What is the purpose of the PTU?

What is the purpose of the PTU?

• A. To allow Yellow system to pressurize Green system or vice versa
• B. To isolate Yellow from Green
• C. To vent hydraulic fluid
• D. To provide electrical power to Yellow

Answer: (A)

In the A320 hydraulic system there are two independent circuits: Green and Yellow. The Power Transfer Unit is a bridge between these two circuits. Its job is to automatically allow hydraulic power to move from the healthier system to the weaker one when a pressure difference exists, so that the other system remains pressurized enough to operate essential controls. Practically, if the pressure in one system drops while the other remains charged, the PTU engages and effectively uses the higher-pressure side to drive a small transfer pump, pressurizing the lower-pressure side. This cross-connection helps keep flight controls and other critical actuators working even if one hydraulic system loses power. It’s not about venting fluid, isolating systems, or supplying electrical power—those aren’t functions of the PTU.

In the A320 hydraulic system there are two independent circuits: Green and Yellow. The Power Transfer Unit is a bridge between these two circuits. Its job is to automatically allow hydraulic power to move from the healthier system to the weaker one when a pressure difference exists, so that the other system remains pressurized enough to operate essential controls.

Practically, if the pressure in one system drops while the other remains charged, the PTU engages and effectively uses the higher-pressure side to drive a small transfer pump, pressurizing the lower-pressure side. This cross-connection helps keep flight controls and other critical actuators working even if one hydraulic system loses power.

It’s not about venting fluid, isolating systems, or supplying electrical power—those aren’t functions of the PTU.