Abstract: A system and method for warming a fuel cell on an aircraft, the system includes at least one fuel cell. The fuel cell includes an anode and a cathode for creating thermal and electrical energy. A temperature sensor measures a first temperature of the fuel cell. A control unit is coupled to the temperature sensor. The control unit increases the first temperature to a second temperature in response to the first temperature being at least equal to a selected temperature threshold. Increasing of the first temperature is indicative of the control unit operating in a warming mode. The second temperature is higher than the selected temperature threshold.

Abstract: A system and method for warming a fuel cell on an aircraft, the system includes at least one fuel cell. The fuel cell includes an anode and a cathode for creating thermal and electrical energy. A temperature sensor measures a first temperature of the fuel cell. A control unit is coupled to the temperature sensor. The control unit increases the first temperature to a second temperature in response to the first temperature being at least equal to a selected temperature threshold. Increasing of the first temperature is indicative of the control unit operating in a warming mode. The second temperature is higher than the selected temperature threshold.

Abstract: A system and method for warming a fuel cell on an aircraft, the system includes at least one fuel cell. The fuel cell includes an anode and a cathode for creating thermal and electrical energy. A temperature sensor measures a first temperature of the fuel cell. A control unit is coupled to the temperature sensor. The control unit increases the first temperature to a second temperature in response to the first temperature being at least equal to a selected temperature threshold. Increasing of the first temperature is indicative of the control unit operating in a warming mode. The second temperature is higher than the selected temperature threshold.

Abstract: A driveshaft for an aircraft ram air turbine includes a substantially cylindrical elongate portion, a first end extending from the elongate portion, and a second end extending from the elongate portion opposite the first end. The first and second ends each include a substantially frusto-conical section having a curved generatrix, such that distal portions of each of the first and second ends have smaller outer diameters than an outer diameter of the elongate portion. The elongate portion provides relatively high lateral stiffness and the first and second ends provide relatively low torsional stiffness, such that the driveshaft has a lateral natural frequency higher than an operating range of the driveshaft and has a torsional natural frequency below the operating range of the driveshaft.

Abstract: A system of speed control for a ram air turbine of an aircraft includes a power electronics controller, at least one routing device in communication with the power electronics controller, at least one secondary load in serial communication with the at least one routing device and the power electronics controller, and a ram air turbine (RAT) in communication with the power electronics controller, wherein the power electronics controller is configured to apply the secondary load to the RAT through the at least one routing device in response to a transient speed increase of the RAT.

Abstract: A system and method for warming a fuel cell on an aircraft, the system includes at least one fuel cell. The fuel cell includes an anode and a cathode for creating thermal and electrical energy. A temperature sensor measures a first temperature of the fuel cell. A control unit is coupled to the temperature sensor. The control unit increases the first temperature to a second temperature in response to the first temperature being at least equal to a selected temperature threshold. Increasing of the first temperature is indicative of the control unit operating in a warming mode. The second temperature is higher than the selected temperature threshold.

Abstract: A system of speed control for a ram air turbine of an aircraft includes a power electronics controller, at least one routing device in communication with the power electronics controller, at least one secondary load in serial communication with the at least one routing device and the power electronics controller, and a ram air turbine (RAT) in communication with the power electronics controller, wherein the power electronics controller is configured to apply the secondary load to the RAT through the at least one routing device in response to a transient speed increase of the RAT.

Abstract: A driveshaft for an aircraft ram air turbine includes a tubular body and a flange. The tubular body defines an axis of rotation and includes a forward portion and a frusto-conical portion located rearward of the forward portion. The flange adjoins the forward portion of the tubular body opposite the frusto-conical portion, and has a forward face and an opposite rear face. A ratio of an outer diameter of the forward portion of the tubular body to an inner diameter of the forward portion of the tubular body is in a range of approximately 1.423 to 1.425.

Abstract: A driveshaft for an aircraft ram air turbine includes a substantially cylindrical elongate portion, a first end extending from the elongate portion, and a second end extending from the elongate portion opposite the first end. The first and second ends each include a substantially frusto-conical section having a curved generatrix, such that distal portions of each of the first and second ends have smaller outer diameters than an outer diameter of the elongate portion. The elongate portion provides relatively high lateral stiffness and the first and second ends provide relatively low torsional stiffness, such that the driveshaft has a lateral natural frequency higher than an operating range of the driveshaft and has a torsional natural frequency below the operating range of the driveshaft.