Aircraft Hydraulic System Parts and Maintenance

If you are an aircraft enthusiast with an interest in Beechcraft, Cessna, Citation, Piper, Cirrus, or Diamond aircraft, then you are in the right place.

At AAI, we overhaul and exchange aircraft accessories (especially hard-to-find accessories) for these aircraft brands, which means we have an insider’s view that very few people in the entire world get to see.

We get an up-close look at the wear and tear created by years of use and hours of flight time. We see the problem parts that are prone to failure, we see the high performing parts that rarely have issues, and we see everything in between.

So, if you are an aircraft enthusiast (whether you own a private aircraft, are an aircraft mechanic, a pilot, or maybe just have dreams of flying someday) then you will find valuable information in our blog series, An Insider’s Guide to Airplane Parts and Maintenance.

Here are all the articles in the series so far:

Part 1 – Aircraft Fuel System Parts and Maintenance

Part 2 – Aircraft Hydraulic System Parts and Maintenance (this article)

Part 3 – Flight Control System Maintenance: Trim Tab and Flap Actuators 

Part 4 – Aircraft Landing Gear Repair and Overhaul

Part 5 – Pneumatic Systems – Vacuum System and De-ice System Maintenance

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What is an aircraft hydraulic system?

An aircraft’s hydraulic system delivers force from a hydraulic pump to piece of equipment using hydraulic fluid. Depending on the amount of pressure needed, the hydraulic system may generate power from an electric pump (sometimes referred to as a power pack) or may tap into power from the aircraft’s engine via a mechanical pump for higher levels of pressure.  The pressure generated to create the hydraulic force is measured in pounds per square inch (psi), and can reach levels as high as 3,000 psi.

The major parts involved in a hydraulic system are the hydraulic pumps or power packs generating the hydraulic pressure, and the aircraft accessories utilizing the pressure, such as landing gear actuators, landing gear selector valves, uplock sequence actuators and flight control actuators. Other accessories that utilize hydraulic pressure are shimmy dampeners (or dampers), brake master cylinders, and parking brake valves.

The Aircraft Owners and Pilots Association (AOPA) has a fantastic diagram that illustrates the hydraulic system parts and the process of creating and delivering hydraulic pressure.

The AAI insider’s guide to landing gear actuators.

Actuators are designed to convert hydraulic pressure into movement of a specific component or part of the aircraft. When the hydraulic fluid enters the actuator, it forces a sliding component in a specific direction. Actuators control the back-and-forth movement of these parts by sending the hydraulic pressure to one side of the actuator or the other. Landing gear actuators will both lower and raise the landing gear of the aircraft.

As the professional team that overhauls aircraft hydraulic system parts, we recommend checking the landing gear actuator on a regular basis for leaks, corrosion, or other issues.

We mentioned in Part 1 of this series that manufacturers do not provide much information, data, or guidance on aircraft fuel system parts, and the same holds true for hydraulic system parts. Manufacturer support is low, in general, and trying to find technical data can be difficult.

The AAI insider’s guide to aircraft hydraulic pumps and power packs.

Hydraulic systems on smaller aircraft made up of components that do not require a great deal of force to operate are likely to be driven by an electric pump, often referred to as a power pack. These systems should be inspected regularly since they are not driven by the main aircraft engine and can easily be overlooked.

Like electric fuel pumps, the power packs connected to hydraulic systems only operate sporadically. They aren’t designed to run continuously. So, even in instances where a failure doesn’t equate to an emergency, it is still quite important to keep the aircraft well-maintained and functioning properly. This will prevent related issues from popping up that may cause more costly damage to the aircraft. When repairs are missed or if only basic repairs are performed on worn or failing parts, the longevity of the aircraft will be compromised.

AAI provides FAA certified repairs on aircraft hydraulic pumps, power packs, landing gear actuators, and other hydraulic system components.

Corrosion tends to be the worst problem with hydraulic systems (even worse than with fuel systems). At AAI, we commonly receive hydraulic actuators in for leaks and are able to identify more severe root causes that can be fixed and fully restored. Instead of just replacing seals, we perform detailed inspections to ensure parts are ready to be put back into service.

We have developed specialized repairs such as re-chroming piston rods and re-boring cylinders that restore hydraulic system parts to like-new or better-than-new condition. In fact, many aircraft accessory suppliers send their parts to us for these specialized repair and reconditioning services.

For us, it’s all about keeping aircraft optimally maintained with certified replacement parts. We want to help pilots and aircraft owners avoid the illegal activity of mechanics who attempt DIY repairs or parts suppliers who sell uncertified parts.

AAI is an FAA certified repair station servicing Beechcraft, Cessna, Citation, Piper, Cirrus, and Diamond aircraft accessories. We get you the parts you need to maintain your aircraft so that you can get your plane fixed quickly and get back to flying!

We hope this article is both entertaining and educational. Here’s to safe and happy flying!

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