With the Tail SERVO switch in BACKUP position, which tail rotor servo stage is pressurized?

With the Tail SERVO switch in BACKUP position, which tail rotor servo stage is pressurized?

• A. 2nd stage, backup hydraulic system
• B. 1st stage, primary system
• C. 2nd stage, primary system
• D. 1st stage, backup system

Answer: (A)

The tail rotor servo is a two-stage hydraulic actuator, and the backup position switches the tail rotor control to the backup hydraulic circuit. In that mode, the second stage of the tail rotor servo is pressurized. This arrangement preserves tail rotor authority if the primary system fails by using the backup pressure to drive the final stage of the servo. The first stage is normally driven by the primary system, so in backup mode it isn’t the stage that’s pressurized. The backup system isn’t energizing the first stage, and the primary system isn’t supplying pressure in this mode.

The tail rotor servo is a two-stage hydraulic actuator, and the backup position switches the tail rotor control to the backup hydraulic circuit. In that mode, the second stage of the tail rotor servo is pressurized. This arrangement preserves tail rotor authority if the primary system fails by using the backup pressure to drive the final stage of the servo.

The first stage is normally driven by the primary system, so in backup mode it isn’t the stage that’s pressurized. The backup system isn’t energizing the first stage, and the primary system isn’t supplying pressure in this mode.