What role does the power transfer unit (PTU) play in hydraulic System A?

The power transfer unit (PTU) is designed to provide redundancy in hydraulic systems, particularly in aircraft. Its primary function is to ensure that if one hydraulic system (like System A) experiences failure or reduced performance, the PTU can transfer hydraulic power from a functioning system (such as System B) to maintain overall system functionality. This critical redundancy helps ensure that essential aircraft systems continue to operate safely and effectively during various operational scenarios.

In contrast, options related to supplying hydraulic fluid, manual brake controls, or landing gear retraction do not accurately represent the PTU's primary role. The PTU itself does not directly supply fluid, nor does it handle manual brake operations or control landing gear functions. Its focus is on maintaining operational integrity and safety through the sharing of hydraulic power under certain conditions.