What was found
(CAN) AFTER TOUCHDOWN, DURING ROLL OUT, THE NOSE GEAR RETRACTED CAUSING BOTH PROPELLERS TO STRIKE THE GROUND. DURING ASSESSMENT INSPECTION, LOWER TUNNEL BRACKET, PN 95554-00 WAS FOUND TO HAVE 4 RIVETS PULLED THROUGH CAUSING THE GEOMETRY TO CHANGE ON DOWN LINK ASSY. SB 1123B WAS BEING ACCOMPLISHED EVERY 50HRS ON THIS ACFT. SB 1123B DOES NOT REFERENCE THESE RIVETS. THESE RIVETS ARE EXTREMELY DIFFICULT TO INSPECT ON ACFT. WOULD RECOMMEND INSTALLING INSPECTION PANEL ACCESS IN BELLY.