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Understanding the Power Transfer Unit (PTU) in Aircraft

Aircraft are amazing features of engineering, featuring numerous intricate systems working together to achieve safe and efficient flight. One crucial component in these systems is the power transfer unit (PTU), that of which is often overlooked despite its critical role. 

The Heart of Hydraulic Systems

The power transfer unit is a vital component of an aircraft's hydraulic system. This system controls various crucial functions, such as the extension and retraction of landing gear, wing flap adjustment, and movement of control surfaces like ailerons and rudders. To understand the PTU's role, we must first grasp the fundamentals of hydraulic systems in aircraft.

Hydraulic systems use fluid power to transmit force and motion, and the aviation industry employs these systems because of their reliability and ability to handle high loads. Hydraulic fluid, typically a special type of oil, is pressurized and used to actuate various components in such systems. Meanwhile, the PTU comes into play when there is a need to transfer power between two separate hydraulic systems.

Bridging the Gap

In an aircraft, there are typically two main hydraulic systems: system A and system B. Each of these systems serves as a backup for the other, ensuring redundancy and safety. However, there are situations where one system may require hydraulic power from the other. This is where the power transfer unit comes into action.

Imagine a scenario where the hydraulic system responsible for extending the landing gear (system A) encounters an issue or runs low on pressure. In such cases, the PTU bridges the gap. It transfers hydraulic power from the functioning system (system B) to the one in need (system A). This ensures that critical functions like landing gear extension and retraction can still be performed even if one hydraulic system faces difficulties.

The Inner Workings of a PTU

With this basic understanding of PTUs, one may ask how a power transfer unit accomplishes this task seamlessly. To answer this, we will provide a step-by-step process for how PTUs operate:

  1. Detection: When a discrepancy in hydraulic pressure between the two systems is detected, the PTU springs into action.
  1. Electric Pump Activation: The PTU electrical pump is then activated, and it starts drawing hydraulic fluid from the high-pressure system (system B).
  1. Hydraulic Valve Control: The hydraulic valve within the PTU is engaged. It directs the pressurized hydraulic fluid from the electric pump toward the system in need (system A).
  1. Equalization: As hydraulic fluid flows into system A, pressure equalizes, allowing the system to function correctly.
  1. Monitoring: The PTU then monitors both systems' pressure levels, and once equilibrium is achieved, the PTU deactivates the electric pump and hydraulic valve.

Ensuring Aircraft Safety

The power transfer unit is critical to aircraft safety and reliability, ensuring that even in challenging situations, essential functions like landing gear deployment and flap adjustments can be carried out smoothly. This redundancy is a key factor in aviation safety, providing a backup plan in case of hydraulic system failures.


As covered in this blog, the power transfer unit (PTU) is a remarkable piece of engineering that plays a pivotal role in aircraft functionality and safety. By transferring hydraulic power between systems, it ensures that essential operations can proceed without a hitch. If you are in the market for PTU components that you can trust, look no further than Civil Aviation 360.

We invite you to explore our wide selection of products anytime and use our online RFQ service to request quotes for items you are interested in. Once we receive a submitted form, we will respond within 15 minutes to provide a tailored solution for your comparisons. Start your purchasing process today and experience why Civil Aviation 360 is the company of choice for many customers seeking optimal part fulfillment.



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