment of the fuel flow (W.sub.f) based on engine safety operating limits. The first limiter stage (14) is provided with a Ngdot limiter (20) to cause an adjustment of the fuel flow (W.sub.f) when the gas generator speed rate of change (N.sub.gdot) is determined to overcome acceleration/deceleration scheduled safety limits; the Ngdot limiter (20) implements a predictor (23), to perform a prediction (W.sub.fdot) of the fuel flow rate of change (W.sub.fdot), or fuel flow (W.sub.f), allowing the gas generator speed rate of change (N.sub.gdot) to track a scheduled reference value (Ngdot.sub.ref).

The invention relates to an aircraft propulsion system, comprising a main transmission unit (12) and at least two turbojet engines connected to the main transmission unit (12), respectively a first turbojet engine (14a) and a second turbojet engine (14b), each turbojet engine comprising a free turbine (24a, 24b), characterized in that the first turbojet engine (14a) comprises a heat exchanger (30) configured to recover some of the thermal energy from the exhaust gas at the outlet of the free turbine, and in that the propulsion system comprises at least one computer (28a, 28b) configured to control the two turbojet engines and to limit the acceleration and the deceleration of the first turbojet engine (14a) when neither of the turbojet engines is broken down, in order to limit the reactor power transients at the heat exchanger (30).

A system and method for adaptively controlling a cooldown cycle of an auxiliary power unit (APU) that is operating and rotating at a rotational speed includes reducing the rotational speed of the APU to a predetermined cooldown speed magnitude that ensures combustor inlet temperature has reached a predetermined temperature value, determining, based on one or more of operational parameters of the APU, when a lean blowout of the APU is either imminent or has occurred, and when a lean blowout is imminent or has occurred, varying one or more parameters associated with the shutdown/cooldown cycle.

In a fuel control system (10) for a gas turbine engine (1) having a gas generator (4) and a turbine (6) driven by the gas generator (4): a main fuel regulator (12) determines a demand (W.sub.fdem) of fuel flow (W.sub.f) to be introduced in the gas turbine engine (1), based on an input request (PLA); and a first limiter stage (14), operatively coupled to the main fuel regulator (12), causes an adjustment of the fuel flow (W.sub.f) based on engine safety operating limits. The first limiter stage (14) is provided with a Ngdot limiter (20) to cause an adjustment of the fuel flow (W.sub.f) when the gas generator speed rate of change (N.sub.gdot) is determined to overcome acceleration/deceleration scheduled safety limits; the Ngdot limiter (20) implements a predictor (23), to perform a prediction (W.sub.fdot) of the fuel flow rate of change (W.sub.fdot), or fuel flow (W.sub.f), allowing the gas generator speed rate of change (N.sub.gdot) to track a scheduled reference value (Ngdot.sub.ref).

A system and method for adaptively controlling a cooldown cycle of an auxiliary power unit (APU) that is operating and rotating at a rotational speed includes reducing the rotational speed of the APU to a predetermined cooldown speed magnitude that ensures combustor inlet temperature has reached a predetermined temperature value, determining, based on one or more of operational parameters of the APU, when a lean blowout of the APU is either imminent or has occurred, and when a lean blowout is imminent or has occurred, varying one or more parameters associated with the shutdown/cooldown cycle.

A method for operating a gas turbine engine having a starter-electric generator driven by one of a plurality of shafts of the gas turbine engine is provided. The method includes determining a desired amount of thrust to be produced by the gas turbine engine, as well as a desired amount of electrical power to be generated by the starter-electric generator of the gas turbine engine. The method operates the gas turbine engine to produce the desired amount of thrust, while producing less than the desired amount of electrical power using the starter-electric generator. Producing less than the desired amount of electrical power using the starter-electric generator allows for the desired amount of thrust production, or allows for the desired amount of thrust production more quickly.

In a fuel control system (10) for a gas turbine engine (1) having a gas generator (4) and a turbine (6) driven by the gas generator (4): a main fuel regulator (12) determines a demand (W.sub.fdem) of fuel flow (W.sub.f) to be introduced in the gas turbine engine (1), based on an input request (PLA); and a first limiter stage (14), operatively coupled to the main fuel regulator (12), causes an adjustment of the fuel flow (W.sub.f) based on engine safety operating limits. The first limiter stage (14) is provided with a Ngdot limiter (20) to cause an adjustment of the fuel flow (W.sub.f) when the gas generator speed rate of change (N.sub.gdot) is determined to overcome acceleration/deceleration scheduled safety limits; the Ngdot limiter (20) implements a predictor (23), to perform a prediction (W.sub.fdot) of the fuel flow rate of change (W.sub.fdot), or fuel flow (W.sub.f), allowing the gas generator speed rate of change (N.sub.gdot) to track a scheduled reference value (Ngdot.sub.ref).