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Such a tragedy... Forgive my ignorance, maybe some pilots can shed some light on this. In the article it mentions that even though the plane was flying in "al

by ookblah 15y ago

Such a tragedy... Forgive my ignorance, maybe some pilots can shed some light on this. In the article it mentions that even though the plane was flying in "alternate" mode, my understanding is that it still has limits to what inputs can be given. That said, even if autopilot is off, why wouldn't the computer have emergency functions to negate strange situations like this? When would pulling completely back on the stick while losing altitude rapidly ever be considered within the range of normal?

nkurz 15y ago
why wouldn't the computer have emergency functions to negate strange situations like this? I think there are two main reasons. First, one is dealing with a situation where the autopilot has disengaged because it is receiving contradictory input from its sensors. How is the computer to know that a second sensor has not failed, and that its notion of what is normal is not? Failures may tend to cluster. The current technological presumption is that in the event of something unexpected, trust the human over the computer. At the current level of technology, this is still often a good bet. Second, I think the legal situation encourages having a human be the final point of control. Presume that computer overrode the human, and that due to some low-probability unexpected combination of failures this caused the plane to crash despite the pilot doing "the right thing" as proven by the flight recorder. Then picture the size of the lawsuit against the everyone involved in the building and licensing of the plane. Contrast this with the same situation, but with the pilot responsible and dead in the crash. One may find that there isn't much desire from the manufacturer to change the system to take that final responsibility.
jarek 15y ago
> When would pulling completely back on the stick while losing altitude rapidly ever be considered within the range of normal? I don't have a terribly accurate model of airplane control in my mind, but I think this would be the right answer when the nose is pointed down (i.e., the plane is diving). In some cases I think it might also be the right answer if your nose is level but you're losing altitude, e.g. when in a strong downdraft. Pulling back was the wrong thing in this situation because the plane was in stall, but due to sensor problems and later high angle of attack/low airspeed, the avionics didn't have a complete image and an absolute certainty that the plane was in a stall (hence the stall warnings cutting in and out, too). I'm not sure I'd want the plane overriding me in this specific case.
mtts 15y ago
There is a famous incident with an A330 test flight where the auto pilot system happily flew into the ground precisely because, unlike Bonin, it did not panic and give in to the instinct to pull the nose back up. I'm guessing this incident made the engineers who designed the plane a little more eager to provide for a true unhampered manual override.
- Zhenya 15y ago
  For Reference http://en.wikipedia.org/wiki/1994_A330_test_flight_crash http://en.wikipedia.org/wiki/1994_A330_test_flight_crash

by ookblah 15y ago

nkurz 15y ago

why wouldn't the computer have emergency functions to negate strange situations like this? I think there are two main reasons. First, one is dealing with a situation where the autopilot has disengaged because it is receiving contradictory input from its sensors. How is the computer to know that a second sensor has not failed, and that its notion of what is normal is not? Failures may tend to cluster. The current technological presumption is that in the event of something unexpected, trust the human over the computer. At the current level of technology, this is still often a good bet. Second, I think the legal situation encourages having a human be the final point of control. Presume that computer overrode the human, and that due to some low-probability unexpected combination of failures this caused the plane to crash despite the pilot doing "the right thing" as proven by the flight recorder. Then picture the size of the lawsuit against the everyone involved in the building and licensing of the plane. Contrast this with the same situation, but with the pilot responsible and dead in the crash. One may find that there isn't much desire from the manufacturer to change the system to take that final responsibility.

jarek 15y ago

> When would pulling completely back on the stick while losing altitude rapidly ever be considered within the range of normal? I don't have a terribly accurate model of airplane control in my mind, but I think this would be the right answer when the nose is pointed down (i.e., the plane is diving). In some cases I think it might also be the right answer if your nose is level but you're losing altitude, e.g. when in a strong downdraft. Pulling back was the wrong thing in this situation because the plane was in stall, but due to sensor problems and later high angle of attack/low airspeed, the avionics didn't have a complete image and an absolute certainty that the plane was in a stall (hence the stall warnings cutting in and out, too). I'm not sure I'd want the plane overriding me in this specific case.

mtts 15y ago

There is a famous incident with an A330 test flight where the auto pilot system happily flew into the ground precisely because, unlike Bonin, it did not panic and give in to the instinct to pull the nose back up. I'm guessing this incident made the engineers who designed the plane a little more eager to provide for a true unhampered manual override.

Zhenya 15y ago
For Reference http://en.wikipedia.org/wiki/1994_A330_test_flight_crash http://en.wikipedia.org/wiki/1994_A330_test_flight_crash