Failsafe Multimode Clutch Assemblies for Rotorcraft

A powertrain for a rotorcraft, the powertrain comprising:

• a main drive system including a main engine;
• a secondary engine;
• and
• a failsafe multimode clutch assembly positioned between the main drive system and the secondary engine, the clutch assembly including:
• a freewheeling unit having an input race coupled to the main drive system and an output race coupled to the secondary engine, the freewheeling unit 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 having an engaged position in which the bypass assembly couples the input and output races of the freewheeling unit and a disengaged position in which the bypass assembly does not couple the input and output races of the freewheeling unit;
• and
• an actuator assembly configured to utilize a pressurized lubricating oil to generate an engagement signal that biases the bypass assembly toward the engaged position and a disengagement signal that biases the bypass assembly toward the disengaged position;
• and
• a lock assembly in fluid communication with the engagement signal, the lock assembly enabling actuation of the bypass assembly when the engagement signal is present and disabling actuation of the bypass assembly when the engagement signal is absent;
• wherein, in the disengaged position of the bypass assembly, the overrunning mode of the freewheeling unit is enabled such that the clutch assembly is configured for unidirectional torque transfer from the input race to the output race;
• and
• wherein, in the engaged position of the bypass assembly, the overrunning mode of the freewheeling unit is disabled such that the clutch assembly is configured for bidirectional torque transfer between the input and output races.

A rotorcraft comprising:

• a main rotor coupled to a main drive system including a main engine;
• a secondary engine;
• and
• a failsafe multimode clutch assembly positioned between the main drive system and the secondary engine, the clutch assembly including:
• a freewheeling unit having an input race coupled to the main drive system and an output race coupled to the secondary engine, the freewheeling unit 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 having an engaged position in which the bypass assembly couples the input and output races of the freewheeling unit and a disengaged position in which the bypass assembly does not couple the input and output races of the freewheeling unit;
• and
• an actuator assembly configured to utilize a pressurized lubricating oil to generate an engagement signal that biases the bypass assembly toward the engaged position and a disengagement signal that biases the bypass assembly toward the disengaged position;
• and
• a lock assembly in fluid communication with the engagement signal, the lock assembly enabling actuation of the bypass assembly when the engagement signal is present and disabling actuation of the bypass assembly when the engagement signal is absent;
• wherein, in the disengaged position of the bypass assembly, the overrunning mode of the freewheeling unit is enabled such that the clutch assembly is configured for unidirectional torque transfer from the input race to the output race;
• and
• wherein, in the engaged position of the bypass assembly, the overrunning mode of the freewheeling unit is disabled such that the clutch assembly is configured for bidirectional torque transfer between the input and output races.