When is the PTU inhibited?

The Power Transfer Unit (PTU) is inhibited under specific conditions to prevent unintended operation. The correct scenario involves the nose wheel steering disconnect pin being engaged and one engine master switch being on. This situation indicates that the aircraft is in a particular state where the PTU is not required, typically during specific phases of ground operation where it is necessary to minimize hydraulic system interactions and prevent damage or malfunction in the hydraulic systems.

Understanding when the PTU is inhibited is crucial for maintaining the proper function of the aircraft's hydraulic systems. Other scenarios outlined, such as having the parking brake off and both engine master switches on or just one engine master switch on without the nose wheel steering disconnect pin, do not inhibit the PTU, which means the PTU would be active when it might not be needed, possibly leading to complications in hydraulic performance or even system isolation issues.