7 ms·
The computer worked to prevent the aircraft from entering an overspeed condition by pitching up and attempting to recover from the dive even before that dual st
by jsmthrowaway 10y ago
The computer worked to prevent the aircraft from entering an overspeed condition by pitching up and attempting to recover from the dive even before that dual stick input was an issue. It was intervening 13 seconds into the incident, as the aircraft threatened to exceed safety tolerances. The dual stick input created another issue after that intervention began.
The automation very possibly saved lives here. The overspeed protection is good because had that not happened, there's a real possibility that significant sections of the airplane would have sheared off, or the airplane could have rapidly drifted further out of control as it accelerated quickly through 365 knots indicated. Big, heavy, thrusting things gain airspeed rapidly when you pitch them down 18 degrees at cruise power, and the margin of recoverability is very minimal. There are arguments that humans are unable to prevent some scenarios in that situation because by the time higher-order thinking on decisions has happened, it's too late. See, for example, the surprisingly lengthy duration of time between the incident and setting for idle, which probably should have been among the first things done in response. Brains are slow when things happen fast, and a symphony of alarms and whoops (undoubtedly in progress) does not help.
A Boeing would not have intervened in the situation at all and would have allowed the aircraft to go overspeed, risking serious airframe damage. If you crash dive an airliner at cruising speed, very, very bad things happen. At cruising altitude safety envelopes are very small. The paragraph talking about direct law is, roughly speaking, what would have happened had this been a Boeing aircraft. (This isn't bad, it's just different philosophies of pilot responsibility. I'm not partisan on the difference like some pilots and am willing to acknowledge the benefits of both approaches; this one is an Airbus advantage.)
- PhantomGremlin 10y agoA Boeing would not have intervened in the situation at all OTOH it's probably a lot harder to "jam" a camera into the center stick of a Boeing than it is into the side-stick of a Bus.
- deleted 10y ago[deleted]
- m_mueller 10y agoI could also imagine that a Boeing pilot generally has more respect of the machine (s)he's operating because of the direct control. The overall deadly accident rate in Boeing vs. Airbus, plotted over time, would be interesting.
- nether 10y agoBoth aircraft are so incredibly safe with vanishingly low accident rates, that it'd be nearly impossible to suss out accidents due to the respective designs versus pilot error, weather, carrier procedures etc.
- WWLink 10y agoThe silly thing is they could combine the fly-by-wire system with the boeing-style control system if they wanted to. There's no reason why not, other than the space in the cockpit I suppose. It's basically just a much bigger joystick, no?
- JshWright 10y agoThe biggest advantage of the Boeing approach is that the controls are linked; if one moves, so does the other. Mismatched inputs are impossible. I truly don't understand the Airbus approach... There is no method of resolving conflicts between the sticks that make sense... Sum them? Average them? Take the last seen input? Prefer the left side always?
- mikekchar 10y agoNot knowing anything about it, it seemed to me from the article that the system takes mismatched input as an indication that the autonomous systems need to be engaged. Though if it subsequently decides not to engage, I'm not sure what you should do...
- fryguy 10y agoI don't work in avionics, but in another field with two pilots. Most things are done by exclusive control meaning there is a selector for which station has the flight stick. But for shared control the way it works is the first station that has non-zero inputs takes exclusive control until they have zero inputs for a short period of time. Although in our case, the availability of two sticks is for hardware redundancy rather than pilot redundancy so the Boeing approach seems safer.
- FabHK 10y agoOf course there is a system, and it's sophisticated. Averages are taken in case of inputs on both, and there's a priority button to take precedence (so that the other is ignored). There's more to it than that, but of course there's a system and a lot of thought has gone into it. In the AF 447 case, the left pilot did take priority, but the dude on the right took it back. Had the left one taken it and held it (by keeping the button pressed), the accident might have been avoided. So the system is hardly foolproof, and one can argue about the particular implementation of the interface and the merits vis-a-vis hardware-linked yokes, but any notion that Airbus haven't thought carefully about it is complete bogus. http://aviation.stackexchange.com/questions/3455/why-is-the-priority-takeover-button-used http://aviation.stackexchange.com/questions/3455/why-is-the-...
- tropo 10y agoNope, it wouldn't happen in a Boeing aircraft. This is a well-known Airbus defect that was a contributing factor to the crash of Air France Flight 447. Boeing uses traditional controls. It's like a race car steering wheel on a big movable stick. It is really easy to see how the control is positioned. Airbus uses a small joystick off to the side. It is force-based like a Thinkpad pointing stick, so it barely moves when you push on it. It isn't easy to see if the device is being pushed. Here, a camera got jammed against the joystick. The pilot nearly made things worse by putting the aircraft in "direct law" mode because he couldn't tell that his own control was causing the problem. In the case of Air France Flight 447, the pilot's idiotic control input was not visible to the two other people in the cockpit. Airbus will obviously brush this one under the carpet as well, because admitting that the side-stick control is hazardous would cause a need for drastic retrofit of all Airbus aircraft cockpits. https://en.wikipedia.org/wiki/Air_France_Flight_447#Sidestick_control https://en.wikipedia.org/wiki/Air_France_Flight_447#Sidestic...
- jsmthrowaway 10y agoThis is the partisanship I'm talking about, for what it's worth. I've flown an A320 in a full-size simulator and my experience with its sidestick, even in that simulator environment, does not match what you are describing. The sidestick moves quite far and quite noticeably[0], and does not behave like a ThinkPad. The aircraft simply ignores drastic input, which might be what you're thinking of with that assessment? Anyway, I'd imagine if I were PIC of this flight and my aircraft suddenly pitched down 18 degrees, the sidestick would be the first thing I'd look at in about the first 750 milliseconds. Not sure why that didn't happen here, but I tend not to judge pilots from accident reports, so I have't put a lot of thought into it. I can't imagine a scenario where any camera could conceal itself in that arrangement, unless the A330 has huge voids under the stick that the A320 does not. Even stopping short of judging the PIC, I have a hard time imagining an outcome where this is an Airbus control flaw, no matter the (as one can see, passionate) opinions on sidestick. [0]: https://www.youtube.com/watch?v=5zBsxJdI5JI https://www.youtube.com/watch?v=5zBsxJdI5JI
- xenadu02 10y ago
- Xixi 10y agoAll modern Boeings (>= B777) are FBW (fly by wire) and have flight envelope protection. A 787 will absolutely not go over-speed: it will automatically throttle back.
- Declanomous 10y agoAlso, Boeings have a traditional yoke. It seems like a lot of this trouble was caused by the fact a sidestick can easily be hit by something on the front of the chair.
- deleted 10y ago[deleted]
- awinter-py 10y agoWill throttling back help? The plane is pitched down 18 degrees and mach 0.9 KIAS.
- deleted 10y ago[deleted]
- deleted 10y ago[deleted]