A321
Flight Crew Air Transport Pilot (ATP)
Confusion; Troubleshooting; Human-Machine Interface; Time Pressure
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Weight And Balance; Inflight Event / Encounter Fuel Issue
Flight Crew Diverted; Flight Crew Landed As Precaution; General Maintenance Action; General Declared Emergency
Procedure; Aircraft
Conducting an OE flight for a new Captain; we were nearing our TOD when we noticed a green memo 'FOB LESS THAN 6600 lbs'.  We had sent position reports and kept a fuel log with FOB approximately 600 lbs above our projected TOTAL FOB.  I immediately went to the fuel page and noticed that our wing tanks were down to approximately 5000 lbs. of usable fuel.  [The OE] Captain was flying and immediately recognized that the ACT [Additional Center Tanks] were locked out; and not transferring fuel forward.  We had NO related ECAM warnings or failures. Realizing the severity of this situation; we decided to head toward the nearest suitable field.  I selected 'nearest airports' from the data page; and we headed toward ZZZ.  I called [Maintenance Control] and after some time; they said I had a procedure for this in my QRH.  We had no ECAM; and we were descending to land ASAP; thus my limited time did not allow me to properly look through every reference concerning a fuel failure of the ACT tanks.[My OE] Captain had a similar problem the previous day; with an associated ECAM; that directs the crew to select FWD on the fuel panel; near the ACT pumps; thus 'pushing' the fuel forward.  He did this; but still we had no transfer of fuel; as he did the previous day with his associated ECAM.  This action was taking place during the descent; while setting our altimeter; thru transition; while changing our destination; selecting a runway change as the winds were shifting; and my IPAD suddenly said I had less than 10% power remaining!  I was then connecting my backup battery; and an altitude warning horn brought my attention to a discrepancy of approximately 1000 ft.  I had a message to consider selecting air data on 3; which I did; but this didn't fix that problem so we compared to the STBY; and with air traffic control; thus confirming our proper altitude of 15;000.  My altimeter was incorrect; thus ruled out for the remainder of the flight.  Upon talking to the fueler [he advised] that the ACT transfer switches were found with the guards open and the transfer valves open.  This essentially locked out the operation of the ACT tanks; and inhibited any ECAM warnings from occurring. The altimeter error was caused by pilot error; during a very high task loading event.  I had set 28.96; instead of 29.86; thus causing a 1000 ft error; but we did eliminate the use of this altimeter; almost immediately.
We must ensure that these ACT fuel transfer valves...on the fueling panel are in the correct position prior to leaving the gate.
An A321 flight crew was surprised to receive an ECAM memo of 'FOB LESS THAN 6600;' much below that required; despite regular previous howgozits of fuel in excess of that planned. They soon determined that they had no access to the fuel in the ACT (Additional Center Tank) which should have fed into the center tank as it emptied.  They diverted; whereat a fueler discovered the transfer mechanism was improperly configured; preventing fuel transfer from the ACT to a tank accessible by the engines.