8 ms·

Recently there have been many articles and different takes on the AF447 crash. To anyone who is truly interested I would highly recommend to read the official F

by jnsaff2 12y ago

Recently there have been many articles and different takes on the AF447 crash. To anyone who is truly interested I would highly recommend to read the official Final Report [1] as it gives a much more nuanced and complete picture than the journalistic dramatizations and heavy handed simplification. [1] http://www.bea.aero/en/enquetes/flight.af.447/rapport.final.en.php http://www.bea.aero/en/enquetes/flight.af.447/rapport.final....

MichaelGG 12y ago
But really, all the other interesting stuff aside (cascading errors, modal input), it really boils down to the undefensible decision by Airbus to average inputs from both pilots.
- MrBuddyCasino 12y ago
  This one is really mind blowing. Also I don't get why they switched to joysticks instead of the traditional yoke. With mechanical feedback, yokes should be much more intuitive. I'd love to hear a pilot's opinion who has used both.
  - jasode 12y ago
    Captain Chesley Sullenberger (the famous pilot of the Hudson River crash landing) has the opinion that mechanically linked yokes (Boeing philosophy) is superior to independent fly-by-wire joysticks (Airbus philosophy). A video from CBS shows a very eye-opening demonstration of tactile feedback the mechanical linkage can provide. It's a feedback loop that the non-flying pilot can't ignore. http://youtu.be/kERSSRJant0?t=3m9s http://youtu.be/kERSSRJant0?t=3m9s However, it doesn't mean there aren't other pilots who prefer fly-by-wire joysticks and can list (safety) advantages over mechanical linkages.
  - mikeash 12y ago
    I'm a glider pilot, and gliders universally use sticks (presumably because they're mechanically simpler and considerably smaller, and space is at a premium). I've flown planes with yokes before, and have on rare occasions more recently, and I don't like the feel of it at all. The stick gives much better control and feedback in my opinion. However, that could just be because it's what I'm used to. In any case, I don't think the joystick is a problem, but rather how it's implemented, with no feedback in the system. A yoke implemented in the same way would have had the same problem.
    - parados 12y ago
      I used to be a glider pilot (and an instructor). A disadvantage of a yolk is that when you are flying one handed and apply g (or encounter turbulence) the g forces on your arm induce roll inputs, a stick reduces that. As most powered aircraft are optimised for cruising at 1g this is not so much of a problem but with gliders varying g forces are quite common. The other consideration is that with most light powered aircraft the pilot and passenger get in from the side and a traditional stick sprouting out of the floor gets in the way, a yolk doesn't. With gilders you usually enter from above so the stick is not a problem.
- snom390 12y ago
  No, I don't think it boils down to that. It was just a one of many different design decisions (and philosophies) that has provided a stellar safety record for Airbus planes right up to the point where it contributed to an accident. Remember that it's easy to criticize such decisions in hindsight, but the decision was taken for a reason, and approved by government agencies at the time.
  - mikeash 12y ago
    Positive exchange of control and knowing who is flying the plane is literally one of the first things you cover when learning to fly, before you even get in an airplane for the first time. Averaging inputs in this way interferes with that in such an obvious fashion that it's really inexcusable. I really don't believe this is purely a hindsight thing. Sure, they made this decision for a reason and it was approved my government agencies at the time. However, that doesn't mean I can't think those reasons don't override the fundamental principle of always knowing who's in control of the airplane, and that the government agencies were wrong to approve it. This crash is fairly amazing in how basic a failure it was. The two main things that went wrong (confusion over who was controlling the airplane, and not putting the nose down in a stall) are both extremely basic things. It's the computing equivalent of not checking to see if your machine is plugged in, except that people die because you forget to check. It seems that training was deficient when it came to the basics, and I also think that the non-linked averaged controls are completely inexcusable and should be eliminated.
    - msandford 12y ago
      Or, if you're going to INSIST on doing something that's maybe not too smart (non-linked controls) there are a bunch of things you could do to fix the problem: 1. Have a switch that determines "who is flying the airplane" i.e. which controls are active 2. Implement some kind of feedback even if it's not direct mechanical such as moving both joysticks with a little bit of servo force: not enough to overpower one's hand but enough for the non-flying folks in the cockpit to see 3. Have an "averaging error" sound, light up, whatever if the two joysticks have inputs which are too far from one another to make sense. This isn't great because you still have to pick one joystick to have priority and that might be non-intuitive to pilots Ultimately I think the biggest problem with the Airbus design is that it adds an extra level of indirection between pilot's inputs and airplane course. In most aircraft if you let the controls return to "neutral" the airplane will slowly return to neutral as well. In an Airbus if you let the controls return to neutral the airplane just continues to do whatever it was you were doing; if you're climbing it continues to climb; turning it continues to turn; etc. http://www.apollosoftware.com/products/flybywire/flybywire_english.pdf http://www.apollosoftware.com/products/flybywire/flybywire_e... It seems to me that this is how the problem occurred; someone yanked back on the joystick and nobody else noticed it and then it returned to neutral. But the airplane continued to try and hold attitude up. In a Boeing airplane that wouldn't be a few seconds of joystick back, it'd be a continuous holding of the yoke towards the pilots making it very obvious what was happening. The pilots shouldn't have an integrator between them and the airplane because it makes the airplane handle in very non-intuitive ways to the first 80 or so years of aviation as well as basically all the smaller planes that pilots train on prior to flying big jets.
- tonylemesmer 12y ago
  It is ridiculous. Taking 2 inputs and generating an output neither pilot requested.
- phkahler 12y ago
  >> But really, all the other interesting stuff aside (cascading errors, modal input), it really boils down to the undefensible decision by Airbus to average inputs from both pilots. That's funny. I thought it was because they don't get sufficient stall training. The input blending would certainly be a contributing factor, but they would have made it if the guy did exactly nothing instead of the wrong thing. This goes along with my feeling about the SF accident where the (was it Korean?) pilots don't generally fly planes but rely on the automation.
  - mikeash 12y ago
    Both are critical. With proper input linkage, the other pilot would have realized that the panicked one was doing the wrong thing, and made him stop. With proper stall training, the panicked pilot wouldn't have misbehaved. Part of the reason why you have two pilots in the first place is so they can check each other and make up for situations where one pilot has a lapse of judgment, or panics, or is just improperly trained.
  - snom390 12y ago
    I think what was pointed out in the report was a lack of training on high altitude hand flying. The pilots got plenty of stall training, but mostly in take-off / landing scenarios (which is realistically when you're most likely to experience a stall).

by jnsaff2 12y ago

MichaelGG 12y ago

But really, all the other interesting stuff aside (cascading errors, modal input), it really boils down to the undefensible decision by Airbus to average inputs from both pilots.

MrBuddyCasino 12y ago
This one is really mind blowing. Also I don't get why they switched to joysticks instead of the traditional yoke. With mechanical feedback, yokes should be much more intuitive. I'd love to hear a pilot's opinion who has used both.
- jasode 12y ago
  Captain Chesley Sullenberger (the famous pilot of the Hudson River crash landing) has the opinion that mechanically linked yokes (Boeing philosophy) is superior to independent fly-by-wire joysticks (Airbus philosophy). A video from CBS shows a very eye-opening demonstration of tactile feedback the mechanical linkage can provide. It's a feedback loop that the non-flying pilot can't ignore. http://youtu.be/kERSSRJant0?t=3m9s http://youtu.be/kERSSRJant0?t=3m9s However, it doesn't mean there aren't other pilots who prefer fly-by-wire joysticks and can list (safety) advantages over mechanical linkages.
- mikeash 12y ago
  I'm a glider pilot, and gliders universally use sticks (presumably because they're mechanically simpler and considerably smaller, and space is at a premium). I've flown planes with yokes before, and have on rare occasions more recently, and I don't like the feel of it at all. The stick gives much better control and feedback in my opinion. However, that could just be because it's what I'm used to. In any case, I don't think the joystick is a problem, but rather how it's implemented, with no feedback in the system. A yoke implemented in the same way would have had the same problem.
  - parados 12y ago
    I used to be a glider pilot (and an instructor). A disadvantage of a yolk is that when you are flying one handed and apply g (or encounter turbulence) the g forces on your arm induce roll inputs, a stick reduces that. As most powered aircraft are optimised for cruising at 1g this is not so much of a problem but with gliders varying g forces are quite common. The other consideration is that with most light powered aircraft the pilot and passenger get in from the side and a traditional stick sprouting out of the floor gets in the way, a yolk doesn't. With gilders you usually enter from above so the stick is not a problem.
snom390 12y ago
No, I don't think it boils down to that. It was just a one of many different design decisions (and philosophies) that has provided a stellar safety record for Airbus planes right up to the point where it contributed to an accident. Remember that it's easy to criticize such decisions in hindsight, but the decision was taken for a reason, and approved by government agencies at the time.
- mikeash 12y ago
  Positive exchange of control and knowing who is flying the plane is literally one of the first things you cover when learning to fly, before you even get in an airplane for the first time. Averaging inputs in this way interferes with that in such an obvious fashion that it's really inexcusable. I really don't believe this is purely a hindsight thing. Sure, they made this decision for a reason and it was approved my government agencies at the time. However, that doesn't mean I can't think those reasons don't override the fundamental principle of always knowing who's in control of the airplane, and that the government agencies were wrong to approve it. This crash is fairly amazing in how basic a failure it was. The two main things that went wrong (confusion over who was controlling the airplane, and not putting the nose down in a stall) are both extremely basic things. It's the computing equivalent of not checking to see if your machine is plugged in, except that people die because you forget to check. It seems that training was deficient when it came to the basics, and I also think that the non-linked averaged controls are completely inexcusable and should be eliminated.
  - msandford 12y ago
    Or, if you're going to INSIST on doing something that's maybe not too smart (non-linked controls) there are a bunch of things you could do to fix the problem: 1. Have a switch that determines "who is flying the airplane" i.e. which controls are active 2. Implement some kind of feedback even if it's not direct mechanical such as moving both joysticks with a little bit of servo force: not enough to overpower one's hand but enough for the non-flying folks in the cockpit to see 3. Have an "averaging error" sound, light up, whatever if the two joysticks have inputs which are too far from one another to make sense. This isn't great because you still have to pick one joystick to have priority and that might be non-intuitive to pilots Ultimately I think the biggest problem with the Airbus design is that it adds an extra level of indirection between pilot's inputs and airplane course. In most aircraft if you let the controls return to "neutral" the airplane will slowly return to neutral as well. In an Airbus if you let the controls return to neutral the airplane just continues to do whatever it was you were doing; if you're climbing it continues to climb; turning it continues to turn; etc. http://www.apollosoftware.com/products/flybywire/flybywire_english.pdf http://www.apollosoftware.com/products/flybywire/flybywire_e... It seems to me that this is how the problem occurred; someone yanked back on the joystick and nobody else noticed it and then it returned to neutral. But the airplane continued to try and hold attitude up. In a Boeing airplane that wouldn't be a few seconds of joystick back, it'd be a continuous holding of the yoke towards the pilots making it very obvious what was happening. The pilots shouldn't have an integrator between them and the airplane because it makes the airplane handle in very non-intuitive ways to the first 80 or so years of aviation as well as basically all the smaller planes that pilots train on prior to flying big jets.
tonylemesmer 12y ago
It is ridiculous. Taking 2 inputs and generating an output neither pilot requested.
phkahler 12y ago
>> But really, all the other interesting stuff aside (cascading errors, modal input), it really boils down to the undefensible decision by Airbus to average inputs from both pilots. That's funny. I thought it was because they don't get sufficient stall training. The input blending would certainly be a contributing factor, but they would have made it if the guy did exactly nothing instead of the wrong thing. This goes along with my feeling about the SF accident where the (was it Korean?) pilots don't generally fly planes but rely on the automation.
- mikeash 12y ago
  Both are critical. With proper input linkage, the other pilot would have realized that the panicked one was doing the wrong thing, and made him stop. With proper stall training, the panicked pilot wouldn't have misbehaved. Part of the reason why you have two pilots in the first place is so they can check each other and make up for situations where one pilot has a lapse of judgment, or panics, or is just improperly trained.
- snom390 12y ago
  I think what was pointed out in the report was a lack of training on high altitude hand flying. The pilots got plenty of stall training, but mostly in take-off / landing scenarios (which is realistically when you're most likely to experience a stall).