Abstract: A powertrain for a rotorcraft includes first and second engines and a transmission system that includes a main rotor gearbox, a first freewheeling unit coupling the first engine to the main rotor gearbox and a second freewheeling unit coupling the second engine to the main rotor gearbox. The first freewheeling unit has a driving configuration and a bypass configuration. In a preflight configuration of the rotorcraft, the first engine provides power to at least one auxiliary component with the first freewheeling unit in the bypass configuration while the second engine provides power to the main rotor. In a flight configuration of the rotorcraft, the first engine provides power to the main rotor with the first freewheeling unit in the driving configuration while the second engine also provides power to the main rotor.

Abstract: A method of optimizing a planetary gear system for continued operation after failure of a planet gear includes providing a planetary gear system and reducing a backup ratio of a planet gear of the planetary gear system by reducing a rim thickness of the planet gear.

Abstract: A powertrain for a rotorcraft includes first and second engines and a transmission system that includes a main rotor gearbox, a first freewheeling unit coupling the first engine to the main rotor gearbox and a second freewheeling unit coupling the second engine to the main rotor gearbox. The first freewheeling unit has a driving configuration and a bypass configuration. In a preflight configuration of the rotorcraft, the first engine provides power to at least one auxiliary component with the first freewheeling unit in the bypass configuration while the second engine provides power to the main rotor. In a flight configuration of the rotorcraft, the first engine provides power to the main rotor with the first freewheeling unit in the driving configuration while the second engine also provides power to the main rotor.

Abstract: A gear shaft allows a ceramic bearing to be used in environments where gear steel is desirable for driving a gear. The gear shaft includes a gear region and a bearing region. A bearing can be disposed about the bearing region of the gear shaft. A gear can be disposed about the gear region of the gear shaft. The bearing includes a ceramic material. The gear region of the gear shaft includes gear steel, whereas the bearing region of the gear shaft includes a bearing-region material that has a coefficient of thermal expansion (CTE) that is close to the CTE of the ceramic material.

Abstract: An active cooling system includes a sensor configured to monitor a status of a lubrication system of a lubricated component and a cowling configured to cover at least a portion of the lubricated component. The cowling includes an inlet panel configured to move from a normal operating position to a cooling position, wherein the cooling position creates an air inlet configured to increase airflow passing by the lubricated component. The active cooling system further includes an actuator configured to initiate movement of the inlet panel from the normal operating position to the cooling position.

Abstract: A bearing liner allows a bearing to be mounted to a bearing housing even where the coefficients of thermal expansion of the bearing and the housing are different. The bearing liner includes a body portion and a mounting portion. The body portion has a cylindrical substrate that extends about a longitudinal axis of the bearing. The mounting portion includes mounting tabs that extend from the body portion of the liner. The mounting tabs allow the liner to be fixed to the housing and to the bearing. The mounting tabs are configured to flex relative to the body portion of the liner so as to allow for thermal expansion and contraction of the housing relative to the bearing while still securing the bearing to the housing.

Abstract: A method of optimizing a planetary gear system for continued operation after failure of a planet gear includes providing a planetary gear system and reducing a backup ratio of a planet gear of the planetary gear system by reducing a rim thickness of the planet gear.

Abstract: A gear shaft allows a ceramic bearing to be used in environments where gear steel is desirable for driving a gear. The gear shaft includes a gear region and a bearing region. A bearing can be disposed about the bearing region of the gear shaft. A gear can be disposed about the gear region of the gear shaft. The bearing includes a ceramic material. The gear region of the gear shaft includes gear steel, whereas the bearing region of the gear shaft includes a bearing-region material that has a coefficient of thermal expansion (CTE) that is close to the CTE of the ceramic material.

Abstract: A bearing liner allows a bearing to be mounted to a bearing housing even where the coefficients of thermal expansion of the bearing and the housing are different. The bearing liner includes a body portion and a mounting portion. The body portion has a cylindrical substrate that extends about a longitudinal axis of the bearing. The mounting portion includes mounting tabs that extend from the body portion of the liner. The mounting tabs allow the liner to be fixed to the housing and to the bearing. The mounting tabs are configured to flex relative to the body portion of the liner so as to allow for thermal expansion and contraction of the housing relative to the bearing while still securing the bearing to the housing.