B747-400
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 90; Flight Crew Total 16000; Flight Crew Type 2000
Communication Breakdown; Training / Qualification; Human-Machine Interface; Distraction; Confusion
Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance; Inflight Event / Encounter Fuel Issue
Flight Crew Overcame Equipment Problem; General Release Refused / Aircraft Not Accepted; General Flight Cancelled / Delayed
Staffing; Human Factors; Procedure; Aircraft
When we arrived at the aircraft about 1 hour prior to departure; fueling was in progress. I did the walk around; then noticed the fuel truck was still in position but disconnected. In the cockpit I sat in the second observer's seat to do a more detailed logbook review and sign the log page. While I was doing this the First Officer commented that our fuel load was not symmetrical. On looking at the fuel synoptic; all main tank quantities were boxed in yellow and both tank 1 and 4 and 2 and 3 fuel imbalance EICAS messages were displayed. We called Maintenance. The approximate quantities were: Center = 7.0; #1 Main = 22.0; #2 Main = 56.0; #3 Main = 48.0; #4 Main = 17.0; #2 Reserve = 5.0; #3 Reserve = 0.0. Total FOB = 155.0. The [span wise] AOM imbalance limitations are: Tanks 1 vice 4 = 3.0 Tanks 2 vice 3 = 6.0. Also; no center tank fuel is allowed until all main and reserve tanks are full unless the center tank fuel is counted as payload. My thought was to have Maintenance transfer fuel so the center tank was empty and tanks one through four were balanced. This was not to be since the mechanic was not familiar with the transfer procedure. To try and keep things simple; I asked them to add fuel so tanks 1-4 were balanced and to rerun the weight and balance to reflect this and to include the center tank fuel as payload. This would require the addition of about 18;000 LBS of fuel. I then called Dispatch and explained our solution and request a revised flight plan. So far so good; except in the heat of battle I missed the very last bullet point in the AOM fuel loading limitations that the center tank scavenge system must be deactivated when carrying ballast fuel. To avoid this omission in the future; it makes sense to locate this limit in the same paragraph that requires center tank fuel to be counted as payload when all main and reserve tanks are not full. We continued the cockpit setup and soon the Load Supervisor appeared and asked if the fuel load was OK. All was as requested; except reserve tank 3 was indicating 3.0 instead of the 5.0 requested. I asked if the fuel truck was still hooked up and was told 'I don't think so.' I replied it was OK; we would not need additional fuel. At this point; the gateway called saying they had no way to add the center tank fuel as payload. All they had was an entry for Balance Control Fuel (BCF). I told them that was the place. It turns out BCF is added to the ZFW on the matrix and on the ACARS Weight and Balance page. However; the TOGW number is derived by adding payload + BOW (Basic Operating Weight) + fuel. This is correct from a weight standpoint; but it is not the way the aircraft's FMC PERF page works. The FMC derives TOGW by adding ZFW and fuel. This counts BCF twice; once as part of the ZFW and once as part of the fuel load. This caused a good 15-20 minutes of confusion while we tried to understand why the FMC Gross Weight was approximately 10.0 greater than the Weight and Balance program TOGW. The First Officer figured out the Payload + BOW + fuel issue and then I finally caught the approximately 10.0 number was BCF + taxi fuel. We had Operations run the weight and balance again without a BCF entry and everything fell into place; but it is not technically correct. Even though 7;000 LBS is about 1% of our TOGW and likely gets caught in the data scatter; the system integration between the weight and balance program and the FMC has a bug in this area that needs to be addressed. Also; there needs to be a CAUTION by the BCF entry that the center tank scavenge systems must be deactivated when BCF is used. This caution and the BCF amount should be presented on the printout provided to the Captain. Our 7;000 LBS is trivial regarding CG movement; but 70;000 or 100;000 LBS would be a different story. Additional confusion resulted from the fueler not getting closer on the fuel in reserve tank 3. The 2;000 LBS difference threw us out of the matrix resulting in discussions with Operations and Dispatch before the final weight and balance was printed and signed. We blocked out 46 minutes late.
When the fuelers failed to load the required fuel as required for weight and balance compliance the flight crew of a B747-400 was forced to improvise an increase in fuel volume and location that would correct the errors. Upon doing so they failed to recognize and implement the required deactivation of the center tank fuel scavenge system.