Originally Posted by
Concours77
As I see the design in the schematic, all hydraulic failures are mitigated by manual manipulation, what I do not see is any design feature that prevents a stuck piston or jammed power arm from inhibiting this manual control.
Ahh, I see what you're saying. No idea on this end. I'll have to look further.
Frankly, to find possible fault with the boost unit seems to be a stretch.
They had a three-way lottery. The boost unit and normal cabling, the disconnected boost and normal cabling, or the autopilot and boost engaged and broken cabling. Any of those would have saved them. But the autopilot was carded inoperative, and I doubt they had enough time to work through the possibilities. It sounds like they thought their problem was either a bad autopilot or bad boost unit.
They had about 22 seconds from recognizing the problem to impact, and it's asking a bit much for them to evaluate the possibility that the autopilot, though carded inoperative, might function enough to bypass bad cabling and run the boost unit. I have no indication whether the autopilot was actually functional, or whether they knew it.
An uncredited causal factor, as I see it, is that early and low turn. It was, as Cordwainer uncovered, a means to avoid a cumbersome departure double-hand-off. Understandable, but it meant they were in a low and significant turn before they realized they had a problem. As I discuss in my report, that turn and bank also renders a rudder correction largely ineffectual. It was a perfect storm of really bad circumstances lining up. But then, having looked at a number of accidents, this is how crashes tend to happen.