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Habsheim

Old 9th Apr 2014, 17:23
  #761 (permalink)  
 
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But again, why do you still persist equalling Valphamax and stalling speed ... ?
And if you do think Valphamax is Vs1g at 110 then what is Vstall ?
This has been discussed extensively earlier in the thread. The Special Conditions for certification of the A320 (published by the FAA and linked earlier on this thread) define Vs1g as Valphamax. The certification requirements consider the airplane stalled when the longitudinal control is held on the aft stop during 2 seconds and there is no further increase of angle of attack. Vs1g is published in the AFM and the FCOM. There is no requirement to determine Vstall, assuming that you mean the speed corresponding to the maximum lift coefficient calculated at 1g. 'Vstall' is not published anywhere, AFAIK.

True that all these speeds, all of them, including Vls Valphaprot, should have been published in the report for the weight config altitude at the time ... Where are they ?
All these speeds are irrelevant to the accident, and I can't see any need for the accident report to publish them. The report publishes alphaprot, alphafloor and alphamax, which are relevant.

For the graph, things don't add up.
How do they or you get identical speed traces from so different attitudes ?
An obvious penalty on the speed there must be by pulling the nose up ... but also a benefit to the altitude ... Where are the ?
IAs and pitch attitude have been read the graphical presentation of Bechet's simulator exercise. AoA has been determined as the difference between pitch attitude and flight path angle. The vertical speed can be determined from the trace of radio altitude, and FPA is determined from VS and TAS. If there is anything that doesn't add up, please be more specific.
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Old 9th Apr 2014, 19:10
  #762 (permalink)  
 
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This accident was 26 years ago, yet reams of fascinating info regarding the secrets of the 'bus "logic" continue to fill these pages.

And all this in addition to the acres of apparently "new" knowledge following the report on AF447.

I admit I'm an ex-Boeing driver, but the whole process of revelation and presumably education of 'Bus drivers following a major accident, gives me no confidence as l board my next Airbus flight as SLF.

If the beast really is that complicated, and so much info remains in the filing cabinet at Toulouse, then surely those who are NOT 'Bus enthusiasts are entitled to ask is this the best way to go in aircraft design and operator instruction?

787 design team please note?!?!
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Old 9th Apr 2014, 21:02
  #763 (permalink)  
 
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Originally Posted by OK465
For an aircraft without a cockpit AOA indication I'm not sure I agree.
If I understood Confiture correctly, he was criticising the report, not the lack of cockpit AoA indication. Considering that the cockpit display includes Valphaprot and Valphamax, which speed would you like to add?
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Old 9th Apr 2014, 21:38
  #764 (permalink)  
 
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Originally Posted by BARKINGMAD View Post
This accident was 26 years ago, yet reams of fascinating info regarding the secrets of the 'bus "logic" continue to fill these pages.
It's not really that complicated to be honest. Ultimately we're talking about differences in mode that didn't really have a great deal of effect in the grand scheme of things.

I think one thing that is coming out of the discussions above all else is that the only guaranteed way that accident could have been avoided was to not point an aircraft full of pax at a forest and chop back the power in the first place! That's an airmanship issue, not a technical one.
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Old 9th Apr 2014, 21:58
  #765 (permalink)  
 
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Dozy, "It's not really that complicated, to be honest."

Nearly 800 postings on the latest Habsheim thread and almost 1,000 on the last AF447 thread surely scores higher than any Boeing, excepting of course the mystery of MH370?

Admitted it's not an exhaustive analysis of the tech aspects of either breed, but maybe there's something in it?

It would be interesting to know from 'bus line dogs how much more they have learned about their 'frames if they've followed the discussions in these fora.

Yes, l learned things about the 73NG which otherwise would have remained hidden after reading reports various, but doubt that the volume of previously unknowns gets anywhere close to the Airbus genre.

Tin hat is on...........
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Old 9th Apr 2014, 22:53
  #766 (permalink)  
 
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Originally Posted by BARKINGMAD View Post
Nearly 800 postings on the latest Habsheim thread and almost 1,000 on the last AF447 thread surely scores higher than any Boeing, excepting of course the mystery of MH370?
Actually, I think you'll find a lot of both those threads were invariably the same bunch of people trying to insinuate nefariousness on the part of Airbus, and useful idiots like myself trying to rebut them. I'd say of those threads, about 20% of them were actually worthwhile info - and that's a generous estimate!

In fact, Airbus's original EFCS technology as a whole was somewhat less complex than the T7 - the force-feedback logic being almost as complex again.

The issue with Airbus discussions on here is that there are definitely a core of pilots - usually, though not always, from France and allied with SNPL - that insist Asseline was wronged by a French government cover-up, and no matter what the actual discussion is about, some of them will try to turn the conversation back to that. I'm hoping this thread will answer any remaining issues and end the ridiculous excuses in future...

[EDIT : Put it this way - the level of software implementation we're talking about here would be roughly the equivalent of knowing about the tensile properties of metal cables and hydraulic flow rates on conventionally controlled airliners of yesteryear - which pilots didn't really need to understand in order to fly the aircraft!]
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Old 10th Apr 2014, 08:12
  #767 (permalink)  
 
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@ OK465
The simulations appear to be well conducted and reasonably high fidelity with respect to that specific aircraft and incident....but as previously noted, the plots not so much. In addition to the pitch attitude inaccuracies, I particularly like the Pg 13 IAS plot that is moved upward halfway thru the simulation and connected with a vertical dashed line.

I think there's possibly a little more pride taken in these type of presentations nowadays.
I take your point, but I do wonder if we aren't being a little harsh when we judge a 1988 presentation by the standards of reproduction equipment available today.

The four "simulator" charts bear all the hallmarks of having been produced on an analogue pen recorder - the sort where paper is drawn past a line of pens which move only transversely across the paper. To analyse the data subsequently one had to annotate and add scales by hand so these are inevitably "untidy" compared to a printed version.

To add to the misery the gridlines on the plotter paper were, IIRC, printed in a delicate shade of pink, which was great if you were reading directly off the plotter paper but which all but disappeared when passed through the sort of copying machine then available.

Both these "faults" are present in the published charts, but they could have been then state of the art

About 10 more seconds of the sim plot on Pg 13 might have been interesting and actually I don't see where it would have cost anything to continue it to purported alphamax and present it. The sim was already set up and rolling.
I agree it would have been interesting, but it would have been open to the accusation that the extra data was speculative. As it stands the plot stops when the DFDR records stop, so is appropriate for a formal accident report.

I would guess that the extension you advocate was looked at - in fact the BEA report (p.15) talks about "other studies", but these were treated as background material.

If one is prepared to speculate a little it is possible to get some idea of what might have happened - check your PMs.
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Old 10th Apr 2014, 20:23
  #768 (permalink)  
 
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Originally Posted by Owain Glyndwr View Post
@ OK465
I take your point, but I do wonder if we aren't being a little harsh when we judge a 1988 presentation by the standards of reproduction equipment available today.
...
Both these "faults" are present in the published charts, but they could have been then state of the art
Quite. I've been saying this for a while, but it's easy to take for granted the relative simplicity in transferring this kind of data and rendering it in different ways today compared to the hassle it was even 20 years ago. For example, in 1990 (when this final report was published) the current spreadsheets could not handle the amount of data that was dumped from the DFDR - and there was no way to even get that data into that format directly other than manual transcription - the risk of miskeys would have been too great.

Even if it were possible, the current version of Windows was 3.0, and the current version of Word was 1.0 (for Windows). In June 1990, these would have been effectively brand new products, and while it was technically possible to insert Excel data into WFW 1.0, Excel could not generate charts - that didn't really come into its own until about 1993-4.

Obviously the realisation that these tools could be used in this way did come, and modern reports use that method routinely these days. However, this was a result of a near-revolution in desktop computing power throughout the 1990s, and simply wasn't available for the publication of this report. As BARKINGMAD says, we're talking about an accident that happened almost 26 years ago, and a final report that is almost 24 years old!

Last edited by DozyWannabe; 10th Apr 2014 at 21:10.
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Old 10th Apr 2014, 22:45
  #769 (permalink)  
 
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@ Barking

It is interesting that we are still here talking about the FCS implementation and such after such a long time.

The point is that many heavy pilots have never flown their planes to within a hair's breadth of the programmed limits.

The accident was caused by a low power setting and lack of practice and plain poor judgement ( demonstrating the jet at its max AoA with pax on board at a ridiculous altitude). Sheesh.

I go with Doze and Okie for the most part. And I think Okie flew the same jet I did in his previous life, which was full FBW and very clear limits defined as to the aerodynamics.

The mentality that the cosmic flight control system will "protect" you is dangerous. We don't all have to be super engineers or test pilots, but we do have to understand the "limits" and then all the reversion modes of both the FCS and the autothrottle ( Asiana).

So I feel that good training in the real jet as well as the sim could help here. I know that $$$ count, but seems to me that a few hours and maneuvers in the real jet would pay off big time.

AF447 PROVED that you could stall the jet if you climbed at such an angle and ran outta speed before the magic FCS could help. The plane was still recoverable, so it was not truly in a "deep stall", it was "deeply stalled".

That's all I gotta say here from the peanut gallery.
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Old 10th Apr 2014, 23:55
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Originally Posted by gums View Post
AF447 PROVED that you could stall the jet if you climbed at such an angle and ran outta speed before the magic FCS could help.
To be fair, that particular scenario (i.e. hard protections are void outside of Normal Law) was explicitly highlighted in the manuals from the beginning. Even the most strident Airbus evangelist wouldn't have claimed the protections to be a universal remedy - though the press may have muddied the waters there. The company received a tragic object lesson in that when one of their chief test pilots was killed during a training/demonstration exercise in an A330. From that point onwards, they tended to be even more circumspect.

I think the reason this particular accident still causes discussion and debate today hinges - at least partially - on the fact that the report was only ever published in French (which was standard practice when no international body was involved), and most of what the Anglophone world knows about it was filtered through the press.

Asseline's argument was that the aircraft did not respond to his full back-stick command. The BEA research indicates that it did respond, but due to the late application of thrust and even later application of the back-stick command, the rate of response was initially slower than it might have been. This was not a routine operation - far from it - and if it had been, then maybe the details which this thread has uncovered would have been more widely known. As it was, the investigation concluded (rightly so, in my opinion) that the systemic lack of oversight was the primary factor in the accident, with the somewhat poor airmanship during the conduct of the flight also contributing. A radical overhaul of the practices regarding commercial aircraft performing demonstrations at airshows was thus sufficient to prevent a recurrence.

[EDIT : I must say that while I'm appreciative of the namecheck, IMO the dynamite work on this thread has come from Owain Glyndwyr, HazelNuts39 and Chris Scott as well as OK465! ]

Last edited by DozyWannabe; 11th Apr 2014 at 00:10.
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Old 11th Apr 2014, 14:30
  #771 (permalink)  
 
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gums
447 and Habsheim are two different things. Protection was never an issue in AF447 as the aircraft was in alternate law and you could always stall. It was lack of procedural knowledge on part of pilots was the cause. In normal law you have the protection as was the case in Habsheim but here the issue that was being raised was did the protection cause the accident. Both side have gone considerable distance with interesting inputs although only agreeing to disagree.
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Old 11th Apr 2014, 16:18
  #772 (permalink)  
 
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@ vilas

I don't disagree with you about AF447. My concern is that it appears some 'bus drivers seem to feel that they can't stall the jet, and then the lack of certain "protections" in the various reversion modes comes into play when things go south.

That is why I suggested better training both in the sim and in the real airplane. I know involves lottsa $$$, but sheesh.

In the early days of my experience as an IP in a full FBW jet, we first let the student get used to the side stick, and then we would go to the limits. We did not have a simulator for 3 years after the jet became operational! And you could not demo the gee limiter in a stupid sim.

Habsheim was a great example of poor planning, poor preparation, and poor judgement. Sorry to come down hard on a fellow pilot, but that's my feeling. Even our demo hops for the crowds allowed for some leeway, and the maneuvers were practiced over and over. A degree or two of AoA that the FCS allowed at max command was never a consideration.

Back to my peanut gallery......
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Old 11th Apr 2014, 16:34
  #773 (permalink)  
 
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Originally Posted by vilas View Post
... but here the issue that was being raised was did the protection cause the accident.
I think it's fair to state that the protections didn't "cause the accident" - as there were massive "holes in the cheese" present before the aircraft ever left the ground. Ultimately, I think even the sceptics have to admit that the airline should never have allowed the flight to go ahead without proper review, plus the airmanship and decision-making after getting the airfield visual were questionable.

The question is not about whether the protections "caused the accident" as much as it is whether the slower initial response due to HAP mode made the contact with the trees more substantial than it might have been. At this point I think agreeing to disagree is the best we can manage, because as I said before, there are simply too many variables involved to make a definitive educated guess.

@gums - If there are FBW Airbus pilots who believe they can't stall one under any circumstances (and to be honest I'm sceptical of that), then they clearly haven't read the manuals and training materials properly and require being pulled off the line for immediate remedial training!

I know there's a school of thought that has the AF447 PF pulling up because he was expecting the protections to keep the aircraft in check, but there's no clear evidence of that. The fact is that there have been studies performed into startle response, which found that severe cases of startle will cause a pilot to instinctively pull up in (IIRC) 80% of cases regardless of whether the aircraft has AoA protection or not.
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Old 12th Apr 2014, 04:11
  #774 (permalink)  
 
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DOZY
I am in agreement with you and I also do not believe there pilots out there who do not know that Airbus can be stalled in alternate law. Pilots are getting complacent on automation and loosing their basic scan. Far too many accidents happen because of not monitoring speed on approach. Take SFO for instance no pilot is going to keep quiet when he sees the speed is 15/20 KTS below Vapp. They simply are not looking at the speed because most of the time automation looks after it. AF447 pilot applied memory items of after take off situation otherwise there is no requirement of TOGA power. Unreliable airspeed is only practiced during type rating and never in yearly or six monthly checks.
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Old 12th Apr 2014, 20:31
  #775 (permalink)  
 
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Originally Posted by BARKINGMAD View Post
Tin hat is on...........
This thread does not offer anything useful apart from n-th refutation of "Airbus is evil" utterances. These anonymous claims of A brand corruption are based on notions about aerodynamics, thermodynamics and kinematics that are so implausible that not even mixing them liberally with theories of messieurs Einstein, Bohr or Schrodinger can make them look more realistic than average Klee's painting. Sir, if you think there is something of even a bit substantial in them, then your headgear is seriously overbuilt. Material is fine but thickness could be safely reduced down to mere foil.

Originally Posted by Vilas
AF447 pilot applied memory items of after take off situation
No. It says obtain and maintain 15 degrees pitch. It doesn't say "pull mindlessly, change your mind and reduce pitch somewhat then pull mindlessly again." There was no trace of seeking for specific pitch in AF447 case but was a lot of pulling-up-no-matter-what. Just as in Pinnacle (to a point). Or West Caribbean. Or Pulkovo. Or Colgan.
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Old 12th Apr 2014, 22:50
  #776 (permalink)  
 
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Barkingmad yep being ex Boeing myself now Airbus for quite a while. I was surprised after AF447 to find out the 330 stall characteristics as all the stalls done in the sim were conventional (buffet then pitch down) no one mentioned it could "deep stall" the bus does require continuous study. They are fascinating however.
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Old 13th Apr 2014, 00:40
  #777 (permalink)  
 
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Originally Posted by HN39
Considering that the cockpit display includes Valphaprot and Valphamax, which speed would you like to add?
The cockpit displays only include what is believed to be Valphaprot and Valphamax according to the FAC ... but such characteristic speeds have theoretical values, and knowing that Asseline was playing in that area, it should have been the most natural thing for the BEA to communicate those values in their report.

This has been discussed extensively earlier in the thread.
Extensively but erroneously - If Vs1g was Valphamax Airbus would not have called Vs1g "stalling speed".

If there is anything that doesn't add up, please be more specific.
I cannot be more specific than that :
How do they or you get identical speed traces for Bechet and Asseline as they adopt so different attitudes ?

Originally Posted by Owain Glyndwr
To analyse the data subsequently one had to annotate and add scales by hand so these are inevitably "untidy" compared to a printed version.
Sorry but there is ample way to do it professionally ... or you can always choose to do it unprofessionally.

To add to the misery the gridlines on the plotter paper were, IIRC, printed in a delicate shade of pink, which was great if you were reading directly off the plotter paper but which all but disappeared when passed through the sort of copying machine then available.
Tell me ... is it that same sort of copying machine that swallowed Annexe VII ?
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Old 13th Apr 2014, 09:38
  #778 (permalink)  
 
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Originally Posted by CONF iture
How do they or you get identical speed traces for Bechet and Asseline as they adopt so different attitudes ?
Firstly, speed and attitude are independent variables. You can have any speed at any attitude.

Secondly, one of many explanations is that Asseline flew into a forest and Bechet did not. Asseline's IAS would have been higher that Bechet's if he had not lost 5 kt of headwind in the 5 seconds before he hit the trees:

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Old 14th Apr 2014, 11:06
  #779 (permalink)  
 
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Originally Posted by CONF iture
If Vs1g was Valphamax Airbus would not have called Vs1g "stalling speed".
Compared to the certification requirement, that is a lame argument. Vs1g is the official definition of "stalling speed" for this airplane, and it is obtained with the sidestick on the aft stop at the corresponding AoA. How would you define Valphamax?

Furthermore, in Bechet's simulator test, at about 6.8 seconds after moving the thrust levers forward, the AoA is 17.5 degrees and the airspeed is 116.5 kIAS. According to the FCOM, Vs1g is 109.5 kt at a weight of 59,000 kg, so 116.5 kt is 1.064 times Vs1g. The loadfactor at an AoA is proportional to airspeed-squared, and should be 1.064*1.064 = 1.13. That value is a perfect match with the loadfactor shown in the graph below, that is derived from the altitude trace (or the radius of the flight path) of the simulated flight.

In other words, Bechet's simulation confirms that Vs1g corresponds to alpha-max of 17.5 degrees at 1g.


Last edited by HazelNuts39; 14th Apr 2014 at 15:43.
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Old 14th Apr 2014, 17:29
  #780 (permalink)  
 
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Originally Posted by CONF iture View Post
Sorry but there is ample way to do it professionally ... or you can always choose to do it unprofessionally.
Given that we've established that the tools to generate and annotate the material digitally were not readily available in 1990, how would you propose they do it differently?

Tell me ... is it that same sort of copying machine that swallowed Annexe VII ?
Annexe VII is there. It was either mis-labelled by the clerk who compiled the paper copy, or the sheet inserted by the clerk who did the original compilation made a mistake in describing it. What the document scanning hopper *has* done is get the occasional pages scanned in the wrong orientation, but they do all appear to be present.

The way to check this would be to go and have a look at the original paper copy in the Republic archives, but I wouldn't know how to go about doing that (and as a foreign citizen may not be able to access it anyway).
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