Best Practices for Aircraft Bearing Maintenance

From engines to landing gear, countless aircraft systems depend on bearings to support seamless movement and reduce friction. Aviation bearings are designed to operate with exacting precision, but their constant exposure to heavy loads, extreme temperatures, and continuous motion places them under relentless stress. When these components are not properly maintained, costly repairs or serious safety concerns can spring up. As such, be sure to read on as we guide you through some best practices for inspecting and caring for bearings in this blog.

Inspection and Assessment

Effective bearing maintenance begins with a comprehensive inspection process. This can happen on varying timelines based on the bearing type, application, and airframe, with typical intervals being based on flight hours or major checks. During this step, maintenance personnel should:

Look for surface wear, discoloration, or signs of overheating, which can signal friction-related damage or lubrication failure.
Check for corrosion or contamination, particularly in bearings prone to moisture exposure or debris ingress.
Assess lubrication conditions, as dry, hardened, or discolored grease often indicates extended service use, excessive temperature, or contamination.
Verify smooth rotation during manual checks, since resistance, unusual vibration, or audible noise may point to internal defects or raceway damage.

Non-Destructive Testing

For bearings used in flight-critical systems, visual checks alone are not always sufficient. Non-destructive testing (NDT) is a standard practice to identify subsurface or otherwise hidden flaws before they progress to failure, with common methods including:

Magnetic Particle Inspection: Magnetic particle inspection involves the use of a magnetic field and fine ferrous particles that collect data on where magnetic flux is disrupted by a flaw.
Ultrasonic Testing: Ultrasonic testing employs high-frequency sound waves that travel through the bearing material, where reflections from internal cracks or fatigue damage are detected on specialized equipment.
Eddy Current Testing: Eddy Current Testing induces electrical currents into conductive materials, and any change in current flow caused by a crack, corrosion, or material inconsistency is measured with a probe.

Cleaning and Lubrication

Rolling elements depend on a consistent film of grease or oil to minimize friction and prevent metal-to-metal contact, so lubrication is an imperative part of maintenance. Before relubrication takes place, bearings must be carefully cleaned. This involves:

Removing old grease or oil using manufacturer-approved solvents.
Drying components thoroughly to prevent corrosion.
Avoiding abrasive cleaning methods that could scratch or otherwise damage raceways and rolling elements.
Inspecting surfaces immediately after cleaning to better detect small cracks, pitting, or discoloration that might have been hidden before.

Once these steps are complete, technicians proceed with applying the specific grease or oil listed in the relevant Aircraft Maintenance Manual (AMM) to provide adequate protection and performance based on load, speed, and temperature. Application also needs to be carried out with care, since excessive lubricant can lead to overheating, while insufficient amounts leave rolling elements vulnerable to wear. Moreover, re-lubrication intervals are also established by the manufacturer, with recommendations tailored to the operating environment, duty cycle, and bearing design.

Best Practices for Handling and Installation

While bearings are expertly engineered, their service life can be significantly shortened if proper handling and installation procedures are not followed at every stage of handling and assembly.

Handling

Opt to wear clean gloves when handling bearings to avoid natural oils, dirt, and moisture from transferring from bare hands.
Avoid dropping or striking components, as even small impacts may create dents on raceways that cause fatigue under load.

Installation

Use proper tooling for seating bearings, such as bearing presses or heating plates that allow hardware to be mounted without applying force directly to rolling elements or cages.
In some cases, heating the bearing or cooling the shaft might be recommended to achieve a proper fit, but temperatures must be controlled to remain within manufacturer limits so material properties are not altered.
Ensure shafts and housings are aligned precisely before installation to avoid uneven load distribution across rolling elements, which can result in inefficient operation and accelerated wear.

Documentation and Compliance

Inspections, lubrication procedures, and full replacements all have to be documented in accordance with the operator’s approved maintenance program and the requirements of governing authorities. These practices should involve logging inspection dates, findings, and corrective actions, clearly stating the condition of the bearing. This also extends to tracking lubrication cycles, including the type of lubricant used.

Maintaining thorough documentation means that the service history of each bearing remains transparent and verifiable, demonstrating compliance and airworthiness. Just as important, detailed records of wear patterns, lubrication condition, or vibration anomalies can reveal developing issues. With this information in hand, operators are better positioned to make proactive decisions regarding maintenance scheduling and part replacement.

Secure Reliable Aircraft Bearings through NSN 360

In summary, by following these general maintenance guidelines, operators can keep bearings performing well and prevent unexpected failures, ultimately reducing downtime and upholding the highest standard of safety. If you are in need of replacement bearings for any aircraft system, it is crucial to purchase them in line with stringent aviation standards. ASAP Semiconductor serves as a dependable procurement partner for these needs, offering a wide range of top-quality aviation bearings through NSN 360.

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