A Beginner’s Guide to Aircraft Hydraulic System Components

A far cry from early aircraft assemblies that relied on physical strength, cables, and pulleys to manipulate flight control surfaces, modern hydraulic systems present impressive power-to-weight ratios to power numerous tasks with effectively no effort from operators. Since they are central to how most subsystems function, anyone who works with aircraft should have at least a basic understanding of how they are able to achieve their output. In this blog, we will take you through every major element that is responsible for creating a pressurized hydraulic network and accurate end results.

Reservoirs

Every hydraulic system draws from a reservoir that holds the fluid it runs on, but beyond acting as storage, it accommodates the natural expansion and contraction of fluid with temperature changes, provides a space for air bubbles to escape, and helps dissipate heat. Often, the reservoir is also pressurized by engine bleed air to guarantee that a positive flow of fluid is always available, preventing cavitation even during aggressive maneuvers or high-altitude flight.

Hydraulic Pumps

Responsible for driving consistent fluid flow, pumps come in two main configurations to best serve the hydraulic system:

Engine-Driven Pumps (EDPs): The primary source of pressure, EDPs are mounted directly to the accessory gearbox to run as long as the engine does.
Electric Motor-Driven Pumps (EMPs): EMPs are powered by the aircraft’s battery, APU, or generators. They act as backups when an aircraft is grounded and the engines are static or failsafes in the event of an EDP failure.

Furthermore, pumps can be constant displacement variants that move a fixed volume of fluid with every revolution, but most aircraft favor variable displacement options to automatically adjust output in response to demand. By doing so, variable pumps can maintain steady pressure without imposing unnecessary heat buildup or mechanical wear on itself or the other hydraulic system parts.

Accumulators

An accumulator is effectively a high-pressure storage tank, divided into two chambers by a piston, flexible diaphragm, or rubber bladder. One side is filled with hydraulic fluid, while the other contains an inert gas, typically nitrogen. Since gas is compressible and hydraulic fluid is not, it pushes against the already-pressurized fluid to maintain potential energy within the system. In turn, accumulators can:

Mitigate Shocks: When valves open or close rapidly, they create sudden spikes in pressure that can rattle the airframe and attached components, so the gas absorbs these surges to avoid stress.
Provide Emergency Power: If the primary pumps fail, the energy stored in the accumulator allows for a limited number of emergency operations.
Uphold Stability: During periods of high workload, such as when a pilot deploys flaps and landing gear simultaneously, the demand for fluid can momentarily exceed what the pump can supply. In these moments, the accumulator will kick in to provide the extra volume and avoid a temporary drop in pressure that could make control responses sluggish.

Actuators and Selecting Valves

At the end of the system loop, actuators and valves translate generated energy into physical movement at the right time and in the right manner. These include:

Linear and Rotary Actuators: Linear actuators employ a piston-and-cylinder arrangement to create straight-line motion. In contrast, rotary actuators contain a rotating vane or piston to achieve circular movement for tasks like steering nose landing gear, rotating cargo bay door hinges, or adjusting trailing-edge flaps.
Selecting Valves: When a pilot initiates a command, the selecting valve shifts to direct pressurized fluid to one side of an actuator while simultaneously allowing spent fluid to return to the reservoir.
Priority Valves: In case of a partial pressure loss, priority valves automatically isolate non-essential subsystems so vital areas like brake system tube assembly parts or primary flight control surfaces stay fully functional.

Source an Array of Aircraft Hydraulic System Parts with Ease

While hydraulic systems are supported by even more parts than what we covered, such as fluid lines, seals, and filters, the interplay between these main elements is what actually allows them to generate force and facilitate movement. As each aspect is carefully designed to reliably deliver power, you need to have a trustworthy source for high-grade hydraulic hardware when maintenance is due. Aerospace Parts Distributor would be proud to serve as your go-to procurement platform, our inventory containing thousands of ready-to-purchase products from industry leaders like Fluid Components Ltd and others. Knowing that we also benefit our customers with an intuitive website layout, layered quality commitments, and helpful experts that curate competitive fulfillment solutions, we invite you to check out our selection and get in touch to see how else we can serve your operations!