“The investigations isolated the failure to the Zenit-3SL first stage hydraulic power supply unit (BIM) used to pressurize the RD-171M main engine gimbal actuators. No additional contributors to the failure were found. The BIM failed approximately 3.9 seconds into the flight due to the abnormal performance of the pump that’s function is to pressurize the hydraulic oil supplied to the RD-171M main engine gimbal actuators. The pump failure was the result of contributing factors associated with a pump manufacturing process that proved difficult to control.”
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