Regulations & Safety
Why Proper Maintenance of Aircraft Wheel Bearings Is Critical for Safety
Airbus technical data shows aircraft wheel bearing failures result mainly from maintenance errors. Proper torque, cleaning, and lubrication are essential for safety.
This article is based on technical guidance and safety publications from Airbus and additional industry safety reports.
Aircraft wheel bearings are among the most stressed components in aviation. Despite supporting loads of up to 500 tons and enduring temperature shifts from sub-zero cruising altitudes to the intense heat of braking, they remain largely hidden from view. According to a technical safety publication by Airbus, the failure of these components is rarely due to design flaws but is almost exclusively the result of improper maintenance.
At AirPro News, we have reviewed the latest guidance from Airbus’s “Safety First” initiative, alongside broader industry data, to understand why these small components continue to pose significant risks to flight safety. The consensus across manufacturers and regulators is clear: strict adherence to maintenance protocols is the only barrier against catastrophic failure.
The primary cause of bearing failure, as identified by Airbus and industry data, is maintenance error. Specifically, the issues revolve around incorrect torque application, contamination, and inadequate lubrication. Aircraft use “tapered roller bearings” designed to handle both the weight of the aircraft (radial loads) and side-to-side movement (axial loads). When these bearings are mistreated, the consequences are severe.
One of the most critical and frequently misunderstood aspects of wheel installation is the torque procedure. According to Airbus technical guidelines, a specific “double-torque” method is required to ensure the bearings are seated correctly without being overtightened.
The process generally involves three distinct steps:
The risk lies in the details. If a technician skips rotating the wheel during the initial torque application, the rollers may not align, leading to a false torque reading. This can result in loose bearings that vibrate and wear prematurely, or tight bearings that overheat and seize.
The failure of a wheel bearing is not merely a maintenance inconvenience; it is a direct threat to the structural integrity of the aircraft. When a bearing seizes, it can generate enough friction to weld components together or shear axles, leading to wheel separation.
In one notable case study highlighted by Airbus, an A330 aircraft lost a wheel during takeoff. The investigation revealed that a seized bearing destroyed the axle nut, allowing the wheel to eject from the landing gear. This is not an isolated event. Data from the Transportation Safety Board of Canada (TSB) underscores the prevalence of this issue. “A study revealed 67 occurrences of nosewheel bearing failures on A319/A320/A321 aircraft worldwide between 1989 and 2004.”
— TSB Canada Data
While the Airbus “Safety First” article focuses on their fleet, the physics of bearing failure applies universally. Reports from the UK Air Accidents Investigation Branch (AAIB) detail an incident involving a Boeing 737-800 where a seized bearing generated sufficient heat to compromise the chrome plating and base metal of the axle, causing it to fracture.
Similarly, an investigation into an Embraer EMB-145 (registration G-EMBP) found that moisture contamination due to improper seal installation led to severe overheating and subsequent axle failure. These incidents confirm that regardless of the airframe manufacturer, the root causes, contamination and torque errors, remain consistent.
To mitigate these risks, manufacturers and technical organizations like Timken have established “gold standard” maintenance manuals. The following practices are considered non-negotiable for airworthiness:
The Human Factor in Maintenance
While the technical steps are well-documented, we believe the persistence of these failures points to a human factors challenge. Wheel bearings are “hidden” components; unlike a tire that shows visible tread wear, a bearing often looks pristine until the moment it fails catastrophically. This lack of visual feedback places an immense burden on the maintenance process itself.
In high-pressure line maintenance environments, the requirement to rotate a wheel while torquing it, a process that relies on “feel” and patience, can be a trap for technicians rushing to clear an aircraft for departure. The data suggests that safety in this domain relies less on new technology and more on a disciplined adherence to the basics: cleaning, inspecting, and respecting the torque procedure.
Regulators continue to monitor these risks closely. The FAA has previously issued Airworthiness Directives, such as AD 2012-10-09 for Cessna 560XL aircraft, following reports of brake failure linked to loose bearing components. Furthermore, the FAA Safety Team (FAASTeam) frequently issues alerts reminding operators that “grease is not just grease,” warning that using unapproved substitutes constitutes a violation of FAR Part 43.
Whether operating a General Aviation aircraft or a commercial airliner, the message from the industry is uniform: take care of the wheel bearings, and they will carry the load.
The Hidden Danger in the Gear: Why Wheel Bearing Maintenance Cannot Be Rushed
The Mechanics of Failure
The “Double-Torque” Procedure
Real-World Consequences
Airbus and TSB Canada Data
Cross-Fleet Vulnerabilities
Industry Best Practices
AirPro News Analysis
Regulatory Context
Sources
Photo Credit: Airbus