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AF447 Thread No. 3

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AF447 Thread No. 3

Old 2nd Jun 2011, 07:59
  #1081 (permalink)  
 
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With regard to who sits in which seat it has been mentioned that the senior f/o must sit in the Lhs. In my previous company this was not the case. The acting pilot in command had to be in their trained seat. A rated pilot could sit in any seat in the cruise as long they or the other pilot was an APIC. We also were qualified for acting pilot in command if we had an ATPL and had completed our first recurrent check. Now I do not know what AFs rules are but the setup they used is not unusual and would suggest that the less experienced pilot was in the RHS and was in command.

With regard to the stall warning this troubles me that an integral part of dealing with unreliable airspeed is not actually always available. Surely this needs to have ground air logic as part of it's operating envelope.
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Old 2nd Jun 2011, 08:16
  #1082 (permalink)  
 
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Hi Right Way Up,

With regard to the stall warning this troubles me that an integral part of dealing with unreliable airspeed is not actually always available. Surely this needs to have ground air logic as part of it's operating envelope.
I agree.

Also one wouldn't confuse the stall warning vibrations felt through the control column of a conventional aircraft with anything else. Under stressful conditions, crew can miss interpret audio clues easily (like the synthetic voice intermittently saying "stall stall" or "speed speed").
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Old 2nd Jun 2011, 09:11
  #1083 (permalink)  
 
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...just some observations out of 'daily life':

@ mach-buffeting: Experiencing Mach buffeting is common in normal operations: even within the normal speed envelope some transient speed-overshoots happen and buffeting is felt, although I didn't voluntarily fly into overspeed and don't know if it becomes much more prominent if doing so. I even think buffeting is (very slightly) noticeable once your speed goes beyond 0.84, which is well within the envelope....

@ stall-warning: Part of the last recurrent training was an unreliable speed-exercise (actually embedded in a 'flight into volcanic ash'-scenario including dual engine-failure, electrical emergency etc dunno how realistic the scenario/the simulation is: what really, really bothered both of us was the stall-warning which was not possible to be cancelled, although we definitely haven't been in a stall (thinking about it, it might be a deficiency of the simulator, since if it was AOA-induced, it could not have been valid, as there was no speed on the speed-scale, it should have been rendered invalid by the system): what I wanted to say is, that the permanent yelling of 'STALL, STALL' was so distracting that it almost made us agressive... not good if you have to think 'out of the box' and take decisions in ambigous environments...

@ PNF observing PF-stick-inputs: You do have to focus your view to PF's sidestick if you want to determine what he is doing. Given a scenario (Airbus SOP!) where the PF cares about flightpath and R/T and PNF cares about systems according to ECAM or QRH (and in this situation the main workload lies with the PNF!) there is not much monitoring-capacity left....
It's those situations where I miss the flight engineer most: A guy with intimate insight regarding the systems and some distance to the actual 'haptic' flying: BTW: both prominent examples about rescued airliners where pilots had to 'invent' flying to different rules than trained (Sioux City DC-10 and Baghdad A300) had a flight engineer, but that be only an outdated rant...
In so far, the situational overview of the captain once in the cockpit observing the both F/O's from behind might even be helpful solving such a situation...
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Old 2nd Jun 2011, 10:41
  #1084 (permalink)  
 
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Originally Posted by Garrison View Post
It is unlikely that a recovery could have been made without manually trimming the THS. At high alpha the elevator is not very powerful compared with the stabilizer. That this was not done suggests that the crew were not aware of the -13 degree THS setting. Doesn't it seem unlikely that if they were aware of it, and had identified the stall, they would have been deterred from using it by their simulator training? They were about to die. Or did I overlook something in the report?
Even if it gets tiring:
Could you point me to any indication the Crew identified that they were in a stall and that it was the THS trim that defeated their vigorous Nose Down command on the elevator ???

Furthermore:
Could you point me to a source that the THS wouldn't have returned to a more neutral / Nose down setting after continuous Nose Down would have dropped the Nose below 30 AoA ?

Until 10kFt I do not see any indication that the Flight condtion was properly identified by the Crew and any corresponding Text Book Recovery attemptes were made / sustained. That makes philosophying technical limitations to recovery obsolete, IMHO.
Below 10kFt recovering from a 40 AoA would have been impossible anyway.

Regarding the usefulness of an AoA indication:
It is definitely not clear if that would have made a change. It would have bbeen an additional opportunity though. But only if it is covered in the training as well. Otherwise it will be meaningless.
Indication of the Angle of the THS: I doubt it would have helped. I cannot see a Crew already overwhelmed by Information/warnings/alerts/chimes starting to look for even more data and rather 'irrelevant' ones from their perspective for that matter.
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Old 2nd Jun 2011, 11:05
  #1085 (permalink)  
 
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HN39

As explained in the previous thread, I don't think there is significant difference between high speed or low speed Mach buffet. Perhaps the frequency changes gradually with Mach number, and that may be noticeable if there is a large spread between the high and the low limit. But since an airline pilot never gets there, would he be able to recognize the difference?
Having experienced both as FE on test/acceptance flights on the Nimrod and L1011 I can say from my experience the buffet itself wasn't much different and had we not been aware of which regime we were entering I'm sure we wouldn't have been able to tell from the buffet alone.

I imagine that AF447, by the time it was at 380 with TOGA and 16 alpha was getting a bit of both!
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Old 2nd Jun 2011, 13:01
  #1086 (permalink)  
 
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Stall warning

Originally Posted by RealQuax
what really, really bothered both of us was the stall-warning which was not possible to be cancelled, although we definitely haven't been in a stall (thinking about it, it might be a deficiency of the simulator, since if it was AOA-induced, it could not have been valid, as there was no speed on the speed-scale, it should have been rendered invalid by the system): what I wanted to say is, that the permanent yelling of 'STALL, STALL' was so distracting that it almost made us agressive...
I'm amazed. What prevented you from doing the appropriate thing and drop the nose half a degree or so?

A propos stall warning. In Interim Report #2 BEA explains that stall warning starts when the AoA exceeds approx. 10 degrees at M=0.3, and at approx. 4 degrees at M=0.8. The update now provides a third datapoint of 6 degrees at M=0,633 (extrapolated backwards from 185 kt 15 seconds later). These points relate to alphamax as shown in this graph.
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Old 2nd Jun 2011, 13:10
  #1087 (permalink)  
 
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Huttig?

BOAC above presented a report from Der Spiegel that a certain Prof. Huettig had re-created the incident in the simulator - the THS went up and stayed there - curtains. This seems to me to be the smoking gun in this crash.

Air France*Catastrophe: Victims' Families Propose Grounding All*A330s - SPIEGEL ONLINE - News - International
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Old 2nd Jun 2011, 13:52
  #1088 (permalink)  
 
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THS position AF447

QUOTE: deSitter
BOAC above presented a report from Der Spiegel that a certain Prof. Huettig had re-created the incident in the simulator - the THS went up and stayed there - curtains. This seems to me to be the smoking gun in this crash.

Air France*Catastrophe: Victims' Families Propose Grounding All*A330s - SPIEGEL ONLINE - News - International

-drl

In a previous posting I mentioned the AirCanada DC8 run away stabilizer trim causing an impossible force required by the pilots to pull effective up elevator even with their feet against the panel! This accident ended up with a big hole in the ground near the town of St Therese in Quebec, Canada.
Why should the AB 330 be any different and why would AB disqualify the
good professor Huettig's findings? There are just too many questionable things going on and we cannot rule out the industrial lobby's forces trying to influence the findings.
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Old 2nd Jun 2011, 14:08
  #1089 (permalink)  
 
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[quoteWhat IS significant, as I have said a few times (it really is crucial and we are not being told!) is what PNF said during this amazing and frightening zoom climb. Until we know that we cannot progress, I feel.

][/quote]

Might as well give up the lack of info comments - quite obvious no more info will be forthcoming for a while - unless we get lucky and have a credible leak published.

I concur with Machinbird's possible scenario re the cause of the zoom climb. Full understandable and likely.
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Old 2nd Jun 2011, 14:13
  #1090 (permalink)  
 
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Does anybody understand the rationale for two sets of control laws between Normal and Direct? It seems to make systems management take precedence over aviating.
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Old 2nd Jun 2011, 14:15
  #1091 (permalink)  
 
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Didn't the BEA permit AB to make a statement that they believe nothing needs to be modified in the A330 after the black box data was reviewed?

If that is true, BEA must believe it was a pilot only problem; right?
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Old 2nd Jun 2011, 14:55
  #1092 (permalink)  
 
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Clandestino: your gracious response much appreciated. It occurs to me that if you've been a captain, you've been teaching pilots how to fly for quite some time. Apologies if my tone was anything other than cordial.
Can anyone confirm that "l'enregistreur de parametres" as fitted to AF 330s really doesn't record ADIRU2 (or ADIRU3) IAS output?
What display are you talking about?
Good question, I should clarify.
What I was referring to (what was in my mind as I posted that) was basic flying instruments: attitude indicator (pitch and roll aka AI), airspeed/Mach, altitude, vertical speed, slip and turn (which is incorporated into the AI if I read that diagram correctly), FPV.
-His Nav display may or may not have occupied his attention.
-Engine instruments in the center display position (to his left) probably dropped out early into the event. (ISIS seems a bit far across the cockpit for his scan unless he is sure AI is not reliable).
-Other warning displays on more than one display. How did they integrate into or disrupt his scan? Unknown. (Back to the "What was PNF doing?" consideration ... )
... left and ISIS pitot unclogged at different times so there's no reason to think that right pitot was in sync with either of the two remaining.
Agreed, which is why it would be interesting to know if what he saw was what ISIS and PNF saw, in re basic flight indications I note above. (EFIS, OK, better collective descriptor than my crude depiction) matched.
However there is no mention so far that any of the four attitude references tumbled or that ALT or VSI data got invalid at any time.
Roger, unknown, and important to keep bringing up, given the number of times we have seen (including some of my own "what if the gyro tumbled?" digressions in the last threads) statements that AI was not reliable. Not valid based on what has been released so far.
Don't jump to any conclusion from that however. It will take much more than this "report" to have good idea what happened with AF447.
Indeed.

Again, thanks for the response.
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Old 2nd Jun 2011, 15:04
  #1093 (permalink)  
 
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Stall Warning

From HN39:
A propos stall warning. In Interim Report #2 BEA explains that stall warning starts when the AoA exceeds approx. 10 degrees at M=0.3, and at approx. 4 degrees at M=0.8. The update now provides a third datapoint of 6 degrees at M=0,633 (extrapolated backwards from 185 kt 15 seconds later). These points relate to alphamax as shown in this graph.
That shows neatly how Stall Warning incidence is a function of Mach Number, so when the ADRs went belly up, what happened to the M input to the stall warning system, and what did the latter think the corresponding warning incidence (AOA) should be? Does it use the last valid IAS/M value as the rudder limiter system does?

Secondly the BEA states that right at the start of the sequence :
From 2 h 10 min 05 , the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall warning sounded twice in a row.
Does anyone know why the warning sounded at this stage? It's not obvious. Could it have been an indication of moderate or worse turbulence, because, after all, this was before the dramatic and inexplicable zoom climb, and before the sustained nose up side stick inputs that caused the THS to reach 13 deg airplane nose up? The aircraft should have been in a normal cruise condition at this earlier stage. Among lots of things the BEA hasn't chosen to reveal yet, is the general level of turbulence experienced before and during the upset. For that matter they haven't said whether there were any stall warnings before it all went wrong.

Note that in the Air Caraibes blocked pitot event they also reported a 10 second stall warning about 30 secs after the AP disconnect and start of the general brouhaha. The crew decided this was false, in accordance with advice in the <<ADR CHECK PROC>>, though the ACA report notes that elsewhere the crew are told to ignore that advice and respect the stall warnings. Confused? Those issues don't seem to have been resolved, at least not in readily available documents or posts here.
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Old 2nd Jun 2011, 15:11
  #1094 (permalink)  
bearfoil
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@Graybeard

"Does anybody understand the rationale for two sets of control laws between Normal and Direct? It seems to make systems management take precedence over aviating."

GB

That basic question lit the original thread on fire for pages, and from the git go.

Firstly, I believe there are three control domains twixt N and D, if one counts Abnormal (ironic?). Just as Piloting is changing its format to reliance on automation, what gets left behind is what has become most important, Know the Airplane.

There is no challenge to the gestating supremacy of Auto Flight in allowing, (Training) airmen and women to know the personality of their a/c backwards and forwards. What is the insult to parochial aero programming inherent in aviating skills? Such Hubris. "It did exactly what it was supposed to".

I beg to differ, for if any of the doubts expressed here are proven, what remains is "I'll do this, and if it 'doesn't work', it's on you". Always the defensive, and dismissive attitude. Arrogance has always been deadly in aviation.

The lack of a fossil AH on the panel was a shorter discussion, as many were astonished to find that so 'common' an occurrence as 'Unreliable Airspeed' could (did) leave both pilots without attitude, or 'assiette' data, (display).

@gbnf

"From 2 h 10 min 05 , the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall warning sounded twice in a row."

This is reliant on the undivulged time line, for BEA state only "From....."
Anyways, after the 2:10:05 id. "Twice in a row" means to me, two short alarms, and my guess is that these were related to AoA rate transients, not a Stall per se. "chirp, chirp."

The Plane rolling right meant that a/p had been trimming out a chronic and trending condition, both Right wing heavy, and NOSE HEAVY. The THS was at 3 degrees when a/p dropped, what was the nature of the dropping Nose? Was it dropping continually, and continued to drop after a/p drop? Yes, because the THS was running behind its trim command from FMC, by definition. Nose and right wing dropping, a condition identified by both the a/p and the handed-to PF. This is suggestive not of Turbulence, but controls damage, weight issues (cg), Fuel scatter, etc. or ICE. Even an inop or over limited Rudder. Perhaps?

Last edited by bearfoil; 2nd Jun 2011 at 15:26.
 
Old 2nd Jun 2011, 15:14
  #1095 (permalink)  
 
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gonebutnotforgotten:
That shows neatly how Stall Warning incidence is a function of Mach Number, so when the ADRs went belly up, what happened to the M input to the stall warning system, and what did the latter think the corresponding warning incidence (AOA) should be? Does it use the last valid IAS/M value as the rudder limiter system does?
I looked at HN39's graph.

What you say in re stall as "a function of Mach number" seems to me "correlates to Mach number," since the stall approach, condition of stall, and warnings, (unless I misunderstand the system) are triggered by a signal from the AoA sensing system.

AoA sensing subsystem is independent of the Airspeed/Mach sensing sub system. The computer receives signals from both and uses various logic to reconcile them, which seems to be your further point, and a potential point of failure or ambiguity. (The clipping of AoA info below 60 kts has been discussed, pro and con, at some length in the Rumors Forum thread ...)

If I misunderstood your point, apologies.

bearfoil:
The lack of a fossil AH on the panel was a shorter discussion, as many were astonished to find that so 'common' an occurrence as 'Unreliable Airspeed' could (did) leave both pilots without attitude, or 'assiette' data, (display).
bear, what do you mean by a fossil Artificial Horizon? The ISIS back up display has a back up AH. As yet, no evidence that the AH's embodied in the glass cockpit displays (for basic flying instruments I note above to Clandestino) were other than functioning per spec.

I are confused at your point there.

Last edited by Lonewolf_50; 2nd Jun 2011 at 15:25.
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Old 2nd Jun 2011, 15:34
  #1096 (permalink)  
bearfoil
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LW

I'm writing with some very old notes, I may traipse back a couple years, the notes are not mine, apologies. My understanding is the pilots were without any reliable instrumentation re: AoA. If one is committed to, and experiencing stable cruise flight, attitude is critical when things go bump? Pitch is in there?

a33zab

Abnormal? I count three Law hurdles between Normal and Direct. Also the a/c can go direct/Direct with pilot input, yes? Touch the wheel, bypass A1,A2, and Ab. No one will get fired without offers of employment elsewhere, I think.
 
Old 2nd Jun 2011, 15:39
  #1097 (permalink)  
 
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Hst

I don't fully understand the discussion over the HST because (I will put it as a question) would it not have followed to a nose down posn if the PF would have gave nose down on the stick and therefore have overcome this situation?
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Old 2nd Jun 2011, 15:56
  #1098 (permalink)  
bearfoil
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I think Flight Law at the time of Stall/descent was not auto trim, and would have required manual input on the two wheels bracketing the Throttle pedestal?

(See MartinM's great pic)
 
Old 2nd Jun 2011, 16:06
  #1099 (permalink)  
 
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I know its been discussed before - and was one theory proposed by BBC/Nova - but would the speed change from M0.82 to M0.80 have been complete before the UAS? If pitot drains simultaneously block first the IAS over-reads, then if total pressure ram port blocked speed is locked in - UAS may only be detected when drain holes asymmetrically unfreeze. If this happens while in transition true air speed could have undershot target - and A/P pitch up to hold altitude? So out of trim when A/P A/T disconnect requiring immediiate manual correction?
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Old 2nd Jun 2011, 16:17
  #1100 (permalink)  
bearfoil
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The Plane rolling right meant that a/p had been trimming out a chronic and trending condition, both Right wing heavy, and NOSE HEAVY. The THS was at 3 degrees when a/p dropped, what was the nature of the dropping Nose? Was it dropping continually, and continued to drop after a/p drop? Yes, because the THS was running behind its trim command from FMC, by definition. Nose and right wing dropping, a condition identified by both the a/p and the handed-to PF. This is suggestive not of Turbulence, but controls damage, weight issues (cg), Fuel scatter, etc. or ICE. Even an inop or over limited Rudder. Perhaps?
 

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