The NTSB has released the final report on the fatal crash of a Robinson R44 on Nov. 22, 2022, and the probable cause for the accident was “the inadequate inspections of the forward left control rod end attachment hardware to the stationary swashplate by the pilot and by maintenance personnel, resulting in an eventual loosening and backing out of the hardware and subsequent loss of helicopter control.”
About five minutes before the accident, a local staff meteorologist and the R44’s pilot took off for simulated news scene training in Charlotte, North Carolina. After conducting left 360-degree orbits over a highway, the helicopter went out of control, descended steeply, then crashed onto a grassy area. According to the NTSB, “The pilot made a radio call on the local helicopter common frequency before impact stating that ‘Three’s going down, Sky Three’s going down.’ There was no post-accident fire.”
Following the accident, investigators found that connecting hardware was missing from a control rod end that attaches to the helicopter’s stationary swashplate. “A metallurgical examination of the remaining components suggested that the connecting hardware, including a threaded bolt, nut, Palnut, two washers, and two hat-shaped spacers were loose and backed out during the flight. It is unlikely that the hardware was secure before the flight and may have been loose for multiple flights before the accident.
“Additional examination of the remaining hardware revealed that one of the two spacers was installed backwards, most likely during the field overhaul of the helicopter about three years before the accident.”
The helicopter had flown 26 flights (including the accident flight) after the most recent 100-hour inspection, which was completed on October 16. The field overhaul in August 2019 included the replacement of three rod ends, including the forward left control rod end that was implicated in the accident, as well as the lower rod ends.
In its examination of maintenance records, the NTSB noted that a Robinson Helicopter service letter (SL 50) had not been complied with. “The SL instructed operators to replace certain cadmium-plated nuts (MS21042L4) with D210-series nuts due to corrosion and cracking issues. The D-210-series nuts should have been replaced during the field overhaul in August 2019 (a complete set of D-210 nuts was included in the overhaul kit). A mixture of MS21042L4 and D-210 nuts were found throughout the flight controls on the accident helicopter. The type of nut that liberated from the forward left control rod/stationary swashplate could not be determined.”