Originally Posted by
ackattacker
Rick, since we're considering the scenario of a carefully planned event by someone who knew the aircraft well, the perpetrator could have disarmed the automatic deployment of the O2 masks by pulling the cb and used the direct manual control of the outflow valves to dump the pressure quickly.
Also, even if the masks dropped they would only provide 15 minutes or so and they would be confined to their seats. I'm gonna call this scenario "plausible".
Yes, it's certainly headed towards plausible. But letting the masks drop would actually help control the cabin...the folks in back would put the masks on and be immobilized, as opposed to the ten biggest ABPs trying to break down the cockpit door.
That would buy time for the bad guy by allowing the cabin to rise to whatever FL the plane was at...by the time the O2 ran out in the back it would be too late for the pax.
Regardless of the dump limit on the outflows the cabin WILL rise to the aircraft's actual altitude if the packs are off. How long it takes depends on how leaky the fuselage is.
That's one explanation for the altitude changes. The other could be an uncontrolled airplane with no AP experiencing gradual shifts in pitch trim.
But it's starting to look more and more like deliberate action in light of the reported course changes using known waypoints.