A method for operating a hybrid electric propulsion system of an aircraft, the hybrid electric propulsion system comprising a turbomachine, an electric machine coupled to the turbomachine, and a propulsor coupled to the turbomachine, the method comprising: operating the turbomachine to drive the propulsor; receiving data indicative of a failure condition of the hybrid electric propulsion system; and extracting power from the turbomachine using the electric machine to slow down one or more rotating components of the turbomachine in response to receiving the data indicative of the failure condition.

The method can include: monitoring a current value of a rate of reduction of torque of the shaft; providing a threshold value for the rate of reduction of torque of the shaft; and generating a signal indicative of the shaft shear event when the current value exceeds the threshold value.

A hybrid electric propulsion system including: a gas turbine engine comprising a low speed spool and a high speed spool, the low speed spool comprising a low pressure compressor and a low pressure turbine, and the high speed spool comprising a high pressure compressor and a high pressure turbine; an electric motor configured to augment rotational power of the high speed spool or the low speed spool; and a controller to: detect an in-flight windmill re-start condition of the gas turbine engine; and cause power to be supplied from a power source to the electric motor in order to augment rotational power of the high speed or the low speed spool during the detected in-flight windmill re-start condition.

A first fuel flow rate command value indicating a command value of a fuel input amount is calculated so that an output of a gas turbine matches a target output. An upper limit value of the first fuel flow rate command value is calculated based on a deviation obtained by subtracting, from an estimated value of a turbine inlet temperature of the gas turbine, a second limit value relating to the estimated value set such that the estimated value does not exceed a first limit value of the turbine inlet temperature.

A method for operating a hybrid electric propulsion system of an aircraft, the hybrid electric propulsion system comprising a turbomachine, an electric machine coupled to the turbomachine, and a propulsor coupled to the turbomachine, the method comprising: operating the turbomachine to drive the propulsor; receiving data indicative of a failure condition of the hybrid electric propulsion system; and extracting power from the turbomachine using the electric machine to slow down one or more rotating components of the turbomachine in response to receiving the data indicative of the failure condition.

Exemplary embodiments are disclosed of variable frequency drive (VFD) controllers with engine fail-over and systems including the same. In exemplary embodiments, a system includes a controller configured to be operable for controlling a VFD that drives a motor (e.g., a three-phase AC motor, etc.), which, in turn, drives (e.g., mechanically spins, etc.) a first pump. The same controller is also configured to be operable for controlling an engine (e.g., a diesel engine, etc.), which, in turn, drives (e.g., mechanically spins, etc.) a second pump. The system is configured to failover from the motor to the engine in response to a VFD communications failure.

There is described a shaft shear event detection method. The method comprises storing in memory a shaft oscillation signature determined as a function of known characteristics of the shaft and associated with a shaft shear event; monitoring a rotational speed of the shaft; detecting from the rotational speed an oscillation wave superimposed on the rotational speed by detecting a first period below a lower threshold and a second period above an upper threshold, and detecting a rate of occurrence of the first period and the second period, the oscillation wave having a wave modulation frequency corresponding to the rate of occurrence and a wave modulation amplitude; comparing the oscillation signature to the oscillation wave; and detecting the shaft shear event when the oscillation wave corresponds to the oscillation signature.

A dual trip manifold assembly (TMA) includes an isolation valve assembly having a first valve configured to receive a flow of fluid from a hydraulic system fluid supply. The first valve is configured to channel the flow of fluid to at least one hydraulic circuit. The isolation valve assembly also includes a second valve configured to receive the flow of fluid from the at least one hydraulic circuit of the at least two hydraulic circuits. The second valve is further configured to channel the fluid flow to a trip header and to receive the fluid flow from the trip header. The first valve and the second valve are synchronized to each other such that rotation of one of said first and second valves causes a substantially similar rotation in the other of said first and second valves header.

A hybrid electric propulsion system including: a gas turbine engine comprising a low speed spool and a high speed spool, the low speed spool comprising a low pressure compressor and a low pressure turbine, and the high speed spool comprising a high pressure compressor and a high pressure turbine; an electric motor configured to augment rotational power of the high speed spool or the low speed spool; and a controller to: detect an in-flight windmill re-start condition of the gas turbine engine; and cause power to be supplied from a power source to the electric motor in order to augment rotational power of the high speed or the low speed spool during the detected in-flight windmill re-start condition.

A controller for a gas turbine wherein the gas turbine includes the compressor arranged to operate at a rotational speed n, the combustor and the fuel supply includes the first fuel supply and the second fuel supply, wherein the compressor is arranged to provide air to the combustor at a steady state air mass flow rate m.sub.ss and wherein the fuel supply is arranged to supply fuel at a fuel mass flow rate m.sub.total to the combustor. The controller is arranged to, responsive to the load change L to the load L, control the fuel supply to supply a proportion Z of the fuel mass flow rate m.sub.total as a fuel mass flow rate m.sub.fuel pilot via the first fuel supply based, at least in part, on a combustor mass flow rate m.sub.t.