A heater that inhibits the formation of ice in an air gap separating a stationary stator and a rotatable rotor of a rotating machine. The heater includes a plurality of stringers configured to be arranged in associated winding slots of the associated stator adjacent the air gap, and extending between two ends of the heater. Each of the stringers includes two electrical resistance heating traces arranged between two electrical insulation layers that are arranged between two thermal conduction layers. The traces extend along an entire length of each of the stringers between the two ends of the heater. The traces are electrically isolated from each other.

Described are inerting systems that may be used on board an aircraft or other passenger transportation vehicle to reduce a risk of fire due to electronic components or to other elements in a compartment and to assist in preventing or extinguishing any fire or hazardous condition that may occur. The systems include a source of inert gas such as oxygen depleted air generated from a fuel cell on board the aircraft. The oxygen depleted air or other inert gas is conveyed through ducts to compartments that house the electronics, thus changing the conditions in the compartment to be less conducive to fire.

Described are inerting systems that may be used on board an aircraft or other passenger transportation vehicle to reduce a risk of fire due to electronic components or to other elements in a compartment and to assist in preventing or extinguishing any fire or hazardous condition that may occur. The systems include a source of inert gas such as oxygen depleted air generated from a fuel cell on board the aircraft. The oxygen depleted air or other inert gas is conveyed through ducts to compartments that house the electronics, thus changing the conditions in the compartment to be less conducive to fire.

Embodiments of the present disclosure relate generally to the use of the fuel cell systems on board aircraft and other passenger transportation vehicles and to methods of using heat, air, and water generated by such fuel cell systems. The heat may be used to address condensation within the aircraft. The heat may be used to help evaporate excess water that would otherwise condense in the aircraft skin. The excess water collected may be used to create humidification for cabin air. In other examples, the heat, warmed air, or warmed water may be delivered to other locations or heating systems for beneficial use.

Embodiments of the present disclosure relate generally to the use of the fuel cell systems on board aircraft and other passenger transportation vehicles and to methods of using heat, air, and water generated by such fuel cell systems. The heat may be used to address condensation within the aircraft. The heat may be used to help evaporate excess water that would otherwise condense in the aircraft skin. The excess water collected may be used to create humidification for cabin air. In other examples, the heat, warmed air, or warmed water may be delivered to other locations or heating systems for beneficial use.

A spring compression device comprises a spring sleeve configured to receive a spring; a spring adjustment member provided on and engaged with the spring sleeve and configured to abut a spring mounted on the spring sleeve, wherein the spring sleeve and spring adjustment member define an operating length (L) of the spring compression device, and the spring adjustment member is configured to be moved relative to the spring sleeve to adjust the operating length of the spring compression device; and at least one blocking component for blocking movement between the spring sleeve and the spring adjustment member.

A power unit for producing both alternating current and direct current includes a switcher connected to a direct current source, wherein the switcher includes circuitry configured to produce both alternating current having first characteristics and direct current having second characteristics, wherein the circuitry comprises a plurality of insulated gate bipolar transistor circuits and drive circuits connected to the insulated gate bipolar transistor circuits. The switcher may receive variable voltage and frequency or constant voltage and frequency. In either case, the switcher circuitry is able to provide power of the desired characteristics. The power unit may be used to power aircraft when the aircraft is on the ground.

A power unit for producing both alternating current and direct current includes a switcher connected to a direct current source, wherein the switcher includes circuitry configured to produce both alternating current having first characteristics and direct current having second characteristics, wherein the circuitry comprises a plurality of insulated gate bipolar transistor circuits and drive circuits connected to the insulated gate bipolar transistor circuits. The switcher may receive variable voltage and frequency or constant voltage and frequency. In either case, the switcher circuitry is able to provide power of the desired characteristics. The power unit may be used to power aircraft when the aircraft is on the ground.

A failsafe multimode clutch assembly positioned in a powertrain of a rotorcraft. The clutch assembly includes a freewheeling having a driving mode in which torque applied to the input race is transferred to the output race and an overrunning mode in which torque applied to the output race is not transferred to the input race. A bypass assembly has an engaged position that couples the input and output races of the freewheeling unit. An actuator assembly uses pressurized lubricating oil to shift the bypass assembly between the engaged position and a disengaged position. A lock assembly enables and disables actuation of the bypass assembly. In the disengaged position, the overrunning mode of the freewheeling unit enables a unidirectional torque transfer mode of the clutch assembly. In the engaged position, the overrunning mode of the freewheeling unit is disabled such that the clutch assembly is configured for bidirectional torque transfer.

An electric power supply is disclosed having high-voltage, direct-current (HVDC) circuitry comprising one or more DC pre-charge capacitors and one or more power transistor switches, the HVDC circuitry configured to receive high-voltage, direct-current (HVDC) input power of about 320 volts and/or greater and convert the HVDC input power to multi-phase, high-voltage, alternating-current (HVAC) output power of about 320 volts and/or greater; and low-voltage, direct current (LVDC) circuitry adapted and configured to operate on low-voltage, direct-current, wherein the LVDC circuitry is configured to control and monitor the multi-phase HVAC output power. The electric power supply is further configured to operate in reverse and convert received multiphase HVAC input power to HVDC output power.