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Originally Posted by BBKing
so there are questions to answer.
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One thing is for sure - as we know in situations involving incidents with commercial jets - no stone will be left unturned. Even if it takes the investigators or "tin kickers" years to establish a cause, they don't like having any plane incident undetermined because they cannot correct the probable cause which could strike again in another plane.
[Warning - Some Air Investigation history coming up]
You only have to look at the case of the jamming rudder PCU servo valve issue, involving three flights but all the same model plane, the Boeing 737. In this case which took investigators 10 years to solve (one of the longest investigations in aviation history).
What happened? If you can recall, two of the three planes were ripped from the sky due to one small minuscules problem in the rudders PCU servo valve which controls the movement of the Rudder. In both incidents - the rudders PCU servo valve would jam and malfunction forcing the two planes to go an unrecoverable pitch to nose down position.
One of the main reasons it took so long to determine the absolute cause of the crashes of both B737's is that the rudders PCU servo valve, upon previous inspection left no evidence of any malfunction, it was only when a thermo shock test was performed that investigators saw with their own eyes that the servo valve jammed and then the valve would then only work in reverse mode, thus any commanded action taken by the pilots meant the opposite effect on the rudder, so in essence, what the pilots didn't know and will never know is that they were actually steering their plane to the ground.
Other contributory evidence came to light too when the third flight involving a B737, when the same rudder hard-over malfunction occurred but the pilots managed to land safely giving investigators a plane that was intact and pilots that were alive and able to tell them their version of events.