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Originally Posted by daviddem
- assuming the premise of an onboard emergency, it makes sense that the captain would head towards the nearest suitable airport. Would he (you) do that by programming the auto-pilot and if so would he (you) program it only to head towards the airport or also to land there?
This is very much situation dependent. If I'm over land (and thus talking to a controller), I may just ask the controller for vectors if I've got my hands full with the emergency. Time permitting, I'll simply put a fix into the FMS and fly direct to that fix (this could be a VOR near or at the airport, or a fix on the arrival, or just a fix that the controller supplies to me). The "programming" involved is to simply type in the fix name, put it on the top line and then hit the execute button and engage LNAV.
If I'm out over the middle of the ocean with an emergency, I am probably diverting to either Keflavik or Lajes. In either case, I've already got those airports in Route 2 of the FMS (kind of a standby route for use in emergency). I'll just make route 2 the active route and fly direct to the airport.
You really can't program these things to land. That's a common misconception. We can enter the ILS arrival into the box and fly all the fixes right to the runway. You can even have altitudes and speeds associated with the fixes and it will start down and attempt to slow down at the proper time. But the plane won't configure itself (lowering gear and flaps) and won't slow below a safe speed for the current configuration. Thus, if no one is there to dirty up the plane, it might fly right down to the runway with the gear up and at a fast speed...kind of a controlled crash.
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- if the captain did NOT program the autopilot for a landing, what is the autopilot supposed to do once reaching the waypoint and nobody takes back control?
After reaching the last waypoint in the list, the autopilot will revert to Heading Mode and hold the heading it had when crossing that waypoint.
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- in the event that the autopilot also eventually got damaged in the incident/fire while on the way to the airport, and the crew is incapacitated, what happens to the plane then? I guess since nobody or nothing makes input to its controls, to correct its trajectory, it should crash pretty quick, no?
It could fly for quite some time, perhaps hours, without crashing. If it's trimmed properly (and the autopilot actually makes trim adjustments, except for aileron trim), it could just enter gradual turns one way or the other and the altitude might vary somewhat.
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- what would be an explanation for the turn towards the NW and the final position calculated from the ACARS pings?
Again, I have to admit to not being glued to the constant barrage of updates on this event. I keep my distance in order to preserve my sanity in the sea of baseless speculation going on. I really have no idea what you're referring to.