AF 447 Thread No. 9

[john_tullamarine]

AF 447 Thread No. 9

Thread part -

(a) #1 starts here (http://www.pprune.org/tech-log/395105-af-447-search-resume.html#post5303737) and finishes here (http://www.pprune.org/tech-log/395105-af-447-search-resume-195.html#post6408432). Posts = 3890
(b) #2 starts here (http://www.pprune.org/tech-log/449639-af-447-search-resume-part2.html#post6408428) and finishes here (http://www.pprune.org/tech-log/449639-af-447-search-resume-part2-127.html#post6476460). Posts = 2537
(c) #3 starts here (http://www.pprune.org/tech-log/452836-af447-thread-no-3-a.html#post6476336) and finishes here (http://www.pprune.org/tech-log/452836-af447-thread-no-3-a-104.html#post6515428). Posts = 2071
(d) #4 starts here (http://www.pprune.org/tech-log/454653-af-447-thread-no-4-a.html#post6515515) and finishes here (http://www.pprune.org/6561320-post1061.html). Posts = 1061
(e) #5 starts here (http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a.html#post6561270) and finishes here (http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-99.html#post6638007). Posts = 1978
(f) #6 starts here (http://www.pprune.org/tech-log/460625-af-447-thread-no-6-a.html) and finishes here (http://www.pprune.org/tech-log/460625-af-447-thread-no-6-a-85.html#post6793822). Posts = 1683
(g) #7 starts here (http://www.pprune.org/tech-log/468394-af-447-thread-no-7-a.html) and finishes here (http://www.pprune.org/tech-log/468394-af-447-thread-no-7-a-68.html). Posts = 1354
(h) #8 starts here (http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a.html#post7129212) and finishes here (http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-78.html#post7278807). Posts = 1550


Links to the various BEA reports are given below. If I have missed any of the useful papers, please PM me with the URL and I can include it.

(a) BEA site - French (http://www.bea.aero/fr/index.php), English (http://www.bea.aero/en/index.php)
- Report link page - French (http://www.bea.aero/fr/enquetes/vol.af.447/vol.af.447.php), English (http://www.bea.aero/en/enquetes/flight.af.447/flight.af.447.php)

(b) Interim Report (No, 1) Jul 2, 2009 - English (http://www.bea.aero/docspa/2009/f-cp090601e1.en/pdf/f-cp090601e1.en.pdf)

(c) Interim Report No. 2 Dec 17, 2009 - English (http://www.bea.aero/docspa/2009/f-cp090601e2.en/pdf/f-cp090601e2.en.pdf)
- Update Dec 17, 2009 - French (http://www.bea.aero/fr/enquetes/vol.af.447/point.enquete.af447.17.12.2009.pdf), English (http://www.bea.aero/fr/enquetes/vol.af.447/update.on.the.investigation.af447.17.12.2009.en.pdf)

(d) Estimating the wreckage location Jun 30, 2010 (http://www.bea.aero/en/enquetes/flight.af.447/phase3.search.zone.determination.working.group.report.pdf)

(e) Wreckage search analysis Jan 20, 2011 (http://www.bea.aero/fr/enquetes/vol.af.447/metron.search.analysis.pdf)

(f) Briefing and associated update May 27, 2011
- Briefing (http://www.bea.aero/fr/enquetes/vol.af.447/info27mai2011.fr.php) - update French (http://www.bea.aero/fr/enquetes/vol.af.447/point.enquete.af447.27mai2011.fr.pdf)
- Briefing (http://www.bea.aero/fr/enquetes/vol.af.447/info27mai2011.en.php) - update English (http://www.bea.aero/fr/enquetes/vol.af.447/point.enquete.af447.27mai2011.en.pdf)
- Briefing (http://www.bea.aero/fr/enquetes/vol.af.447/info27mai2011.de.php) - update German (http://www.bea.aero/fr/enquetes/vol.af.447/point.enquete.af447.27mai2011.de.pdf)
- Briefing (http://www.bea.aero/fr/enquetes/vol.af.447/info27mai2011.br.php) - update Portugese (http://www.bea.aero/fr/enquetes/vol.af.447/point.enquete.af447.27mai2011.br.pdf)

(g) Interim Report No. 3 July 2011 - French (http://www.bea.aero/docspa/2009/f-cp090601e3/pdf/f-cp090601e3.pdf), English (http://www.bea.aero/docspa/2009/f-cp090601e3.en/pdf/f-cp090601e3.en.pdf)

Miscellaneous pertinent links -

(a) Airbus Operations Golden Rules (http://www.airbus.com/fileadmin/media_gallery/files/safety_library_items/AirbusSafetyLib_-FLT_OPS-SOP-SEQ03.pdf)
(b) ALPA FBW Primer (http://cf.alpa.org/internet/alp/2000/febfbw.htm)
(c) C* and Civil Transports - Cranfield (https://dspace.lib.cranfield.ac.uk/bitstream/1826/186/2/coareport9303.pdf)
(d) Longitudinal Flight Control Design - RAeS (http://www.raes.org.uk/pdfs/2989.pdf)
(e) Longitudinal Stability: Effect of High Altitude and CG - Boeing (http://boeing.com/commercial/aeromagazine/aero_02/textonly/fo01txt.html)
(f) pitot static system performance - USN (Pax River) FTM (http://www.aviation.org.uk/docs/flighttest.navair.navy.milunrestricted-FTM108/c2.pdf)
(g) The Problem of Automation: Inappropriate Feedback and Interaction, Not Over-Automation. Donald A. Norman UCSD (http://www.jnd.org/dn.mss/Norman-overautomation.pdf)
(h) Upset Recovery - 16MB zip file (http://www.mediafire.com/?jrkvp2ysl7aea25)
(i) Ironies of Automation. Lisanne Bainbridge UCL (http://www.bainbrdg.demon.co.uk/Papers/Ironies.html)
(j) Cognitive Capability of Humans. Christopher Wickens Uni Illinois (http://www.humanfactors.uiuc.edu/Reports&PapersPDFs/chapters/Wickens_Durso%20Aviation.PDF)
(k) Trust in Automation: Designing for Appropriate Reliance John D. Lee, Katrina A. See; Human Factors, Vol. 46, 2004 (http://www.questia.com/googleScholar.qst;jsessionid=LHmZGvvpc1T1RT2pThDgGpvfwpMvh6f TTBPVC4hD8Tpg8J4LdQZy!-290722064?docId=5008765429)
(l) Training for New Technology. John Bent - Cathay Neil Krey's CRM site (http://www.crm-devel.org/resources/paper/bent.htm)


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[4dogs]

Does anyone have a time (UTC) for the scheduled release of the report?

[john_tullamarine]

The BEA site suggests (http://www.bea.aero/en/enquetes/flight.af.447/com18juin2012.en.php) early afternoon.

However, I've had a long week so it's off to bed for me, I'm afraid.

[jcjeant]

Hi,

Keep monitoring this page :)
FLIGHT AF 447 (http://www.bea.aero/en/enquetes/flight.af.447/flight.af.447.php)
A media presentation will take place at the Musée de l'Air et de l'Espace in Le Bourget at 2.30 pm
So it's in one hour from now (local time)
Dunno if the report will be posted same time

[Machinbird]

Quote:
Originally Posted by Machinbird
BEA has not yet provided spoiler and aileron position data, so analysis of the causal aspect is not yet possible.

Carried over from Thread No. 8
Well, if it doesn't make it to the final report, you can always use page 112 of interim 3: lateral DFDR parameters. Ailerons and spoilers staunchly followed the sidesticks, their periods of fluttering like mad were occasionally interrupted by full LWD deflection with not much apparent effect, as expected in stall.
Clandestino, look at the data you suggested and blow it up until you can see the shape of the curves. You cannot using that data. Not enough pixels to see anything.
Just a bunch of blocks. I do not call that disclosure of the data.

[pcoletti]

Which is 12.30 GMT

[Clandestino]

Due roughness, one can't use graphs to derive control rates but positions can clearly be seen.

Would you please extend your roll/roll rate graph a minute into the future? Graphs on pages 30 and 31 are smooth & high-res, you can't object to that.

[Flying Wild]

briefing live with on the fly translation on the BBC: BBC News - Air France 2009 Paris-Rio crash final report released (http://www.bbc.co.uk/news/world-europe-18720915)

[fireblade2000uk]

The report is "expected to say" so nothing new as of yet!

[frac]

Other Live Stream.

Live BFMTV (http://www.bfmtv.com/direct/)

[4dogs]

Thanks JT,

I did have a quick look at that page but dismissed the Press Release as being from 2009...duh! :O

[DozyWannabe]

So in terms of changes to aircraft systems:

FDs need to be changed in terms of their appearance in marginal systems behaviour
Stall Warning needs to be overhauled including dedicated visual channel and to operate in cases of low speed
Feedback in terms of systems failures (presumably ECAM) needs to be clarified and improved

Some certification changes will also be recommended.

So - any claims of a whitewash putting the finger solely on pilot error from this point onwards are clearly false.

[UPDATE - Claims final report will include computed FD commands, which should please some who wanted that information...]

[roulishollandais]

Hello pcoletti,
... Just to be accurate :
14h30 local time in France (metropole=Paris) is
12h30 UT and also
00h30 GMT (reference for astronomy : the day starts at noon the sun passing the Greenwich meridian at 00h00 true solar time # 00h04m40s GMT 5.july2012) . (International convention)

... I have noting against UK !

roulishollandais (enjoying with sundials...):p

[Heathrow Harry]

from Beeb

Technical failure and human error led to the loss of an Air France flight over the Atlantic in June 2009 and the deaths of 228 people, according to the final report into the crash.

The report by France's aviation authority, the BEA, says the crew did not react correctly after the Airbus A330 had technical failures.

It disappeared from radars while en route to Paris from Rio de Janeiro.

It took nearly two years for the flight recorders to be found.

Thursday's findings are in line with a preliminary report released last year by the BEA.

That report said the pilots did not follow the proper procedures after the aircraft's speed sensors - called Pitot tubes - failed during a storm two hours after take-off.

The plane stalled and lost altitude, the report said, and the captain did not retake control of the plane after taking a rest.

One of the mistakes of the crew, according to investigators, was to point the nose of the aircraft upwards, after it stalled, instead of down.
Manslaughter claims
Investigators have found fault with both Airbus and Air France, sparking a row between the two firms over their accountability for the crash.

Both companies are under investigation by French magistrates for alleged manslaughter.

A separate judicial report will be released next week. This is also expected to echo Thursday's report by the BEA, the French news agency AFP says.

Since the crash, Air France has replaced the speed sensors on its fleet of Airbus jets - made by the French firm Thales - with a newer model.

The wreckage of the plane was discovered after a long search of 10,000 sq km (3,860 sq miles) of sea floor.

After 23 months of searching, robot submarines finally found the flight "black box" recorders last year.

[Peter H]

roulishollandais
... Just to be accurate :
14h30 local time in France (metropole=Paris) is
12h30 UT and also
00h30 GMT

Rather a surprise to us brits, who are told that they use GMT half the year.

More specifically, from wikipedia
Historically the term GMT has been used with two different conventions, sometimes numbering hours starting at midnight
and sometimes starting at noon. The more specific terms UT and UTC do not share this ambiguity, always referring to
midnight as zero hours. Astronomers preferred the latter GMT convention in order to simplify their observational data
so that each entire night was logged under a single calendar date.

[konradeck]

Good update on Simon's site: Crash: Air France A332 over Atlantic on Jun 1st 2009, aircraft entered high altitude stall and impacted ocean (http://avherald.com/h?article=41a81ef1/0080&opt=0)

New thread compared to previous interim reports, which partially explains crew's behavior is that Flight Director was constantly suggesting the crew to raise aircraft's nose.

[pcoletti]

... here:

http://www.bea.aero/docspa/2009/f-cp090601.en/pdf/f-cp090601.en.pdf

[noske]

Aviation Herald already has a summary of the presentation and the Q&A session. Most remarkable to me:


The flight directors provided indications to increase the nose up attitude.
During the final 4 minutes of flight the flight directors disappeared and reappeared multiple times.
The flight directors were NOT disengaged as they SHOULD have been.
The modus of flight director operation is being further looked into.

[alph2z]

Final report (26 MB, Not finished downloading)

http://www.bea.aero/docspa/2009/f-cp090601.en/pdf/f-cp090601.en.pdf

Web page for download mirrors and french
Rapport final (http://www.bea.aero/fr/enquetes/vol.af.447/rapport.final.fr.php)

Enjoy ....
.

[DozyWannabe]

The flight directors provided indications to increase the nose up attitude.


Not quite accurate. The presentation stated that the FDs indicated "slight nose-up" (presumably 5 degrees) at the point of Stall Warning activation. If they were indeed indicating 5 degrees then the FDs would have been ordering an initial small nose-up command followed by maintaining the 5 degree attitude. What was in fact commanded by the PF was a nose-up to almost 15 degrees within five seconds - way in excess of what the FD was displaying.

[jcjeant]

Hi,

Orangefreak
It's the final report !
Date publication : July (Juillet) 2012
And a lot of annex
Going for a long reading now :)

[llagonne66]

Including the appendixes it goes up to 43.5 megabytes ... so anybody posting a comment, let's say in the next 6 hours, won't be very serious ...

[PJ2]

A procedural question from a non-pilot.

I assume that a stall warning requires a prompt response, while an event such as UAS requires a more considered response [and resort to a checklist].

If so, shouldn't the initial response to a stall warning be a memory item? With any caveats about ignoring stall warnings being part of that memory item.

From Day One of flight training, recognition of the stall in the airplane one is training in is a high priority item. The "Approach to the Stall" is a common exercise when transitioning to new aircraft types. The "approach to stall" is not the actual stall, either in the simulator or the aircraft as the case may be. No one stalls airplanes in transition or type-rating courses. It is the recognition of the impending stall that is taught.

Regulatory bodies may or may not require that the approach-to-stall exercise be part of recurrent training on one's current aircraft. In Canada, current regulations do not require the approach to the stall exercise in fly-by-wire aircraft after the initial type-rating is complete. One may go years without seeing the exercise again unless it is informally inserted into the sim exercise by a keen instructor. Usually sim time is so compressed with required exercises that such things as manual flying and so on aren't usually done.

On the memorized aspect of the stall response, you're right - the stall warning requires an immediate response and yes, the aircraft-specific response would be memorized - but it's memorized the same sense as one might "memorize", say, the skid-response in a car...it's not just "memorized mechanically" but should be "visceral" - ie, instant and automatic.

Two reasons why this may not be the current state of affairs are, 1) aircraft today are so reliable and so well-designed that getting oneself into such a corner is an extremely rare event, and 2) because of such reliability, the "approach to the stall" exercise has been de-emphasized (and not just for Airbus aircraft) so pilots today who may not have exerienced anything but a high degree of automation may not, (emphasis here) have the same appreciation of the danger of the stall as the previous group who grew up on cable-and-pulley aircraft that could and did stall. A sense that one's airplane "cannot stall" because of automated protections is completely foreign to me and to an entire generation of guys who are now retired/retiring but I wonder in what way the stall is currently perceived as a serious and ever-present threat if one loses airspeed? There have been at least a dozen accidents in the last eight or so years as a result of stalling one's transport aircraft. That's unusual and I think a trend.

The avoidance of the stall would be/should be innate as once again, avoiding a stall is absolutely fundamental to flying any airplane. Type-specific responses to the stall warning, (which indicates an approach to stall, and not the fact that the airplane is stalled) would be part of the FCOM for the aircraft. Typically, such responses used to focus on a minimum loss of altitude first, while "powering out" of the condition. At high altitude, the guidance was that the pitch attitude may have to be slightly below the horizon for recovery. TOGA (take off/go around) thrust was always applied as part of the memorized drill.

Since AF447, this response has been re-visited and, I think, far more intelligently designed due to the recognition that the stall is not an airspeed problem, it is an AoA [angle of attack] problem, and the first reaction now is to reduce the wing's AoA to unstall the wing, then recover with power. Increasing thrust with under-slung engines tends to pitch the aircraft up, countering the required response, so adding thrust is a secondary response now. These responses will be memorized and, I suspect, practised far more frequently now.

The sections of the FCOM I cited in the previous post would be those seen on the ECAM and would be accomplished after all memory items were completed by the crew.

The standard response has always been to respect the stall warning, period. The one caution could be confusing to someone who hadn't received thorough training but the two should never be confused to the extent that doubt is produced as to what to do if a stall warning occurs.

I hope this helps.

[sensor_validation]

Including the appendixes it goes up to 43.5 megabytes ... so anybody posting a comment, let's say in the next 6 hours, won't be very serious ...

It's a very well written report, only typo I noticed in the English version was on bottom of P151 "mark range" should be "Mach range".

Sad, so sad.

[syseng68k]

Have been lurking for some time, waiting for the final report,
but one thing that stood out for me on initial scan was the
paragraph on the horizontal stabiliser, p218, 5.3.1.2, where
the concept of "pitch runaway" is discussed.

I'm sure that this must have been discussed at length elsewhere
in the topic, but would have assumed that any sensible system
design would inhibit ap engagement, or any autoflight function,
unless airspeeds are known good. Otherwise, feedback loop
with no null possible...

[Fox3WheresMyBanana]

Quoth page 185 of the report

Current training practices do not fill the gap left by the non-existence of manual flying at high altitude, or the lack of experience on conventional aeroplanes. Furthermore, they limit the pilots’ abilities to acquire or maintain basic airmanship skills.

In short, training's too short.

..and do Air France's crew training changes (p215) do anything about this? No

[RR_NDB]

but would have assumed that any sensible system
design would inhibit ap engagement, or any autoflight function,
unless airspeeds are known good. (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-2.html#post7279598)

A case for GIGO, "as per design"?

[Clandestino]

but one thing that stood out for me on initial scan was the
paragraph on the horizontal stabiliser, p218, 5.3.1.2, where
the concept of "pitch runaway" is discussed.
Errr... discussed was the "pitch runaway" that could result from engaging the autopilot that would follow the false air data, not "stabilizer runaway".

I'm sure that this must have been discussed at length elsewhere
in the topic, but would have assumed that any sensible system
design would inhibit ap engagement, or any autoflight function,
unless airspeeds are known good.Problem is that it is easy to use computer to detect failed airspeed indicator but the system that can detect unreliable airspeed needs to be truly intelligent. No replacement for human pilot there is currently available.

[ECAM_Actions]

A design flaw is the inhibition of the stall warning based on airspeed, instead of the weight-on-wheel switches. If the WoW switches are saying it is flying, then the aircraft must be flying, right??? Is this too obvious??

To invalidate the stall warning on airspeed alone is stupid.

There are three parameters:

* WoW switches (FLYING)
* Airspeed (STALL, though invalid)
* AoA (STALL)

3 out of 3 says it is stalled, even though the airspeed is invalid in this case.

If any of the other two parameters were not stalled:

* WoW switches (FLYING)
* Airspeed (STALL, though invalid)
* AoA (FLYING)

with the speed being unreliable (and the system knowing this), chances are it is flying! This of course ignores the fact there are MULTIPLE AoA vanes sensing a stall condition.

[RR_NDB]

Problem is that it is easy to use computer to detect failed airspeed indicator but the system that can detect unreliable airspeed needs to be truly intelligent. (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-2.html#post7279647)

Simple engineering task. Problem is: Designers mut be ALWAYS, "truly intelligent."

No replacement for human pilot there is currently available.

And this unavailability is AN ABSURD! It is VERY EASY, REPEAT: VERY EASY to process the information in order to HELP THE CREW ALLOWING TO UNDERSTAND THE ISSUE, IMMEDIATELY! BEFORE ANY CONTAMINATION OF AVIONICS WITH GARBAGE!

To put (and maintain) in crew shoulders the responsibility to do the diagnosis (as Airbus SAS paper in UAS issue put) is IMO a GRAVE ERROR.

[RR_NDB]

A design flaw is the inhibition of the stall warning based on airspeed, instead of the weight-on-wheel switches. If the WoW switches are saying it is flying, then the aircraft must be flying, right??? Is this too obvious?? (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-2.html#post7279662)

K.I.S.S. or K.I.C.S.? design approach?

K.I.C.S. stands for: Keep It Complex Stupid

[grity]

s.202: A crew can be faced with an unexpected situation leading to a momentary but profound loss of comprehension. If, in this case, the supposed capacity for initial mastery and then diagnosis is lost, the safety model is then in “common failure mode”.


what did this mean: "common failure mode" ???
is it accepted in the flying comunity to loose the control in this case?

[aguadalte]

I was hopping to see at least one recommendation regarding PF SS inputs to be shown on PNF PFD in the sequence of this statement on the final report:
(...) It would also seem unlikely that the PNF could have determined the PF’s flight path stabilisation targets. It is worth noting that the inputs applied to a sidestick by one pilot cannot be observed easily by the other one and that the conditions of a nightflight in IMC make it more difficult to monitor aeroplane attitudes (pitch attitude in particular). (...)
I guess that would be an "evidence" of Airbus Industrie's misconception of the system...

[jcjeant]

This is the reaction of Air France ..
It's sad that Air France stay on his position and have not understand the message convoyed by the BEA in the final report .... :*

Communiqués de presse (http://alphasite.airfrance.com/fr/s01/communiques-de-presse/#communique3422)

Google*Traduction (http://translate.google.be/translate?sl=fr&tl=en&js=n&prev=_t&hl=fr&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Falphasite.airfrance.com%2Ffr%2Fs01%2Fcommuniq ues-de-presse%2F%23communique3422&act=url)


In its analysis and conclusions, the BEA said it's a chain and a combination of factors - technical and human - that led to the loss of the aircraft in just over four minutes. He confirmed that the crew was trained and qualified in accordance with the regulations and the aircraft systems have responded in accordance with their design and certification criteria.
The BEA report describes a crew that is based on information provided by the instruments and aircraft systems, and behavior of the aircraft as it was visible in the cockpit instrument readings, triggering alarms and shutdowns, noises aerodynamic vibrations of the device, etc.. The reading was made he was not permitted to apply the appropriate actions. In this environment degraded steering, crew, gathering the expertise of the captain and officers of the two pilots, remained engaged in the conduct of the flight until the last minute.
Air France pays tribute to their courage and determination in these extreme conditions.
And the reaction of Airbus:
AF447 Statement*| Airbus, a leading aircraft manufacturer (http://www.airbus.com/presscentre/hot-topics/statement/)

The publication of the BEA’s final report now provides the opportunity to further work on the lessons learned from this tragedy and measures to be applied to avoid the recurrence of such an accident. Without waiting for this final report, Airbus has already started working at industry level to further reinforce the robustness of pitot probes requirements and actively supports related activities.

[Fox3WheresMyBanana]

I doubt that at any point in these pilots' training have they been placed in a situation where their corrective actions did not work, nor have they been trained to deal with it. I imagine this is what is meant by common failure mode.
Even after 2 minutes, if they'd started from square one, they could probably still have saved the aircraft.

This doesn't have to be as hard as my RAF Instructor who gave me the aircraft with a toppled horizon in a spin for an IF Unusual Attitude that was supposed to be full panel. But this, and other similar tricks (once is not enough), taught me to recognise when plan A wasn't working, and how to start again from scratch.
It would probably help in the civilian world if these things weren't graded either.

[Clandestino]

To invalidate the stall warning on airspeed alone is stupid.

If the CAS measurements for the three ADR are lower than 60 kt, the angle of attack values of the three ADR are invalid and the stall warning is then inoperative. This results from a logic stating that the airflow must be sufficient to ensure a valid measurement by the angle of attack sensors, especially to prevent spurious warnings.Plugging WoW into stall warning computer would make it more complicated, adding one more point of possible failure. Is 60 kt really too low cut-out for widebody?

And this unavailability is AN ABSURD! It is VERY EASY, (REPEAT: VERY EASY) to process the information in order to HELP THE CREW ALLOWING TO UNDERSTAND THE ISSUE, IMMEDIATELY!
BEFORE ANY CONTAMINATION OF AVIONICS WITH GARBAGE!It is not easy in this universe where computers haven't moved from algorithms that can be broken down to simple IF...THEN; it is impossible. There are lines of code helping the FBW computers reject false air data if one computer doesn't tell the same story as the other two (which has shown its dark side at Perpignan) or there is such a rapid change in parameters that it's physically impossible but it takes intelligence to recognize if the combination of airspeed and normal acceleration is incompatible with sustained flight and yet aeroplane is flying, then there must be something wrong with the indications.

To put (and maintain) in crew shoulders the responsibility to do the diagnosis (as Airbus SAS paper in UAS issue put) is IMO a GRAVE ERROR.
Every modern passenger transport aeroplane experiencing unreliable air data will throw a host of undue warnings. Warning computers are not intelligent and are not supposed to be, they just monitor parameters and cry out when pre-programed thresholds are exceeded. Have a look what happened to Aeroperu (http://www.skybrary.aero/bookshelf/books/1719.pdf) or Birgenair (http://flightsafety.org/ap/ap_oct99.pdf) when air data become unreliable. They were 757s. Not made in Toulouse. It is all very nice for PPRuNers or investigation boards to ask for better UAS detection and resolution systems but without some creative genius coming with the idea of how they should be made, we won't get far.

is it accepted in the flying comunity to loose the control in this case? Seemingly everything is possible with de-structured crew. Love that postmodernist terminology in the accident reports... not.

I guess that would be an "evidence" of Airbus Industrie's misconception of the system... Too bad this "evidence" did not make it into recommendations. Conspiracy? Recognition that non-interconnected sticks did indeed prevent CM1 from recognizing that all the mess was mainly CM2 induced is so low down the causality chain to be significant?

[ECAM_Actions]

Is 60 kt really too low cut-out for widebody?It would seem not slow enough. :ugh:

All the ADCs need to know is whether all the airspeeds are within a certin limit of each other. They were not, and the system alarmed/downgraded as it was supposed to.

Where the problem arose was in the fact that the crew were overwhelmed by the automation, instead of asking why the airspeed was indicating 60 kts and the stall warning intermittent.

Regardless of any computers, I hope people haven't already forgotten that the by now very low airspeed was showing as such on the PFD and ISIS?

Regardless of what people fly - SIT and THINK when an alert first appears. Do a sanity check - are basic flight parameters nominal for the phase of flight?

[RR_NDB]

it is impossible. (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-2.html#post7279785)

It is POSSIBLE AND EASY! (Simple engineering solution)*

(*) Will brief on that important issue in Man machine interface Thread


Not made in Toulouse. (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-2.html#post7279785)

I am an EE with Safety interests. A x B is not my agenda.

without some creative genius coming with the idea of how they should be made, we won't get far.

This is responsibility of R&D of A, B, E, etc.

Will brief on that important issue in Man machine interface Thread

[jcjeant]

This is an amazing "pearl" in this report:

Page 206
4.2.1 Recommendations on Operations
Training for Manual Aircraft Handling
Examination of their last training records and check rides
made it clear that the copilots had not been trained for manual aeroplane handling
of approach to stall and stall recovery at high altitude.

They can't fly manually at high altitude .. :}
When you know that most of the flight is in high altitude .. this gives chilling (no pun intended)
If this is not a finger pointed to AF .. I don't know what is this ...

[Bill Macgillivray]

I suspect (and raise the anti-flack shields!), that a tremendous amount of basic flying skills are no longer required to be taught. Flying an aircraft safely has now moved to a stage where (generally) you are monitoring a computor/auto-pilot system and the basic skills do not appear "valid", we are into the "what is it doing now" syndrome. FATAL!! (I have only recently given up instructing and not just on basic aircraft!). Not all of the old skills should be forgotten! It could/has proved fatal!

[oldchina]

Agree.

As I said before, no-one thinks it odd that it's legal (certified) to have an autopilot that under certain conditions in cruise gives back control of the plane to the pilots. The same conditions in which the pilots are not trained to fly the plane.

[RR_NDB]

Hi,

Bill Macgillivray:

Not all of the old skills should be forgotten! (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-2.html#post7279937)

A basic (and old) mandatory skill is aviate your plane. AoA is ESSENTIAL (to fly non rotary wing a/c).

This VERY BASIC "detail" was simply not "respected".

:{

[GarageYears]

This is a chilling read, but I think brings the lack of understanding of what the aircraft was doing into sharp focus. From everything I can tell the whole verbiage is there. It is not a happy read at all.

[Turbine D]

I thought it was interesting relative to the point that visual cues take precedent in the human mind over aural cues in time of stressful situations.

Clandestino quote: It is all very nice for PPRuNers or investigation boards to ask for better UAS detection and resolution systems but without some creative genius coming with the idea of how they should be made, we won't get far.

In the WSJ today: For next year, the company (Boeing) is poised to test an array of modifications on one of its 787 Dreamliner models, according to industry and company officials. Boeing flight tests of the 787 next year are likely to include a new cockpit-safety feature aimed at helping pilots recover from stalls or other unusual maneuvers that could cause them to lose control of the aircraft, officials said.

The proposed system for the 787 provides instant and prominent visual cues - consisting of brightly colored arrows popping up on cockpit displays - to help pilots recover from flight upsets or other extreme situations that may prompt them to be confused about a plane's automation or trajectory.

Developed by Honeywell International Inc. in conjunction with Boeing, the proposed warnings are intended to advise pilots how to manipulate a plane's controls in an emergency by giving the pilots clear-cut directions that are not available on current Boeing models. If Boeing offers such enhancements, airlines are likely to embrace them because the system is projected to require only relatively inexpensive software upgrades to existing flight-control hardware and cockpit displays.

The article talks about more improvements to be tested on a 737 as well as changes to GE and or CFMI engines that will improve upon fuel consumption efficiency.

[jcjeant]

The proposed system for the 787 provides instant and prominent visual cues - consisting of brightly colored arrows popping up on cockpit displays - to help pilots recover from flight upsets or other extreme situations that may prompt them to be confused about a plane's automation or trajectory.

To note that this kind of cues are already implemented in many video games :ok:
Of course .. it's more easy to implement those in a video game instead a airliner :)
Would be the future of flying be a kind of video game :confused:

[RR_NDB]

I thought it was interesting relative to the point that visual cues take precedent in the human mind over aural cues in time of stressful situations. (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-3.html#post7280012)

Great news coming from R&D. With a powerful "man-machine interface tool" to crews "near the edge". (as such was the case in AF447 before put a/c in full stall)

Thanks for very important information at a "right moment" for us here. BEA "final report day".

[ECAM_Actions]

I think Boeing missed the point. If they need school-kid directions because the pilots are overwhelmed with data, maybe they'd be better addressing the cause rather than finding yet another piece of data to flash at them?

Besides - the FD bars on the AF jet were commanding a CLIMB, so how are Boeing's magic arrows going to react any differently under the same situation?

How about a declutter function - HIDE all but the MOST important data, and silence alarms? Blank screens if you have to.

[RR_NDB]

I think Boeing missed the point. If they need school-kid directions because the pilots are overwhelmed with data, maybe they'd be better addressing the cause rather than finding yet another piece of data to flash at them?

Besides - the FD bars on the AF jet were commanding a CLIMB, so how are Boeing's magic arrows going to react any differently under the same situation?

How about a declutter function - HIDE all but the MOST important data, and silence alarms? Blank screens if you have to. (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-3.html#post7280060)

A well developed SW together Air Speed DSP could improve easily the current situation.

As far i can imagine, the idea of the info TD bring us is to simplify crew work in abnormalities.

Your 3 questions are important. We need to wait.

[Turbine D]

Hi jcjeant,
Would be the future of flying be a kind of video game :confused:

Yup, only a matter of time as the pace of technology continues on its rapid pace. Maybe not in our lifetime, but, if your great-grandson or great-granddaughter aspires to be a pilot, this is a preview of the future. There is already a shortage of these "pilots"....

Drone Control Room ....Must see ! - YouTube

[Turbine D]

RR_NDB,

Re: Great News

I though you would like this!

[DozyWannabe]

Besides - the FD bars on the AF jet were commanding a CLIMB...

5 degrees nose-up at FL350 or thereabouts - which is what the flight directors showed at the time of SW - is *not* a climb at cruise thrust.

[justthisonce]

Hello All, I am a newbie and an airline enthusiast. I used to work for an airline but in their IT so I don't claim any knowledge of powered (or unpowered) flight.

I have been keeping track of this case ever since it happened.

I saw this in the news today and signed up on this forum just to ask this one question. I read the cockpit recorder transcript here.

Air France 447 Flight-Data Recorder Transcript - What Really Happened Aboard Air France 447 - Popular Mechanics (http://www.popularmechanics.com/technology/aviation/crashes/what-really-happened-aboard-air-france-447-6611877)

What ruled out the possibility that the Bonin guy was not suicidal?

This is a reasonable question, given that several crashes over the years have had such implications, so I'll let it stand.

However, please let's not venture into conspiracist realms .. JT

[mm43]

But the aeroplane had not encountered, before or during the accident, an exceptional meteorological situation from the point of view of phenomena that are traditionally avoided in stormy environments (turbulence, lightning, icing).Hope that puts an end to the "thunderstorm" brigade. It is deemed to have been "nothing exceptional", though the wise decision would have been to avoid it.

....the presence of flight envelope protections makes neutral longitudinal static stability acceptable. ....It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall.A bit of a "soft" excuse when you've already managed to dump most of the kinetic energy available.

Machinbird;

Your PIO roll proposition appears to have been confirmed.

[jcjeant]

In the CVR transcript I notice some PNC call during event ..
2H10.55
2H10.59
2H11.02
2H11.24
2H11.30
It may be that PNC was concerned that something was abnormal ....

[MountainBear]

It's a very well written report, only typo I noticed in the English version was on bottom of P151 "mark range" should be "Mach range". Well, I didn't even make it past the first two pages before discovering this gem:


As accurate as the translation may be, the original text in French is the work or reference

back to the actual report...

[DozyWannabe]

What ruled out the possibility that the Bonin guy was not suicidal?

This is a reasonable question, given that several crashes over the years have had such implications, so I'll let it stand.

However, please let's not venture into conspiracist realms .. JT

Will do JT.

The CVR transcript looks all wrong for a deliberate attempt to sabotage the flight. Bonin's words reflect a mindset of being gradually overwhelmed by a problem, and increasing anxiety as the situation worsens. In every case of suicide/homicide in aviation I know of, the perpetrator has never betrayed anxiety - instead becoming task-focused and shutting out all extraneous human interaction.

Also his wife was on board - they were both returning from a holiday to Brazil which if anything seemed to lighten Bonin's mood based on second-hand evidence.

Everything else aside, all evidence indicates a pilot who tragically got out of his depth and was spooked enough to try the wrong thing over and over.

[Machinbird]

Machinbird;

Your PIO roll proposition appears to have been confirmed.
Thank you for the heads up.:) Haven't yet had the time to read the report.

[MountainBear]

This is a chilling read, but I think brings the lack of understanding of what the aircraft was doing into sharp focus. From everything I can tell the whole verbiage is there. It is not a happy read at all.I've read through the report and the appendix (just one time) and honestly I'm none the wiser than I was after the report a year ago.

Fundamentally, there are three pilots flying one of the best aircraft in the world and they put it in the water. What I do not comprehend is why they did not comprehend.

All the final report offers is speculation.

(!) we’re going to crash
This can’t be trueIt was true and it's about the only thing I am confidant of.

[gums]

I can't seem to find a download with all the appendices.

[Irish Steve]

a tremendous amount of basic flying skills are no longer required to be taught.

It's worse than that. A tremendous amount is deemed either unneccessary or too expensive by the bean counters. Some operators insist the automation is used to get the absolute cheapest operation of the aircraft, and the bean counters do statistical analysis on the cost of training for some scenarios against the cost of the incident should it happen.

This is only the tip of the iceberg, and this incident is Airbus' Titanic, they have some serious soul searching to do in many areas.

[LandIT]

gums

Try the annexes au rapport final area at the bea site...
Rapport final (http://www.bea.aero/fr/enquetes/vol.af.447/rapport.final.fr.php)

[RR_NDB]

Hi,

MountainBear:

flying one of the best aircraft in the world (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-3.html#post72)

:confused:

What I do not comprehend is why they did not comprehend.

:confused:

A good machine is transparent. You ALWAYS control it. Through a constant comprehension.

:ok: ???

[Mr Optimistic]

First off congratulations to the French institutions for their endeavours in retrieving the evidence and the subsequent analysis. Irrespective of sidesticks and yokes, aoa indicators , huds or other technical options, the fate of this aircraft was a consequence of the actions of 3 human beings over a 4 minute interval in their otherwise peaceful lives. No machine can be perfect so its an equation of competence, training, knowledge and readiness.

[john_tullamarine]

a tremendous amount of basic flying skills are no longer required to be taught.

.. while the automatics are working ... which is why my old slide rule still sits in the bottom drawer (not that I would like to have to demonstrate my residual competence on the beast at a moment's notice).

Through a constant comprehension.

.. and apprehension ...

No machine can be perfect so its an equation of competence, training, knowledge and readiness.

.. not a bad summation.

Clearly there has to be a point beyond which diminishing returns makes additional training investment a moot point and not rationally justifiable .. however, establishing just where that point might reside depends a lot on what coloured glasses the viewer is using.

I have noted, in a variety of test circumstances, that a characteristic of the experienced pilot is a tenacious devotion to achieving the goal. This admirable trait is defeated if we don't give him/her a fighting last ditch chance to save the day when all the gee-whizz stuff takes a holiday.

[gums]

Thanks IT, got the full CVR appendix and others.

As many here expected, a combination of training, CRM, and the control law reversions/displays all played a role in the tragedy.

I shall cut the crew a bit of slack. Not a helluva lot, but I have to look at their experience and previous training. And then there's the belief by a few that the "system" will take care of them.

I shall not cut the FBW mechanization a single atom of slack, nor the associated lack of clear displays to the crew as to what they had available ( so-called protections) nor basic steering guidance for the crew that had thousands of hours using the AP and not actually flying the jet. Don't mean to be harsh, but it's what I feel.

This will be a landmark accident report in terms of recommendations and findings and.....

My prayers are that we shall see improved training, improved CRM and maybe some changes in the reversion sequences of the FBW systems when the air data sensors fail.

[Organfreak]

Well done, Gums. (We're all bz reading...)

:ooh:

[RatherBeFlying]

I read the final report and much of what was discussed in these pages is there.

My only nit is that there is no discussion that the crew seems not to have been aware of or concerned about altitude until the 10,000s digit dropped off the altitude display, i.e. went from 5 digits to 4:

2 h 13 min 31,7 PF (*) au niveau cent -- FL 100
2 h 14 min 07,3
PNF je cabre PF ben il faudrait on est à quatre mille pieds
PNF I'm pitching up PF Well we need to we are at four thousand feet

and while recovery from 4000' would have been unlikely even then they did not think of stall.

Earlier on we have PF:

2 h 11 min 58,2 Je… j’ai, le problème
2 h 11 min 58,6 c’est que j’ai plus de vario là

who feels he has lost VS indication.

Perhaps if the VS pointer was red, thick and flashing it may have clued in the crew in time.

[mm43]

5.1.2 Modifications to reference systems


Documentation

Changeover to manufacturer’s documentation in English. The B777 division will be the first to be thus equipped in October 2012.



An interesting decision, but confirming a common language policy and easy comparison with similar documentation worldwide. IMO to be applauded.:D

[VGCM66]

I keep reading the "• Appendix 1 CVR Transcript" because I think it does speak volumes about the mind set of the crew. I still think that humans factors were the main cause of this crash. There is a lot of paper work that contributes to diverge the attention of the crew from flying the airplane. CRM was no where to be found that night. How do you get a Cessna pilots license without knowing what Stall means? Who cares about over speed when altitude keeps dropping? 25,000 feet (actually 28,000) were casually lost at level 100 and keeping the wings level was more important? ...? :ugh:

Anyways, it is over for now until the next one.

[FullWings]

I still think that humans factors were the main cause of this crash.
Yes, and just humans. The sad thing is, if at the first sign of anything going wrong, they'd all trooped out of the cockpit, sat down, had a coffee and a croissant and come back to their seats five minutes later, they'd probably still be alive to talk about it.

[Lyman]

Something in the CVR transcript I have not seen til now... Very late in the text.

2:13:53.0. Page 31 CVR transcript (English)

Captain: "So wait...AP off". (sound of selector button....)

Que?

[A33Zab]

UAS IMMEDIATE DETECTION

Quote:
it is impossible. (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-2.html#post7279785)
It is POSSIBLE AND EASY! (Simple engineering solution)*

(*) Will brief on that important issue in Man machine interface Thread


I would suggest you apply for a job within AIB.

IMO the most sensible solution:

http://i474.photobucket.com/albums/rr101/Zab999/Vsyn.jpg



To not understand - the AIRBII Man machine - and in particulair the displays, Ecam messages etc. for NON Airbus pilots is excusable.....but NOT TO Airbus pilots.


3.2 Causes of the Accident:
------




Thus, the accident resulted from the following succession of events:

Temporary inconsistency between the airspeed measurements, likely following the obstruction of the Pitot probes by ice crystals that, in particular, caused the autopilot disconnection and the reconfiguration to alternate law;
Inappropriate control inputs that destabilized the flight path;
The lack of any link by the crew between the loss of indicated speeds called out and the appropriate procedure;
The late identification by the PNF of the deviation from the flight path and the insufficient correction applied by the PF;
The crew not identifying the approach to stall, their lack of immediate response and the exit from the flight envelope;
The crew’s failure to diagnose the stall situation and consequently a lack of inputs that would have made it possible to recover from it.

[philip2412]

I`m not apilot by far.But I`ve read a few a.i. reports, so i think i know a bit more than the common man on the street.

sp pls somebod answer my question.Would`nt a simple spirit level (water gauge) in the cp have heled ?
There a so many technical revolutions today ,flying to the stars.why is it not possible to have a display in the cp showing the attitude of the ac from outside (head up-tail down) with a big blinking red arrow under the fuselage pointing downward,combined with an alarm and a voice,saying "correct your attitude" which can`t be cancelled until this has been done ?

[jcjeant]

Something in the CVR transcript I have not seen til now... Very late in the text.

2:13:53.0. Page 31 CVR transcript (English)

Captain: "So wait...AP off". (sound of selector button....)

Que?

The AP is off from the beginning of the event
I suppose the captain moved the AP selector to OFF (useless command IMHO)

[sensor_validation]

Quote:
Is 60 kt really too low cut-out for widebody?

It would seem not slow enough. :ugh

As discussed at length before it is 60kt 'apparent airspeed' derived from pitot tubes which will all be significantly under-reading at high angle of attack. I'm sure someone can post a calculated trace of actual speed through the air, taking into account vertical and ground speed and estimated wind.

Why 60kt? To read a 10:1 turndown in airspeed in range 30-300 needs a 100:1 turndown on the pressure sensor - so just double the lower value to make sure we can measure it?

[BOAC]

Besides - the FD bars on the AF jet were commanding a CLIMB, - I very much hope EA is not a pilot but if he/she is that this view is not common across the industry. We have seen this 'concept' a few times on the previous threads and it does demonstrate a complete lack of understanding as to how aircraft fly.

[HazelNuts39]

The turbulence was modelled by introducing gusts so that the simulated parameters were copied from the parameters recorded.That information was missing in Interim #3 and explains the AoA variations without pitch variations in the simulation prior to A/P disconnect. It remains odd that the normal acceleration trace does not reflect the AoA variations.
In the specific case of alternate 2B law, some coefficients used in the longitudinal flight control law become speed-independent and are set for the maximum speed for the aeroplane configuration (330 kt in clean configuration).This may explain the difficulties I encountered in trying to correlate the side stick commands to the airplane response.

I'm sure someone can post a calculated trace of actual speed through the air, taking into account vertical and ground speed and estimated wind.Apologies if it has been posted earlier. Strangely the report never mentions that the IAS becomes increasingly erroneous after the AoA exceeds 25 degrees.

http://i.imgur.com/ibRLy.gif?1

[jackharr]

When was this lecture?

Children of Magenta - YouTube

It certainly pre-dates AF447 accident but is creepily prescient.

[Fox3WheresMyBanana]

Exactly. It's from 1997. Had the same stuff in 1988 in the RAF. Gave the same stuff in 1992.
This is why airlines should run their own training schools, ab initio, not rely on self-financed pilots getting trained by anyone they think will pass them at the most affordable price.

[rgbrock1]

Question to all those who fly for a living or have done so:

Would you have, as Captain, taken a rest break right before traversing the ITCZ?

A question was raised in the final report about the timing of the Captain's break but was sort of brushed aside. Perhaps there would have been a different outcome had the Captain stayed awhile longer in the cockpit but that's easy enough to state in hindsight.

[BOAC]

Done to death, rg, on previous threads. Me no, not with the expected 'thickness' of the zone. A few years back I asked some of the 'crusty' senior BA 'chaps' and they said rest was rostered on a flight at a specific time and these follk would normally take it at the assigned time. Many others have said not. You need to see AF flight crew orders to answer the question there.

NB The ITCZ is NOT an emergency; it is not an ABNORMAL occurrence; it is crossed many times by many aircraft all over the world every day. 2 COMPETENT F/Os are more than capable of traversing it. In essence it is just a large weather front, but it appears to have gathered some special 'mystique' for some here.

[rudderrudderrat]

Hi DozyWannabe,
FDs need to be changed in terms of their appearance in marginal systems behaviour I agree.

On page 3 of Appendix 2 FDR Chronology, at time 2.10.47 "The FD 1 and 2 become available again (modes HDG/VS). The selected heading is 34°. The vertical speed is 1,500 ft/min."

The FDs will presumably command a pitch attitude to satisfy +1500ft per min, whilst displayed.

At time 2.11.22 - 2.11.35 "The vertical speed changes from -3, 900 ft/min to -6,800 ft/min." At time 2.11.40 "The FD 1 and 2 become unavailable. The angles of attack 1 and 2 become invalid (NCD status) while the angle of attack 3 is 33°."

I suggest the flight directors will have commanded high nose up pitch attitudes, in order to satisfy +1500 ft per min even as the aircraft entered the stall and started to descend rapidly.

I understand the wisdom of turning off the flight directors during "Unreliable Airspeed", but when the FDs disappear out of view automatically, it's difficult to remember to still have to switch them off.
There was no help from the automatic reappearance of the FDs.

[DozyWannabe]

Hi rudderrudderrat - welcome back to the conversation.

According to the presentation, when the FDs intermittently reappeared they were no longer in V/S acquisition mode, and in fact changed mode multiple times during the sequence - but they didn't elaborate on which mode they were in. Hopefully this weekend I'll have a chance to give the report more than a skim.

[paull]

I did not see any recommendations on changes by Airbus so that the pilots get a heads up before they are handed the plane.
1- Guys, getting inconsistent Airspeed indications here.
2- AP will drop out, you are heading for Law 2B
3- Set pitch and thrust
4- See you on the other side.

Not too much to ask surely?
Training for 'startle' sure, but why not remove as much as you can?

[Lyman]

Paull...."I did not see any recommendations on changes by Airbus so that the pilots get a heads up before they are handed the plane."

In a way your comment holds the philosophy up for rigid examination. Pilots of this aircraft are not privy to volumes of periodically life threatening data. Three pitots? To serve the computing master alone? YES. The pilot is only allowed to see a synthesis of indicated airspeed. This amalgam is an average, and controlled within certain parameters, and when out of limit, the startle begins. The pilot is outside the decision to quit, and all data leading up to it. There seems to be no provision for pilot monitoring of the data that will challenge his manual skills at altitude. And yet the data is available. Is the pilot considered superfluous to bad data in? Here, yes.

Ever been at a restaurant and have the waiter spill your meal in your lap? Changes everything. These two had hot enchiladas thrown in the face; screws with one's 'presence of mind', eh?

[hetfield]

Concerning FDs, basically they shouldn't do anything different from AP. If Georgie quits, one should be very carefull to trust the yellow bars....

[aircarver]

Why was the trim at 13 deg. nose up ?
Did the system autotrim responding to sustained back stick ?

.

[Organfreak]

Why was the trim at 13 deg. nose up ?
Did the system autotrim responding to sustained back stick ?

Now here's a question that even I can answer.

Yup.

[aircarver]

Thanks !

.

[CONF iture]

The other report, the judicial one, is out next week ... Is it out for all to be seen, or restricted to a limited audience ?

Will it be also as an empty shell that the BEA report is ... ?

[hetfield]

Why was the trim at 13 deg. nose up ?
Did the system autotrim responding to sustained back stick ?That is a very good question!

Another one is:

Would the pilot have trimmed a conventional aeroplane to such an extend?

[DozyWannabe]

Will it be also as an empty shell that the BEA report is ... ?

I'd say the BEA report is pretty comprehensive - more so than I expected it to be. What do you find lacking about it objectively (i.e. other than it does not fit your agenda of blaming Airbus for everything and demanding they go back to a conventional control layout)?

[Lyman]

Somewhere in there is the "Tiptoe" dance BEA does around obscuration of the sticks one from the other, no? Stress 'tiptoe'.

jcjeant: Imagine what the "AP OFF" call portends? Here is Captain, seconds away from impact with the Ocean, entertaining that the problem could be originating with the autopilot? Can one be that removed from an awareness of his aircraft?

"So, wait...." Clutching at straws? It does demonstrate the Captain's awareness of the then current drill for UAS..... DO NOT re-select Autopilot.

Also, switch off flight directors, AutoThrust, etc. For me, it is emblematic of the tragic disconnect demonstrated by 'qualified' pilots of this a/c. The report has couched all the evidence toward incompetence, with minor bones thrown to involve the airframer and airline. This accident is unbelievable, as presented by the report. Suspension of disbelief is required to read it without bias. One is tempted to assign some skulduggery to its plot. The pilots obviously eliminated Stall as a possibility, for to believe otherwise is to entertain a laughable consideration of the facts as presented. If so, they must have been baffled by the lack of "response" to commands to "climb". Out of ideas from the git, not to mention the experience of actually Stalling an a/c at altitude.

[DozyWannabe]

Hardly a "tiptoe dance". It gets mentioned, but given that the design is now a successful one that has proven itself in safety terms, it's rightly mentioned at the appropriate point and left there.

I'd say the report (admittedly on a quick rather than thorough reading) is fairly even handed - the implicit primary thrust of it is towards the industry who left these pilots so ill-prepared rather than hanging the pilots themselves out to dry. The sequence of mis-steps is long, detailed and painful to read, but at no point is it suggested that this was the fault of the crew in isolation. The manufacturer comes in for censure for the way it handled certification of the Thales pitot tubes and disseminated information when the first problems occurred. Bear in mind the fact that as a civil service report it had to use very dry language and I'd say it stands up very well.

Regarding "AP OFF" at that time - well, the tendency in a situation like that is to try everything. The procedures do call for various automatic systems to be explicitly disabled and as we know, none of those procedures were followed. I wouldn't be surprised if the Captain wasn't simply taking a belt-and-braces approach to the problem. None of the DFDR traces from the point of automatic disconnect are consistent with autoflight re-engagement so ultimately it was a futile gesture, but it probably made sense to him at the time. If you're attempting an implication that autoflight was engaged at any point after the initial upset, then "clutching at straws" is putting it mildly!

[PJ2]

Would you have, as Captain, taken a rest break right before traversing the ITCZ?
Yes, discussed to death; to repeat an earlier response, "no", I never took my rest period during an ITCZ crossing, (A343, Pacific routes, NA - Australia). It was a matter of policy, (mine, not my airline's), not of crewing, trust, or anything else; the cockpit is where "the captain" belongs, in my opinion, as the crossing is an area that presents specific operational challenges and decision-making opportunities, if I can put it that way. The only think I was never entirely happy with was the notion of "RPs", (great guys & gals, but the position is not cleared to fly below cruise levels and therefore the RPs are entirely unpractised in what little manual flight there currently is available - I always thought that was false, short-term economy).

The ITCZ conditions described in the Report are precisely as they are during most crossings. Sometimes deviations were necessary, sometimes not. HF was mostly good but the advent of ADS and especially CPDLC were a god-send for such requests.

The radar would be on, tilt and gain used according to standard operating principles, (scanning up and down, calculating tops of the moisture, gain on automatic as well as manual settings). Sometimes one would have a full moon to help pick one's way between cells and avoid the over-hangs, (where necessary, almost always diverting upwind). While not frequent, St. Elmo's was often seen as was lightning, (which would also help light the way ahead if the build-ups were isolated enough). Light to occasional moderate turbulence was the rule as was the occurence of ice crystals; I know that sound that they make on the windshield.

Some common images, (obviously before nightfall), some of which I have posted before for those who may not see this from the pointy end and are trying to imagine the process of navigating ITCZ weather - it is in my opinion an art as much as it is a technical process:

http://www.smugmug.com/photos/i-gQ2BwXq/0/M/i-gQ2BwXq-M.jpg


CPDLC clearance to deviate:

http://www.smugmug.com/photos/i-FfWvx8w/0/M/i-FfWvx8w-M.jpg


Standard track off-set technique:

http://www.smugmug.com/photos/i-fGNkLJc/0/M/i-fGNkLJc-M.jpg


The weather deviated around:

http://www.smugmug.com/photos/i-pN7ZFFj/0/M/i-pN7ZFFj-M.jpg


Typical ITCZ weather:

http://www.smugmug.com/photos/i-NLrQRJ6/0/M/i-NLrQRJ6-M.jpg


http://www.smugmug.com/photos/i-6x4vW6r/0/M/i-6x4vW6r-M.jpg


http://www.smugmug.com/photos/i-ffHVPv5/0/M/i-ffHVPv5-M.jpg


http://www.smugmug.com/photos/i-3tL3P9b/0/M/i-3tL3P9b-M.jpg

At the time, we were informed that aircraft icing never occurred at cruise altitudes, below -40C, and while the problems with pitots and UAS events were occurring then, we never heard a thing about them and never once were shown or practiced the event in the sim, nor was the info ever presented in annual recurrent training or safety reviews.

I hope this is helpful for those who may not have seen this kind of weather or flown it.

[CONF iture]

Hopefully this weekend I'll have a chance to give the report more than a skim.
Why don't you wait before making the following comment then ...
I'd say the BEA report is pretty comprehensive - more so than I expected it to be.

[DozyWannabe]

Because I have done proofreading before, and I'm good at isolating details. Of course, if you'd like to tell me where it's lacking, I'll cheerfully keep an eye open for it when I do a proper in-depth read this weekend.

[A33Zab]

Link to:

Presentation webcast (http://live.webcastor.fr/bea/index.php/front/bea_en)

FF to Q&A.......Valid questions....confusing answers. (if translated correct?)

[TTex600]

Well, looks like the BEA left it up to the PPruners to figure it out. How many threads will it take to do so?

For me, this was either a situation where the holes lined up (and you can't eliminate that probability no matter what): or a situation where a system presented it's human operators too little usable information. If the first, we can just go on, praying it doesn't happen to us, or if the second we will need to understand what inputs humans need and can decipher when their world is turning to worms.

Now for my editorial comment. Airbus AND Boeing, need to present information regarding primary aircraft control in such a way that allows the aviator to scan and know vs a display that forces the pilot to scan and interpret. IOW, airspeed tapes, altitude tapes, IVSI's buried between other info, and ECAM systems that demand attention are great for video games. They suck for actually flying an airplane when one needs a clear picture of the essentials for life.

[chris weston]

Tex, absolutely agree.

Who was it said "what's gonna kill me?"

I know, that was on take off, but its still pdg advice.

[A33Zab]

Figure 64 in Final (E) report is different to (F) version.

(F) version:

http://i474.photobucket.com/albums/rr101/Zab999/figure_64_en.jpg

[PJ2]

A33Zab;

Good catch. Figure 64 in the E version is from IR#3, p42.

Likely a transcription error. There are a number of other minor edits in the E version.

[gums]

Thank you Tex.

You have nailed it.

I look at many of the panel displays and some of the military HUD presentations and wonder where the "de-clutter" switch is! When things go south I want to see a few things that are critical and not a lotta B.S. that doesn't contribute to recovering from a bad situation.

I was impressed that the report raised the issue of presenting AoA. That is sure to evoke many comments here. ya think?

Another thing that caught my eye was the reference to control law reversion to "2b". Good grief! 1a, 2c, 3a, and the beat goes on. No matter if you are Chuck Yeager or Sully or Gums, ya need to have a very clear reversion sequence on these FBW systems. Some of the reversion modes on the 'bus are related to max bank/pitch angles and such. But AoA limits ( aka "protections" for the masses) are not all that clear. Sully pointed out in an interview last few days that he would have liked to get another degree or two of pitch just before impact. Couldn't do it.

I am not in favor of a complete "manual" reversion aka "direct" without a clear and determined effort by the crew. I don't think that the AF447 crew would have used such an implementation, but maybe some others might if all their efforts failed to get the jet under control. In our system, we had the limits on AoA and gee to provide optimum energy in severe maneuvering. The AoA limit was not related to stall AoA. Nevertheless, full back stick provided the best normal gee and pitch rate that the jet could provide.

Back to the point that Tex pointed out.... Clear and relevant data on the presentations is essential. When not on Otto-pilot, then basic pitch and roll and such need to be primary. What in the hell was the crew doing with the flight directors in a vertical speed mode, or any other mode? If "x" degrees of pitch are in the boldface procedure, fine. But don't confuse the crew with extraneous flight director B.S.

Lastly, I have been unpleasantly surprised to learn that some jets like the 'bus fly so close to the edges of the envelope at 35 or 37K. I would expect this of some military platforms like the U-2 or SR-71 or the fabled Aurora, but not a commercial jet. Guess I was spoiled by a large margin of speed/mach and such.

[RatherBeFlying]

It looks like BEA had a short handout for the press and made frequent admonishments that "all the details are in the full report which you shall receive later". There was also a meeting with the families in the morning. One of the questioners is an experienced Airbus pilot who is working for the families who was not impressed by the report.

There was talk that the FD when present mostly led the crew in the wrong direction. The press questions on FD were all over the map because they don't have much clue what an FD does -- most certainly an FD does not give stall recovery directions. There may have been an indication that stall warning should either shut down the FD or present proper recovery attitude (there's something like an hour or more of dialog and I'm writing from memory).

The flight tests did not go beyond approach to stall. The presenters opined that recovery from the developed stall is out of the envelope and that recovery is highly doubtful, even with proper actions. i.e. certification does NOT require recovery from a developed stall.

There was mention of "lost indicated altitude" that I suspect was because the ADC needs airspeed to present corrected altitude and that there was an apparent initial loss of altitude that PF attempted to correct. Or was the altitude display lost -- perhaps a native French speaker can tell us just what words were used.

The question session I would really like to see is BEA answering questions from qualified pilots who have had time to read the report.

[CONF iture]

Because I have done proofreading before, and I'm good at isolating details.
...
Hopefully this weekend I'll have a chance to give the report more than a skim.And how do you isolate details as you gave the report only a skim ... ?
But if you know you're good at it, that's probably enough.

[CONF iture]

There was mention of "lost indicated altitude" that I suspect was because the ADC needs airspeed to present corrected altitude and that there was an apparent initial loss of altitude that PF attempted to correct. Or was the altitude display lost -- perhaps a native French speaker can tell us just what words were used.
The mention made was well for a loss of indicated altitude (under reading) and not a loss of altitude display.

So many questions on the FD during the presentation ...
So little answers ...
And so little in the report too ...

It has been central in the BEA work ... but they won't share the details.

BTW where is the FD/AP Vertical Mode Trace ... ???

[A33Zab]

Posted before but to refresh the memory:

(not all related to AF447)

All Thales probes have been replaced per AD 2009-0195 (http://ad.easa.europa.eu/ad/2009-0195)

Besides the probe replacement program, several hardware and software changes have been introduced:

BUSS (SW always available) - already available before AF447!
FMGEC: AP/FD not available at UAS condition. AD 2011-0199R1 (http://ad.easa.europa.eu/ad/2011-0199R1)
FCPC: F/CTL ALT LAW (PROT LOST) ECAM MSG accompanied with reason.
FCDC: More rigid 'USE MAN PITCH TRIM' PFD message when autotrim not available.
FWC: **NAV IAS DISCREPANCY MSG When 2/more IAS are detected to be different.
Added AoA data filtering to improve SW detection in turbulent conditions.
AoA: Conical shaped ground base to prevent water ingression.
** Don't know if F-GZCP was equipped with this mod but the mod was available at that time. (BEA doesn't mention the presence of this message, suspect it was NOT available in F-GZCP)

[BOAC]

My apologies if this has been covered in the previous 8 threads/thousands of posts, but can an AB person explain the two reported VS vertical modes in the report, 'VS+6000fpm+' and 'VS+1400fpm'?

My experience of FDs/A/Ps is that if the selected ALT is 350 and I am climbing above that I would expect a -ve VS demand to regain. Where did these two UP 'settings' come from? To what 'target' were the FD controllers working? Were these figures software/system induced or crew selected?

It seems as if the FDs, when 'valid', were reacting to the existing rates which is not the way I expect - ie 'Flight Followers' rather than 'Flight Directors'.

[rudderrudderrat]

Hi BOAC,

It seems as if the FDs, when 'valid', were reacting to the existing rates which is not the way I expect - ie 'Flight Followers' rather than 'Flight Directors'.
Correct. This is probably the most confusing part about the FD logic. The FDs are withdrawn automatically during unreliable airspeeds and the FMA modes are lost. If two airspeeds erroneously agree, then the FDs will reappear with present HDG and instantaneous VS. In the confusion of the moment, it appears to me that this crew then followed these new FD modes.

See EASA Airworthiness Directives Publishing Tool (http://ad.easa.europa.eu/ad/2011-0199R1) and download easa_ad_2011_0199_R1.pdf (21 kb) for a full explanation.

[HazelNuts39]

A33Zab,

Two comments:
Since that AD was issued, new FCPC software standards have been developed that will inhibit autopilot engagement under unreliable airspeed conditions. Does it also inhibit reappearance of the FD?

The BUSS, if fitted, must not be used above FL250. The main reason for that (http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-48.html#post7210355) is that the back-up stall warning threshold does not change with Mach number and the selected value of 8.6 degrees is too high above FL250.

[BOAC]

Thanks rrat - apart, then, from the obvious lack of flying ability of the crew and absent cockpit management skills, this system function may well be a major contributory cause of the accident.

Even that AD does not 'cut the mustard' for me - it refers primarily to A/P engagement and only a fleeting mention of the FDs.

"Further analyses have shown that, after such an event, if two airspeed
sources become similar while still erroneous, the flight guidance computers
will display the FD bars again, and enable the re-engagement of AP and
A/THR. However, in some cases, the AP orders may be inappropriate, such
as possible abrupt pitch command."

What about the FD 'orders'? Does the software mod direct the FMC to target selected altitude rather than any other convenient number?:ugh:

[A33Zab]

Does it also inhibit reappearance of the FD?


According company info it does:
---
The Flight Control Primary Computer (FCPC) has been modified by installing a new software standard; P11AM20A 2K2.
The only improvement introduced with this software update concerns the autopilot inhibition under unreliable airspeed condition.
When there are significant differences between all airspeed sources,
the flight controls revert to alternate law, the autopilot (AP) and AutoThrust (A/THR) automatically disconnect and the Flight Director (FD) bars are automatically removed

---

The BUSS, if fitted, must not be used above FL250. The reason for that (http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-48.html#post7210355) is that the back-up stall warning threshold does not change with Mach number and the selected value is too high above FL250.

The FL250 threshold is explained in FCOM as:
---
Cases of unreliable speed situation caused by temporary contamination of the pitots with water or ice (typically above FL250), usually disappear after a few minutes.
The flight crew flies pitch/thrust and activates the BUSS only if the unreliable speed situation appears or remains below FL250.
This distinction (FL 250) ensures a good balance between crew workload and safety
(continued flight using the BUSS or temporary use of pitch/thrust tables).
---
But you are correct: the Backup Stall Warning values are fixed values for S/F config.

[HazelNuts39]

A33Zab,

IMHO the FCOM explains the reasoning behind the selection of 8.6 degrees. Once chosen, this value limits the usability of the BUSS to below FL250. Higher altitudes require lower values of the S/W threshold, which would have impaired the usefulness of the system at low altitude.

[A33Zab]

but can an AB person explain the two reported VS vertical modes in the report, 'VS+6000fpm+' and 'VS+1400fpm'?


I'll return later for more FD/FMGEC info. [job is calling]

For now:

http://i474.photobucket.com/albums/rr101/Zab999/VS1.jpg

[rudderrudderrat]

Hi BOAC,
Does the software mod direct the FMC to target selected altitude rather than any other convenient number?
As far as I'm aware - No. It would have been necessary to reprogram the FDs with Open Descent etc. to reacquire the FL they had departed from.

The first line of the Memory items of the "Unreliable speed Indication / ADR Check Proc"
AP/FD .... Off
was never accomplished. It doesn't help to solve the problem when the FDs keep reappearing with erroneous guidance.

[hetfield]

From the Final Report

At 2 h 10 min 05, the autopilot then the auto-thrust disconnected and the PF said
“I have the controls”. The aeroplane began to roll to the right and the PF made
a nose-up and left input. The stall warning triggered briefly twice in a row. The
recorded parameters showed a sharp fall from about 275 kt to 60 kt in the speed
displayed on the left primary flight display (PFD), then a few moments later in the
speed displayed on the integrated standby instrument system (ISIS). The flight
control law reconfigured from normal to alternate. The Flight Directors (FD) were
not disconnected by the crew, but the crossbars disappeared.When the ASI came back, the bars reappeared and the AP would have been be available again.

[aircarver]

I noted (from the report) a GPS altitude was available. Is there a procedure for using it in the face of erroneous airdata altitude ?

.

[MountainBear]

In the confusion of the moment, it appears to me that this crew then followed these new FD modes.

This one sentence sums up everything I dislike about the final report.

It seems to me that there are two areas of wide-spread agreement.

(1) The pilots were confused about what was happening to them.
(2) Despite this confusion they acted.

There is no widespread agreement as to why they acted the way they did.

Instead, the report describes an olio of pet agendas including confusing technology, psychological error, training issues, etc. To mix a metaphor, in response to this cloud of unknown gnats BEA loads its formidable cannon of recommendations with grapeshot, praying that somehow one of those little lead balls will hit the little gnat actually responsible.

Complex systems fail in complex ways but that's no excuse for making hash. :=

[OK465]

There is no widespread agreement as to why they acted the way they did.

Probably never will be...

But if "turning over all the rocks" results in finding something that can be potentially problematical the 'next time', whether or not it was only a 'possible' factor in this case, it deserves attention.

One gnat at a time...

[PJ2]

BOAC, OK465, RRR, A33Zab;

I believe the reason for ensuring the disengagment of the FDs during the UAS drill is based upon the default longitudinal AP/FD engagement mode of V/S or FPA. The removal and reappearance of the FDs would logically be the same as pushing the FD switch OFF then back ON again. When that occurs the V/S or FPA is synchronized with the aircraft parameter, whatever it happens to be at the time of re-engagement. From there, the pilot makes an appropriate selection such as OPEN CLB/DESC, or, for immediate altitude hold, setting the V/S to zero, etc. (Another way to put it...V/S or FPA are simple, selected (ie, not managed), modes - the FDs could not "know" what "1400fpm" or "6000fpm" was for...it just reflected current conditions, from which selections may or may not be made).

The essential aspect of the UAS drill is flight path stabilization via pitch & power. The FDs could non-intuitively counter that response depending upon conditions at re-engagement.

Mountain Bear;
Complex systems fail in complex ways but that's no excuse for making hash.
Ensuring a stable flight path would have avoided the accident.

While the slavishly-following-the-FD theory makes sense, as posited by some even before the report was issued, it makes no sense to many who have flown bread-and-butter transports that could actually be stalled any time and who now fly this or any aircraft with complex automation; it's a tool in the kit and nothing more - still is. "Looking through" the directors to the raw data on the instruments and combining that with one's understanding of the energy and stability of the machine was always a valued approach but not anymore.

The ability to understand and even have some depth of intuition about flight in heavy transports in the operational environment is the larger story here.

[BOAC]

I realise I am rather late at the 'They followed the FD' dining table, but why does this possibility not feature more in the BEA report? Is it not a horrendously poisonous cocktail to present to a confused crew - an apparently 'computer generated so must be right' driven VS demand, totally seductive, when all else has fallen around your ears? Why not a simple 'Select Vertical mode' inhibit?

[hetfield]

BOAC

The FD on the bus, even on the A300, is just one of many traps.

Fortunately the airline I used to work for put some emphasys during training on that issue.

[Flyinheavy]

@BOAC

May be because PF was really concerned with "Overspeed"...

2.1.3.3.1 PF’s reactions

On the other hand,
in the absence of airspeed information known to be reliable, it is possible that the
PF thought that the aeroplane was in an overspeed situation, notably due to his
interpretations of several clues:

ˆ The aerodynamic noise,
ˆ The buffeting, that he might have interpreted as being due to high speed,
ˆ The speed trend arrow on the PFD, which at that time indicated acceleration.

He reformulated his impression
a*few seconds later, combined with an attempt to extend the speedbrakes.
Other factors which may have prompted the PF to fear an overspeed situation were:
ˆ The display on the ECAM (max speed 330/.82) combined with the reconfiguration
to alternate law which may have been read;
ˆ The fact that, in cruise, the upper red strip on the speed tape (MMO) is about ten
knots above the current speed, whereas VLS is barely visible at the bottom of the
tape (thirty knots less);
ˆ The dangers associated with overspeed situations embedded in the collective
consciousness of pilots.

[jcjeant]

I realise I am rather late at the 'They followed the FD' dining table, but why does this possibility not feature more in the BEA report? Is it not a horrendously poisonous cocktail to present to a confused crew - an apparently 'computer generated so must be right' driven VS demand, totally seductive, when all else has fallen around your ears? Why not a simple 'Select Vertical mode' inhibit?

Procedure AF for unreliable speed:
Select FD OFF
AF447 crew don't followed the procedure ... sad ...

[hetfield]

Procedure AF for unreliable speed:
Select FD OFF
AF447 crew don't followed the procedure ... sad ... YES, but the bars already disapeared when ASI went bust....and the AP kicked off.

A trap!

[Mr Optimistic]

One question I have that I think actually determines my layperson opinion on this is why, given the duration of the incident, there appears to have been no vigorous attempt to acknowledge that the response wasn't having the desired effect and to at least articulate alternative strategies. Odd to persevere with failure and not fight harder.

[aircarver]

Did the autopilot stall the airplane on bad airdata before it clicked off and handed over to the pilots, or did the PF immediately imply an overspeed, and stall it with the long period of stick back ?

.

[henra]

When that occurs the V/S or FPA is synchronized with the aircraft parameter, whatever it happens to be at the time of re-engagement. From there, the pilot makes an appropriate selection such as OPEN CLB/DESC, or, for immediate altitude hold, setting the V/S to zero, etc. (Another way to put it...V/S or FPA are simple, selected (ie, not managed), modes - the FDs could not "know" what "1400fpm" or "6000fpm" was for...it just reflected current conditions, from which selections may or may not be made).


Interesting!
Is that behaviour known and clear to an average AB Crew?
Technically I can see the logic behind but on the other hand that could indeed be somewhat misleading if the behaviour is not properly understood by the Crew. And indeed it appears the behaviour was not clear to them because after the intial rapid climb one could conclude they followed the 1400fpm of the FP.
It might at least be a good idea to automatically disconnect the FD in the same way as the AP in case of UAS so that it deliberately has to be reengaged. This might help a crew that failed to properly follow the procedure for whatever reason.

Altogether I do not really share the feeling that the report put too little emphasis on the FD. These reports are always very indirect in language and considering that I felt they highlighted the FD rather prominently. To me the report implies most of the committee also had the impression that the FD played an important role especially during the extermely relevant first minute of the incident.
After that things were pear shaped anyway and recovery was getging more and more unlikely. Once they were at 40° AoA things were set firmly for a bad ending. (Anyone trained in doing a 45° Nose dive at 30kFt in a 200t airliner at night in IMC with uncertainty about validity of instrument readings?)

[JoeQ]

What about the affect of the audible alarms. Doesn't the noise make it more difficult to think clearly? Is it really very helpfull to have the alarms keep repeating? I know that when I am in a stressfull situation i just want everyone to shut up for a bit so I can think. Has there been research done on that subject?

Sorry if this has been discussed before. I have read many of the threads, but alas, not all of them.:O

[PJ2]

Is that behaviour known and clear to an average AB Crew?
I would certainly expect so, it's part of knowing one's airplane. But it is one of those transient characteristics that is somewhat "invisible" because normally we're on the way to something else in terms of a selection. On the engine-out on takeoff, we would level off the A320 by selecting "0" on the V/S but when initially rotating the knob it would synch with the current VS, from which an adjustment would be made.

The UAS memorized items require that the AP/AT/FDs are all turned off.

Automatically, (meaning the system does it, not the pilot), turning the FDs off with an abnormality such as an NAV ADR Fault may or may not be a good thing. Solving one specific issue always has a "dozen" other perhaps-unanticipated outcomes so it would have to be studied, just like the THS continued trimming after a stall warning, and the loss of the stall warning (NCD - no computed data) below 60kts. Perhaps it should latch?...but that can't be determined until a full analysis of all possible/knowable outcomes are tested.
After that things were pear shaped anyway and recovery was getging more and more unlikely. Once they were at 40° AoA things were set firmly for a bad ending. (Anyone trained in doing a 45° Nose dive at 30kFt in a 200t airliner at night in IMC with uncertainty about validity of instrument readings?)Well, there has been input, (by Owain Glyndwr (http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-5.html#post7143575)) that recovery may have been possible at various altitudes. Owain indicates that a reasonable "unloading" of the wing/reduction in AoA could be done with a steadily-held 10deg ND and in fact lower down, (thicker air), the recovery would be slightly quicker.

[kwateow]

The PF flew a perfectly flyable, reasonably safe and fairly stable plane into a stall.

AF procedures for "unreliable air speed" were not followed at any time.

[jcjeant]

Well, there has been input, (by Owain Glyndwr (http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-5.html#post7143575)) that recovery may have been possible at various altitudes. In the press meeting the BEA had to answer the same question (recovery possible ?)
Their answer was they don't know .. as this was never tested in real life on a A330
But like they stated it .. it's seems that for the BEA that recovery was impossible .. unless a miracle ......

[mm43]

jcjeant; It seems that for the BEA recovery was impossible .. unless a miracle ......On reflection, I believe the BEA have developed the Report on the basis that their mandate was to determine the actions and/or events that lead to the aircraft departing the Normal Flight Envelope. The report then covers factual information concerning the LOC through to impact.

Consequently, they are very vague on possible alternative outcomes for which no validated data is available, and it is up to the airframer and regulator to establish procedures that can be used in a LOC situation where the envelope has been "extended".

[aircarver]

Why no AOA indicators ? The report indicates the data is available buried several pages down, but it isn't an indicator you can fly to.

Seems pitch was being referenced as AOA when they were wildly different.

The airplane was being nervelessly flown in 'coffin corner' by the autopilot with good air data, to save fuel. Once the pitot inputs were lost, the autopilot threw the chore back to the humans, who were even less equipped to do the task without reliable speed data.

Yet the PF kept trying to keep the altitude that it was almost impossible to hand fly at. Why not a procedure requiring dropping down to a less demanding (altitude) in the flight envelope when the autopilot goes on strike. Screw saving fuel until the other problems are sorted out.

.

[gums]

Kinda disappointed by PJ's reference to setting FD modes and such.

Fer chrissakes, attitude and power and an understanding of the aero for your jet should dictate what control inputs you make, and not the flight director or its modes.

Again, I do not advocate the crew reverting via a switch to "direct" law.

The final report makes a case for concern by the crew with overspeed. I can understand that. One thing that happens when the mach gets too high is aileron reversal, and this could have been a concern. Nevertheless, the report clearly mentions over and over the inapropriate application of back stick.

A shameless plug for the primitive FBW system and control laws I flew for 4 years - our AoA was related to the gee command. So at the max allowable AoA we could not command more than one steekeeng gee! The nose could not be commanded for a further rise, and the tail surfaces would be commanding for nose down. So we sat there with full back stick and 27 degrees AoA and one gee until we pushed forward on the stick. Falling like a rock, but we could command less than one gee and gain energy and the fight was still on.

Gotta go....

[henra]

Well, there has been input, (by Owain Glyndwr (http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-5.html#post7143575)) that recovery may have been possible at various altitudes. Owain indicates that a reasonable "unloading" of the wing/reduction in AoA could be done with a steadily-held 10deg ND and in fact lower down, (thicker air), the recovery would be slightly quicker.



Aerodynamically I could well imagine that recovery was possible until quite late in the sequence. Maybe even down to 10 kFt. After all it is a conventional tail airliner and they were not in a spin. So the Tail was in free airflow. With full ND elevator and maybe neutral or at least less extreme NU trim it is liekely that the Nose would have dropped sufficiently to at some point re- attach the airflow over the wing. Might have taken 30s sustained ND or even more but personally I don't share the pesssimism that it wasn't technically possible.

It is more the practical probability which I would consider exteremely low. At no time the crew appeared in a mental constitution to unambiguously diagnose what was going on and to act accordingly and sustain that action until it yields the results (which could have taken rather long and decided action, much much longer and decidedly than they seemed to be willing to pursue a scheme). It appeared they tried something and if it didn't yield within seconds they reverted the action.

[OK465]

@gums:

In my mind, PJ2 has always been one of the staunchest and unswerving advocates of attitude & power, flight path stabilization, and 'knowing' your aircraft, both aero & systems-wise.

It appears to me that he is only explaining how the system works & what they were dealing with. But I don't want to speak for someone else.

@ The stall:

I flew 3 T-tail air transport aircraft which did not 'deep stall' and one military conventional tail aircraft that did.

The bottom line on this recovery and associated techniques is that none were ever attempted because there was no recognition that they were ever required.

If the term 'deep stall' is not meaningful enough or does not fit the formal definition, or offensive to anyone, call it a 'pterodactyl' or a 'lemon drop'. That won't change it one bit.

Just don't call me late for dinner. :)

[PJ2]

gums;

Well, if true, and the Report does spend some time on this, yes, it is disappointing that the pilots in this case actually "obeyed" the FDs, but quite frankly I have never heard of any pilot I know actually blindly following the flight directors and ignoring the instruments.

Guys I flew with, regularly turned the FDs off if they weren't following them - it's just something one does on the Airbus without even thinking about it, so drilled into Airbus pilots is this requirement.

Ever since the A320 accident at Madras, Airbus pilots have been made VERY aware that if the flight directors aren't going to be followed, turn them off, (the original problem concerning IDLE-OPEN DESCENT with one FD on has long since been fixed).

Now if you're following them, you're not going to turn them off, but if you're going to follow them you had better be damn certain in your own aviator's mind where these bars are taking YOUR airplane.

When a few first suggested that the PF might actually have followed the FD I dismissed it - no transport pilot, esp. an Airbus one, would blindly follow FDs without always questioning what the FD is leading one towards - the computers are high-speed idiots, nothing more. We regularly talked of "looking through" the FDs during momentary changes in flight dynamics and we'd wait for the FDs to catch up to the airplane while temporarily ignoring them. That just comes from a lot of hand-flying but you'll never get it from turning the knobs.

OK465 - thank you - you're quite correct - I'm just explaining the system.

It's an ordinary, very good FD that deserves the same respect and treatment any computer system does - "check six", "trust, but verify", hand-fly raw data - it works because it's an airplane and a beautiful one at that; it is not a computer platform or an iPlane.

Henra - we're on the same page - yes, it could have been recovered. No, I wouldn't have expected this crew to try given how cockpit discipline was conducted.

[gums]

Thanks, PJ, it's what I thot, but some newbies may not realize the fine points. Blindly following the FD's is not always recommended when the steam gauges are telling you that something is awry.

For OK, the jet was not in a "deep stall", but rather "deeply stalled". A nose down stick and maybe even power could have recovered the thing, given 35,000 friggin' feet to do so.

It comes down to realizing what the jet is doing and what you can do about it with the tools you are given.

The complicated reversion laws and pilots thinking they have this and that "protections" is not healthy, IMHO. Ya gotta have a baseline that you can count on without a manual switch to "direct" law, which I do not recommend unless you are Chuck Yeager. And then we have the THS that follows the pilot back stick to achieve the commanded gee, NOT THE AOA!!! So to recover, the pilot had to roll the THS trim down and also push forward on the stick in order to provide the nose down moment required. I was surprised that BEA discussed the longitudinal static stability. Considering that the jet control laws disregard AoA other than warnings and some limits in "normal law", would seem to me that we could look at that aspect a bit more.

[PJ2]

gums;

What "de-confuses" the airplane is flying it like any other airplane. I don't think I was unusual in the way I thought about the A320/A330/A340...I was never "aware" that there were "protections"...it was flown like a DC8, or a Lockheed or a B767 - just never took anything for granted. It is astonishing that this should be permitted to change as it is so fundamental to staying alive and keeping others who are with you alive.

Demonstrating one's knowledge of the autoflight should be one of many exercises instead of the way the entire sim exercise is conducted. These days I suspect one risks drawing criticism if one insists on hand-flying some exercises. But the instructors have to sign the sheets saying such stuff was covered, so the sheets have to change.

Raw data, non-FD, manually-flown (including autothrust OFF), ILS and non-precision approaches ought to be regular exercises in recurrent sims.

The beancounters and even ops managers may resist that thinking but indications are, here in the Report and in the US particularly after Colgan, (as mentioned in the Report) that it is time to re-prioritize skills, teaching/training, standards and checking.

[OK465]

...the jet was not in a "deep stall", but rather "deeply stalled"

This now appears to be a question of adjective versus adverb...:p

[CONF iture]

What "de-confuses" the airplane is flying it like any other airplane. I don't think I was unusual in the way I thought about the A320/A330/A340...I was never "aware" that there were "protections"...it was flown like a DC8, or a Lockheed or a B767 - just never took anything for granted.
Like most of us, you never had to apply the relevant memory items in real life, but for the simulated life you have been asked to get the maximum and just rely on the protections. Anything else and you didn't follow the Published Emergency Procedure ...

[gums]

Point taken OK, and I had posted a graph of the pitch moment for the Viper a year or so ago. Flew at least two jets that could be "deeply stalled", but pushing forward and keeping wings level with rudder would enable a prompt recovery. In the Viper, we had about a ten deg AoA range that did not allow a nose down effect using full elevator. The 'bus folks claimed that the cee gee for AF447 was well forward of the allowable value, so the jet had a positive nose down pitch moment through out the drill.

I go with PJ a 100% on a few drills flying the jet without all the FD's and otto help. There's no need to be macho and "prove" your manhood/womanhood. Just demonstrate you can fly the damned jet without all the gizmos.

Finally, I re-iterate my instense dislike for the term "protection" versus "limit". For some reason, I found it easier to remember the jet's "limits" than how it was supposed to "protect" me.

[jcjeant]

cjeant; Quote:
It seems that for the BEA recovery was impossible .. unless a miracle ......
On reflection, I believe the BEA have developed the Report on the basis that their mandate was to determine the actions and/or events that lead to the aircraft departing the Normal Flight Envelope. The report then covers factual information concerning the LOC through to impact.

Consequently, they are very vague on possible alternative outcomes for which no validated data is available, and it is up to the airframer and regulator to establish procedures that can be used in a LOC situation where the envelope has been "extended".

As the A330 was never tested in real life for stall and recovery ... the AF447 pilots were (against their will) promoted test pilots when the aircraft stalled
Unfortunately they do not look like they were qualified for the job ...

[mm43]

jcjeant;Unfortunately they do not look like they were qualified for the job ... If they didn't know how not to stall it, recovery was then an even bigger ask.:sad:

Not knowing you were stalled, made the outcome inevitable.:eek:

[geoff sutherland]

JCJEANT...are you sure they never tested A330 stall recovery? Is that possible?

[BOAC]

Might have taken 30s sustained ND or even more but personally I don't share the pesssimism that it wasn't technically possible. - firstly, this is not really relevant to this accident since the crew did not have the first notion that they were 'stalled', but way back in the dark annals of the multiple threads on this I posited that 20k would be my guess at the absolute lowest recovery altitude and below that they were in yet another 'coffin corner'.

Posters talking about '30 secs sustained ND or even more' need to remember that

a) This a/c was descending at around 10,000 fpm ie from 10k, one minute to impact
b) A pitch change of around 30-40 degrees nose down would have been required to initiate unstall, which would probably have raised the r o d to around 20k fpm
c) Now pull out at xxx g?

[PJ2]

BOAC - again not to resurrect things but your numbers were about what my sim exercise produced from FL350 - one was just above FL200 - the others around FL 250 or so IIRC. Descent rates were as high as 17,000fpm. I did not try it lower and now wish I had.

Owain Glyndwr's numbers show a 10deg ND steady pitch attitude, for recoveries at FL350, FL200 and FL60 at 3, 2 & 1 deg/sec AoA recovery rates.

The FL350 scenario recovers between FL250 and FL220 which coincided with most but not all our exercises; the FL200 scenario recovers between FL145 and FL125 and the last scenario recovers about a thousand feet above the sea.

[henra]

Posters talking about '30 secs sustained ND or even more' need to remember that

a) This a/c was descending at around 10,000 fpm ie from 10k, one minute to impact
b) A pitch change of around 30-40 degrees nose down would have been required to initiate unstall, which would probably have raised the r o d to around 20k fpm
c) Now pull out at xxx g?

I agree it is not really important in the given case,
just out of curiosity I had again a rough look at the physics behind.

We are probably talking about somewhere between 10 and 20kFt.

I appologise upfront for re- doing the calc.
[Assuming stall speed of ~180kts @200t, no flaps, we need 250kts IAS for a 2g recovery. At 10 kft that corresponds to ~300kts IAS. At an angle of 45 ° this would produce ~22kfpm (300kts x sin(45°)). If we assume linear acceleration (which I admit is not 100% true) that would give us an average 16kfpm.
In 30s that would mean a drop of 8k.
Edit : At 30° - 35° RoD would be 16kfpm. Simplified average 13kfpm.
This would give us 6500ft drop.

Now the 2 g recovery:
R = v^2/a: with a = 9,81 m/s (Out of the 2g maneuver capability @300kts TAS (=250kts IAS) one g is required for Sir Isaac Newton). That gives us a radius of
2430m. At an angle of 45° the corresponding lost altitude would be (1- cos(45°)) x Radius. That would gives us an additional 710m (2370ft)].
Here I err on the conservative side, as recovery in the given example would have been below 3kft and thus 250kts IAS wouldn't have meant 300kts TAS but rather 260kts.
(Edit: 1500ft at 35°)

So we have lost somewhere between 6,5 and 10kft for acceleration to a speed where recovery could be executed and between 1,5 kft and 2,5kft for the recovery itself. However it would be easy to start to early with the recovery and run into the next stall.

However, from a purely theoretical PoV somewhere close to 10.000ft might have been possible.
Apologies again for beating this poor dead horse again.

But I fully agree this has no practical meaning in the given case.

[BOAC]

Owain Glyndwr's numbers show a 10deg ND steady pitch attitude- I admit I cannot understand these figures - with an AoA of 35-40 degrees, and a pitch attitude of ?13-18 degrees? an instantaneous change to 10 degrees nose down still leaves you with an (admittedly improving) AoA (ball park) of between 12 and 17 degrees. ie no 'instant' unstall. How long do you wait? Are we not confusing attitude with Aoa here? Go back to ?mm's? early AoA pics and overlay a 10 degrees nose down pitch.

I am also uncertain how representative a sim exercise would be with AoAs of that value - can they even be achieved and is the software up to the job?

[Owain Glyndwr]

I admit I cannot understand these figures - with an AoA of 35-40 degrees, and a pitch attitude of ?13-18 degrees? an instantaneous change to 10 degrees nose down still leaves you with an (admittedly improving) AoA (ball park) of between 12 and 17 degrees. ie no 'instant' unstall. How long do you wait? Are we not confusing attitude with Aoa here? Go back to ?mm's? early AoA pics and overlay a 10 degrees nose down pitch.

I was hoping to stay lurking until I had time to read the whole of the final report, but since several people have referred to my theoretical study I thought I'd better chip in.
Yeah I agree the process is not intuitive. I gave my best shot at an explanation in Thread 8 post # 175. Not an 'instant' unstall though - it takes quite a while to get the AoA down to sensible levels. I also fully agree with the statement that this represents theoretical possibilities and that the psychological pressures on the pilot might well inhibit maintaining the necessary ND attitude for long enough. And no, I think I understand the difference between attitude and AoA well enough.
As for the BEA response - I think they said they didn't know because nobody had done the sums or (certainly) any relevant flight tests. They didn't (AFAIK) say it was impossible.

[HazelNuts39]

Owain Glyndwr's Recovery trajectories (http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-5.html#post7143575)

[kit344]

Another (minor) error on BEA website 5 July 2012 press briefing (http://www.bea.aero/en/enquetes/flight.af.447/point.presse.05juillet2012.en.php)

In the English version of the Summary, Paris time is stated to be 5 hours ahead of UTC. French, German and Brazilian (Portuguese) versions appear to be correct.

They have also transposed the links to DE and BR summaries with http://www.bea.aero/fr/enquetes/vol.af.447/note05juillet2012.br.pdf under the German flag and http://www.bea.aero/fr/enquetes/vol.af.447/note05juillet2012.de.pdf under the Brazilian flag.

[rudderrudderrat]

Hi DozyWannabe,

Your comment on 19 April http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-5.html#post7143575 post #94

However, "following the FD" is *exactly* what the AF447 pilots had been trained to expect to do 99% of the time. was amazingly accurate.
It explains (to me) the pitch attitudes PF attempted to follow and his errors.

[DozyWannabe]

Did the autopilot stall the airplane on bad airdata before it clicked off and handed over to the pilots

No - in fact it's for that very reason that the values are constantly compared and the AP will disengage if there's a discrepancy. The aircraft did not stall until it reached the apogee of the zoom climb, at which point it had been under manual control for almost a minute.

or did the PF immediately imply an overspeed, and stall it with the long period of stick back ?

That's the big question, and judging by the content of the final report there's not enough clear-cut information to provide a definitive answer there. Instead what we have is a series of possibilities, each of which has to be eliminated. Those giving the report short shrift because it does not provide a definitive answer are missing the point - it's not the fault of the investigators, it's that there was insufficient information available to provide a simple answer.

For one thing, I don't think it's a coincidence that a push for flight-deck CCTV monitoring began around the time the final report was being compiled.

Hi DozyWannabe,

Your comment on 19 April http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-5.html#post7143575 post #94
was amazingly accurate.
It explains (to me) the pitch attitudes PF attempted to follow and his errors.

Why thank you. I feel compelled to admit I wasn't the only one pointing that out, however. :)

That said, I don't think the FDs alone were the cause of the PF's pitch-up commands*, just as I don't think fear of overspeed or expectation of being able to rely protections would do it in isolation. I suspect it was a combination of any or all of those factors and possibly more.

This is what irks me about some of the criticisms of the report in this thread - because if the accusations of the BEA trying to protect Airbus and AF by pinning it on the crew were true, they could easily have taken a look at the probable FD behaviour, stated that the crew contravened procedure, stalled and crashed the aircraft and left it there.

Instead what we have is a fairly exhaustive review of all the possible factors that led to the accident, inclusive of shortcomings on the part of the manufacturer, operator and the industry as a whole - there's even a whole section devoted t othe handling of the recovery operation and how to rectify mistakes made there. While there's a lot of material dedicated to how the crew mishandled the situation, the findings and conclusions only relate that factually. The implicit reprimands seem to be largely directed at the industry as a whole.

[* - The reason for this is that we don't know precisely when they re-appeared, how long they re-appeared for, we only have a theory on what they might have displayed based on systems behaviour - and probably most importantly, if the PF even saw them when they did re-appear on each occasion that they did. On its own it's an interesting rather than compelling theory, but in concert with everything else working against the crew it's definitely something that needs to be eliminated in future.]

[rudderrudderrat]

Hi DozyWannabe,
The reason for this is that we don't know precisely when they re-appeared, how long they re-appeared for, the times and modes are here
http://www.bea.aero/docspa/2009/f-cp090601.en/pdf/annexe.02.en.pdf
I hope Airbus changes the FD logic. If the FDs are withdrawn automatically, then they should remain withdrawn until the pilots reselect them.
To have them reappear automatically in a different mode to that which the pilots originally engaged them, can be very confusing.

[DozyWannabe]

Hi DozyWannabe,
the times and modes are here
http://www.bea.aero/docspa/2009/f-cp090601.en/pdf/annexe.02.en.pdf
I hope Airbus changes the FD logic. If the FDs are withdrawn automatically, then they should remain withdrawn until the pilots reselect them.
To have them reappear automatically in a different mode to that which the pilots originally engaged them, can be very confusing.

Agreed. That behaviour is far from optimal and should be altered regardless.

That said, while the times and modes are displayed in the annex, that still only provides an estimate of what might have been displayed. Taking a look at the timeline, the FDs reappeared twice during the climb phase of the accident sequence - first in ALT CRZ* mode, and subsequently in VS/HDG mode. They then reappeared during the descent phase several times.

Here I need a bit of clarification - in this mode, will the FDs lock to the current vertical speed or the selected vertical speed?

[rudderrudderrat]

Hi DW,
The reference to "vertical speed selected" is what the FDs automatically acquired on automatic re-engagement.
The reference to "vertical speed" is what the aircraft is actually doing.

[OK465]

I am also uncertain how representative a sim exercise would be with AoAs of that value - can they even be achieved and is the software up to the job?

Level D simulators generally have a touch screen instructor station display. On the systems/flight diagnostic page there is an icon labeled "INPUT GUIDANCE".

Selecting this page allows you to choose a specific internal software parameter, such as ALPHA, and have it 'artificially' displayed on the ND where VOR DME would normally be. This function allows two different parameters to be selected at any given time, i.e. VOR 1 DME & VOR 2 DME could be set to display ALPHA & BETA. (A poor man's AOA :))

The ALPHA values at any point are very consistent with those from the FDR, a credit to the Sim manufacturers and the value of the 'predicted' data provided with the software 'flight package'. (BETA is another story)

I believe the mathematical analyses of recovery altitudes assumed a constant average nose down pitch rate (based on actual pitch rates generated for short periods from the FDR data) and a specific constant 'G' applied at a given speed on the pull-out. Correct me if I'm wrong.

This is all well and good if the FCS is 'agreeable' to providing those pitch rates over the extended period of time encompassing the full exercise. In other words, the analysis is, at least partially, independent of the specific flight control system as the SS is held forward for longer and longer periods, the 'assumed' long term pitch rate being extrapolated from short periods.

It may be entirely representative...:confused:

[Owain Glyndwr]

I believe the mathematical analyses of recovery altitudes assumed a constant average nose down pitch rate (based on actual pitch rates generated for short periods from the FDR data) and a specific constant 'G' applied at a given speed on the pull-out. Correct me if I'm wrong.This is correct for the entry and exit manoeuvres, but for by far the longest time the aircraft was assumed to be held at constant pitch attitude - in most cases 10 deg ND but other attitudes were looked at. The thinking was that attitude was about the only thing he could rely on and hold easily. 10 deg was a "for instance" value which might not have been too extreme to be believable, and was held for a long time just to see if it would have been effective. So your next point is OK - the sums did not depend on the ability to hold specific pitch rates over an extended period and weren't really any sort of function of FCS except insofar as the entry rate of pitch was concerned, and even there one could show that the entry rate did not significantly affect the outcome.

[DozyWannabe]

Cheers.

I thought that was the case, but wanted to make sure.

So - with that checked, your assertion about the discrepancy between the selected VS and actual VS during the descent phase of the sequence is correct (i.e. the FDs could well have been commanding a high nose-up pitch angle). However, during the descent phase with the aircraft stalled, the PF would have had a job keeping the nose consistently above 0 degrees, and chasing a positive FD command then would have been practically impossible.

What's interesting to me is what happened in the climb phase, and for me it's vital to keep these two phases distinct in terms of analysing FD behaviour and correllating it with the PF's actions. In both cases of the FDs' reappearance during the climb phase the discrepancy between the pitch angle, selected V/S and actual V/S should never have indicated an instruction to put the nose up to 15 degrees, but that's what happened.

Picking this apart is a complex endeavour!

[rudderrudderrat]

Hi DozyWannabe,

Please see post #113 by A33Zab.
I can't explain the initial climb without flight directors (perhaps work load, surprise, CBs, Lightening flashes, smell of ozone, noise on the cockpit from hail, AP disconnect wailer, ECAM dings, ALT Alert warning, "Stall Stall" SV, and calls from the cabin crew, etc. played some part.)
However A33Zab's picture seems to correlate quite well a bit later.

[OK465]

...but for by far the longest time the aircraft was assumed to be held at constant pitch attitude

OG:

This is somewhat of a conundrum in the sense that when you reach -10 degrees, as you say a long time before actual recovery, to hold that pitch attitude do you...

1. release the SS, i.e. FCS positions the elevator to hold what?

Still stalled, It's likely the elevator would go right back to full ANU to hold ~1G and the existing flight path which is quite a bit steeper downhill than 10 degrees at this point. Rule out SS release?

2. or is the SS manipulated, i.e. what is necessary, considering FCS elevator response, to hold a constant pitch attitude while stalled? If not continuing full forward, how do you do this? Some occasional aft SS necessary? (rhetorical :})

The FCS has a pretty big say in what you actually get here in practicality, although the theoretical side is certainly sound and I understand that's as far as you intended to take it or that anyone could take it. :ok:

In practicality, I wouldn't come off the forward SS stop (with whatever extended nose down pitch rate was actually available) until I knew that I was 'flying' again. This approach, of course, may change some of the values. :)

[DozyWannabe]

Please see post #113 by A33Zab.

I hope we're looking at the same post - I'm seeing one with this image, which deals almost exclusively with the climb phase...

In fact I've (roughly) highlighted the areas where the timeline says the FD was available and in which mode:

http://i1088.photobucket.com/albums/i331/turricaned/VS1_FD.png

In the first case, I'm not sure what ALT CRZ* might have presented, but in the second case, even with +6000fpm selected, the FDs engage with an actual VS in excess of that. In that case, would the FD have commanded nose down?

[HazelNuts39]

1. release the SS, i.e. FCS positions the elevator to hold what? You definitely would have to apply forward SS until starting to pull up. How much SS I don't know. This post (http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-9.html#post7154767) has a graph that shows the normal acceleration NZw.
Another post (http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-11.html#post7156875) shows it for another trajectory.

N.B. In these graphs NZw is the acceleration normal to the flight path, whereas it is usually measured normal to the airplane's longitudinal axis.

[Owain Glyndwr]

or is the SS manipulated, i.e. what is necessary, considering FCS elevator response, to hold a constant pitch attitude while stalled? If not continuing full forward, how do you do this? Some occasional aft SS necessary? (rhetorical)

Perhaps I should have written "assumed to be flown at a constant pitch attitude"
Even in the stall the aircraft always responded to elevator is a conventional manner, and I didn't really anticipate any difficulty in using the stick to maintain constant pitch. So I didn't give the practical piloting technique a lot of thought :)

But as you say, I didn't intend it to be taken too far - I was just curious to know whether there was, in fact, any chance of recovery.

[BOAC]

It doesn't really matter. What many of us are saying is that FD 're-enable' should either be inhibited without a deliberate selection by crew OR, less desirable, it should re-engage in 'acquire selected altitude' mode, although this latter could cause problems if slow and below that altitude. Whoever decided it should just 'accept' the existing VS? Did anyone ask a pilot?

Presumably if the A/P was not inhibited also it could just re-engage and rear up to pitch for 6000fpm up? How sensible. Now, wait a minute, that rings a few bells..................:ugh:

[PJ2]

OK465;
I believe the mathematical analyses of recovery altitudes assumed a constant average nose down pitch rate (based on actual pitch rates generated for short periods from the FDR data) and a specific constant 'G' applied at a given speed on the pull-out. Correct me if I'm wrong.
In the sim exercises, for recovery the SS was held full nose-down from the beginning of the stall warning at about FL360 until the wing was unstalled at about FL250, about 40 seconds total time, with a maximum achievable ND pitch of about -12 deg with an average of -10deg. The thrust levers were in the CLB detent and the THS was initially at 13.6deg and was returning to the normal cruise setting.

With the FPV symbol available, the FPA could be observed just above initially at -40deg, (pitch -10deg).

It began to move, initially very slowly up, about 15 seconds after full ND SS;

- at 29 seconds after full ND SS, the FPA had moved from -40deg, (pitch at -11) to -25deg, (same pitch);

- in the next 5 seconds it moved from -25 to -15, (FL257);

- at 38 seconds after full ND SS the FPA was -9deg, (pitch -5deg) with the wing unstalled and the CAS at 255kts.
In practicality, I wouldn't come off the forward SS stop (with whatever extended nose down pitch rate was actually available) until I knew that I was 'flying' again.
Absolutely correct!

[DozyWannabe]

Did anyone ask a pilot?

Presumably - given the presence of pilot engineers in the people required to sign such behaviours off - yes.

Presumably if the A/P was not inhibited also it could just re-engage and rear up to pitch for 6000fpm up?

Which is exactly why, unlike the FD, the AP *is* inhibited under such circumstances.

[PJ2]

Hi Dozy;

Re the discussion with RRR on the FDs...just to clarify, when they re-engage, they synchronize with the current V/S or FPA aircraft parameter, and not with anything that is selected.

[DozyWannabe]

Re the discussion with RRR on the FDs...just to clarify, when they re-engage, they synchronize with the current V/S or FPA aircraft parameter, and not with anything that is selected.

For reference - what RRR said was:

The reference to "vertical speed selected" is what the FDs automatically acquired on automatic re-engagement.

We really need to be sure about this, because it will have had a massive impact on what the FD may or may not have been displaying.

[JD96]

One thing I haven't seen mentioned on here (only reading the latest thread), is that it took 40 seconds to call the captain after autopilot kicks off, and another minute for him to arrive. I'm not a pilot, but it seems it should be policy for the captain to be called immediately in that circumstance.

[OK465]

We are sure...:)

The select VS window on the FCU will NOT be open (i.e. the display will be blank) until the FD's return. There is no active mode until FD's are available.

The display window will then 'open' and will, on the FCU panel, display the existing VS at FD recovery, as will the FMA, i.e. +1400 VS. The FCU value & the FMA value cannot be different.

edit: BTW, in ALT2 the A/P is inhibited permanently for the remainder of the flight.

[PJ2]

Dozy;
I clarified the FD matter in post #119 (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-6.html#post7283180) with help from various documents at my disposal. While complicated to explain, the FD operation is fairly straightforward after training and some experience with the system.

It works extremely well, and there is a very good reason why the UAS memorized drill requires that they be turned off.

I suspect you're well aware that building in an "auto-shutoff", like the oft-cited issues with the stall warning NCD matter and the movement of the THS, may create new, separate problems with their own extremely-rare-though-possible risk exposures, and isn't as straightforward a solution as it may seem. It was stated many threads ago that this is a performance accident not a technical one. The issue here is performance, not system characteristics in extremely rare circumstances, for no designer can possibly expect to anticipate and then counter all possibilities and permutations of degradation and system behaviour. As I have observed many times, this is, in essence, sadly, tragically, not a complicated accident.

OK465;
The select VS window on the FCU will NOT be open (i.e. the display will be blank) until the FD's return. There is no active mode until FD's are available.Precisely.
edit: BTW, in ALT2 the A/P is inhibited permanently for the remainder of the flight.
Which clarifies BOAC's concern that the AP would engage at "+6000fpm"; It wouldn't, in ALT2B.

The AP would engage in Normal Law but, under normal protections/limits it would also ensure a smooth reduction from an obviously-too-high VS to a stable level-off or gentle climb.

In any case, (because of the Madras accident), as speed reduces, VS reverts from VS to OPEN CLIMB and the thrust reverts to SPEED.

[BOAC]

PJ - out of interest, how did you get the sim to an AoA of 40degrees? Starting recovery 'at the stall warning' would not achieve that?

[CONF iture]

- The reason for this is that we don't know precisely when they re-appeared, how long they re-appeared for, we only have a theory on what they might have displayed based on systems behaviour -
When and How long are PRECISELY known, where have you been ?
Also FD commands have been recalculated by Airbus, or call it BEA if you like.

Everything is presented on a video animation we will not see.
The animation presented during the press conference has no interest.

[PJ2]

I think the AoA was closer to 30deg, (-40 FPA, -10 Pitch), but I held the stick fully back until the stall warning and kept it back. The sim pitched down to about -2 or 3 degrees, even with power on and the THS moving towards -13.6deg. The stick was then placed fully-forward and held until it was clear the wing was flying again.

In this image, the stall warning was constantly sounding. The image of one of the recoveries may help envision the attitude, rate of descent and recovering speed even while still fully stalled:

http://www.smugmug.com/photos/i-PrSVWNM/1/M/i-PrSVWNM-M.jpg



I posted a schematic a while back and it may help as a refresher:

http://www.smugmug.com/photos/i-9NjS58r/0/L/i-9NjS58r-L.jpg

[jcjeant]

Everything is presented on a video animation we will not see.
If this video exist .. maybe this will be seen on the judicial process ...
That can be required by some parties

[Clandestino]

In the first case, I'm not sure what ALT CRZ* might have presented, but in the second case, even with +6000fpm selected, the FDs engage with an actual VS in excess of that. In that case, would the FD have commanded nose down? Dozy, recalculation of F/D commands is covered in section 1.16.5.4, graph is on page 96 of the English edition. Values on graph are shown relative to aircraft symbol on ADI, positive is nose-up, negative nose-down.

Everything is presented on a video animation we will not see.
The animation presented during the press conference has no interest. Since the stakes are pretty high, I bet video will leak, as will CVR track, eventually.

[BOAC]

There seems to be some departure from 'actual' parameters in that sim (as expected), as you describe a pitch down below the horizon with full THS and power. 447 managed to hold a high nose attitude in that situation. How much stick effort was required to hold the nose down against the thrust couple? Full forward, half?

I should clarify, to calm DW's fevoured brow, that I do KNOW the A/P would not 're-engage' - I was attempting to transfer the apparent FD 'logic' to the A/P as an example, in my opinion, of misguided design. After all, we do have enough examples of the AB A/P ACTUALLY causing a dramatic 'uncommanded' climb.

[wiggy]

One thing I haven't seen mentioned on here (only reading the latest thread), is that it took 40 seconds to call the captain after autopilot kicks off, and another minute for him to arrive. I'm not a pilot, but it seems it should be policy for the captain to be called immediately in that circumstance

Call him/her back if you must and only when it's safe to do so, but:

1. You should have two type rated pilots at the controls who are capable of handling the aircraft, with or without the autopilot and with or without the captain being on the flight deck.

2. Calling the captain (via "phone" or similar) would take one of the pilots "out of the loop", albeit briefly, at a time when both pilots should be firmly focused on flying the aircraft.

3. In any event dependant on crew rest facilities, sleep patterns and umpteen other things you may not get the captain back onto the flight deck in a matter of seconds, it will possibly/probably take several minutes, which is the reason for point 1.


AF may have failed on at least one of those points.......

[RetiredF4]

BOAC
There seems to be some departure from 'actual' parameters in that sim (as expected), as you describe a pitch down below the horizon with full THS and power. 447 managed to hold a high nose attitude in that situation. How much stick effort was required to hold the nose down against the thrust couple? Full forward, half

@PJ2
I share that concern. PF achieved a higher pitch attitude and stalled at lower speeds, mainly due to the fact that some ND SS and or reducing th NU SS input led to some g- reduction below 1.0 g without effectively reducing the pitch rate (see the Nz graphs of the respective time frame). TOGA application at that point (2nd StallWarning) and SS NU input forced a further increase of pitch without solving the speed and AOA problem. Thus when the stall finallly occured, pitch was a lot higher and speed was slower than what you describe in your sim exercise. With the nose lower like that gods g (gravity for the nonflyers) works a lot earlier than it would have for AF447, and the speed would be back in flying parameters a lot quicker.
Presently on leave on my iphone, therefore no further comments on the report.

[mm43]

Looking back at one of HN39's graphics (http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-9.html#post7154767) on post stall recovery, I was reminded of an earlier debate over "super-cooled" water. The matter has not been cleared up by the BEA as their conclusions include:-The precise composition of the cloud masses above 30,000 feet is little known, in particular with regard to the super-cooled water/ice crystal divide, especially with regard to the size of the latter. The equatorial areas of the Atlantic and the western Pacific are the spawning grounds for sometimes large tropical revolving storms. The mechanisms associated with these maritime environments and their affect on the upper atmosphere is still not fully understood.

[CONF iture]

If this video exist .. maybe this will be seen on the judicial process ...
Enough of that pseudo transparency ...
Video animation of selected recorded data is basic stuff - Where is it ?
Full data are not available to all in the judicial process - Why is that ?

Since the stakes are pretty high, I bet video will leak, as will CVR track, eventually.
How naive you can be ...
There was no such thing as a CVR track leak, there was intentional release of deformed data in order to format the opinion :

According to Amedeo from Le Figaro, the AF447 captain had stated :
On ne va pas se laisser emmerder par des cunimbs (http://www.lefigaro.fr/actualite-france/2011/08/05/01016-20110805ARTFIG00446-af-447-ce-que-les-enqueteurs-du-bea-n-ont-pas-dit.php)

But now the last CVR transcript from the BEA is :
On n’a pas été emmerdé par les cunimb hein

Completely different meaning.
I can explain if you need help.

What connection between Le Figaro and Airbus ... I let you guess.

It appears also that Fabrice Amedeo is the same guy that took part in this other piece of propaganda where the Airbus Chief Pilot himself was generously interviewed from the impressive A380 flight deck.

kXMsmPQKaps&feature=channel&list=UL

2 options for the families of the AF447 pilots :
Either they accept what's on the menu right now and try their best to resume 'normal' life.
Either they fight the system in research of the full story ...

[jcjeant]

How naive you can be ...
There was no such thing as a CVR track leak, there was intentional release of deformed data in order to format the opinion :

According to Amedeo from Le Figaro, the AF447 captain had stated :
On ne va pas se laisser emmerder par des cunimbs (http://www.lefigaro.fr/actualite-france/2011/08/05/01016-20110805ARTFIG00446-af-447-ce-que-les-enqueteurs-du-bea-n-ont-pas-dit.php)

But now the last CVR transcript from the BEA is :
On n’a pas été emmerdé par les cunimb hein

Completely different meaning.
I can explain if you need help.Yes indeed ...
But all this is weird for me (made sens .. or not)
Indeed this sentence (cunimb) is called when the plane is near Natal (the captain announces that he sees Natal just before pronouncing the sentence about cunimbs)
passing RUMBA
0 h 44 min 45
We can see Natal
ahead

0 h 44 min 49
We weren’t hassled by
cumulonimbus eh It does cunimbs they met on "en route" .. Rio-Natal ?
Curious to see a meteo graph on this route .... (I see nothing special in the TEMSI appendix 12)
Or the sens is ... "it was no cunimbs between Rio-Natal" ?
It's usual to have cunimbs between Rio and Natal ?

[hetfield]

And with 1783 fatalities in its history, according to a tally compiled by the Swiss-based website "Aircraft Crashes Record Office", Air France has been the second most deadly airline for passengers after Russia's Aeroflot.

Oops, that's harsh....

[rudderrudderrat]

Hi DozyWannabe,
but in the second case, even with +6000fpm selected, the FDs engage with an actual VS in excess of that. In that case, would the FD have commanded nose down?
Please see page 98 of the final report.
http://www.blackholes.org.uk/PP/FDs.jpg
Apart from the first 20 seconds or so when PF pulled the nose up whilst trying to keep the wings level in ALT LAW, subsequently the FDs were reasonably closely followed.

From time 02:10:50 until 02:11:40, whilst the stall warning is sounding, the FDs are commanding nose up from 7.5 degs up to 20 degs.
It would be far less confusing if the FDs had remained out of view until reselected by the pilots, or if they reappear automatically then park at zero pitch and wings level command until a pilot manually "sync"ed them to a mode they want.
If the FDs had remained locked onto ALT FL350, then they would have commanded a nose down.

I fail to see the logic of this design.

[Lonewolf_50]

The flight tests did not go beyond approach to stall. The presenters opined that recovery from the developed stall is out of the envelope and that recovery is highly doubtful, even with proper actions. i.e. certification does NOT require recovery from a developed stall.
What Owain has theorized tells me that "doubtful" is a dubious vedict. He pointed out that from the data available, THS and elevators still had lift and authority. That supports the idea that recovery is possible, but what isn't certain is the altitude penalty paid to recover. (Though some estimates can be made). As note previously, they became, once stalled, two test pilots not well briefed on what they were testing ... :( and didn't know they were now in that role. :{
It seems as if the FDs, when 'valid', were reacting to the existing rates which is not the way I expect - ie 'Flight Followers' rather than 'Flight Directors'.
Confuses me as well. Makes sense to me that FDs are to be selected OFF when UAS is encountered. Back to flying attitude and power ... old school flying.
Correct. This is probably the most confusing part about the FD logic. The FDs are withdrawn automatically during unreliable airspeeds and the FMA modes are lost. If two airspeeds erroneously agree, then the FDs will reappear with present HDG and instantaneous VS. In the confusion of the moment, it appears to me that this crew then followed these new FD modes.
The first line of the Memory items of the "Unreliable speed Indication / ADR Check Proc" AP/FD .... Off was never accomplished.
It doesn't help to solve the problem when the FDs keep reappearing with erroneous guidance.
Arrrgggh!

For PJ2, since you've spent some time actually training AB3xx pilots:
You seem skeptical that the instrument scan of the two pilots on the flight deck at the time, heavily dependent upon the FD. Do you find very many pilots who go through your training sessions to be what I might call "FD" dependent? Do the training scenarios give you the latitude to find out where their scans are strong, and where they are weak?

It would appear that if one pilot is too heavily dependent on the FD, (PF in this case), that increases the problem the other pilot has in helping the PF get back into the game. (If I am making comments to him based on a scan of nose and wings, and he is following his FD, maybe we have a chance for confusion?)
If that "FD boresight" were in progress (guessing) then my understanding of some "why did they do that" is somewhat improved.
But only partly.
PNF appears to have maintained something of an instrument scan, in re altitude at least, as he was working (in vain) to correct PF's various errors. (Note: seems that he'd have helped more by making sure the memory item of disconnecting FD was accomplished).
What many of us are saying is that FD 're-enable' should either be inhibited without a deliberate selection by crew OR, less desirable, it should re-engage in 'acquire selected altitude' mode, although this latter could cause problems if slow and below that altitude.
Seems that the former is the more desirable.

[PJ2]

Hello Lonewolf_50;

I'm on the road at the moment and need some time to compose a response, as well as respond to RetiredF4's observations.

[john_tullamarine]

The flight tests did not go beyond approach to stall

Certification requirements have varied over the years. One always needs to check the certification basis for a given aircraft and, even then, it is not guaranteed that a variation wasn't agreed upon during the program.

As I recall, the 744 may have traded on the basis of the earlier models.

As to what the OEM ought to investigate, over and above the Standards, might be another matter.

[OK465]

The flight tests did not go beyond approach to stall

Makes me wonder why I did 3 QTG's recently that encompass 'the stall', as validated by IAS, buffet onset, stall AOA, and VSI break? QTG's come from flight test data.

There is a big difference between 'the stall' and a 'developed' (better word, aggravated) longer term condition.

One always needs to check the certification basis for a given aircraft...

as JT says. :ok:

[gums]

Wondering why we are talking about "pitch rate" command versus "pitch" command. Can't command a rate directly, nor pitch itself, so to get a "pitch" value you must hold the stick fore or aft to get there, then adjust because the 'fuser is still trying to command a gee value - nominal one gee corrected for pitch attitude. Am I reading the manual wrong?

That being said, what in the hell are the pilots doing trying to follow the FD's? That's one theory out there on the streets, from what I have read.

I have always felt that a constant nose down attitude and some power to gradually fly out of the stall that the jet experienced would have been possible. 5 degrees, 10 degrees, no matter. Very glad a few have tried it in the sim or calculated the required maneuver. The jet does not have a pitch coefficient moment as we had in the Viper at 40 or 50 degrees AoA that prevents a nose down pitch moment using elevators and the THS.

If there is one thing about our primitive FBW system, it was a force transducer versus a position transducer for pitch and roll commands. So to hold a pitch attitude other than what Otto was trying to achieve to meet the gee command ( trim gee not a default of one gee), we had to exert "x" pounds. Releasing the stick commanded Otto to resume the trim command we could set. The 'bus does not allow the pilot to command a trim gee. So the pilot has to hold the stick fore or aft to get away from that one gee default trim condition. This feature was rather intuitive, despite lack of movement. To fight nose up trim we had to push forward, and vice versus.

This is still a great thread for discussion, and I am honored to be able to bitch and moan and contribute amongst all the commercial pilots here.

[mm43]

Lonewolf_50;... seems that he'd have helped more by making sure the memory item of disconnecting FD was accomplished.In that context, "We've losts the speeds" doesn't appear to have had any relevance to "IAS doutuese", and as that item wasn't sought in the QRH (at least no mention made), the PNF became concerned with -
(a) how the aircraft was being handled;
(b) the necessity to get the Capt back ASAP.
Unfortunately, the whole episode can be placed into similar categories -


Lack of training in high altitude UAS procedures
Lack of training in high altitude handling
Lack of CRM training.

Having said that, I and others have noted that a deviation would have resolved any issues, and we would have all continued on blissfully unaware that this accident was still waiting to happen.http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/icons/mpangel.gif

[Linktrained]

Until they passed 10,000 ft. there appears to have been no comment on their direction of travel... DOWN.

This was indicated ( and recorded). But it was not NOTICED by the pilots.

The presentation of this information might be improved.

( Seeing the hands of my old "Sensitive Altimeter" going round would have caught MY eye...)

( The lack of recognition of " STALL" has been discussed.)

[Indarra]

The flight tests did not go beyond approach to stall. The presenters opined that recovery from the developed stall is out of the envelope and that recovery is highly doubtful, even with proper actions. i.e. certification does NOT require recovery from a developed stall.

Until they passed 10,000 ft. there appears to have been no comment on their direction of travel... DOWN.

This was indicated (and recorded). But it was not NOTICED by the pilots.

The presentation of this information might be improved.


Get the feeling that BEA doesn't want to dwell to much on areas which could be the basis of claims against Airbus.

[Owain Glyndwr]

i.e. certification does NOT require recovery from a developed stall.

Final Report section 1.18.1.1

Regulatory aspects The A330 meets the requirements of the regulations in force – that is to say JAR 25 changes 13 or 14 and the special conditions imposed by DGAC – at the time the type certification application was made.

JAR 25 Change 13

JAR 25.201 (c) (2) As soon as the aeroplane is stalled recover by normal recovery techniques

My emphasis. BEA were just stating the facts

[DozyWannabe]

Get the feeling that BEA doesn't want to dwell to much on areas which could be the basis of claims against Airbus.

Where does this come from? The BEA pulled Airbus up on the certification of the pitot tubes and the SB rather than AD approach with which they were to be replaced. Airbus was served with notice of intended action for manslaughter along with AF.

The BEA are *not* interested in protecting Airbus (nor should they be) and never have been.

[Indarra]

Where does this come from? The BEA pulled Airbus up on the certification of the pitot tubes and the SB rather than AD approach with which they were to be replaced. Airbus was served with notice of intended action for manslaughter along with AF

OK. Doze, I’ve been a little too cryptic.

The stall recovery issue
A number of respected posters (such as PJ2 #127, #145, #165 and Owain Glyndwyr #148, #149 and there are others) have made a case for the possibility that the aircraft could have been recovered after the stall. BEA is in effect saying that it is only interested in what happened until departure from the flight envelope. It’s saying that while maybe or maybe not the aircraft would have been recoverable subsequently, the issue is, in effect irrelevant, because it didn’t cause the departure from the flight envelope.

What I want to say was the failure to attempt the stall recovery was another hole in the cheese, and logically shouldn’t be dismissed so easily by the BEA. Stall recovery surely is another part of the backup offered by having human pilots as the final resource. And just maybe, just possibly, the reason why the BEA is not interested is because it raises the question of the inverted stall warning. To have included a recommendation about the inverted stall warning could place Airbus Industrie under GREATER legal pressure.

The non-recognition of altitude loss
Similarly a couple of posters have expressed surprise that the BEA’s report does not particularly pick up the crew’s evident ignorance of the descent down to 10,000. Some have made the suggestion that they only noticed when one digit came off the digital display. Again, I am wondering, ever so gently, whether the failure to highlight this disadvantage of a digital altimeter versus an analogue one, was also influenced by a BEA desire to keep FURTHER pressure off Airbus Industrie.

Caveat
There are a lot of pages to read, and I haven’t had the time to absorb everything, but think the above thoughts, which seem to share something with JCJeant, might be worth injecting.

[DozyWannabe]

The BEA does address the issue with the stall warning inhibition.

"A few seconds after the transition to alternate law, the stall warning sounded briefly, even though the PF’s inputs should have made this warning sound for several seconds. The reason for this is the drop in the measured airspeeds, some of which fell temporarily to below 60 kt, while the angle of attack reached 40°. Furthermore, the drop in measured airspeeds to values of less than 60 kt during the stall caused the repeated activation and deactivation of the warning which may have made it considerably more difficult for the Captain to effectively analyse the situation on his return to the cockpit."

The presentation also stated that while recovery at a later stage *may* have been possible if the crew had advanced handling training, the fact that none of them did rendered a recovery very unlikely.

Quite some time ago I stated a belief that the inhibition of the stall warning below a certain speed was very unlikely to be Airbus-specific. This is something I still believe quite strongly.

[HazelNuts39]

To have included a recommendation about the inverted stall warning could place Airbus Industrie under GREATER legal pressure.
The recommendation is stated on page 214 of the Final Report:
When airspeeds are below 60 kt, the stall warning is no longer available, even though it may be beneficial for it to be available at all times.
Consequently, the BEA recommends that:
€€ EASA require a review of the conditions for the functioning of the
stall warning in flight when speed measurements are very low.
[Recommendation FRAN‑2012‑051]

[BOAC]

Indarra - I believe BEA are correct to focus on 'how they got there' rather than 'what they did then', since there was ample evidence of a stall both in the cockpit warnings PLUS surely the basic knowledge that if you 'zoom' at high level you will run out of the big skyhook.

There should never have been ANY need for 'advanced' recovery experience, since proper control of the a/c AND recognition of and an appropriate response to the zoom and stall warnings would have avoided the 'flop' into the high AoA stall they created. Surely the aim MUST be to have pilots who can react correctly to the initial flight path divergence rather than giving training in recovering from an extreme situation.

Regarding the altimeter presentation - even given that the 'digital' display is less intuitive than the analogue dial, I still find it hard to accept that the sight of the numbers in the box spinning rapidly (does it really matter which way?? - it should NOT be happening, whichever way) did not jerk them into looking at what was happening.

[syseng68k]

> Quite some time ago I stated a belief that the inhibition
> of the stall warning below a certain speed was very unlikely
> to be Airbus-specific.
> This is something I still believe quite strongly.

Just because you believe it, doesn't make it good system
design. Rather the opposite in that if the a/c is stalled
at 60 knots, then it's definately still stalled below this.
Common sense suggests that the logic should be that if the
system detects a trend downwards in airspeed that goes
through the stall warning and then on past the 60 knot limit,
the warning should stay in place until the system data is
known good and the a/s reaches a safe level. Put another way,
if the system knows that the a/c is stalled, it should assume
the worst if it has less data to work with subsequently. It's
almost as though some back room systems engineer thought:
"The sensor data is bad, so logically, we must inhibit the stall
warning", conveniently missing the whole point of the
exercise.

The success of any automated system comes down to: How intuitive
is it in use; How accurately and consistently does it communicate
current system state to human operators; How gracefully does
it degrade beyond the design limits. No matter what the report
says, I think many at AB will be peddling furiously underwater
for quite a while :-)...

Regards,

Chris

[overthewing]

Can I pose a possibly naive question for pilots who fly long-haul routinely?

Cockpit manning was in three shifts, which seems standard for the length of the flight.

The Captain was PNF for the first shift. He was off-duty for the second shift. However, before he left the flight deck, he asked which of the two co-pilots was going to be landing the plane, and I assume the answer was the second co-pilot, who had just completed his rest.

So the Captain hadn't assigned himself any flying at all.

Is this usual? For the commander not to get his hands on the controls at any stage of the flight?

[Owain Glyndwr]

Consequently, the BEA recommends that:
€€ EASA require a review of the conditions for the functioning of the
stall warning in flight when speed measurements are very low.
[Recommendation FRAN‑2012‑051]

Already done - CS25 Amendment 6 25.207 (c) - introduced after AF447 reads:

Once initiated, stall warning must continue until the angle of attack is reduced to approximately that at which stall warning began. (See AMC 25.207(c) and (d)).

This effectively would prohibit any speed related cut off of warning

[DozyWannabe]

Just because you believe it, doesn't make it good system design.

I never said it was!

The point I was getting at was that not only was there a clear reference to the speed-based inhibition in the report (which made the assertion that the BEA was covering for Airbus's system design incorrect), but also that if other manufacturers' types exhibit similar behaviour, then again it relates to a design issue in general and not one specific to Airbus.

Now, according to the report this aspect of the design appears to have been instituted because of potential failures of the AoA vanes at takeoff leading to a false stall warning - which would present a hazard close to the ground (this also means that the suggestion of adding WoW switch to the trigger inputs wouldn't work). Essentially this accident has provided a secondary worst-case scenario where the inhibition can mislead a troubleshooting process. You and I both know this is complicated stuff, don't we? :)

(Which reminds me - I should pick up my 68k assembler revision soon...)

[rudderrudderrat]

Hi DozyWannabe,
Now, according to the report this aspect of the design appears to have been instituted because of potential failures of the AoA vanes at takeoff leading to a false stall warning - which would present a hazard close to the ground (this also means that the suggestion of adding WoW switch to the trigger inputs wouldn't work)

I don't follow that logic.
If the stall warning triggers with airspeeds >60 kts, then why not simply suppress the nuisance warnings on the ground when the airspeed is <60kts AND WoW?

[HazelNuts39]

Owain Glyndwr;

I think the quoted sentence was introduced with JAR-25 Amendment 96/1, effective 19.05.96, incorporated in Change 15 dated 1 October 2000. It must be read in conjunction with the provision you quoted earlier, that in the demonstration of stall characteristics recovery is initiated as soon as the airplane is stalled.

Furthermore, FAA Advisory Circular AC 25-7A dated 31/3/98 states:
"If artificial stall warning is provided for any airplane configuration, it must be provide for all configurations, and continue throughout the stall until the angle of attack is reduced to approximately that at which stall warning was initiated." and -
" Stall warning tests are normally conducted in conjunction with the stall testing required by 25.103 (stall speeds) and 25.203 (stall characteristics)."

[DozyWannabe]

@rudderrudderrat:

I'm thinking of the worst-case scenario where ADIRU or pitot tube failure occurs at or just after rotation. If you're going to inhibit based on WoW, this potentially opens a can of worms. A spurious SW at FL250+ is one thing, but it's even more deadly on climbout.

In general, when making amendments to complex systems behaviour it is important to ensure that providing a solution for one failure mode does not adversely affect the solution for existing failure modes.

[rudderrudderrat]

Hi DozyWannabe,

Sorry - I must be a bit dozy. I still don't understand.
The stall warning is triggered when measured Alpha exceeds some threshold. Alpha > X. The vanes are unreliable in airflow less than 60 kts. Therfore:
1) Inhibit when IAS <60 kts = No good for AF 447 scenarios.
2) Only Inhibit IF IAS <60 kts AND WoW, else Shout when Alpha > X

Why would 2) make a false stall warning on climb out more likely?

[jcjeant]

Now, according to the report this aspect of the design appears to have been instituted because of potential failures of the AoA vanes at takeoff leading to a false stall warning - which would present a hazard close to the ground (this also means that the suggestion of adding WoW switch to the trigger inputs wouldn't work)Adding a layer :)
At less than 60 knots ... even on takeoff .. you are on the ground not close to the ground .. so no hazard
And at 70 or 100 knots .. you are alway on the ground
Sorry but I don't understand the logic of this design ... (60 knots)

[DozyWannabe]

Why would 2) make a false stall warning on climb out more likely?

If air data failure causes a read of <60kts and the weight comes off the wheels. It's an edge case for certain, but probably needs to be considered.

[EDIT : Hold up - I see what you're saying. You're talking about WoW *in addition* to <60kts. My memory may be playing up, but I think some were proposing ditching the speed requirement entirely and using WoW instead. ]

[Owain Glyndwr]

HN39

OK, thanks, I didn't have the documentation to check back exactly when it appeared in CS25, but on checking back I see that JAR25 Ch 13 has the same wording, but with one important difference:

Stall warning must continue throughout the demonstration until the angle of attack is reduced to approximately that at which stall warning is initiatedIf you read that with the requirement that stall recovery is to be initiated promptly then one can see why the designers didn't cover the case of an aggravated (I like that description) stall. Without "throughout the demonstration" they would have to cover the AF447 situation. - at least that would be my interpretation of the rule.

[CONF iture]

Once initiated, stall warning must continue until the angle of attack is reduced to approximately that at which stall warning began. (See AMC 25.207(c) and (d)).
Owain Glyndwr,
It was in the FCOM for a long time : here (http://www.pprune.org/tech-log/454653-af-447-thread-no-4-a-30.html#post6545680)

[rudderrudderrat]

Hi DozyWannabe,
You're talking about WoW *in addition* to <60kts. ... but I think some were proposing ditching the speed requirement entirely and using WoW instead.
Correct. The TriStar crash at JFK was partly caused by a false stall warning as the weight came off the wheels. All they had to do was hold 12.5 degs pitch and climb away.
ASN Aircraft accident Lockheed L-1011 TriStar 1 N11002 New York-John F. Kennedy International Airport, NY (JFK) (http://aviation-safety.net/database/record.php?id=19920730-0)

The best logic would surely be:
only inhibit whilst on the ground AND if IAS <60 kts Else Shout.

[Owain Glyndwr]

CONFiture

OK - thanks for that info.

[HazelNuts39]

Owain,

The most recent version of the FAA Flight Test Guide, AC 25-7C, dated X/X/2012, has this:
(c) Consistency. The stall warning should be reliable and repeatable. The warning must occur with flaps and gear in all normally used positions in both straight and turning flight (§ 25.207(a)) and must continue throughout the stall demonstration until the angleof-attack is reduced to approximately that at which the stall warning was initiated (§ 25.207(c)).
I tend to think that, if your interpretation of the rule had been intended, then that meaning would have been stated more explicitly.

[Peter H]

Hi,

Trying to control the stall-warning with a context-free rule is likely to be very difficult/unrewarding.

It's much easier to use some sort of finite-state-machine.

Minimal version might be something like:

State: SW_OFF
....if ( AoA_excessive & AoA_trusted) then goto SW_ON

State: SW_ON
....if ( AoA_acceptable & AoA_trusted) then goto SW_OFF

where:
AoA_trusted is true if speed > 60kts

[infrequentflyer789]

Hi DozyWannabe,

Sorry - I must be a bit dozy. I still don't understand.
The stall warning is triggered when measured Alpha exceeds some threshold. Alpha > X. The vanes are unreliable in airflow less than 60 kts. Therfore:
1) Inhibit when IAS <60 kts = No good for AF 447 scenarios.
2) Only Inhibit IF IAS <60 kts AND WoW, else Shout when Alpha > X

Why would 2) make a false stall warning on climb out more likely?

How exactly does (2) work ?

The issue is that when IAS < 60kts Alpha = NaN (or NCD or whatever invalid indication). This happens before the SW computer.

So, is NaN > X or not ? That is the issue the SW logic has to decide.

You can't just fix the SW logic, in any meaningful way. The input data simply isn't there in this scenario.



You could maybe give the SW memory so it uses last-valid value, which would catch the 447 scenario - but that adds complexity and failure modes there.

Or you route raw AoA around the ADIRU for SW purposes - which is I think what the BUSS solution does (as a side effect of its main job) ?

[syseng68k]

Dozywannabe, #201

You and I both know this is complicated stuff, don't we? http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif
There are other sources that could be used as well. Ground speed,
altitude and vertical speed are in theory available from the ins,
which is completely independent of the air data system. Such data
could be used for a sub level sanity check of the air data system.
If the adr disagree and drop out, there is a historical trending
relationship between ins ground speed and adr air speed, which will
be valid short term as degraded data. Whether this is used in the
330 is not known, but it doesn't seem to have been available in any
form to the crew or the stall warning functions.

For stall warning inhibition on the ground, ins data is arguably
a far more relevant source than anything else and wouldn't
require any wow detection ?...

[Owain Glyndwr]

I tend to think that, if your interpretation of the rule had been intended, then that meaning would have been stated more explicitly.

Maybe Hazelnuts, and it may be just me, but I am still stuck with the change to the European rules (and EASA are the more directly affected) - why make that change if they did not mean something by it? They don't usually change long standing wording on a whim. Perhaps FAA just haven't caught up yet - and you know as well as I that there is often a time gap between US and European certification changes.

[dinbangkok]

First up - I'm a regular member of the SLF community. The closest I can claim to understanding the intricacies of what happened on AF447 other than as a layman is a psychology degree (from Manchester University when a certain Swiss cheese theory Jim Reason was at the helm of the Psychology Department). I've been following the discussions on here since the incident in 2009 - thank you for everyone, irrespective of what side of the fence you're on with regard to the unending man vs. machine automation debate. It's been illuminating, fascinating and reassuring to see the unfortunate event dissected and debated by professionals from all walks of life. One hopes that through debates like these, things can only get better.

So my tuppence for what it's worth... From my understanding of the report (which I think overall reads as thorough and even handed), clearly there were some issues in terms of BOTH crew resource management and ergonomics in times of high stress, but the thing that screams out to me as fundamentally wrong in terms of 'how can this be!', is on page 192 of the report: The copilots had not undertaken any in-flight training, at high altitude, for the “vol avec IAS douteuse” procedure or on manual aeroplane handling I find that fact absolutely terrifying - irrespective of how automated the plane is I would have thought that advanced manual airmanship skills should be mandatory for any commercial pilot, irrespective of altitude!. Indeed I can't help but notice a correlation between the well publicised potentially fatal incidents which have been averted, thanks to the fantastic skills and experience of the pilot. Notable of course (and a completely unrelated incident), is of course the one on the Hudson where the pilot was a keen glider. Everyone travelling on that flight was obviously very lucky to have that particular pilot at the controls, but surely we should be looking to reduce the role of 'luck'. But what do I know...

So my question for the pilots out there: Could airlines ever be persuaded to go back to basics and do more to boost the manual flying skills of commercial pilots, irrespective of the level of automation on a designated aircraft?... Indeed completely change the structure of training so that when training on a specific aircraft, pilots start 'manual', with automation added, layer by layer? (adding layers to the onion so to speak)... Ultimately, so that every pilot is confident (relatively speaking), and knows what it feels like, to fly said aircraft when controls / automation have gone t*ts up?

Excuse my ignorance and sorry for interrupting - I'll continue lurking for now. Many thanks again for everyone's contribution

[HazelNuts39]

why make that change if they did not mean something by it?There were substantive changes to that paragraph. It is entirely possible that deletion of the words 'througout the demonstration' was thought to be editorial, non-substantive. In any case, those changes had nothing to do with AF447.

Perhaps the condition that all three AoA values are NCD while the airplane is in flight should be considered a failure of the stall warning system:

228. Design and Function Of Artificial Stall Warning and Identification Systems.
d. Indicating and Warning Devices.
(2) Warning that the associated systems for operating the stall warning or stall identification devices has failed should be provided. As far as is practicable, this warning should cover all system failure modes.

[henra]

The issue is that when IAS < 60kts Alpha = NaN (or NCD or whatever invalid indication). This happens before the SW computer.

So, is NaN > X or not ? That is the issue the SW logic has to decide.

You can't just fix the SW logic, in any meaningful way. The input data simply isn't there in this scenario.


Hmm, I'm afraid you might be quite on the mark with this objection. This could very well be the reason why they implemented this less than ideal solution.
Circumnavigating the ADIRU in certain instances while going through it normally might open up new cans. (Additonal mini ADR required with possible discrepancies to main ADR's requiring redundancies and another Error Handling logic...)

From a boolean perspective a solution seems possible and even not too complicated but it might indeed conflict with their basic system design necessitating less than ideal workarounds causing other trouble.
Will be interesting to see if, when and how they can fix this.

I seem to remember that Boeing does have a similar logic of suppressing the warning if the speeds are too low. Anyone any idea if they are working on that topic as well?
Do they also calculate SW behind the ADR modules (which normally makes a lot of sense as you would otherwise need an additional mini ADR unit to convert the Raw data in a usable format just for the Stall Warning alone).

[Peter H]

infrequentflyer789

You can't just fix the SW logic, in any meaningful way.

I beg to disagree, see post #213

The input data simply isn't there in this scenario.

Yes, you do not have a meaningful value for AoA (here represented by a NaN), so cannot use it in a context-free rule to indicate if the stall-warning should be sounded.

You could maybe give the SW memory so it uses last-valid value, which would catch the 447 scenario - but that adds complexity and failure modes there.

As you say, remembering any previous sensor value (e.g. AoA ) leads to extra complexity and failure modes.

However holding the current state of the stall-alarm would not introduce such problems.


In "IEEE FP speak" my AoA_trusted and your AoA are related by: AoA_trusted = NOT(isNaN(AoA)).

[Turbine D]

Indarra,

The stall recovery issue
A number of respected posters (such as PJ2 #127, #145, #165 and Owain Glyndwyr #148, #149 and there are others) have made a case for the possibility that the aircraft could have been recovered after the stall. BEA is in effect saying that it is only interested in what happened until departure from the flight envelope. It’s saying that while maybe or maybe not the aircraft would have been recoverable subsequently, the issue is, in effect irrelevant, because it didn’t cause the departure from the flight envelope.


IMO, the role of the accident investigation authority (BEA, NTSB, etc.) seems to be misunderstood at times. Their role is to investigate accidents with the sole objective of improving aviation safety. To do this they:
- Obtain and assemble factual information regarding the accident
- Analyze the factual information
- Reach a conclusion on findings of the cause or probable cause
- Make safety recommendations.

Now granted PJ2 and Dozy did some SIM work to look at whether or not recovery was possible (it appeared to be) and Owain Glyndwr did analysis depicted in graphical charts which indicated recovery was theoretically possible. However, this is not information that can be construed factual unless actual flight trials were conducted in an A-330-200 aircraft to support/confirm the theoretical findings of SIM and analysis. For example, the AA Flt.191 out of ORD went down in an asymmetrical stall shortly after liftoff. The NTSB never addressed if the plane could have been recovered satisfactory but concentrated, based on factual investigation how the accident got to this point in the first place. Afterwards, at least two university studies concluded the plane was recoverable. However, approximately 30 pilots when confronted with the problem in a SIM failed to recover the airplane. This is why speculative information or theory based information shouldn't enter into a failure report out, it could be right or it could be wrong.

The non-recognition of altitude loss
Similarly a couple of posters have expressed surprise that the BEA’s report does not particularly pick up the crew’s evident ignorance of the descent down to 10,000. Some have made the suggestion that they only noticed when one digit came off the digital display. Again, I am wondering, ever so gently, whether the failure to highlight this disadvantage of a digital altimeter versus an analogue one, was also influenced by a BEA desire to keep FURTHER pressure off Airbus Industrie.

Digital verses Analog - Well, take a look at the NW B-727 accident during climb out of JFK on December 1, 1974, also a stall accident. In this accident the analog altimeter didn't help either. In fact, I wonder if, at that time, digital altimeters were available, if some people would have concluded a digital altimeter would have helped.

Just some thoughts to consider....

[Owain Glyndwr]

Their (BEA) role is to investigate accidents with the sole objective of improving aviation safety. To do this they:
- Obtain and assemble factual information regarding the accident
- Analyze the factual information
- Reach a conclusion on findings of the cause or probable cause
- Make safety recommendations.

Now granted PJ2 and Dozy did some SIM work to look at whether or not recovery was possible (it appeared to be) and Owain Glyndwr did analysis depicted in graphical charts which indicated recovery was theoretically possible. However, this is not information that can be construed factual unless actual flight trials were conducted in an A-330-200 aircraft to support/confirm the theoretical findings of SIM and analysis............This is why speculative information or theory based information shouldn't enter into a failure report out, it could be right or it could be wrong.

100% with you :ok:

Hazelnuts
It is entirely possible that deletion of the words 'througout the demonstration' was thought to be editorial, non-substantive. In any case, those changes had nothing to do with AF447.

As I said, it maybe just me, and it's certainly not worth a lot of discussion, but regardless of whether they intended it to be just editorial, for me, as a one-time designer, that editing changes the S/W duration requirement from conditional [i.e.linked to a prescribed demonstration technique] to mandatory without explicit or implicit time limits. But as I said its not worth an argument.

I don't really see why the logic that AoA vanes are not reliable below 60 kts should have any effect on problems with untoward stall warnings near lift off. Unreliable AoA signals because of dynamic effects yes, but that is a different problem.

With my interpretation of CS25 if it is flying you believe the AoA signal(s) and latch the S/W until the AoA comes back below the threshold and is confirmed to be so. Airbuses have a logic that changes the laws from ground to flight modes, so why are people debating complicated 60 kt and WoW combinations?

[Lonewolf_50]

Turbine D: Well said!

This is why speculative information or theory based information shouldn't enter into a failure report out, it could be right or it could be wrong.

[mm43]

Just as a matter of interest and to get away from the WoW debate; does the AoA < 60 KT actually represent unreliable AoA vane angles at sea level or maximum service ceiling? I have feeling it may well be the latter.

Any takers?

[PJ2]

Turbine D, Re, "
Now granted PJ2 and Dozy did some SIM work to look at whether or not recovery was possible (it appeared to be) and Owain Glyndwr did analysis depicted in graphical charts which indicated recovery was theoretically possible. However, this is not information that can be construed factual unless actual flight trials were conducted in an A-330-200 aircraft to support/confirm the theoretical findings of SIM and analysis. For example, the AA Flt.191 out of ORD went down in an asymmetrical stall shortly after liftoff. The NTSB never addressed if the plane could have been recovered satisfactory but concentrated, based on factual investigation how the accident got to this point in the first place. Afterwards, at least two university studies concluded the plane was recoverable. However, approximately 30 pilots when confronted with the problem in a SIM failed to recover the airplane. This is why speculative information or theory based information shouldn't enter into a failure report out, it could be right or it could be wrong."
Also 100% with you!

Re your earlier comments on the differences in our own sim stall exercise and the way AF447 was handled, yes, ours was a far more brisk pull-up and the comments you and BOAC offered ring true.

[Lyman]

mm43. Are you saying that the actual AOA may have been greater than 45 degrees? Perhaps much greater?

[Diversification]

In one of the the preliminary reports it was hypothised that this msg was caused by an attempt of the pilots to shut down one or both of the affected computers.
"02:11:55 - .1/FLR/FR0906010210 27933406EFCS1 X2,EFCS2X,,,,,,FCPC2 (2CE2) /
WRG:ADIRU1 BUS ADR1-2 TO FCPC2,HARD
"
Now the data should be available to either refute or verify this assumption, but I have not found anything about it in the final report. Did I miss it?

Regards

[Machinbird]

Just a reminder that way back, I did a test with an airline type AOA vane using the hand out the window trick in my car. It came alive at less than 20 mph!

They really don't take much wind speed to activate. 60 Knots might relate to reliable airspeed measurement issues. The key issue is that AOA data is valid in its own right and should never be controlled by airspeed as to whether it is considered valid.

As we see with AF447, they had well over 100 knots airspeed on the way down, it just wasn't being directed into the pitot tubes.:*

[HazelNuts39]

does the AoA < 60 KT actually represent unreliable AoA vane anglesIt may be more a question of accuracy than of reliability.

[NeoFit]

Machinbird

With all respect due, your "hand out the window" AoA car vane test was'nt done witht a -50 degre TAT.

However, I agree.
It's seems to me that AoA vanes effective range is plus or minus 50 degre
(AFAIR).
(and I am sorry coming back with Tarom 1994 event: the plane was stalling with a quite vertical attitude, but the recorded AoA was 'only' 45 degre. Sure, real AoA was out of range).

Best regards

[mm43]

It may be more a question of accuracy than of reliability.Or is it the angle at which valid CAS is no longer calculated?

Machinbird;

Thanks for reminding us about your experiment. I know the original reason given for the AoA vane invalid @ < 60 KT was to prevent spurious SW in the approach and departure regimes, but it has now been demonstrated to be confusing when the envelope gets "extended".

[HazelNuts39]

Or is it the angle at which valid CAS is no longer calculated?Say again???

[mm43]

Say again??I certainly cocked up that question!

I actually meant that when CAS of < 60 KT was calculated, the ADRs deem that the AoA vane angle can no longer be relied upon. In other words I answered my own question.:ouch:

[HazelNuts39]

Lyman,

At the end of the recording the flight path angle relative to earth was -45.2 degrees, and the pitch attitude was +16.2 degrees. In still air those values would correspond to an AoA of 61.4 degrees. With a tailwind component of 24 kt the AoA could have been about 70 degrees.

[bubbers44]

Does everyone agree that at FL350 when they lost airspeed and autopilot they should not have pulled up to a 14 degree deck angle and stalled the airplane? If they hadn't done that and had done what any experienced pilot would do and hold attitude and power and get appropriate UAS check list we wouldn't be discussing this now.

If they did stall at 38,000 any competent pilot could recover from a stall and not crash unless for some strange reason he thought holding full or almost full back stick would help him recover. Please tell me no pilot here would do the same thing they did.

[john_tullamarine]

If they .. had done what any experienced pilot would do and hold attitude and power and get appropriate UAS check list we wouldn't be discussing this now.

Probably we are all agreed on that point.

any competent pilot could recover from a stall

One might hope that such would be the case.

However, there is, at least, one caveat (and I note I have no background on the Airbus flock).

While some of our number have had the opportunity to experiment in sim exercises with an indication that recovery might have been possible, we note that the beloved sim is a computer not an aeroplane. The observed sim characteristics are only as good as the aeroplane model programmed and this in an area of the envelope where the model would be expected to consist of extrapolations rather than hard FT data.

There remains the question of just what real world (stability) characteristics the particular aircraft might have had in the circumstances, hand flown at high FL without the computers' assistance. The CG was fairly aft at around 29% (as I recall) and recovery from a deeply stalled situation may have presented a crew with some unusual or unexpected problems. While many may censure the crew and the particular operator's training systems for getting to the stalled situation in the first place, it may be appropriate to cut the guys in the hot seat some slack so far as "oh dear (or words to that effect), what do we do now ?" might be concerned.

Different matter for an experienced experimental TP but we are talking about two line F/Os who (so far as I am able to divine) had no broader experience. Indeed, there are some very experienced TPs who frequent this place and, with any luck, we may get some pertinent comments from those good folk.

Ultimately it will be interesting to see if AB provides useful guidance on the matter ?

[mm43]

Diversification;Unexplained ACARS WRG msgNo, you didn't miss it!

The possible solution was the answer posited by A33Zab to Svarin in AF447 - Thread No.3 (http://www.pprune.org/tech-log/452836-af447-thread-no-3-a-97.html#post6511019) , and physical evidence effectively vanished at impact.

I can only assume that as the BEA couldn't substantiate the message, and in determining it had no effect on the outcome, they decided to leave it as described in Interim Report No.2.

[RatherBeFlying]

That is a possible surmise from BEA's report and webcast.

But do we really expect a crew that ends up in a developed stall and later realises the situation to simply accept their fate in an intact airframe at better than FL300? Is that acceptable to the SLF population?

Stick pushers were once required in transport a/c that could not recover from a stall -- why has that requirement apparently been dropped?

[rudderrudderrat]

Hi JT,
There remains the question of just what real world (stability) characteristics the particular aircraft might have had in the circumstances, hand flown at high FL without the computers' assistance.
I have been pondering the same thing ever since the first report was received.

The computers gave the crew direct Roll Control with the ailerons and spoilers, but they retained the management of the position of the elevator and stabiliser.
I think that without the computers' assistance, the crew would have had to trim the load from the elevator themselves as the speed washed off during the stall warning and probably the crew would have had to reprogram their own flight directors to a positive VS (if that is what they really wanted).

[HazelNuts39]

Stick pushers were once required in transport a/c that could not recover from a stall -- why has that requirement apparently been dropped? That requirement is still in force, but we don't really know if the airplane was unable to recover from a stall.

[Sriajuda]

While it appears a mystery to almost anyone as to why all three pilots seemed unable to recognize the stall, I wonder even more about the apparent lack of the computer's abilities to detect the same.

Even with the speed sensors gone or unreliable, there is ample information remaining to deduct (heuristically) that indeed, the AC was in a stall. From a system engineer's point of view, I perceive a gross discrepance between automation behaviour *before* leaving the predefined, valid flight envelope, and thereafter. Before, there is protection from all sorts of (possibly) stupid control inputs by the pilots, but as soon as a single sensor fails, the whole protection system just quits. That is highly inconsistent behaviour and might, IMHO, explain the actions of the PF. He might just have been too used to the plane doing the actual flying, and he might have expected it to do what he was used to: Interpret his stick inputs as a "goal" definition (climb!) and do the actual flying to achieve that goal.

I understand that the AC had switched to 'alternate law', and that maybe the pilots or, to the very least, the PF might have been unaware of that. The point I want to make is that I see no need for such an abrupt cessation of computer support in that situation. Three minutes is a very long time, much more so for computers. Heuristics looking at all sensory data could have determined, with reasonable accuracy,

- airspeed (correlate previous, valid readings with GPS speed and accelerations measured vs. change in pitot sensor data)
- vertical speed (sensory data was good, AFAIK, barometric and ground radar, no?)
- aircraft attitude (AI was working, no? An even if not, over some period of time it could be deduced just by observing the acceleration data in all three axis)

Using that data would be sufficient to detect the stall. Even more important, such heuristical cross-checking of sensory data by the computers could have avoided both the switch to alternate law *as well as the stall*. Even if the heuristic analysis was not good enough to safely fly the aircraft, the computer could just as well have fallen back onto pitch & power by itself. Of course, alerting the crew to the fact at the same time. Giving them the *option* of manual takeover (including a *manual* switch to alternate law), rather than just quitting and leaving them to sort it out.

Humans are not computers, and are extremely suspectible to fatigue, habits, boredom, surprise and panic. If you wanted to design a system that had the goal of provoking 'human error', these are the human weaknesses you'd exploit. And that is exactly what the airbus did: Lull the pilots into a seemingly fool-proof, fully automated environment, and then, at a slight (!) malfunction of hardware, drop everything raw onto them, intermingled with inconsistent alerts and warnings.

I think these are major user-interface flaws. Sure more/better pilot training is called for, too. But the system's design should strive to be intuitive rather than that additional/repeated training is required just to be able to deal with the system's behaviour.

The same goes for the airbus sidestick configuration: It seems to be designed with the goal of making sure the two (and sometimes a third!) pilots are unaware of what the other is doing. Out of each others sight, the passive one not moving, averaging dual inputs...I just don't get that. Does anyone here think that the captain was aware of what the PF was doing?? And to think how easily that could have been different, with a different setup.

Also the change to alternate law could, nay, should be combined with force-feedback sticks. In humans, not all the senses are equal. They get processed in different priorities. These are:

1. Smell
2. Taste
3. Touch
4. Aural
5. Visual

We can't make much use of 1 and 2, but rather than displaying a small text on a screen (5, lowest priority), why not use no. 3? The change from non-force feedback to force feedback would very distinctly signal the change from 'normal' to 'alternate' law to the PF!

Just a systems engineer's thoughts about the issue(s), who has done very little flying (albeit a lot of sailing).

[NARVAL]

"Different matter for an experienced experimental TP but we are talking about two line F/Os who (so far as I am able to divine) had no broader experience"
Thank you John Tullamarine, for that comment. One must remember, beyond the fact that the pilots had probably never experienced "out of the flight envelope" excursions, on other planes, as some of us did, at the time of the accident:
-no procedure relating to the stall of the A330 was integrated in the QRH (quick reference handbook)
-The procedure was in the abnormal complementaires (PAC) in the Air France documentation and in the supplementary items in the airbus FCTM.
It appears (modified) in the QRH in august 2010 (Emergency manoeuvers).
It is then seriously modified, again, in the QRH in october 2010.
The stall, until the accident, was not listed in the emergency manoeuvers, and staying competent by recurrent exercises (especially at high altitude) was never considered. The approach to the stall (as the aircraft, of course, prevents you from entering it), was occasionally demonstrated at low altitude, with a drill totally unsuitable to the high altitudes. It si only now that everybody is really sure that lowering the nose and reducing the thrust if necessary, at high altitude, will get you out of trouble... The Airbus FCTM said that it was not necessary to train the pilots to the stall recovery (Operational Philosophy/Flight controls/ Page 01.020 7th january 2009) and Air France had the same attitude (stall recovery training only for "classical" airplanes. The Bus was considered unstallable. I insist on this for my pilot friends who speak of the competent pilots as opposed, apparently, to the crew. Take a look at the pilots experience. Only taking one copilot, not to bore you, no mention of any high altitude manual flying on the A330, and last useful training on that issue in 1998 on the A320...For the captain, 2001.
Sad but true. I was very experienced when I left the job, and I do not entertain the notion, a single second, that they were incompetent. Just had not seen it, had not been there...

[slats11]

From a system engineer's point of view, I perceive a gross discrepance between automation behaviour *before* leaving the predefined, valid flight envelope, and thereafter. Before, there is protection from all sorts of (possibly) stupid control (http://www.pprune.org/#) inputs by the pilots, but as soon as a single sensor fails, the whole protection system just quits.

Humans are not computers, and are extremely suspectible to fatigue, habits, boredom, surprise and panic. If you wanted to design a system that had the goal of provoking 'human error', these are the human weaknesses you'd exploit. And that is exactly what the airbus did: Lull the pilots into a seemingly fool-proof, fully automated environment, and then, at a slight (!) malfunction of hardware, drop everything raw onto them, intermingled with inconsistent alerts and warnings.


I would agree with this. And I wonder if this logic reflects underlying concerns about blame and legal ramifications if a "protected system" were to crash. So if there is a problem, downgrade the computer support, give greater authority to the pilot and let him/her fly it. If it ends badly, then people will lament the lack of manual flying skills and blame the pilots, the training, the operator, the culture.... rather than the equipment.

So I wonder at the wisdom of abruptly changing horses midstream. And I wonder whether this design logic is in the best interests of the AI, or the passengers.

[syseng68k]

Sriajuda, #242:

While it appears a mystery to almost anyone as to why all three pilots
seemed unable to recognize the stall, I wonder even more about the
apparent lack of the computer's abilities to detect the same.

This is something that I was quite shocked about, expecting a much
higher degree of proactive intelligence from the system design, but
perhaps this is the subtext of a company with a corporate mindset of
"it cannot crash, cannot stall". I keep harping on about this, but
in the absence of normal speed and attitude data, subsystems such
as the ins generate more than enough information for some other
part of the system to monitor current and historical state. Use of
this data could provide improved warning and predictive capability.
This sort of on going "big picture" global monitoring would be mandatory
for applications such as nuclear power, but seems sadly lacking in
aircraft.

While there is no doubt that the crew made serious errors, the plethora of
warnings, not warnings and other inconsistent data presented to the crew,
probably already in a state of panic, can only have made the situation much
worse. It's the duty of the system designers to anticipate the worst
possible conditions, design the system so that it is consistent at
the ragged edge and provide accurate data at all times. Clearly not the
case here and from that point of view, the overall system design failed
the crew.

A trivial example: How difficult would it be to prevent a full back stick
6k/minute vs command at 35k ?...

[Sriajuda]

subsystems such as the ins generate more than enough information for some other part of the system to monitor current and historical state. Use of
this data could provide improved warning and predictive capability.
This sort of on going "big picture" global monitoring would be mandatory
for applications such as nuclear power, but seems sadly lacking in
aircraft.

Exactly my thoughts. And it neither starts nor ends at the computer level: AF447 was not the first AC brought down by a pitot failure. The mistake I see there is what I call 'false redundancy'. While the sensors are there in triple, they are not truly redundant as

a) they are the same type and manufacturer
b) they operate on the same physical principle.

Since numerous ways to measure air speed exist, I cannot understand why not even one truly redundant airspeed measuring device is used in AC. (Boeing is the same here, AFAIK).

[airtren]

Exactly my thoughts. And it neither starts nor ends at the computer level: AF447 was not the first AC brought down by a pitot failure. The mistake I see there is what I call 'false redundancy'. While the sensors are there in triple, they are not truly redundant as

a) they are the same type and manufacturer
b) they operate on the same physical principle.

Since numerous ways to measure air speed exist, I cannot understand why not even one truly redundant airspeed measuring device is used in AC. (Boeing is the same here, AFAIK).

The "redudancy" assumed by this design of speed sensing - which at this point is not different than other manufacturers - seems to target intrinsic/internal sensor failures and less a failure caused by external events, such as weather.

With the current design, the 3 pitot tubes are not only of the same type and same manufacturer, but they are also located pretty much in the same place - under the nose - and thus they're sharing the same fate and will likely behave the same way in front of external events, such as weather. They will fail the same way, and pretty much at the same time, which the case of AF 447 shows so clearly.

From a system architecture and design perspective one can find many weak elements, some of which several recent posts, including yours pointed to.

In the wider perspective, in which design decisions include costs, a very well trained crew, and many others, the presence of multiple factors is supposed to provide an attenuation of the effects of these weak elements. Statistically though, there is always a probability that the elements necessary for the whole to work well are NOT going to be present - as the case with AF 447 shows - with the tragic consequences we know.