A safety management system for an aircraft, or a propulsion system thereof including a fuel cell assembly and a combustion engine, may include various sensors and controllers configured to execute a safety action. At least one sensor is configured to detect at least one operating parameter of the propulsion system, and a controller is configured to determine that the at least one operating parameter has achieved a safety threshold and to execute a safety action when the at least one operating parameter has achieved the safety threshold. The safety action is configured to control operation of the fuel cell assembly and to control operation of the combustion engine.

An aircraft with increased crash robustness including a fuselage with a forward end, an opposite rear end, a ventral surface, and a dorsal surface. The aircraft further including a longitudinal axis running from the rear end to the forward end and a dorsoventral axis orthogonal to the longitudinal axis and running from the dorsal surface to the ventral surface. The aircraft also including at least a battery module located within the fuselage comprising a plurality of battery cells, each battery cell includes an axial axis positioned orthogonally to each of the longitudinal axis and the dorsoventral axis, and each battery cell has a plurality of radial axes orthogonal to the axial axis, wherein the plurality of radial axes includes a first radial axis aligned with the longitudinal axis and a second radial axis aligned with the dorsoventral axis.

A system includes a turbo pump to convert compressed gas into power, a storage tank to store the compressed gas, and a fire suppression control valve having a closed position in which the compressed gas is prevented from flowing to the cargo compartment and an open position in which the compressed gas is ported to the cargo compartment to suppress a fire. The system also includes a pump control valve having a closed position in which the compressed gas is prevented from flowing to the turbo pump and an open position in which the compressed gas is ported to the turbo pump to cause the turbo pump to convert the compressed gas into the power. The system also includes an OBIGGS to convert bleed air from a gas turbine engine into an inert gas to provide low rate discharge (LRD) fire suppression to the cargo compartment.

A system includes a turbo pump to convert compressed gas into power, a storage tank to store the compressed gas, and a fire suppression control valve having a closed position in which the compressed gas is prevented from flowing to the cargo compartment and an open position in which the compressed gas is ported to the cargo compartment to suppress a fire. The system also includes a pump control valve having a closed position in which the compressed gas is prevented from flowing to the turbo pump and an open position in which the compressed gas is ported to the turbo pump to cause the turbo pump to convert the compressed gas into the power. The system also includes an OBIGGS to convert bleed air from a gas turbine engine into an inert gas to provide low rate discharge (LRD) fire suppression to the cargo compartment.

Fuel tank inerting systems are described. The systems include a fuel tank, a catalytic reactor arranged to receive a reactant mixture comprising a first reactant and a second reactant to generate an inert gas to be supplied to the fuel tank to fill an ullage space of the fuel tank, a condenser heat exchanger arranged between the catalytic reactor and the fuel tank and configured to cool an output from the catalytic reactor, and a fan assembly arranged within an inerting system flow path upstream of the catalytic reactor, wherein the fan assembly is arranged within a gas flow having a temperature of at least 185° C.

In accordance with at least one aspect of this disclosure, a fluid system of an aircraft includes a primary fluid conduit that conveys a primary fluid, and a leak detection system disposed around at least a portion of the primary fluid conduit and forming one or more detection volumes. The leak detection system determines whether there is a primary fluid leak into the one or more detection volumes by sensing a pressure change in the one or more detection volumes.

In accordance with at least one aspect of this disclosure, there is provided a system for an aircraft engine. In embodiments, the system includes an accessory box and a fuel accessory located in an interior space within the accessory box, where a vent is defined through a wall of the accessory box. In embodiments, the vent includes a plurality of holes or slots in an outer wall of the accessory box for passage of gaseous fuel from the interior space. In embodiments, the vent is configured for passive ventilation of the interior space.

In accordance with at least one aspect of this disclosure, there is provided a system for an aircraft engine. In embodiments, the system includes an accessory box and a fuel accessory located in an interior space within the accessory box, where a vent is defined through a wall of the accessory box. In embodiments, the vent includes a plurality of holes or slots in an outer wall of the accessory box for passage of gaseous fuel from the interior space. In embodiments, the vent is configured for passive ventilation of the interior space.

In accordance with at least one aspect of this disclosure, there is provided a system for an aircraft engine. In embodiments, the system includes an accessory box and a fuel accessory located in an interior space within the accessory box, where a vent is defined through a wall of the accessory box. In embodiments, the vent includes a plurality of holes or slots in an outer wall of the accessory box for passage of gaseous fuel from the interior space. In embodiments, the vent is configured for passive ventilation of the interior space.

In accordance with at least one aspect of this disclosure, there is provided a system for an aircraft engine. In embodiments, the system includes an accessory box and a fuel accessory located in an interior space within the accessory box, where a vent is defined through a wall of the accessory box. In embodiments, the vent includes a plurality of holes or slots in an outer wall of the accessory box for passage of gaseous fuel from the interior space. In embodiments, the vent is configured for passive ventilation of the interior space.