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AF447 final crew conversation - Thread No. 1

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AF447 final crew conversation - Thread No. 1

Old 19th Jan 2012, 11:45
  #1081 (permalink)  
 
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@jcjeant:

What will be their proposals to remedy this ... if any
They...Airbus... offered the BUSS option even before AF447.
But it will never be a standard for the A330 if not mandated so by the autorities.
AFAK it is standard on A380 and will be on A350.

Recently I heard about upcoming 'firmware' updates (Don't have it on paper yet):

The ECAM announcement of transition to another law will be accompanied with a brief statement for the reason why the transition took place.

The PDF message "USE MAN PITCH TRIM" will show up always when automatic trim is not available.
(e.g. Abnormal Attitude ?)
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Old 19th Jan 2012, 11:58
  #1082 (permalink)  
 
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@ BOAC

.......which is why I said "There has to be a tade off between safety features and system complexity" and why designers are paid to analyse these trade offs and make a judgement.

There are potential traps with many safety features which is why they all have pre set limits and automatic self checking and should generate fault messages when they are no longer working, and switch themselves off.

The decision to inhibit stall warning was most likely based on a balance between nuisance / erroneous warnings causing a hazardous situation in a circtical phase of flight and the likelihood of a plane still being airborne at less than 60kts.

For some safety features, the extra complexity is justified especially if the probability of failure of the safety feature is sufficiently remote and consequences fully understood and protected against, and also if it lets you know when it has thrown in the towel.

As I suggested in my post, deep stalls are probably not common enough to merit the added complexity of warning that an aircraft is in one, so our views may be overlapping a little here. I was just suggesting that a deep stall may possibly be detected without pitot pressure or normal stall protection.
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Old 19th Jan 2012, 12:40
  #1083 (permalink)  
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I understood your suggestion, but the SIMPLE way to handle deep stalls is not through software but by LESS reliance on automatics/cradle-grave protections and the like and just encouraging basic flying skills - which appear to have been absent in this 'first level' airline. The more the psychology encourages 'reliance' on something telling you you have screwed up, the more likely it is you will, as opposed to making sure you don't, and that is ignoring all the pitfalls of a software based system reliant on voting on multiple sensors.
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Old 19th Jan 2012, 14:40
  #1084 (permalink)  
 
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Having said that, if the type of deep stall that has occurred here can render the normal stall warning useless due to airspeed < 60kts, would it not be possible to derive a warning from a combination of high rate of descent / Vertical speed together with a high nose up attitude above a pre-determined or abnormal value?
A much simpler and reliable solution is to latch the stall warning once a (fully developed?) stall is detected then do not clear the condition until sensors show the aircraft to be flying (unstalled) again.

While clearly not the "cause" of this accident the stall warning re-appearing when the correct (ND) input was applied could not have helped.
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Old 19th Jan 2012, 15:38
  #1085 (permalink)  
 
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Maybe if stall warning is understood and respected for what it is, the airplane will not "deep" stall?
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Old 19th Jan 2012, 16:03
  #1086 (permalink)  
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Precisely, HN39
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Old 19th Jan 2012, 16:42
  #1087 (permalink)  
 
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Originally Posted by MurphyWasRight View Post
A much simpler and reliable solution is to latch the stall warning once a (fully developed?) stall is detected then do not clear the condition until sensors show the aircraft to be flying (unstalled) again.

While clearly not the "cause" of this accident the stall warning re-appearing when the correct (ND) input was applied could not have helped.
Define "sensors show the aircraft to be flying (unstalled) again" in the case where those sensor values are out of valid range. That is where the complex software comes back in with all the associated problems / risks.

Then consider dealing with a latched warning which is spurious (for reasons of sensor failure or whatever) and is going to block out other lower-level warnings you may actually need to deal with the real problem.

Think maybe the latched warning is going to need a cb / off switch ?
This crew ignored stall warning for some time. Thinking it was spurious ?
Think the 447 crew would have pulled that cb / switch ?
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Old 19th Jan 2012, 18:53
  #1088 (permalink)  
 
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Thumbs up

Post 1087 ....very very relevant. I would read and re-read it and then only come to making even the glimmer of a statment!
Read it. It has huge undertones and even bigger hidden statments.
I know the fella who wrote it ..
Read and then re-read!
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Old 19th Jan 2012, 19:18
  #1089 (permalink)  
 
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if789:
Originally Posted by MurphyWasRight
A much simpler and reliable solution is to latch the stall warning once a (fully developed?) stall is detected then do not clear the condition until sensors show the aircraft to be flying (unstalled) again.

While clearly not the "cause" of this accident the stall warning re-appearing when the correct (ND) input was applied could not have helped.
Define "sensors show the aircraft to be flying (unstalled) again" in the case where those sensor values are out of valid range. That is where the complex software comes back in with all the associated problems / risks.
If the sensors are out of valid range, for example airspeed <60kts, then the aircraft is not in a normal flying range and since it was last known to be stalled it most likely still is.

No need for fancy checks. the currently inhibited (likely to reduce spurious alarms on landing etc) "stall states" such as air speed <60kts would not be able clear the warning.

Importantly they would continue to inhibit -entering- the stall warning state.

As to spurious warnings due to (undetected) sensor failure the current logic would likely continue the stall warning if the sensor failed in a way to inidicate a stall so things would be no worse than they are now.

Mainly just pointing out that considering a bit of recent state history can allow for a more robust desging compared to trying to determine current state from a single snapshot of data.
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Old 19th Jan 2012, 19:25
  #1090 (permalink)  
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Far too complex and fraught with bear pits, boys and girls.

Far simpler/cheaper to put pilots in the cockpit who know that flying with 12 degrees nose up or so at FL380 is not a good idea, and you never know, they might be able to sort out some other problems too.
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Old 19th Jan 2012, 19:43
  #1091 (permalink)  
 
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Cool @ A380 Jockey

Post 1087 ....very very relevant. I would read and re-read it and then only come to making even the glimmer of a statement!
My post is even better if you click on the link!

Much of the article expresses ideas that have been posted in these threads (and argued about endlessly). But it was refreshing to see these opinions confirmed by a very experienced type-rated pilot, who also went out of his way to praise aspects of the airplane; clearly not a Boeing axe-grinder. These forums are so anonymous that it's hard to really know the AB experience of those expressing opinions on these problems.

I was shocked that the first post to respond to it said it had appeared here many times (?) and that it was nonsense. Then we had a feller who disagreed with that, and that was the end of that discussion.

Well heck, since you drive the Big Boy, go ahead and try to make a glimmer of a statement!
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Old 19th Jan 2012, 20:27
  #1092 (permalink)  
 
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Originally Posted by A380 Jockey
I know the fella who wrote it ..
Then perhaps you should ask him to have a look in his manuals a bit more often and also have a look at the interim reports. There seems to be some things he has forgotten or don't know.
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Old 19th Jan 2012, 22:27
  #1093 (permalink)  
 
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I do feel certain that were you to spring this scenario on pilots in a simulator without warning,less than half of them would have a successful outcome.

Safely flying Airbus requires something of a non-pilot mindset.




I guess this is why I never chose to fly the AB.
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Old 20th Jan 2012, 00:06
  #1094 (permalink)  
 
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Since you've never flown it, I'd like to know how you came up with that conclusion? The majority of pilots whom I've flown the A330 with would have handled it just fine, because they knew how to handle UAS events at altitude.
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Old 20th Jan 2012, 01:07
  #1095 (permalink)  
 
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I quoted the sim part at the top but chose to stay away after my friend told me his story landing at MIA when they couldn't control the aircraft so went around knowing they were going to crash, just didn't know where. Eventually they regained control and landed.

Something about a side stick control doesn't give me the confidence, especially if the FO is flying, of what is going to happen next. Mix that with a guy with low experience and another with not much more experience than the guy flying. Two pilots in a full stall and neither one could figure out why they were falling out of the sky? At least a yoke in both belly's would give them a clue. Maybe not in this case.
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Old 20th Jan 2012, 02:59
  #1096 (permalink)  
 
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the first post to respond to it said it had appeared here many times (?)
Why the question mark? It -has- appeared here many times. Read the thread.
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Old 20th Jan 2012, 03:22
  #1097 (permalink)  
 
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With regard to post 1087's link. Not rubbish at all.
For example this quote from the original article:
The real problem probably occurred immediately after the pilot flying grabbed the Sidestick and took over manually.
Unfortunately,airline pilots rarely practise hand-flying at high altitude and almost never do so without A/THR engaged.
As a result,we forget that the aircraft is very sensitive to control inputs at high altitude and overcontrol is the usual result.
About a month and a half ago I concluded over on the tech thread that this was initially a roll PIO event as best I could figure from the data. It really stands out as unusual in the period leading up to the stall (well, that and the high nose attitude.)
Call in overcontrol if you wish, but if it was really PIO, it was worse than that as far as demanding a response from the pilot.

The guys with the minimalist approach to aircraft control will probably never see PIO. If you are not that type of pilot though, you could have an unpleasant encounter.

PIO is funny, in that it is hard to stop once started., and it requires a change in piloting strategy to stop it.
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Old 20th Jan 2012, 04:37
  #1098 (permalink)  
 
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PIO is funny, in that it is hard to stop once started
That's why the O stands for oscillation.
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Old 20th Jan 2012, 06:27
  #1099 (permalink)  
 
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...but the more important letters are the P & I...
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Old 20th Jan 2012, 15:44
  #1100 (permalink)  
 
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...but the more important letters are the P & I...
Actually not. Agreed that if you are flying, it is your problem to solve right now. Later, if you are still among the living, it becomes someone else's problem.

But the causative factor is really a problem in control design that can be overcome by the control design engineers.

If you blame yourself for the problem (when you find it) and don't write it up, it won't get fixed. As long as the maintenance folks have not changed the way the aircraft flies by ill-advised maintenance, the problem belongs with the certifying authority and the guys and girls with slide rules.
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