B747-400 flight crew reported a divert due to lavatories not being serviced properly prior to departure.
Synopsis
B747-400 flight crew reported a divert due to lavatories not being serviced properly prior to departure.
Narrative
We were doing our cockpit set up checks and preparing to leave airport to go to RJAA. We received the service form from the cockpit printer stating next to lavatory service was not available. We normally see 'completed' after lavatory; so we called and asked them to look into it. After a short time; they responded that not available was entered in error; and that we would receive a new service form. We did; and on the new service form next to lavatory stated completed. The relief pilots stated that the gauges by door 2R looked good. After about 3 hours into the flight; the Purser called stating that the left side of the aircraft lavatories and the forward upper deck had stopped working. We called Dispatch and Maintenance to try to diagnose the problem. We tried to reset the tank that was full but could not. We knew the biggest lavatory tank was full; but did not know for sure how long we could fly before the other tanks would eventually fill up. We made the conservative decision to land at an enroute airport before a bad situation got worse. We had to dump 62;500 pounds of fuel at FL320 so we would not land overweight. The approach and landing was normal and below maximum landing weight. The lavatories were serviced. The people that serviced the airplane said that the main tank was full; but the other three tanks were about 10% full. The indicators at 2R showed more than 10%; but were they accurate? I don't know. When the lavatory service was completed and the aircraft was fueled; we proceeded to RJAA. What went wrong that led to this problem? I don't know. On the surface; it looks like everything was done right. We received a completed service form. The relief pilots said the gauges looked good. What else could we have done? Was there a problem with the gauges? Was there a problem with the person dumping three tanks; not four?
Second reporter narrative
The purser called the cockpit saying: the lavatories on the left side of the aircraft won't flush; the sensor light on the LAV panel was blinking; and the left forward tank was indicating full; and the remaining three tanks were between 1/2 and 3/4 full. I contacted Dispatch and Maintenance. Maintenance had us attempt to reset the sensor light that was blinking; but with no success. We all agreed that with approx 9 hrs flight time; we had no other recourse; but to divert and be serviced. We chose an airport that was on our track two hours ahead. It provided the shortest flight time to RJAA after diversion; weather good and beat possibility of staying within flight attendant duty time. Fuel jettison of 62;500 LBS was required to avoid an overweight landing and required maintenance inspection. However; we were able to wait until we were out of Canadian airspace and back into US airspace before jettisoning to avoid further complications.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.