Originally Posted by Dave Fitzgerald

The COS accident is one that my dad did the investigation on. I was flying the Shuttle at the time. He had a vested interest in the outcome.

Parker Hanfin made the rudder PCU. It was the same part from the original guppy. So not a new issue. In fact, that was the problem the slide would wear, and allow hydraulic fluid to be ported to the wrong side of the actuator, in effect reversing what rudder was input.

It was a wear issue with parts. The FAA solution was tighter limits on overhaul of rebuilt units and life limited parts. Apples and Oranges to the MCAS. The MCAS is a basic design shortcoming to multiple failure events, one was a worn out part issue.

So the solution was inspection within a certain cycle limit. Grounded if over that limit. Parker Hanfin was part of the problem. Internal documents actually showed this possibility, and an external overhaul outfit was the one that blew the whistle. Ultimately, ironic because the FAA tightened the overhaul limits--and said Parker was the only approved overhaul outfit.

So.....can't really compare the two, and is why you really haven't heard any other comparisons.