Thanks for such first hand information, I am satisfied with point (1) - It is the minimum the BEA should have mentioned.
Point (2) is more delicate - Your information seems accurate to me, but the correlation with the CVR data, and also the Asseline's account, would need that crucial missing piece of info that BEA kept out of our sight ...

Take your time to go through MA account, but we'll need to look deeper as there is so much more to be discussed ...

I read the alpha graph to indicate that the aircraft quickly approached its 22 degree pitch limit and the down elevator bunt maneuver was to keep it from overshooting. The time ticks are relatively large 20 second increments.

Much more maneuvering g available in the example than at Habsheim.

I'm wondering whether these systems calculate limiting pitch angle based on excess thrust available at the instant? I'll have to read the report more carefully.

A33Zab, thank you for your post, which, although not directly relating to AI products, is still highly relevant.

Quotes from OK465:
"But the current [Airbus] software is probably many FCS software iteration revisions from 1988."

Yes! I wish all our contributors would bear that in mind, particularly when interpreting data from later accident reports... Why would it not have changed? The guys at St Martin-du-Touch would have been constantly striving for improvement, as well as accommodating the new birds.

"I was young then."

Really? :rolleyes:

... and more than a runway separated them from the guys at 1 Rond Point Maurice Bellonte.

The flight had been briefed to be at 100 ft along R/W 34 L.
Perhaps due to the realignment with grass R/W 34 R the aircraft used some of its potential energy (now only height and airspeed, with flight idle having been set at 12.44.14) the descent to 46 ft became inevitable. This required more of a climb than had been planned - or an earlier selection of TOGA by a few seconds ( 10 ?).


Many pilots must have learned a valuable lesson since seeing what happened.


PS. Some could be younger, too !

In your post #266 you quoted from the preamble of the FAA Special Conditions for the US type certification of the A320. Development testing is not certification testing. In the Special Conditions it is evident that certification tests to determine Vs1g are conducted in normal law, the AoA protection system operating normally, except that alpha-floor must be disengaged.

Special Condition 6. Flight Envelope protection, (b) Angle-of-Attack Limiting, under (1)(i), states: Conditions associated with the determination of the stalling speed are those provided in § 25.103 of the FAR.

Relevant sections of FAR § 25.103 as amended by the special conditions read:

(a) VS is the reference stalling speed with--
(1) Stalling speed determined at not greater than IDLE thrust (NOTE: automatic go-around thrust application feature must be disengaged);
(2) (...)
(b) The stalling speed VS is the minimum speed obtained as follows:
(1) From a stabilized straight flight condition at any speed not less than 1.16 Vs (or speed at AOA protection onset, if greater) nor more than 1,30 Vs, apply elevator control to decelerate the airplane so that the speed reduction at the stall does not exceed one knot per second.
(2) (...)

In short: Vs is the speed obtained in normal law when the sidestick reaches the aft stop, i.e. Vs = V(alpha-max)

Is it surprising to you ?

Me: "The guys at St Martin-du-Touch would have been constantly striving for improvement, ..."
HN39: "... and more than a runway separated them from the guys at 1 Rond Point Maurice Bellonte."

Yes, the rather uninspiring Airbus premises - did they even exist in 1988? As you know, the south side of la ville de Blagnac has changed almost beyond recognition since the late 1980s, partly because of the creation of the rocade. (And, more recently, the north side of l'aeroport de Blagnac went completely bonkers - but that's another story.)

For me St Martin-du-Touch were the premises of Aerospatiale Engineering and Production facilities, and I was assuming that Airbus was responsible for FCOM, FCTM, pilot training and Customer Services in general, and of course, marketing and sales.

No not at all.

http://i55.servimg.com/u/f55/11/75/17/84/image10.jpg

If I wanted to confuse and discourage a reader, I would probably do that :

1. Publish the photocopy of a copy of a copy ... of the original
2. Not include the seconds of the GMT
3. Add a TGEN for which I would not specify the origin
4. Publish a limited amount of FDR data
5. Publish those data for only a short period of that short flight

Hi Chris,

In your post #133 you wrote:
I don't know if that issue was resolved. Recently I stumbled by chance upon a document entitled: The A320 Habsheim accident - An Airbus Industrie response to allegations ... .

On page 17 under "The CVR timing" Airbus writes:
CVR time 12H 44'31'' equated to DFDR time TGEN 266
TGEN is the timing in seconds from the start of the DFDR reading made by the investigators.

Does that help?

Hi HN39,

"On page 17 under "The CVR timing" Airbus writes:
CVR time 12H 44'31'' equated to DFDR time TGEN 266"

Thanks for drawing that CVR timing reference to my attention, which I had not noticed in the 1991 Airbus document. It certainly confirms your interpretation of the co-ordination between the GMT references and the "TGEN" time frames which you had used in your graph, and contradicts (by one second) my own as used in my post #122 of Dec 18, which I also used in #130 and #133.

So the BEA definition of t=0 at 1245:39 clearly occurs at DFDR time-frame 334.0 secs. IIRC, that is the last time frame in which none of the (sequentially recorded?) data was corrupted.

And the GMT minute is not updated until the time frame (TGEN) 1 second after the beginning of the minute, i.e., the first 1245 GMT (at TGEN 296.0) represents 1245:01, and the last 1244 GMT (at TGEN 295.0) represents 1244:60, which would be 1245:00.

RE:: Sequentially recorded?

The same document on page 12 has following Note:

Why suddenly changing the norm ... ?
Why simply not publishing the extensive FDR time reference ... seconds included ?

Is it really too much asking than expecting the investigators to specify which GMT H:M:S has been selected ?

It would be surprising that TOGA or FLEX has been selected before any takeoff clearance, but again, FDR data would tell more ... if only published.

Hi Chris Scott,
Sorry for the delay in finding this info.
You and Owain are correct. Please see http://sfte2013.com/files/78988645.pdf, slide 35

"Test Conduct - Stalls for certification
in FBW aircraft
• Initially performed at forward CG
• Must be performed in Normal Law
– In case a stall occurs despite the protections
– Airbus - Normal Law modified with higher limiting AOA"

edit.
Hi Owain Glyndwr,
Could than be explained by the FBW computers sensing the rate of speed decay, knowing the rate of pitch change available, and anticipating the change in attitude necessary to avoid exceeding aMax?

Hi HN39,
The above presentation suggests the aircraft is actually taken beyond CL Max, and its behaviour is observed in both Normal law and "Additional stalls performed with degraded control laws" (slide 35) to determine VS1g.

Hi rudderrudderrat,

Thanks for the link to an interesting paper. For the purpose of our discussion I think a few points are worth mentioning:

-- The presentation is dated 29 October 2013
-- It presents the views of Boeing and Airbus FTP's and FTE's, not necessarily that of the airworthiness authorities
-- The first bullet is "Stall Definition and Requirements", but the paper does not contain a discussion of that subject
-- The paper does not distinguish the tests conducted to determine the stall speeds from those to verify the stall characteristics or to identify aerodynamic characteristics such as the CLalpha curve

The A320 Special Conditions are dated 1988 and state clearly that Vs1g must be determined in normal law with alpha-floor disengaged. Consequently, Vs1g for the A320 is the speed obtained when the airplane is decelerated at 1 kt/s, the sidestick reaches the aft stop and is held there a few seconds. The published stall speeds and the cl-alpha observed in the accident (t-6 122 kt alpha=13.5) suggest that Vs1g corresponds to alpha-max of 17.5 degrees.

Hi rrr

Possibly, but it could be any number of reasons, and with absolutely zero knowledge of the VFW laws I would rather not speculate.

I would add though that the time history as shown is not IMO a very good response to a step elevator command. It certainly shows an effective limitation to alphamax, but as a response to a demand for maximum lift NOW! it leaves a lot to be desired. Sure it gives alphamax fairly quickly (as it should at 180 kts) but it only stays there for a very short time and that is followed by a very large response reversal and a slow climb up to maximum lift. In fact it takes about 20 seconds to get to a sustained alphamax.

AF447
 

May we go back to AF447 instead of pantomiming?
Order of French tragedies:
1) Rio
2) Perpignan
3) Toulouse
4) St Odile
5) Habsheim

OK, so coming back to this after a brief absence I just have to check - we're talking about the VFW-Fokker 614 used in the ATTAS programme - *not* the A320 - right?

From DLR Portal - Research Aircraft - VFW 614 / ATTAS - out of operation :

Or in other words, a European version of NASA's "General Purpose Airborne Simulator" JetStar. So I think it is at least safe to assume that the specification of that EFCS would have had significantly different behaviour goals than that of the A320.

Would you also say that while it may have been "good", it was nevertheless reasonable to truncate the published DFDR output to the time period relevant to the accident by the standards of the time?

The BEA are only charged with publishing material proven relevant to the accident. Neither of those issues on the face of it seem to be relevant to the accident itself. The A320 at the time had some technical issues to be ironed out - this was and is true of every new type one cares to mention (and the truism has been demonstrated recently with the A380 Trent issues highlighted by QF32 as well as the B787 battery issues demonstrated several times).

That the report didn't mention those particular issues is not a case of "hiding" anything, it's a case of those issues being irrelevant to the accident sequence in the first instance, and stating the bleedin' obvious in the second!

@Winnerhofer
And Concorde,
And Toronto
And unknown incidents

@rudderruddererrat
Thanks for the link. I hope A and B will continue these meetings with ICAO

@Hazelnuts39
I agree with your doubts.Who decided but Airbus themselves the special 1988 conditions replacing the regulators.


Does anybody know the certification date of Airbus in Vietnam (ref for USA...)?

In 1988 Capt. Gordon Corps (of the Air Registration Board and its successor, the Design and Manufacturing Group of the Airworthiness Division of the Civil Aviation Authority) was in charge of that work. At that time he was still an independent consultant and not an Airbus employee.

Another poster and I have been quoting from the FAA Special Conditions for the A320. These have followed the normal FAA process of rulemaking. A Notice of Proposed Special Conditions was published in the Federal Register on October 19, 1987. The comments received from the public in response to that notice are discussed in the preamble of the final rule. Regarding the reference stall speed the A320 Special Conditions are largely identical to the current standard of the regulation, proposed in 1995 and adopted in 2002 with FAR Amendment 25-108.

Many people from airworthiness authorities, manufacturers, operators and pilot associations in the U.S., Canada and Europe participated in the development of those changes in the regulations. In fact it would be difficult to identify a manufacturer of transport category airplanes or its regulatory agency that was not involved in that process. I doubt that any of those individuals would have claimed to be 'in charge of that work'.

Time stamps and DFDR/CVR synchronisation
 

Quote from me:
"...I'm still inclined to the theory that TGEN 000.0 seconds is most likely to be the instant that TOGA was selected on T/O."
Quote from CONF_iture:
"It would be surprising that TOGA or FLEX has been selected before any takeoff clearance..."

Yes, I should have done the arithmetic! That puts TGEN 000.0 seconds at 1240:05z, and T/O clearance was not issued until 1240:40z.

We know that movement of the throttle levers through the various thrust-limit gates, as necessary for the selection of TOGA from idle, is audible on the CVR. My assumption was that TGEN 000.0 would have marked a point of synchronisation between the CVR and the DFDR, but there is nothing in the CVR transcript - such as a lever movement, or the start of a transmission on the R/T - to suggest any audible event at 1240:05z that would have been simultaneously recorded on the DFDR.

So it may be that TGEN 000.0 is a purely arbitrary point. The Airbus 1991 document explains that the CVR is not time-stamped, but that the CVR records at a steady speed. I infer that a minimum of two synchronisation points some minutes apart would be necessary, to enable the CVR and DFDR recordings to be synchronised for the whole flight. The selection of TOGA a few seconds before impact would appear to be one ideal example. **

BTW, I'm still reading Capt Asseline's account. My PDF is missing the Annexes. Can anyone steer me towards obtaining them, please?

** The selection of T/O thrust on take-off would be another.

The BEA has made every effort to confuse the situation and make sure that what should be simple and straightforward is ... NOT.
Clac Clic Cloc and even Crac ! are happily mixed all along ...

You can find the Annexes for Asseline book here :
Crashdehabsheim.net

Go to :

• Bibliotheque
• Le temoignage du pilote (telechargeable ici)
• Telecharger les annexes

Poor phrasing on my part - I put it down to a combination of exhaustion and jetlag. :zzz:

Of course more people and organisations were involved, and I shouldn't have been so sloppy with my wording - but what I was trying to get at was that in Capt. Corps case at least, he was still primarily answerable to his CAA role in determining certification criteria and his role as a consultant would be driven by that as opposed to Airbus's corporate benefit (as rh seemed to be insinuating).

Er - how are they doing that? If I've got this right, you're talking about an appendix with the raw data over which the BEA have very limited editorial control. Remember that DFDRs were a relatively new technology at the time, and as such best practices were still being determined*.

Apropos of nothing, I find it somewhat ironic that you are criticising the BEA for supplying raw data (which can be opaque and confusing) in this case, yet you were demanding the release of raw data on the AF447 threads and criticising the BEA for not doing so. It seems to me that they can never do right as far as you're concerned.

EDIT :

* - For one thing, the computerised data manipulation tools and techniques which we take for granted today weren't fit for purpose in 1988. These days microcomputers are powerful enough to import vast amounts of raw data into a spreadsheet, and aligning the data visually is as simple as clicking and dragging a mouse. In 1988 there was still a significant gulf between the mainframes and minicomputers used in industry and the microcomputers used in offices and homes. The storage of data in a binary format was far from standardised - and even if that hurdle could be overcome, spreadsheets were only used on microcomputers, the most powerful examples of which in 1988 didn't have the RAM to effectively manipulate that much data.

Hi ruderrudderrat,
Thanks for the link to that recent presentation on stall testing. Very interesting.

Quote from me:
"I agree with CONF_iture, however, that it would be good to see the DFDR for the whole flight."
Reply from Dozy Wannabe:
"Would you also say that while it may have been "good", it was nevertheless reasonable to truncate the published DFDR output to the time period relevant to the accident by the standards of the time?"

Yes. If not, I would have said "...would have been good..."

It would be useful, however, for the purpose of our present discussions, not least to improve our understanding of the data. I would like to see the T/O and climb, if only to observe the acceleration of the engines from idle to T/O thrust (presumably TOGA, but I haven't seen a reference to that, and the copilot's FMA call of "THR" is apparently anomalous, unless the PF had selected Flex Thrust with no "assumed temperature" entered in the FMGS), the height at which the right turn was initiated, and the changing status of A/THR.

Hello Confit,
Thanks for that link to the annexes in Capt Asseline's account.

Agreed, if only for the sake of completeness. However, the BEA's response to Capt. Asseline's correct assertion that the elevators briefly deflected down while he had the stick back was a thorough real-world reconstruction of the aircraft's commanded flightpath - an experiment entailing significant effort and expense*. Is it not therefore reasonable to infer that the BEA compared engine performance data at take-off and during the accident sequence against both each other and an optimum set of test data - and found no significant anomalies?

One thing that has always puzzled me about Capt. Asseline's responses in the aftermath of the accident is that the BEA's report, far from assigning the causes purely to the actions of the flight crew, actually implicitly hauls AF's operations practices over the coals - not just in terms of highlighting the woefully inadequate briefing materials, but also highlighting contradictory rules and regulations pertaining to conduct of display flights. Reading between the lines the report more-or-less implies a reasonable argument that the crew were almost set up to fail. Capt. Asseline and his lawyers could likely have turned this into the most clear-cut example of mitigating circumstances in history, and yet they ignored that angle in favour of going after Airbus. To me this makes so little sense that I can't begin to fathom out why.

EDIT :

* - To put the question from another angle, if the BEA were being pressured to go easy on AI, why go to all that trouble and expense when a verbal response with no experiment would have carried the same weight in an official sense?

Quote please ... ?

Except from the "Clac Clac" mentioned in the CVR transcript at time 12 41 04 which could possibly mean that the FLEX detent was the one used for the take off, I cannot remember anything explicitly mentioned in the report.

Also from Asseline's account on page 103 :

Your post #336:


Points 2 and 3 in particular. You're looking at raw output right there - even if the technology existed to do so at the time, the BEA could not add GMT seconds or TGEN origin without by definition altering the data.

Additionally, your point 1 is likely just a consequence of the age of the document. The original digital files are likely locked away in an archive - the online version is purely for casual use, so digging the original up would likely not be cost-effective. Your point 5 is essentially the same as your point 4 and therefore redundant. Remember that the BEA is only charged with publishing data relevant to the accident. As I said above, if the engine performance at take-off and during the accident sequence was shown to be within normal limits, then there's no requirement for the BEA to publish it.

Quote from Dozy Wannabe:
"Is it not therefore reasonable to infer that the BEA compared engine performance data at take-off and during the accident sequence against both each other and an optimum set of test data - and found no significant anomalies?"

If one believed beyond any doubt that the BEA carried out a wide-ranging, impartial, and fully-informed investigation, that would indeed be a reasonable inference. But it would cut no ice with the BEA's detractors, and the bureau itself is unlikely - if you'll forgive the understatement - to enter into discussion on any alleged deficiencies.

Alternatively, we can all accept the findings and suspend further discussion...

Salut Confit,

I have not reached page 103 yet...

Your quote from Capt Asseline:
"Pour décoller de Bâle-Mulhouse, j'avais positionné les manettes des gaz dans un cran intermédiaire (FLX MCT), déterminant une poussée réduite au décollage [...]"

The CVR quotes the copilot's FMA call as "Thrust...", which happens to be abbreviated (as you know) to "THR" on the thrust FMA.

I therefore infer that the throttle levers were placed in the FLX/MCT gate (i.e., Flexible T/O thrust was commanded for take-off), but that no assumed temperature was presemt in the FMGS.

For other readers, the flexible-thrust "assumed temperature" is a device to order the engines to develop the lower T/O thrust associated with a higher ambient air-temperature than that pertaining on the day. It is calculated before departure as part of the T/O performance calculation, and entered manually into the PERF / Take-Off page of the FMGS by the flight crew. When the throttle levers are placed in the FLX/MCT gate for take-off, the thrust FMA should read "FLX nn", where "nn" is the assumed temperature, e.g., "FLX 53".

The issue as I see it is that most if not all of those "detractors" resort to obfuscating and, on occasion, outright misrepresenting the contents of the report in order to support their arguments. At the time, the lawyers representing Capt. Asseline and the SNPL union embarked on an almost unprecedented campaign to muddy the waters, briefing journalists with any allegation they could muster.

The ultimate outcome of this scorched-earth approach is that even people who are knowledgeable on the subject are frequently misinformed. I still hear talk of "the computer thought it was landing", "the autopilot was in command when it crashed" and "the report blamed the pilot" among other things - most of which, like those examples, are completely and demonstrably untrue.

If only...! :sad:

Seriously though, there's no such thing as a perfect report in the real world - but in my opinion the BEA performed an investigation that was at least as "wide-ranging, impartial, and fully-informed" as could be expected.

RE 1: In those days the BEA didn't have facilities to read DFDR tapes and decode the data. The tape was read at the CEV (Centre d'essais en vol), the french military flight test centre, which also does civil certification test flying and houses the french national test pilot school. The print looks to me like it was produced on a IBM typewriter or daisy-wheel printer and published in the report as it was received from the CEV.
RE 2: The DFDR GMT parameter probably records only hours and minutes (remember the timestamp of the AF447 ACARS messages?). The seconds have to be determined by counting the frames, and fractions of a second from the parameter position within the frame word sequence. Who sets the GMT clock in the airplane? The wording of the note in the Airbus memo suggests that TGEN is not a recorded parameter but a frame count added in the CEV printout of DFDR data.

Quote from HN39,
"Who sets the GMT clock in the airplane?"

I reckon that's a rhetorical question, but I can confirm that it's anyone who is inclined to do so. We never did it in flight. According to the FCOM, its timings are "sent to the CFDIU, FDIU and FMGC." The FDIU, of course, feeds the DFDR.

Quote from Dozy Wannabe:
"One thing that has always puzzled me about Capt. Asseline's responses in the aftermath of the accident is that the BEA's report, far from assigning the causes purely to the actions of the flight crew, actually implicitly hauls AF's operations practices over the coals - not just in terms of highlighting the woefully inadequate briefing materials, but also highlighting contradictory rules and regulations pertaining to conduct of display flights. Reading between the lines the report more-or-less implies a reasonable argument that the crew were almost set up to fail. Capt. Asseline and his lawyers could likely have turned this into the most clear-cut example of mitigating circumstances in history, and yet they ignored that angle in favour of going after Airbus. To me this makes so little sense that I can't begin to fathom out why."

You make a very reasoned argument, and it may well be that Capt Asseline was badly advised. Union politics are far too complex for the likes of me.

The presentation describes recent experience during testing of A380 and B787 and is looking toward the future. Slide 35 doesn't mention Vs1g.

Nothing in the presentation is in conflict with my position that the certified Vs1g for the A320 was determined in accordance with the Special Conditions for type certification of the A320: in normal law as designed for the production airplane except with alpha-prot disengaged. Additional tests were conducted with modified or degraded control laws to demonstrate stall characteristics and to obtain aerodynamic data beyond alpha-max (and probably beyond cLmax) for design purposes and for the flight simulator data package.

P.S.
This effectively means that the 1987 FCOM (Chris Scott #213) was in error when it said "alpha-max = alpha (1.06 Vs)".

@Hn39

That makes sense. Those additional tests (with an increased alphamax so that it didn't interfere with the testing) would have come first to establish what alphamax might be and the certification tests then completed up to that alphamax/Vs1g as you suggest.

Actually the CVR transcript is clear :
"Thrust SRS ! RUNWAY" at time 12 40 59

Anomalous I agree, as the call should have been either MAN FLX or MAN TOGA, but if no flex temp had been previously entered, and Asseline had set the thrust levers to the FLX detent, the ECAM ENG THR LEVERS NOT SET would have been triggered ... Was it different in 88 ?

And where my post #336 is "criticising the BEA for supplying raw data" ?
All I can see is demanding for more ... not less.

Quotes from CONF_iture:

"Actually the CVR transcript is clear :
"Thrust SRS ! RUNWAY" at time 12 40 59"

Yes, so we'll have to hope that my recollection of 25 years ago is better than that of what I read 25 hours ago! Thanks, I've amended my post.

"Anomalous I agree, as the call should have been either MAN FLX or MAN TOGA, but if no flex temp had been previously entered, and Asseline had set the thrust levers to the FLX detent, the ECAM ENG THR LEVERS NOT SET would have been triggered ... Was it different in 88 ?"

Yes, it was certainly different on the A320 in 1988 (I'm not au-fait with current A320 FMAs, which may or may not have changed). Your "MAN FLX" and "MAN TOGA" were simply "FLX nn" and "TOGA". In the absence of an assumed temperature in the FMGS (as inevitable on a touch and go), and the throttle levers at FLX/MCT, the FMA would indicate "THR". I don't recall any associated ECAM mesage, but am not sure. IIRC, the FADEC would deliver TOGA in that configuration, but it would seem sensible to advance the throttles to make sure. I've yet to find any reference to this situation in my contemporary FCOMs.