Overweight Departure and Initial Fuel Issues
The aircraft departed overweight for a 17-hour ferry flight. Early in the flight, the crew experienced some fuel problems but decided to continue after resolving the issue. The crew reported that en route winds were close to forecast.
Fuel System and Transfer Challenges
The ferry fuel system consisted of a simple 5-tank gravity fuel feed into the fore and aft main tanks. About 6 hours from destination, the crew realized the ferry tanks were not flowing into the main tanks as planned. They began manually transferring fuel from the rear ferry tank to the forward ferry tank and shut down the right engine to reduce fuel consumption. However, this did not stop the negative fuel flow from the main tanks.
Ditching and Center of Gravity Concerns
At the time of ditching, the crew estimated that about 170 gallons of fuel remained in the ferry tanks, most of which was in the three aft ferry tanks. An aero engineer calculated that the aircraft was at least 10 inches behind the maximum aft center of gravity (CG) at the time of ditching. The engineer suggested that the ferry fuel system was not managed to maintain the CG within allowable limits, a task made more difficult by the rear fuselage cargo.
Probable Cause
The probable cause of the intentional ditching was the flightcrew's failure to properly manage the fuel system and operation of the airplane in an excessively overweight condition.