Hydraulic Power Unit Information & Instructional Guide

In airports worldwide, hydraulic power units (also referred to as mules) help ground crews perform critical aircraft maintenance operations to keep their fleets in top conditions. These complex pieces of equipment are vital to operations, but understanding their essential functions can be a challenge if you haven't worked with them before. If you're considering picking up a hydraulic power unit (HPU) from Tronair to meet your commercial, regional or business needs, you'll need to understand how they operate. This article will provide an overview of Tronair hydraulic power units to help customers understand how to use them for daily maintenance operations.

Note: This guide is not exhaustive. Please consult your hydraulic power unit operations manual and ensure you've received the proper training before attempting operation.

What Is Hydraulic Power?

Before we jump into the ins and outs of Tronair hydraulic power units, let's start with the basics – what is hydraulic power and what are hydraulics powered by? In the aviation industry, hydraulic power is used to help aircraft run better, faster and stronger. In technical terms, hydraulic power is transmitted by the circulation of a controlled, pressurized fluid (usually hydraulic fluid in the aerospace industry) to a motor that converts it into mechanical output capable of performing certain operations.

What Is a Hydraulic Power Unit?

Hydraulic power units are among the most commonly used pieces of ground support equipment in the industry. With high power output and a wide range of applications, a hydraulic power unit allows aircraft ground maintenance crews to perform essential preventive maintenance tasks that would otherwise not be possible without starting an aircraft's engines.

Hydraulic power units are typically used for the following aircraft maintenance tasks:

Draining aircraft hydraulic systems
Filtering aircraft hydraulic systems
Refilling aircraft hydraulic systems
Performing checks on hydraulic-driven flight controls after maintenance

How Do Hydraulic Power Units Work?

At Tronair, our hydraulic power units come in various configurations. But despite their differences, all still operate on a standard set of principles. Hydraulic power units rely on multi-stage pressurization networks to move hydraulic fluid. The movement of this enclosed fluid transfers energy to then be converted into mechanical motion.

All hydraulic power units are powered by a motor, which in turn powers the main pump to circulate hydraulic fluid from the reservoir throughout the entire system. When the hydraulic pump has converted the hydraulic energy into mechanical energy, valves will control and direct the fluid flow to provide power to the aircraft.

The Components of a Hydraulic Power Unit

Now that we've discussed the basics of hydraulic power units, let's look at the components that make up these complex machines.

Motor

The heart of the hydraulic power unit is the motor – the primary source of power. Typically, motors are electrically powered. However, a few are gas and diesel-driven for outdoor usage. The motor is responsible for converting electricity or gas into mechanical energy.

Hydraulic Pump

Another prominent component of any hydraulic power unit is the hydraulic pump. The hydraulic pump controls both the flow and the pressure within the unit. Once the electrical power is converted to mechanical power by the motor, the hydraulic pump converts that into hydraulic pressure to be used for aircraft maintenance.

Hydraulic Reservoir

Another essential component of hydraulic power units is the reservoir – the storage area for the hydraulic fluid. Once the pressure and flow are selected, hydraulic fluid will pass through the reservoir into the hydraulic pump to be directed into the aircraft.

Regulators

Hydraulic power unit regulators are the components that control or "regulate" the pressure lines, ensuring they don't become overpressurized and burst.

Relief and Pressure Supply Lines

Relief and pressure supply lines keep the pressure inside the hydraulic power unit level. In other words, these components pump the hydraulic fluid at a set pressure and ensure the fluid is cycling properly. Keeping the pressure level keeps air bubbles from forming inside the unit and keeps the hydraulic fluid inside the tubing pure.

How To Safely Operate a Hydraulic Power Unit

Next, it's time to learn the basics of operation. In this short video, the experts at Tronair take you through the step-by-step process of operating a Tronair TAD Series Hydraulic Power Unit.

In order to operate a hydraulic power unit safely, there are a few safety precautions to keep in mind with every use.

Operators must be adequately trained before hydraulic power unit operation.
The HPU power switch must be in the "off" position when connecting and disconnecting hoses to the aircraft.
Operators must check the pump rotation before starting the unit.
When starting or stopping the hydraulic power unit, the bypass valve must always be in the "open" position.
Operators must disconnect electrical power from HPUs and keep the bypass valve in the "open" position before servicing.
Operators must ensure pressure and return hoses of the same system are paired and used together.

Let Tronair Help You Find the Hydraulic Power Unit That Suits Your Needs

Hydraulic power units are the workhorses of your ground support equipment fleet. They provide auxiliary hydraulic power to your aircraft systems for essential maintenance and repair – without them, your operations would come to a halt. If you're thinking of updating your equipment with a new hydraulic power unit or units, the experts at Tronair have you covered. Not only can we help you find the best HPU for your specific operation or aircraft, but we'll go the extra mile to ensure you understand its operation to the fullest extent. Shop hydraulic power units from the most trusted name in ground support equipment today.

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