McDonnell Douglas Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Inflight Event / Encounter Fuel Issue
Flight Crew Diverted; Flight Crew Landed As Precaution; General Declared Emergency
Procedure; Aircraft
The flight began with MEL 28-22-01-01-A Fuel Tank 1 Aft Pump Inop with direction to run the FSC in Auto and to add 2;000 LBS of fuel as MEL penalty. On climbout; received a Level 1 alert MAIN TANK PUMPS OFF and observed on the synoptic; tank 1 pumps off; transfer pump on and crossfeed open. Cycled the FSC from Auto to Manual to Auto and the system fixed itself; returning to tank to engine operation. Later in flight; at cruise; received a Level 1 alert ENG 1 SUCT FEED and observed on the synoptic; all pumps off and crossfeed closed. Put FSC in Manual and the system returned to tank to engine operation; decided to continue flight in Manual; suspecting trouble with the FSC. At FL370; approaching ZZZ; received a Level 1 alert TNK 3 TIP TRAPPED (5;800 LBS unusable) and shortly thereafter another alert TNK 3 FUEL QTY LO. Taking into account the fuel status and the distance/time/fuel burn remaining to destination; the decision was made that landing at the nearest suitable airport was the safest course of action. ZZZ was the nearest suitable airport. An emergency was declared to ensure priority handling and the descent; approach and landing was uneventful. This was a fuel problem that developed as a result of a Fuel MEL and multiple fuel system malfunctions. Adding additional fuel in anticipation of multiple fuel malfunctions is an alternative; but operationally; probably not cost effective.
Approximately 2+30 (FL370) in to the flight the crew received a Level 1 TANK1 SUCT FEED alert at which time the crew selected the fuel synoptic and noticed all boost pumps off and no transfer or X-feed open. Crew selected Manual and observed that the forward boost pump was once again operating. At this point the crew elected to keep the Fuel System in Manual. In relative quick succession after the aforementioned abnormality; the crew received a Level 1 TANK 3 TRAPPED (5;800 LBS) alert with an associated Level 1 TANK 3 FUEL QTY LO alert. Discussion between the crew was utilized and the ultimate decision to declare an emergency and divert to ZZZ. Ensure that significant fuel abnormalities are repaired in a timely matter.
Air Carrier flight crew reports departing with a deferral for Fuel Tank 1 Aft Pump Inoperative with direction to run the FSC in Auto and to add 2;000 LBS of fuel as MEL Penalty. During the next two and one half hours of flight multiple valve and pump anomalies are observed and corrected by placing the FSC to manual then back to auto; then finally leaving it in manual. When an alert is received for trapped fuel in number three tip tank the crew elects to divert.