Methods and systems for operating an aircraft having two or more engines are described. The method comprises operating the two or more engines of the aircraft in an asymmetric operating regime, wherein a first of the engines is in an active mode to provide motive power to the aircraft and a second of the engines is in a standby mode to provide substantially no motive power to the aircraft, receiving a request to exit the asymmetric operating regime, the request having at least one parameter associated therewith, selecting one of a plurality of available exit protocols as a function of the at least one parameter, and applying the exit protocol by commanding the engines accordingly.

A hybrid engine includes a gas turbine engine having at least one compressor section and at least one turbine section operably coupled to a shaft. The hybrid engine includes an electric motor configured to augment rotational power of the shaft of the gas turbine engine. A controller is operable to monitor for a transient operation request of the hybrid engine, provide the transient operation request to one or more management systems of the hybrid engine to determine whether one or more faults are detected by the one or more management systems, modify one or more stall margin adjustment parameters of the gas turbine engine based on detecting the one or more faults by the one or more management system, and adjust operation of the hybrid engine based on the one or more stall margin adjustment parameters.

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 hybrid-electric propulsion system includes a propulsor, a turbomachine, and an electrical system, the electrical system including an electric machine coupled to the turbomachine. A method for operating the propulsion system includes operating, by one or more computing devices, the turbomachine such that the turbomachine rotates the propulsor; receiving, by the one or more computing devices, a command to accelerate the turbomachine while operating the turbomachine; and providing, by the one or more computing devices, electrical power to the electric machine to add power to the turbomachine, the propulsor, or both in response to the received command to accelerate the turbomachine.

A system and computer-implemented method of determining an acceleration of an engine are provided. The system comprises a processor and a memory comprising instructions stored thereon which when executed by the processor cause the system to perform a method of determining an acceleration of an engine. The method comprises obtaining and storing zero-crossing timestamps in a buffer, determining angular displacement times of the shaft based on the timestamps, applying a conversion factor to the angular displacement times, determining an acceleration of a shaft based on the angular displacement, and causing a fuel flow to the engine to be adjusted as a function of the acceleration as determined. The zero-crossing timestamps correspond to an angular displacement of a shaft associated with the engine. The zero-crossing timestamps are obtained using an angular displacement measurement device. The conversion factor corresponds to an angular displacement of the shaft.

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 shaft at a flight rotation speed when clutched and rotating the second shaft at a first idle rotation speed when unclutched, the first idle rotation speed above the placarded zone; decreasing a rotation speed of the first shaft from the flight rotation speed to a given rotation speed within the placarded zone; decreasing a rotation speed of the second shaft to the given rotation speed; clutching the second shaft; and decreasing the rotation speeds of the first and second shafts to a second idle rotation speed below the placarded zone.

Systems and methods for controlling an gas turbine engine are provided. The method comprises receiving a requested engine speed and obtaining a shaft inertia of the engine, a steady state fuel flow for the requested engine speed, and a relationship between fuel flow and acceleration power generated by the fuel flow. A required fuel flow to obtain an engine acceleration is determined as a function of the requested engine speed, the shaft inertia of the engine, the steady state fuel flow for the requested engine speed, and the relationship between fuel flow and acceleration power generated by the fuel flow. A command to a fuel flow metering valve is output in accordance with the required fuel flow.

During a stage (E0) of starting the turbine engine, the method of the invention comprises: an open-loop generating step (E10) of generating a fuel flow rate command (WF_OL) from at least one pre-established relationship; and a closed-loop monitoring step (E20-E30) of monitoring at least one operating parameter of the turbine engine selected from: a rate of acceleration (dN2/dt) of a compressor of the turbine engine; and a temperature (EGT) at the outlet from a turbine of the turbine engine; this monitoring step comprising maintaining (E30) the operating parameter in a determined range of values by using at least one corrector network (R1, R2, R3) associated with the parameter and suitable for delivering a signal for correcting the open-loop generated fuel flow rate command so as to maintain the operating parameter in the determined range of values.

A turbine engine includes a fan connected to a fan shaft, a combustion chamber, and an electric motor/generator in communication with the fan shaft. A controller is configured to direct power into the electric motor/generator during engine accelerations from steady state such that air flow to the combustion chamber is increased. The controller is further configured to direct power out of the electric motor/generator during engine decelerations from steady state such that air flow to the combustion chamber is decreased.

Herein provided are methods and systems for setting an acceleration schedule for engine start of a gas turbine engine. A rotational acceleration measurement of the engine is obtained after the engine is energized in response to a start request. The rotational acceleration measurement of the engine is compared to a threshold value within an acceleration band having a maximum threshold and a minimum threshold. An acceleration schedule is determined based on a position of the rotational acceleration measurement of the engine in the acceleration band relative to the threshold value.