Brake accumulators play a critical role in maintaining braking capability during hydraulic system failures in civil aircraft. Detecting faults in these accumulators is challenging because they serve as backup devices, making their status obscure under normal conditions when the main system is operational. This paper introduces an analytical method that leverages flight test data to detect the fault of brake accumulators. Analyzing the rate of pressure change post hydraulic cut-off reveals a direct, quantifiable indicator that correlates with accumulator condition. Study on specific flight test data shows that marked deviations in this measure can signal potential malfunctions. The approach not only enhances the capability to detect hidden faults but also supports the development of improved maintenance strategies for civil aviation safety.