A Robinson R22 helicopter's right tail rotor pedal failed due to fatigue cracking during mustering operations near Georgetown, an ATSB investigation has found
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The R22 was conducting mustering at Kutchera Station, 95km west north west of Georgetown on June 22, 2019, when the pilot applied a small amount of right pedal to turn the helicopter, and the pedal cracked, bent forward and became stuck.
The pilot was unable to dislodge the pedal and prepared for an immediate landing in accordance with the stuck pedal procedure. However just prior to landing, the helicopter struck a tree and became uncontrollable, impacting the ground. While the helicopter was substantially damaged, the pilot was uninjured.
Following the accident, the helicopter's maintenance organisation identified a significant fracture in the right tail rotor pedal assembly at a right angle weld join between two sections of tube.
The right pedal was then sent to the ATSB's technical facilities in Canberra. Examination and testing determined the pedal fracture was a result of a pre-existing fatigue failure, which had initiated at the highest stress part of the welded joint and had opened up following the control input applied by the pilot.
While it was considered likely that the developing crack was present at the time of a recent 100-hourly maintenance inspection, it was not detected, likely due to the location of the weld making it difficult to identify in-situ. The developing crack would have initially presented as a hairline feature, and it was located on a matte black surface, at a change in section slightly below the level of the cabin floor.
ATSB's Acting Director Transport Safety Kerri Hughes said the location of the fatigue crack highlighted the need to be vigilant when performing inspections in difficult or hard to reach places.
"In the case of the tail rotor pedal, the inspection was made difficult due to the location, and required a torch and mirror to inspect the pedal assembly, which featured a matte black surface," Ms Hughes said.
The helicopter's maintenance organisation has added the tail rotor pedals to the list of components that undergo magnetic particle inspection at each 2200hour overall for the R22.
Ms Hughes also praised the pilot's positive actions in the crash.
"The quick thinking actions of the pilot following the failure resulted in a good outcome, with no injuries sustained," she said.
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Derek Barry
Editor of the North West Star Mount Isa since January 2016. Prior to that, an editor at several regional southern Queensland newspapers. Passionate about telling local stories. Comes with a strange accent to due an Irish accident of birth.
Editor of the North West Star Mount Isa since January 2016. Prior to that, an editor at several regional southern Queensland newspapers. Passionate about telling local stories. Comes with a strange accent to due an Irish accident of birth.
