@Sanus
Cop103 you mention many interesting things but surely even a first year metallurgist could tell the difference between a thread that has failed through looseness (chaffing and wear) and a thread that has suffered sudden shear overload? The latter would have rolled over thread crowns etc.
Sanus, my knowledge is not limited to my first year metallurgist. You should remember that the 60.000 non-public documents have included specialist metallurgist reports e.g. from MIT. I’m counting on these MIT's experts knowledge and the experts reports what I have seen.
Your opinion that the control tube and the control rod end has separated as “has failed through looseness (chaffing and wear)”. If this has been the case then the question mark will come over Bristow’s maintenance organization and the technicians. I can't believe that the Bristow’s technicians will bypass during PFC or Daily Check (whatever is the used name for daily inspection) were the S76’s “formula” is open. This is an area of technician interest to check the condition of each Servo Actuators, links, rods, tubes, locking pins, safety wires, visual locking markings, fluid levels, bearings play, leakages ect.
Every technicians of S76 type knows that the area under the “formula” is the most critical area for the safety. If the scenario is like you descript “has failed through looseness”. This development will take time to be separated. The time what is needed to make this looseness to be a separation is not a short time. During this long time this defected control tube and the control rod end should be passed quite many technician's eyes and hands. This doesn’t make sense for me and doesn’t make sense for Bristow’s maintenance organization.
The flight crew should have an indication (during hovering) that the basic, neutral position of control stick has removed and also the play on the rod assembly makes the most likely the helicopter to be unsteady because the flight controls rigging is changing all the time...
The FAA's certification requirement for the helicopter type certification insists that the all critical components or systems should ensure the continuity of safe flight. The all critical components of the all critical systems must be:
1. Redundant (dual systems, hydraulic systems, electrical systems, ect.)
2. Fail safe (single rods, links, tubes, ect.)
This Control rod tube and the control rod end belong to under of the requirement of FAIL SAFE. When the control tube and the control rod end have separated the mandatory requirement of fail safe component doesn’t exist. This is the helicopter type certification requirement. The S76 helicopter is certified under the FAA's Transportation Category. This certification could be an issue and the present finding could have an affect to the airworthiness?
We remember that the accident of 12th of August, 2015, where six people lost their lives.