How Are Aerospace Bearings Tested for Safety and Reliability

Aircraft rely on bearings within engines, landing gear, flight control systems, and many other assemblies to allow reliable, friction-free motion while often carrying immense loads. Unlike bearings used in other settings, these aviation variants have to be stringently engineered to function in some of the harshest operating conditions imaginable. In this blog, we will look at some of the demanding evaluations these bearings undergo to ensure they perform as intended.

Design and Material Verification

Before a bearing can enter service, its materials and geometry must be validated to confirm that it can endure the mechanical stresses and thermal extremes inherent to flight. A central benchmark in this area is the FAA Technical Standard Order TSO-C149, which establishes the minimum performance requirements for aircraft bearings. Under this order, bearings are tested for:

Hardness, confirming resistance to deformation under load.
Dimensional accuracy, ensuring tolerances match engineering specifications.
Load ratings, verifying the bearing can safely sustain applied stresses.
Wear resistance, assessing durability under prolonged use.

Beyond these baseline checks, bearing life expectancy under load is also crucial, as aerospace bearings are expected to go through countless stress cycles without fatigue. The internationally recognized ISO 281 standard provides the calculation methods for dynamic load rating (C) and static load rating (C0), which together allow engineers to estimate the L10 life, or the number of revolutions that 90 percent of identical bearings are expected to achieve before failure.

Inspection and Non-Destructive Testing

After design and material trials, bearings undergo different forms of inspection to confirm that manufacturing processes have produced parts free of defects. These include:

Dimensional checks that confirm clearances, contact angles, and surface finishes.
Metallurgical evaluations that assess grain structure, hardness consistency, and contamination.
Source Qualification Inspections (SQI) that verify that suppliers can consistently manufacture bearings within aerospace tolerances.
Eddy-current testing, which uses electromagnetic fields to detect cracks and subsurface flaws as small as 0.002 inches. Accuracy in this method relies heavily on proper probe alignment to avoid masking defects or producing false readings, so eddy-current procedures are tightly controlled and carefully calibrated to create reliable and repeatable results.

Functional Testing

Once bearings have passed initial design validation and inspections, they move into an evaluation process that concerns both standard operating stresses and application-specific demands. At this stage, the industry distinguishes between two levels of verification outlined in NASA-STD-5017A:

Qualification testing is performed on representative designs to demonstrate that a bearing can withstand stresses at or above its expected operating range, confirming that it has a sufficient safety margin.
Acceptance testing is carried out for production lots to ensure that every manufactured batch continues to meet the required standards of performance and integrity.

Environmental Testing

Simulations of vibration, shock, temperature extremes, humidity, and corrosive atmospheres are commonly carried out for bearings in alignment with RTCA DO-160 procedures. Although originally written for avionics and airborne equipment, these procedures are frequently adopted in bearing qualification programs to validate durability under environmental stresses.

Beyond these general trials, functional testing reflects how bearings actually operate in the aircraft systems they are made to be used in. For airframe plain and spherical bearings, SAE ARP-5448 prescribes standardized methods for evaluating wear, lubrication performance, load response, and liner bond integrity under simulated service conditions. Testing is usually tailored to the application in question. For example:

Bearings meant for flight control linkages are tested for oscillatory loads.
Landing gear bearings are validated against heavy impact and contamination from dirt or moisture.
Engine bearings are not usually evaluated to ARP-5448, instead matching OEM engine standards with a focus on high-speed and high-temperature operation.

Endurance and Lifecycle Validation

Even after the various forms of testing, aerospace bearings must still demonstrate that they can display long service lives. Therefore, endurance and dynamic load testing are carried out to subject sample populations to repeated cycles of stress, speed, and load, confirming that the predicted lifespans from ISO 281 align with actual fatigue performance.

Purchase Performance-Validated Aerospace Bearings on Emergent Purchasing

In summary, aerospace bearings undergo a multi-stage regime of testing governed by rigorous standards, with each phase building toward the goal of creating the most safe and well-performing parts possible for the rigors of flight. Given this high bar of expectation, sourcing bearings from a reliable supplier is essential. Emergent Purchasing serves as a dependable procurement platform in this endeavor, supplying a wide range of aviation-compliant bearings and other components from trusted manufacturers.

On our database, customers can readily track down what they need through provided search tools and curated catalogs that organize parts by common designations. Moreover, those who shop with us will benefit from more than easy browsing and quality products, as our team strives to present competitive and timely fulfillment options curated to their specifications. With this in mind, get in touch with our staff to see how we can accommodate all your operational needs with ideal sourcing solutions.