4 ms·

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:

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.

mikeash 12y ago
Really, I don't think there's a point to discussing ways to mitigate non-linked controls. It's basically like saying, well, if you're going to keep poisonous cobras in the baby's crib, here are some ways to help avoid getting bitten.... Now, there's no reason you can't have a full fly-by-wire system with all the conveniences and safety advantages that implies along with such a system. The two controls could be mechanically linked before feeding into the system, or they could be completely mechanically independent and then use a force feedback system to link the electronically. There are interesting arguments on both sides of the Airbus fly-by-wire system, but it's ultimately a separate question.
- snom390 12y ago
  Well, there's a reason: Cost. Certifying and retrofitting force feedback controls on existing Airbus planes will be very expensive, and since the current safety record is so good, it's probably not going to happen unless another accident happens attributable to the same design decision.
  - mikeash 12y ago
    That's a good point, I was thinking from the perspective of designing a new system, not dealing with the large installed base.
snom390 12y ago
They do have a switch to override controls on airbus planes. But of course, that's not much use when both pilots are in panic mode. AFAIK they could see how the controls were manipulated on the FDR, and I think both pilots actually applied nose-up inputs for some time.

mikeash 12y ago

Really, I don't think there's a point to discussing ways to mitigate non-linked controls. It's basically like saying, well, if you're going to keep poisonous cobras in the baby's crib, here are some ways to help avoid getting bitten.... Now, there's no reason you can't have a full fly-by-wire system with all the conveniences and safety advantages that implies along with such a system. The two controls could be mechanically linked before feeding into the system, or they could be completely mechanically independent and then use a force feedback system to link the electronically. There are interesting arguments on both sides of the Airbus fly-by-wire system, but it's ultimately a separate question.

snom390 12y ago
Well, there's a reason: Cost. Certifying and retrofitting force feedback controls on existing Airbus planes will be very expensive, and since the current safety record is so good, it's probably not going to happen unless another accident happens attributable to the same design decision.
- mikeash 12y ago
  That's a good point, I was thinking from the perspective of designing a new system, not dealing with the large installed base.

snom390 12y ago

They do have a switch to override controls on airbus planes. But of course, that's not much use when both pilots are in panic mode. AFAIK they could see how the controls were manipulated on the FDR, and I think both pilots actually applied nose-up inputs for some time.