@tgvbhy15
I'm very pleased to share my knowledge with everybody who is working with S76 series helicopters. I have had change to read documents which are not public documents. Due to this; my understanding for consequences and the root cause is so clear. I'm very disappointed to see how some of the interest parties are willing to misslead investigators, pilots and technicians to change the focus from actual root cause to the consequence.
For example the 12th August, 2015 the preliminary report of the accident, together with issued AD, changed the focus to the Control rod, the Control rod end and the locking nut. The finding was that the Control rod and the rod end have separated. A lot of noise was created to inspect if the locking nut is not in place and an AD and ASB were issued....it is like David Copperfield who makes you see what he wants you to see.
The Control rod and the Control rod end separation during the flight are almost impossible if the helicopter behaves normally. When the helicopter is behaving normally the flight controls work load (resistance load of flight controls, mixing unit, control rods) is only 5 lbf. This is due to the fact that the hydraulic power (Servo Actuators) is making the power work behalf of PF.
If you consider the fact that the Control rod tube and the Control rod end has come loose and entered through a thread. Everyone can make on evaluation that the 5 lbf work load is not enough to cause this Control tube and the Control rod end separation.
If you consider that if the case is that the flight controls are jammed and two dying man are fighting against jammed flight controls by using the power of adrenalin. You can only evaluate how huge the forces of the two dying man can achieve?
In the Baltic Sea accident the 10th of August, 2005 the Commander was able to bend the his control stick forward. The copilot together with the captain were fighting against jammed flight controls until they were able to brake the control tube and the control rod end which is connecting copilot's and captain's control sticks.
All of this (above) was verified from the FDR, CVR and by the physical evidences from the helicopter wreckage.
Even in the theory the possible missing locking nut has no influence on the strength of Control rod tube and the Control rod end. The locking nut is needed to secure that the length of the Control rod assembly will be fixed and any unplanned Control rod end rotation (bolt thread) could not happen which could change the length of the Control rod assembly. This only during the maintenance action when the Control tube assembly is disconnected for the helicopter. At time when the Control tube assembly is connected to the helicopter the Control tube and the Control rod end is not able to rotate because it is attached by the bolts in the both ends.
The conclusion is: the control rod assembly can't be separated by 5 lbf. work load but two dying man could have enough power to brake this Control tube assembly e.g. if the flight controls are jammed.
We have to memorize that the S76 series helicopters are or should be certified under the FAA's transportation helicopter category requirements?
Last edited by Copterline 103; 21st Mar 2016 at 21:06.
Reason: Typo corrections