Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Aircraft Equipment Problem Less Severe
Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft
We were an hour and a half into our flight. I (the RFO) went back to take first rest period. I saw the FSS (Fire Suppression System) panel was continuously cycling from normal to off (blank) to a red 'FAULT argon pressure' alert. I snapped a picture of it to show the rest of the crew. We began a conversation about the DG (Dangerous Goods) we were carrying and having no back up protection available. We knew the FSS was; at best; not working. At worst; it might be leaking argon into the ship...we could not know its status. It was decided that it was best to return to SYD rather than risk the lives of the crew to proceed for another 6 hours over water with nowhere to land and with DG aboard. The DG included; not just lithium batteries; but flammable solid; liquid; gas; corrosive and more. The Captain ACAR'sed ops and Maintenance Control and also communicated by satcom. Maintenance Control reviewed the FSS history of the ship and found none. The MEL directed the crew to review the FOM. The FOM indicated that without Operational FSS on board the DG could be place in a can and the old system be reactivated or the DG could be removed from the Aircraft. We had DG on a pallet with no way to fight a fire. This was unsafe at best. The issue was this: without an operable FSS; either no DG can be carried aboard the a/c or the old system of a DG container and hoses must be in place. We had neither. The Captain elected for Safety and legality. We considered YBBN as it was closer; but elected SYD. The FO had given ATC a heads up that we likely would return to SYD. We dumped about 42;000 lbs of fuel at FL300 to reduce to below MLW. The FO flew an uneventful approach and landing to R34L SYD. (Maintenance also took photos of the malfunctioning system; as they had not seen it before either. Maintenance also confirmed that it was not safe to fly with the current DG configuration)FSS failed while carrying DG. The fault light (Argon Pressure) came on and off continuously. We had no way of knowing based on the fault light what had failed and what still worked. The Argon gas may have leaked out. The system may have been inop. There was simply no way of determining the level of the failure. This led us to believe that we may not have any ability to detect or fight any type of fire in the cargo area.
I don't think it can be prevented. Systems break. What can be changed though is a better and more thorough understanding of carrying DG. The safety of the aircraft and its crew should never be compromised to take a chance at continuing without firefighting capability. I heard statements like these while we were conferring with Maintenance Control: 'well; maintenance will just defer it and send you back out' and 'we used to not have that system'. Good grief! The folks charged with assisting us need to be better educated about the carriage of DG and how the deferral would have worked had we dispatched with it. When I contact Maintenance Control for assistance in flight; I want a full partner. I don't want to have to teach at that moment.
MD11 flight crew and the Dispatcher involved report on the decision to return to YSSY when the fire suppression system faults enroute with dangerous goods aboard.