The Zenit 3-SL (Sea Launch) launch failure which caused the total loss of the Intelsat 27 communications satellite was caused by a fault in the rocket’s steering system. A failure investigation, whose conclusions were confirmed by a Failure Review Oversight Board (FROB), found that first stage hydraulic power supply unit (BIM) used to pressurize the RD-171M main engine gimbal actuators had failed approximately 3.9 seconds into the flight. This was due to abnormal performance of the pump whose function is to pressurize the hydraulic oil supplied to the RD-171M main engine gimbal actuators.
The pump failure was described to be ”the result of contributing factors associated with a pump manufacturing process that proved difficult to control.” The launch failure resulted in payout for insurance loss of $406 million. Corrective actions are now being implemented to allow the Zenit 3-SL (Sea Launch) to return to operation on behalf of the launch provider Sea Launch.