What was found
PIE - ON CLIMB-OUT AT FL 260, A LOUD UNEXPLAINED BANG OCCURED SIMULANEOUSLY WITH AN AIRCRAFT PITCHING MOMENT (TWICE), IMMEDIATELY THE AIRCRAFT BEGAN TO VIBRATE. A/C DIVERTED TO PIE. PERFORMED TAKEOFF POWER CHECKS ON ALL ENGINES, NO FLUCTUATIONS NOR VIBRATIONS NOTED. PERFORMED OPS CHECK OF ALL FLT CONTROLS AND NO FAULTS NOTED. (M)