Why is it even possible to enter a desired altitude of 0 feet into an automatic pilot? As a layman, it’s hard for me to imagine why anyone flying a 777 would want to maintain an altitude of zero at full speed for more than a few seconds (if that).
While there are airports with elevations lower than 0ft, this is a good design question to ask. In general, it's assumed the pilots will do the right thing to save the day, if needed.
As one would guess, it shouldn't have been on. Insight comes from a comment in TFA:
"I’m a captain at a U.S. major airline with a lot of time in 777s. Something this doesn’t mention is the that even if ground level was set into the mode control panel, the aircraft wouldn’t have descended if it was being hand flown. That means that the flying pilot here selected the autopilot on immediately after takeoff. This is unusual at Western carriers as we like to hand fly. To me this indicates a lack of experience or confidence or both."
To elaborate, why isn't an autopilot "aware" of whether the aircraft is taking-off/landing or in-flight?
It seems completely mad that an automated flying mode could be engaged in such an obviously suicidal way on a modern bulk carrier aircraft, without so much as a blaring warning and red flashing lights.
You are assuming that there weren't blaring warnings and red flashing lights. Probably there were many.
> To elaborate, why isn't an autopilot "aware" of whether the aircraft is taking-off/landing or in-flight?
Autopilots are much simpler systems. I don't know how much you know about them, but people in the general public believe they are some AI which flies the airplane from A to B. In reality they have much more common with a thermostat than an AI. You set a target heading and the plane will bank to match it. You set a target height and the plane will pitch to match it. Yes yes, they have many modes, and some modes can do much more complicated things than these, but it is not there to replace the pilot. It is a tool to alleviate dead simple piloting tasks so the pilots fatigue less on long flights.
Just as an example how simple stupid they are: You can command the autopilot to climb, and if you don't adjust the throttle appropriately (either manually, or by enabling the autopilot to adjust it) then the plane will use up all the airspeed during the climb and the autopilot will happily fly it into a stall.
Also just a general rule about aviation incidents/accidents: It is a good idea to wait for a proper investigation report before running far with all kind of assumptions about what happened, and therefore what you think should be changed.
Here[1] is an NTSB report detailing how the AFDS and the A/T work together in a Boeing 777. They enumerate several different combinations in which the autothrottle does not provide stall protection.
It also calls out as contributing factor the crew’s mistaken belief that the airplane is pretty much impossible to stall.
1: https://www.ntsb.gov/investigations/AccidentReports/Reports/...