MD-11
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Aircraft Equipment Problem Critical
Flight Crew Returned To Gate; General Maintenance Action; General Flight Cancelled / Delayed
Aircraft
While parked prior to takeoff and immediately after receiving takeoff clearance from Center (Tower had just closed) we got a Level 2 'TNK WING OVERFILL' alert and complied with QRH. However; the fuel tanks were at just over 30K pounds which is not even close to full capacity. With Fuel System in auto we noticed the quantity decreasing in #1 fuel tank followed by the #1 fill valve opening and refilling from the #3 tank. Subsequently the quantity began to decrease again and we realized that our total quantity had decreased a few thousand pounds more than it should have during the short taxi (from 96.4K to approx 92K). We called Maintenance to request an immediate visual inspection to determine if fuel was venting overboard. We told the Ramp Office to notify the Fire Dept in the event of fuel spillage. A few minutes later Maintenance arrived and told us to pull the #3 Fire Handle because they thought there was an engine fuel leak. When they determined fuel was venting overboard under the right wing they told us to shut down all engines. We shut down #1 & 3 engines while starting the APU and then shut down #2 engine after APU came on line. Maintenance then told us to shut down the APU because fuel was still venting. After shutting down APU fuel venting stopped. The Fire Dept closed the west end of Taxiway A and Maintenance towed us back to the gate. Called Duty Officer to inform him of fuel venting issue. Transloaded to another aircraft and Fire Dept instructed us to back taxi on RWY for takeoff because taxiway was still closed. Cause unknown at this time. Maintenance thinks it may be a ruptured fuel line. To minimize the amount of fuel vented overboard; the QRH Checklist should be revised to determine whether airborne or on the ground and what specific corrective action the FSC is supposed to be taking on the fuel synoptic. On the ground; decreasing quantity with subsequent filling should confirm fuel venting overboard and require immediate engine shut down on the venting side as a minimum.
While waiting for takeoff clearance an MD-11 Captain gets a  Level 2 'TNK WING OVERFILL' alert. The tanks are not close to full; but some fuel is missing; so Maintenance is called and confirms a fuel leak. All engines are shut down and the aircraft is towed back to the ramp.