What is the purpose of having two primary pitch trim channels A and B?

• A. To alternate between channels for load sharing
• B. To provide redundant electrical signals to the primary pitch trim motor
• C. To drive the secondary stand-alone trim motor
• D. To control the speed brake independently

Answer: (B)

Redundancy for a critical control is the main idea here. Having two independent channels provides a backup path for the command to the primary pitch trim motor. If one channel develops a fault, the other channel can still drive the trim motor and maintain the commanded trim, helping prevent trim loss or instability. This setup often includes fault detection by comparing the two channels, so a malfunction can be identified without losing trim function. It’s not about sharing the load between channels or driving a separate trim motor, and it’s not related to the speed brake system.