What really happened aboard Air France 447 • Hacker News Board

Re: What really happened aboard Air France 447

#321

Post by accountoftheday » Fri, Dec 09, 2011, 12:02 AM UTC

Caballera wrote: post #299

jarek wrote: post #131

Earlier quoted context omitted.

The Popular Mechanics account of AF447 leaves out some quotes and doesn't explain their content very clearly, unfortunately, but it appears they were doing that, more or less. "02:11:37 (Robert) Commandes à gauche! Left seat taking control! [...] At any rate, Bonin soon after takes back the controls." Sometime after 2:12:15: "As the plane approaches 10,000 feet, Robert tries to take back the controls, and pushes forw…

i don't know these people and I'm not a pilot, but is it possible the Bonin wanted to crash the plane? I find it hard to believe that he would continue to pull back on the stick almost the entire time and not 'share' that information, and after Robert took control (by stating 'Give me the controls!'. Just wondering if this is something that would be looked into.

I believe Bonin's wife appears on the passenger manifest, which makes a suicide even more unlikely.

Re: What really happened aboard Air France 447

#322

Post by jarek » Fri, Dec 09, 2011, 1:07 AM UTC

Florin_Andrei wrote: post #249

jrockway wrote: post #224

Earlier quoted context omitted.

(And of course, in planes that are not certified for stalls, you can't really practice full stalls and have to train on approach to stalls instead.) Of course, very little airliner training happens outside a simulator, which can you can stall without damaging anything.

> Of course, very little airliner training happens outside a simulator, which can you can stall without damaging anything. Maybe they should apply mild taser shocks to pilots stalling in the simulator. I'm not being snarky. There should be some kind of physical consequence of making bad mistakes, otherwise it's too disconnected from reality.

The result of that would be pilots doing everything in their power to avoid entering stall and thus learning less about behaviour while in stall and exiting stall. I'm not sure that's a desirable outcome. Sometimes you have to fail to learn.

Re: What really happened aboard Air France 447

#323

Post by nradov » Fri, Dec 09, 2011, 1:55 AM UTC

crististm wrote: post #307

acabal wrote: post #48

That was one of the tensest things I've read in a while. My heart was pumping up until the end. The level of stress, confusion, and terror those pilots, not to mention the passengers, must have experienced must have been truly terrible.

My thoughts exactly. While reading this I could not think about the same counter-intuitive reaction that people have when they drive and the car slips. Most people steer in the direction of the road when the single action to regain control is to slightly steer in the direction of the slippage.

Except that steering in the direction of the slippage may not be the correct action at all, at least in some vehicles. http://www.oregon.gov/OSP/PATROL/safety_tip_slide_control.sh...

Re: What really happened aboard Air France 447

#324

Post by lutorm » Fri, Dec 09, 2011, 2:48 AM UTC

crikli wrote: post #289

Florin_Andrei wrote: post #245

Earlier quoted context omitted.

> without valid airspeed there's a risk of overspeed which can cause a new set of problems What problems specifically? > Nobody believed a passenger aircraft would be so stable during a full stall. What was the plane "supposed" to do during the stall? If you're inside the plane, how does it feel when the plane has stalled?

> What problems specifically? All aircraft have a VNE speed, the NE standing for "never exceed." Going beyond this threshold invites structural failure and loss of control. > If you're inside the plane, how does it feel when the plane has stalled? I've mentioned this in another comment, but the body is a horrible judge of spatial reference. How the body is going to feel during a stall is tough to predict, particularl…

Not all planes are stable in a full stall, some lose longitudinal stability and will be almost impossible to keep level.

Re: What really happened aboard Air France 447

#325

Post by crikli » Fri, Dec 09, 2011, 2:54 AM UTC

lutorm wrote: post #324

crikli wrote: post #289

Earlier quoted context omitted.

> What problems specifically? All aircraft have a VNE speed, the NE standing for "never exceed." Going beyond this threshold invites structural failure and loss of control. > If you're inside the plane, how does it feel when the plane has stalled? I've mentioned this in another comment, but the body is a horrible judge of spatial reference. How the body is going to feel during a stall is tough to predict, particularl…

Not all planes are stable in a full stall, some lose longitudinal stability and will be almost impossible to keep level.

Oh sure but most passenger planes are pretty docile a stall.

Re: What really happened aboard Air France 447

#326

Post by shinratdr » Fri, Dec 09, 2011, 3:16 AM UTC

ojosilva wrote: post #180

Nick_C wrote: post #120

Earlier quoted context omitted.

> 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 dif…

I utterly agree on reducing continuous and loud sound warnings in the cabin. This 1996 757 Aeroperu crash recording is quite scary: http://www.youtube.com/watch?v=G5QSBlYTJ1Y They had no functioning pitot tubes and lots of contradictory indications, which triggered a storm of alarms, most of them false. Pilots spend quite some time trying to shut alarms off while trying to figure out their situation with air control.…

I really appreciate that recording because it helps empathize with exactly how disturbing it would be to be in that situation.

Re: What really happened aboard Air France 447

#327

Post by groby_b » Fri, Dec 09, 2011, 3:54 AM UTC

mikeash wrote: post #226

flyingkiwi wrote: post #32

Earlier quoted context omitted.

IIRC, that was lesson 1, minute 2 (right after take-off). The previous commenter who said that wouldn't think to ask because it is akin to asking 'is the computer plugged in' is probably right (though the captain should have noticed it when he was observing). Serious design flaw, and tragic human error with devastating results. :(

I'm actually mildly surprised that it waited until you were in the air. I always brief that before takeoff whenever I take another pilot along. But yes, very basic stuff in any case, and amazing that they were not following this standard procedure.

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.

Re: What really happened aboard Air France 447

#328

Post by joss82 » Fri, Dec 09, 2011, 3:57 AM UTC

crististm wrote: post #307

acabal wrote: post #48

That was one of the tensest things I've read in a while. My heart was pumping up until the end. The level of stress, confusion, and terror those pilots, not to mention the passengers, must have experienced must have been truly terrible.

My thoughts exactly. While reading this I could not think about the same counter-intuitive reaction that people have when they drive and the car slips. Most people steer in the direction of the road when the single action to regain control is to slightly steer in the direction of the slippage.

The correct course of action is to declutch so that the wheels get back in sync with the road. Of course, you cannot do that on an automatic car.

Re: What really happened aboard Air France 447

#329

Post by einhverfr » Fri, Dec 09, 2011, 5:05 AM UTC

tankenmate wrote: post #255

einhverfr wrote: post #160

Earlier quoted context omitted.

yeah, I agree with that. Also there's another factor in that stall warnings may have been seen as an ADIRU malfunction rather than an actual stall. In those cases, I suppose pulling back might make some sense if you think you have bad ADIRU input and the plane is in normal law.

I think the whole point is that in almost all circumstances an ADIRU failure will lead directly or indirectly to alternate law. Hence the correct procedure should be to assume alternate law and cross check. Once your instruments start failing left, right, and centre you should go into what I call "advanced free fall" mode, check horizon (true, false or otherwise), check altitude, check parachute, repeat... If you hit…

I was thinking of the Qantas and Malaysian Airlines mishaps where faulty ADIRU's lead to sudden uncommanded changes in altitude and eventual stall warnings.

Re: What really happened aboard Air France 447

#330

Post by mike_ivanov » Fri, Dec 09, 2011, 5:44 AM UTC

Florin_Andrei wrote: post #247

einhverfr wrote: post #128

Earlier quoted context omitted.

IANA Pilot. I do make aerodynamically correct fixed-wing and lifting-body type paper airplanes, however, and I have had a LOT of fun playing with aerodynamics in this hobby. One thing to keep in mind regaring stall is that it's 100% dependent on angle of attack, not speed (something Popular Mechanics gets entirely wrong). What happens basically is that at a high angle of attack the air layer doesn't track the wing su…

> One thing to keep in mind regaring stall is that it's 100% dependent on angle of attack, not speed (something Popular Mechanics gets entirely wrong). What happens basically is that at a high angle of attack the air layer doesn't track the wing surface properly and so you are deprived of standard lift. So the air layer on the back "peels off", and you have turbulent flow on the back, instead of laminar, is that righ…

Exactly.

http://en.wikipedia.org/wiki/Stall_(flight)