infrequentflyer789

Thanks for your response. Help me to understand how "relieving the elevators" does not acquire a massive amount of PITCH Authority in one or the other direction? The HS is acting as a lever to "neutralize" the effort required to deflect the elevators, ever producing more baseline AOI. Angle of Incidence in this sense is an artificial "neutrality". The FCOM alerts the operator to the THS preventing some PITCH authority above 180 knots? How is this alert benign to the efforts of PF447 recovering the a/c?

Yes, I think elevators alone would have been preferred. Once above a certain angle, and at >180 knots, with All Trim Fuel aft, recovering seems a tall challenge? In this sense, the elevators are "Trim Tabs", ineffectual at "boosting" the control surface (THS), to allow maneuvering. Instead, they have a range of effect that traps the a/c in fluctuating PITCH excursions. Neither direction is satisfying, to the extent that AoA is "never below" 30 degrees (BEA).

Not even Flare should top 17 degrees, yet here the a/c is at "cruise" and 16 degrees! Do we set out to castigate the pilot ("Je ne comprends rien").
Do we attack the machine? Why do either? The a/c in some way got away from her pilot. Some random misfortune is trying to tell us something. To the extent we make up our minds, we lose the opportunity to learn.

As an aside, you say "Elevators alone were sufficient to get her to 16 degrees and fully STALLED." In ALTERNATE LAW, isn't the airframe protected from such a thing?

Static Port Placement
 

grity: Interesting graph, Grity; thanks.

I should have explained that my surprise was not at the fore-aft placement of the static ports on the A330, but their placement so low on the fuselage, maybe only 30-40 degrees off vertical centerline.

By comparison, the DC-10 static ports are at least 60 degrees off the vertical. FWIW, they are also about 47 feet aft of the nose, beneath the mid-cabin doors. The low speed static correction is less than the 300 feet of the A330; more like 240 feet, IIRC.

Also noteworthy is the lack of an airspeed input to the Stall Warning on the DC-10. It is based on AOA sensor, modified by flap discretes.

CJ;
FWIW, I agree CJ - it is a mistake to read too much into each word in an attempt to squeeze this or that interpretation, (ours!), from it. Finding agreement when far more is known is going to be equally difficult as well.


Interesting post and link Machinbird, thank you. I don't disagree that a form of cognitive overload may have occurred. In keeping with this discussion, I would like to broach a human factors aspect about which thus far nothing has been noted or asked. The observation concerns SOPs, CRM and cockpit discipline in the handling of this event.

The creation, implementation, training and checking of SOPs, CRM processes and their outcomes, cockpit discipline, are intended to avoid or delay cognitive overload, or cognitive dissonance.

While cockpit design, cockpit displays, ergonomics, and aircraft/system drill and checklist design will influence outcomes, a "Standard" way of accomplishing complex tasks under both time and operational pressures reduces the potential for error. I know very well that it doesn't always work that way despite best efforts.

I would like to preface this observation by stating that this is not just about "the crew", but it is a question which will arise in every airline pilot's mind because SOPs, CRM and cockpit discipline are heavily emphasized in recurrent training and line checking.

This is not about finding blame because that is not what the investigative process is about. The investigative process is about "finding things out" and must be free to ask all questions regardless of how uncomfortable they may be. In other words, the investigative process is unlike ordinary discussion in that when a question is asked, it does not imply anything other than a need to know.

So asking a question about training does not imply that "training is under suspicion" nor does asking questions about the crew's actions imply that such are under "special scrutiny".

I would like that distinction to be as clear as possible. This has nothing to do with complementing or criticizing the crew. The notions of "defending the crew" or "criticizing the crew" don't apply in the investigative discourse. Criticizing or defending the aircraft may have a place in other venues and so may such an examination of the crew have a place, but that would be a legal, political, economic discourse, not the investigative discourse.

I make this distinction partly for the reason CJ posted his comments on parsing language - the same words will mean different things, depending upon the discourse. "Investigate" means different things in politics and law than it does in safety work.

That said...

The question of SOPs and standard responses to abnormalities arises out of the almost-immediate response just after 02:10:05 by the PF to the autopilot and autothrust disconnect and the ECAM messages. We know that the BEA Update states that almost immediately there was a left and nose-up SS input and pitch increased beyond 10 degrees.

Abnormal and Emergency SOPs are created and trained to:

a) ensure control of the aircraft is firmly in hand and that stable flight was being maintained and to ensure the flight path (track and altitude) was being maintained as needed;

b) ensure that all crew members on deck were alerted to the problem, and to who was in control of the aircraft and who was to execute drills and/or checklists - ATC would be notified when there was time;

c) ensure that all crew actions are predictable and understood by all cockpit crew members and to avoid "individual variations" leading to unexpected responses and confusion.

This is the standard Aviate, Navigate, Communicate rule that we have seen mentioned.

In terms of CRM and responding to abnormals and emergencies, no action, no drills, no checklists are started until the aircraft is under control and stable.

Most of the time that is a quick assessment and emergency drills are done without delay. For an abnormal such as this one, there is no hurry. The airplane was stable before the event and other than minor variations perhaps due to turbulence, would continue that way in the absence of input.

The pilot flying always initiates a drill or checklist by announcing the drill being executed or the requesting the appropriate checklist. This communication alerts everyone in the cockpit (usually just the two), to what is coming next and to prepare for response, as trained.

If a memorized drill (such as the Rapid Depressurization, Emergency Descent), the PNF monitors the drill for accuracy and correctness while the PF flies the manoeuver and where necessary calls out any deviations. If required (in a EGPWS manoeuvre for example or Stall Recovery), the PNF may call out primary parameters such as pitch, altitude, speed, rate of climb and so on. Here, such feedback would be of critical importance to help avoid "tunnel vision" and increase situational awareness for both crew members, and to help the PF who would be concentrating on flying the aircraft with a possibly-reduced scan.

As I have said, this wasn't an emergency such as a depressurization, an engine failure or fire or a GPWS event which requires timely, immediate action but it did have two memory components to the drill, (as shown in the BEA Interim Report #1), before the UAS QRH Checklist was to be called for. I have discussed this memorized drill and checklist a number of times on previous threads.

The next step in the SOPs for handling an abnormal is to execute and clear the ECAM messages. There are SOPs for this process. Once clearing all the ECAM messages is accomplished, the STATUS page is checked for equipment and capability lost. The ECAM is then cleared. Then, if still necessary, the "paper" checklist, (QRH) is called for by the PF and brought out by the PNF and referenced. Usually the QRH checklist most commonly used are the Landing Config/Approach Spd/Landing Distance Following Failures and Landing Distance Without Autobrake CONF 3 or CONFIG FULL checklists. These kinds of items might be delayed until closer to destination - I'm just using this as one example.

When all ECAM actions and Status reviews are complete and when the required QRH checklists are completed and when the aircraft is considered secured the process of communicating to ATC any problems with capability in terms of maintaining flight and navigation, then communicating with the Flight Attendants, then, where necessary, the company. Any diversions, changes in altitudes are considered at this time.

This is one example of how it's done and there will be variatons, slightly different priorities and more or less memorization of drills depending upon the airline.

The key point here is, this process must be thoroughly trained and checked during recurrent simulator and line checks. SOPs, CRM and cockpit discipline are for those times when things start come unglued in a hurry. The training focuses one and gives a structure to the inevitable initial chaos which can unfold rapidly as we have seen here; - at 02:08 they were talking about deviating to the left of course, and just over six minutes later they were gone.

The question of SOPs goes beyond the crew and must be asked "upstream" of just this crew. What support for these areas was there and how robustly was it carried out?

A more complete update from the BEA will hopefully shed some light on this aspect of this accident because it may be related to the reason for the pitch-up and stall.

The "Airbus Golden Rules" came out a very long time ago - around 1998 IIRC. The later 2004 document discusses the above process in greater detail and is well worth examining.

Hi Bear,

See you are back and posting once again. There was a very interesting post awhile back on the other AF447 thread in R&N. Take a look at it, would like your thoughts. You can find it at: Post #1222, Pg.62 by The Shadow.

I would sure like to know what was happening in the two minutes or so before AP/AT disconnect. If the pitots were beginning to clog, what was the autos doing to adjust for sensing slower speed that really wasn't slower.

Hi TD!

I've read the shadow, and more than once. As to a gradual packing up of the Pitots (and three apace), the a/c would trim ND/NU with ThrottleUp and/or THS/N/U/D. This would satisfy the computer, and completely bollox up the actuals. At some stage, and not necessarily due ICE, the a/p would quit (cannot hold 'Altitude'), or for any of a number of easily understood reasons. If so, and prior to "Disagree", the a/c may simply handover the goods and continue in NORMAL LAW. If agreement then degraded to the extent of AD needing "Timeouts", there is a separate kettle of fish, eh? That is UAS, certainly, but as a follow on, not as a priori. I am not sure if this mode is represented in the prior incidents of UAS, but I also do not know if our crew had experienced an actual UAS of the garden variety either.

I am amazed that so distinguished a group as this one hasn't thought the PF was indeed acting on bad data (not his "fault"), and was doomed to a guessing game either way, No?

nice to meet up again, my friend.


Can we call this mode: "Triply redundant bogus airspeed, but who knew?"

TRBA/bwk........

bearfoil;
Where is the guessing game here? It was an airspeed indication failure. Engine thrust including all engine indications, the altitude indication, the IVSI, the aircraft attitude indicator and the ship's GPS (for groundspeed and actual altitude) were all functioning and available, and the use of these indications is guided by the UAS memorized drill and checklist. There was no need to do anything but wait.

There is no guessing game which is probably the reason that it hasn't been brought up for serious discussion. It can be brought up I suppose but where is the evidence and what is the defence for the notion that this was a guessing game?

"Je ne comprends riens." From a pilot flying a wide body with 280 souls on Board. "No valid indications". "We have no indications".

Absent anything of value to rely on, my 'guess' is that "guessing game" is a kind sort of way to describe epic fail.

"There was no need to do anything but wait". The Pilot flying thought differently, and acted accordingly. You have evidence to prove he was mistaken?

If The Shadow is correct, and he makes a compelling case, the a/c was guessing too. Acting on bogus data might be a fair way to frame it. It passed along its blunder to the flightcrew.

Hi Bearfoil,
In fact, the FCOM is underlining that the aircraft "PITCH authorithy" is better than in "conventional aircraft". What is mentioned is about a very remote case: a fully "jammed" THS - without any manual or electrical trim available. Above 8 deg NU, elevators will still be effective below 180 knots: this is the limit speed mentioned for safe flying in this case.
But now, do you think that AF447 had a jammed THS? Should I remember you that autotrim and manual trim were both very likely available. In fact, it seems that the main flight-control issue about AF447 "recovery" attempt, so far, was rather the complete lack of PF sustained nose down imputs...

By itself, "All Trim Fuel aft" means nothing... there is a variation from 0 to +0.5% aft of the target CG due to central tank fuel use which is completed by transfer from the THS to the central tank during cruise; add also a 2% safe margin below certification aft limits (if target is at max) and a push-button for forward fuel transfer, just in case.
Recovering from a stall without sustained nose down imputs seems rather quite more challenging than any "all trim fuel aft".

bon soir, takata.

"Better" Pitch authority than conventional a/c? Describe Better? More powerful (Stubborn)? More "Travel" (~14 degrees)? Impossible to recover at certain speed and exaggerated deflection? Jammed or not, The THS is a formidable force. Pitch Authority is more complicated than mere power, though admittedly Airbus has that ground covered. How quickly is it available? If it transits to its NU limit, are elevators enough to recover from some unusual attitudes? I think the answer is patently NO.

Without assigning a responsible, the THS can prevent a predictable planform. yes?

I think there is a working theory that has fossilised into a narrow ledge for some.

I doubt seriously the pilots will be found to have handled this a/c correctly at every turn. Likewise, the a/c itself became a riddle....... "Je ne comprends riens"............

Airbus once again must confront: What is it doing? It seems the THS happily wormed its way to near Full NU, and remained there. Likewise, the a/c climbed careeringly to STALL.

Regardless the upshot of the piloting, A330 has a legacy of explanation of its own, imo.

Absent anything of value to say/add in your many posts, you'll better refrain from bolding quotes out of your FANTASY LAW universe.
"Je ne comprends rien" is not part of the tanscript, neither in French or English. (Beside, you dramatically added 52 "souls" on board).
Here is the good quote from the note in English.
And some part of your answer (about what indication was lacking) is certainly to be find in the following sentences:
So, fifteen seconds before this point, the speeds were invalid (AoA was above 40° and the PF was applying full back stick for 30 seconds)... then, maybe no speed at all were displayed on either PFD, nor Stand-by gauge...

I took a break. Several things are obvious upon reading to catch up. So I've caught up and herewith deliver this word bomb.

Nothing's changed, at least through the morning of the 6th.

(wordy annecdote)
There seems to be a lot of oversimplification in fields I work or have worked. For example, in some systems you cannot use "voting" type redundancy. The GPS satellite FSDU, Frequency Synthesizer and Distribution Unit, that takes the Rb and Cs clock 10.23MHz signals and applies carefully modifications before distributing the system clock to the two independant clock busses on the bird. There was a passive frequency distribution network from the clocks to the frequency synthesizer inputs. It combined all clock outputs into the three synthesizers' inputs. Since a 10.23 MHz sinewave is not something you can vote about only one clock and one synthesizer is powered at a time. (Otherwise you would get unacceptable spurious signals even with very high quality electronic relays to select clock signals.) I had to design for about 120dB isolation hoping to get at least 100dB. That's a 1 trillion to one isolation ratio as the target and 10 billion to one as a target. Trust me, clocks and synthesizers not needed were turned off. The outputs were all in parallel with a circuit designed to not short out the output bus if a transistor failed short circuit or open circuit. So that was, in essence, a passive voting system. The powered synthesizer drove the bus. With two busses a failure on one bus let the other survive and take over the full job. (/wordy)

PJ2 likes the first step of the UAS scenario concept. It fits very well when you consider it's claiming coincidence for all three pitots to fail the same way at the same time. If the PF side, which we do not see, showed even a brief overspeed just as the aircraft disconnected that would be the last thing the PF saw and he might have over trusted it. The off-again-on-again-finnigan stall alerts certainly could foster the view that they were spurious when overspeed actions fix what stall actions seem to bring back.

bearfoil wants and "easy" switch. It appears AirBus has patented such an idea. Way back in the June 2009 "era" of this discussion the idea of using the INS and GPS as a backup to the pitot tubes was broached. It was denied. Everyone figured long term, for which it cannot work. For short term, say a couple minutes, it should work just fine as an extrapolation tool. ABI seems to be planning to use this or is using it, likely on the A380. That's as "easy" as it gets. Warn the pilots to be on their toes and more attentive than usual. But fly through the mess, AoA, Thust, and GPS/INS. If at least one of the pitot tube readings does not become "sane" within 2 or 3 minutes or of altitude hold is too difficult then let the pilot ease into control. He's had a couple minutes to become well aware of what has been going on.

(By the way, the "easy switch" is the path towards a fully robotic plane, you know.)

BOAC seems to still desipise the glass cockpit and FBW. Right or wrong it is not going to go away no matter how much he rails about it. On a per million miles basis the glass cockpit in the A330 line shows half the accident rate and hull loss rate of the Boeing competitor he loves so much. Those are VERY loud words in mute bare statistics. I'd have more sympathy for him if the statistics were reversed. I suspect he will see a two person "executive" cockpit before he sees a return to cables or direct control. (The executive makes executive decisions about where the plane goes, never "files it", and is there rather than on the end of a long string of satellite relays away from Nevada. The other person is the relief executive. Both are trained with three special skills, giving the executive direction to the aircraft if something odd happens, telling the world about these changes, and reading the radars. He might even be trained to push a button to switch from one set of computers to another if something extraordinary were to happen.) It seems to me that is the direction it is all moving. And when the electonics can handle a hole blown in a plane with the plane still marginally flyable it will happen. "Get over it."

Confiture is remarking about the pilots seeming unawareness of what each was doing. If the quiet cockpit the BEA release conjures as a vision is real, at least one new feature must be trained into pilots: thinking out loud. Announce what you see and what you are doing about it. And acknowledge what the other has said. If that oddball scenario I mentioned above with PF seeing something quite different from PNF and recorded left seat only data then such an announcement of observation and intended action could have saved the plane.

PJ2 reposted (this time), for the Nth time, the schematic of where the various sensor signals go. I guess after RR_NDB's comments about redundancy it's time to wonder what makes the pitots redundant with only one going to any given ADIRU? I hope somebody did the numbers and decided this was better than feeding all three to all three ADIRUs. Or else there are data feeds between ADIRUs that are not shown. Anyway, I'll run an idea up a flagpole. Display all three to give speed with an error band with special displays for lost channels. Then there would be no chance PF would see something different from PNF. (I'd add a fourth channel to the picture, the consolidated GPS/INS report corrected for the last known calculated air speed.)

And we have the bozos who setup the cirriculum for AB330 pilots teaching them to keep their grubby paws off the trim wheels at all times and the designers who told the software people to never resume autotrim once the pilots mess with the trim wheels. Oy vey!

Detail regarding Captain seeing over shoulders of the PF and PNF: Note that he was found floating. The others were found belted in. He was probably standing observing closely.

As a hint for people who have a new thought it would be smart to revisit the BEA release and work it into the last 6 minutes and 21 seconds of the plane's flight. Ask, "How does this fit?" It might prevent your looking like a bonehead. (bearfoil continues his attempts at this proof.)

bearfoil, "Certification is mainly a mystery to me; I trust the system to certify a/c to be safe and reliable."
Sir, there is no such thing if you mean "never fails". The only way to achive "never fails" is to "never try." Stay on the ground and never fly. Then something other than an airplane will kill you.

Certainly not intentionally from me, bf. That is why I concentrate so hard on why they performed the damnfool stunt looking in training for the answer.

It's clear "what" killed the plane and the people aboard it. What is not at all clear is "why?"

Mr. O and bf mentioned "protections". They are NOT protections. They are limits. Calling then protections gives a false sense of security. I sense this all through this discussion, by the way. There is too much, "It can't fail." Can't is a very very big short contracted pair of words.

I remember asking WAY WAY WAY back in the June 4 2009 thread about some of this. If there is a standard drill for handling a plane in an unusual condition why does the plane not do it itself rather than expect the under informed (for instance no AoA) humans to take the load? There should be a better way.

Please forgive me here if I "bitch" about this a littlte. You have a TEAM in the cockpit. They are not telepathic. As you aviate tell your partner what and why. Think out loud, as I said above.

Do you read more than you post or do you post more than you read? (As it happens I rementioned this above.)

Quoth ChristianJ, "Personally just looking forward to the next BEA report... and the way that will put the fox among the chickens, once again."

Amen.

For those interested, The Shadow's post is on pg 61, #1218 R&N thread. We have discussed similar issues on the Tech Log threads, although not in such a concentrated manner.
It is pretty obvious that no one on the AF447 flight deck saw the trim indication in time. If they had, there should have been an understanding of what the problem was.

JD-EE

Thanks for the gentle treatment, ma'am. Guilty. I think you referred to BUSS (BackUpSpeedSystem), not fitted to 447. I do not advocate a robot of any description, it is (will always be), a potential lethal comeuppance for the Hubris of those who have more education than brains.

Machinbird. If that alone is the upshot of this tragic accident, everyone on several continents who had a hand in 447's demise deserves a flogging.

(ie: Not "noticing" Trim). For the record, may I opine that calling that THS a Trim device is abundantly fantastic? Like comparing a haircut to a decapitation.

The following graphic is a compilation of work done by HazelNuts39 and updated to include modifications suggested by A33Zab. It covers a period of 2 minutes from just prior to AP/ATHR disconnect to about one minute after the aircraft actually stalled.

http://oi51.tinypic.com/dbr05u.jpg

The time the stall actually occurred is shown as 2:10:59 and observation will show that the aircraft gained a small amount of height by ballistic momentum over the next 6 seconds.

I'm sure that HN39 will assist with explanations should they arise.

The graphic above is 785 x 500 pixels so as not to stretch the page when being viewed on displays of 1024 pixels horizontal resolution. Clicking on the graphic will link to a full size image (1100 x 700) displayed in a separate window.

Hi Machinbird,
I've read it and, quite frankly, it is full of obvious misunderstanding of the very basic systems. Hence, beside very plausible description of some likely crew reactions, the theory developped is completely confusing with such a mix about flight control laws including their related sub-systems monitoring.

I wonder how he may think that the initial PF pitch-up described by the BEA was certainly commanded by the "flight system" and was not due to any manual side stick imput?
If the flight system needs to move a control surface, if possible within the current flight law, it will do it directly without making some side-stick imputs! But if the recorded side-stick channel is showing an imput, this is evidently a PF action... Why would one have a single doubt about that?

Hence, what such post is mostly showing, is that many people simply do not understand the basic logic behind the flight controls but still are furiously patching up some theories that will contradict most of the investigators work... (see Bearfoil's sustained daily efforts to continuously stall this thread into the deep-deep!)

What would be the problem with the trim, beside the initial roll tendency after AP disconnection?

JD-EE, we were temporarily lead astray by forum members who apparently believed that autotrim would not resume control once you made a manual trim input. PJ-2 has kindly set us straight (with technical references) and explained that autotrim will resume once you take your paws off the trim wheel. I strongly suspect there is some misinformation adrift in the Airbus community that needs correction. I wonder how BEA will address that?

mayby the different positions of the static ports also generate a different sensibility in case of icing.....

dolphins have their sensors at the forehead under the blowhole!
http://onderwijs1.amc.nl/medfysica/d...s/image004.jpg

Takata,
The problem with the trim is that it moved to a high aircraft nose up setting without crew awareness.
It appears that a FBW aircraft requires the pilot to know exactly what mode the aircraft is operating in or else the question arises, "What's it doing now?" In the case of the AF447 crew, they had no attention to spare to consider what the trim might be doing, thus the nose up demands caused the trim to run silently to a high setting without the knowledge or anticipation of the crew.

Once at a high setting, the trim acted to stabilize the aircraft in the deep stall that they eventually achieved. When the Captain arrived on the flight deck, he had to puzzle out what he was seeing. From the jump seat, the indications were essentially hidden by the wheels themselves.

The THS autotrim system has virtually eliminated the problem of trim-runaway, but it has replaced that problem with a new set of problems.

With regard to The Shadow's post, I merely pointed to its location. It was a pretty good post considering the date of posting and the breadth of coverage, particularly the human factors. I did not agree with all his points however.

Hi,

JD_EE
Another Pprune scoop ...
Better than Le Figaro there ...
JD_EE .. you also been a "person close to the investigation" .. a "reliable source" ?
Can you show your reliable source confirming the text in bold ?

- I'm afraid, that like many other inputs from many 'experts' on this huge sequence of threads, that is a complete mis-representation. If you read the other thread (Safety forum) you will discover that it is the attitude to the implementation of "the glass cockpit and FBW" and its interface with the pink and fleshy bits that operate it that I "despise" - if that is your chosen approach.

Even PJ's 'Golden Rules' from Airbus (how concerning is it that this needed to be published? Where have we 'arrived'?) make no mention I could find of 'Direct Law' handling, merely 'manual flight' - ie 'protected'. It makes no mention of that fact that the 'protection' we 'sell you' with the aeroplane may not. The mindset that needs to be broken is that all this is going to 'look after you'. It will until it doesn't. That, if anything. must be the key message. BA tried hard a few years back (following a worrying spate of loss of 'SA' and common-sense induced by the mesmerising glass) with a far-seeing course for pilots called 'EOI' - 'Enhancing Operational Integrity'.

One further comment - I am concerned that these 'graphs' produced after hours of hard work by folk like MM and A33 will pass rapidly into the 'factual' world - as pseudo FDR traces - when in fact they are supposition - guess-work - based on extremely limited information. We just do not know enough at this time.

I'm no expert but I've been trying to follow the AF447 tech thread with the aid of the Flight Crew Operating Manual here..

http://www.mercadodaaviacao.com.br/a...t_controls.pdf

In the section on Alternate Law it says..

Quote:
Won't going to Direct Law remove the nose down demand that it just tried to apply? It says in Direct Law all protections are inoperative.

Have I missunderstood?

Any pilot flying an aircraft with autotrim should know that his trim will follow his stick imputs, shouldn't he?
Isn't it one of the basic skill needed for one wanting to be rated for a specific type? What makes you think that many FBW pilots don't know exactly in what mode their aircraft is operating?
Well, considering that the trim was doing what a type rated PF asked, and what it is always supposed to do in such a case, what would be the point to consider that it would take more "attention" than usually?
Hence, as usual when imputs ask for a lot of nose up, what is wrong with that?
What make you believe that a type rated crew would not anticipate it or lacked the knowledge that it will do exactly that? Do you think that it wasn't what they wanted, nose up?
Right, the PF achieved a full stall with the help of the side stick, thrust and THS trim. Hence, what's wrong with the side stick, the thrust lever and the THS trim?
Beside hindsight, what makes you believe that the Captain would have immediately recovered the situation with all the trim settings displayed under his nose? He wasn't there from the begining of the crisis and still possibly far behind the other pilots. He also might have seen the Flight Control page, where the THS trim setting is displayed, right in front of him...
I still can see the problem with the THS trim. If they had acknowlegded their stalled situation in time, they would have immediately applied full and sustained nose down imputs, hence, THS trim would very likely follow that. If, for whatever reason, THS trim would not follow those imputs, not enough elvators authority should have attracted PF attention about considering that trimming nose down could help him... at least, theoretically if his training level wasn't the issue.

Hi BOAC,
I tend to agree with you. If you keep taking tactile feed back away from a pilot, then you reduce him/her to a visual clues only input processor. If the FBW computers couldn't cope without valid airspeed information, is it a bit too much to expect a human to do a better job without the benefit of a "conventional aircraft's elevator feel"?

Hi,

takata whrote
So .. when read all this .. my feeling is:
The pilots were rated on type ... but nevertheless were not qualified for the situation of AF447 was
They had not knowledge of basic flying skills
They don't know how the Airbus systems work
So we can conclude that:
The formation and training of those pilots is very low
So Air France bear all the responsibility for this accident by not providing adequate training to their pilots or not detecting by exams (simulator) that those pilots were not qualified for fly a Airbus A330
At least and even if this above is not entirely true .. Air France stay bear the responsibility of this accident as the contract between Air France and their passengers was to transport them from A to B and they failed....
Are my feelings good ?

Machinbird re trim wheels - thank you for clarifying that. I must have missed that even though I make a point of reading PJ2's postings extra carefully. Alzheimers must be setting in.

jcjeant, the PF and PNF were brought up belted to their seats according to BEA press releases.

The releases declared:
* They pulled up two bodies.
* They pulled up the two pilots seats.
* They DNA identified the pilots.

Ergo, if the two bodies were not in the seats or very near them, who was and why were they dumped from the seats? (And if they were not in the seats I wonder how they came out considering how they are strapped in. It's not a passenger style seat belt. The pilots use full harnesses.)

BOAC, on the graphs I am in agreement with you. And I believe we are in agreement with gums about the word "protections." The word sets up the wrong mindset leading to people getting reckless and cavalier about deadly serious subjects.

Re FBW - you could have (and did) fool me. You seem dead set against AirBus despite its superior safety record. And as far as I know for transport aircraft though the A340 that AirBus has embraced the automation more than other airlines. So I drew the conclusion you rather disliked FBW and software anywhere on the plane, except perhaps in the inoperative laptops the SLF carried on board. You have been busy ripping software engineers a new set of orifices it seems.

- not quite sure w t f that means but it sounds like something my mum would not like me to do. I suspect we move in different social circles.

I see you have not contributed to my thread at all so I suspect the Alzheimers has prevented you from reading the opening post too, or maybe you forgot you read it?

This video on the loss of the X31 back in the nineties - it was suggested a disconnected probe (and ice) was the fault!

It too went straight up!!

I am not aware of anything like it ... ?
Anywhere below 10000 feet but rarely at cruise level.


Takata, if you are asked to fully stall your aircraft for exercice, would you still trim up past the early signal of the approaching stall ?
Why automation has been doing something you would not ever do yourself ?
IF ... the pilots were confused enough to maitain NU inputs, was it necessary for the automation to help them in their confusion ?
Leave on their shoulders that kind of initiative.


PJ2, I am unconfortable with your view here.
You have not adressed my concerns.


You are WAY out DW, and should know better ...

TE plots
 

mm43;

Thanks for your superb graphics work enhancing the crude EXCEL graphs I posted here, and for posting your graph on this thread.

Of course you are quite right. My 'pseudo FDR traces' are to some extent 'supposition - guesswork', but I don't understand your concern. I thought that, while we're waiting for the publication of the real FDR traces and many posters discuss AoA's, pitch angles, airspeeds etc., this was better than nothing.

Perhaps it would help to explain in some detail how the data shown on these graphs have been derived. In this 'computer simulation' (an EXCEL spreadsheet) the airplane manoeuvre is driven entirely by an assumed variation of acceleration (az/g) along the earth vertical that is shown here. At first, that driver function is just a wild guess. But then the resulting v/s, altitude, airspeeds, AoA, etc., is compared to the data in the BEA Update, including the time line, and the input function is 'massaged' to improve the goodness of fit, and the same process is repeated. After a large number of iterations I felt that 'version 4' is as good as it will ever get until we get the real data.

The calculated parameters are derived from the 'driver' function az/g by strict application of flight mechanics (i.e. Newton's laws) and A330 aero data published by Airbus (where available(*)). (**). The calculation then goes as follows: V/S is calculated from (by integration of) az/g. Altitude is then calculated similarly from V/S. Subtracting altitude from total energy yields kinetic energy and hence TAS, CAS and Mach. V/S and TAS together yield FPA. Next lift coefficient CL is calculated from weight, normal load factor n, Mach and altitude. CL and Mach yield AoA from the aerodynamic data (*). Finally, pitch angle is calculated as the sum of AoA and FPA.

For what it's worth, until we get the real FDR traces ...

(*) The available data cover the operating envelope between Mmo and buffet boundary. There are no data close to the stall and beyond. For these conditions I have assumed a pitch angle of between 15 - 16 degrees and calculated AoA from Pitch-FPA. Whenever I quote a stall-AoA, it is based on what I think is a reasonable extrapolation of the available data.

(**) This means that, if the airplane is subject to the assumed az/g, then it must follow the derived data shown on these graphs. In other words, the data shown are mutually consistent.

You are correct Chris, but you still need favorable conditions :

• P3 not in the usual aft position
• Tray table stowed
• Adequate luminosity

http://i45.servimg.com/u/f45/11/75/17/84/af447_12.png

http://i45.servimg.com/u/f45/11/75/17/84/af447_13.png

What I'd like to emphasize on is the following :
IMO, fully visible control columns are a natural and easy Gold mine of valuable information. That free information is lost with the sidestick philosophy as implemented by Airbus.

People here pretend that one sidestick was maintained full NU for 30 seconds ... Were the PM and Captain aware of that situation ?
Never with fully visible control columns, such critical information could have been missed.


As stated by Chris Scott and PJ2, I can confirm that it is possible to get that information from P3, and so without P1 or P2 concourse :

http://i45.servimg.com/u/f45/11/75/17/84/af447_14.png

http://i45.servimg.com/u/f45/11/75/17/84/af447_10.jpg

http://i45.servimg.com/u/f45/11/75/17/84/af447_15.png

[quote+HN]but I don't understand your concern.[/quote] - I obviously did not express my 'concerns' simply enough. I have no issue with the hours of work folk have done on these images and they are 'interesting'. My concern is that they will inevitably become 'fact' and we will be again be plastered in posts similar to those resulting from the Meteosat images '"See - they flew straight in to a big red thunderstorm"etc etc. As long as everyone remembers that these 'graphs' are NOT from the FDR we will be ok.

However, it won't be long before we see- "since they had xxxx at 02:xx:xx (from the FDR trace) then surely yyy"

mmciau - interesting clip I had not seen before - secondary cause of accident - ?
"pilot ignorance of an option to override computer control". No, I mustn't.

@ Machinbird,

Thanks for the post and page correction on The Shadow's post. I guess a couple of posts were removed after I made a note of it, leading to my error.

Hi BOAC,

I just wish AB had fitted such a switch.

+1

1) how on earth can a "system" allow the THS to go to full 13° up in cruise at 35.000' ?

2) how on earth can a stall warning be disabaled below 60 Kts to just kick in again when control is being regained (and completely confuse the poor crew) ?

A couple of comments that call for a rejoinder.
Crew awareness of nose attitude begins, in instrument conditions, with the artificial horizon/attitude indicator. If that was working as advertised (no data to date suggests it was not) then the primay scan instrument should have given PF and PNF (and later Captain) indications of where the nose was relative to "level flight." Instrument Flying 101.
True of most modern aircraft (to include modern helicopters that aren't FBW, but do have a lot of redundant and overlapping flight control systems and related degraded modes)
Example is the SH-60 Seahawk:
From all things (and A/P such as it is) on (AFCS on) you go to AFCS off, then Trim Off, then SAS off (SAS 1 and / or SAS 2) then Boost off. You are still flying, but in each case you can do some things, and can't do others. The aircraft also gets a bit more "touchy" to handle, and pilot workload goes up. The last puzzle piece (which means you are having a very bad day) would be if your Boost was off and you then got a horizontal stab miscompare, which forces you into manual control of the stab. When working in fully functional mode, it is that aircraft's sole FBW control surface.
Graceful degradation? I guess so.

The Control Laws of A330 may or may not be as graceful in degradation, but the aircraft itself is a bit more complex, not the least due to the requirement to manage fuel and CG via various fuel transfer protocols.
Also there are more A/P functions and, more FBW involved. I have once again walked my way through the degraded modes. They make sense.

I guess that they make sense to A330 pilots, particularly if you get to practice them in suitable training environment. Nothing like some practice and a few "hell sessions" in a sim to get you to know your systems. :cool:

Regardless of which bird you fly, you really have to know your systems.

The more systems, and the more they interact, the more you have to know. Enter your company, and the manufacturer, and their training material, and the training programs.

Those last are critical elements in how well any crew understands their aircraft.
Crew awareness of nose attitude begins, in instrument conditions, with the artificial horizon/attitude indicator. If that was working as advertised (no data to date suggests it was not) then the primay scan instrument should have given PF and PNF (and later Captain) indications of where the nose was. Instrument Flying 101.

jcjeant:
All? Outside of the cockpit, there are three non trivial and overlapping bodies who influence how well prepared a crew is for their missions.
The airline
The aircraft manufacturer
Regulating bodies

The rule sets and information each of these bodies issues to guide, restrict, limit or otherwise influence expected pilot behavior is subject to omission or error. AF has a share of responsibility, but for you to say "all" is an overstatement.
I suppose that from a "strict liability" point of view, that's one way to look at the accident: breach of contract to carry from point A to point B.

Looking at it that way doesn't get one any closer to addressing the sysetmic issues that are under the conginzance of

The airline
The aircraft manufacturer
Regulating bodies

Therein lies the remedy to avoiding such a mishap in the future.

TD good morning,

More than shifting the (at the time) fascination with sea bottom debris arrangement to AD disagree precursors, Shadow's post is illuminating. Airdata that became discrepant is assumed to be the cause of the accident, how did it come about? He introduces the concept that this phenomenon may have an actual beginning, and it may not be the "So, we have lost the Speeds"...

It has been addressed before, but not to the extent that people may include it in their concept of the progression of failures that brought 447 down. The direct cause of ICE in Pitots is considered to be microcrystalline particles. If in the area of some well distributed solid particles, it is reasonable to conclude the tubes may ingest these at some conforming rate. The Three tubes were "identical" in nature, differing perhaps in the degree of corrosion the drain holes had experienced in service. Dependent on the concentration and rate of uptake, it is logical to assume the Air Pressure differential migrated lower over time, indicating an airspeed that was progressively lower than actual value.

As the speeds declined, the ship would accommodate the "loss" of speed by increasing power, since energy needs to be added and altitude needs to remain the same, but as the a/c climbed anyway, (the energy was actually just right, the computer found it to be low because of ICE), the Nose would be lowered. This might continue until the a/c was zipping along at its assigned cruise level carrying too much power and actual velocity. Depending again on the rate of uptake, this false trimming would last until the a/c autopilot checked out, unable to control the Nose "hunting for a satisfactory Pitch". (AutoPhugoid?)

That is merely a hypothesis, BEA have not addressed through their data any such thing. Neither have they favored ICE as the reason for UAS, to my knowledge.

Autotrim. Takata is correct, of course. Except for one thing. The THS is a very large surface and can control Pitch without as much steady pressure as required by elevators alone. For this, the a/c pays a price in Response.
The Horizontal surface is powerful because it is large. Large things move more slowly than smaller things. To think that it is desirable that when a pilot needs response, he is awarded Power instead, and that lagging the possible cycles of deflection necessary, misses the point. By the time TRIM has "helped" it is not needed, and it becomes a handicap in the ability to maneuver. (AutoPhugoid?) At a/p loss, was it dropped because the Pitch oscillations were too great? Did the PF "chase" the THS all the way up to STALL, trying to get the nose down while still in the aft area of the BackStick? Unable to see THS deflection, would he be able to sense the lack of ND he wanted, thinking that at "neutral" stick, it was no such thing, just a steady increase NU? Who wants to chase TRIM all the way up to ballistic? Bottom line. Why Autotrim in dire circumstances. Obviously available, even mandatory, who needs it?

Needless to say, given the size of the THS, quick movement puts large mechanical demands on the surface, and the jackscrew that accomplishes the deflection. For the pilot to have considered that the THS was "AutoHelping" he would also need to determine that it was also a hindrance. Operating an airbus with the certain knowledge that the a/c was creating a problem is not perhaps in the cerebral databank of its operator. Likewise, the Manual Trim as safety device. The airbus needs a safety device? This may be too subtle for normal flight, but in the tall weeds it may have been a factor.

At the risk of parsing too closely, In the audio where the pilots are noticing "No indications", is it surprise one senses? Or Betrayal?

One hopes that some more research (NASA still working on this?) will shed light on the degradation rate, or mode. (Then again, there are those Goodrich probes ... :8 )

Bear, in a curious way, the elevator and THS work together like Charlie Kaman's servo flap/rotor blade lashup in the old SH-2, and the current KMAX, helicopter. What you end up doing is using a small airfoil to change the pitch of a larger airfoil until equilibrium is reached.
Take a look at this picture.
http://upload.wikimedia.org/wikipedi...0px-N267KA.JPG

That little tab near the end of the rotor blade is the servo flap. The pilot's inputs via cyclic (stick/sidestick analogue) moves the servo flap, which changes camber of airfoil (blade) which aerodynamic forces then resolve into a new pitch angle. (The difference in actual function, and where the two are not the same, is in the moveable THS in an airliner being internally adjusted (motors and hydraulics) to a new position to reach the new stabilized position based on the change induced by elevator movement, rather than how the KMAX does its thing by harnessing fluid flow effects).