Aircraft hydrogen fuel systems and methods and systems of starting such systems are described. The aircraft hydrogen fuel systems include a hydrogen burning main engine, a main tank configured to contain liquid hydrogen to be supplied to the main engine during a normal operation, and a starter tank configured to contain gaseous hydrogen to be used during a startup operation of the main engine. Methods and processes for starting and/or restarting such systems are described.

According to an exemplary embodiment, an inerting and pressurization system for a fuel tank may be provided. The inerting and pressurization systemmay include an inert gas supply network, a number of valves and a number of air separator modules. The inerting and pressurization system may further include a programmable controller that may automatically increase the proportion of inert gas in the inert gas supply network. According to a second exemplary embodiment, a fire extinguishing system may include a number of air-separation modules that may supply an inert gas to a supply network and a programmable controller that may be operatively connected with the inert gas supply network to control how the inert gas outputs may be distributed in response to a fire threat signal.

A fuel system includes a fuel gathering system in fluid communication with a fuel storage container, and a fluid pump assembly in fluid communication with the fuel gathering system. The fluid pump assembly includes a main gear pump stage and a first flow attenuator. A main driven gear is meshed with a main drive gear in a main pump conduit, and a main pump bearing assembly rotatably supports the main drive gear and the main driven gear. The first flow attenuator is disposed around the main pump conduit, and includes a substantially polygonal fluid opening. Edges of the opening are substantially aligned with an undercut bearing portion on at least one of an inlet side and an outlet side of the main pump conduit to define a non-round fluid boundary.

A fuel system includes a fuel gathering system in fluid communication with a fuel storage container, and a fluid pump assembly in fluid communication with the fuel gathering system. The fluid pump assembly includes a main gear pump stage and a first flow attenuator. A main driven gear is meshed with a main drive gear in a main pump conduit, and a main pump bearing assembly rotatably supports the main drive gear and the main driven gear. The first flow attenuator is disposed around the main pump conduit, and includes a substantially polygonal fluid opening. Edges of the opening are substantially aligned with an undercut bearing portion on at least one of an inlet side and an outlet side of the main pump conduit to define a non-round fluid boundary.

The invention provides an aircraft fuel system comprising a fuel storage facility for storing fuel and ullage, a separate ullage storage facility for storing ullage, and a transfer arrangement for transferring ullage between the fuel storage facility and the ullage storage facility, wherein the transfer arrangement is capable of controlling the transfer of ullage based on a pressure input to the transfer arrangement. The invention also provides an aircraft with such a fuel system and a method of operating an aircraft.

The invention provides an aircraft fuel system comprising a fuel storage facility for storing fuel and ullage, a separate ullage storage facility for storing ullage, and a transfer arrangement for transferring ullage between the fuel storage facility and the ullage storage facility, wherein the transfer arrangement is capable of controlling the transfer of ullage based on a pressure input to the transfer arrangement. The invention also provides an aircraft with such a fuel system and a method of operating an aircraft.

A system comprises a non-transitory machine readable storage medium storing instructions and a database identifying a plurality of assets and a state of each asset. The instructions configure a processor for receiving updates to a distributed electronic ledger managed by plural peer processors. Each update includes an event or change affecting one of the assets. The peer processors verify portions of the ledger describing each event or change. At least one of the updates has not yet been recorded in the ledger at a time of the receiving. The processor computes a state of each asset, based on the updates, receives a request for a state of one of the assets; and responds to the request, reflecting each event and change affecting that asset. The response is performed without waiting for the peer processors to verify an update that has not yet been recorded in the ledger.

An over-pressure vent (OPV) system is provided for a fuel tank of an aircraft. The OPV system includes an OPV valve configured to be coupled in fluid communication with a supply line of a nitrogen enriched air distribution system (NEADS) such that the OPV valve is configured to vent pressure from the supply line. The OPV valve is configured to be coupled in fluid communication with the supply line upstream from an outlet of the supply line from which the NEADS delivers nitrogen enriched gas to the fuel tank. The OPV valve is configured to sense a pressure within the supply line upstream from the outlet of the supply line.

An over-pressure vent (OPV) system is provided for a fuel tank of an aircraft. The OPV system includes an OPV valve configured to be coupled in fluid communication with a supply line of a nitrogen enriched air distribution system (NEADS) such that the OPV valve is configured to vent pressure from the supply line. The OPV valve is configured to be coupled in fluid communication with the supply line upstream from an outlet of the supply line from which the NEADS delivers nitrogen enriched gas to the fuel tank. The OPV valve is configured to sense a pressure within the supply line upstream from the outlet of the supply line.

A fuel system is provided for an aircraft having a fuel source. The fuel system includes a fuel oxygen reduction unit defining a liquid fuel supply path, a stripping gas supply path, a liquid fuel outlet path, and a stripping gas return path, wherein the stripping gas return path is in airflow communication with the fuel source.