Methods and systems for operating an engine, the engine having an engine core, an exhaust nozzle, and variable geometry mechanisms, are provided. A request for an increase in thrust generated by the engine is received. In response to receipt of the request, it is determined that at least one operating condition for engine degradation thrust is met. In response to this determination, the variable geometry mechanisms are modulated to degrade an efficiency of the engine, thereby increasing a temperature of core air flowing through the engine core. The increase in thrust is generated from the increased temperature of the core air flowing through the engine core and into the exhaust nozzle.

In a method for operating an engine, a request for an increase in thrust generated by the engine is received. In response to receipt of the request, a determination is made as to whether at least one operating condition for heat application-based thrust is met. If so, a heat source is applied to heat bypass air flowing through the bypass duct towards the exhaust nozzle and the increase in thrust is generated from an increased temperature of mixed bypass air and core air at the exhaust nozzle.

In accordance with at least one aspect of this disclosure, there is provided a fuel system for a gas turbine engine of an aircraft, including a main inlet feed conduit fluidly connected to a primary manifold feed conduit and a secondary manifold feed conduit. A primary manifold fluidly connects the primary manifold feed conduit to a plurality of primary fuel injectors, and a secondary manifold fluidly connects the secondary manifold feed conduit to a plurality of secondary fuel injectors.

An aircraft that includes a hybrid-electric propulsion system is provided. In one aspect, the hybrid-electric propulsion system includes at least one propulsor that includes a gas turbine engine and an electric machine mechanically coupled with a spool of the gas turbine engine. When idle operation is commanded, electrical power is provided to the electric machine to cause the electric machine to apply torque to the spool and fuel provided to the engine can be reduced. Thus, the electric machine is controlled to provide a power assist to maintain the engine at the commanded idle speed whilst reducing fuel consumption.

The present disclosure provides systems and methods for controlling thrust produced at takeoff by at least one engine (114, 116) of an aircraft (100). At least one input signal comprising input data indicative of a speed of the aircraft is received (202). The speed of the aircraft is compared to a first pre-determined threshold. Responsive to determining that the speed is below the first threshold, a thrust limit for the at least one engine is determined (204) from the input data and output to the at least one engine a thrust limitation signal for causing the thrust to be limited according to the thrust limit (210).

An aircraft includes a gas turbine engine and an optically-based measurement system. The gas turbine engine is configured to ingest a first mass flow and to exhaust a second mass flow. The optically-based measurement system is configured to determine the first and second mass flows in response to performing an imaging process on the gas turbine engine.

A system of a hybrid aircraft includes a first gas turbine engine including a fan, a high speed spool, and a low spool motor configured to drive rotation of the fan. The system also includes a second gas turbine engine and a controller. The controller is operable to determine an operating mode of the hybrid aircraft, control the low spool motor to drive rotation of the fan of the first gas turbine engine responsive to a thrust command while the second gas turbine engine is driven by commanding fuel combustion based on the operating mode, and accelerate the high speed spool of the first gas turbine engine and command fuel combustion at the first gas turbine engine based on a transition of the operating mode to perform a starting operation of the first gas turbine engine.

A method of mitigating contrails produced by an aircraft having a set of gas turbine engines, comprises the steps of (i) for each engine in a first subset of the engines, reducing the operating efficiency of the engine to produce a reduction in thrust provided by that engine and (ii) for each engine in a second subset, increasing the fuel flow to the engine to increase the thrust provided by that engine, the set of at least two gas turbine engines consisting of the first and second subsets. The method provides for contrail mitigation action by means of engine operating efficiency reduction to be directed to a first subset of engines for which contrail mitigation per unit engine operating efficiency reduction is greatest, the resulting reduction in thrust provided by such engines being at least partially compensated by increasing fuel flow to engines of the second subset.

A gas turbine engine is provided. The gas turbine engine includes a turbomachine having a low speed spool and a high speed spool; a rotor assembly coupled to the low speed spool; an electric machine rotatable with the low speed spool for extracting power from the low speed spool, for adding power to the low speed spool, or both; and an inter-spool clutch positioned between the low speed spool and the high speed spool for selectively coupling the low speed spool to the high speed spool.

The aircraft can have a first engine secured to a first wing on a first side of a fuselage, and a second engine secured to a second wing on a second side of the fuselage, the second wing having a proximal end secured to the fuselage, and a distal end extending away from the fuselage. While operating the first engine, compressed gas can be conveyed from the first engine to a thrust generating device located at the distal end of the second wing.