What is the purpose of the PTU?

The purpose of the Power Transfer Unit (PTU) is to facilitate the transfer of hydraulic pressure between the green and yellow hydraulic systems. In the event of a failure or loss of pressure in one system, the PTU ensures that the other system can provide hydraulic pressure to maintain essential aircraft functions. This interconnectivity allows for redundancy and operational reliability, particularly during critical situations.

The PTU is designed to operate when there is a significant pressure differential between the two systems, enabling the green hydraulic system to assist the yellow system or vice versa, depending on which is experiencing a drop in pressure. This capability is crucial for maintaining control surfaces and other hydraulic systems even if one line encounters issues, thereby enhancing overall safety and aircraft performance.