Which component is used to manually activate the RAT?

The component used to manually activate the Ram Air Turbine (RAT) is the RAT MAN ON switch. This switch is specifically designed to deploy the RAT in the event of a total loss of electrical power in order to provide emergency hydraulic power and essential electrical power to the aircraft systems.

When activated, the RAT extends into the airstream and generates hydraulic pressure and electrical power that are critical for maintaining some level of aircraft control and operations. This switch is an essential part of the aircraft’s emergency systems and demonstrates how the aircraft can maintain functionality even in critical situations.

The other options mentioned do not serve this specific purpose. The PTU switch is related to the Power Transfer Unit, which assists in hydraulic system pressure but does not deploy the RAT. The hydraulic fault switch deals with hydraulic system failures but does not activate the RAT. The emergency power switch is related to managing the overall power supply in emergencies, but it does not directly activate or deploy the RAT. Therefore, the RAT MAN ON switch is the definitive choice for this function.