What does the standby hydraulic system use to power the rudder?

The standby hydraulic system is designed to ensure that essential systems, like the rudder, can be operated even in the event of a primary system failure. To achieve this, it typically utilizes a single electric motor-driven pump. This setup allows for reliable and immediate hydraulic pressure to be delivered to the rudder control system, ensuring that pilots have the necessary controls available for safe operation of the aircraft. The use of an electric motor as the power source provides the capability to actuate the hydraulic system independently of other mechanical or hydraulic sources, thereby enhancing the redundancy and safety of the flight control system.

The other options, while relevant to hydraulic systems in different contexts, do not directly provide the necessary powered actuation for the rudder in the standby system. A hydraulic fluid reservoir is crucial for storing hydraulic fluid, but it does not actively power the system. A mechanical backup system might involve alternative methods of control but is not the primary source of hydraulic power. A manual control lever can assist in controlling the rudder, but again, it does not independently supply hydraulic power required for operation in a standby scenario.