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.

The disclosure provides composite polymer compositions comprising a polyaryl ether ketone base polymer, a conductive filler, a dispersing and processing additive, and optionally a dielectric filler. The composite polymers exhibit retained or improved strength, increased toughness, and significantly increased elongation at break compared to the base polymer. The composite polymer may be used in lightweight, non-metallic fuel conveyance systems in aircraft.

The disclosure provides composite polymer compositions comprising a polyaryl ether ketone base polymer, a conductive filler, a dispersing and processing additive, and optionally a dielectric filler. The composite polymers exhibit retained or improved strength, increased toughness, and significantly increased elongation at break compared to the base polymer. The composite polymer may be used in lightweight, non-metallic fuel conveyance systems in aircraft.

A system and method for the transfer of cryogenic fluid fuel includes a nozzle positionable with respect to fuel tank inlet, e.g., of an unmanned aerial vehicle (UAV), a seal to seal the area where the nozzle and inlet are connected, a collapsible and expandable bellows providing an isolation volume where the fluid is transferred from the nozzle into the inlet; a vacuum is provided in the volume to avoid accumulation of fuel or other species in the volume.

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.

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.

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.

Provided is a fuel system that can reduce the amount of fuel in a second tank before the amount of fuel in a first tank. A fuel system includes: a first tank and a second tank that respectively store fuel; a fuel supply pump that supplies at least the fuel in the first tank out of the first and second tanks to a fuel consuming section; a transfer pump that transfers the fuel in the second tank into the first tank; and a fuel passage having an inlet in communication with an inner portion of the first tank, and an outlet in communication with an inner portion of the second tank. The fuel in the first tank overflows into the second tank through the fuel passage.

Provided is a fuel system that can reduce the amount of fuel in a second tank before the amount of fuel in a first tank. A fuel system includes: a first tank and a second tank that respectively store fuel; a fuel supply pump that supplies at least the fuel in the first tank out of the first and second tanks to a fuel consuming section; a transfer pump that transfers the fuel in the second tank into the first tank; and a fuel passage having an inlet in communication with an inner portion of the first tank, and an outlet in communication with an inner portion of the second tank. The fuel in the first tank overflows into the second tank through the fuel passage.