Air Asia Indonesia Lost Contact from Surabaya to Singapore

[EMIT]

Woof Woof

WesWall - Luckily the 140 + pages are scribbled full mostly by people who don't fly the Bus themselves, or do not fly any airplane at all.

[Coagie]

I wonder if the copilot just happened to come upon a particularly bad spot of weather and executed a turn and climb to avoid it, and it just happened to be the moment when his protections were lost, when the FAC'S were disabled? If you are accustomed to the protections, you might not be gentle or precise with the sidestick, if you were making a relatively sudden maneuver.

[NigelOnDraft]

If you are accustomed to the protections, you might not be gentle or precise with the sidestick, if you were making a relatively sudden maneuver.

I probably have over 5K hours on the A320. I am not "accustomed" to the protections i.e. in my flying I have not once (AFAIK) got near to them being triggered. If I did I would get a phone call

In the Sim, yes - they are demonstrated and used in a few emergency drills: GPWS & Windshear. For either of them to trigger, you need to be near the ground, something not a feature of this accident.

Apart from those 2 drills, I cannot think of any realistic scenario where an Airbus pilot would intentionally "rely" on the protections?

[Coagie]

Maybe whenever control is turned over to the pilot from the computer, it should be treated similar to a loss of cabin pressure with the initial focus of the pilots being to get to a lower altitude, so the aircraft is easier to handle manually. Remember, one of the biggest reasons, day to day, that airlines want the computer to control the airliner, is to enable it to fly at high altitude for fuel efficiency. Because each flight will have a different weight and center of gravity, the computer can trim accordingly, but at high altitude, it might take precious time for pilots to get the "feel" of the aircraft. So why not drop down 10,000 feet or so (a dive might not be necessary), until you are comfortable, that you are in control?

[training wheels]

A search for alpha floor activation reveals that not too many incidences have occurred in the past where alpha floor protection was used in anger.

[NigelOnDraft]

Maybe whenever control is turned over to the pilot from the computer...

When the pilot normally "takes control" it is from the Autopilot - nothing to do with the "computer" typically referred to above as in HAL / Control Laws etc. Nobody rated on type should have an issue in Normal Law manual flying at cruise Alt.

If you mean when there is a significant failure such that the AP drops out AND you get a control law degradation, then yes, a descent is advised. IIRC it is 4000' below the normal "Max Alt" to avoid triggering the (now more sensitive) Stall warning.

[triskele]

timeline

I would like to confirm the timeline, Reuters quotes the minister thus...'At 6:17 a.m. on Dec. 28, three minutes after air traffic control unsuccessfully tried to make contact and asked nearby aircraft to try to locate QZ8501, the A320 turned to the left and it began to climb from its altitude of 32,000 ft (9,750 meters), Jonan told a parliamentary hearing.'
If this is so it appears the cockpit was rather busy before the turn and climb, during whichthe FACs were turned off?

[Coagie]

"If you mean when there is a significant failure such that the AP drops out AND you get a control law degradation, then yes, a descent is advised. IIRC it is 4000' below the normal "Max Alt" to avoid triggering the (now more sensitive) Stall warning."

You mean I'm not the first to think of this? ...Yes that's what I mean. I'm thinking of the attitude taken toward the issue. Loss of cabin pressure causes an immediate reaction to get to a lower altitude. It doesn't cause "Let's find out where the hole is, then get to a lower altitude". So similar, but maybe not as intense, sense of urgency could apply to loss of or degraded automation.
Of course I'm using "computer" to mean whatever type of flight control automation applies to whichever aircraft or situation. If I specified "HAL" or "Airbus", the comment might get modded out.

[Radix]

Coagie is onto something. Some pilots have become so used to the fact of operating in the coffin corner (mach overspeed vs. stall) that they have become oblivious to the fact that it is called coffin corner (who came up with that term)?

Shouldn't the first reaction when having to hand fly at that altitude be, I need to get lower as my margin for error here is extremely small, hence I need to give myself some room to be able to safely handfly i.e. I will descend now.

It appears some pilots instinctively do the exact opposite! They start to climb. Why is that?

[silverstrata]

glendaledoon:

It boils down to this. do you want a plane that obeys a computer or obeys a human pilot? I'll take a human pilot.

The problem is rarely the computer. The problem (and this applies to all industries) is most often the computer-human interface.

In trying to cope with so many variables the flight computer gets ever more complex. But where the computer has to interface with the human, things have to be simplified down to basic commands. This difference in capability means the human operator has no chance of understanding what the computer is trying to do, behind the scenes; and so if there are any i/o errors or hardware malfunctions, there is no chance a human can instantly trouble-shoot the problem.

The answer is not to go back to basic stick and rudder flying. The answer is to have more redundancy in the inputs, and not allow the computers to be disconnected. (Just, as you would not dream of disconnecting the flight control hydraulics.)

[MountainBear]

It boils down to this. do you want a plane that obeys a computer or obeys a human pilot?

I'll take a human pilot.

I'll take the computer.

Here's the thing about a computer--it still has enormous upside because the software is the result of a collective endeavor. It is true enough that in short run there might be more accidents but in the long run it will produce significantly less accidents than any human. We have seen this is every field that computers have been involved in.

It is not a question of IF the computer will take over for the human pilot, only a question of WHEN.

[aircarver]

.... "and not allow the computers to be disconnected."

What happens when they start releasing 'magic smoke' ....

.

[misd-agin]

Let the investigation run it's course. We don't know if something unusual happened, something happened that wasn't known to the crew(s), if this was a good airplane and control was lost due to poor flying ability, or various other possible combinations.

[Ian W]

Originally Posted by silverstrata

The problem is rarely the computer. The problem (and this applies to all industries) is most often the computer-human interface.

In trying to cope with so many variables the flight computer gets ever more complex. But where the computer has to interface with the human, things have to be simplified down to basic commands. This difference in capability means the human operator has no chance of understanding what the computer is trying to do, behind the scenes; and so if there are any i/o errors or hardware malfunctions, there is no chance a human can instantly trouble-shoot the problem.

The answer is not to go back to basic stick and rudder flying. The answer is to have more redundancy in the inputs, and not allow the computers to be disconnected. (Just, as you would not dream of disconnecting the flight control hydraulics.)

I think that using the hydraulics as an analogy is not quite correct. Hydraulics have no power of decision they do what they are told and without a computer interface that is precisely what the pilot makes them do. The computers do precisely what the systems analyst and software designer wanted them to do when the pilot makes inputs and the environmental conditions are in particular states as sensed through various replicated sensor systems.

The crew will quite often be in the position of asking "what is it doing now? why did it do that? or what is it going to do next?" usually with the occasional thrown in for emphasis.

The systems analyst, software designer and acceptance engineers often ask: "What did they do that for? Who would have thought a pilot would do that? or Surely the winds/temperatures can't do that?" and other comments as they have to consider every possible combination - not every likely combination but all of the unlikely ones too. To avoid getting too complex, they have an 'otherwise case'. So if the software finds things are not working the 'otherwise case' is to fail and hand the bag of bolts to the pilot. The pilot doesn't have to be a magenta line follower to be surprised by this and however good cannot know everything the computer was doing and why it was doing them. If possible the pilots are expected to keep, or get, the aircraft straight and level then try to solve the problems. This may not be easy if they have totally lost situational awareness and the computer system just dropped them the bag of bolts.

All this was known and discussed many years ago - see http://csel.eng.ohio-state.edu/produ..._surprises.pdf Automation Surprises. (I made a similar comment on the Tech Log).

It is a pity that the pilot is not only not 'IN the loop', or 'ON the loop' but is often well 'OUT of the loop' when it comes to the automation and what and why it is doing things. It takes a level of concentration from the pilot to retain situational awareness, but if the computer system doesn't communicate - like an introverted PF with a steep authority gradient in CRM - it can lead to problems when things go awry.

[MountainBear]

It appears some pilots instinctively do the exact opposite! They start to climb. Why is that?

This is a fascinating psychological topic. The general consensus in the literature is that pilots revert to a primitive concept that equates flying with climbing. This makes sense in that in order to fly one must climb up from the ground. What do you do when you want to fly? You go up. Mentally, the pilot goes back to square one and tries to take off all over again. In the AF447 case it was revealed that all the way into the sea the pilots kept trying to get the plane to /climb/ and even verbalized that intent. When in fact is they have just flown the plane they would have been OK.

What still remains to be understood is why some pilots revert to an incorrect cognitive map under stress. Is it that they were poorly trained to begin with? Or perhaps they have some basic psychological predisposition?

[DrPhillipa]

The answer is not to go back to basic stick and rudder flying. The answer is to have more redundancy in the inputs, and not allow the computers to be disconnected. (Just, as you would not dream of disconnecting the flight control hydraulics.)

Moving from 3 pitots to 17 would not help much as they have to be in the same aspect to the air stream as each other to provide comparable results and would likely all freeze up or not. Then you have the problem of what to do when x agree and y show different numbers to the x and each other etc. Problem is that near coffin corner you need one RIGHT answer. Any sort of mean value or even a most probable value is bound to be WRONG to an unknown lesser or greater degree.

The computers are not disconnected on UAS. The AP may "disconnect" itself, some protection subroutines which depend on IAS may decline to function (and announce that fact) but the computers still move the control surfaces - unless they all fail and then you have Mechanical Law and you really are in some trouble whether in a Bus or a 787.

[Coagie]

What happens when they start releasing 'magic smoke' ....

That's what causes them to stop working. The "magic smoke" is let out. Sometimes a bigger fuse isn't the answer.
When it's not the computer,
and it's not a sensor or other input device,
it can be, that the power supply voltage is off, making the 5 volts or 12 volts, whichever applies, below threshold, where it's seen as a "0" instead of a "1", causing weird, intermittent, and sometimes unpredictable problems. This sometimes happens, when the power supply is also the battery charger, and the charging voltage is wrong from maladjustment or a cell in a battery is shorted, drawing enough current to cause a voltage drop.
Some or none of this may apply to QZ8501, but might be why switching out an FAC might not have remedied the problem (assuming the reports of maintenance issues with that system on that particular aircraft have any truth to them).

[320goat]

People are confusing the classic coffin corner with min maneuver speed (Vls) and max maneuver speed. If you are flying at MAX REC FL you probably have about 20kt split but closer to 35-40kt split for coffin corner.

[glendalegoon]

silverstrata

I really don't think you know much about planes...esp the concept about disconnecting the hydraulics

well, in certain scenarios with the 737, that is exactly what you do, you turn off the hydraulics esp to the rudder. (others can look up the rudder hardover crash).


I'll take the human and let him have the controls and have him be ''in the loop".

Just because you have 10 men working on computer software, doesn't mean they are not compromising...remember the idea that an elephant is a mouse designed by committee.

Lindbergh went alone for many reasons...among them the decision making process was his alone and not left up to others. I think his words were something like: one boy is a boy, two boys are half a boy, and three boys are no boy at all. (see ''the spirit of st louis")


So, when they make the computerized non pilot plane, I hope you volunteer to be the first passenger.

[aircarver]

"That's what causes them to stop working. The "magic smoke" is let out. Sometimes a bigger fuse isn't the answer."

There's been a lot of discussion of electrical equipment that the pilot can't shut off.

As the 'beneficiary' of a smoky in panel fire, (killed with the CB) I am not so thrilled by this kind of thinking.

.