airtren

I am not sure if it's helpful... In essence, the calculations are done very, very quickly, a lot quicker than the time relevant for moving a control surface between two distinct consecutive positions - 6 (microsec) to 9 (nanoseconds) order of magnitude. At that calculation speed rate, the calculations would be looking like being done in parallel, even if they were done serially.

bearfoil

To understand airtren, a simple question? How long after A/P loss is LAW change to ALTERNATE?

A33Zab

hi Gums,

Don't get me wrong, the 1°/g is not an absolute value.
It is used to explain the elevator deflection criteria.

The massive THS/Stab for heavy transporters are 'slow' screw driven, therefore the elevators takes the short term pitch orders while long term orders are for THS to neutralize elevator deflection.

The exact logic inside the PRIMs is for obvious reasons hidden from public eyes.

Since it is 'gee' driven it won't need a speed signal to operate, (speed used for rates and gains) but if it is missing the IR(accelerometers) it definitely revert to DIRECT.
Already in the first BEA report page 54/55 it was stated and explained why the system went in a latched ALTERNATE 2 law.

The figure and text is extracted from the FCTM.

JD-EE

jcjeant, the stall alarm was reliable as long as the PF recalled the overly complex set of rules for the stall alarm being suppressed.

this is the sort of logic I contemplate
If the plane is in the air (no weight on wheels or wheels retracted)
thenNumbers need to be teased out somewhere. Even logic as simple as this is better than what the have now, as I see it:
If the plane is in the air (no weight on wheels or wheels retracted)
if airspeed is valid and below threshold
thenelse
then (airspeed invalid)(A perfect solution is hard to derive and requires AoA and other criteria. I'd also put some hysteresis on the warnings so that they're a little harder to trigger and a little harder to un-trigger.)

(Sorry about the formatting - it's best I can do with this interface in a reasonable amount of time.)

A33Zab

where have you been last years?

1 sec!

02:10:05 AP disengage.
02:10:06 ALTERNATE LAW (at the start of the 10s monitoring proces)
02:10:08 A/THR disengage.
02:10:16 ALTERNATE LAW LATCHED.

A33Zab

You forgot to program an END IF, EXIT IF and ERROR handler.........

Before 02:11:45 the CAS was not below 60Kts and SW operational.
They modified the system, AOA input to IR part of ADIRU and SW will now be NCD if CAS below 30Kts. (call it progressing technology)

I think they should prevent the A/C to become in such a upset situation.

takata

Sorry also. I have re-read what you wrote and picked "leg" as the entire flight (as I remembered you corrected me on this point). Hence, maybe I confused you with my answer, as you get it right concerning this part of the flight.

My emphasis was to point at AF system for long-haul crews (équipage renforcé) which:
- do not use "relief" pilot (limited duty).
- do not rank F/Os (senior/junior)
- let the captain to decide and annouce who will be the pilot in charge between the two F/Os while he is resting.

What changed in the system is:
- Before: Pilot in charge was PF during captain's rest. (AF447 case).
- Now: Pilot in charge is PNF, in left hand seat, during captain's rest.

takata

In fact no... they don't sound very similar. It's due to their particular prosodie (tone). Both are interjectives which phonetically sounds quite differently (at least for French native speakers): "hein ?" and "euh..." are not usually confused in transcription.

- "euh..." is a sign of hesitancy, hence it is pronounced low, like a breath.
- "hein ?" is a sign of insistancy, hence it is pronounced high, short and distinctively.

Also, "hein ?" would call for an answer / acknowledgement :
- je suis d’accord qu’on est en manuel hein ?
- Surtout essaie de toucher le moins possible les commandes en en latéral hein ?
- Je suis en TOGA hein ?

Hence, "il est où euh..." should point at something ("where is [it]... ), not at someone (who else?). The PNF only called the captain after saying that. Before calling him, he perfectly knew where his captain was (resting).

I will agree with your good point. Interpretation is based on context which is the primary clue. Notwithstanding, Such talks reading are revealing some ambiguousness not always easy to catch at first glance. Moreover, those dialogues are not complete and are lacking the necessary punctuation.

CVR transcipts lacks crucial referentials to be perfectly understood. If one factors the intrinsic ambiguousness of any langage while, in translation, further involontary ambiguousness could be added in the process, this may end quite far from the reality. Do not expect something clearer once released in English, rather the contrary!

jcjeant

Hi,

Come back from some pages .. (this thread run quick lol)
takata
Yes the captain tell "here it is,use that"

It answers who and what he was asked?
Mystery ..
Typical error you said ?
I rather think that we lose our time trying to put words into actions and timing
The CVR transcript in this Report No. 3 is very incomplete (it does not take a linguist to say such a thing)
No doubt the final report will be more complete
And last .. it will certainly be the complete version during the trial .. because judges and lawyers will not be satisfied by charades we read now

Old Engineer

Thank you for the useful information of your last post (00:24 Z on 2d). I'd say you have to be very well informed. I mean, it's more than just having a manual lying around. I have some questions-- you wrote:

"The massive THS/Stab for heavy transporters are 'slow' screw driven, therefore the elevators takes the short term pitch orders while long term orders are for THS to neutralize elevator deflection."

My question here is, when CG is full aft, and elevator authority thus at a designed minimum of 1 degree per 1 g, how fast does the "slow" screwjack move the plane of the HS, compared to how fast the movement of the SS moves the elevator through 1 degree?

It seems to me that in any case, the rate at which the screwjack catches up with the elevator is 2-1/2 times faster at full aft CG than it would be at full forward CG. This further seems to me that PF would have only 40% as much times to assess the results of his SS inputs, when CG is full aft, compared to his situation with CG full forward. Am I missing something there?

Beyond that, it is fairly obvious (well, I didn't see it until now, I admit) that 13 degrees NU of the HS jackscrew cannot be reeled off regardless of the speed of the jackscrew, until the A/C has reduced its forward velocity to the point where such angle NU of the HS will not tear the wings off (ie, g < 2.5) (or is there some law where <3.5 would apply?).

It further appears that at some lesser value of degrees NU of HS the A/C is not actually flying, but is so slow that it must stall out. It would seem this angle would be rather readily calcuable. Why did the control computers for trim not make this calculation? Would not air density per altitude probe been the only outside information needed for this? ... together with weight of A/C less fuel burn and fuel in HS, presumably available on board to the computers...)

I admit to asking the question without taking time to see if I am overlooking something obvious. But it would still be better for someone of your familiarity with the THS issue to give an authoritive answer than for I to muddy the waters here by claiming it has to be the way I am seeing it at the moment. Thanks.

Also, in going to 15 degrees NU of the A/C attitude, what is the effect of partial fuel in the hollow HS sloshing to the rear of the HS tank, on aft CG... and then on the above considerations?

A33Zab

I did post the image before, THS movement E4 thru E5 related to TOGA C4 thru C5

Now with this text from FCTM:

Flight Mode
In pitch, when an input is made on the sidestick, the flight control computers
interpret this input as a “g” demand/pitch rate. Consequently, elevator deflection
is not directly related to sidestick input. The aircraft responds to a sidestick order
with a pitch rate at low speed and a flight path rate or “g” at high speed. When no
input is made on the sidestick, the computers maintain a 1g flight path. Pitch
changes due to changes in speed, thrust and/or configuration, which in a
conventional aircraft would require the pilot to re-trim the aircraft, are
compensated for by the computers repositioning the THS. The pitch trim wheel
moves as the control law compensates for these changes. Sometimes, changes
of trim due to changes in thrust may be too large for the system to compensate,
and the aircraft may respond to them in pitch in the conventional sense and then
hold the new attitude at which it has stabilised after the trim change.

airtren

Takata,

My reading of the BEA text was also that the PNF was referring to the "Captain" as the BEA document refers to the PNF calling the Captain in the couple of seconds following 2:10:47 - the "il est ou, euh" is at 2:10:49.

But if I let myself convinced by your post, and look at what could "il" be in "il est ou, euh?..." as in something that he does not find... and the Captain brings and hands back to him, then:

You've mentioned "documentation". But "documentation" in French is feminine, therefore it is replaced by the pronoun "elle", not "il", so it's not that.

2. a page? - French "la page" is feminine, prenoun should be "elle"...

so it's not that

3. instruction? - French "instruction" is feminine, therefore "elle"

so it's not that

What else then, as the "genre" seems to be a problem for those three....

jcjeant

Hi,

No problem ..
The French language is rich in synonymous
takata will answer to you by:
The instruction book (male)
The workbook contains the documentation (male)
etc. ..
If you really think that the question was related to documentation ... you are now satisfied because the gender issue is resolved

JD-EE

To be fair there is no practical way to duplicate the conditions encountered for testing purposes other than millions of hours flying looking for those conditions and running tests in the few seconds the test plane is within those conditions. They're that exotic. There is also the problem that nobody could conceive of such conditions existing until very recent years.

Flying today is an order of magnitude or two safer than it was in the days of the "old farts" here. Dredge up statistics for yourself. You owe it to your reputation for honesty and fairness around here.

(Yes, I looked it up. B is slightly safer than A at this time for current models. All are so much better than the old C, D, B707 era, and other older planes it's silly to compare them on a linear graph.)

promani

SAturnv

"The wife of the PF had gone with him to Brazil because the crew had a long layover in Brazil. As it was also Pentecost weekend, this meant a long holiday weekend. She taught physics in high school. Their two young sons remained in France"

I know many families must have been destroyed by this accident, but after reading the above it just choked me up. To think that these two young boys would have been told that 'mummy and daddy' will be home in the morning. And when they woke up someone had to tell them that 'mummy and daddy' will not be coming home.........ever.

Old Carthusian

Lonewolf 50
The pitot tube issue despite being the trigger is actually irrelevant to what caused the accident and I think one has to be careful not to attribute a major design flaw to the pitot tubes. To say that there is something wrong with the aircraft is a value judgment implying a serious problem. Remember, according to BEA the pitot tube problem in this incident did clear itself up after a short period.
The actual issue, though is why the crew reacted to the situation they were in in the particular way they did. What caused them to ignore the procedure for UAS? This is the issue, it is nothing to do with the aircraft. Attempts to somehow blame the aircraft are erroneous. One has to look at training and responses to unusual situations. As many others have noted - on the information we have this was not initially a serious incident. We are in the realms of psychology and human reactions here, not physics or computer science.

jcjeant

Hi,

I think so too .. say otherwise would be in bad faith.
On the other hand we must also realize what the objective criteria that have achieved such results
There are many and not only the progress made to the aircraft or avionics.
The airports are now equipped for the most part help ensure a better security approach for landing
Weather forecasts and knowledge of the atmosphere at altitude also helped to improve safety.
In terms of plane .. the engine has made tremendous progress and thus the fatal engine failures are rare
The FBW has assisted flight and also allowed to consider the construction of aircraft with new materials and significant economic returns have been created.
And there are other aspects that certainly forget
Remains the Achilles heel ... pilots ...
Considerable progress is still to do on this side .. since .. statistics have now changed and the human factor (errors) took the lead in the reasons for accidents
Anyone know where is the problem ..
Now .. as has been done about any technical problems .. we must find solutions .. is certain that despite other progress .. figures and statistics will frozen in the state as today .. or worse .. deteriorate ...

I hope you will be in court of justice for explain the facts above ...
Thales and Airbus will have you a debt of gratitude if you been as persuasive in your message
I dunno if AF will be so happy ....

Graybeard

Old Carthusian:
In spite of meeting certification specifications, heating of pitot probes is hardly rocket science, and to have them ice up repeatedly in a $multi-million plane means the design or maintenance is inadequate. The Thales AA probes were condemned, as were the Thales AB probes. Even the Goodrich replacements on an A330 have suffered at least one icing event.

This points to either unfortunate placement of the probes, or insufficient heating from the airplane's power source. Something as minor as probe bonding to aircraft skin could adversely affect the heat transfer.

Yeh, I suppose you could argue if it hadn't been iced pitots, some other event would have eventually brought that (incompetent) crew to grief. I don't buy it.

PJ2

airtren;
Yes it is helpful, thank you, airtren. I didn't state it as such, but it was indeed the speed of processor operation that I was thinking about in terms of the "disconnection two seconds before the CAS dropped" - that the speed of processors enable downline processors (FCPC's to be exact), to "know and act", (ie., disconnect the AFS) long before the data recorders, sampling at various but obviously much slower rates, "knew" and recorded the event.

It is a point regarding the reading and interpretation of flight data that I have been wishing to make since the beginning - that when it comes down to microprocessor speeds we cannot say what is occurring "in-between" SSFDR data points and especially when we are examining parameters with different recording/sample rates such as 'g', which is typically eight to sixteen times-per-second, and CAS which is typically (depending upon dataframe programming), once per second and sidestick position which is typically four times per second - we cannot always interpolate data points in such events because there is often sufficient time between samples for a parameter to reverse itself or go to a limit then return, the actual recorded values being "none the wiser", so to speak.

In response to your question HN39, and I'm just exploring the idea I here that I began developing in my first response, (and it may be stretching a point, I don't know yet!), - that the drop in Mach, which shows up in the data as one second long and (apparently) "caught two seconds before the CAS" may be the result of the nature of flight data recordings rather than an actual two-second difference. There is a small dip in CAS at the same time the Mach goes to M0.26, but that may be looking for data that isn't there.

The question is really, Did the FCPC disengage the AFS two seconds before the CAS showed a drop, and if so, what engagement condition was no longer satisfied among those listed in the AMM, or is the above notion a plausible explanation?

Old Carthusian

Indeed it can be argued that the pitot tubes could be better designed and also that Air France should have taken quicker action to replace the Thales design with the Goodrich design.

That does not negate the need for the crew to respond appropriately to the incident. This crew didn't and how and why the crew responded to an incident which wasn't necessarily terminal is the key to the accident. It doesn't rest on incompetence but what caused them to disregard laid down procedures and adopt a totally different course of action. This question is not an aircraft issue but a human issue. After all pilot training for these big aircraft rests on dealing with unusual situations in the simulator. Maybe this situation isn't covered in which case there might be a training deficiency. Even if this is the case training should have been sufficient for the crew to successfully diagnose and avoid the stall and crash. I did mention in a previous post that there are occasions were people will do something they actually don't think they are doing in a stress situation and others have spoken of the instinctive reaction to pull back on the stick. This may have a bearing on what happened in the cockpit. Here is where training and standard procedures are vital. As to why this crew did not follow the latter - this is what I mean by the realms of psychology and human reaction. The transcript released by the BEA is instructive.