Accident Overview
Approximately 4.3 hours into an overwater flight, the crew reported that only 15 minutes of fuel remained. Shortly thereafter, three of the aircraft's four engines lost power due to fuel exhaustion. The crew attempted an emergency landing, during which the aircraft struck a levee and sustained extensive damage. Most of the wreckage came to rest in a drainage canal. The crew members were recovered from the water on July 22, 1988.
Investigation
Investigators found no fuel in the aircraft's fuel tanks and no evidence of a fuel spill. Records indicated that the aircraft had departed El Salvador with enough fuel for 7 hours of flight. The loss of 2.7 hours of fuel could not be verified at the time. However, about one month after the accident, an employee of the operator discovered an open drain valve inside the #4 engine nacelle. A metallurgical examination determined that the valve had been in an open position for an extended period. No ground personnel observed fuel draining from the aircraft during start, taxi, or takeoff. The crew had no ability to control the valve in flight.
Evidence showed that the #1, #2, and #3 engines were not producing power at the time of impact. All crossfeed valve controls were found in the crossfeed position. Ethanol was detected in the blood of both the pilot and copilot, but analysis indicated it was likely the result of postmortem changes.
Probable Cause
The official probable cause was fuel exhaustion, which resulted in the loss of power to three engines, necessitating a forced landing during which the aircraft struck a levee. Contributing factors included the light condition at dusk and the terrain conditions (a dirt bank/rising embankment and water).