Precision bearings boost defence aircraft performance

Maintaining these assemblies requires tooling that supports controlled installation, reliable verification, and careful removal. As a specialist bearing and tooling supplier CARTER MANUFACTURING works closely with engineering and maintenance teams to identify the best bearing and tooling options to suit their components and maintenance requirements. In this article we focus on bearings for defense and fixed wing aircraft applications, whilst highlighting the important benefits of Spherical Plain Bearings.

Defense aircraft

Bearings are critically important in defense aircraft applications because they reduce friction, manage extreme loads, and ensure absolute reliability under harsh combat and extreme environmental conditions. Bearings really matter in military aviation as they play a crucial role in Friction and Heat Reduction, allowing high-speed rotating parts, such as turbine shafts to spin smoothly, while minimizing heat build-up and power loss. Load handling is also critical as bearings absorb massive radial and axial forces during sharp manoeuvres, high-G turns, acceleration, and landing impacts. Ultimately Safety and Mission Success can depend on single bearing failure which could cause catastrophic engine or flight control failure.

Fixed wing aircraft

Typically, bearings are not part of the structural aircraft wing (which relies on metal or composite spars and ribs). Instead, bearings are used wherever moving parts or control surfaces interact with the wing.

For example, Flaps and Slats, where actuators and tracks use roller, ball, and spherical plain bearings to extend and retract high-load surfaces. Also, Ailerons and Spoilers, where hinge points, pushrods, and cable pulleys use control-surface bearings (like needle or spherical rod ends) to pivot smoothly. Fuel Systems and Pumps usually feature internal mechanical components, or cooling fans which incorporate miniature bearings.

The benefits of spherical bearings

These are particularly valuable in aircraft assemblies where a joint must carry substantial loads while allowing pivoting movement or accommodating angular misalignment. Unlike ball or roller bearings, they operate through sliding contact between spherical surfaces. This makes them well suited to connections that oscillate through a limited range of movement, including flight-control mechanisms, structural attachments, and landing gear assemblies. In fixed-wing aircraft, spherical plain bearings are used in flight control linkages and actuator attachments. They enable the connections to articulate as control mechanisms move, while transmitting the forces needed to operate the relevant control surfaces.

Landing gear

This is another important application. Bearings within joints are used in flight-control linkages and accommodate the changing geometry associated with extension and retraction, while carrying loads through the assembly. Their ability to accommodate angular movement also helps to address alignment changes under load.

Spherical plain bearings can also be used in wing-to-pylon and engine-to-pylon attachments. In these locations, they provide a load-bearing connection that accommodates angular misalignment within the mounting arrangement, while selected engine accessory attachments use similar principles to support equipment connections. The precise bearing type and arrangement vary between aircraft designs, making application specific tooling selection essential.

Helicopters

Helicopter rotor systems present demanding conditions involving repeated movement, vibration, and cyclic loading. Spherical plain bearings are used in main rotor pitch-control links, allowing the connections to articulate as the control system changes blade pitch. These joints must transmit control forces while accommodating the relative movement of connected components. Bearing condition and correct installation are therefore important considerations during inspection, repair, and overhaul. Spherical plain bearings are also found in helicopter airframe flight-control systems on wheeled aircraft and landing-gear assemblies. As with fixed-wing applications, the bearing arrangement and maintenance requirements depend on the individual platform.

Controlled installation

Installing a spherical plain bearing requires careful attention to the bearing, housing, and specified retention method. Accurate alignment and the correct application of force help protect both the bearing and the surrounding component. Where retention involves swaging or staking, suitable tooling is needed to form the retaining feature in accordance with the applicable engineering instructions. Housing geometry, material, access, and bearing dimensions all influence tool selection. Carter supplies UNASIS installation tooling to support these requirements, working with customers to identify a solution appropriate to the assembly and the prescribed process.

Testing the installed assembly

Once a bearing has been installed and retained, the relevant engineering or maintenance instructions may require checks of its retention and operating characteristics. Depending on the application, these can include proof-load testing to assess retention and rotational torque testing to check resistance to movement. The required loads, limits and acceptance criteria must come from the applicable component documentation.

UNASIS testing tools supplied by Carter support these verification activities, helping maintenance teams establish a consistent process from inspection. 

Careful removal during repair and overhaul

Removing a bearing can be challenging, particularly when it’s retained within a valuable housing or positioned in an assembly with restricted access. Purpose-designed removal tooling helps engineers control the operation and minimize the risk of damage to surrounding features. The appropriate method depends on the bearing location, retention arrangement, and component geometry. Considering removal alongside installation and testing, allows workshops to prepare for the complete maintenance task, supporting efficient repair and overhaul processes.

Application led support

Although spherical plain bearings share a common operating principle, their applications across aircraft and helicopters differ considerably. A flight-control linkage, landing-gear component and rotor pitch-control link each present distinct requirements for access, loading, retention, and inspection. Carter works with customers to understand these details and identify suitable UNASIS tooling. By combining bearing knowledge and tooling requirements together, the company supports engineering teams undertaking critical aerospace and defense maintenance work. Whether the requirement concerns an individual component or a repeat workshop process, the focus remains the same: appropriate tooling, controlled operations, and consistent results.

www.carterbearings.co.uk