SAN DIEGO—A brief Navy narrative of a fatal helicopter crash off Southern California says the aircraft experienced “side-to-side” vibrations that caused the main rotor to hit the deck of an aircraft carrier while landing, The San Diego Union-Tribune reported. The MH-60S Seahawk fell off the deck of the USS Abraham Lincoln on Aug. 31. One crew member was rescued and five were declared dead after a search. Five sailors on the carrier deck were injured. The crash summary in a Naval Safety Center document, first reported by the Navy Times, did not include any information on what might have caused the vibrations. Michael Canders, a retired military helicopter pilot who is the director of the Aviation Center at Farmingdale State College in New York, told the Navy Times that side-to-side vibrations can occur if rotor blades are out of balance. “All of that has to be carefully balanced to make …