NTSB says mechanical failure caused 2020 helicopter crash at USC
The National Transportation Safety Board determined that a 2020 helicopter crash atop USC's Keck Medical Center was caused by mechanical failure after a part of the helicopter's tail rotor separated from itself mid-flight.
The medical transport helicopter was carrying a donated organ.
According to the NTSB, the ring nut separated as the helicopter was approaching the medical center causing the pilot to lose control of the tail rotor sending the aircraft into an uncontrollable spin. During their investigation, officials discovered the ring nut had a "worn footprint." They did not discover any other mechanical malfunctions or failures "that would have precluded normal operations."
Investigators said that there were four previous cases that were "associated with loss of tail rotor control" and the ring nut in question. According to the manufacturer Agusta, following internal investigations, prompted them to issue changes to their maintenance procedures. Additionally, the European Union Aviation Safety Agency issued an emergency airworthiness directive in 2012 and Agusta issued five Technician Bulletins in September 2012.
The Federal Aviation Administration followed suit and issued an airworthiness directive nearly two years later. After the fourth failure, the FAA issued another order, requiring daily checks by the pilot of the aircraft, which the pilot in the 2020 crash at USC did.
In total, the crash hurt three people, two of whom sustained serious injuries.
