It was determined that the accident Catastrophe was caused Causation by a fatigue crack in the main spar of the left wing that caused Causation the outer part of the left wing , outboard of the engine nacelle , to separate Forming_relationships from the remainder of the aircraft .

Hunley '' approached Arriving just under the surface , avoiding Preventing_or_letting detection until the last moments , then embedded Placing and remotely detonated Attack a spar torpedo that rapidly sank Motion_directional the sloop-of-war with the loss Death of five Union sailors .