Four-Engine Aircraft Disintegrates After Electrical Failure During Night Cargo Flight (N859U)

Accident Overview and Flight Details A four-engine aircraft departed Ogden-Hill AFB at 0445 local time on a cargo flight to Nellis AFB on behalf of the U.S. Air Force. The aircraft carried three crew members and 27,552 pounds of cargo. ## Loss of Electrical Power and Descent While climbing from 12,000 to 13,000 feet, the flight reported to Salt Lake departure control that it had lost all electrical power. The crew requested no-gyro vectors to visual flight conditions and clearance for an immediate descent to a lower altitude. During the descent, the aircraft attained a high airspeed and high rate of descent and disintegrated in flight. All three crew members were killed, and the aircraft was destroyed. ## Wreckage Location The wreckage was dispersed along a path about 1.5 miles long on an abandoned airport located about 4 nautical miles south of Salt Lake City International Airport. ## Probable Cause The National Transportation Safety Board determined that the probable cause was a progressive failure in the aircraft's electrical system, which led to the disabling or erratic performance of some critical flight instruments and flight instrument lighting while the flight was operating in night instrument meteorological conditions. As a result, the flight crew could not resolve the instrumentation anomalies to determine proper aircraft attitude reference, became disoriented, and lost control of the aircraft. The crew's efforts to regain control imposed aerodynamic loads that exceeded the design limits of the aircraft and caused it to break up in flight.