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The Airbus vs Boeing approach to fly-by-wire is a bit of a religious issue, like type safety or memory management in our world. Many words have been written on

The Airbus vs Boeing approach to fly-by-wire is a bit of a religious issue, like type safety or memory management in our world. Many words have been written on both sides. I think the UI issue in AF447 is much less clear cut. It's more a lack of any indicator that pilots are making opposite inputs, rather than a misleading or confusing display. Airbus did not anticipate that a pilot would stall a plane and fly it directly into the ocean. There was a whole chain of events (including some appalling human factors) that led to the tragedy there. The avionics teams at both companies have put an incredible amount of thought into how these systems are designed, and how they fail. The differences are instructive, but we should refrain from being quick to judge which is more or less intuitive.

acqq 12y ago
If it's really so implemented, averaging "full left" and "full right" inputs to the "keep going straight" response is deeply wrong. Apparently missing mechanical feedback really contributed to the accident.
omegant 12y ago
Sorry but you are wrong, it´s not a religious issue, it´s a clear IU mistake by Airbus. I´m currently flying A-320, I´ve also flown B 737(300 and 800), and MD88. It´s true that at the beginning the new airbus received a lot of heat from pilots. After all they were trying to reinvent cockpits UI from 0. This led to a series of design accidents (due to initial design mistakes ) like the one on the article. The initial idea it´s not bad: reducing weight (removing all mechanical and hydraulic controls), inventing the glass cockpit, simplified system management, etc.. It took over a decade to polish the cockpit (and the whole airplane, that had tons of electronics related failures all around) to it´s actual safe and workable state. Those issues, plus the idea that pilots had to readjust your whole idea of a cockpit, were the ones that created that opposition. The opossition it's almost gone now, although in general we pilots still prefer Boeing aircraft (at least in Europe). Airbus airplanes fly very nicely and are great too. But now that we are used to the new IU, the concept problems are still there. Main diference between flying normal fly controls and a moving auto-throttle and airbus fly-by-wire: -Airbus throttle levers don´t move while the auto-thrust is changing the power setting. All the other airplanes as far as I know do it. -Airbus side-sticks don´t move when the autopilot or the other pilot is giving an input. Also as somebody explained above, the inputs are added, you can end with a double (or zero input), if you forget to push the priority button (in stress situations like last second corrections to land it´s easy to forget it). Why this is a mistake? because when flying a modern airliner you have an excess of information to process, all at once. A moving auto-throttle let´s you know what the engines are doing through your hands, without having to look at a tiny indicator at the instruments. Also it let´s you override the auto-throttle briefly because you need more power or less power at a given moment, without having to disconnect it. With airbus auto-thrust either the airplane or the pilot has the control, and you have to manually takeover. This may be dangerous at an approach that it´s already hard enough with cross winds or heavy rain. The same apply to the side-stick. Normal autopilots move the fly controls at the cockpit while actuating them. This let´s you know what the autopilot it´s doing. And of course when a pilot it´s flying manually, the other pilot knows exactly what he is doing ALL THE TIME. He can slightly correct a maneuver without having to take over the controls from zero. Airbus has wiped a layer of fundamental information available to the pilots, increasing the information overoosd through the vision. It´s the equivalent of driving a race car with a playstation control. Most of the time this information it´s not used(like in cruise), but you really, REALLY need it when things become hairy close to the ground. In fact I routinely disconnect the auto-thrust to land, with the Boeing and MD88 I kept it engaged. Airbus knows this, but it´s too late to change 20 years of airplane development. They´ll need to change too many things (systems, procedures, certification, instruction), also right now it´s easy to change from flying let´s say a A320 to a A 330, due to having very similar cockpits and systems (that´s a great idea). The conversion course it´s short and relatively cheap. Changing the controls would make this fleet changes much more expensive and time consuming to Airlines. Edit: overall small changes to improve clarity.
- jacquesm 12y ago
  It's a real pity that the resistance to improving (or even fixing!) these shortcomings is mostly economic in nature, I can't imagine that the pilots would object to having these issues solved once and for all. Unfortunately pilots don't have a whole lot of options to exert meaningful pressure on aircraft manufacturers.
  - oftenwrong 12y ago
    >Unfortunately pilots don't have a whole lot of options to exert meaningful pressure on aircraft manufacturers. If a group of pilots came together to declare an aspect of a plane's functionality as unsafe, wouldn't that send strong signals to the public, governments, ICAO, etc? Even if those signals were ignored initially, they could become more important later if an accident occurred in which the same functionality is (or "was"?) involved. At that time, the media groups, great lovers of scandal and tragedy, would come out and say, "Functionality X contributed to the accident. These pilots warned about the dangers of functionality X back in year Y, and everyone ignored them." After that, the pilots' opinions might be more heavily considered.
  - metacorrector 12y ago
    and when they do apply pressure on Airbus from their side of the cockpit, they can't tell if countervailing pressure is being applied from the other side?
- userbinator 12y ago
  I think the concept you're referring to is self-indicating, or in this case the lack thereof. A much more commonplace example that comes to mind is volume control knobs on things like stereo amps; the "old style" had a knob directly connected to the potentiometer controlling the volume, so it was self-indicating and at a glance (or even just by feel if the pointer is tactile) you could see what position it was set to. Now it seems fashionable to use knobs that don't have any markings and will spin continuously, meaning that you have to look at the display to see what the setting is. To me it sounds like a cost-cutting measure - to have controls that move, there has to be an actuator in them, which makes it more expensive. My stereo which has self-indicating volume knobs actually contains a small motor that rotates them when I use the remote control.
mdc 12y ago
"Airbus did not anticipate that a pilot would stall a plane and fly it directly into the ocean" Stalling and flying into the ground have been two common failure modes since flying began and they often happen in sequence. I would think they would be high in the list of misuse cases any aircraft designer would consider. "we should refrain from being quick to judge which is more or less intuitive." We should not be quick to judge which UI is more effective, but by definition we can be quick to judge which is more intuitive. In fact, the more time you spend with a system, the less qualified you are to comment on whether it is intuitive. Judging whether a UI is intuitive should take very little time and no expertise past understanding basic operations. I'm certainly not qualified to judge, but I'd think anyone who has experience with modern flight systems would be qualified to comment on whether a particular design was intuitive.
- lutorm 12y ago
  I think he meant "stall a plane and keep it stalled for many minutes, flying it into the ocean". Stall/spin accidents are common, but they normally arise from loss of control at low altitude when there's not enough time or space to recover.
mikeash 12y ago
The stalling was a consequence, the fundamental problem is that there's no indication that two pilots are fighting over the plane. And that is an obvious problem. It's literally one of the first things you cover when you begin learning how to fly. The instructor will sit you down and walk through how you hand off the controls and agree who's flying the plane at any given time. Likewise, when flying with another pilot you always do a positive handoff. "You have the plane." "I have the plane." The physical link between the two sets of controls is an important backup mechanism that ensures this happens. Not linking the two sets of controls is insane. It's unrelated to the different approaches to fly-by-wire. Taking two radically different control inputs and simply averaging them together makes no sense.

acqq 12y ago

If it's really so implemented, averaging "full left" and "full right" inputs to the "keep going straight" response is deeply wrong. Apparently missing mechanical feedback really contributed to the accident.

omegant 12y ago

Sorry but you are wrong, it´s not a religious issue, it´s a clear IU mistake by Airbus. I´m currently flying A-320, I´ve also flown B 737(300 and 800), and MD88. It´s true that at the beginning the new airbus received a lot of heat from pilots. After all they were trying to reinvent cockpits UI from 0. This led to a series of design accidents (due to initial design mistakes ) like the one on the article. The initial idea it´s not bad: reducing weight (removing all mechanical and hydraulic controls), inventing the glass cockpit, simplified system management, etc.. It took over a decade to polish the cockpit (and the whole airplane, that had tons of electronics related failures all around) to it´s actual safe and workable state. Those issues, plus the idea that pilots had to readjust your whole idea of a cockpit, were the ones that created that opposition. The opossition it's almost gone now, although in general we pilots still prefer Boeing aircraft (at least in Europe). Airbus airplanes fly very nicely and are great too. But now that we are used to the new IU, the concept problems are still there. Main diference between flying normal fly controls and a moving auto-throttle and airbus fly-by-wire: -Airbus throttle levers don´t move while the auto-thrust is changing the power setting. All the other airplanes as far as I know do it. -Airbus side-sticks don´t move when the autopilot or the other pilot is giving an input. Also as somebody explained above, the inputs are added, you can end with a double (or zero input), if you forget to push the priority button (in stress situations like last second corrections to land it´s easy to forget it). Why this is a mistake? because when flying a modern airliner you have an excess of information to process, all at once. A moving auto-throttle let´s you know what the engines are doing through your hands, without having to look at a tiny indicator at the instruments. Also it let´s you override the auto-throttle briefly because you need more power or less power at a given moment, without having to disconnect it. With airbus auto-thrust either the airplane or the pilot has the control, and you have to manually takeover. This may be dangerous at an approach that it´s already hard enough with cross winds or heavy rain. The same apply to the side-stick. Normal autopilots move the fly controls at the cockpit while actuating them. This let´s you know what the autopilot it´s doing. And of course when a pilot it´s flying manually, the other pilot knows exactly what he is doing ALL THE TIME. He can slightly correct a maneuver without having to take over the controls from zero. Airbus has wiped a layer of fundamental information available to the pilots, increasing the information overoosd through the vision. It´s the equivalent of driving a race car with a playstation control. Most of the time this information it´s not used(like in cruise), but you really, REALLY need it when things become hairy close to the ground. In fact I routinely disconnect the auto-thrust to land, with the Boeing and MD88 I kept it engaged. Airbus knows this, but it´s too late to change 20 years of airplane development. They´ll need to change too many things (systems, procedures, certification, instruction), also right now it´s easy to change from flying let´s say a A320 to a A 330, due to having very similar cockpits and systems (that´s a great idea). The conversion course it´s short and relatively cheap. Changing the controls would make this fleet changes much more expensive and time consuming to Airlines. Edit: overall small changes to improve clarity.

jacquesm 12y ago
It's a real pity that the resistance to improving (or even fixing!) these shortcomings is mostly economic in nature, I can't imagine that the pilots would object to having these issues solved once and for all. Unfortunately pilots don't have a whole lot of options to exert meaningful pressure on aircraft manufacturers.
- oftenwrong 12y ago
  >Unfortunately pilots don't have a whole lot of options to exert meaningful pressure on aircraft manufacturers. If a group of pilots came together to declare an aspect of a plane's functionality as unsafe, wouldn't that send strong signals to the public, governments, ICAO, etc? Even if those signals were ignored initially, they could become more important later if an accident occurred in which the same functionality is (or "was"?) involved. At that time, the media groups, great lovers of scandal and tragedy, would come out and say, "Functionality X contributed to the accident. These pilots warned about the dangers of functionality X back in year Y, and everyone ignored them." After that, the pilots' opinions might be more heavily considered.
- metacorrector 12y ago
  and when they do apply pressure on Airbus from their side of the cockpit, they can't tell if countervailing pressure is being applied from the other side?
userbinator 12y ago
I think the concept you're referring to is self-indicating, or in this case the lack thereof. A much more commonplace example that comes to mind is volume control knobs on things like stereo amps; the "old style" had a knob directly connected to the potentiometer controlling the volume, so it was self-indicating and at a glance (or even just by feel if the pointer is tactile) you could see what position it was set to. Now it seems fashionable to use knobs that don't have any markings and will spin continuously, meaning that you have to look at the display to see what the setting is. To me it sounds like a cost-cutting measure - to have controls that move, there has to be an actuator in them, which makes it more expensive. My stereo which has self-indicating volume knobs actually contains a small motor that rotates them when I use the remote control.

mdc 12y ago

"Airbus did not anticipate that a pilot would stall a plane and fly it directly into the ocean" Stalling and flying into the ground have been two common failure modes since flying began and they often happen in sequence. I would think they would be high in the list of misuse cases any aircraft designer would consider. "we should refrain from being quick to judge which is more or less intuitive." We should not be quick to judge which UI is more effective, but by definition we can be quick to judge which is more intuitive. In fact, the more time you spend with a system, the less qualified you are to comment on whether it is intuitive. Judging whether a UI is intuitive should take very little time and no expertise past understanding basic operations. I'm certainly not qualified to judge, but I'd think anyone who has experience with modern flight systems would be qualified to comment on whether a particular design was intuitive.

lutorm 12y ago
I think he meant "stall a plane and keep it stalled for many minutes, flying it into the ocean". Stall/spin accidents are common, but they normally arise from loss of control at low altitude when there's not enough time or space to recover.

mikeash 12y ago

The stalling was a consequence, the fundamental problem is that there's no indication that two pilots are fighting over the plane. And that is an obvious problem. It's literally one of the first things you cover when you begin learning how to fly. The instructor will sit you down and walk through how you hand off the controls and agree who's flying the plane at any given time. Likewise, when flying with another pilot you always do a positive handoff. "You have the plane." "I have the plane." The physical link between the two sets of controls is an important backup mechanism that ensures this happens. Not linking the two sets of controls is insane. It's unrelated to the different approaches to fly-by-wire. Taking two radically different control inputs and simply averaging them together makes no sense.