What really happened aboard Air France 447 • Hacker News Board

Re: What really happened aboard Air France 447

#371

Post by delackner » Mon, Dec 12, 2011, 5:37 AM UTC

sk5t wrote: post #106

snowwrestler wrote: post #92

Earlier quoted context omitted.

I think the simplest solution to the mismatched stick issue is to use servo motors to replicate the old situation--the movement of each stick mirrors the movements of the other. A pilot wouldn't have to look for some stick position display, or indicator light, if they can easily feel the deflection of the stick.

My understanding--I am not an aviator--is that the current Boeing controls behave this way and have for a long time. Apparently there is a lot of disagreement between the Boeing/US and Airbus/EU schools of thought, with a preference for greater mechanical (rather than electrical) interaction with flight controls on the Boeing side.

The linked article said that Boeing indeed to behave this way, and frankly I am not boarding ANY Airbus flights in the future.

Re: What really happened aboard Air France 447

#372

Post by delackner » Mon, Dec 12, 2011, 5:48 AM UTC

Too wrote: post #153

greiskul wrote: post #14

Earlier quoted context omitted.

Which raises a very good question, when would you ever want that joystick behaviour?

I guess it could be a cheap workaround to always get smooth transitions when changing pilot. Imagine if one pilot holds full left and the other full right and you press a "switch now!"-button. You would need some kind of transition-period of maybe a second to avoid jerk which could be confusing for the pilot to not know when he has full control and when he is in transition.

Actually if both sticks are actually linked, the person taking over will find his stick already full-left, and have to actually pull it over to the right as part of "taking over". Such simplicity and it would result in none of this insanity.

Re: What really happened aboard Air France 447

#373

Post by assemble » Mon, Dec 12, 2011, 6:27 PM UTC

omegant wrote: post #362

assemble wrote: post #303

Earlier quoted context omitted.

Try 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.

Well not at 400' and 130knots... That is way they were performing a windshear maneuver ( incorrectly) at FL 340.

Fair 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.

Re: What really happened aboard Air France 447

#374

Post by groby_b » Thu, Dec 15, 2011, 3:00 AM UTC

mikeash wrote: post #340

groby_b wrote: post #327

Earlier quoted context omitted.

Same experience. Pre-flight briefing with instructor: "When I say 'I have the plane', do NOT fly the plane". But then again, that's a VFR flight in decent weather. I'd imagine it's a bit easier to get stressed in the middle of the night in a storm over the Atlantic with electrical failures.

I think another major difference is that in most planes, you can feel when the other guy is screwing around with the controls because they're connected, so you can yell at him to stop doing whatever he's doing. It seems to me that it would be worthwhile to fake this in a pure fly-by-wire environment. The added cost and weight of a force-feedback system on the control sticks should be minimal compared to the aircraft…

Wouldn't be surprised if that's one of the outcomes of this - you'll still have the ability to override the other stick, but you'll know you're overriding.