A gas turbine engine for an aircraft and a method of operating a gas turbine engine on an aircraft. Embodiments disclosed include a gas turbine engine for an aircraft including: an engine core has a turbine, a compressor, and a core shaft; a fan located upstream of the engine core, the fan has a plurality of fan blades; a nacelle surrounding the engine core and defining a bypass duct and bypass exhaust nozzle; and a gearbox that receives an input from the core shaft and outputs drive to the fan wherein the gas turbine engine is configured such that a jet velocity ratio of a first jet velocity exiting from the bypass exhaust nozzle to a second jet velocity exiting from an exhaust nozzle of the engine core at idle conditions is greater by a factor of 2 or more than the jet velocity ratio at maximum take-off conditions.

A gas turbine engine for an aircraft and a method of operating a gas turbine engine on an aircraft. Embodiments disclosed include a gas turbine engine for an aircraft including: an engine core has a turbine, a compressor, and a core shaft; a fan located upstream of the engine core, the fan has a plurality of fan blades; a nacelle surrounding the engine core and defining a bypass duct and bypass exhaust nozzle; and a gearbox that receives an input from the core shaft and outputs drive to the fan wherein the gas turbine engine is configured such that a jet velocity ratio of a first jet velocity exiting from the bypass exhaust nozzle to a second jet velocity exiting from an exhaust nozzle of the engine core at idle conditions is greater by a factor of 2 or more than the jet velocity ratio at maximum take-off conditions.

A flow combiner is provided for a gas turbine engine. The flow combiner includes an outlet duct, a compressor bleed inlet duct coupled to the outlet duct, and a ventilation inlet duct coupled to the outlet duct. The compressor bleed inlet duct is configured to receive a bleed flow from a compressor of the gas turbine engine. The ventilation inlet duct is configured to receive a ventilation flow from an enclosure surrounding the gas turbine engine. The bleed flow and the ventilation flow are combined as an outlet flow through the outlet duct.

An aspect includes a method for motoring control for multiple engines of an aircraft is provided. A controller can determine a motoring time of a first engine starting system to cool a first engine. The controller can compare the motoring time of the first engine starting system with a motoring time of one or more other engine starting systems of one or more other engines of the aircraft. The motoring time of the first engine starting system can be controlled relative to a tolerance of the motoring time of the one or more other engine starting systems by adjusting the motoring time of the first engine starting system relative to the one or more other engine starting systems in a motoring sequence based on comparing the motoring time of the first engine starting system with the motoring time of the one or more other engine starting systems.

An aspect includes a method for motoring control for multiple engines of an aircraft is provided. A controller can determine a motoring time of a first engine starting system to cool a first engine. The controller can compare the motoring time of the first engine starting system with a motoring time of one or more other engine starting systems of one or more other engines of the aircraft. The motoring time of the first engine starting system can be controlled relative to a tolerance of the motoring time of the one or more other engine starting systems by adjusting the motoring time of the first engine starting system relative to the one or more other engine starting systems in a motoring sequence based on comparing the motoring time of the first engine starting system with the motoring time of the one or more other engine starting systems.

A compressor case for a gas turbine engine includes an annular body that extends circumferentially around a center axis and extends axially along the center axis. A first bleed manifold is formed on an outer surface of the annular body and encloses a first plenum. A second bleed manifold is formed on the outer surface of the annular body and is axially aft of the first bleed manifold. The second bleed manifold encloses a second plenum. A bleed inlet extends through the annular body and into the first bleed manifold. Cooling passages are formed in the annular body, and each of the cooling passages extends from the first plenum to the second plenum and fluidically connects the first plenum to the second plenum.

A compressor case for a gas turbine engine includes an annular body that extends circumferentially around a center axis and extends axially along the center axis. A first bleed manifold is formed on an outer surface of the annular body and encloses a first plenum. A second bleed manifold is formed on the outer surface of the annular body and is axially aft of the first bleed manifold. The second bleed manifold encloses a second plenum. A bleed inlet extends through the annular body and into the first bleed manifold. Cooling passages are formed in the annular body, and each of the cooling passages extends from the first plenum to the second plenum and fluidically connects the first plenum to the second plenum.

Systems and methods are disclosed for controlling surge margin in the compressor section of a gas turbine engine. Bypass ports on a first compressor section and second compressor section lead to a bypass conduit. An auxiliary turbine and discharge conduit are positioned in the bypass conduit. Fluid flow from the compressor sections into the bypass conduit via the bypass ports is controlled by bypass control valves.

Systems and methods are disclosed for controlling surge margin in the compressor section of a gas turbine engine. Bypass ports on a first compressor section and second compressor section lead to a bypass conduit. An auxiliary turbine and discharge conduit are positioned in the bypass conduit. Fluid flow from the compressor sections into the bypass conduit via the bypass ports is controlled by bypass control valves.

The present disclosure relates to an architecture of a propulsion system of a multi-engine helicopter comprising turboshaft engines connected to a power transmission gearbox, characterized in that it comprises: at least one hybrid turboshaft engine capable of operating in at least one standby mode during a stable cruise flight of the helicopter; at least two systems for controlling each hybrid turboshaft engine, each system comprising an electric machine connected to the hybrid turboshaft engine and suitable for rotating the gas generator thereof, and at least one source of electrical power for the electric machine, each reactivation system being configured such that it can drive the turboshaft engine in at least one operating mode among a plurality of predetermined modes.