2017-SW-123-AD Airbus Helicopters Deutschland GmbH Model MBB-BK 117 C-2 Helicopters, to Require Establishing or Reducing the Life Limit of Various Parts (Main Rotor Head – Nut, Upper and Lower Quadruple Nut, Bolts, and Inner Sleeve; Swash Plate Control Ring Assembly; Rotor Flight Control Collective Bellcrank-K; Cyclic Control Rod Tube; and Upper Control Forked Lever). 2017-SW-123-AD