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The state of UX design has advanced so much, perhaps we need more UX testing so that even pilots who are unfamiliar with a plane could figure out what to do. Am
by teyc 15y ago
The state of UX design has advanced so much, perhaps we need more UX testing so that even pilots who are unfamiliar with a plane could figure out what to do. Amazon probably does more with figuring how to help users checkout their shopping cart than plane designers helping pilots get a plane out of a stall.
Alternate law and normal law introduces two modes. This breaks one of the rules of user experience, especially if it is infrequently encountered. Combined with turning autopilot off on its own, it is bound to cause even more confusion. The plane could have put an alert asking the pilot to go on autopilot, otherwise, it will continue by making educated guesses. (A pilot is no better judge of airspeed than the computer)
Another rule of UX broken is "tell" instead of "announce". The voice should have said "Stall. Dive now" or "Stall. Why are you pulling the stick back?".
The flight computer can reinforce its credibility by demonstrating it has predictive capability. For instance, it can say, "decrease your angle of attack or you will stall in 5 seconds", then "4", "3" "2" "1", "stalling". The voice should demonstrate increased tension and panic as counting down.
It is high time the flight computer act as the "third pilot". It is similar to video judges in competitive sports.
Of course people may choose to ignore the computer, but we can then continually review why the computers assessment was wrong and improve on it.
What I don't understand is, how does a plane know it's stalling if the pitot tubes are frozen?
By the way, optical flow meters could have been used as a backup.
- freemarketteddy 15y ago>how does a plane know it's stalling if the pitot tubes are frozen? I think it can easily do that by measuring the G force similar to an accelerometer on iPhone.
- jrockway 15y agoNo. There is, not surprisingly, another sensor in the airflow for that. http://www.lindenhillimports.com/images/photof48.jpg http://www.lindenhillimports.com/images/photof48.jpg
- barrkel 15y agoAccelerometers measure acceleration. You won't feel any unusual G forces for any constant velocity, whether it's climbing or descending.
- freemarketteddy 15y agoYes you're right...Stall is not a free fall but a sudden reduction in lift which can occur for instance when the angle of attack increases beyond a certain value.
- lutorm 15y agoIt's actually not a sudden reduction in lift either. Even in a stall, lift equals gravity. It's just that the normal relationship between angle of attack and lift is reversed to that higher angle of attack lowers lift rather than increasing it. This makes it inherently unstable and difficult to control, but there is in principle nothing preventing you from flying a stalled airplane all day.
- Nick_C 15y ago> how does a plane know it's stalling if the pitot tubes are frozen Angle of attack sensor. AoA is the actual definition of a stall as it measures the point at which airflow breaks away from the wing, reducing lift. Re your other points on computer warnings, cockpits can get pretty noisy when shit happens with various alarms, buzzers, horns and voices going off. There's actually a tendency to reduce the number of different alarms and use screen information to indicate the problem (although that may be changing after the Qantas drama in 2010 http://en.wikipedia.org/wiki/Qantas_Flight_32 http://en.wikipedia.org/wiki/Qantas_Flight_32).
- teyc 15y agoThere's actually a tendency to reduce the number of different alarms and use screen information to indicate the problem Yes, that'd be good UX. There should be only one actionable task presented at any time to correct errors. In any case, user testing is more important than guidelines. I wonder if grouped alarms make any sense. For instance you can group all alarms related to stalling together, and present the one thing the pilot can do to correct this. This gives the pilot a sense of what is the most effective use of their attention in a bad situation. QF mishap - the Wikipedia article didn't talk about the alarms.
- Nick_C 15y agoWith the Qantas incident, they had something like 146 msgs appear on the screen spread over about 5 or 6 pages. So they were forcibly distracted from solving the problem from a top-down approach to having to investigate and cancel each of the 146 msgs, and that was why the two extra pilots were such a godsend, they were able to help out.
- teyc 15y agoYes, a message flood is also a failure of UX. At my place of work, when a flood of errors occur, we throttle and batch the errors so that the admin doesn't get thousands of emails. Given that user interfaces on airplanes are digital now, there are a lot of opportunities to innovate. For instance, where there are multiple failures and alarms, it might be better for the panel to continuously replay the sequence in which the alarms were set off, more or less like how movies do it to help the viewer understand what is happening on the computer. By showing how a system is failing through time, it shows a causal relationship. In addition, you can provide drill down capabilities. In the case of Air France, perhaps it could have illustrated the AoA through time, and the flight velocity. Perhaps that would have explained something to the pilot.
- joshAg 15y agopitot tubes just measure longitudinally forward airspeed (ie the direction the plane is going). altimeters measure asl (above sea level) altitude, and gyros measure angle of attack and accelerations. I believe there is a way to tell stall just from altimeter and gyro readings when combined with state information (flap position, gear up/down, &c.) about the plane. great points about the ui design, though. i think the biggest issue, though, was the controls not announcing (either through force feedback or a blaring alarm or an urgently blinking light) conflicting input on the control sticks. does anyone know why this is a feature in the first place?
- jarek 15y agoThe autopilot turning off altogether is the biggest equipment problem here (along with averaging/independent sticks). An alarm will surely be necessary but I don't see how killing off autopilot helps since the pilots probably won't have any better of an idea. Perhaps this specific incident caught an ugly edge case. There is actually a fair amount of ergonomics and interfaces design that goes into these systems - at least equal to Amazon's shopping cart, probably more. Same goes for systems like ATC. "Stall" does mean "dive now" to every pilot. It is extremely questionable whether including this information explicitly would help at all in the chaotic, confused environment in the cockpit at the time. "Why are you pulling the stick back" is way too long as well, although it does raise a fair point about keeping both pilots aware of each other's control inputs.
- assemble 15y agoTry writing the code for an autopilot some time. It's hard. We spend a lot of time flight testing just the autopilot. Making something go in a particular direction at a particular altitude at a particular speed is hard enough. Throw in a stall and the best the plane can do is try to nose down.
- omegant 15y agoWell not at 400' and 130knots... That is way they were performing a windshear maneuver ( incorrectly) at FL 340.
- assemble 15y agoFair enough. My main point is that we spend a lot of time trying to get the autopilot to function right, but it's not an easy problem where you can just throw a bunch of edge case detection code in. There are lots of physical control laws involved in a/c code that you can't break. Silly laws of physics type things.
- DanBC 15y ago> The voice should demonstrate increased tension and panic as counting down. This part doesn't sound so useful, in a cockpit with worried pilots.