Which switch on the collective must be depressed to override FD torque limitations?

Which switch on the collective must be depressed to override FD torque limitations?

• A. TRNG SWITCH
• B. AFCS
• C. BIM
• D. CSYNC

Answer: (D)

The key idea is that the Flight Director’s torque limits are there to protect the engine and rotor drive from excessive load. There’s a dedicated switch on the collective that bypasses that protection when you need to run beyond the normal limit, and that switch is the one labeled CSYNC. When you depress CSYNC, you override the FD torque limiter, allowing the Flight Director to command torque beyond the standard cap for special procedures or testing. The other switches don’t serve this purpose. TRNG is for engaging a training mode, AFCS controls the Automatic Flight Control System itself, and BIM is unrelated to bypassing torque limits. Use CSYNC only as required by procedure and with awareness of the potential for over-torque drive.

The key idea is that the Flight Director’s torque limits are there to protect the engine and rotor drive from excessive load. There’s a dedicated switch on the collective that bypasses that protection when you need to run beyond the normal limit, and that switch is the one labeled CSYNC. When you depress CSYNC, you override the FD torque limiter, allowing the Flight Director to command torque beyond the standard cap for special procedures or testing.

The other switches don’t serve this purpose. TRNG is for engaging a training mode, AFCS controls the Automatic Flight Control System itself, and BIM is unrelated to bypassing torque limits. Use CSYNC only as required by procedure and with awareness of the potential for over-torque drive.