The invention relates to: Control circuit (1) for an electrical device (2), said control circuit (1) receiving as input a discrete electrical control signal (CMD), the control circuit (1) comprising a source (11) of voltage (±V) configured so as to supply the circuit according to a negative or positive voltage; a switch (12) normally closed in the absence of any discrete electrical control signal (CMD) and configured so as to isolate the electrical device from the voltage source as a function of the electrical control signal (CMD), said switch being connected between the voltage source and the electrical device (2); the switch (12) being sensitive to the discrete electrical control signal (CMD) for just one sense of voltage.

An airplane has main propulsion engines and a first fuel supply for the main propulsion engines. The airplane further has an auxiliary propulsion engine and a second fuel supply for the auxiliary propulsion engine, this second fuel supply being separate from the first fuel supply. The auxiliary propulsion engine can be switched on independently from the main propulsion engines. Such airplane has increased safety, since it will be possible to maintain flight, particularly when at high altitude, even if all main propulsion engines have failed.

A refuel adapter, which may, among other things, be suitable for aircraft refueling includes a casing and a butterfly valve disposed within an interior of the casing. The butterfly valve includes a body defining an opening and a disc rotatable within the body about an axis of rotation to selectively close the opening. The disc includes at least one opening therethrough, and a first flap and a second flap are each rotatably attached to the disc to selectively cover a portion of the at least one opening. The butterfly valve may be movable between (i) a static position in which the disc and the first and second flaps are in a closed position, (ii) a refuel position in which the disc may be in a closed position and the flaps are in an open position, and (iii) a defuel position in which the disc may be in an open position.

A pipe joint with a socket, and a pipe fitted into the socket. An annular seal is compressed between the socket and the pipe. The seal is electrically conductive and resiliently flexible. The socket or the pipe has a recess which houses the seal. The recess has a ridge in a base of the recess and the seal has a groove which extends around a radial periphery of the seal. The ridge fits into the groove to fool proof the installation, such that a standard non-conductive O-ring seal is more difficult to install in error.

The present disclosure provides methods and systems for fault detection for a speed sensing system of a multi-engine rotorcraft. A shaft speed for a first engine and a rotor speed for at least one rotor of the multi-engine rotorcraft are obtained. The shaft speed is compared to the rotor speed. When the shaft speed is greater than the rotor speed, a first fault in the speed sensing system is detected and a first speed sensing system fault signal is issued. When the shaft speed is less than the rotor speed, a determination is made regarding whether the first engine is coupled the at least one rotor based on a fuel flow to the first engine. A second fault in the speed sensing system is detected and a second speed sensing system fault signal is issued responsive to determining that the first engine is coupled to the at least one rotor.

The present disclosure provides methods and systems for fault detection for a speed sensing system of a multi-engine rotorcraft. A shaft speed for a first engine and a rotor speed for at least one rotor of the multi-engine rotorcraft are obtained. The shaft speed is compared to the rotor speed. When the shaft speed is greater than the rotor speed, a first fault in the speed sensing system is detected and a first speed sensing system fault signal is issued. When the shaft speed is less than the rotor speed, a determination is made regarding whether the first engine is coupled the at least one rotor based on a fuel flow to the first engine. A second fault in the speed sensing system is detected and a second speed sensing system fault signal is issued responsive to determining that the first engine is coupled to the at least one rotor.

In some examples, an air treatment system includes a filter, an ozone sensor, and a separator configured to separate air into a nitrogen-enriched gas and an oxygen-enriched gas. The filter is configured to remove ozone from an air stream and supply filtered air to the separator. The ozone sensor is configured to sense an ozone level of the filtered air issuing from the filter prior to encountering the separator. The air treatment system may include processing circuitry configured to monitor the ozone level sensed. The air treatment system may be part of an inerting system configured to supply the nitrogen-enriched gas to an ullage space of a fuel tank.

A control system (50) for an electro-hydraulic servo-actuator (26) envisages: a controller (55), to generate a control current (I.sub.c), designed to control actuation of the electro-hydraulic servo-actuator (26), implementing a position control loop based on a position error (e.sub.p), the position error (e.sub.p) being a difference between a reference position (Pos.sub.ref) and a measured position (Pos.sub.meas) of the electro-hydraulic servo-actuator (26); and a limitation stage (58), coupled to the controller (55) to provide a limitation of the actuator speed of the electro-hydraulic servo-actuator (26); the limitation stage (58) limits a rate of change of a driving current (I.sub.d) to be supplied to the electro-hydraulic servo-actuator (26), in order to limit the actuator speed.

Hybrid electric propulsion systems and methods therefore are provided. More particularly, the present disclosure is directed to control systems for hybrid electric propulsion systems for aerial vehicles that are configured for rapidly and automatically taking action in response to rapid electrical load changes on a torque source, such as an engine. Methods for operating hybrid electric propulsion systems for aerial vehicles are also provided.

Hybrid electric propulsion systems and methods therefore are provided. More particularly, the present disclosure is directed to control systems for hybrid electric propulsion systems for aerial vehicles that are configured for rapidly and automatically taking action in response to rapid electrical load changes on a torque source, such as an engine. Methods for operating hybrid electric propulsion systems for aerial vehicles are also provided.