Occurrence
On 11 October 2013, while performing scheduled maintenance tasks including battery removal at a maintenance organization located at Warsaw Chopin Airport (EPWA), a mechanic noticed a fluid leak in the area of the left and right main landing gear wheels. After a detailed inspection, it was determined that both the left and right brake assemblies were leaking. Checking the brake fluid level showed no fluid in the sight glass.
Investigation
Verification of historical records from the continuing airworthiness management indicated an increasing trend of such malfunctions. The operator considered it necessary to perform additional work and inspections of the brake system. These tasks were contracted to a maintenance organization not involved in the original fault. The work was completed, and the aircraft returned to service.
During the investigation, several possible causes were considered:
- Improper operation: The manufacturer had issued a communication regarding brake system malfunctions, advising crews not to overuse wheel brakes for directional control, but rather to use propeller thrust.
- Quality of parts: The possibility that poor quality parts contributed to the malfunctions was dismissed.
- Repair correctness: The possibility that incorrect repairs contributed to the malfunctions was dismissed.
Given the analysis and the absence of a technical cause, the most probable cause was determined to be improper operation, specifically excessive use of wheel brakes during taxi, takeoff, or landing, leading to overheating of the system, seal damage, and fluid leakage.
Probable Cause
The probable cause of the event was improper operation, i.e., excessive use of wheel brakes during taxi, takeoff, or landing.
Preventive Actions
No preventive actions were taken by the investigating entity, and no safety recommendations were issued by the commission.