What happened
On October 11, 2013, during routine maintenance procedures involving the removal of a battery, a mechanic at a maintenance organization located at Warsaw Chopin Airport (EPWA) identified a fluid leak near the left and right main landing gear wheels. Upon closer inspection, the technician determined that both the left and right brake assemblies were leaking. A subsequent check of the fluid levels revealed that the brake fluid was completely depleted, as indicated by the empty level inspection window.
Review of historical airworthiness records indicated an increasing trend in similar brake-related malfunctions. In response, the operator ordered additional inspections and maintenance work on the braking system. These tasks were assigned to a different maintenance organization, and once the work was completed, the aircraft returned to service.
The investigation
The investigation, conducted by the user's investigation team, examined several potential causes for the leak. The investigators evaluated whether the issue stemmed from improper maintenance, the quality of components, or operational practices. The investigation ruled out the possibility that the leak was caused by poor-quality parts or incorrectly performed repairs.
Findings
- The investigation identified improper operation as the primary cause of the failure.
- Specifically, the crews were found to be excessively using the wheel brakes to assist with directional changes and maintaining heading during taxi, takeoff, or landing, rather than utilizing propeller thrust for these maneuvers.
- This excessive use of the brakes led to overheating of the braking system, which ultimately caused a seal failure and the subsequent fluid leak.