Aircraft on the NTSB record: Mcdonnell Douglas 500N · serial LN-032

The pilot's in-flight loss of control due to the failure and separation of the forward thruster control cable telescoping sleeve ball swivel fitting, which resulted in a stuck thruster and the entry into an uncontrollable yaw/spin. Also causal was the mechanics improper maintenance actions during diagnostics to determine the cause of a yaw control anomaly in that he failed to remove an access panel over the FS113 splitter to fully and completely examine the thruster control cable. Factors in the accident were: (1) the incomplete emergency procedures/system explanations in the RFM for a stuck thruster condition; (2) the pilot's negative transfer of emergency procedures from the HH-60, which likely induced him to make incorrect inputs to throttle, collective, and the anti-torque controls during the onset of the stuck thruster condition; and (3) MDHI and the cable manufacturer's failure to expeditiously diagnose and correct the stress corrosion cracking problem in the forward thruster cable ball swivel fitting.