Systems and methods associated with electrical systems of aircraft are disclosed. A method disclosed herein comprises generating electricity using an electric generator operatively coupled to an engine of the aircraft, supplying the electricity generated using the electric generator to a baseline power bus; generating electricity using an electric starter generator operatively coupled to the engine; and supplying the electricity generated using the electric starter generator to a supplemental power bus independent from the baseline power bus.

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 turbine engine includes integrated electric machines in the compressor section and the turbine section to supplement power produced from fuel with electric power. The example compressor section includes a compressor electric motor that is coupled to a compressor generator. The example turbine section includes a turbine electric motor that is coupled to the geared architecture to supplement power driving the fan section. A turbine generator provides electric power to the turbine electric motor.

Gas turbine engine starter systems and associated methods. A gas turbine engine starter system includes an engine starter with a starter torque output configured to convey a starter torque to a gas turbine engine. An engine startup process includes a spool-up time interval in which the engine rotational speed increases to a speed within an engine starting speed envelope. During at least a portion of the spool-up time interval, the starter torque is less than a speed-dependent maximum torque value of the starter torque that the engine starter is configured to produce. A method of operating a gas turbine engine starter system includes operating an engine starter to accelerate the gas turbine engine such that the starter torque is less than a speed-dependent maximum torque value of the starter torque that the engine starter is configured to produce during at least a portion of a spool-up time interval.

An eductor for an auxiliary power unit with a gas turbine engine and a load compressor incorporates an eductor housing having an cooling airflow inlet and a turbine exhaust inlet opening fluidly connected through a primary plenum to an outlet opening. A splitter plate is positioned in the primary plenum fixing a flow stagnation point with respect to a wall of the primary plenum.

A hybrid electric gas turbine engine system includes a first compressor and an auxiliary compressor. The first compressor is configured to output first compressed air. The auxiliary compressor is configured to operate in parallel with the first compressor to output second compressed air. A controller is configured to selectively activate the first compressor or the auxiliary compressor based on an operating condition of the hybrid electric gas turbine engine system.

A gas turbine engine with a compressor supplying compressed air. A combustor receives the compressed air and fuel and generates a flow of combusted gas. A turbine receives a core flow of the combusted gas to rotate a turbine rotor. A turbine inlet nozzle directs the combusted gas to the turbine rotor. Vanes are disposed in the turbine inlet nozzle and rotate to vary a flow area through which the core flow passes. The vanes adjust a pressure ratio of the gas turbine engine to compensate for changing operational requirements of the gas turbine engine by rotating to positions matching the changing operational requirements.

An aircraft system includes a turbine engine having a compressor, a combustor having an inlet and an outlet, and a turbine having an inlet portion and an outlet portion. An auxiliary power unit (APU) is operatively connected to the turbine engine. The APU includes a compressor portion, a generator, and a turbine portion. The compressor portion is operatively connected to the turbine portion through the generator. A source of cryogenic fluid is operatively connected to the turbine engine and the APU. A heat exchange member includes an inlet section operatively connected to the source of cryogenic fluid, a first outlet section operatively connected to the turbine engine and a second outlet section operatively connected to the compressor portion.

A method and system for controlling fuel flow to an aircraft engine during start are provided. Following light-off, an actual value of at least one engine operating parameter is obtained. Based on a difference between the actual value and a target value, a first command is generated to cause fuel flow to be provided to the engine's combustor according to a computed fuel flow rate defined by a fuel schedule of the engine. When the computed fuel flow rate is within a fuel flow rate limit, the first command is output. Otherwise, a limiting factor is applied to the computed fuel flow rate to limit a reduction in fuel flow to the combustor and a limited fuel flow rate is obtained, and a second command is output to cause fuel flow to be provided to the combustor according to the limited fuel flow rate.

A disclosed drive assembly for an auxiliary power unit includes a first drive shaft driven by an auxiliary power unit, a second drive shaft driven by a first electric motor, a differential gear system including a ring gear driven by the second drive shaft, a and planet gears supported within a carrier attached to the ring gear. The first drive shaft and an output shaft are coupled to the planet gears and a generator is driven by the output shaft. The electric motor and the auxiliary power unit combine to drive the output shaft.