From aircraft flight controls, landing gear and wings to helicopter rotor pitch-control systems, bearings play an essential role in transferring loads while allowing components to move accurately. 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 defence and fixed-wing aircraft applications, whilst highlighting the important benefits of spherical plain bearings.
Defence aircraft
Bearings are critically important in defence aircraft applications because they reduce friction, manage extreme loads and ensure reliability under harsh combat and extreme environmental conditions.
In military aviation, bearings play a crucial role in friction and heat reduction, allowing high-speed rotating parts, such as turbine shafts, to spin smoothly while minimising heat build-up and power loss. Load handling is also critical, as bearings absorb substantial radial and axial forces during sharp manoeuvres, high-G turns, acceleration and landing impacts.
Ultimately, safety and mission success can depend on a single bearing, the failure of 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, flap and slat actuators and tracks use roller, ball and spherical plain bearings to extend and retract high-load surfaces. Aileron and spoiler hinge points, pushrods and cable pulleys use control-surface bearings, such as needle bearings or spherical rod ends, to pivot smoothly. Fuel systems and pumps usually feature internal mechanical components or cooling fans that incorporate miniature bearings.
The benefits of spherical plain bearings
Spherical plain bearings 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
Landing gear is another important application. Bearings within joints 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 and, on wheeled aircraft, 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 inspection process.
Careful removal during repair and overhaul
Removing a bearing can be challenging, particularly when it is retained within a valuable housing or positioned in an assembly with restricted access. Purpose-designed removal tooling helps engineers control the operation and minimise 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 from Carter
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 with tooling requirements, the company supports engineering teams undertaking critical aerospace and defence 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.
Find out more at Carter Manufacturing’s defence industry page.
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