Summary
We propose to adopt a new airworthiness directive (AD) for certain Agusta Model A109C, A109E, A109S, A109K2, and AW109SP helicopters. This proposed AD would require inspecting the lock wires securing the tail rotor (T/R) duplex bearing locking nut (locking nut) to determine whether any lock wires are missing or damaged. This proposed AD is prompted by reports of loosening T/R locking nuts, which if not corrected, could result in failure of the T/R and subsequent loss of control of the helicopter.