What is the purpose of the Power Transfer Unit (PTU) in the Challenger 300/350?

The purpose of the Power Transfer Unit (PTU) in the Challenger 300/350 is to ensure the retraction of the landing gear in the event of a failure of the left engine-driven hydraulic pump. This design feature allows for continued safe operation of the aircraft under circumstances where one hydraulic source has become inoperative, specifically allowing the aircraft to maintain critical functions like landing gear operation.

The PTU achieves this by using hydraulic power from the right engine to assist in providing the necessary pressure to operate the gear mechanism, thereby enhancing the safety of the aircraft and allowing for a reliable landing procedure even in the event of a hydraulic failure. This redundancy in the hydraulic system is essential for maintaining operational integrity and safety in flight.

While other options may pertain to hydraulic functions, they do not specifically highlight the unique role of the PTU in addressing hydraulic system failures related to gear retraction.