Improper overhaul procedures etc.
I have open my files. One correction must be done:
The FAA approved overhaul instruction requires that the Plasma coating material should be Metco 445 (85 % copper and 15 % aluminiun).
The Tallinn University of Technology and NTSB came up with the same results of SIK used plasma composition. The accident servo piston plasma composition was Cu 98 %, Al 1,5 % and Ti 0,3 %. The other finding was that due to wrong plasma composition the plasma flakes doesn't decompose to the smaller pieces as planned.
By using the right material (Metco 445) the removing plasma flakes should not maintain the present size and the plasma flakes should be decomposed to the smaller and smaller pieces to avoid the C3 port obstructions. This is the knowledge what I, NTSB, FAA and SIK are sharing. This in no new news for any stakeholder.
SIK S76 HRT Servo Reliability Improvement Plan meeting on 15th Sep, 2006 has agreed that: "Chips/flakes have low likelihood of creating significant (>75%) blockage during 3000 TSO".
The type certification requirements requires instead of "low likelihood" to be "extremely improbable". This is an issue what Lockheed Martin Corporation is nowadays accountable as the TC Holder of S-76.
If more detailed information or evidences are needed, I'm more than pleased to show and provide it.
Please see the attached pictures of the plasma and plasma composition as an evidence of improper maintenance.