In what state is the second FADEC during primary mode of operation?

During the primary mode of operation of a Full Authority Digital Engine Control (FADEC) system, the second FADEC is in a standby state. This design is essential for ensuring redundancy and reliability in engine control systems. The primary FADEC is responsible for managing the engine's functions and performance, while the second FADEC remains on standby to take over in the event of a failure or malfunction of the primary unit.

Maintaining the second FADEC in standby allows for quick switching in response to any issues without significant interruption to engine performance. This redundancy is critical for safety, especially in aviation applications where engine reliability is paramount. The other choices reflect conditions that do not accurately describe the operational state of the backup FADEC during the primary mode; thus, standby is the most appropriate and accurate designation for its condition.