What happened
During the final approach phase of flight, the aircraft experienced a dual hydraulic system failure. In response to the loss of pressure, the captain elected to execute a go-around. The crew subsequently diverted to a nearby military airport equipped with longer runways to ensure a safe landing. The landing at the diversion airport was completed without further incident and all occupants were not injured.
The investigation
Investigators discovered that a hole had been chafed through a return line belonging to the 'A' hydraulic system. This chafing occurred at a bracket located within the left wheel well area.
Further examination of the hydraulic architecture revealed that an 'A' system return line and a 'B' system return line had been cross-connected in the vicinity of the No. 1 pylon. This improper connection created a path for fluid from the 'B' system to transfer into the 'A' system, where it then vented overboard through the chafed line.
Prior to the mechanical failure of the line, all hydraulic system indications, readings, and tests had appeared normal. A review of maintenance records was conducted, but investigators were unable to determine when the lines had been reversed during previous service.