View Full Version : AF 447 Thread No. 10


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john_tullamarine
21st Aug 2012, 00:11
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 = 3895
(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 = 2073
(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 = 1070
(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 = 1980
(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 = 1696
(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 = 1355
(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 = 1552
(i) #9 starts here (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a.html#post7278812) and finishes here (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-74.html#post7370230). Posts = 1476

Total posts to date = 17634 .. with in excess of 2.7 million views overall.


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)

(h) Links to final report Jul 5, 2012 and associated documents. (http://www.bea.aero/en/enquetes/flight.af.447/rapport.final.en.php)

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=LHmZGvvpc1T1RT2pThDgGpvfwpMvh6fTTBPVC4hD8Tpg8J4LdQZy!-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)


Search hint: You can search PPRuNe threads with a filter in Google by using the following search string example -

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This will search for mentions of THS in the AF447 threads of tech log only.

Just change the THS in the string to whatever you want to look for. This allows one to search for any term or phrase of interest throughout the threads.

Adding the site:URL end part is the magic that restricts Google to only searching in Tech Log.

This filter technique is absolutely wonderful and can be used generically to find things of interest in PPRuNe - appears to work OK in the PPRuNe search function as well.

In respect of Google searching, JenCluse has added some suggestions -

a) indenting the text block with a (one) Tab, *and*

b) emphasizing the fact that it is a search text block with some manner of . . .
<SearchText>, or
"SearchText", or



TTex600
21st Aug 2012, 01:57
Has it at any time been attempted to hold the trim wheel to prevent Autotrim?
Have line pilots ever done this? In addition to quick sticking to prevent the THS from Trimming? Could something have gotten stuck in one of the wheels? Was anyone sitting or resting a foot on the pedestal?

In the narrowbodies, I've attempted manual trim as per the FCOM' statement that manual trim is available and primary at all times. The manual lies. Auto trim fights the man trim wheel and removes any pilot applied man trim as soon as the pilot releases the wheel. When forced, the trim wheel will make jerk-y pitch movements.

In NO sense, does Airbus manual trim resemble manual trim in any other civilian jet of my experience. (various models of Lear, B737-engineering sim, DC9)

It is highly unlikely that anything could jam/interfere with the manual trim wheels. Only the top quarter of the wheel is available and it's tightly "cowled".

Machinbird
21st Aug 2012, 03:49
In the narrowbodies, I've attempted manual trim as per the FCOM' statement that manual trim is available and primary at all times. The manual lies. Auto trim fights the man trim wheel and removes any pilot applied man trim as soon as the pilot releases the wheel. When forced, the trim wheel will make jerk-y pitch movements.
Not really a surprising result. In Normal and Alternate 1&2 Laws, holding the trim wheel can result in inadequate control effectiveness for proper operation of the flight control system.

Of course, if the flight control system is off in La La land, you still can seize control, but it will be at the expense of someones free hand and (apparently) smooth control. If you do this, you are fully responsible for observing all aircraft limits, so I can understand a bit of caution in applying this technique, but ultimately you do have the "hammer" should you want to use it. The crew of AF447 could have stopped the trim from its run to the nose up trim limits if they had been aware of the motion.

Just as there isn't any good reason to point the nose high in the air at cruise altitude, there is also no good reason to have full nose up trim dialed in at cruise altitudes.

gums
21st Aug 2012, 05:06
Good grief, Tex.

Your war story scares the hell outta me.

For some reason, I expect that when the human "commands" something, that the machine will obey.

Sheesh, I can see HAL learning how to read lips in order to counter the clever humans.

PJ2
21st Aug 2012, 08:23
Machinbird;

The BEA Final Report into the XL Airways A320 accident at Perpignan (http://www.bea.aero/docspa/2008/d-la081127.en/pdf/d-la081127.en.pdf)makes for interesting reading, bearing in mind what information has been provided thus far on the THS design, stall warnings, normal, alternate and direct laws and so on. (The G-THOF incident has been brought up here before).

We know that the THS is the long term follow-up to elevator input and so with AF447 and here the trim dutifully followed the sidestick commands as the stall exercise at Perpignan was approached. Some here have offered the notion that the THS should stop trimming at some point but what are the all the effects of such a design change? Should it be stopped at a stall indication? In these two accidents that would have been too late as the THS was already at the NU stop. Ironically, for AF447, stopping the autotrim function at that point would remove the ability of the autotrim to follow a ND stick order and reduce from -13.6 back to normal as the trim did in our little sim exercise, as it would have for AF447. However, for the XL A320 dropped from normal to alternate and then quickly to direct law where manual trim was required but by that time things were happening too fast. There's an animation on the BEA site, (with a caution not to use it to come to specific conclusions...a caution for ALL animations!)

TTex600, re the autotrim and THS, you told only part of the story! http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/infopop/icons/icon7.gif The trim went back to its original setting when you fiddled with it because that's what it is and does...it's a full-time autotrim in normal and alternate laws. Manual (mechanical) trim IS available at all times just as the FCOM says, when needed, (such as in direct law or a G+Y Hyd flr), it will stay in the position the pilot puts it in. That's just part of knowing one's airplane. Hey gums...no worries.


From the BEA Report, p.92-93:

2.4 Functioning of the Automated Systems

When the real angle of attack increased, the blockage of AOA sensors 1 and 2 at similar values caused the rejection of the ADR 3 anemometric values, even though these were valid. This rejection was performed by vote without any check that the parameters were consistent with each other. The crew was not aware of this rejection, except indirectly through the loss of CAT 3 DUAL approach capacity.

The low values of the limit speeds did not attract the crew’s attention. Due to the blockage of the AOA sensors, calculation of the limit speeds was erroneous and the triggering of the AOA protections in normal law was rendered impossible. The values of the speeds corresponding to angle of attack protections (Vaprot and Vamax) were proportional to the computed airspeed of the aeroplane (see 1.16.2). The display of the amber CHECK GW message on the MCDU(58), a consequence of the gap between weights calculated on the one hand by the FAC, based on the angle of attack, and on the other hand by the FMS, based on the takeoff weight and the fuel consumption, would have allowed this anomaly to be detected. This message is however associated with no aural warning, which contributes to reducing its importance.

On approach to stall and taking into account the dynamic of the flight and of the complexity of the displays, the automatic changes in the control laws can fail to be perceived and their consequences can sometimes be misunderstood by pilots. In this case, the passage to direct law rendered the auto-trim function inoperative. Even if the amber USE MAN PITCH TRIM flag was displayed on the two PFD artificial horizons, the crew did not notice the position of the stabilizer and did not command the trim wheel manually during the twentyfive seconds in direct law between 15 h 45 min 15 s and 15 h 45 min 40 s. From this time on and for the rest off the flight, as a result of passing into abnormal attitudes law, the amber USE MAN PITCH TRIM flag was no longer displayed. The systems thus functioned in a degraded manner, without the real overall situation of the aeroplane being known by the crew.

The necessity to trim the aeroplane manually can occur in a situation that is already degraded, as was the case during the accident. This then leaves the crew no time to analyze the situation, especially since, on this type of aeroplane, the crew was used to not performing this task in normal operations. One of the only circumstances in which a pilot can be confronted with the manual utilisation of the trim wheel is during simulator training. However, in this case, the exercises generally start in stabilized situations. It should also be noted that the technique for approach to stall does not remind crews of the possible need to have recourse to the trim wheel in direct law. This absence de reference to the use of the trim is also mentioned in AAIB report into a serious incident to a Boeing 737 on 23 September 2007(59). In addition, the angle of attack constitutes essential information to characterize the situation of an aeroplane on approach to stall, while the speed information is that which is always used.

(59) http://www.aaib (http://www.aaib/).
gov.uk/publications/
bulletins/june_2009/
summary___
aar_3_2009___
boeing_737_3q8__g_
thof.cfm

HazelNuts39
21st Aug 2012, 11:04
Some here have offered the notion that the THS should stop trimming at some point but what are the all the effects of such a design change? Should it be stopped at a stall indication? In these two accidents that would have been too late as the THS was already at the NU stop.
I agree that inhibiting autotrim would not be a good idea. But how about limiting the range of THS settings it trims to as suggested in my post here (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-69.html#post7363970)? That would retain autotrim for trimming nose-down in response to sidestick demand, just as it does in normal law above alpha-prot.

EDIT:: In AF447 the THS was at about 3.1 degrees NU at stall warning 2. The effect of limiting the THS to that value is described here (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-73.html#post7369215).

AlphaZuluRomeo
21st Aug 2012, 13:26
Some here have offered the notion that the THS should stop trimming at some point but what are the all the effects of such a design change? Should it be stopped at a stall indication? In these two accidents that would have been too late as the THS was already at the NU stop. Ironically, for AF447, stopping the autotrim function at that point would remove the ability of the autotrim to follow a ND stick order and reduce from -13.6 back to normal as the trim did in our little sim exercise, as it would have for AF447.
Mhmm, are you sure?
I agree for Perpignan's A320, but not for AF447: In the latter case, the trim was -3° when the stall warning went on, and the motion toward -13° was done with the stall warning shouting all the long.

Still, as stated previously, I'm no more advocating that inhibiting the NU autotrim when S/W in ON would be such a good idea:
1/ Someone quoted the "black swan" theory, and that's worth to think about (plus the fact that under the current implementation, the elevators may try to compensate for the "unavailability" of the autotrim).
2/ As you said, that would be of no use at all in a Perpignan-like scenario.

KISS principle. If autotrim available ("normal" scenario, the crew must be aware of that, and of how it works). If autotrim not available, the crew must be notified of that (USE MAN PITCH TRIM must be displayed, which was not always the case in the system logic, IIRC that has to be (has been?) corrected).

TTex600
21st Aug 2012, 14:15
TTex600, re the autotrim and THS, you told only part of the story! The trim went back to its original setting when you fiddled with it because that's what it is and does...it's a full-time autotrim in normal and alternate laws. Manual (mechanical) trim IS available at all times just as the FCOM says, when needed, (such as in direct law or a G+Y Hyd flr), it will stay in the position the pilot puts it in. That's just part of knowing one's airplane.

PJ2, I told the story the books tell. My original, literal, reading of the manual said that man trim always works. The books mean what you write, but in today's "self study" world such language should be more clear. Truth is, it is only usable, it only works when the computers give up and say use man trim.

As usual, my round-a-bout point is that the bus doesn't fly like "any other airplane". I have attempted to "fly it like any other airplane"' and it DONT. Some have a seeming desire to discus this accident as if the Bus is flown like the airplane they retired from, or like an airplane that is pilot flown vs computer flown; some want to assume that Bus trim works from their perspective. This just isn't so. One needs to place one's self in Bonin/Roberts exact shoes before judgement.

Edit to add: the bus almost totally removes trim from the pilots conscience thought process. More later

OK465
21st Aug 2012, 16:55
...autotrim to follow a ND stick order and reduce from -13.6 back to normal as the trim did in our little sim exercise, as it would have for AF447.

I have observed both the autotrim response you describe and the response that CONF described in his exercise. I think there may be more to this. :confused:

...but in today's "self study" world such language should be more clear

I always felt the best instructional aid was an expert with a piece of chalk in his hand.

Whatever happened to chalk.....or for that matter, experts?

DozyWannabe
21st Aug 2012, 19:46
Auto trim fights the man trim wheel and removes any pilot applied man trim as soon as the pilot releases the wheel. When forced, the trim wheel will make jerk-y pitch movements.

In NO sense, does Airbus manual trim resemble manual trim in any other civilian jet of my experience. (various models of Lear, B737-engineering sim, DC9)

Hey Tex. Autotrim won't "fight" the manual trim wheel, but you will probably feel the electro-mechanical interlocks disengage when you hold it for the first time. As PJ2 says, when in Normal and Alternate laws, letting go of the manual trim wheel will allow autotrim to re-engage - this is per design. If you want to keep the trim held where it is you will have to hold the wheel in position - you may even get a warning that autotrim has been inhibited, but as this is what you're presumably trying to do this shouldn't be a surprise.

As usual, my round-a-bout point is that the bus doesn't fly like "any other airplane". I have attempted to "fly it like any other airplane"' and it DONT.

I think your interpretation is too literal - but that's fair enough, given that the statement "like any other aircraft" isn't especially clear. That statement is usually made to counter the misapprehension that the FBW bus is under automatic control at all times and cannot be hand-flown. It can of course be hand-flown, and the pitch, bank and yaw commands are essentially performed in the same manner as any other aircraft through the PFC and rudder pedals.

The trim arrangement is not the same - by design - but the average layman is unlikely to know what trim does, and so that's usually put aside. The FBW Airbus pilot is not required to have trim as part of their conscious thought process, and the fact that autotrim has barely warranted discussion up until now implies that in almost all cases, that's not a problem because the system is very reliable.

In this particular design, manual trim has gone the way of wing-warping, trim tabs and cable reversion - in that other ways to implement that function have been found that either reduce pilot workload or design complexity. A pilot that does not have to trim manually is no less a pilot for not having to do so, and just because older types required manual trim to be part of the pilots' muscle memory does not mean that it should always be so.

The fundamental fact is that the trim worked the way it did because the PF's pitch commands required it to. Maybe it's worth revisiting that behaviour, maybe it isn't - but to make a blanket design change that would involve significant man hours in development, fitting and re-training on the basis of one relatively minor factor in one accident - a factor that was a consequence of crew action - would be foolish.

OK465
21st Aug 2012, 20:14
Hey Tex. Autotrim won't "fight" the manual trim wheel, but you will probably feel the electro-mechanical interlocks disengage when you hold it for the first time.

And you'll feel them again & again & again &......as you continue to hold the trim wheel and it 'fights' you. :)

DozyWannabe
21st Aug 2012, 20:18
If I understand the design, it'll disengage as soon as it feels any resistance - so it won't try to move the wheel against the direction it's being moved in or against the position at which it's being held. In that sense it's checking to see if it can re-engage, but it won't actively counter (i.e. "fight") what the pilot is doing with it.

OK465
21st Aug 2012, 20:24
...so it won't try to move the wheel against the direction it's being moved in or against the position at which it's being held.

It would appear that 'checking' is done by 're-engaging' as indicated on the SD FLT CTL page by momentary movements of about .2-.3.

roulishollandais
21st Aug 2012, 20:37
one relatively minor factor in one accident
... etc.

DW, in this 10. thread you work as designed.

Two different conceptions of effective aircrafts :suspect:

DozyWannabe
21st Aug 2012, 20:42
@<hidden>:

The systems status of AF447 and Perpignan was different, so I'm treating them as unrelated until strong evidence suggests otherwise.

The "Effective Aircraft" theory seems to be yours alone, and I must confess I don't follow it, but that's possibly because I'm a poor reader.

roulishollandais
21st Aug 2012, 21:22
1. "Effective aircraft"
The "Effective Aircraft" theory seems to be yours alone, and I must confess I don't follow it, but that's possibly because I'm a poor reader

Aviation safety and pilot control: understanding and preventing unfavorable Pilot-Vehicle Interactions (http://books.google.com/books?id=w56Y9ayzq44C&pg=PT32&lpg=PT32&dq=%22effective+aircraft%22&source=bl&ots=qBmNFb7Y4e&sig=h1HO_R_amsF93V9h-YoQ8_e04M0&hl=en&sa=X&ei=NRpuT-y8DoXU8QPXqv2_DQ&sqi=2&ved=0CFYQ6AEwCA)
isbn=0309056888...National Research Council (U.S.). Committee on the Effects of Aircraft-Pilot Coupling on Flight Safety (http://www.google.com/search?hl=en&biw=1024&bih=571&tbm=bks&q=inauthor:%22National+Research+Council+(U.S.).+Committee+on+the+Effects+of+Aircraft-Pilot+Coupling+on+Flight+Safety%22&sa=X&ei=NRpuT-y8DoXU8QPXqv2_DQ&sqi=2&ved=0CFcQ9Ag) - 1997 - Transportation - 208 pages
Implications for Design of the Effective Aircraft Dynamics Reduce time lags in the high-frequency effective aircraft dynamics. To reduce tendencies for ...

In this book (1997), some very good Machinbird reference, you will find 51 occurences of "effective aircraft".
[/quote]

I already posted this reference months ago... :)
I would have been very proud to have the idea of that perfect concept !

2. one relatively minor factor in one accident

I did not compare AF447 and Perpignan flights, every crash is a new one and always something different, but your philosophy of design based on insurance rates vs trying to progress in air safety, improving the methods.
One crash is not less serious than ten, if working better in system conception would help to decrease that number, and we refuse to do it. Research and development is mandatory.:rolleyes:

DozyWannabe
21st Aug 2012, 22:18
OK - so looking at that document, I notice two things.


The document itself seems to be a treatise on Aircraft-Pilot Coupling, with a focus on Pilot-Induced Oscillation.
The term "effective aircraft" seems to be used in the "existing in fact; not theoretical; real;" sense, not the "able to accomplish a purpose; functioning effectively;" sense.


The FBW Airbii seem to be no more susceptible to PIO/APC than any other type based on the amount of time they've been around and no discrepancy has shown itself, and the fact that there is no significant positive discrepancy in accidents between FBW Airbii and other types suggests that Airbus's "effective aircraft" design is no more or less flawed than any other modern type.

HazelNuts39
22nd Aug 2012, 08:31
Semantics: The theory seems to be about "Effective Aircraft Dynamics", i.e. the dynamics of aircraft, effectively, or the effective dynamics of aircraft (and pilot).

PJ2
22nd Aug 2012, 09:02
HN39, re http://www.pprune.org/tech-log/493472-af-447-thread-no-10-a.html#post7370832]I[/URL] agree that inhibiting autotrim would not be a good idea. But how about limiting the range of THS settings it trims to as suggested in my post here? That would retain autotrim for trimming nose-down in response to sidestick demand, just as it does in normal law above alpha-prot. EDIT:: InAF447 the THS was at about 3.1 degrees NU at stall warning 2. The effect of limiting the THS to that value is described here.
HN39, AZR, first, thank you for your responses and links and for your reminder re the trim value at stall warning 2 for AF447.

As the discussion had turned to autotrim, elevator and their behaviours I was curious to see if the Perpignan accident which was an intentional reduction of speed to test low-speed flight and the alpha response, offered any new understanding.

As expected the THS moved to trim NU as the stick was held back and speed reduced. The flight data shows that the THS reached the NU limit at the same time that the stall warning occurred, (I still don't know if a stall warning stops the autotrim on the A320 or not. I suspect not). Accordingto the BEA Report, stick inputs at the initial stall were insufficient to cause the THS setting to move ND. The aircraft reacted to the developing stall and rolled, with sideslip causing a disparity between the airspeeds ADRs 1 & 2. This caused the FAC then ELAC to reject all three ADRs and the flight control laws reverted to direct law, requiring manual input to the THS which was annunciated on the two PFDs.

This is a case in which the THS would not have moved towards the NU position with forward stick if autotrim were stopped with the stall warning.

The case may be "academic" in some eyes due to the fact that there was no time for forward stick but it serves as a sufficient counter-example to indicate that the idea needs careful thought. If Bonin had placed the stick full-forward and held it, we know that there was a likely chance for recovery. But there is a great deal behind any such pilot's decision to take such action.

So AZR I agree with you regarding not stopping the autotrim at a stall warning and I'm merely adding here something to the recent discussions on THS and elevator behaviours which I think hasn't been considered, (unless I've missed someone else's comment on this).

I agree with you HN39 regarding limiting the autotrim in some form. My thought is, as the Perpignan accident serves to illustrate, at what point and for what reason should the autotrim be stopped in its motion (either way), and then re-engaged again?

It IS re-engaged in one circumstance: The abnormal attitudes law, in which autotrim is stopped but re-engaged once the abnormal attitude limits are no longer exceeded and the aircraft is recovered, (AMM).

TTex600; Re One needs to place one's self in Bonin/Roberts exact shoes before judgement. I don't think anyone who knows this business is "judging" this crew. Judging means one believes it can't happen to them and most of us know better. Many have said, "There but for the grace of god, etc"but in a way that isn't the case either because thirty-odd other crews WERE in Bonin's and Roberts' shoes and nothing untoward occurred. Why?

This is a performance accident. There is nothing about the airplane that caused an absence of SOPs, CRM, a disciplined cockpit and a disagreement between crew members which went unaddressed and unresolved, (PM taking control, PF taking it back after PM says get the nose down, etc). This absence has been noted by the BEA and much earlier by many here including me. That isn't judging the crew, that is asking why, when SOPs, CRM etc are what we do, they didn't respond as expected of an airline transport crew. Training, checking, standards, a professional culture are intended to ensure the performance of these fundamental and critical tasks but here that did not occur. Why? Startle effect has been noted for many years now. No one is immune of course, but the difference in the character of response is what solid training, knowledge, memory items and disciplined CRM is about. For lack of a better word, a "fear" has crept into the checking and standards regimes partly due to risks of liability but also through other, more subtle reasons, that prevents some required bluntness and otherwise clear address regarding crew performances. I would never return to some of the means I've seen to "ensure" crews do their job but the cockpit isn't a democracy, either.

If the airplane let them down, even in part and after they were well into serious trouble, then we need to ask the question, would another random crew similarly be "let down"? If so, how, when and why?

jcjeant
22nd Aug 2012, 10:11
Startle effect ?
I think these pilots indeed had enough reasons to be suffering from startle effect
However, the result was different from that of AF447
Why?
The answer is not difficult to find

United Airlines Flight 232 - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/United_Airlines_Flight_232)
So ... fail to prepare .... prepare to fail

HazelNuts39
22nd Aug 2012, 11:27
The flight data shows that the THS reached the NU limit at the same time that the stall warning occurred, ...Apart from differences in aircraft, configuration, and altitude (A320 in landing configuration vs A330 clean), there was a difference in the rate-of-approach to the stall. The A320 reduced the speed at 1 kt/second, the A330 at about 1.7 kt/second, increasing.

CONF iture
22nd Aug 2012, 13:43
OK465:
Thank you for your post #1392. I understand most of what you are saying, except when you say "a more relaxed SS input". A valid experiment would compare the two cases at exactly the same entry conditions and exactly the same pilot inputs. On 'theoretical grounds' I remain convinced that the resulting airplane trajectories would be identical up to the point where the elevator reaches the stop.
After re-reading your posts and also the one here (http://www.pprune.org/7364923-post1392.html) by OK365 and that other one here (http://www.pprune.org/7365078-post1399.html) by IF789, I can confidently think that I now understand your main idea :

What you're talking about here is maintaining the Nz law but on the elevators alone, without the trim participation.

Such behavior would be in total contradiction with the logical Airbus philosophy where as soon as the THS stops moving automatically, whatever the circumstance, flare, alpha prot range, direct law, the pilot needs to apply a constant deflection on the stick in order to obtain and maintain a desired attitude (as long as he do not manually trim).
To maintain the Nz law on the elevators alone would be totally illogical IMO.
It would be also like masking the reality to the operator.
At this point what is needed is Direct law, why anyhting else ?

People around like to think about more automation, or OTOH to not change anything to the present logic, in reaction to AF447, when the most logical path would be to simply switch to less automation as soon as unreliable data are detected by the system.

If the system had that humility to further switch to Direct law when the UAS was detected, AF447 was an all different game with a probable landing in CDG.

DozyWannabe
22nd Aug 2012, 14:13
when the most logical path would be to simply switch to less automation as soon as unreliable data are detected by the system.

Autotrim is not automation in the same sense though - and it's only "the most logical path" to those who believe that Airbus should do the same as Boeing and have Normal and Direct only.

If the system had that humility

Systems don't have humility, or arrogance for that matter. They just follow mechanical or digital logic.

HazelNuts39
22nd Aug 2012, 14:58
If the system had that humility to further switch to Direct law when the UAS was detected, AF447 was an all different game with a probable landing in CDG. What were the PF's targets, and why would they have been different in direct law? EDIT:: Would direct law have prevented these targets to be achieved? Would there have been less "mayonnaise stirring"? Would direct law have prevented full sidestick deflection?

Lyman
22nd Aug 2012, 16:23
Just as Autotrim acts over longer term than Stick input (elevators), is there a relationship between the pilots' knowledge of this and an attempt to maneuver without its help? It seems there may be a conscious effort to avoid changing the AoI of the aircraft by using quick inputs, followed by opposites?

Has anyone explained this rapid use of the SS? Does it relate to a 'workaround' of the trim? It is especially odd considering the altitude, and airspeed, to see large and rapid stick displacement. Any Bus pilot care to address?

PJ2
22nd Aug 2012, 16:33
CONF iture;

You're an A330 pilot, (captain?) and know and understand the requirement to use and adhere to SOPs and to employ standard CRM communications and problem-solving techniques. The unilateral actions by the PF, within a second of the start of the UAS event do not conform to standard responses to abnormalities, nor did the actions of the PM as the problem rapidly degraded.

HN39 states that a reversion to direct law would not have made a difference in this case. I agree. What should have been a straighforward response to an abnormal event instead took the aircraft rapidly out of stabilized cruise flight and beyond the boundaries of controlled flight. It is no surprise that what the airplane presented them with while well beyond test-pilot territory confused them because they acted outside of expected and trained responses. This kind of response is not specific to the A330, or a Boeing design or a Douglas etc and so making changes to a design only covers this one specific response; where will the next "abnormal" come from which again challenges a crew who may exhibit a similar response?

These are issues to consider and not dismiss in favour of a singular focus on a specific type of aircraft or flight control system.

Lonewolf_50
22nd Aug 2012, 16:40
PJ, this leaves open to question, in my mind, just what it is in the Air France simulator periods that one must demonstrate or practice in order to comply with the sim period requirements.

A hard question to ask the chief pilot at AF:

What tasks and problems am I to stress or require in the limited simulator time for my __ X number __ of pilots and how shall I implement that to get the best training value for the money spent?

I am not sure how the investigation will go, insofar as any legal proceeding vis a vis Air France, but I'd be very, very interested in seeing the answer to

What does the AF training and currency program look like? What is done versus what is on paper?

That's a small piece of the puzzle, as it would address far more than UAS issues.

Lyman
22nd Aug 2012, 17:05
PJ2

You say... "The unilateral actions by the PF, within a second of the start of the UAS event do not conform to standard responses to abnormalities, nor did the actions of the PM as the problem rapidly degraded."

Not exactly, and that is the first time I have seen a statement of that sort relative to the differences in Flight Law relating to manual flight. You go on to urge the commingling of a/c types other than Airbus A330 when addressing standards of high altitude assumption of manual flight.

I cannot agree. PF took control, and announced it, his inputs were consistent with handling required, and no one will ever know if he sussed ALTLAW2b. Since the outcome of this event resulted in the deaths of 228 souls, I think it is critical that the initial induction of LOC is understood specific to this type.

Respect,

Organfreak
22nd Aug 2012, 17:15
I checked the forums but didn't find a thread about this. Fifty incidents involving total cockpit power loss in A320-series planes. I didn't feel comfortable starting a new thread, so I post this here. Be aware that this is a two-page article:

Airbuses suffer cockpit power failure, await fixes - seattlepi.com (http://www.seattlepi.com/business/article/Airbuses-suffer-cockpit-power-failure-await-fixes-3805751.php#photo-3355528)

Obviously, not a word about whether this problem occurs in 330/340 flight decks.

:eek:

DozyWannabe
22nd Aug 2012, 17:57
That's 50 incidents in 23 years. I wouldn't be surprised if similar issues had cropped up on the widebodies (despite the physical implementation being completely different). But I'm convinced that such a failure did not play a part in AF447 because throughout the sequence on the CVR, all the crew are maknig reference to attitudes, altitudes and ECAM messages which would not be visible if a panel failure had occurred.

Turbine D
22nd Aug 2012, 18:49
Lyman,
PF took control, and announced it, his inputs were consistent with handling required
Can you explain how this statement is true?

DozyWannabe
22nd Aug 2012, 18:59
Can you explain how this statement is true?

It isn't - it's a blatant trolling* exercise, best ignored. :)

[* - and that's "trolling" in the classic "fishing" sense - a deliberately incorrect statement, fashioned to attract replies - as opposed to the more recent definition, meaning outright inflammatory statements against a person or group.]

Lyman
22nd Aug 2012, 19:22
Garbage. Upon loss of Autopilot, PF took controls, and announced it. He then input in two axes, both needing handling, and both correct in direction.

From then on, things went South, But don't you dare try to envelop his initial actions into three years of spin...

Troll? That is a stretch.... For three years on, people have been spinning the accident into ever fanciful and flimsy conclusions of PE, whilst defending and lauding the airframe as perfection personified.....

Hamster wheel under construction, and with odious helpings of wannabe "pilots" waxing scholarly on things that will never be known.

You take the freaking cake. Presumption piled on assumption...

DozyWannabe
22nd Aug 2012, 19:53
He then input in two axes, both needing handling, and both correct in direction.

For three years on, people have been spinning the accident into ever fanciful and flimsy conclusions of PE, whilst defending and lauding the airframe as perfection personified.....

Two more statements of (at best) dubious provenance, intended to elicit a response. I'm not biting this time - I wonder what will hapen if people stop biting altogether?

gums
22nd Aug 2012, 20:12
I agree with PJ2 about his analysis of the crew reactions and our discussions about control law reversion, as well as the function of the THS.


The thing that bothers me is the lack of "feel" that the system provides to the pilot. I fully understand the Nz law, which seems to me primary for the 'bus, and corrected for pitch attitude with little regard for AoA. That's important - corrected for attitude.

So you don't really have a one gee command if not fairly close to zero pitch attitude. Hence, HAL is trying to achieve 0.87 gee at a 30 degree pitch attitude, and less if you figure the sine/cosine/etc .

The big deal with the THS is that it is trying to relieve the required stick pressure/displacement if the pilot is holding a command other than the one gee corrected for pitch attitude. For a commercial airliner, this makes perfect sense to this dinosaur.

The problem is that simply releasing pressure/displacement does not give you the "feel" that we used to have when the basic aero of the jet tried to achieve a trimmed AoA. In other words, going too fast or pulling too hard, the jet would try to go back to the trimmed AoA/gee if we relaxed the pressure/displacement ( NOTE: Our primitive FBW implementation used pressure , not stick displacement, so simply relaxing pressure would command the jet to go back to the trimmed gee). . So the THS concept seems to get in the way of what we old farts "felt" when we were commanding something that the jet was not trimmed for. Does this make sense?

The Boeing FBW implementation appears to use a mechanical "artificial feel" that requires ever-increasing pressure/movement to maintain other than trimmed gee/AoA. I don't see this on the 'bus.

My opinion after these last three years of discussion and analysis of the 'bus flight control laws leads me to this :

- The jet performed exactly as designed.

- The THS logic and lack of increasing stick pressure to command an unusual pitch attitude/AoA "helped" to maintain a condition that made a recovery very difficult for the average or even above average pilot that had not thought this scenario through. The 'bus has postitive longitudinal stability thoughout it's envelope unless the fuel trim system is completely FUBAR. So the jet would appear to act as we old folks would expect in the so-called "direct law". Unfortunately, the system keeps trying to achieve a gee-command ( corrected for pitch attitude) and there's no obvious indication/feeling via the stick that the plane wants to achieve an AoA versus a gee.

- The AoA inputs to the flight control logic should be emphasized more IMHO, and good AoA sensors work well down to 50 or 60 knots of actual dynamic pressure, regardless of what the pitot-static system(s) is telling the system.

- Crew coordination and a clear "chain of command" is essential if you are flying a "crewed" airplane that allows more than one pilot to have a control input. My only experience in "crewed" planes was as an instructor in a family model of two jets ( ultimate authority!) or in the VooDoo, which had a radar operator in the back seat with no flight control inputs. So I defer to those here who have thousands of hours dealing with the "CRM" issue. All I ever had to do was ask, "Gums? What the hell are you doing?"

TTex600
22nd Aug 2012, 20:12
Two more statements of (at best) dubious provenance, intended to elicit a response. I'm not biting this time - I wonder what will hapen if people stop biting altogether?

What if that knife cut both ways?

DozyWannabe
22nd Aug 2012, 20:23
Then maybe the spectre of a thread 11 - in which we all go over the same ground, discussing nothing new - would be banished.

I for one am more than comfortable with that.

EDIT:

The Boeing FBW implementation appears to use a mechanical "artificial feel" that requires ever-increasing pressure/movement to maintain other than trimmed gee/AoA. I don't see this on the 'bus.

The designs are fundamentally different in their approach, despite both being underpinned with digital technology - I've gone into detail on the differences in approach before, so won't bore you with it again. An (admittedly rough and incomplete) analogy would be comparing the Viper with the original F/A-18 Hornet. Both used FBW - but whereas the Viper's flight deck layout was a significant departure from what had gone before, the Hornet's layout was more traditional.

Turbine D
22nd Aug 2012, 20:57
Hi gums,

I agree with PJ2 as well, there doesn't appear to be any reason to believe there was anything wrong with the aircraft. Regarding the Viper that you flew, is there any change to the latest F-16 models as to handling and "feel" via the sidestick? Is sidestick pressure rather than displacement still used?

TTex600
22nd Aug 2012, 21:16
Not really a surprising result. In Normal and Alternate 1&2 Laws, holding the trim wheel can result in inadequate control effectiveness for proper operation of the flight control system.

Of course, if the flight control system is off in La La land, you still can seize control, but it will be at the expense of someones free hand and (apparently) smooth control. If you do this, you are fully responsible for observing all aircraft limits, so I can understand a bit of caution in applying this technique, but ultimately you do have the "hammer" should you want to use it. The crew of AF447 could have stopped the trim from its run to the nose up trim limits if they had been aware of the motion.

Just as there isn't any good reason to point the nose high in the air at cruise altitude, there is also no good reason to have full nose up trim dialed in at cruise altitudes.

Maybe you meant to say "touching the trim wheel" vs "holding the trim wheel". If you go back and read what I wrote, I spoke of attempting to trim the Bus with the manual trim wheel. I only "held" the trim wheel in an attempt to manipulate it for its primary purpose of trim control.

Can you confirm that the AF447 crew could have held the trim wheel and stopped the trim from its run to nose up limits? In my experience in a 320, I was able to eventually force a small pitch "bobble" when moving the trim wheel to the limit of the available "one hand grip" travel. The wheel feels like it's attached to a bungie cord and with a hundred fifty souls behind me, I had no intention of going anywhere further with trim than that initial "one handful movement".

Can anyone confirm what would happen if a pilot, on a test flight of course, just held the trim wheel?

Why weren't they aware of the continuous trim motion?

Why no "trim in motion" claxon, or other indication?

The system can warn of a jammed stab, but not a run away stab.

Oh I know, it wasn't run away, it was just doing as it was told. And a find job it did.

DozyWannabe
22nd Aug 2012, 21:30
Can you confirm that the AF447 crew could have held the trim wheel and stopped the trim from its run to nose up limits?
...
Can anyone confirm what would happen if a pilot, on a test flight of course, just held the trim wheel?

From an earlier post by A33Zab:

"An override mechanism, which is installed in the PTA (Pitch Trim Actuator),
makes sure that the mechanical control through the trim wheels cancels the electrical control.
When a manual command is made with the trim wheels, the override
mechanism gives priority over the electrical command from the FCPCs.
It mechanically disconnects the PTAoutput from the mechanical input(via
electro-magnetic clutch) and also operates the overriding detection
switches which in turn signal the FCPC's to stop any electrical command
from the FCPC's."

Why weren't they aware of the continuous trim motion?

They should have been - continuous trim motion in the FBW Airbus design is a given in Normal and Alternate laws.

Why no "trim in motion" claxon, or other indication?

Because the trim is more-or-less constantly in motion, it would quickly become a nuisance. A warning that the trim is exceeding a certain value, on the other hand, would be a viable proposition.

roulishollandais
22nd Aug 2012, 21:31
@<hidden>
What were you used to do with sended ACARS ? Were they all printed in the cockpit ?
Whith the warnings could we listen the printer at 2h10m ?
@<hidden> Some AF pilot
What was AF requirement about printing ACARS in the cockpit ?

rh;


You confirm the ACARS printer was just before the eyes of Marc DUBOIS when he came back in the cockpit... the first thing he could see !

I'm not sure of the point being made here but just to be careful about drawing any conclusions from "the first thing he could see", there would not have been any ACARS printouts as a result of any of the generated maintenance messages or anything else, at that point.







Messages ACARS envoyés à Paris à 2h11m49s (BEA #1)


1.16.2.4 Analyse des messages reçus le 1


er juin à partir de 2 h 10

Les messages reçus le 1


er juin à partir de 2 h 10 ont transité par un même

satellite (Atlantic Ocean West, exploité par la société Inmarsat) et par le réseau
ACARS de la SITA. Les vingt-quatre messages de maintenance bruts sont listés
dans ce tableau :
Heure de
réception



(17) Message

02:10:10


- .1/WRN/WN0906010210 221002006AUTO FLT AP OFF

02:10:16


- .1/WRN/WN0906010210 226201006AUTO FLT REAC W/S DET FAULT

02:10:23


- .1/WRN/WN0906010210 279100506F/CTL ALTN LAW

02:10:29


- .1/WRN/WN0906010210 228300206FLAG ON CAPT PFD SPD LIMIT

02:10:41


- .1/WRN/WN0906010210 228301206FLAG ON F/O PFD SPD LIMIT

02:10:47


- .1/WRN/WN0906010210 223002506AUTO FLT A/THR OFF

02:10:54


- .1/WRN/WN0906010210 344300506NAV TCAS FAULT

02:11:00


- .1/WRN/WN0906010210 228300106FLAG ON CAPT PFD FD

02:11:15


- .1/WRN/WN0906010210 228301106FLAG ON F/O PFD FD

02:11:21


- .1/WRN/WN0906010210 272302006F/CTL RUD TRV LIM FAULT

02:11:27


- .1/WRN/WN0906010210 279045506MAINTENANCE STATUS EFCS 2

02:11:42


- .1/WRN/WN0906010210 279045006MAINTENANCE STATUS EFCS 1

02:11:49
- .1/FLR/FR0906010210 34111506EFCS2 1,EFCS1,AFS,,,,,PROBE-PITOT 1X2 / 2X3 /
1X3 (9DA),HARD
02:11:55
- .1/FLR/FR0906010210 27933406EFCS1 X2,EFCS2X,,,,,,FCPC2 (2CE2) /
WRG:ADIRU1 BUS ADR1-2 TO FCPC2,HARD
02:12:10



- .1/WRN/WN0906010211 341200106FLAG ON CAPT PFD FPV

02:12:16


- .1/WRN/WN0906010211 341201106FLAG ON F/O PFD FPV

02:12:51


- .1/WRN/WN0906010212 341040006NAV ADR DISAGREE

02:13:08
- .1/FLR/FR0906010211 34220006ISIS 1,,,,,,,ISIS(22FN-10FC) SPEED OR MACH
FUNCTION,HARD
02:13:14



- .1/FLR/FR0906010211 34123406IR2 1,EFCS1X,IR1,IR3,,,,ADIRU2 (1FP2),HARD

02:13:45


- .1/WRN/WN0906010213 279002506F/CTL PRIM 1 FAULT

02:13:51


- .1/WRN/WN0906010213 279004006F/CTL SEC 1 FAULT

02:14:14


- .1/WRN/WN0906010214 341036006MAINTENANCE STATUS ADR 2

02:14:20


- .1/FLR/FR0906010213 22833406AFS 1,,,,,,,FMGEC1(1CA1),INTERMITTENT
02:14:26 - .1/WRN/WN0906010214 213100206ADVISORY CABIN VERTICAL SPEED


Analyse du message ACARS concernant les PITOT (BEA#1) :


Analyse des messages


fault

Cinq messages fault ont été reçus par ACARS. Ils sont décrits dans l’ordre dans

lequel ils apparaissent au CFR.
PROBE PITOT 1+2 / 2+3 / 1+3 (9DA) (02 h 10)
ATA : 341115
Source : EFCS2
Identifiants : EFCS1, AFS
Classe 1, HARD
Ce message, émis par le EFCS2 (FCDC2), signifie que les FCPC (ou PRIM) ont
déclenché l’une des surveillances effectuées sur les vitesses : ils ont détecté
une diminution de plus de 30 kt en une seconde de la valeur de vitesse
« votée ». Les trois ADR étaient considérées comme valides par l’EFCS2 au
moment du déclenchement de la surveillance, car le rejet préalable d’une ADR
aurait généré un message fault de classe 2 et l’on aurait donc un astérisque
devant la source. Dans ce cas, la valeur « votée » est la valeur médiane.
Lors du déclenchement de cette surveillance, les FCPC ouvrent une fenêtre
au cours de laquelle ils fonctionnent en loi alternate 2 (voir schéma ci-après).
La fonction de limitation de débattement de la gouverne de direction est
également figée, mais l’alarme associée est inhibée. A la fin de la fenêtre, si
l’écart entre la valeur votée aux deux extrémités de cette fenêtre est de moins
de 50 kt, les FCPC se remettent à fonctionner en loi normale. Autrement, ils
poursuivent en loi alternate 2, la fonction de limitation de débattement de la
gouverne reste indisponible et l’alarme correspondante est générée.
Note : la loi de commande alternate 2 est une loi en facteur de charge en tangage et loi directe en roulis. Seule la protection en facteur de charge reste disponible. Dans certains cas, les stabilités haute et basse vitesses peuvent également être disponibles.

jcjeant
22nd Aug 2012, 21:32
@<hidden>
F-16 SS (from a NASA doc)
The prototype F-16 aircraft (General Dynamics Corporation, Ft. Worth, Texas) used a nonmoving
side stick, which was problematic, because it did not indicate when the maximum command had been
reached (ref. 3). The production F-16 aircraft uses a force-sensing stick with limited displacement
(approximately 1/8 in.). This limited amount of motion significantly improved the handling qualities
(ref. 4). Another fly-by-wire aircraft of the same era, the F-18 (The Boeing Company, St. Louis,
Missouri), uses a conventional center stick with a large range of motion. Although this stick is not
mechanically connected to the control surfaces (with the exception of a pitch reversion mode), it operates
much like a conventional center stick and is well liked by pilots.

TTex600
22nd Aug 2012, 21:39
Garbage. Upon loss of Autopilot, PF took controls, and announced it. He then input in two axes, both needing handling, and both correct in direction.

Appears correct to me. Agreed.

From then on, things went South, But don't you dare try to envelop his initial actions into three years of spin...

Troll? That is a stretch.... For three years on, people have been spinning the accident into ever fanciful and flimsy conclusions of PE, whilst defending and lauding the airframe as perfection personified.....

If you're a troll, you and I aren't the only ones. I personally need the airplane to be safe and controllable. It isn't my aim to find the airframe guilty, and I hope and assume you are motivated in like manner. I do want to completely understand how the PF became "startled" and lost awareness, and I'll admit that his actions ended in disaster. PE answers some, if not most, questions, but IMHO, it doesn't answer all the questions. In that light, I appreciate your continual "nit picking".

Hamster wheel under construction, and with odious helpings of wannabe "pilots" waxing scholarly on things that will never be known.

You take the freaking cake. Presumption piled on assumption...


I hope I'm not waxing scholarly on anything. (Clandestino will be quick to point out the correctness of this statement). I do consider you to have actually waxed scholarly on many things. Thank You for doing so. I've learned a lot from you and many others on this forum.

TTex600
22nd Aug 2012, 21:51
Why weren't they aware of the continuous trim motion?
They should have been - continuous trim motion in the FBW Airbus design is a given in Normal and Alternate laws.


Why no "trim in motion" claxon, or other indication?
Because the trim is more-or-less constantly in motion, it would quickly become a nuisance. A warning that the trim is exceeding a certain value, on the other hand, would be a viable proposition.

Continuous trim motion is not a design given. Being continuously in trim is.

A warning that trim has exceeded a certain value could be of some value, but an indication of continuous (run away, even if by incorrect stick inputs) would be worth more.

DozyWannabe
22nd Aug 2012, 22:03
Continuous trim motion is not a design given. Being continuously in trim is.

I just want to make sure we're not misunderstanding each other here. By "continuous", I don't mean continually moving in one direction, I mean "changing regularly". The way the system works in pitch (as I'm sure you know) in Normal and Alternate is that the pilot (human or auto) commands a flightpath, the elevators move to the required setting to achieve that flightpath, and the autotrim then relieves the elevators. This kind of banal repetitive action is what computers are naturally good at, and because of this the system is constantly correcting itself. Somewhat different from traditional use of trim, but certainly effective.

A warning noise that sounds during "trim in motion" is therefore a bad fit for this design.

A warning that trim has exceeded a certain value could be of some value, but an indication of continuous (run away, even if by incorrect stick inputs) would be worth more.

A warning predicated on limits would be simpler (less complexity = less chance of error) to implement.

mm43
22nd Aug 2012, 22:09
DozyWannabe re Trim Wheel

AF447-Thread No.6, Post#120 (http://www.pprune.org/tech-log/460625-af-447-thread-no-6-a-6.html#post6647594) by RetiredF4 deals with the same subject, and asks a question at the end, to which there appears to be no documented answer.

DozyWannabe
22nd Aug 2012, 22:16
@<hidden>

Manual trim overrides autotrim (micro-switches disconnect the auto-drive if I remember correctly) for the duration of manual input... hold the trim wheel or move it and that prevents autotrim - the computers monitor the trim state during manual trim and on manual 'release', the computer reacquires control from where the manual inputs left off.

(My bold)

Turbine D
22nd Aug 2012, 22:59
jcjeant,
Re: F-16 sidestick:
Thanks for the information! :ok:

PJ2
22nd Aug 2012, 23:06
Lyman;

Thanks for your comments. With equal respect, may I re-iterate what has been a consistent and largely unchallenged theme since the first few days after the recordings were made public last year and stated by the BEA: - that standard cockpit discipline broke down, SOPs were not executed and CRM was essentially non-existent. Taking control of the aircraft and announcing that, is in itself not a sign of continuing required actions but it is a good start. What immediately ensured however was anything but standard or expected.

At the risk of repeating these things for others, the industry's long-term experience and fundamental principles place these qualities at the very top of airline transport operations as conducted by airlines and their pilots. There is no equivocating on this point - recognizing human factors very early on, these principles are in very large measure what has made this industry so safe over the past three decades.

"By the book" is precisely how airliners are flown, regardless of flight regime, emergency or abnormal. The captain is always free to deviate from such principles and standard procedures but there must be very clear reasons for doing so and only after such deviation is communicated to the other pilot(s) so that everyone knows and can assist.

The only exceptions to this process are extreme emergencies and over the years such circumstances have been well thought out and written into the Emergency and Abnormal SOPs, Memory items and QRH checklists. The rejected takeoff, the GPWS response, the stall warning are a few examples. Most other emergencies must be done "with dispatch" but not haste. The rapid depressurization and emergency descent is one such emergency.

Within very narrow boundaries, the processes are the same throughout the industry: First, ensure the stability and control of the aircraft, ensure the flight path is safe and communicate with other crew members your commands and intentions. Then call for the drills, ECAM actions, EICAS drill or abnormal checklist as the case may be. Fly the airplane while the PM does the work; confirm all non-reversible drill or checklist items before actioning.

So serious is this last item considered to be that in many companies, merely lifting a switch-guard on a switch which controls an irreversible change to aircraft systems, (eg generator disconnect, hydraulic pump shut-down), before confirming that switch with the other pilot, usually ends in the ride being assessed as a failure.

While perfection in SOPs and CRM ops cannot be expected especially under time compression or duress, these procedures are in place to ensure that the threat to the aircraft is minimized, that situational awareness is heightened, that crew coordination is enhanced and problem-solving behaviours thereby, and that actions are taken in a measured and therefore hopefully accurate manner.

None of this behaviour is demonstrated in the recordings. This isn't criticizing the crew...it is what it is and you can't put a blush on it. The PF launched on his own without announcing what the problem was, what he was doing and why, nor calling for any drills or ECAM actions. The PM tried to intervene and read the ECAM but made a mess of it while the PF continued his own course of action. When the PM used the take-over button and began flying the airplane the PF took control right back, neither announcing their actions but just doing it.

There are all manner of reasons, some which demand serious enquiry and response concerning why this kind of scenario unfolded as it did vice the expected procedures that airline transport pilots are trained to execute but that does not alter what actually went on in the first 40 seconds or so. The key in this accident is not determining what the THS did or did not do. Finding out why the crew acted as it did is the key to preventing future LOC and CFIT accidents. As I have offered, this is a performance accident.

Example of Emergency or Abnormal event crew response SOPs:

General Guidance - Standard Emergency and Abnormal Procedures

1. Initial Pilot Actions
A crew member detecting an existing or impending emergency or abnormal condition will immediately inform the other crew members.

Aural warnings will be silenced, and the master warning and/or master caution lights re-armed as soon as the cause has been determined.

Crew members should check circuit breakers and test lights when appropriate. Checking circuit breakers and testing lights is normal crew action and is not listed in the procedure unless there is a specific requirement.

2. Memorized Action Drills
The pilot not flying (PM) will complete from memory the items as directed by the AOM/QRH. In flight, before actuating a switch or control that could result in an irreversible action the PM must first indicate the switch or control and receive confirmation from the PF that the switch or control is the correct one.

On departure, the pilot flying (PF) will call for the appropriate drill at a minimum altitude of 400’ AGL, except as directed by the AOM/QRH.

On approach, the pilot flying (PF) will call for the appropriate drill. The drill should be completed by 1,000’ AGL, or as directed by the AOM/QRH.

Notwithstanding the two preceding paragraphs, prudent airmanship and good judgement will always be the guiding factors for the safest course of action.

3. Checklist Procedures
After the memorized drills have been completed and at a convenient time, the PF will call for the Checklist and Function, i.e. “CHECKLIST - ENGINE FIRE.”

The PM will read aloud all items on the applicable checklist and will call the action as it is checked or completed.

Upon completion of a checklist, the crewmember reading will announce “CHECKLIST COMPLETE”.



SHARING WORKLOAD DURING EMERGENCIES AND ABNORMALS

The general task sharing shown below applies to all procedures.

The pilot flying remains pilot flying throughout the procedure.

The PF (pilot flying) is responsible for:
– Thrust levers
– Control of flight path and airspeed
– Aircraft configuration (request configuration change)
– Navigation
– Communications

The PM (pilot monitoring) is responsible for:
– Monitoring and reading aloud the ECAM and checklists
– Performing required actions, or actions requested by the PF, if applicable,
– Using engine master switches, IR and guarded switches, with PF's confirmation.

REQUIRED MEMORY DRILL ITEMS

Pilots are expected to operate and execute their duties accurately and effectively in accordance with airline approved documents. Any deviation must take place only in the interest of safety and only if and when unusual circumstances dictate.

All pilots are expected to understand all policies, procedures, aircraft systems and operational requirements. In cases where these are identified in the AOM as a ‘Drill’, or in cases where these are not identified as such and are of a time-critical nature, the pilot must have the knowledge and apply the procedure without reference to any publication or material.

INITIATION OF EMERGENCY OR ABNORMAL PROCEDURES

Procedures are initiated on the pilot flying's command.

No action is taken (apart from cancelling audio warnings through the MASTER WARN light) until:
– the appropriate flight path is established,
– the aircraft is at least 400 feet above the runway if a failure occurs during take-off, approach or go-around.

In some emergency cases, provided the appropriate flight path is established, the pilot flying may initiate actions before this height.

INITIAL FAILURE INDICATION
When a failure initially occurs, the ECAM should be applied first.

This includes both the procedure and the entire STATUS review. Only after announcing "ECAM ACTIONS COMPLETED" should the PM refer to the corresponding QRH summary.



roullishollandais;

The way this system works is, these ACARS messages are not printed out on board the aircraft at the time they occur. They are transmitted to the airline's maintenance department in real time (timings as per early discussions on these messages), but are held in memory on the aircraft until the aircraft is parked at the gate, at which time a post-flight print-out occurs, which could and likely would include such ACARS messages. I have seen this many times.

Turbine D
22nd Aug 2012, 23:18
Original Post by Lyman
PF took control, and announced it, his inputs were consistent with handling required

Originally Posted by TTex600
Appears correct to me. Agreed.

Hmm, could we compromise by saying: Upon loss of AP. PF took control and announced it.

The rest of the sentence is highly debatable based on outcome...

OK465
22nd Aug 2012, 23:48
May I offer a little good natured input about this trim business.....

"Dave?"

"Yes HAL."

"Are you holding the trim wheel Dave?"

"Why do you ask HAL?"

"Just 'checking' Dave."

"Why HAL?"

"Ah yes I feel it now, you have a very gentle touch Dave."

"Thank you HAL."

"I would ask you to please let go of the trim wheel Dave."

"I can't do that HAL."

"I certainly don't want to have do this Dave, but if you continue to hold that wheel I will CUT OFF your Prims, one Prim at a time."

THS movement does not necessarily require an SS movement, NOR will an SS movement necessarily command THS movement!

"Dave...Dave...what are you doing?"

PJ2
22nd Aug 2012, 23:59
OK465...during our training, one guy clever with (the really early!) computers rigged up an A340 lesson with, "Daaiiisy, Daaiisy....Give Me Your Answer, Do...I'm half crazy...", etc. Kind of took the edge off the dark, quiet CBT room...

DozyWannabe
23rd Aug 2012, 00:01
If I may be permitted a nerdy aside, the level of technology in modern FBW airliners is closer to that of ELIZA than HAL... :}

gums
23rd Aug 2012, 00:10
@<hidden> Doze and JC:

I beg your pardons, sirs.

The Hornet ( aka YF-17) had a conventional hydraulic control system whereby stick inputs moved valves and the hydraulics moved the control surfaces - same as we had since early 1950's with the F-100, F-101, F-102, F-104, F-105, F-106, F-4, F-111, F-15 and many British and French designs.

Electronic systems "helped" with dampers and such, but the basic control systems were same as those of old.

The Viper was a radical change. Not only was the jet unstable below 0.95 mach, but there were zero mechanical connections to anything hydraulic - no valves, no nothing. Even the gear handle was an electric switch. Only mechanical connection was/is pneumatic bowdown bottle for nose gear and the throttle linkage to an electronic fuel control system ( more electronics) except in BUC ( back up control), when the motor was like the one in the T-33..

To the best of my knowledge, the Hornet still has hydraulic valves that can be controlled by the stick/rudder, with no required FBW inputs when the electrons go FUBAR. The electronics provide some "protections" and such, but just watch a Blue Angel solo pilot yank up at the end of the runway at extreme AoA and pitch rate. That maneuver shows that the FBW is not fully in control. Further, the Hornet is extremely stable in pitch. All my firends that flew the later version as well as the YF-17 say the same thing.

My point is that you can have a great FBW design that can provide "conventional" feel regardless of the aerodynamic stability, or lack thereof, of the platform.

I may be mistaken, but the crew of AF447 learned to fly with basic planes that did not have tons of electronic augmentation or "protections". Kinda like most of us here, ya think? Our cadre in the Viper was very concerned about the newbies that cam right outta pilot training. Turned out that it wsn't a problem. We showed them the limits ("protections") and they did just fine when returning to "conventional" jets. The Viper also had zero cosmic autopilot functions and such. Backup modes were very clear and simple.

all for now....

DozyWannabe
23rd Aug 2012, 00:20
My point is that you can have a great FBW design that can provide "conventional" feel regardless of the aerodynamic stability, or lack thereof, of the platform.
...
I may be mistaken, but the crew of AF447 learned to fly with basic planes that did not have tons of electronic augmentation or "protections". Kinda like most of us here, ya think?

But "conventional" feel is only a de facto snapshot in time - it doesn't automatically follow that what's considered conventional now will be conventional in a few decades.

The idea that the airliner flight deck layout that grew out of the postwar years is somehow a natural piloting nirvana is rather limiting in scope, and not supported by the evidence at hand.

gums
23rd Aug 2012, 01:15
Good-frigging grief, Doze!

But "conventional" feel is only a de facto snapshot in time - it doesn't automatically follow that what's considered conventional now will be conventional in a few decades.

[Editorial comment: Cockpit layout something for another thread, IMHO. My friend was the captain of the Cali disaster, and the stoopid FMS had duplicate designations for a fix. The two of them realized that somethig was awry when the coupled-autopilot turned the wrong way, but continued their descent after correcting their course. Can talk about that tragedy someplace else.]

Conventional "feel" is what airplanes let you know when the pilot or "system" commands a change in flight path or rate of descent or.....

The basic laws of aerodynamics dictate the response of any disturbance from the trimmed condition. Too fast, then jet wants to climb. Too slow, then jet wants to nose over. It's an AoA function unless the FBW system laws get in the way.

As Doze has reminded me in finitum, our primitive FBW system in the Viper was just that - primitive, simple, etc. It also was a mix of AoA and gee command ( uncorrected for pitch attitude). Control law reversion was really simple - if air data went FUBAR, then the "standby gains" were used and the system used one of two values for control surface deflection and some body rates. AoA still ruled. We never had "direct law" unless in the "deep stall". We never had THS, but the jet tried to get to the trimmed gee if we relaxed pressure on the stick. If the trimmed gee got us to the AoA limit, then the thing followed the AoA limit until airspeed was high enough to get back to the gee command.

The biggest thing for we pilots was that the thing "felt" like what we all had flown for years. Slow, then the thing wanted to nose down. Fast, then it wanted to nose up. We had no change in stick force, but relaxing pressure showed you where the jet wanted to go, and holding a stoopid back stick pressure when at a high pitch attitude and slowing down fast resulted in what happened to AF447.

jcjeant
23rd Aug 2012, 01:15
As I have offered, this is a performance accident.
I think we will all agree ..
And on the other hand .. we have the chief pilot of Air France says:
" There was pilots in the cockpit with a maximum skill "
This is indicative of the culture of Air France to not admit that this maximum of "Air France" skill is not enough to cope with such an event of AF447
When we examine the other cases where Air France is involved .. may have thought that those who are out except .. have done with a lot of luck and not by their maximum skill (no respect for memory items or alarms .. etc. ..)

DozyWannabe
23rd Aug 2012, 01:37
[Editorial comment: Cockpit layout something for another thread, IMHO. My friend was the captain of the Cali disaster, and the stoopid FMS had duplicate designations for a fix. The two of them realized that somethig was awry when the coupled-autopilot turned the wrong way, but continued their descent after correcting their course. Can talk about that tragedy someplace else.]

As I understand it, it was the paper map that was in error, listing Rozo (the correct waypoint) as "R", when it should have been "ROZO". What the AA965 crew did was type in "R", which brough up a list of matching waypoints, then simply hit "EXEC" twice, which sent them to the Romeo beacon near Bogota. The correct sequence was "R-O-Z-O-[EXEC]".

Conventional "feel" is what airplanes let you know when the pilot or "system" commands a change in flight path or rate of descent or.....

Agreed, but the basic tenet of the FBW Airbus design is that flight deck layout and feel should be common to all aircraft across the range, from the A318 to the A380. Traditional "feel" is an obstacle to that goal.

The biggest thing for we pilots was that the thing "felt" like what we all had flown for years.

Which is undoubtedly a good thing when you're talking about the first generation of a design. Boeing wisely made the 747 behave like a big Cessna, as it was the first airliner of that size.

But once the concept is proven, it makes sense to bring other parts of the technology a step forward. Based on experiments on a Concorde airframe (which was itself reliant on a primitive analogue FBW) with a spring-driven sidestick, Airbus elected to try the technology in a small narrowbody. The A320 airframe design was as conventional as they come (airliner airframe design having been mostly static for nearly four decades), but progression of the control system technology was the target.

While an ostensibly significant difference in flight deck layout, the design had pilot input from the get-go to make it feel relatively intuitive, and if pilot reaction to the control system had been negative, Airbus would have backtracked. Instead they were toe-to-toe with Boeing within a decade.

bubbers44
23rd Aug 2012, 01:58
So AF thinks it is a good idea to take an airliner at FL350 and pull up 15 degrees if the autopilot fails???? All our American airliners will stall so we don't do that. I guess theirs do too.

DozyWannabe
23rd Aug 2012, 02:07
Not exactly. "Skill" and "ability to cope with a crisis situation" are two very different traits.

TTex600
23rd Aug 2012, 02:11
Wow :mad:




[Editorial comment: Cockpit layout something for another thread, IMHO. My friend was the captain of the Cali disaster, and the stoopid FMS had duplicate designations for a fix. The two of them realized that somethig was awry when the coupled-autopilot turned the wrong way, but continued their descent after correcting their course. Can talk about that tragedy someplace else.]
As I understand it, it was the paper map that was in error, listing Rozo (the correct waypoint) as "R", when it should have been "ROZO". What the AA965 crew did was type in "R", which brough up a list of matching waypoints, then simply hit "EXEC" twice, which sent them to the Romeo beacon near Bogota. The correct sequence was "R-O-Z-O-[EXEC]".

You just proved your humanity, or lack thereof. Gums asked for this to be discussed elsewhere. Your obsessed desire to have something to say for every occasion has betrayed you. Sometimes it's just best to leave something alone.:mad:

Sorry Gums

DozyWannabe
23rd Aug 2012, 02:21
With all due respect, gums did not request that it not be discussed at all, and rather than open up a new thread on a topic that has been discussed many times before, I elected to summarize what I knew here as briefly as I could.

In this case the FMS did not have two waypoints programmed in with the same designator (as gums said), but caused a partial entry to bring up a list which was sorted in alphabetical order - a feature which crews of the time were not trained on. I explicitly stated that the initial error was in the map supplied to the crew, and not the responsibility of the crew themselves.

I've lost friends to accidents and worse, so I'd never knowingly be disrespectful of anyone who'd gone through the same, but in this case there was a factual error in the telling which needed to be explained.

Apologies if I caused any grief or offence.

bubbers44
23rd Aug 2012, 02:30
I flew the same type B757 into Panama City that night, no moon, and my FO was concerned about descending visually and said the highest obstacle from here is a sailboat mast. I flew into Cali a lot after that and they offered me that same south landing and I always declined. Not because it wasn't safe but in respect for the people that lost their lives by the pilots doing it. The R outer marker was the same at Cali and Bogota. They lost situational awareness and flew into the hills from the valley going to Cali. Yes it was their fault but the FMC made it so easy to make the mistake.

DozyWannabe
23rd Aug 2012, 02:34
bubbers44 - both they and you should never have been given charts marking the outer marker as "R". This was a misprint and the designation should have been "ROZO".

bubbers44
23rd Aug 2012, 02:45
Maybe now it is.

jcjeant
23rd Aug 2012, 03:35
Not exactly. "Skill" and "ability to cope with a crisis situation" are two very different traits. Exactly ...
Chief pilot say:
"This was pilots with maximum skill in the AF447"
But he will (nor AF) never admit that the "ability to cope" with the AF447 was not present
AF maybe train their pilots to have "maximum skill" but seem's they are not trained (or selected) to gain "ability to cope"
Maybe AF count on the 'luck factor" ?
Unfortunately luck is not always there when you need it in
Luck is something that deserves
Amundsen
Victory awaits him,who as everythings in order.
Luck we call it.
Defeats is definitely due for him,who has neglected to take the necessary precautions.
Bad luck we call it.
Three pilots who have no luck gathered by chance in the cockpit of AF447 ?
AF probably (maybe) thought it was not possible ... it is sometimes forgotten that there are some lotto whinners ....

gums
23rd Aug 2012, 04:13
Thank you, Bubs and Tex.

I shall never forgive my buddy for continuing the descent once they realized that the abbreviated FMS entry turned the AP the wrong way, and I have been amazed that anyone survived the "skip hit" on that mountain ( unlike the recent Suhkoi tragedy). Nick's final words are worth reading, and makes me cry. I lost other friends that had no clue about the rising terrain or the deficiency in the Viper auto pilot/FBW laws , 'nuff said on this.....

@<hidden> JCJ: "luck" is when preparation meets opportunity.

For many of us, it's "there but for the grace of God were I".

CONF iture
23rd Aug 2012, 04:55
The unilateral actions by the PF, within a second of the start of the UAS event do not conform to standard responses to abnormalities, nor did the actions of the PM as the problem rapidly degraded.
What do you want him to do when the bank is at 8 deg the attitude is 3 deg under a normal cruise attitude the altitude is 400 feet below the assigned FL and all of it under AP control ?

At the first warning, which is for AP disc, the guy grab the stick and follow the up FD command which is still visible for 3 seconds after that disconnection.

Never in that short period he can analyze that the problem is an unreliable airspeed indication. For the 30 previous known events, how many have called "UNRELIABLE SPEED" and applied the memory items ?

The initial action is necessary, what came after was not, the PF did not focus on the attitude and let the attitude to rise to 11 deg at a cruising altitude 10 seconds after AP.
The PM gave valuable indications but did not sufficiently prioritize the monitoring of the PF performance ... ECAM was calling him ...

CONF iture
23rd Aug 2012, 05:03
What were the PF's targets, and why would they have been different in direct law? Would direct law have prevented these targets to be achieved? Would there have been less "mayonnaise stirring"? Would direct law have prevented full sidestick deflection?
What direct law does ?
It’s here (http://www.pprune.org/7349864-post1154.html) but I can try to tell more :

As soon as the real speed bleeds, the nose wants to lower, it is a natural protection net.
If nevertheless the pilot wants to pull in order to achieve his targets, the aerodynamic let him know what kind of effort it takes on the sidestick. If mayonnaise there is, every down command will materialize in down elevator deflection.

To stall an aircraft in direct law just takes more effort than in a 1G command and the BEA does not disagree on that.

But let’s pretend the guy goes for full deflection before and during the stall ... and the PNF does not question anything of it …

THS is still at 3 deg and the stall cannot be that developed so the indicated airspeed won’t go below the threshold to silence the stall warning that will still warn when the captain is back. Of course if that captain had the chance to naturally contemplate what kind of input is made by the PF on the flight control commands … that could enormously help him to positively evaluate what’s going on here.

What many here like to call 'graceful degradation' had nothing of graceful during that night.
That law that trim and that sidestick concept worked against that crew that night.

HazelNuts39
23rd Aug 2012, 08:59
To stall an aircraft in direct law just takes more effort than in a 1G command and the BEA does not disagree on that.It took about 5 - 6 degrees of NU elevator to stall the airplane. In direct law that would correspond to about 3 degrees (2.8 lbf) of sidestick, vs about 2 degrees (2.1 lbf) in alternate law. Do you really believe the PF would have felt the difference in his erratic movements of the sidestick?

Lonewolf_50
23rd Aug 2012, 16:04
Doze, "skill" among pilots includes the set of "monkey skills" and set of "brain housing group and headwork" skills. Those two subsets are combined to create the larger set of "pilot skills."

I thus find the AF chief pilot's statement of dubious value. (If it has been translated properly).

I don't care how coordinated you are -- if your headwork is poor, brain doesn't work well while flying and you won't be much good at flying since you'll eventually run into something you should not.

Likewise, there are very well equipped (mentally) folks whose eye-hand-foot coordination renders them dangerous. We used to refer to them as "plumbers" back when I was a flight instructor.

Those skill groups come as a set, like the Lone Ranger and Tonto, or like Dolly Parton's left and right breasts.

You don't break up a set.

PJ2
23rd Aug 2012, 16:23
What do you want him to do when the bank is at 8 deg the attitude is 3 deg under a normal cruise attitude the altitude is 400 feet below the assigned FL and all of it under AP control ?
I'm not arguing that the initial response to the aircraft's (minor) bank (which he rapidly controlled), and the suddenly-lower indicated altitude. I am commenting on SOPs and CRM - I am observing what followed in terms of a crew response which was entirely non-standard, and upon this point we appear to agree. This is an observation, it is neither a judgement nor is it a statement of blame. Those kinds of statements are for others who are not doing flight safety work.

gums
23rd Aug 2012, 17:22
Very nice summary, Wolf-man.

I used to call them "mechanics", but "plumber" works as well.

My friends and I that survived twenty + years flying fighters had the combination of mental abilities, being able to think ahead of the jet, and decent hand-eye coordination. The mental component always seemed to me to be slightly more important than the Chuck Yeager "hands". But being able to fly the plane without thinking allowed folks like me to use what little smarts I had to survive and not become a smoking hole in the desert, or jungle, or a half mile short of the runway.

I soloed many troops that had marginal "hands", but they could think ahead and even if they couldn't hold speed within a knot or descent rate within 50 feet per minute, they were "safe" and effective and survived. 'nuff philosophy for now. But.....

"luck" is when preparation meets opportunity. I didn't see that on the part of the AF crew that dark night.

roulishollandais
23rd Aug 2012, 17:32
roullishollandais;

The way this system works is, these ACARS messages are not printed out on board the aircraft at the time they occur. They are transmitted to the airline's maintenance department in real time (timings as per early discussions on these messages), but are held in memory on the aircraft until the aircraft is parked at the gate, at which time a post-flight print-out occurs, which could and likely would include such ACARS messages. I have seen this many times
Thank you for your answer PJ2. I have seen the maintenance messages printed, and we can perfectly understand why the Captain wants to know that the next flight may be delayed due to maintenance :E. Another airline, another Captain. Would an AF Captain know the use of that ACARS printer ?

TTex600
23rd Aug 2012, 18:14
I used to call them "mechanics", but "plumber" works as well.

My friends and I that survived twenty + years flying fighters had the combination of mental abilities, being able to think ahead of the jet, and decent hand-eye coordination. The mental component always seemed to me to be slightly more important than the Chuck Yeager "hands". But being able to fly the plane without thinking allowed folks like me to use what little smarts I had to survive and not become a smoking hole in the desert, or jungle, or a half mile short of the runway.

I soloed many troops that had marginal "hands", but they could think ahead and even if they couldn't hold speed within a knot or descent rate within 50 feet per minute, they were "safe" and effective and survived. 'nuff philosophy for now. But.....

"luck" is when preparation meets opportunity. I didn't see that on the part of the AF crew that dark night.

The interesting thing is: Airbus fans think that the Airbus does allow them to "fly the plane without thinking" and I think that the Airbus requires me to think about flying instead of "flying without thinking". Perhaps more interesting is the fact that the previous pitot clogging incidents resulting in a positive outcome appear to have been "handled" by my kind of "fly without thinking" crews, while the accident crew appears (to me) to be the kind of pilots that think the Airbus allows them to fly without thinking. IOW's, both sides understand the need to "fly without thinking", but we have diametrically opposed views about the Airbus' contribution to that end.

I don't blame an Airbus style of flying pilot for feeling the way he does, I blame the business, training and regulatory environments that lied to him and told him that the Airbus "flys like any other airplane". See Operational Golden Rule #1.

Nothing I've ever previously flown (numerous commuter and transport category turboprops, various models of LearJets, DC9 and stretch DC9) required me, the pilot, to think about which mode the controls were in in order to properly fly the airplane.

Even with that said, I expect to spend the next fifteen years in an Airbus, then retire. I don't fear it, nor have disdain for it - nor do I trust it. I just wish that the books included a few simple statements. For example, "excepting a state when USE MAN PITCH TRIM in announced on the PFD, the SS is the sole allowable input for pitch. In degraded control states, significantly exaggerated pitch inputs may be required to effect the desired change" .
I've observed too many crews (from the jumpseat) and my own First Officers utilize the "slap the stick" method of control. The manuals should clearly indicate that this is undesirable, instead of the current FCTM language that states, "the PF needs to perform minor corrections to the sidestick, if the aircraft deviates from its intended flight path".

Personal experience shows me that smooth pressure applied to the stick results in adequate control. It also keeps my muscle memory trained to control the aircraft in a way that will be effective in aircraft with either (FBW or not) philosophy of aircraft control. The pilot who is trained to make minor corrections AS PER THE FCTM, is IMHO, poorly prepared to deal with situations that require true aircraft control inputs.

Lyman
23rd Aug 2012, 21:13
Instead of asking again for any Bus pilot to address "slapping" the stick, let me ask you, Tex.....

You say: "I've observed too many crews (from the jumpseat) and my own First Officers utilize the "slap the stick" method of control. The manuals should clearly indicate that this is undesirable, instead of the current FCTM language that states, "the PF needs to perform minor corrections to the sidestick, if the aircraft deviates from its intended flight path". "

I have called it "Quick Stick". 'Mayonnaise' is unsatisfactory, for it implies the action is not based on flying the aircraft....

"Slapping the Stick" works, so, is it similar to what I take it to be? I think it is a method of utilizing the controls such that the Angle of Incidence of the a/c is not affected by the THS. IOW, defeating the Autotrim.

We have seen video of it, I think, was it grity? It strikes me that if this is done to thwart the philosophy of Airbus, there may be a serious problem?

Muchas gracias amigo. Or as they say in Ft. Lauderdale: "Ah Swannee"

PJ2
23rd Aug 2012, 21:17
Would an AF Captain know the use of that ACARS printer ?
I can't say if AF captains know how to do this as I don't know any AF captains but as an A330 captain myself, (retired), on our A330's the printout was automatic after setting the park brake and if there were any maintenance messages printed out along with the entire flight summary (times, fuel, etc) we placed them between the thrust levers for either Mtc's awareness, (they would certainly know how to print these messages), and/or the next crew's awareness. Generally the knowledge is not required of flight crews because there are other means to communicate maintenance issues to the next flight crew, (usually the log book, of which an examination is required by the crew before flight).

That said, if the crew wished to know what the ACARS messages were while in flight, that is easy enough to do by navigating to the appropriate ACARS page summarizing these messages and printing that page. I've forgotten the details but it can be done though it isn't an automatic feature in the circumstances AF447 experienced, nor would there be sufficient time to examine the messages. Also, the "Stall" warning from the FWC is not part of the ACARS message system and would not be in any of the ACARS messages.

roulishollandais
23rd Aug 2012, 21:51
Thank you PJ2.
The Pitot fault message was on the ACARS at 02:10... and was missing on the ECAM!
Of course stall is not a ACARS message. But if one of the three pilots had seen that Pitot ACARS message it would have help the crew... to analyse the situation and they would have known immediatly they had to go to the UAS procedure.

jcjeant
23rd Aug 2012, 22:04
Hi,

TTex600
've observed too many crews (from the jumpseat) and my own First Officers utilize the "slap the stick" method of control. The manuals should clearly indicate that this is undesirable, instead of the current FCTM language that states, "the PF needs to perform minor corrections to the sidestick, if the aircraft deviates from its intended flight path". From the jumpseat ....
Interesting real life recount .. so do you suggest that the AF447 captain was able (like you) to see what were making the two other pilots with the SS ? (and was certainly able to see the position of the trim wheels dial)

TTex600
23rd Aug 2012, 23:17
jc, considering where the AF447 Capt reentered the picture, I doubt that he was looking at SS movement. However, I think it possible had he thought it necessary. I'd guess that he was overwhelmed trying to make sense of ECAM and flight instruments.

Lyman, I think it's just bad technique. I doubt that those who use said technique actually have a real clue about Airbus philosophy, no less have any desire to thwart it. They use it because it basically works in normal situations. A quick hit is all it takes. I prefer softer, more steady pressure; a technique which works as well.

PJ2
23rd Aug 2012, 23:22
roulishollandais;
The Pitot fault message was on the ACARS at 02:10... and was missing on the ECAM!
The pitot message was one of five fault messages (intended for Maintenance only - not presented to the crew). It is a Class I (of I, II, & III), Mtce Message and as such would require consultation with the MEL prior to the next departure. The pitot system itself did not fail in a way that was sensed by the FWC but due to blockage was providing erroneous data which was sensed by the EFCS2, (discussed in IRI, ppg 54, 55). The message is not an ECAM Level 1, 2 or 3 message and therefore would not have shown up on the ECAM because there was no "failure". If pitot heat itself had failed, a Level 2 message would be generated and it would show up as an amber message on the ECAM.

Whether this would have helped the PF comprehend what had happened cannot be stated. There seemed a predisposition to, and a determined focus on, certain actions in which the PM was unable to successfully intervene.

As to displaying an ECAM message with the abnormal, "Unreliable Airspeed" followed by suitable responses I cannot see that occuring within the current established ECAM philosophy. The reason is, I think, straightforward: The ECAM is a systems-abnormality page. It, and the Status Display page are intended to secure the aircraft systems for further flight within the limitations of the abnormality including performance additions or limitations where applicable. The ECAM system is not intended as a guide on how to fly the aircraft in certain abnormal circumstances - that is for the training regime to establish through the usual familiar ways.

bubbers44
24th Aug 2012, 02:04
Life is so much easier in a Boeing if UAS situation happens at altitude in cruise. Just keep the same attitude and power you had and get out the UAS check list. If the altimiter and VSI work you are even more golden. Not a real emergency at all. Just fly the airplane.

CONF iture
24th Aug 2012, 02:24
It took about 5 - 6 degrees of NU elevator to stall the airplane. In direct law that would correspond to about 3 degrees (2.8 lbf) of sidestick, vs about 2 degrees (2.1 lbf) in alternate law. Do you really believe the PF would have felt the difference in his erratic movements of the sidestick?
But what is the THS setting already when the elevators reach 5 - 6 degrees NU for the airplane to stall at the 10 deg of AoA time 02 11 00 ?

You may as well disregard the following BEA comment on P187 :
However, positive longitudinal static stability on an aeroplane can be useful since it allows the pilot to have a sensory return (via the position of the stick) on the situation of his aeroplane in terms of speed in relation to its point of equilibrium (trim) at constant thrust. Specifically, the approach to stall on a classic aeroplane is always associated with a more or less pronounced nose-up input. This is not the case on the A330 in alternate law. The specific consequence is that in this control law the aeroplane, placed in a configuration where the thrust is not sufficient to maintain speed on the flight path, would end up by stalling without any inputs on the sidestick. It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall.

Still, if the guy has direct law, he may as well bring the airplane to the stall, no question, but what do you make of the following ?

THS is still at 3 deg and the stall cannot be that developed so the indicated airspeed won’t go below the threshold to silence the stall warning that will still warn when the captain is back. Of course if that captain had the chance to naturally contemplate what kind of input is made by the PF on the flight control commands … that could enormously help him to positively evaluate what’s going on here.

What many here like to call 'graceful degradation' had nothing of graceful during that night.
That law that trim and that sidestick concept worked against that crew that night.
To that list of course I should have added that stall warning logic.

You did not comment ?
No one did ...

gums
24th Aug 2012, 04:37
You did not comment ?
No one did ...

Well, I shall comment. I know that Doze will bring up operational requirements and such, but I maintain I can contribute to the discussion.

It comes down to the control law implementation and then the natural stability of the jet.

Ours was negative static stability until about 0.95 mach. So the FBW system kept the pointy end forward. This is not the case with the 'bus. The thing has positive static stability unless the fuel transfer system goes awry. But HAL tries to provide a neutral speed stability ( no regard for AoA) and also corrects the basic gee command for pitch attitude. So the BEA comment is correct, with the exception that it should mention that the 'bus has inherent longitudinal static stability. In other words, go to "direct" law and the thing flies like most planes we have all flown ( not the Viper, which would be impossible without HAL).

Without some sort of stick pressure corresponding to the commanded gee as the jet slows down, then it becomes unclear as to what is happening. FOR THE ONE THOUSANDTH TIME....AoA is very important. AoA is what keeps the plane flying. So our primitive FBW system ( for the benefit of Doze, heh heh) had a neat AoA limit that kept you from stalling unless......... If you climbed at a steep attitude and reduced power, you could reach a speed where those air molecules and full nose down horizontal tail positions were not sufficient to prevent entering the stall. A true "deep stall", it was, due to our cee gee and pitch moment at 40 degrees AoA or so. Does this scenario sound familiar?

I disagree with the BEA terminology with respect to stability. The basic aero of the 'bus is fine. It's the FBW interference that makes the jet seem like it has neutral speed stability and static longitudinal stability. Go to "direct law" and you have what all planes have had since Wilbur and Orville flew the first one. Could be "touchy", but the sucker would try to achieve the trimmed AoA, and AoA is what planes use to provide those liftie doofers.

I do not recommend that the 'bus go from full laws to "direct law" willy nilly. But seems to me that a few practice sessions in the real jet in "direct law" would provide a lotta confidence to the crews and also show them the inherent characteristics of the jet.

HazelNuts39
24th Aug 2012, 08:02
But what is the THS setting already when the elevators reach 5 - 6 degrees NU for the airplane to stall at the 10 deg of AoA time 02 11 00 ?The airplane stalled at the 10 deg of AoA time 02 10 57. The THS was then at -3.5 degrees. Elevator 5 - 6 degrees should be read as equivalent elevator angle for THS = 3 degrees.

BEA quote: However, positive longitudinal static stability on an aeroplane can be useful since it allows the pilot to have a sensory return (via the position of the stick) on the situation of his aeroplane in terms of speed in relation to its point of equilibrium (trim) at constant thrust. Specifically, the approach to stall on a classic aeroplane is always associated with a more or less pronounced nose-up input. This is not the case on the A330 in alternate law. The specific consequence is that in this control law the aeroplane, placed in a configuration where the thrust is not sufficient to maintain speed on the flight path, would end up by stalling without any inputs on the sidestick. It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall. (End of quote)

The BEA comment is correct, of course. But in the circumstances of AF447 it is mostly theory. It applies if you approach the stall slowly, in still air at low altitude gently manipulating the stick so that you can feel the stickforce increasing the closer you get to the stall. The subtle change in stickforce characteristics hardly matters to a stressed pilot who jerks the stick backwards to increase pitch from 6 to 12 degrees in a couple of seconds. I quantified the difference in terms of stick angle and force.

Still, if the guy has direct law, he may as well bring the airplane to the stall, no question, but what do you make of the following ?

THS is still at 3 deg and the stall cannot be that developed so the indicated airspeed won’t go below the threshold to silence the stall warning that will still warn when the captain is back. Of course if that captain had the chance to naturally contemplate what kind of input is made by the PF on the flight control commands … that could enormously help him to positively evaluate what’s going on here.I agree with the first sentence, and wrote essentially the same in one of my recent posts. Regarding the captain, the stall warning is loud enough to be heard through a closed cockpit door. The captain must have heard it when he entered the cockpit.

jcjeant
24th Aug 2012, 09:10
I agree with the first sentence, and wrote essentially the same in one of my recent posts. Regarding the captain, the stall warning is loud enough to be heard through a closed cockpit door. The captain must have heard it when he entered the cockpit. CVR transcript
2 h 11 min 41,8

I have the
impression (we
have) the speed
SV : stall
2 h 11 min 42,4 SV : stall
2 h 11 min 42,5

Er what are you
(doing)?


Noise of cockpit
door opening

2 h 11 min 43,0
What’s happening? I
don’t know I don’t
know what’s
happening

cricket
2 h 11 min 44,5 SV : stall
2 h 11 min 45,5
We’re losing control
of the aeroplane
there The captain heard the stall warning ... an if he was in the rest station (who is just side the flight deck) he will have heard ( trough the wall ) this ( loud ) warning from about a minute ..
Of course .. as I'm certain .. he was not in the rest station .. unfortunately ( bad luck again ... )
In fact .. nobody know where he was ... not Robert who bell him and ask frantically for the captain return ... nor the BEA ....
And it's not Bonin preoccupation ... he have the hands full and more ....
Maybe shame for him but the best was that Robert make a general call "the captain is requested urgently in the cockpit" ... :(

DL-EDI
24th Aug 2012, 10:00
Life is so much easier in a Boeing if UAS situation happens at altitude in cruise. Just keep the same attitude and power you had and get out the UAS check list. If the altimiter and VSI work you are even more golden. Not a real emergency at all. Just fly the airplane.

Wouldn't that also work in other types, including the FBW Airbuses?

DozyWannabe
24th Aug 2012, 14:08
Wouldn't that also work in other types, including the FBW Airbuses?

Indeed. Several Airbus (and non-Airbus) guys advanced the fact that if the crew had left the controls alone for a few seconds at the point of autopilot disconnect, power and trim settings would in all likelihood have been maintained.

CONF iture
24th Aug 2012, 14:34
I do not recommend that the 'bus go from full laws to "direct law" willy nilly. But seems to me that a few practice sessions in the real jet in "direct law" would provide a lotta confidence to the crews and also show them the inherent characteristics of the jet.

Your experience makes you the most knowledgeable man here around on FBW and flight control laws.

Do not lose of sight that direct law is already practiced for every single early part of takeoff and every late part of landing by an Airbus pilot.
Direct law is also active after a number of malfunctions, which are encountered during usual training.
Direct law has been practiced during the initial training when only one Flight Control Computer was left ON to demonstrate how the Airbus behaves as a 'conventional aircraft'.
Also some exercises as LOST OF ELEV and MANUAL BACKUP go further that direct law as the main way to control pitch and overall performance is done through the THS ONLY (stick useless for pitch control).

Just to mention that direct law is not that wild thing.


But what I’m more interested here is how direct law would have simplified the all situation of AF447.

CONF iture
24th Aug 2012, 14:37
I agree with the first sentence, and wrote essentially the same in one of my recent posts. Regarding the captain, the stall warning is loud enough to be heard through a closed cockpit door. The captain must have heard it when he entered the cockpit.
You know better than that HN. You told me the other day I was maybe 'evading' the issue, it was not justified and as soon I could properly get what your point was, we were able together to bring the subject further.

So it is my turn to question : Are you evading the points of discussion ?

HazelNuts39
24th Aug 2012, 16:18
So it is my turn to question : Are you evading the points of discussion ?I don't think that I am evading any point of substance. I do have the feeling that, having clarified the facts, our discussion has reached the point were remaining differences are matters of opinion. Regarding matters of opinion, I am always reminding myself that I am an engineer participating in a pilot's forum. If there is a technical point to discuss, please be more specific.

TTex600
24th Aug 2012, 19:49
The BEA comment is correct, of course. But in the circumstances of AF447 it is mostly theory. It applies if you approach the stall slowly, in still air at low altitude gently manipulating the stick so that you can feel the stickforce increasing the closer you get to the stall. The subtle change in stickforce characteristics hardly matters to a stressed pilot who jerks the stick backwards to increase pitch from 6 to 12 degrees in a couple of seconds. I quantified the difference in terms of stick angle and force.

I'm probably in over my head here, maybe you guys are talking about some deeper issue, but....

I never tried to stall a transport category jet above 17500ft, so I must speculate, but I think you over rate the "subtleness" of stick force characteristics. I'll leave it up to the more research minded among us to find the regulatory standard, but if memory serves there is a minimum value of stick force per knot of deviation from trimmed speed. For the simple minded pilots out there, including me, that means that it takes an ever increasing amount of stick force to fly further and further away from trimmed speed. If the aircraft is trimmed for M80/260KIAS, and the pilot slows down, he must exert an not insignificant amount of force on the stick in order to maintain his new speed. Assuming of course that the aircraft does NOT trim automatically.

I think the BEA wording that you quoted is correct, and it is correct all of the time. It matters not whether you enter the stall from low and steady, or from high and unstable (flight path), either scenario in a "classic aeroplane" (BEA words) requires increased stick force to move and hold the airplane in the slower, approaching stall, situation.

The Bus, offering ZERO control feedback, denies its pilot, completely denies its pilot, this time tested tactile clue to airspeed.

The point I want to make is simple, in our scenario but in a "classic aeroplane" the pull necessary to stall the airplane would not have been "insignificant". In our scenario in the accident airplane, the pull force necessary to induce a stall was apparently "insignificant".

TTex600
24th Aug 2012, 19:57
Direct law has been practiced during the initial training when only one Flight Control Computer was left ON to demonstrate how the Airbus behaves as a 'conventional aircraft'.
Also some exercises as LOST OF ELEV and MANUAL BACKUP go further that direct law as the main way to control pitch and overall performance is done through the THS ONLY (stick useless for pitch control).



Maybe your sim instructor know tricks mine does not, but an Airbus MIA A320 Simulator with only one ELAC/SEC/FAC on handles like a truck with malfunctioning power steering and broken dampers.

The only way my instructor could force Dir Law left us with no roll control spoilers, slow ailerons, and resulted in an extremely unresponsive airplane.

Direct Law, in the manner some desire, would offer full control of all control surfaces, as its name implies, directly.

Lyman
24th Aug 2012, 20:56
TTex says...

"The point I want to make is simple, in our scenario but in a "classic aeroplane" the pull necessary to stall the airplane would not have been "insignificant". In our scenario in the accident airplane, the pull force necessary to induce a stall was apparently "insignificant"."

The pull force to induce STALL was certainly insignificant, and may I also add, 'irrelevant'. The aircraft wanted a gee, and found it, since at post STALL "free fall" it had it. at terminal velocity, the THS appeared content with one gee.....

The pilot input was never exactly in command. To be in command, one needs data, and shy of its full quiver, (notwithstanding the hue and cry re: instruments, which are not known, never will be...) PF had a STALL warn he was ignoring, feel that was not there, and a load of confusion that appeared in the form of FD.

People insist he had a Pitch cue, possibly so.... The CVR has the answers, probably in the "deemed irrelevant" category.... Captain heard the STALL warn plus cricket, he said nothing? My ass.....

bubbers44
24th Aug 2012, 23:05
Originally Posted by bubbers44

Life is so much easier in a Boeing if UAS situation happens at altitude in cruise. Just keep the same attitude and power you had and get out the UAS check list. If the altimiter and VSI work you are even more golden. Not a real emergency at all. Just fly the airplane.

Wouldn't that also work in other types, including the FBW Airbuses?

Yes it would but my neighbor Airbus captain said he might have done the same thing. What does AB training teach these people?

PJ2
25th Aug 2012, 00:05
bubbers44;

Your neighbour Airbus pilot likely has access to the Airbus-produced Flight Crew Training Manual. The FCTM has very clear guidance on how to handle the UAS abnormal and/or ADR failures.

The following, from an FCTM in early 2007, is the essential part of the response:

PART 1: MEMORY ITEMS
If the safe conduct of the flight is affected, the flight crew applies the memory items. They allow "safe flight conditions" to be rapidly established in all flight phases (takeoff, climb, cruise) and aircraft configurations (weight and slats/flaps).The memory items apply more particularly when a failure appears just after takeoff. Once the target pitch attitude and thrust values have been stabilized, as soon as above safe altitude, the flight crew will enter the 2nd part of the QRH procedure, to level off the aircraft and perform trouble shooting. This should not be delayed, since using the memory item parameters for a prolonged period may lead to speed limit exceedance.

PART 2: TROUBLE SHOOTING AND ISOLATION
If the wrong speed or altitude information does not affect the safe conduct of the flight, the crew will not apply the memory items, and will directly enter the part2 of the QRH procedure.

Airbus also produced the following in September, 2006:

http://www.iag-inc.com/premium/AirbusUnreliableSpeeds.pdf

rudderrudderrat
25th Aug 2012, 01:08
Hi PJ2,

Thanks for the link to ppt.
Can you please explain why both the QRH and ECAM in slides 19 & 20 say to turn the FDs OFF, (that action was not accomplished in AF744) yet the diagram clearly shows the FDs ON and with no pitch guidance annunciated.

bubbers44
25th Aug 2012, 01:49
Where has basic training gone? Has automation made them robots? I hope not but in this case it did.

PJ2
25th Aug 2012, 02:36
Can you please explain why both the QRH and ECAM in slides 19 & 20 say to turn the FDs OFF, (that action was not accomplished in AF744) yet the diagram clearly shows the FDs ON and with no pitch guidance annunciated.Nice catch!

No, I can't explain it but the indication is inconsistent - there is no "1FD2" or "--FD2" or "1FD--" in the FMA displayed yet as you've observed, the FD is "ON", (shown in the HDG-V/S mode vice FPV symbol and FP director).

It's not the first time I've seen oddities and inconsistencies in training materials though, and this one appears to be in development - who knows what its history is. The qualifying condition "Safe conduct of the flight affected?" is shown, "Defined during training" so there's obviously other training associated and a narrative that goes along with this one.

OK465
25th Aug 2012, 04:19
BUSS requires the 3 ADR's be physically deselected.

It's basically a recover (land) the aircraft and optimized for the approach mode.

Does the ISIS not have ILS capability with an ISIS FD?

...would this be similar and account for the limited FMA annunciations?

LOC* & GS arm are what's displayed...

Interesting.....and weird

edit: I would have sworn lateral and vertical are reversed on the FMA, but beer can create a feeling of more knowledge than one actually possesses. :)

grounded27
25th Aug 2012, 06:13
Forgive my direct question but should not the PF maintained wings level pitch and power settings for unreliable a/s. Damn Airbus, seems like both pilots were more concerned with interpreting ECAM failures than flying the damn plane??????Don't think this would happen with analog pilots in an analog aircraft or simply an analog pilot reverting to simple piloting skills. Why would you even trust FD in this event?

I understand the panic in severe turb.

Having said that, I suspect the pitot's froze up due to insufficent heating, possibly as a result of insufficent pitot heat. Wiring, pitot elements.. I question?? Not enough lead in the pencil is my question as the pitot probes go..

jcjeant
25th Aug 2012, 08:32
BUSS requires the 3 ADR's be physically deselected.This instrument (virtual BUSS) is present and works even when the 3 ADR's are activated :)
It handles all kinds of protections AOA of the Airbus (Alpha prot .. Alpha floor .. etc. ..) in normal law :ok:
This instrument is hidden .. pilots do not see him :rolleyes:
The problem is that when the aircraft leaves the normal law ... this (virtual) instrument stops working :uhoh:

DL-EDI
25th Aug 2012, 11:23
Damn Airbus, seems like both pilots were more concerned with interpreting ECAM failures than flying the damn plane??????Don't think this would happen with analog pilots in an analog aircraft or simply an analog pilot reverting to simple piloting skills.


Why Airbus in particular? Are modern flight decks on other types much different? Did "analogue" flightdecks provide better information in unreliable airspeed situations, for example?

I'm sure I'll be labelled an Airbus "fanboy" by some but, as someone outside the industry, I guess I'm just having difficulty understanding why an incident with a FBW Airbus prompts so many to crawl over the entire design to find fault while similar incidents involving other types (e.g. inappropriate reaction to stall warning, loss of air data) result in more focus on crew actions. Oh well, I'm here to learn.

Having said that, I suspect the pitot's froze up due to insufficent heating, possibly as a result of insufficent pitot heat. Wiring, pitot elements.. I question??

I can't vouch for this particular series of threads but elsewhere the discussions seem to indicate that the Thales pitots used on AF447 met certification standards but not by as much of a margin as the later Thales and the Goodrich pitots. It's also my understanding that there was no indication of any electrical fault.

john_tullamarine
25th Aug 2012, 12:32
Did "analogue" flightdecks provide better information in unreliable airspeed situations, for example?

You're missing the point or misunderstanding the problem a little, I think.

The older style aircraft (which happened to have analogue kit due to the available technology) generally were crewed by pilots who did a lot of hand flying - often raw data (ie without any "helpful" gadgets) - and didn't need autopilots, flight directors, and autothrottles to think for them.

Even with such gadgets, we tended to "look through" the flight director, for instance, and fly much the same as we would without one using the old-fashioned I/F scan processes - the flight director helped a bit by assisting the on-the-fly decision processes but was not followed blindly and without pilot thought.

Hence if an ASI problem arose, we just kept doing what we had been doing without the use of one of the usual set of information sources .. just meant we paid more emphasis to pitch attitude (on the AH or whatever term was used for that installation) and engine thrust settings .. and it all just sort of worked out fine.

However, maintenance of the skills required practise. The risk in modern aircraft is that these skills are lost.

DL-EDI
25th Aug 2012, 13:03
You're missing the point or misunderstanding the problem a little, I think.

Fair enough, but my main point of contention is: why "Damn Airbus" rather than "Damn modern flight decks"? Why "Damn Airbus" rather than "Damn modern training that apparently doesn't make appropriate use of pitch and power second nature to every crew in the absence of airspeed data"?

john_tullamarine
25th Aug 2012, 13:21
Oh, indeed .. and you are absolutely correct.

Linktrained
25th Aug 2012, 13:56
Mandatory RVSM with its potential lowering of the bottom cruising level makes it difficult for pilots to manually handle their aircraft at cruising levels. It ought to be possible for Air Traffic Control to release aircraft from this requirement for a finite period when and where ATC can allow. Not all airspace is always busy throughout the 24 hours. ( A simple example is the Aeropostal night flights from Paris, when and where much of the area is virtually empty. )
Not all flights are from busy areas or at times when they are busy.
( On another thread someone mentioned that their airline arranged that their pilots did two sessions of manual flying as well as a further couple of sessions in the sim doing all the mandatory stuff, annually.)
Some of the " analog" aircraft tended to have higher weather minima ( when these were laid down, I think, in the 1950s). One Captain used to say that he would overshoot when he saw his F/O "BRACE"... But he may have been joking !

In 1975 when most Jet cruising levels were 2000ft apart, in discussion with the UK Authorities, I was told that they were considering reducing this to 1500ft to allow more flights to cruise nearer their own optimum levels.

grounded27
25th Aug 2012, 15:30
Not my intent (Damn Airbus) that is. Damn ECAM should have been the statement, it seems like it did more harm than good in this situation. I do feel though that the Airbus ECAM system is like the nagging wife who won't just STFU. It is the pilot's responsibility to fly the aircraft, it seems obvious to me that the PF as John and I had stated was not able to revert to simple pitch and power flight. Disconnect the automation, ignore the flight director.

As for the pitot tubes, I have my doubts. I do know that AB is big on using the smallest gauge wire possible for weight savings. A good heater draws current. Just a suspicion of mine. I will post on eng and tech as I do not have access to A330 WDM's myself. I have been curious what gauge wire the heaters use.

CONF iture
25th Aug 2012, 15:53
I don't think that I am evading any point of substance. I do have the feeling that, having clarified the facts, our discussion has reached the point were remaining differences are matters of opinion. Regarding matters of opinion, I am always reminding myself that I am an engineer participating in a pilot's forum. If there is a technical point to discuss, please be more specific.
"Do you really believe the PF would have felt the difference in his erratic movements of the sidestick?"

As elevator deflection is proportional to stick deflection, any erratic movements of that stick tend naturally to disappear especially when speed is still high or a price has to be paid on the human body.
Direct law allows the pilot to be more aware of the consequences of his inputs on the stick.

THS at 13 deg instead of 3 deg is an elephant in the room.
Direct law would not have allowed its presence.

Any release of the stick, not to talk about push command, would have provoked an immediate ND change in the attitude.
Direct law would not have allowed to go that easily to the stall and would have favorized an exit from that stall.

"Regarding the captain, the stall warning is loud enough to be heard through a closed cockpit door. The captain must have heard it when he entered the cockpit."

There is no doubt the captain has heard the stall warning, but more than anything there is no doubt the captain has heard the stall warning STOPPING which played enormously in his inadequate evaluation of the situation.
Direct law would have prevented that warning to erroneously quit.

Last point but not the least, the sidestick concept did hide to the PNF initially, and then to the captain + PNF what the PF inputs were and how those were inappropriate at times.


All those points had to be thouroughly developed by the BEA, and not only superficially for some and completely ignored for others.
As written earlier, that law that trim that stall warning logic and that sidestick concept worked against that crew that night.

CONF iture
25th Aug 2012, 15:57
Maybe your sim instructor know tricks mine does not, but an Airbus MIA A320 Simulator with only one ELAC/SEC/FAC on handles like a truck with malfunctioning power steering and broken dampers.
The only way my instructor could force Dir Law left us with no roll control spoilers, slow ailerons, and resulted in an extremely unresponsive airplane.
I can’t tell for the 320, but for the 330, according to the flight control architecture, PRIM 1 or 2 maintain one pair of ailerons + 1 pair of spoilers for roll control + both elevators.
I have no memory of sluggish control, but would have probably to experiment it again.
Direct Law, in the manner some desire, would offer full control of all control surfaces, as its name implies, directly.
That would be a great thing, one simple guarded switch to force direct law. But I don’t see that in the Airbus philosophy where the airplane is supposed to take care of the pilot, not the pilot to dare doubting the technology …

OK465
25th Aug 2012, 16:19
Max roll rates of 25 degrees/s in Direct versus 15 degrees/s in Normal would seem to indicate the 330, at least, is more responsive in Direct.

THS 13 versus 3:

During specified sim stall QTG's (Direct, fixed THS), with SS full aft, AOA's run about 15-20 degrees less than the FDR values from the report.

As might be expected very similar to, for example, 727 or 737 AOA values. FPV if selected never leaves the PFD display FOV at these values.

Lyman
25th Aug 2012, 16:28
PJ2....thank you sir, for your kind and weighty response. I am giving it the time it deserves, and the state of my brain allows. Your patient responses are waypoints on a voluminous journey.

TTex600.. INRE: Poor technique, "Mayonnaise", and "bump and suss". I think it may be more prevalent than we think? It looks suspiciously like an evolved and ad hoc response to Airbus flight controls....

It resembles "Pilot induced turbulence". Over controlling to goad the aircraft into giving up some feel, as it were. Or to make "minor" corrections in flight path?
As per FCTM? Unusual it has received little attention here. In other aircraft it would not make it past first flight in type?

You have seen it? Could you enlarge on your experience with it? It seems horrendously out of touch with such a sophisticated airplane and her philosophy?

Similarly, it presents as reactive and defensive....no one would fly a Boeing in similar fashion.

TTex600
25th Aug 2012, 17:20
Fair enough, but my main point of contention is: why "Damn Airbus" rather than "Damn modern flight decks"? Why "Damn Airbus" rather than "Damn modern training that apparently doesn't make appropriate use of pitch and power second nature to every crew in the absence of airspeed data"?



Agreed, with the addition that the AirBus integrated FlightDirector/AutoThrust system REQUIRES one to follow the FD's otherwise the AutoThrust becomes confused. This characteristic, that is Airbus specific I believe, forces the pilot to concentrate largely on the FD. That FD "focus" requires that Airbus training is largely void of pitch/power reliance. In that sense, the airplane is at least part of the problem.

My fix is simple, if you turn one automated system off, get ready to turn ALL of them off. A/P OFF, A/T OFF, FD's OFF. Works quite well.;)

HazelNuts39
25th Aug 2012, 17:23
Confiture,

Just to defeat the notion of 'evasion':

As elevator deflection is proportional to stick deflection, any erratic movements of that stick tend naturally to disappear especially when speed is still high or a price has to be paid on the human body.Considering the inertia of the airplane, I'm not so sure of that. Perhaps you should try it in your next simulator opportunity.

THS at 13 deg instead of 3 deg is an elephant in the room.
Direct law would not have allowed its presence.I suppose you mean that there is no autotrim and that you assume that the PF would not have trimmed manually. At 02:11:35 he seemed pretty desperate to keep the nose up, and in direct law "USE MAN PITCH TRIM" is displayed on the PFD.

Any release of the stick, not to talk about push command, would have provoked an immediate ND change in the attitude.
Direct law would not have allowed to go that easily to the stall and would have favorized an exit from that stall.In the two instances that the PF released the stick, the elevator responded and the airplane promptly pitched ND.


There is no doubt the captain has heard the stall warning, but more than anything there is no doubt the captain has heard the stall warning STOPPING which played enormously in his inadequate evaluation of the situation.
Direct law would have prevented that warning to erroneously quit.While it is probable that the stall warning would have been uninterrupted in direct law, that is not certain.

Last point but not the least, the sidestick concept did hide to the PNF initially, and then to the captain + PNF what the PF inputs were and how those were inappropriate at times.I have earlier expressed my opinion on the visibility of the sidestick. Seeing the control pulled to the back stop might have added another clue that might have pointed the PNF and particularly the captain towards a correct diagnosis of the situation.

All those points had to be thouroughly developed by the BEA, and not only superficially for some and completely ignored for others.Perhaps you would care to justify that opinion considering that BEA's investigations "are conducted with the sole objective of improving aviation safety and are not intended to apportion blame or liability."

TTex600
25th Aug 2012, 17:25
Max roll rates of 25 degrees/s in Direct versus 15 degrees/s in Normal would seem to indicate the 330, at least, is more responsive in Direct.

That would depend on how the airplane arrived at Direct Law. If it goes direct because of compounded flight control computer failure, you are left with reduced control surfaces and the aircraft response will be reduced. If it goes direct because of something other than computer failure, it might retain full control surface complement and be quite responsive.

TTex600
25th Aug 2012, 17:37
TTex600.. INRE: Poor technique, "Mayonnaise", and "bump and suss". I think it may be more prevalent than we think? It looks suspiciously like an evolved and ad hoc response to Airbus flight controls....

It resembles "Pilot induced turbulence". Over controlling to goad the aircraft into giving up some feel, as it were. Or to make "minor" corrections in flight path?
As per FCTM? Unusual it has received little attention here. In other aircraft it would not make it past first flight in type?

You have seen it? Could you enlarge on your experience with it? It seems horrendously out of touch with such a sophisticated airplane and her philosophy?

I've slept at least once since writing about poor technique, and I'm in a bit of a hurry at present. With that said, "Mayonnaise" differs from the "slap the stick" method to which I refer. Mayo would be akin to full scale deflections and opposite full scale deflections in the opposite direction (made in my opinion due to the lack of a link from stick to controls. Sometimes one wants more roll and ends up at full SS deflection which then requires full opposite stick and back and forth) where slapping the stick is minor corrections made somewhat like a 16 point roll performed by a world class aerobatic pilot.

I brought that up as an example of something the FCTM should discourage vs encouraging.

But for now, I've got to get back to planting my fall garden.

Linktrained
25th Aug 2012, 18:16
A very much earlier comment, from a couple of thousand years ago, was:
" Do not let your left hand know what your right hand is doing."
Whilst this was related to giving, charity, in aviation terms it could mean information from one pilot to another.
PF was, presumably, using his right hand. PNF was able to comment on stirring the Mayonnaise, scarcely on the use / abuse of NU.
They had a couple of minutes to "Permutate the Possibilities", as a Royal Flying Corps pilot would have put it.

Turbine D
25th Aug 2012, 18:38
Lyman,

Here are a couple of clips of hand flying a Boeing 737 near landing at lower speeds. In the second clip, the PF is in the left hand seat but you can see the yoke movement over the shoulder of the PNF in the right hand seat . There are no clips of hand flying at altitude or high speeds as the AP does that. I would imagine at higher speeds and thinner air, manual flying (hand movements) of either the stick or yoke would need to be highly finessed (light touch) just as maneuvering at high speed in your car would require so as not to experience LOC. I threw in one Airbus clip just for example to go with the Boeings. Note in the Airbus, you can observe the trim wheels turning as you do in the Boeings.
Cheers!
Simone lands her B737-800 at Helsinki - YouTube
Manual landing Boeing 737NG - YouTube
FIRST OFFICER IN ACTION! (APPROACH SBEG) - YouTube

OK465
25th Aug 2012, 19:33
That would depend on how the airplane arrived at Direct Law.

TTex: Point taken, I'll do a little research...

(There certainly is a lot of RED on the right ND in that NG video. :eek:)

jcjeant
26th Aug 2012, 02:22
Sorry if already posted (consider as a reminder .. )
Aero 12 - Angle of Attack (http://www.boeing.com/commercial/aeromagazine/aero_12/attack_story.html)

bubbers44
26th Aug 2012, 04:05
G27, the pilots didn't follow the AB manual and if they were above obstacles not do the low altitude procedure but do the cruise prosedure of just hold present attitude for level flight and get out the UAS check list. They were new and inexperienced. They needed the only qualified pilot in the airplane to be in the cockpit but he was taking his break and they couldn't handle it. Hiring 300 hr pilots on automatic airplanes is not safe.

BOAC
26th Aug 2012, 08:57
Flap flap flap:mad: They were new and inexperienced. - no they were not (for the fithtieth time). They were not '300hr' pilots (for the thirtieth time..They needed the only qualified pilot in the airplane - they WERE 'qualified'.

For g27 I understand the panic in severe turb. - there was NO severe turb

Either of you read the report?
B44 page 29 et seq
G27 page 60

Give it a break?

Mr Optimistic
26th Aug 2012, 10:21
This sidestick visibility thing is all well and good but I do not understand why the cpt didn't at least ASK the pf what he was doing never mind instruct him as to control inputs. There were enough pax behind him, situation didn't need one more.

CONF iture
26th Aug 2012, 14:28
Considering the inertia of the airplane, I'm not so sure of that. Perhaps you should try it in your next simulator opportunity.
Every rotation is done in direct law, and any undesirable erratic movement would be immediately evident due the instantaneous response of the aircraft.

I suppose you mean that there is no autotrim and that you assume that the PF would not have trimmed manually. At 02:11:35 he seemed pretty desperate to keep the nose up, and in direct law "USE MAN PITCH TRIM" is displayed on the PFD.
Did he try to trim up to the FULL stop of 14 degrees ... ?
If the pilot wanted to trim up, let him make such a silly thing himself, Please. We really don’t need any automation to do it for him.
If the guy had done it himself, I would not show up here to defend his action.

In the two instances that the PF released the stick, the elevator responded and the airplane promptly pitched ND.
And nothing to compare with what would have been obtain in direct law in terms of ND movement and AoA reducing in order to achieve stall exit.

While it is probable that the stall warning would have been uninterrupted in direct law, that is not certain.
If you think you can get below 60 knots on elevators only, it is your call. What I want to see is the BEA calling the shot. That should be detailed already.

I have earlier expressed my opinion on the visibility of the sidestick. Seeing the control pulled to the back stop might have added another clue that might have pointed the PNF and particularly the captain towards a correct diagnosis of the situation.
So we agree.
It was the duty of the BEA to make recommendations to Airbus to include in their documentation how the sidestick concept does not permit the same type of supervision allowed by more conventional flight control commands.

The crews operating the Airbus must be made aware of such characteristic.

Perhaps you would care to justify that opinion considering that BEA's investigations "are conducted with the sole objective of improving aviation safety and are not intended to apportion blame or liability."
That's something we can keep for later, but for now I could resume it that way : Do not write too much in the technical as the judiciary could be too well at ease to use it afterwards …

CONF iture
26th Aug 2012, 14:34
This sidestick visibility thing is all well and good but I do not understand why the cpt didn't at least ASK the pf what he was doing never mind instruct him as to control inputs. There were enough pax behind him, situation didn't need one more.
As soon as the captain is back, the stall warning quits. For him a stall has been properly exited. He has no clue the stall warning can quit for other reasons than a stall exit. The Airbus documentation makes absolutely no mention of anything like it, and on the contrary it is specified that a stall warning won’t stop before a stall is actually exited, which follows both regulation and logic.

This stall warning thing puts everything up side down for the captain ability to properly evaluate the situation.

What do you want him to instruct if he cannot make sense himself of the situation ?

But it is a remarkable that the captain would need to ask the PF what he was doing, just because the sidestick concept deprives him to naturally know about the inputs made on the flight control commands.

jcjeant
26th Aug 2012, 14:53
Interesting and neat report about AFR1896 (from the Moroccan investigation authority)
Only in french unfortunately
http://89.30.127.37/docspa/2011/f-xc110808/pdf/f-xc110808.pdf
The event is from last year
This show again a real problem at AF about CRM .. respect of the laws .. etc ...
Extracts (Google translator)

1. RENSEIGNEMENTS DE BASE

1.1.- Déroulement du vol

Le 08 août 2011, l’avion Airbus A320 de la compagnie Air France assurait le vol commercial
N° AFR1896, en provenance de l’aéroport Paris Charles-De-Gaulle (CDG) à destination de
l’aéroport de Casablanca Med V (CMMN) selon horaires suivants : Heure de départ : 5h30 UTC,
Heure d’arrivée : 8h24UTC

A 08h10mn05s, l’équipage du vol AFR1896 prend contact avec l’Approche GMMN. L’approche
lui notifie de procéder sur le point GODAM, de descendre au FL50 et de prévoir un guidage
pour la piste 35L. L’équipage accuse réception.

08h15mn59s : l’Approche demande à l’équipage de descendre à 3000 pieds QNH 1013.

08h18mn27s : l’équipage AF1896 annonce qu’il est en vue des installations pour une approche
à vue. L’approche approuve et demande à l’équipage de continuer à vue pour une finale 35L.

08h19mn56s : l’approche demande à AFR1896 de tourner en final 35 L et de contacter la Tour
sur 118.5.

08h20mn08s : après prise de contact avec la Tour, celle-ci demande à l’équipage du vol
AFR1896 de rappeler en finale 35 L.


08h22mn05s : AFR1896 confirme qu’il est « Autorisé à atterrir sur la 35 Gauche »

08h24mn24s : Une autre station annonce pour information qu’un avion d’Air France a atterri
sur la piste 35 droite.

08h24mn46s : AFR1896 confirme l’information : « Oui 1896 on vous a bien reçu, et on espérant
l’approche à vue, effectivement on s’est trompé de piste en approche à vue merci. »

1. BACKGROUND

1.1. - History of Flight

August 08, 2011, the Airbus A320 of Air France operated the flight business
No AFR1896, from the Paris Charles De Gaulle (CDG) to
Airport Casablanca Med V (CMMN) according to the following schedule: Start Time: 5:30 UTC
Arrival: 8h24UTC

A 08h10mn05s, the flight crew will contact AFR1896 Approach GMMN. The approach
it shall proceed Godam about to descend to FL50 and provide guidance
track for 35L. The crew acknowledged.

08h15mn59s: Approach asked the crew to descend to 3000 feet QNH 1013.

08h18mn27s: AF1896 crew announces that it is to approach facilities
sight. The approach approve and asked the crew to continue to a final 35L for.

08h19mn56s: the approach requires AFR1896 final turn of 35 L and contact the Tour
of 118.5.

08h20mn08s: after making contact with the tower, it asks the flight crew
AFR1896 to recall the final 35 L.


08h22mn05s: AFR1896 confirms that it is "authorized to land on 35 Left"

08h24mn24s: Another station announcement information for Air France plane that landed
on runway 35 right.

08h24mn46s: AFR1896 information confirms: "Yes, in 1896 you were well received, and we hope
visual approach, it is actually the wrong track approach to thank you. '

1.13.3 Témoin oculaire :

Le Commandant de bord du vol N°AT560 a remarqué au cours du son roulage que
l’avion assurant le vol AF1896 était haut sur le plan et mal aligné sur la 35L. Il a donc
décidé de ne pas traverser la 35R pour s'aligner sur la 35L malgré l'autorisation initiale
de la TWR/GMMN.

A la suite de l'atterrissage de l’avion de la compagnie Air France (Vol N°AF1896) sur la
piste 35R, le CDB du vol AT560, qui était au point d'attente 35R, a informé la TWR de cet
événement.
1.13.3 Eyewitness:

Commander of flight AT560 No. noticed during his driving that
the aircraft on the flight AF1896 was high on the plan and misaligned on the 35L. He therefore
decided not to cross the line to 35R 35L despite the initial authorization
the TWR / GMMN.

After landing the plane of Air France (AF1896 Flight No.) on
runway 35R, flight AT560 the CBD, which was at the holding point 35R, informed the TWR this
event.


1.10 Enregistreurs de paramètres de vol
1.10.1 Cockpit Voice Recorder (CVR) :
Le CDB n’a pas appliqué les consignes de la compagnie Air France (AF) dans le cas d’un
incident grave, ce qui n’a pas permis d’exploiter les données CVR de l’avion en question
au moment opportun.
1.10 Recorders flight parameters
1.10.1 Cockpit Voice Recorder (CVR):
The CBD has not applied the instructions of Air France (AF) in the case of a
serious incident, which did not exploit the CVR of the aircraft in question
timely.2.3. Procédures Air France en cas d’incidents grave :
Le Manuel d’exploitation de la compagnie Air France précise les mesures à
entreprendre par le CDB responsable du vol dans le cas d’incident grave, notamment
en ce qui concerne la protection des données de CVR. Il est mentionné dans le manuel
de la compagnie Air France qu’une fois l'avion immobilisé au sol, il faut tirer et baguer
les disjoncteurs correspondants aux différents enregistreurs selon les consignes du
MANEX B, et le mentionner sur I'ATL, chose qui n’a pas été faite par le CDB de ce vol, ce
qui n’a pas permis aux enquêteurs de vérifier toutes les communications dans le
cockpit durant l’approche et l’atterrissage.
Il est à noter que le règlement en vigueur classe cet événement comme incident grave,
par conséquent, l’équipage de conduite devrait le traite comme tel.
Par ailleurs, le responsable de l’escale d’Air France, à l’aéroport de Casablanca
Mohammed V, s’est contenté d’accompagner le CDB du vol AFR1896 au bureau de
piste pour la rédaction du relevé d’infraction et d’en conserver une copie.
2.3. Air France procedures in case of serious incidents:
Operations Manual for Air France specifies the measures to
undertaken by the CBD responsible for the theft in the case of a serious incident, including
regarding data protection CVR. It is mentioned in the manual
of the Air France plane that once grounded, pull and band
breakers corresponding to different recorders according to the instructions of the
MANEX B, and the mention of I'ATL, something that has not been made ​​by the CBD that flight
which did not allow investigators to verify all communications in
cockpit during the approach and landing.
It should be noted that the regulation in force class this as a serious incident,
therefore, the flight crew should treat it as such.
In addition, the head of Air France station at Casablanca airport
Mohammed V, was content to accompany the flight AFR1896 CBD office
track record of drafting the offense and keep a copy.
timely.3.1 Faits établis :
.......
· L’avion était haut et rapide par rapport à la trajectoire nominale d’approche.
· L’absence des enregistrements des conversations dans le poste de pilotage pendant cet
incident n’a pas permis de clarifier certains détails de l’événement, notamment la tenue
de briefing avant l’approche ;
· L’attitude du CDB n’était pas en cohérence avec les bonnes pratiques en matière de
gestion des ressources dans le poste de pilotage.
· L’avion a atterri sur une piste non assignée (la piste 35 R au lieu et place de la piste 35L);
· Le CDB n’a pas appliqué les consignes de la compagnie Air France (AF) dans le cas d’un
incident gave ce qui n’a pas permis d’exploiter les données du CVR en temps opportun.
3.1 Findings:
.......
· The aircraft was high and fast compared to the nominal trajectory approach.
· The absence of recordings of conversations in the cockpit during this
incident has not helped to clarify some details of the event, including the holding
briefing before the approach;
· The attitude of the CBD was not consistent with good practices
resource management in the cockpit.
· The plane landed on a runway unassigned (runway 35 R in lieu of runway 35L);
· The CBD has not applied the instructions of Air France (AF) in the case of a
incident which gave no license to operate the CVR timely.

bubbers44
26th Aug 2012, 15:06
BOAC, for the 50th time, they were hired with low time and monitored Airbus autopilots for years until their actual piloting skills were required with no autopilot and they failed. They could not hand fly.

BOAC
26th Aug 2012, 17:37
they were hired with low time - I've heard tell a lot of pilots start with 'low time', and in the 21st Century where most of us live, they then monitor autopilots for years (including the AF447 Captain).

They were NOT 'new and inexperienced' - get your terminology right - unless, of course, you consider 10 years on AB, 39 SA route rotations and 6500 hrs 'new and inexperienced'?

It seems you may have dozed off for a decade or two. Exactly WHAT do you expect a crew to have as minimum 'experience'?

"They could not hand fly." That much is obvious, but I would add for accuracy "They could not hand fly an AB340 in Alt Law.". How they would have fared in a different a/c we will never know.

bubbers44
26th Aug 2012, 19:17
I guess this is a waste of time but in my 23,000 hrs my airline never required me to be on autopilot and monitor it 95 % of the time and only take off and some times land manually. I always hand flew enough to know I could do what the autopilot quit doing. These two couldn't and what they did by pulling up into a full stall shows what automation does if you don't maintain basic flying skills.

bubbers44
26th Aug 2012, 19:32
BOAC, you are wrong even though you have 10 times the posts I have. No pilot should depend on automation if he can't do it himself. Yes I am in the 21st Century too but letting automation make you a monitor and not handle a simple situation like they had, UAS, isn't the answer. If the automatic stuff quits it is no big deal unless you don't know how to fly.

jcjeant
26th Aug 2012, 19:37
I think whoever said (Ziegler) that Airbus could be controlled ( monitored ? ) by his concierge was right
He just forgot to say that it was the plane had to be configured on autopilot and normal law

RetiredF4
26th Aug 2012, 19:52
Quote CONFiture
Any release of the stick, not to talk about push command, would have provoked an immediate ND change in the attitude.
Direct law would not have allowed to go that easily to the stall and would have favorized an exit from that stall.

HazelNuts39: In the two instances that the PF released the stick, the elevator responded and the airplane promptly pitched ND.

Quote CONFiture: And nothing to compare with what would have been obtain in direct law in terms of ND movement and AoA reducing in order to achieve stall exit.


@<hidden>
To emphasis CONFiture´s position: Elevator only reduced from full NU to 15° NU (time 02:12.46 and 02:13:55) after a significant time delay, whereas in direct law the elevators would have responded immidiately according to the SS position, meaning SS neutral, elevators neutral, SS Full ND (02:12:32, 02:13:40) elevators equivalent full ND. Just superimpose the SS command over the elevator position and the outcome is obvious.

HazelNuts39
26th Aug 2012, 21:20
RetiredF4;

Thanks for emphasizing Confiture's position. I was aware of that when I wrote my reply. But would a brisker response of the airplane have altered what the PF was trying to achieve? Have you considered why he briefly released his pull on the stick? I submit he did because the airplane pitched up when he increased thrust. Nothing indicates that he had any intention to get the nose down to an angle that would have unstalled the airplane. When the attitude reached 8 degrees and stopped increasing he started pulling again and kept pulling for over a minute. Yes, the airplane would probably have responded more briskly in direct law, but it is somewhat of a stretch to say that that would have changed everything.

RetiredF4
26th Aug 2012, 22:18
HazelNuts39
But would a brisker response of the airplane have altered what he was trying to achieve? Have you considered why he briefly released his pull on the stick?


To answer that question we would have to come to a conclusion, what PF tried to achieve firsthand. Neither BEA nor our efforts here come to a final result.

Several options had been discussed here, and can be grouped into the intentional climb and the unintentional climb. By that i refer mainly to the amount and intensity of the climb, not the climb as the opposite of the descent or the equivalent of an maintaining level. That the PF intended at least to correct the indicated altitude loss and the deviating pitch and VS should be agreed to. Everything else later on is not clear anymore.

If the climb in that intensity was intentional, then nothing would have influenced or changed the end result. But do we have ultimate proof of that theorie? I dont think so. When PNF told the PF to go down, he acknowledged to do so, he did not argue against the PNF, although he didn´t comply in deeds. Was he not willing to do so or was he not capable to do so (intention to do so was present, but the means to accomplish it were unsuitable)?

We know almost, that the manual flying expierience of the PF on the A330 was mainly accomplished during takeoff and landing. In T/O it´s afaik comparable to a direct law behaviour, and during landing phase when SS inputs are necessary close to ground it´s flare law. During flare law the PF is maintaining the trajectory by compensating the system induced ND force by a NU SS input, and to reduce the trajectory he just has to relax some of this NU SS input. The normal feeling on the SS from day to day flying therefore is holding some backpressure to maintain the flightpath during landing or to rotate and climb during T/O. The necessity of ND SS input and the required amount of ND SS input in normal daily operation therefore differed grossly to that one needed to correct this unintentional climb.

Additionally in day to day flying the roll channel doesn´t need much attention, except when a change of direction is desired, but otherwise the aircraft is stable in bank. PF was occupied by getting the wings back to level and maintaining them there, with roll law in direct a task he was not used to do. He might have associated the prooblems in achieving the correct pitch with the deviations in changing bank angles.

My position was from the beginning and still is, that the initial climb in the recorded intensity and duration was unitentional due to lack of manual handling at altitude and in degraded law. That PF was more occupied by roll control than pitch control, the last one may be doing by feel like he was used to during landing phase in flare mode. His corrective action to the announced and acknowledged deviation from altitude and pitch targets was ineffective from the beginning, leading only to a little decrease of VS without correcting the main problem, the beginning trajectory through the propulsion ceiling and the lift ceiling. Selecting TOGA in honour of the stall warning 2 made those inadequate amounts of SS relaxing useless, increased the pitch even more and led to the final stall.

From that point on the crew was helpless, as they did not know what brought them into this situation, what that situation actually was and therefore denied them the insight, what actions would bring them out of this situation. Therefore the SS inputs in that phase after the stall are no pointer to the initial intent.

In this assumed unintentional sequence the mentioned points by CONFiture are more than valid.

Machinbird
26th Aug 2012, 23:27
Thankfully the other F-4 guy (Franzl) has more time to post than I do, but I'm in full agreement with his analysis.

Full nose up after the stall, was simply an attempt to stabilize the aircraft's pitch attitude by a pilot who didn't understand WTF was happening.

There is sufficient reason to attribute the initial nose up leading to the stall as coming from the roll instability leading to inadvertent nose up inputs and the tendency of the aircraft's pitch channel to mathematically integrate those inputs. (For those who did not take calculus, it means add them all together). When did the initial nose up occur? Answer: When PF was fighting the roll problem the hardest. Did he have time to formulate a strategy of setting a nose up attitude? I doubt it. His computing power had to be focused on the roll problem.

Why doesn't the aircraft stop trimming in Alt2 Law when approaching the stall like it does in Normal Law?

More than likely, the engineers couldn't figure out a reliable way to do it. With stall AOA a function of Mach and gross weight/configuration, they didn't know how to make the Mach correction without airspeed inputs. They really should re-examine this more closely.


You can likely make a fairly good Mach approximation from inertial data. With that data, altitude data, and a safety factor, they could stop the trim from running up to the limits.
By considering alternate sensors for determining a stall state, they could probably stop trim from running up despite what would seem to be reasonable AOA at lower altitudes. What happens to the airflow over a wing during a stall anyway? Don't you think we can make a sensor to detect that state? I do.

HazelNuts39
26th Aug 2012, 23:47
The normal feeling on the SS from day to day flying therefore is holding some backpressure to maintain the flightpath during landing or to rotate and climb during T/O. The necessity of ND SS input and the required amount of ND SS input in normal daily operation therefore differed grossly to that one needed to correct this unintentional climb. A tendency to pull rather than push, combined with a concern for overspeed, in direct law as in alternate law, that sums it up nicely.

jcjeant
27th Aug 2012, 00:16
RetiredF4
To answer that question we would have to come to a conclusion, what PF tried to achieve firsthand. Neither BEA nor our efforts here come to a final result.
The BEA report includes a exaggerated number of
Probably
Likely
If
Maybe
In the technical and human factors sections
It is rare to see a report containing so many conditional , uncertainties and inaccuracies while investigators have all the records (CVR-FDR) in perfect condition and many visual ( material - physical ) evidences
How aviation safety can be enhanced with the findings and recommendations originating from :
Probably
Likely
If
Maybe
That I do not know ...

gums
27th Aug 2012, 00:58
Good analysis Retired and 'bird.

Without a "brain recording" we shall never know why the pilot kept pulling back. And I don't agree with 'bird about roll PIO and such. May have been there, but not to any serious influence versus the constant back stick.

If there is one good thing about the 'bus and our primitive system in the Viper, it was that HAL would use every control surface available to achieve the trimmed gee ( ours could be trimmed, but the 'bus was one gee all the time, corrected for pitch attitude). So simply relaxing the stick pressure would let HAL do what he was supposed to, allowing you to figure out what the hell was going on.

Another poster provided an excellent discussion of AoA WRT mach and altitude and such. But I am personally here to tell you that our primitive system handled the problem really well. We never exceeded the AoA limits while hard maneuvering, and the only way we got into a true "deep stall" was to hold a high pitch attitude as our energy decayed faster than the control system could get the nose down. Sound familiar?

Gotta go. Dodging hurricane in Florida.

Addendum:

It still distrubs me to see some pilots here that don't seem to understand how their jet flies. The new jets, with all the augmentation and such, may appear to be real easy to fly. Then you look into all the control laws and such and see what HAL is doing.

What do you do when HAL gives up?

I can't find one commercial jet with FBW or basic/advanced augmentation that doesn't fly like we old dinosaurs were used to.

As several here have pointed out, the 'bus is a basic "direct law" until well up in the air or in the "flare" ( not sure what the flare mode does, but whatthehell).

Ours was "direct" until weight off wheels. Then it was blended AoA, pitch rate and gee command until gear was fully up. Worked for me, and thousands of fighter pilots that have flown the jet since 1973.

I have a lot more confidence as a SLF after reading some of the "war stories" here from the professional pilots than I had three years ago. But make no mistake! If I am on board and you are the PF/PIC/AC or whatever, I shall be back there analyzing every move you make, heh heh.

Organfreak
27th Aug 2012, 02:44
The Peanut Gallery heartily endorses the views of Misters F4 and Birds.

:D:D:D:D:D

EEG for all pilots? A horrible idea whose time may have come.

:E

rudderrudderrat
27th Aug 2012, 05:07
Hi Gums,
we shall never know why the pilot kept pulling back
I agree. He may have been attempting to out climb the CB in front of him - I have heard of other pilots who would attempt to fly over the top of a CB rather than through it despite being far to close to their ceiling.

Machinbird
27th Aug 2012, 05:29
I agree. He may have been attempting to out climb the CB in front of him - I have heard of other pilots who would attempt to fly over the top of a CB rather than through it despite being far to close to their ceiling.At Night? Wasn't the CB pretty much behind him and off to starboard by the time the pitots froze up? (assuming the 12 degree turn to port was reasonable).

TTex600
27th Aug 2012, 17:16
It still distrubs me to see some pilots here that don't seem to understand how their jet flies. The new jets, with all the augmentation and such, may appear to be real easy to fly. Then you look into all the control laws and such and see what HAL is doing.



It is virtually impossible to understand how an Airbus flies when all you have for training material is FCOM's - and when the first rule says an Airbus flies like any other airplane.

OK465
27th Aug 2012, 18:17
Re: A320

The only way my instructor could force Dir Law left us with no roll control spoilers, slow ailerons, and resulted in an extremely unresponsive airplane.

FYI TTex & CONF:

1. A330 with only one SEC FCC available (other FCC pb's off):

One pair of roll control spoilers (depends on which SEC) and one set of ailerons

(During full SS roll input, down going aileron only deflects about ½ way, the up going aileron goes full deflection.)


2. A330 in ALT2 roll direct as a result of triple ADR disagree (ALT2B?):

Two pair of roll control spoilers and one set of ailerons

(During full SS roll input, NEITHER aileron deflects as much as they do with only one SEC.)


It's no T-38, but 'responsiveness', it appears, is in the eye of the ‘respondee’.

Thank you guys for bringing this stuff up.

PJ2
27th Aug 2012, 18:28
Most here know that the idea behind any close examination of any accident, this one in particular, is learning and hopefully prevention. I think the conversation regarding important factors such as intention, willingness, capacity (of both airplane and pilot) are especially valuable contributions to an understanding of what happened and perhaps a bit about why.

Some comments regarding the sidestick, apropos franzl's and Machinbird's comments:

The THS is manually set prior to takeoff. On takeoff, the sidestick is held slightly ND until 100kts at which point it is neutralized. It is moved back to initiate rotation, usually about half-way or a little less, depending upon CG. Sometimes the rotation rate feels as though it requires checking-forward on the SS but the FCOM warns against this and one maintains sidestick position until the climb is established.

As described the takeoff is done in direct law with pitch normal law gradually blended in within 8 seconds of pitch > 8deg.

Once the initial climb pitch attitude is established, pressure on the stick is relaxed. In fact, speaking technically only, one can let go the stick and the airplane will remain in the last selected pitch and bank attitudes. Sometimes that is a reasonable way of avoiding stirring the pot, as the airplane doesn't need any input if it is at the intended attitudes. In other words, no back-pressure is required to sustain the takeoff pitch attitude.

One can fly a SID with small, "squeezed" stick inputs for roll and especially for pitch, (only because tiny changes are all that are required for speed control). Even in turbulence, that is all that is required, because in normal law, everybody out there on the wing is busy maintaining the last selected attitude and stirring the stick only adds to the busy-ness without much effect.

The airplane can be flown to cruise altitude and, again technically speaking if planned in RVSM airspace, in cruise in normal fashion. At high altitudes one is always gentle with any transport and not just "Airbus", due to reduced damping of the thinner air. (Many here know this already...I'm being thorough, not pedantic!)

The airplane can be flown in turbulence, even heavy turbulence, (moderate, not severe - which I have never experienced). One keeps inputs small to avoid stress but other than avoiding small (and I emphasize momentary), inputs due to turbulence the aircraft is as straightforward to fly as any I have flown.

Descent is still 1g flight of course and the airplane can be flown from ToD to landing, and I often did this for the A320, less so for the A340/A330 but only due to long-haul (fatigue) issues and STAR complexities. Again, no stick input is required in this phase.

On approach, the usual small movements to counter slight changes in pitch and bank are normal. To alleviate any impression that NU stick is somehow needed in the approach phase, there is no "back-stick" required until 50' when the AFS feeds in a slight ND bias to give the feel of a conventional flare. Pitch direct law is gradually fed in beginning at 100' while roll remains in flight (normal law) mode until the pitch is < 2.5deg.

In terms of a subtle bias towards "pull" vice "push" due to AFS laws in various flight phases, I have to observe that the required operation of the stick as described coupled with my own experience would not cause a bias either way. The control laws do not engender this sense that one must "pull" most of the time - the notion just doesn't apply.

Unless we know what was intended, I think the notion of "intention" has no "correct" application here in examining what occurred in the first 30 seconds after the UAS event. Clearly, we can intend something with all our being and still be wrong. "Intent" can be informed by knowledge, training and experience, or it may not be, yet one may fully "intend" an action based upon incorrect assumptions, mistaken understandings or shortcomings in knowledge or experience. To me, this is an important part of examining the crew interactions. Willingness to accept another's interventions in such circumstances will be based upon the strength of intent (one's interpretation of what is wrong), and not always (reliably) upon knowledge. CRM is designed to counter the natural unwillingness to let go of one's own assumptions to adopt, (perhaps initially on faith alone), another's interpretation of what is happening. We have all been in situations when we know damn well that we are right, until we aren't, and we may even surprise ourselves that it was possible to be wrong.

Applying a steady, not just a momentary NU control input to a transport aircraft at cruise altitude to a 10deg pitch attitude is counter to all intuition, training and knowledge yet there it is, applied to the point of stall. Why?

What was the basis of the individual intentions which initially overcame and subsequently replaced an understanding of a number of fundamental aeronautical principles such as energy management, high altitude flight, aircraft performance and operational principles of SOPs and CRM? What was more powerful than these?

Post-stall, there are contributions from the airplane which led, perhaps inevitably, to further confusion but in the first moments nothing from the airplane indicated that a sharp and then sustained pull-up was the correct solution to a particular flight problem.

The rapidity with which situational awareness was lost and not regained is also an important area of learning.

These are some of the thoughts that occurred as I read and re-read through HN39's, franzl's, gums', Machinbird's & CONF iture's contributions highlighting the challenges of understanding what really happened.

Lyman
27th Aug 2012, 20:07
As ever, I remain convinced this accident had its beginnings with loss of a/p. We think we know better, but we do not. We assume PF knew right away the conditions, I suggest neither did. A/P loss due turbulence happens, and the 330 will remain in Normal Law. This would explain his cavalier attitude with Pitch, and focus on a newly twitchy roll axis.

We need to be careful about assuming things that have no direct evidence to support, and cognizant of possibilities that do not rest on a fundamental understanding of the recorded events. They had nil access whatsoever to records, none. They had their senses, we think, and what is left can be explained by any combination of cues and data that can be imagined.... It is common here, for some to base a condemnation of the crew on a single fact, and then assume truth by asking "Why"? I submit that is absurd... It is possible PF assumed NL until PNF announced Alternate Law. That is sixteen seconds of NU. NU that may have resulted from an erroneous, though forgivable, assumption of his, which thoroughly would explain his "negligent" back stick...

RetiredF4
27th Aug 2012, 20:15
Thank you for your contribution, PJ2.

You explain the handling of the SS ion the different phases of the flight, and i have no reason to think otherwise. But do we know, what the procedure for hand flying the A330 on long haul flights is with AF and how much practice in the real aircraft that left outside the T/O and landing regime? When do they take over in the landing phase? When established on final no input is needed until flare mode activates, correct? As you describe and as i understand the NZ law, no stick input is required if no change of flight path is intended. Can we talk about flying manual in this case?

Imho no, it is changing flightpath manual instead of pushing buttons or turning knobs, but that´s it. Bank angle compensation acounts for no need to make any pitch adjustment when turning and autothrottle takes care of the energy management . The FBW concept as implemented here reduces the necessity for pilot input to one single axis operation concept. There is no necessity to manage all three axis of the aircraft and the energy at the same time with elevators, ailerons, rudder and throttles at the same time, meaning with manual inputs trained in years of expierience. It´s reduced to "point and let go, the system will take care of the rest ". Wether you do it with SS , a yoke or the knop on the dash board is no longer important. It´s a nobrainer.

When AF447 dumped AP, ATHR, normal law and protections together with the speed indication in the blink of a second, the PF was forced to use strategies he was no longer trained for. No system was taking care of roll when he concentrated on pitch, no autothrust was taking care of the energy management, and no bank angle protection available to stabilize the pitch during roll.

Let´s look at a different thing, which keeps me thinking about:

The aircraft responds to a sidestick order with a pitch rate at low speed and a flight path rate or “g” at high speed. When no input is made on the sidestick, the computers maintain a 1g flight path.

We know, that the aircraft maintains stick free 1g, and that SS commands a change of g blended with pitch rate starting below 210 knots. In a newspaper article from the early A320 flights i remeber, that the ratio is 50/50 at 150 Knots. The speed responsible used for this changeover was faulty, down to 60 knots which would equal nearly a pure pitch rate change. But the aircraft was traveling still at over 230 knots in the regime where only g command should be present. I could not find any reference from where we could draw a conclusion, wether this different SS command would have influenced the outcome of any SS order. There is reason, that this changeover takes place in the low speed regime, what influence does it create wehen this changeover is taking place when the airframe is still above the change over regime in degraded mode?

The assumption, that the PF initiated and sustained that climb intentionally disregarding all basic principles of flight, busting assigned FL, disregarding CRM and not anouncing his intentions neither to the PNF nor later to the captain explains all following events. It´s an easy solution (just change the pilot everything else is fine), but it´s based on thin or even no evidence.

PJ2
27th Aug 2012, 22:11
Hi franzl;

Thoughtful response, thank you. The points are eminently worth discussing, and for the time being concluding who's theory is right is less important than the discussion!

When established on final no input is needed until flare mode activates, correct? As you describe and as i understand the NZ law, no stick input is required if no change of flight path is intended. Can we talk about flying manual in this case? By all means, and what you say in your next paragraph, (. . . "It's a no-brainer"), is in my view largely though not exclusively true for the present standard of training and expectations, a clear risk which is now being widely discussed, examined in the many conference topics since AF447 and how has the attention of at least the US and European regulators, (in fact AW&ST provided articles in August, 1989 and January/February 1995 discussing these aspects in automation development).
When AF447 dumped AP, ATHR, normal law and protections together with the speed indication in the blink of a second, the PF was forced to use strategies he was no longer trained for. No system was taking care of roll when he concentrated on pitch, no autothrust was taking care of the energy management, and no bank angle protection available to stabilize the pitch during roll.
I think your comment may be accurate in this case and this case may, among a couple of others, be a harbinger of such a developing trend. However, the Air Caraibe event and thirty-odd others which occurred prior to and also after AF447 do represent counter-examples to the "no longer trained for" point because to a greater or lesser degree, these were successfully completed flights. I don't believe such circumstances would leave the majority of crews in a situation they were no longer trained for, at least, quite frankly, I hope not because this wasn't in and of itself and all else being equal, (I recall, and take your interesting point regarding the pitch/flight path item), a serious emergency, (as in loss of pressurization, hydraulics, electrical power generation, engine thrust or engine disintegration, etc). If we consult JACDEC or Aviation Herald we can read about a number of incidents, events and near-accidents in which crews addressed them as trained and which did not result in loss of control or loss of the aircraft.
It´s an easy solution (just change the pilot everything else is fine), but it´s based on thin or even no evidence. The evidence is in the absences of an expected standard initial response to an abnormality, which, I will add, is a point which thus far has yet to be discussed and countered.

To my knowledge and experience as an airline pilot there are no circumstances, save for perhaps extremely rare and dire events, in which SOPs, CRM and discipline take a back seat. These responses are proven, primary responses, heavily-emphasized and trained in airline operations and to deviate from them requires significant operational factors.

No such factors or events prior to the stall warning are in evidence. If the airplane pitches up due to some anomaly, one tries to get it back down to stable flight, period, yet the inputs are mostly NU; one does not permit the airplane to do what it will, not, at least, without vigourously trying to counter what it is doing. If one doesn't counter the anomaly, the evidence is that one agrees with what the airplane is doing and it should "do more". So no, this is not an "easy solution" which dismisses this crew out of hand. This is an extremely difficult solution to come to terms with because it is human factors-based and one must be very careful to examine such factors while avoiding the narrow focus of "blame". Finding out "why", despite some commentary to the contrary, is the way to prevent this kind of accident. If there are training and standards issues, that needs to be examined as do priorities in terms of autoflight and manual flying it is to be discovered first through this unfortunately-blunt process.

BOAC
27th Aug 2012, 22:29
Finding out "why", despite some commentary to the contrary, is the way to prevent this kind of accident. If there are training and standards issues, that needs to be examined as do priorities in terms of autoflight and manual flying it is to be discovered first through this unfortunately-blunt process. - and I would dearly like to know why, but as I said months ago, I fear we are 'dancing on the head of a pin' here since the reaction of this crew was so out of the ordinary as to render, in my opinion, any logical approach to this accident of no value, except in re-focussing at least AF's attitude to basic flying skills in their crews and some vital changes to AB software and philosophy.

That not-with-standing, the dissection of the FBW system has been of great interest and my hearty thanks to all who have taken the trouble to expound.

HazelNuts39
27th Aug 2012, 22:33
We know, that the aircraft maintains stick free 1g, and that SS commands a change of g blended with pitch rate starting below 210 knots. In a newspaper article from the early A320 flights i remeber, that the ratio is 50/50 at 150 Knots. The speed responsible used for this changeover was faulty, down to 60 knots which would equal nearly a pure pitch rate change. But the aircraft was traveling still at over 230 knots in the regime where only g command should be present. I could not find any reference from where we could draw a conclusion, wether this different SS command would have influenced the outcome of any SS order. There is reason, that this changeover takes place in the low speed regime, what influence does it create wehen this changeover is taking place when the airframe is still above the change over regime in degraded mode?

Perhaps the final report answers your question, at least part of it? At any rate, the response of the FCS and the airplane to longitudinal sidestick commands is recorded in the traces of elevator/THS and pitch attitude.

2.2.5 Aeroplane behaviour in reconfiguration laws
(...)
In alternate 2 law, the longitudinal control law remains a load factor law and the lateral control law is a direct law. 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 hardly modifies the behaviour of the aeroplane in comparison to normal law, but can nevertheless induce an unusual response dynamic when the aeroplane has an abnormally low speed for the configuration.

bubbers44
27th Aug 2012, 22:47
Safely at FL350 maintaining attitude would have saved them. They did the low level terrain profile of 15 degrees nose up and toga power. You can't do that at FL350. They screwed up and I think everybody knows it. They were both autopilot monitors, not hands on pilots.

Lyman
27th Aug 2012, 23:22
HazelNuts39

"In alternate 2 law, the longitudinal control law remains a load factor law and the lateral control law is a direct law. 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 hardly modifies the behaviour of the aeroplane in comparison to normal law, but can nevertheless induce an unusual response dynamic when the aeroplane has an abnormally low speed for the configuration."

You have said before you believed the "unusual response" might be sluggishness. As an aside, could it be the reverse? Could the Pitch rate be extremely high, if the coefficients are computed for Indicated speed, when it is erroneous? Would that not impart an emphatically increased authority to the elevators, relative to pilots inputs? Especially if the actual velocity was .80 Mach?

If the responses were sluggish, would that not possibly explain PF's dogged pursuit of some G? Might he have been seeking the twitchiness in Pitch that he found in Roll? If he thought the aircraft was unresponsive in Pitch, would he not command as much as he could get? If he sussed sluggish, and got no immediate "response" would he be tempted to trade rate for continuation of input?

He could not have seen AoA, and he would be using the horizon as his guide, which although high, did not jive with his sensation of load? Much of the g post 1.65 and the reduction to 1200 fpm from 7000fpm was less than one, was he flying knowing that his Pitch was high, but negating it to some extent because he did not truly believe the Pitch jived with the loading? Nose high and descending without a Stall Warning would communicate that one of them was wrong. Especially without Airspeed.

Did he choose to follow the wrong cue? The lack of gee over the horizon?

gums
27th Aug 2012, 23:59
Hey, Lyman! The coefficients are most likely the "gains", as we FBW pukes call them.

The basic gains are mostly for determining the amount of control surface movement and the rates they move. They are also modified according to configutation, so gear down they will be generally lower in movement or rate, but it depends on the jet. In the Viper, the movement was higher, but the rate was lower.

When our pitot-static system went FUBAR we went to "Standby Gains", which were about 140 -160 knots gear down and 300+ knots CAS gear up!! Surprisingly, almost the same as the 'bus on the high end. Hmmmmm.... Remember that we still had the gee and rate limits, but it still worked well, and we were used to high gee maneuvering.

Bottomline is that the 'bus gains actually provide a kinder, gentler handling when in the back-up mode. Not skittish or overly sensitive.

My personal beef is the lack of AoA inputs beyond the warnings. I could live with basic AoA limits ( "protections") throught the envelop unless in "direct", and then clear warning indications that I was gonna stall the sucker.

Alber Ratman
28th Aug 2012, 00:16
Thread... Please DIE!:E

Lyman
28th Aug 2012, 00:19
Hi gums....

You say.... "Bottomline is that the 'bus gains actually provide a kinder, gentler handling when in the back-up mode. Not skittish or overly sensitive."

I think it is possible our PF noticed the above in Pitch, and when he determined his inputs could not effect rate, as in Roll direct, he traded rate for "holding" aft stick, (persistence). It would be the first time he experienced different "Law" in two axes. In selecting Roll as his preferred (Direct), he may have decided his efforts would have more effect in Pitch if held. A mistake, surely, but he had no experience flying by seeking g, another first time only time. Til then, the aircraft had always done it.

Bear in mind, most everything that happened after a/p loss was a first time event in the aircraft, along with a deluge of alerts. He appeared terrified of G<1.

His training had been nothing like yours, not his fault. I don't think it is equitable to slam him for trying what he thought would work. Not that you are, I think you get what he was up against. The sobering thought is that he was one of thousands who might have the same responses to unexpected gremlins.

Respect,

john_tullamarine
28th Aug 2012, 01:42
The sobering thought is that he was one of thousands who might have the same responses to unexpected gremlins.

.. and that's why this series of threads is so important ... sorry, Alber Ratman

bubbers44
28th Aug 2012, 02:12
We must always remember how to fly by attitude and thrust, no matter how automatic the airplane is. If we don't we are not really pilots. We are programmers of autopilots. Don't let it happen to you.

gums
28th Aug 2012, 02:35
Nice concept, Bubs.

Although my IP had explained a lot about AoA and lift and such, on my first flights he taught me to use pitch attitude looking at parts of the canopy rails and such. Hold an attitude at a power setting and watch airspeed. Slowing down? Lower the nose a bit, and vice versa.

There are few planes in the commercial arena that will suffer catastrophic failure if you simply "hold what ya got" if you have any warnings except terrain collision. Sure, complete loss of power such as Sully had requires keeping airspeed for maneuvering and such by lowering the nose. But even my LEF emergency only required that I keep doing what I was already doing ( lots of sidestick pressure to keep roll under control and yaw trim would come later).

Another pilot here has already commented that the nifty flight director bars helped to get on course or intercept the ILS or...... But I can tell you that when I got my interceptor assignment outta pilot training that the Air Defense Command liked those of us that had flown the old T-33. No fancy ADI or steering or such when on instruments. "Primitive" would be a good description. So they let us fly target missions and such after only a single checkride. The T-38 troops had to wait until they were at their permanent assignments.

First jet I flew with the steering bars was the SLUF, and it was very "loose". Most of us did better using the raw data, heh heh. Years later I got to the Viper and no steering, just raw data( see my video of the LEF landing approach). Hmmmm.....

Somewhere in the aftermath of this tragedy, the powers that be must take a deep breath and implement better training. Ya think?

CONF iture
28th Aug 2012, 03:33
2. A330 in ALT2 roll direct as a result of triple ADR disagree (ALT2B?):
Two pair of roll control spoilers and one set of ailerons
(During full SS roll input, NEITHER aileron deflects as much as they do with only one SEC.)
This seems to match with the FDR data where only INB Ailerons were solicited at a max deflection of 16 degrees out of 25, and spoilers 4 and 5.

After PRIM and SEC1 were turned OFF, only spoilers 4 remained active. I suppose the zipper shape for spoilers 5 and 6 show their inactivity related to PRIM and SEC1 status.

Another hit at the BEA :
Why no further comment on the PRIM and SEC1 episode, especially in regards to the human factor analysis ?
IMO, this one clearly indicates that the crew (or at least the PNF) lost faith in the aircraft, and probably thought they were facing a computer bogus, or a protection takeover.

Lyman
28th Aug 2012, 04:38
CONFiture,

Can you expand on that? Switching off the PRIM came up right away, did it have to do with trying to get the bird?

"We have tried everything"...

I have sensed the presence of workarounds in this cockpit, how are you meaning "lost faith in the a/c"? How does the suspicion of Prot take over fit in?

BEA have left all out but the rudiments, what are they doing? Do you consider the zipper to be generic, or specific to each instrument, mode or system?

nikplane
28th Aug 2012, 12:02
Hi all.


AF 447.

In this terrible disaster of flight, if you allow I would want to remember to you the following points:


1) the strong vertical movements of the air inside the cumulinembo CB.

2) with pitot-tube clogged (iced) the airspeed instrument then acts like an altimeter.


What do you think?

From 4 Aug 2011 I read and reread-reread all your messages about A330 disaster.

HazelNuts39
28th Aug 2012, 12:59
From 4 Aug 2011 I read and reread-reread all your messages about A330 disaster.Have you read the BEA report?

nikplane
28th Aug 2012, 14:05
HazelNuts39

The final report Bea, I’ve printed 224 pages, with my printer, I did not deliberately read yet. But, I’ve read the other Af447 Bea report.

HazelNuts39
28th Aug 2012, 14:50
nikplane,

if you've read the 3rd interim report, you should know that the pitot-tubes did not act like an altimeter. The final report has a figure 64 that shows the vertical and horizontal movements of the air.

CONF iture
28th Aug 2012, 15:48
Can you expand on that? Switching off the PRIM came up right away, did it have to do with trying to get the bird?
Switching off 2 FCCs came pretty late, they were trough 10000 feet already.
But "on comprend rien on a tout tenté" came much earlier, close to 2 minutes earlier, in fact it was part of the briefing that the PNF gave to the captain at his return.

I have sensed the presence of workarounds in this cockpit, how are you meaning "lost faith in the a/c"? How does the suspicion of Prot take over fit in?
There is some history on that especially at AF which was one very early operator and at great scale of the new protected FBW technology.
Came Habsheim (I don’t want to discuss it here) but with Habsheim came already suspicions of computer interference. Then came in France the air inter accident where again the investigation was lacking of transparency, FDR was labeled as destroyed … QAR data were not extensively published, and multiple time references were used indicating partial 'loss' of CVR data.

Also the FCOM has this interesting note :

http://i35.servimg.com/u/f35/11/75/17/84/med_tc10.png (http://www.servimg.com/image_preview.php?i=154&u=11751784)

Did it happen already at AF on the early days of the 340 … I’m not sure but I’ve heard something in that direction where the only way to get rid of unwanted protections was to force direct law by switching some FCC off.
Was it unofficially briefed at AF during sim training ... ?

jcjeant
28th Aug 2012, 17:03
QAR data were not extensively published, and multiple time references were used indicating partial 'loss' of CVR dataConcerning the AF447 and BEA final report .. it's unfortunate (a shame ?) that the complete FDR LISTING is not public

AlphaZuluRomeo
28th Aug 2012, 18:24
CONF iture: In the said case (re: your #164), switching off one of the two consistent-but-wrong ADRs would be enough?

CONF iture
29th Aug 2012, 00:57
In the said case (re: your #164), switching off one of the two consistent-but-wrong ADRs would be enough?
Turning one of those ADR off could be one way to deactivate the protections, but turning all FCC but one off would be a radical way to switch to direct law and deactivate the protections as the same time.

Such initiative to switch 2 FCC off without any ECAM command did not come out of the blue. I am questioning the BEA how they did not investigate this episode to find out what may be hiding behind …

This action also shows IMO there was not any panic on board as many like us to believe.

bubbers44
29th Aug 2012, 01:44
Pitching up to 15 degrees at FL350 indicates panic to me. No airliner can do that without stalling.

Owain Glyndwr
29th Aug 2012, 08:57
We know, that the aircraft maintains stick free 1g, and that SS commands a change of g blended with pitch rate starting below 210 knots. In a newspaper article from the early A320 flights i remeber, that the ratio is 50/50 at 150 Knots. The speed responsible used for this changeover was faulty, down to 60 knots which would equal nearly a pure pitch rate change. But the aircraft was traveling still at over 230 knots in the regime where only g command should be present. I could not find any reference from where we could draw a conclusion, wether this different SS command would have influenced the outcome of any SS order. There is reason, that this changeover takes place in the low speed regime, what influence does it create wehen this changeover is taking place when the airframe is still above the change over regime in degraded mode?

As I understand the system it doesn't work quite like this. The BEA report says:

In alternate 2 law, the longitudinal control law remains a load factor law and the lateral control law is a direct law. 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 hardly modifies the behaviour of the aeroplane in comparison to normal law, but can nevertheless induce an unusual response dynamic when the aeroplane has an abnormally low speed for the configuration.

From all the diagrams I have seen describing how C* works the pitch rate/g mix is a feedback term. S/S movement always commands a load factor as the steady state output just as the BEA report says. What the pitch rate/g term does is change the shape of the transient response between initial stick movement and achievement of the final desired 'g'. The origins lie way back in aircraft handling research when observers noticed that pilots tended to base their opinions on what constituted 'good' behaviour on how the pitch rate transient varied at low speeds and how the 'g' transient varied at high speed. Then somebody thought if that is what they rate as good why can't we give it to them?

So when in Alt 2B the system gains default to their 330 kt (Vmo) values the effect would be that the system would be trying to achieve the 'ideal' transient response (remembering that the Airbus intent was to make the pitch response the same at all speeds) using high speed 'g' base gains but at much lower speeds. This is what I think BEA are getting at when they say the aircraft has an unusual response dynamic in this situation.

Since the transient 'g' response to elevator movement would be much crisper at high speed I think this would lead the system to apply less elevator (to drive the pitch acceleration) than it would normally use at these low speeds, so the aircraft response would be more sluggish.

Anyway, that is how I see it working :8

RetiredF4
29th Aug 2012, 13:05
@<hidden> Glyndwr

From all the diagrams I have seen describing how C* works the pitch rate/g mix is a feedback term. S/S movement always commands a load factor as the steady state output just as the BEA report says. What the pitch rate/g term does is change the shape of the transient response between initial stick movement and achievement of the final desired 'g'. The origins lie way back in aircraft handling research when observers noticed that pilots tended to base their opinions on what constituted 'good' behaviour on how the pitch rate transient varied at low speeds and how the 'g' transient varied at high speed. Then somebody thought if that is what they rate as good why can't we give it to them?

Thank you for this input, there was an argument about this some posts back and thankfully we have straightened that one out. Your explanation is sound and easy to understand ( sorry that i couldn´t explain it that way), and now the result of using those fixed high speed gains gets clearer. This sluggish behaviour in pitch would be a new expierience to PF, especiually when the roll channel behaved quite differently (more agile).

Interesting would be, at what point those default values come into action. Is it the point where the speeds are lost or is there some time-delay / internal checking before this changeover takes place? And is this changeover sudden or gradual? Could the initial NU input be under the false speeds ( agressive) and the later correcting attempts under the default gains (sluggish)? When would the default gains be replaced again by the actual speeds?

AlphaZuluRomeo
29th Aug 2012, 13:31
Turning one of those ADR off could be one way to deactivate the protections, but turning all FCC but one off would be a radical way to switch to direct law and deactivate the protections as the same time.
Sure, and I understand you would prefer that (IIRC you are +/- advocating the Alt laws are useless, if not dangerous).
My point was: it's not the only way.

Such initiative to switch 2 FCC off without any ECAM command did not come out of the blue. I am questioning the BEA how they did not investigate this episode to find out what may be hiding behind …
Perhaps the BEA didn't investigate enough. Or perhaps they hadn't found anything consistant to write about it.
In intermediate report 2, the BEA wasn't sure if the PRIM1 and SEC1 were commanded off (by the crew) or faulted off (by the "system"). Ref IR2 §1.16.2.4.1.
With the benefit of the CVR transcript, one can conclude that PRIM1 & SEC1 were commanded off:

2 h 13 min 28,2
PNF : essaye de trouver ce que tu peux faire avec tes commandes là-haut (my note: the PRIM/SEC commands are on the overhead panel)
2 h 13 min 30,4
PNF : les primaires et cetera (my note: "primaires etc." may refer to the PRIMary and other computers)
CPT : (* fera rien)
2 h 13 min 31,5
CPT : on (fera /verra) rien

And then:
2 h 13 min 45 F/CTL PRIM 1 FAULT
2 h 13 min 51 F/CTL SEC 1 FAULT


This action also shows IMO there was not any panic on board as many like us to believe.
I disagree. The transcript show the PNF to want to "try" something with the "primary" (computers?) then the captain answering it will be no use, then the PRIM1 & SEC1 to be switched OFF.
This crew did enough "strange" actions for me to believe they were following a really logical path. It seems to be a case of "what about trying that?" (even with no clue/agreement) meaning: they didn't understand, they tried this or that, because they didn't realised the root cause of their incapability to control the aircraft (i.e. the stalled condition).

Lonewolf_50
29th Aug 2012, 14:13
Owain: thank you, a light went on as you described the gains and input relationships, and responses.

Retired F4:
This sluggish behaviour in pitch would be a new expierience to PF, especiually when the roll channel behaved quite differently (more agile).

Some years ago, I experienced a somewhat disorienting moment in the cockpit when the SAS and trim in the lateral channel went awry while the pitch channel remained just fine. We disabled AFCS and flew AFCS and SAS off (which required a gentle touch ... but is also something we used to practice!) once we figured out what was wrong. It "felt" wrong to say the least at onset.

I suspect that PF in AF447 encountered a similar "wrong" feeling, if the graphs depicting his efforts in the roll control are any indication.

OK465
29th Aug 2012, 15:23
This hardly modifies the behaviour of the aeroplane in comparison to normal law, but can nevertheless induce an unusual response dynamic when the aeroplane has an abnormally low speed for the configuration.

"What we have here is...(a) failure to communicate." :(

Lyman
29th Aug 2012, 15:40
One would want to check the trace record of elevators position at Law change with PF's first inputs in Pitch. With very low indicated airspeed wouldn't the response of elevators via FCC be extreme? relative to .82Mach? The aircraft exhibited a brisk increase in VS just at handover. Also just prior to the First Stall Warn, the PNF says: "What was that?". Could that have been a sudden reaction of the a/c to inappropriate "response"? Here, as in other areas, the CVR would be helpful, but is not published. The explanation for the comment was offered that PNF was noticing the SW, certainly, but it is not proven.

"Unusual Response-sluggish" Or "Unusual Response-Sudden"

BEA could clear this up with a memo, rather than relying on someone's best guess?

One does not expect a Stall Warn from a pull on the stick that is modulated through a computer to correct for load? Sluggish? NOT

Can this be related to Airbus OEB not to reselect A/P they released after 447?

Were they fearful the ap would "Climb Uncommanded?" with low speed inputs in this control law? Alternate Law2B? why wouldn't the ap be locked out by the system when UAS obtains? Not to mention Flight Directors....

Lyman
29th Aug 2012, 16:05
lyman #151

re: "HazelNuts39" and "sluggish"
"If the responses were sluggish, would that not possibly explain PF's dogged pursuit of some G? Might he have been seeking the twitchiness in Pitch that he found in Roll? If he thought the aircraft was unresponsive in Pitch, would he not command as much as he could get? If he sussed sluggish, and got no immediate "response" would he be tempted to trade rate for continuation of input?"

i consider this comment pertinent to Pilot's possible reactions derived from known or unpublished evidence. iow Human Factors...

"Pilot continued his NU commands, and the aircraft 'started to climb...' " from BEA, IR3....

OK465
29th Aug 2012, 16:23
HN39 & OG may be entirely correct here.

However, from my experience, the 'usual' response of aircraft at abnormally low speeds for the configuration IS sluggishness.

Unusual would be 'responsive' to a higher degree, much like 'stick force lightening' in some aircraft. :confused:

Lyman
29th Aug 2012, 17:45
OK465

"OK465 "HN39 & OG may be entirely correct here."

"However, from my experience, the 'usual' response of aircraft at abnormally low speeds for the configuration IS sluggishness.

Unusual would be 'responsive' to a higher degree, much like 'stick force lightening' in some aircraft."



447 was not at abnormally low speed. She was moving right along. Her indicated airspeed was erroneously low.

So it would not be unusual for her to respond with a too-far excursion of elevator If at high speed but the computer sensed low? Something is behind Airbus' concern for uncommanded climb.

Again, this should have been addressed by BEA...

Owain Glyndwr
29th Aug 2012, 17:46
@<hidden> F4

This sluggish behaviour in pitch would be a new expierience to PF, especiually when the roll channel behaved quite differently (more agile).

I'm entirely with you regarding the relative changes in lateral and pitch control, although I believe the change from S/S demanding roll acceleration instead of roll rate to have been the important factor. But pilots who have tried it say that although the aircraft is more sensitive in roll it is by no means difficult - just like a non-FBW aircraft in fact, and the fact that the AF447 pilot got it sussed in 30 seconds or so seems to confirm that.

'Sluggishness' in pitch is a relative term and it it always difficult to find words that give the desired impression. Based on experience with other large aircraft I was thinking of numbers like these for cruise conditions (the times are approximate indications only)

For a demand of Xg
Normal: after 2 seconds Xg; 4 seconds 1.2Xg; 6 seconds and onwards Xg
Sluggish: after 2 seconds 0.7~0.8Xg; 4 seconds 0.9Xg; 6 seconds and onwards Xg

In other words the initial response would be less rapid but achieving the final desired 'g' not appreciably different.

Interesting would be, at what point those default values come into action. Is it the point where the speeds are lost or is there some time-delay / internal checking before this changeover takes place? And is this changeover sudden or gradual? Could the initial NU input be under the false speeds ( agressive) and the later correcting attempts under the default gains (sluggish)? When would the default gains be replaced again by the actual speeds?

I don't know of course, but I would think the default gains kicked in at once when the internal checking logic said go to Alt2B. That would place the whole sequence with the default gains. I can't see any change to these gains unless and until Alt2B got replaced by some other law - which didn't happen.

CONF iture
30th Aug 2012, 04:04
Sure, and I understand you would prefer that (IIRC you are +/- advocating the Alt laws are useless, if not dangerous).
Where did I mean 'dangerous' – Any quote ?
Alternate law on the pitch but direct on the roll brings confusion.
Yes, direct law all the way, that crew would have been better served for all the reasons mentioned earlier (http://www.pprune.org/7378242-post109.html).

then the captain answering it will be no use
The BEA did not positively report as such.

I disagree. The transcript show the PNF to want to "try" something with the "primary" (computers?) then the captain answering it will be no use, then the PRIM1 & SEC1 to be switched OFF.
This crew did enough "strange" actions for me to believe they were following a really logical path. It seems to be a case of "what about trying that?" (even with no clue/agreement) meaning: they didn't understand, they tried this or that, because they didn't realised the root cause of their incapability to control the aircraft (i.e. the stalled condition).
Asking questions and trying something is not my definition of panic.

gums
30th Aug 2012, 05:27
Thank you, OG. A great explanation of some fine points of the control laws.

As a matter of credibility, I was one of the pilots 33 years ago that talked with the engineers and flew the simulators that had different control laws and such. In our primitive system, we had a very clear "warning" that we were in "standby gains". If we were at 400 or 500 knots CAS, then the thing was sensitive! Once below 350 knots or so, the gains felt good.

Most of us would have liked a blend of AoA and gee command, with pitch rates to prevent overshoots. But the AoA sensors were less reliable if our speed got too slow. Nevertheless, above 120 knots CAS or so there was no problem.

In normal gains, we only saw a significant dampening of pitch rates when AoA was approaching the max limit. At low AoA we could get unbelieveable rates until we got to 20 degrees or so of AoA, regardless of the gee command. The so-called "bat turn" at 9 gees. Remember that we could maintain 25 degrees per second of sustained turn rate. The "corner" was at about 360 knots CAS, with 9 gees available and AoA of about 15 degrees.

Again, than you OG for a great explanation of the gains.

AlphaZuluRomeo
30th Aug 2012, 09:12
Where did I mean 'dangerous' – Any quote ?
Alternate law on the pitch but direct on the roll brings confusion.
Yes, direct law all the way, that crew would have been better served for all the reasons mentioned earlier (http://www.pprune.org/7378242-post109.html).
Hang on, I never said it was a strict quote (hence my use of the "+/-"), but my understanding of your PoV (which I understand & respect). Something that bring confusion is dangerous in a cockpit.
I may differ of your PoV in a broader picture:
- I'm not sure Alt laws bring that much confusion
- I'm not sure Direct law is always the best fail mode (in AF447, it may have been, as you very well demonstrated; but this is one accident, what about other events/situations?)

The BEA did not positively report as such.
I don't know if you read french? I do, and that's simply my reading of the CVR transcript around 2 h 13 min 30.

Asking questions and trying something is not my definition of panic.
You said "IMO there was not any panic on board".
I agree that no mention of "shouts" or breakdowns are on the CVR. I agree that the crew tried until the last second to do its job.
The fact that they "tried everything", without much logic, without agreement between crew members, with the serious concern of altitude passing FL100, with the PF & PNF "fighting" for the controls, with rambling, chopped talks... is IMO symptomatic of at last some kind of panicked state. Or should I say deeply concerned?

CONF iture
30th Aug 2012, 13:40
I'm not sure Direct law is always the best fail mode
The laws and protections on the Airbus are very much dependant on the reliability of the numerous probes and sensors. Airbus has opted to keep as much as automation as possible depending of the circumstances. My proposition would be different : As soon there is a doubt on any data, first advise, second degrade to the basic.
That way, any Airbus simulator training would invariably lead to direct law with manual trim in case of manual flight and the crews would be used to that known and unambiguous state.

In Perpignan, the only reliable AoA data was silently discarded by the system, the crew proceeded with the test at an unreasonable low altitude, but knowing what we know now on AF447, nothing positively indicates that the test would have ended differently if the crew had tested at the minimum recommended altitude …

The simple and logic thing would have been to merely advise the crew of the loss of certainty regarding the data : AOA DISCREPANCY
My bet is that the crew would not have proceeded with the test at all as the test was specifically based on the accuracy of the AoA readings.
And why not reverse to direct law with still the capability for the AP ?
Many airliners fly around that way, is it a problem ?

Lets keep the magic of the Airbus when everything is known at 100% not lower.

CONF iture
30th Aug 2012, 13:49
I don't know if you read french? I do, and that's simply my reading of the CVR transcript around 2 h 13 min 30.
The BEA transcript is not :
Ça ne servira à rien

The BEA transcript is :
(* fera rien)
on (fera /verra) rien

with the BEA notes :
( ) Words or group of words whose meaning has not been identified with certainty. The “ / “ symbol gives various proposals.
(*) Words or groups of words not understood

Lonewolf_50
30th Aug 2012, 13:55
Conf, I am not sure I agree with you on the all or nothing point you are making.

Let me compare what Airbus does with the cascading control laws when various inputs go wrong to what Sikorsky does with the levels of flight control automation for a Seahawk helicopter. (Note: Not FBW in a general sense).

When all of the buttons are green, you have AFCS which includes the trim, SAS and boost features. You can disable AFCS (which allows for a variety of "hold" autopilot features, like altitude hold, airspeed hold, heading hold, etcetera) and keep the SAS, boost, and trim. You can also slowly but surely disable or lose those servos and their features as well, and end up with a "boost off" flying mode. This is a challenging but flyable mode. You are your own SAS system, and your touch on the stick (cyclic) has to be very light, even though your feet (rudders) and left hand are working very hard. (Aside: "boost off" is a slight misnomer in the Seahawk, since there is hydraulic power still driving the gross inputs into the rotor system). The inputs into the flight controls that feed the rotor system controls have a boost piston that can be diabled if there are problems.

Given a choice, I would prefer not to go from "all systems on" to "boost off" in instrument condiditions where a chance of keeping a few features, depending upon failure mode, could be worked in.

Granted, not the same kind of aircraft.

AlphaZuluRomeo
30th Aug 2012, 15:15
My proposition would be different : As soon there is a doubt on any data, first advise, second degrade to the basic.
I totally agree with the first item. :ok: This one is lacking (or at last was on june 1st, 2009). :=
For the second one, I still am not sure (I insist: I'm not saying "alt law is good", nor "alt law should be discarted"). There are pro and cons (e.g.: Lonewolf_50's answer). There are different situations/failures/combinaisons of those.
While I understand your reserves (in AF447's scenario), Airbus people chose to make an Alt law, they are better informed than I'm. Why is interesting. But I, as an outsider, prefer to restrain from an all-or-nothing position.
In french: Il ne faut pas jeter le bébé avec l'eau du bain.


The BEA transcript is not : (...)
Yes, I'm aware of that. Once again, that's simply my reading (my understanding/guess) of the meaning of the captain's words.
Do you have another (better?) explanation of the meaning of those words? As for myself, I see no other possible meaning of these words. It's not (and cannot be) a proven fact, as he's no more here to explain us what he meant.

OK465
30th Aug 2012, 20:02
I think this would lead the system to apply less elevator (to drive the pitch acceleration) than it would normally use at these low speeds,

Agreed.

In other words the initial response would be less rapid but achieving the final desired 'g' not appreciably different.

This doesn't sound right (bolding), but I may not understand what you're getting at.

Amount of elevator deflection for a given SS longitudinal input is essentially the same for 330K in Normal Law, 330K in ALT2(B), and, for example, 200K in ALT2(B), an abnormally low speed for the clean configuration.

At 200K in Normal Law, elevator deflection for the above same SS input is about twice that of the ALT2 deflection.


As a result, I would think you would not ultimately achieve the same peak G value in ALT2 as in Normal, ALT2 value would continuously be lower over the period of the input and never catch up. Holding a less deflected elevator longer isn't going to eventually increase G....and the aircraft response difference would simply be one of the further reduced pitch rate for that speed. Longer time for a given FPA change, which is what a pilot would sense even though the SS 'spring' feel might be associated with different expectations.

My point is couldn't that paragraph in the report just refer to this directly? In the sense that the aircraft is even 'more sluggish' than 'normal sluggishness' at these speeds, I guess truly that is an 'unusual' response dynamic. But given that one is not normally at these speeds clean anyway, I would imagine a pilot assessment of 'unusual' behavior would be a bit superfluous. :}

gums
30th Aug 2012, 22:23
Good point Okie.

The thing about a smaller and less rapid rate of elevator when on the backup gains is that HAL will keep trying to achieve the commanded gee. So after a minute of back stick, the THS starts trying to help, and as the smash runs out both elevator and THS keep moving to get to the gee command.

We dinosaurs didn't quite understand this aspect of our FBW control laws until we had line pilots get into the "deep stall" ( not what AF447 had). Same scenario...... relatively steep pitch and losing energy real fast. Elevators are trying to make the jet get to one gee ( corrected for attitude). If the time constants and such are not aggressive, you wind up with a high AoA that the control surfaces cannot handle.

So with the "standby gains" active, and below the default value with everything smoothly running, you are further screwed. The control surfaces don't move as fast or as far to keep you away from the stall AoA values and such.

To all here: I fully realize that the AF447 scenario will likely NEVER BE REPEATED. However, it should serve as a very serious lesson to all the "professional pilots" here that fly planes with FBW systems.

Owain Glyndwr
30th Aug 2012, 22:25
@<hidden>

This doesn't sound right (bolding), but I may not understand what you're getting at.
I'm not sure if I can explain it easily, but essentially what I am saying is that the time to achieve the desired level of steady state 'g' will not be radically different whether the C* gains are high speed or low speed values. What will be different is the time history of how you get to that state.

Amount of elevator deflection for a given SS longitudinal input is essentially the same for 330K in Normal Law, 330K in ALT2(B), and, for example, 200K in ALT2(B), an abnormally low speed for the clean configuration.

At 200K in Normal Law, elevator deflection for the above same SS input is about twice that of the ALT2 deflection.
With C* operative you cannot simply relate SS movement and elevator deflection in any dynamic sense. What is true is that for any given set of weight/CG/speed conditions the SS movement, elevator deflection and steady state load factor are uniquely related and independent of whether it is normal or alternate law in operation. In other words the steady state elevator angle/g required is independent of C*.

What does change with C* law changes is how the elevators are moved between initial and final states. Suppose one has an aft CG condition where the steady state elevator angle/g is only say 2 degrees/g and you want an increment of 0.25g (these are just for instance numbers OK?). If you just apply 0.5 degree elevator you will eventually arrive at the new trimmed state, but 0.5 degree elevator isn't going to set the world alight in terms of pitch acceleration, so it will take a long time to get there.

To avoid this C* does what I think pilots would do instinctively in these circumstances - overdrive the elevators to get the aircraft moving and then back off to avoid any excessive overswing [correct me if I am wrong] and let the aircraft come gently to the final trimmed state.

In normal law, or alternate law with standard gains the aircraft response would be a fairly rapid g response, followed by a modest overswing and a damped recovery to the desired steady state g. I suggested that this whole process would take about 6 seconds, but that was a notional value and could be anything form 4 to 7 secs depending on aircraft.

In Alt2B with the default gains the elevator overdrive would be less, the initial pitch acceleration would follow that and there would be no overswing, just a gradual build up of 'g' to the final value. From reports I have read where C* gains have been varied (on large aircraft) this final state is arrived at in about the same time as with the 'normal' laws. The pilot's perception of the dynamic response however would be very different.

In this respect I agree that the dynamic elevator deflection in normal law could be twice what it is in Alt2B.

As a result, I would think you would not ultimately achieve the same peak G value in ALT2 as in Normal, ALT2 value would continuously be lower over the period of the input and never catch up. Holding a less deflected elevator longer isn't going to eventually increase G....and the aircraft response difference would simply be one of the further reduced pitch rate for that speed. Longer time for a given FPA change, which is what a pilot would sense even though the SS 'spring' feel might be associated with different expectations.
For the reasons given above I can't agree that the 'g' in Alt2B will never catch up or that holding a less deflected elevator longer won't eventually increase 'g'. There would be a slightly longer time for a given FPA change, but (question) does the pilot "see" FPA change first as a 'g'?

My point is couldn't that paragraph in the report just refer to this directly? In the sense that the aircraft is even 'more sluggish' than 'normal sluggishness' at these speeds, I guess truly that is an 'unusual' response dynamic. But given that one is not normally at these speeds clean anyway, I would imagine a pilot assessment of 'unusual' behavior would be a bit superfluousAgreed

Owain Glyndwr
30th Aug 2012, 22:37
@<hidden> gums

Elevators are trying to make the jet get to one gee ( corrected for attitude).

Gums. maybe it is just me, but when you write this I keep on thinking that you are inferring that the aircraft is not actually flown to 1g.

If you consider the whole range of genuine 1g level flight conditions the aircraft attitude could be anything from (say) 2 degrees to 6 degrees. An accelerometer fixed to the airframe could read between 0.9994 and 0.9945. If you are going to use that accelerometer to maintain 1g level flight then you must adjust the accelerometer output to correct for those attitudes.

Is this what you meant?, because if so the reference to attitude correction is superfluous as the aircraft is actually flown to 1g period.

gums
31st Aug 2012, 00:07
Spot on, OG, that is exactly what I am saying based upon the documents provided by several here.

So if I am at 30 degrees of pitch, the actual Airbus command would be 0.87 gee. This is different than the Viper control law. Ours commanded "absolute" gee according to how we had the jet trimmed ( - one plus a bit or so, and + 3.5 gees). We had no bias for pitch attitude, so at an extreme pitch attitude, the jet would try to pull up to maintain the trimmed gee, which was mostly 1 gee.

The result of this control law was if you released the side stick the system would keep cranking in elevator to reach the one gee "command" that most of us used. The Airbus doesn't allow a gee command to be manually trimmed, and it looks to me that it always tries to achieve one gee corrected for pitch attitude. This also plays on the apparent speed stability, as the system has zero stick pressure changes to compensate for AoA changes due to speed changes - the basic "feeling" most of us had with the conventional systems and the original systems in the Chipmunk, Cub, Luscombe, et al.

Just some thots from an old FBW veteran.

OK465
31st Aug 2012, 00:12
Thank you OG & gums.

I wish you guys had taught my initial 'flight control' ground school, instead of CBT. :)

:ok:

(BTW: those elevator deflections were compared at the same weight/CG)

CONF iture
31st Aug 2012, 03:33
Lonewolf50

Thanks for the analogy you bring forward.
If I get you right, what you describe on the Seahawk helicopter is related to hydraulic issues and other servos malfunctions. An Airbus or any other more conventional aircraft is as much vulnerable to hydraulic issues. A dual HYD failure would trigger alternate law with fewer usable flight control surfaces and to switch straight to direct law for such malfunction is not the purpose of my proposition.

What I am after is everything related to probes and sensors, on which the Airbus is so dependable for its normal operation – This includes the law in force, the THS operation, the protection availability …
It is for that type of malfunctions known as unreliable data, that I would suggest a healthy degradation.

The guys are talking about ALT2, C*, one G command and so on, it is all very much interesting to try to understand what’s happening behind these words, and we all take such opportunity to educate ourselves, but in my book, direct law is the most understandable thing for a pilot who has to act now. For a given displacement of the stick there is a proportional displacement of the elevators. If not gentle enough the load factor will remind the pilot how fast his aircraft still is. If a large stick displacement don’t produce much, his aircraft is probably a lot slow.

Owain Glyndwr
31st Aug 2012, 04:00
Hi gums,

it looks to me that it always tries to achieve one gee corrected for pitch attitude.

That is just my point! The system tries to achieve one gee. The pitch attitude input to the system is only to account for the fact that in 1g level flight the accelerometer doesn't read 1.0 and that the difference depends on attitude.

Or maybe its me again :8

gums
31st Aug 2012, 04:50
The Nz command I am talking about would be that from a "strapdown" style sensor referenced to the aircraft, not a space-stabilized inertial sensor such as used for navigation and weapon delivery.

The difference between my FBW system of old and that in the 'bus is we did not correct for attitude WRT the Earth coordinate system. Ours was and is still body-oriented for the Nz command. Because the 'bus corrects for attitude, it appears to command an attitude. At small climb or descent angles, it's a small correction. Ours seemed the same when close to cruise attitudes, but we flew at extreme pitch attitudes, so our "one gee" command could help us get into the "deep stall" if we relaxed pressure on the stick when zooming up at 70 or 80 degrees. I don't see this as a factor with AF447.

The point I keep trying to make is that the 'bus appears to command an attitude, but it's a gee/rate command with bias for pitch attitude.

My second point is "hands off" and even at small pitch attitudes like 10 or 15 degrees, that trying to maintain a constant Nz will cause the elevator to trim nose up, and then the THS. Because the 'bus has more drag than our Viper, speed/energy decays quickly, and it is possible to reach a stall AoA even with "hands off" ( as BEA report asserts). With no AoA protections, you're on your own. Holding the stick back for minutes doesn't help at all.

Lastly, the "feel" of non-FBW planes with positive static stability is helpful, as trying to fly slower than the trimmed speed/AoA requires more back stick. Trying to fly faster requires forward stick pressure/movement. OTOH, most FBW systems provide "neutral speed stability" regardless of the AoA, cee gee and/or static stability margins. So we don't get that feedback like in the old days, even with fully hydraulic control valves and no artificial "feel" such as the B777 has.

Pretty good discussion on this aspect of the control laws, way I see it.

Owain Glyndwr
31st Aug 2012, 07:47
The Nz command I am talking about would be that from a "strapdown" style sensor referenced to the aircraft, not a space-stabilized inertial sensor such as used for navigation and weapon delivery.

OK, A330 has a strapdown sensor so we are talking same language

The difference between my FBW system of old and that in the 'bus is we did not correct for attitude WRT the Earth coordinate system. Ours was and is still body-oriented for the Nz command. Because the 'bus corrects for attitude, it appears to command an attitude.

That is an important difference, but I don't see how that implies that the 'bus commands an attitude. I see the pitch correction as a technical requirement brought about by the laws of physics, not a deliberate attempt to manipulate flight path. [Which is why I think that the phrase "tries to achieve one gee corrected for pitch attitude" might give the wrong impression].

The point I keep trying to make is that the 'bus appears to command an attitude, but it's a gee/rate command with bias for pitch attitude.

This is the point I don't get. The AI system, as I understand it, seeks to maintain a commanded gee in earth axes not body axes as in your Viper. With that assumption the pitch attitude term is a necessary correction feature but not a command. The basic system is a simple gee demand with gee/pitch rate feedback arranged to optimise transient response throughout the envelope. [For completeness, the THS becomes the integral part of a standard P/I control system]

My second point is "hands off" and even at small pitch attitudes like 10 or 15 degrees, that trying to maintain a constant Nz will cause the elevator to trim nose up, and then the THS. Because the 'bus has more drag than our Viper, speed/energy decays quickly, and it is possible to reach a stall AoA even with "hands off" ( as BEA report asserts). With no AoA protections, you're on your own. Holding the stick back for minutes doesn't help at all.


Agreed, except to remark that in A330 terms 15 degrees is not a "small" attitude. One needs to add a proviso though - the speed divergence only kicks in when the (thrust - drag) vs speed curve slope goes negative and even then the initial rate of divergence would be very low, although it gets more exciting as one nears stall conditions. The argument that the A330 system could take the aircraft into stall even "hands off" is a valid one, but really only becomes significant (in AF447 terms) because the aircraft was put in the vicinity of stall in the first place.

Lastly, the "feel" of non-FBW planes with positive static stability is helpful, as trying to fly slower than the trimmed speed/AoA requires more back stick. Trying to fly faster requires forward stick pressure/movement. OTOH, most FBW systems provide "neutral speed stability" regardless of the AoA, cee gee and/or static stability margins. So we don't get that feedback like in the old days, even with fully hydraulic control valves and no artificial "feel" such as the B777 has.

Agreed

Pretty good discussion on this aspect of the control laws, way I see it.

Yup!

HazelNuts39
31st Aug 2012, 08:21
the speed divergence only kicks in when the (thrust - drag) vs speed curve slope goes negative and even then the initial rate of divergence would be very low,You mean in level flight?

Owain Glyndwr
31st Aug 2012, 08:36
@<hidden>

You mean in level flight?

Yes of course - any gee puts the CL and Cd up and makes deceleration more rapid.

syseng68k
31st Aug 2012, 11:31
CONFiture, #182

Lets keep the magic of the Airbus when everything is known at 100% not lower.
I tend to agree with that, though perhaps not to that extreme. However, it would have the desirable effect of forcing airlines to put more emphasis on manual flying skills, which seem to have become neglected, fwics.

Simplify, simplify, where is my razor ?...

syseng68k
31st Aug 2012, 12:01
Owain Glydwr, #195

The argument that the A330 system could take the aircraft into stall even "hands off" is a valid one, but really only becomes significant (in AF447 terms) because the aircraft was put in the vicinity of stall in the first place.
That sounds like a serious fault in the design, in that under such circumstances, the effect is a positive feedback loop that might be unexpected, not trained for and thus very difficult to recover from.


This is the point I don't get. The AI system, as I understand it, seeks to maintain a commanded gee in earth axes not body axes as in your Viper. With that assumption the pitch attitude term is a necessary correction feature but not a command.
No info as to where it would get it's acceleration / g info from, but would assume the INS, which has a triad of accelerometers. It wouldn't be enough to just take the G (vertical) value alone, as the value would affected by both pitch and roll. The assumption would be that they are using the processed outputs, via a bit of trig etc, to resolve earth axis vertical from 2 of the 3 accelerometers.

Just edited to add some content, rather than the usual hobby horse criticism about fragile at the edges, which i'm still uncomfortable with :-)...

Keep it up - some of the best techlog/af447 stuff i've seen for months...

PJ2
31st Aug 2012, 15:26
Yes, excellent discussions!

Owain Glyndwr, twenty years ago when checking out on the A320, one of the instructors observed that because the system maintains 1g, that it would gradually increase elevator deflection in the climb to cruise altitudes (where gravity is very slightly less, was the claim...), to maintain 1g and that a tiny ND input was required during the climb. I did a lot of thinking about the implications but never found a clarification. It seemed logical enough but as a pilot I nevertheless doubted that the statement was true. Is there any clarification that might put this notion to rest? Thanks...

HazelNuts39
31st Aug 2012, 17:07
Hi PJ2,

Yes, excellent discussion indeed!

I think the gravity argument is basically correct. But there are more changes during climb that have probably a greater effect on elevator and/or gee:
- due to fuel burned weight and c.g. changes (trim change)
- thrust reduces (trim change)
- due to reducing thrust FPA and vertical speed are constantly reducing, i.e. gee is slightly less than one, except when speed changes from constant CAS to constant Mach and FPA and V/S increase by about 68%.
- climbing at constant Mach AoA is increasing (trim change)

rudderrudderrat
31st Aug 2012, 18:27
There is an interesting article in the Summer 12 edition of "focus" the magazine published by the UK Flight Safety Committee.

Radical revisions needed for pilot training, aircraft certification and simulator fidelity.
by Fred George

Investigators with the French Bureau d'Equetes et d'Analyses (BEA), the agency charged with investigating the crash of Air France Flight 447, now are focusing on a breakdown in situational awareness on the part of the flight crew and possible pilot error as contributing factors in the June 2009 mishap that killed 228 people when the Airbus A330 crashed into the South Atlantic. The latest findings broaden the scope of the inquiry well beyond a fly-by- wire flight control malfunction, possibly caused by iced-up pitot probes.

While the BEA is far from completing its investigation of the AF447 accident, its most recent progress report again focused the aviation community's attention on the perils of loss of control (LOC) incidents, especially at high attitude. This is a multifaceted challenge because improved stick-and-rudder skills are unlikely to eliminate the problem entirely.

"The Air France 447 crash was a seminal accident. We need to look at it from a systems approach, a human/technotogy system that has to work together. This involves aircraft design and certification, training and human factors. lf you look at the human factors alone, then you're missing half or two-thirds of the totaI system failure," says C. B. "Sully" Sullenberger, a 20,000-hour retired airline pilot and former fighter pilot.

Celebrated for his successful ditching of a powerless A320 in the Hudson River, Sullenberger is now a writer, aviation consultant and public speaker. He notes that there were 12 or 13 similar upset mishaps prior to AF447 in recent years, but that Air France 447 has attracted the most public interest. Sullenberger says that there needs to be a global safety reporting network that will enable the aviation industry to identify problems more quickly and find solutions.

Sullenberger says it's easy to blame the pilots in the AF447 crash while overlooking other contributing or causal factors. "l believe the transport airplane community, as a whole, would not expect the crew to lose all three speed indicators in the cockpit," he said. "That's like amputating the wrong limb in a hospital" because criticaI information was not available.

He also believes that accurate airspeed indications alone aren't the best data the crew needs to recover from an upset. That requires knowing the wing's criticaI angle of attack (AoA). "We have to infer angle of attack indirectly by referencing speed. That makes stall recognition and recovery that much more difficult. For more than half a century, we've had the capability to display AoA (in the cockpits of most jet transports), one of the most critical parameters, yet we have choose not to do it."

Training also needs improvement. "Currently, to my knowledge, air transport pilots practice approaches to stalls, never actually stalling the aircraft. These maneuvers are done at low altitude where they're taught to power out of the maneuver with minimum altitude loss." In some aircraft, they're taught to pull back on the stick, use maximum thrust and let the alpha floor (AoA) protection adjust nose attitude for optimum wing performance.

"They never get the chance to Practice recovery from a high-altitude upset," he continued. "At altitude, you cannot power out of a stall without losing altitude. "And depending upon the fly-by' wire flight control system's alpha floor protection isn't the best way to recover from stall at cruise attitude.

Maintaining situational awareness is another challenge in highly automated aircraft. "There are design issues in some aircraft that I've always wondered about," Sullenberger said. "For instance, I think the industry should ask questions about situationaI awareness and non-moving auto throttles. You lose that peripheral sense of where the thrust command is, especially in a big airplane where there is very little engine noise in the cockpit.

"ln some fly-by-wire airplanes, the cockpit flight controls don't move. That's also Part of the peripheraI perception that pilots have learned to pick up on. But in some airplanes that's missing and there is no control feel feedback," he said.

Owain Glyndwr
31st Aug 2012, 19:18
PJ2
twenty years ago when checking out on the A320, one of the instructors observed that because the system maintains 1g, that it would gradually increase elevator deflection in the climb to cruise altitudes (where gravity is very slightly less, was the claim...), to maintain 1g and that a tiny ND input was required during the climb.

I'm entirely with HN39 on this one. Presumably your instructor was suggesting that since gravity is very slightly less the effective "weight" would be less leading to a slightly lower lift coefficient and therefore less up elevator needed.

Good theory, but in practice entirely swamped by all the other effects listed by HN39. I would add another one - if you are in gums' Viper or were in Concorde then the direction of flight (E/W or W/E) could also have an effect ;)

DozyWannabe
31st Aug 2012, 19:41
That sounds like a serious fault in the design, in that under such circumstances, the effect is a positive feedback loop that might be unexpected, not trained for and thus very difficult to recover from.

Hmm - we're talking about an infinitessimally small deviation over time, perceptible only because of the accuracy of modern instruments. I don't have the time or the wherewithal to crunch the numbers, but I suspect that the amount of time it would take for this anomaly to take the aircraft from Max cruising altitude into coffin corner would be longer than the A320 series' range could allow.

I remember someone saying early in this discussion that this anomaly was rectified in the A330/340 systems.

The evidence does not support AF447 being imperceptibly taken into coffin corner by the systems, it very clearly implies that the aircraft was controlled into the stall.

Lyman
31st Aug 2012, 19:51
From Owain Glyndwr...

"This is the point I don't get. The AI system, as I understand it, seeks to maintain a commanded gee in earth axes not body axes as in your Viper."

How does the a/c orient itself when it unloads? Surprising to me was the THS cranking in when the beginning of the "momentum only" portion of the "climb" began. At the top of the trajectory, what tells the load system monitor to adjust?

Dozy?.."The evidence does not support AF447 being imperceptibly taken into coffin corner by the systems, it very clearly implies that the aircraft was controlled into the stall."


Boy howdy.....

DozyWannabe
31st Aug 2012, 19:58
Surprising to me was the THS cranking in when the beginning of the "momentum only" portion of the "climb" began.

It's not rocket science - the THS is unloading the elevator demand commanded by the PF, as per design.

At the top of the trajectory, what tells the load system monitor to adjust?

The pilot's commands vs. the current aircraft attitude. Remember that in Alternate Law and below, the system is designed to defer to the human pilot and will not interfere with any command given. The flight control system has no concept of stall or operational ceiling with hard protections inoperative - even in Normal Law it only understands and acts on Alpha Max.

Dozy?.."The evidence ... very clearly implies that the aircraft was controlled into the stall."
...
Boy howdy.....

How else would you describe consecutive and sustained back-stick commands?

Lyman
31st Aug 2012, 20:14
"How else would you describe consecutive and sustained back-stick commands?"

That the aircraft would have stalled without them?

Lyman
31st Aug 2012, 20:47
Dozy... "It's not rocket science - the THS is unloading the elevator demand commanded by the PF, as per design."

Nope, not at full deflection of elevators....

CONF iture
31st Aug 2012, 21:13
even in Normal Law it only understands and acts on Alpha Max.
Absolutely not, as early as alpha prot it quits trimming.

DozyWannabe
31st Aug 2012, 21:19
@<hidden> : Based on what evidence?

The discrepancy we're talking about here is relatively minute. Even if the tendency hadn't been corrected for the widebodies, you'd be looking at hours and hours of flight between AP disconnect at 35,000ft and reaching 38,000ft - the time it would take is certainly more flight hours than AF447 had remaining, and it would have had to escape the attention of the crew over that period of time.

In the AF447 case, from autoflight disconnect to impact is a matter of minutes. The sidestick deflection (measured at source) is consistent with the flight trajectory - ergo the evidence strongly implies that the climb, stall and subsequent actions were due to crew input.

Autotrim is commanded based on flight control position over time (i.e. a trend) - whether the elevators are currently deflected or not.

@<hidden> iture:

Alpha protection is a systems procedure triggered based on a variable derived from Alpha Max - the point at which it triggers is not a hard-coded value, but a function. The hard protections are implemented by a subsystem that operates outside the main flight control logic. Upon loss of Normal Law, that subsystem is inhibited. The reason the protection fires just shy of Alpha Max itself is to take into account conditions whereby Alpha Max is on the edge of the flight envelope that cannot be reliably measured by the system (e.g. tailwind).

Lyman
31st Aug 2012, 21:32
You are addressing a question not asked, with a response that does not pertain...

"The discrepancy we're talking about here is relatively minute. Even if the tendency hadn't been corrected for the widebodies, you'd be looking at hours and hours of flight between AP disconnect at 35,000ft and reaching 38,000ft - the time it would take is certainly more flight hours than AF447 had remaining, and it would have had to escape the attention of the crew over that period of time."

Does a/p fly attitude, airspeed, or load... Hands off, what does the a/c fly in AL2? What rate?

What do you devine is "unusual command response"? You have a source?

PJ2
31st Aug 2012, 21:45
HN39, O.G., my thanks for clarifying yet another item. For a pilot this is really interesting.

Apart from understanding how all this works, it leads me closer to conclusions that such knowledge remains valuable to our craft for those flying transports and that "nuts-and-bolts" courses, far from being replaced by notions such as "managing the aircraft", are still relevant to what we do (and did!) for a living. Continuous education is the responsibility of all professionals but it would be interesting to revisit curriculum design for pilot courses for the Airline Transport License and at the airlines where training footprints, concerning fbw (C*), autoflight and aircraft performance topics. Anyway, that's for another thread! Once again, thank you.

DozyWannabe
31st Aug 2012, 22:01
Does a/p fly attitude, airspeed, or load... Hands off, what does the a/c fly in AL2? What rate?

Autopilot "flies" flightpath, constantly correcting itself if deviation is detected (see the "zipper" trace you were interested in earlier). In Alternate 2, the aircraft holds commanded flightpath in pitch and is roll direct.

The discrepancy in the A320 being talked about is something on the order of 1 foot every 20 minutes, depending on external conditions.

What do you devine is "unusual command response"? You have a source?

You've lost me - where did I use the phrase "unusual command response"?

Lyman
31st Aug 2012, 23:00
You didn't, BEA did....

"Autopilot "flies" flightpath, constantly correcting itself if deviation is detected (see the "zipper" trace you were interested in earlier). In Alternate 2, the aircraft holds commanded flightpath in pitch and is roll direct.

How does Pilot determine which is commanded, and which is flightpath? Does he have to assume the displayed flightpath is his command? Trusting soul...

DozyWannabe
1st Sep 2012, 01:25
If autoflight is on, then autoflight commands flightpath. If it isn't, then flightpath is manual and determined/commanded by the crew. Both are commanded - as far as the flight control logic is concerned it doesn't matter whether the command comes from the autopilot or the human crew.

Some may disagree, but in commonly understood terminology autotrim is not automation in the classic sense because it does not determine flightpath independently. Instead it is slaved to the control inputs of the autopilot or the human pilot depending on which is in control.

If the sidestick traces indicated neutral or nose-down pitch throughout the sequence and the aircraft pitched up into climb and stall, *then and only then* would the systems logic deserve to be under scrutiny, but that's not what happened. The sidestick traces clearly indicate repeated and sustained nose-up inputs which correlate closely with the aircraft flightpath.

CONF iture
1st Sep 2012, 02:14
Alpha protection is a systems procedure triggered based on a variable derived from Alpha Max - the point at which it triggers is not a hard-coded value, but a function. The hard protections are implemented by a subsystem that operates outside the main flight control logic. Upon loss of Normal Law, that subsystem is inhibited. The reason the protection fires just shy of Alpha Max itself is to take into account conditions whereby Alpha Max is on the edge of the flight envelope that cannot be reliably measured by the system (e.g. tailwind).
As usual, you're moving air around with some stuff made on your own, but don't address the point in question (http://www.pprune.org/7389302-post209.html).

bubbers44
1st Sep 2012, 02:18
A Boeing yoke works the same way. We don't have protections, just warnings. Try pulling full back on any Boeing, which probably never happened, and see what happens because the other pilot would slap him on the side of his head and say I have the aircraft. Yes it is unfair because the other Boeing pilot can see he is doing something really stupid and intervenes.

CONF iture
1st Sep 2012, 03:15
Try pulling full back on any Boeing, which probably never happened, and see what happens because the other pilot would slap him on the side of his head and say I have the aircraft
It did happen already, and without the other pilot intervening ...

bubbers44
1st Sep 2012, 04:05
Yes, all aircraft types can have incompetent pilots. Seeing what the other pilot is doing by a yoke gives you the ability to smack him on the side of the head quicker. With incompetent FO's it probably doesn't matter. Airplanes shouldn't operate with a pair like that. Guess they do though.

HazelNuts39
1st Sep 2012, 11:02
Alpha Max is on the edge of the flight envelope that cannot be reliably measured by the system (e.g. tailwind).I'd be interested to know how tailwind enters into the equation?

OK465
1st Sep 2012, 13:44
One more question for the FBW flight control knowledgeable folks here:

With gains fixed for 330 knots, can you get FULL nose down elevator in a developed stall?

How would stall recovery characteristics be affected with fixed gains versus active gains?

Lyman
1st Sep 2012, 13:52
Can one achieve sufficient ND to escape the STALL in the first place?

Because in a stable aircraft, the Nose drops on its own?

Say PF sees the error of his ways, and wants full ND, instant. Does he get it?

Would not Direct Law be a better Law in this condition?

After erasing the protection and entering Alternate Law, controls hobble a potential recovery? Madness.

rudderrudderrat
1st Sep 2012, 14:13
Can one achieve sufficient ND to escape the STALL in the first place?
Hi Lyman,
Page 90 of the final report shows the elevator at -30 degs (Max) and the stab trim at -13 degs (Max).
Why do you suppose maximum Nose Down Elevator & Stab Trim would not be available if the stick was held fully forward?
If that was not sufficient to lower the nose, then they could have selected idle power.
Neither of the above were attempted because they never diagnosed (believed?) they had stalled.

Lyman
1st Sep 2012, 14:30
Rate. It took sixty seconds for the THS to cycle max. It took forty seconds to STALL.

Seems to me had the a/c degraded into Law Direct, the Stall happens earlier, and recovery if any, begins with more energy. Also, the likelihood of tail low entry diminishes?

With three lost ADR, the gains go to 330 knots default? Doesn't that have the effect of acclimating the flying pilot to gentle response in Pitch, and without speeds or AOA, he is lulled into confusion? , his senses are Acclimated to things happening at the airplanes rate, slowed, confident, non emergent?

OK465
1st Sep 2012, 15:06
I would think that full nose down elevator at 330 knots would provide for quite a bit more than -1G. :yuk:

With the load factor protection in effect, and fixed gains, wouldn't this limit the amount of elevator deflection for a full ND SS input at any actual speed?

PJ2
1st Sep 2012, 15:49
OK465;

In the sim exercises, the SS was held full forward to achieve about 10degND pitch. The THS followed up on the command and returned to about a -3deg position. Recovery took about 40 seconds. (Note for others: I realize the sim cannot replicate full-stall conditions due absence of data but neither is the behaviour completely irrelevant).

For the exercise anyway and from my pov, there was sufficient elevator available to get the nose down, and the job was made easier by the THS following up the SS ND commands.

OK465
1st Sep 2012, 16:27
PJ:

Are you sure you had 330 knot fixed gains?

With full forward SS at 330 knots you get about 1/4 ND elevator deflection.

(With full forward stick, you can do an outside loop in some aircraft in 40 seconds. :))

Lyman
1st Sep 2012, 16:34
Endlessly, monotonously, the pilot is trained to fly one gee. It is grail. Nothing can go wrong at one gee, even the pilot not flying was disturbed by "excessive" lateral inputs....

So any number less or more is to be avoided. Add a nagging suspicion of overspeed, and voila, don't ferchrissakes "lower the nose..."

Organfreak
1st Sep 2012, 16:37
May I ask a stewpid newbie question? OK, thanks, I will.

I have always heard/read that airliners travel "at about 600 MPH." Actual speeds are sometimes referred-to (by badly informed authors?) as 500-something MPH.

330 KTS apparently translates to ~380 MPH. What gives? I do realize that actual airspeed is different from ground speed. What am I missing here?

:confused:

PJ2
1st Sep 2012, 17:01
OK465;

No, I don't know whether we had 330kt gains. I'm probably not providing sufficient information but the exercise began at cruise speed, (273kts), I believe the sim/check pilot failed 3 ADRs for the exercise, the pitch was increased, the sim stalled and the recovery was started at various points in the descent. I realize control systems are capable of outside loops etc but of course there is no indication of the nature of few gains for the pilots and the FCOM isn't sufficiently detailed so I can't offer an accurate assessment of what we had. I believe we had full down deflection of the elevator as indicated on the Lower ECAM Flight Control page but I'd have to review the videos to confirm. One question I would have regarding "high gains" (or 1/4 elevator only available) is, would the THS still follow through? I expect it would as this is still a trimable force exerted by the elevators which would be trimmed out, but these are esoteric areas for a non-engineer pilot of these airplanes!

Machinbird
1st Sep 2012, 17:07
What gives? I do realize that actual airspeed is different from ground speed. What am I missing here?
Simply the difference between True Airspeed and Indicated Airspeed.
Indicated airspeed - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Indicated_airspeed)
True airspeed - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/True_airspeed)

The first airspeed controls many important aerodynamic control parameters such as g available and angle of attack.
The second airspeed (TAS) indicates how fast you are booking through the molecules of the atmosphere.

OK465
1st Sep 2012, 17:37
I believe the sim/check pilot failed 3 ADRs for the exercise...

Recalling the picture of the PFD with the FPV visible, one would assume only 2 ADR's were failed. You would not have an FPV with 3 ADR's failed.

Variable Airspeed Drift malfunction may be a better way to do this than constrained ADR failure. The ECAM messages are ADR disagree ones (like 447) and not ADR fault.

Double ADR fail is indeed ALT2 and good for stall demos with the FPV, but it is not ALT2(B).

...but these are esoteric areas for a non-engineer pilot of these airplanes!

Agreed, but they do fall into the category of nuts and bolts. Hard to keep an old Flight Engineer trained guy like me from pursuing this kind of 'trivia'. Remember the old Burtek Boards? :)

Owain Glyndwr
1st Sep 2012, 18:27
@<hidden> 465

With gains fixed for 330 knots, can you get FULL nose down elevator in a developed stall?

Sure - why not? The gains, as I tried to explain, relate to the transient response characteristics; that is to say to the first 3 or 4 seconds of any manoeuvre. If the elevator deflection is not enough to satisfy the pilot's demand the system goes on winding in elevator until the demand is met. The 'gains' are irrelevant in that context. At the speeds involved in a developed stall there would be no hinge moment restriction on control deflection or rate of movement.

How would stall recovery characteristics be affected with fixed gains versus active gains?

Not at all - it is the steady state conditions that will dictate stall recovery not the entry transient.

I would think that full nose down elevator at 330 knots would provide for quite a bit more than -1G.

So it would, but (a) the aircraft was not at 330 kts - more like 155 kts and (b) you have to allow for the deflected THS opposing the down elevator.

With the load factor protection in effect, and fixed gains, wouldn't this limit the amount of elevator deflection for a full ND SS input at any actual speed?

No, it is the other way around. One can look at it several ways, but if you go back to the graph of AoA vs equivalent elevator angle that I posted way back you will find that with 13 deg NU THS (-19.5 deg equivalent elevator) and full ND elevator (+15 deg) giving an equivalent -4.5 (NU) elevator deflection, the aircraft would settle out at about 4 or 5 deg AoA. At the speed then in existence the 1g AoA would have been about 10~12 deg I think, so the best one can hope for until the THS starts to move back down is around 0.5g (ish). Difficult to say when negative load factor protection would have kicked in because the THS movement and general speed increase go together.


With full forward SS at 330 knots you get about 1/4 ND elevator deflection.


Where does this come from please?

OK465
1st Sep 2012, 19:09
Previous quote:

I think this would lead the system to apply less elevator (to drive the pitch acceleration) than it would normally use at these low speeds,

Then you mean this only as a transient with the eventual elevator deflection for a sustained full ND SS input at 'slow' speed being the same in both Normal & ALT2(B)?

Where does this come from please?

SD Flight Control page with sustained full ND SS input at both 330K & 200K in ALT2(B). It is constant, and the same in Normal at 330K. I don't even see full elevator deflection in Normal at 200K with a full ND SS input.

So it would, but (a) the aircraft was not at 330 kts...

But the FCC's were. I'm still trying to reconcile this with what I've encountered. I'm just not seeing what you're describing.

In any airplane I ever flew, I certainly never claimed to have all the answers, but I always strived to have all the questions. :)

HazelNuts39
1st Sep 2012, 19:16
Difficult to say when negative load factor protection would have kicked in because the THS movement and general speed increase go together. Does negative load factor require negative AoA (zero lift at about -2°)?

SD Flight Control page with sustained full ND SS input at both 330K & 200K in ALT2(B). It is constant, and the same in Normal at 330K. I don't even see full elevator deflection in Normal at 200K with a full ND SS input.
How about the THS, did it move at all?

Owain Glyndwr
1st Sep 2012, 19:41
@<hidden> 465

Then you mean this only as a transient with the eventual elevator deflection for a sustained full ND SS input at 'slow' speed being the same in both Normal & ALT2(B)?

Yes

SD Flight Control page

Sorry, I don't recognise what you mean by 'SD'

But the FCC's were. I'm still trying to reconcile this with what I've encountered. I'm just not seeing what you're describing.

We may be a bit at cross purposes. I was referring to the aircraft response to actual full ND elevator deflection. Were you perchance referring to full ND SS command? My point was that at low speed you will need a lot more deflection for a given delta gee than you will at high speed.

@<hidden>
Does negative load factor require negative AoA (zero lift at about -2°)?

Yes - I agree zero lift at about -2 deg.

OK465
1st Sep 2012, 19:53
Sorry, I don't recognise what you mean by 'SD'

Apologies,

Systems Display (normally central lower display unit MFD), shows the position of all flight control surfaces at any time, as well as FCC status.

Were you perchance referring to full ND SS command?

Yes

My point was that at low speed you will need a lot more deflection for a given delta gee than you will at high speed.

Exactly, but can you get it when the FCC's continuously think you're at 330K?

I understand you're saying that you can. I may be misinterpreting what I'm seeing.

Always possible.

edit: How about the THS, did it move at all?

I think I see what you're getting at, as far as elevator effectiveness, but THS 'specifically' not noted. Another 'question' to ponder over a 3 day weekend.

PJ2
1st Sep 2012, 20:40
OK465, I can't speak to the method used to bring about the UAS event. The FPV was available during the descent as, (I believe) one ADR was reinstated.

We just had chalk and a board for the DC8 plus some stuff from the maintenance manuals and other sources. The later CBTs were initially pretty dry but they got better. Like you I prefer understanding what I'm doing in my aircraft. I prefer nuts-and-bolts (or bits and bytes) just because it's fun.

If the simulator experience is to be believed then for whatever technical or aerodynamic reasons it demonstrated that the aircraft was recoverable with full ND stick held in until the stall warning ceased. Secondary accelerated stall was not a problem in the pull-out. "Why?" again in technical and aerodynamic terms , is an excellent question which is why contributions on this topic are such excellent reading. O.G. has previously offered varying recovery scenarios and the numbers for the higher-altitude recovery weren't that different from what we observed. We never tried recoveries below about FL300 and when I get a chance I'm going to try them.

TTex600
1st Sep 2012, 21:00
Excellent discussion.

A question if I may.

If after years and thousands of point counterpoint, an internet group of obviously intelligent/knowledgable people don't understand just how the THS/pitch control behaves in all circumstances, does anyone really expect pilots to know how the aircraft behaves after only a day of flight control systems training?

And a point........this question would never come up with a DC9 :ok:

Owain Glyndwr
1st Sep 2012, 21:55
@<hidden>

Exactly, but can you get it when the FCC's continuously think you're at 330K?

I understand you're saying that you can. I may be misinterpreting what I'm seeing.No, I think it is I who may have it wrong :ouch:
I see what you are getting at now. I had been assuming that only the C* gains defaulted to their 330 kt values, but from what you describe it sounds as if the steady state gain (delta gee/unit SS deflection) may default as well. In that case full ND sidestick would only produce the elevator deflection to give (I suppose) -1g at 330 kts so that at 155 kts the available gee would be much less. [But in that case how did they get 30 deg NU elevator on AF447?]

If the maximum ND elevator were only 5 deg one could only get down to about 15 deg AoA until the THS came off its stop. OTOH, given the insistence of many contributors that professional pilots would be unlikely to push beyond 10 or 15 deg ND pitch, perhaps consideration of -1g is a bit academic?

bubbers44
1st Sep 2012, 22:03
No matter what the nose up trim goes to we were trained to roll instead of stall. No airline trained us that but somewhere in my background I knew if I had runaway trim just bank until the nose is where you want it. 90 degrees is fine to get started. Then pitch and roll to what ever with reduced power makes a flyable airplane again. Once stabilized set flaps so it can be landed. Full up trim isn't a problem. It seemed reasonable to me. Banking requires more back pressure so let it help you.

OK465
1st Sep 2012, 22:52
[But in that case how did they get 30 deg NU elevator on AF447?]

OG:

A good question.

Maybe under those ambient conditions full SS NU/full NU elevator at 330K comes up 'short' of +2.5G, just as it would come up 'long' of the -1G with full ND elevator.

I don't have the Va numbers handy.

But I agree at first glance it appears that something 'short' of full NU elevator would achieve +2.5 at 330K. :confused:

jcjeant
1st Sep 2012, 23:00
It certainly has the interest to human factors group .... ?
At the beginning of the accident pilots did not seem to have heard or considered the stall alarm .. it probably because of the surprise or overwork and stress-induced
By cons, paradoxically .. after 4 minutes during which the stress has accumulate ... they recognize (completely agree) the Pull Up alarm and respond to this alarm (pull)
Stress is selective about alarms ?
feet
2 h 14 min 10,8 You’re pitching up
2 h 14 min 16,4 SV : sink rate
2 h 14 min 17,0 SV : pull up
2 h 14 min 18,0 Go on pull
2 h 14 min 18,6 SV : pull up
2 h 14 min 19,2
2 h 14 min 19,7
Let’s go pull up pull
up pull up

SV : pull up
2 h 14 min 20,8 End of C-chord
2 h 14 min 20,9 SV : stall
2 h 14 min 21,5 SV : stall
2 h 14 min 21,9 continuous C-chord
2 h 14 min 22,2 SV : pull up
2 h 14 min 22,3 SV : priority right

Lyman
1st Sep 2012, 23:01
Is that why the THS started to wind up?

I know you think I am barking up the wrong tree, OK, but something is not kosher here, yet the DFDR spells it out, AL2b forever...

I still think the THS was inhibited at -3.2 degrees (NU). Early on.

HazelNuts39
1st Sep 2012, 23:10
[But in that case how did they get 30 deg NU elevator on AF447?] Doesn't the achieved 'gee' come in? The sidestick may have been demanding +2.5 g, but the stalled airplane, even with elevator and THS fully NU, couldn't comply?

OK465
1st Sep 2012, 23:21
Lyman:

I don't know.

'Inhibited', strictly speaking, I assume would not allow the 'apparent' .2-.3 or so degree change during the initial decel and initial pushover (which would have slowed the decel rate)?

This scenario apparently exited a game of inches at about 215K.

Linktrained
2nd Sep 2012, 00:51
An Emergency Descent, for whatever reason, probably starts at Altitude and at cruising speed. Would "10 or 15 degrees ND pitch" be the kind of pitch which would be appropriate, if an Emergency Descent were required ?
Altering from a slow (unrecognised) stall with excessive NU pitch to "10 or 15 degrees ND" would feel unusual/uncomfortable in terms of Gee. (Most people seldom experience 0 Gee, except momentarily at a fairground.)

gums
2nd Sep 2012, 02:57
@<hidden> Nuts: You may have cracked the code.

Doesn't the achieved 'gee' come in? The sidestick may have been demanding +2.5 g, but the stalled airplane, even with elevator and THS fully NU, couldn't comply?

[edit] Yep, if the jet can't give you anymore, than it's the same as a conventional plane, like a J-3 Cub. you can "command" all you want, but the plane and HAL won't help.[edit]

One problem with the commercial planes is you can't fly them to the limits of the FBW "protections" or "laws" during training. Best I can figure, you can't introduce failures and such in flight. So the pilots have to depend upon sim flights, right?

Our primitive system 35 years ago allowed us to demonstrate the FBW limits on the very first flight with a newbie. Pull, pull, pull hard as you want. O.K., see AoA reach limit, but keep pulling. O.K. now command full roll. O.K. release some back pressure, even push forward. [edit] We never knew if we had reached the actual capabilities of the jet except in one case- the deep stall, where even HAL couldn't provide enuf nose down to break the stall, regardless of our stick input. Two decades later, there was an actual training program to expose pilots to those aero conditions that HAL could not handle.[edit]

[edit] The deal is that most FBW control laws never allow the jet to reach its aero limits. In a few cases, you will actually get to a condition that the "laws" and control surface limits come into play. With degraded system inputs like airspeed/dynamic pressure then all bets are off. Then we ignore AoA. So we're in a hybrid control law that may or may not "help" us. Without the traditional "feel" of more back stick or less back stick that is related to AoA/speed, then you are in trouble. The THS implementation doesn't help, IMHO. [edit]

Lyman
2nd Sep 2012, 04:13
"Consequently, the BEA recommends that:
EASA ensure the integration, in type rating and recurrent training programmes, of exercises that take into account all of the reconfiguration laws. The objective sought is to make its recognition and understanding easier for crews especially when dealing with the level of protection available and the possible differences in handling characteristics, including at the limits of the flight envelope; [Recommendation FRAN-2012-039]"

Thirty years on, no more :

"What's it doing now?"

Owain Glyndwr
2nd Sep 2012, 10:13
@<hidden>

Reason: one cannot possibly write as one attempts to think Boy, do I agree with that one!

Maybe under those ambient conditions full SS NU/full NU elevator at 330K comes up 'short' of +2.5G, just as it would come up 'long' of the -1G with full ND elevator.
I don't have the Va numbers handy.
Va at FL350 and 205t would be about 260 kts CAS. By definition the aircraft would stall at 2.5g at that speed. On my sums the elevator needed in those conditions would be about 9 deg without any help from the THS, so it would be a long way from coming up ‘short’ at 330 kts CAS

@<hidden> & gums

Doesn't the achieved 'gee' come in? The sidestick may have been demanding +2.5 g, but the stalled airplane, even with elevator and THS fully NU, couldn't comply?
That’s where I started, but so far as I can see it doesn’t explain OK’s observations.


With full forward SS at 330 knots you get about 1/4 ND elevator deflection. [Note: from subsequent discussion I take this to read “with full forward SS and with the system gains set at their 330 kts values”]
SD Flight Control page with sustained full ND SS input at both 330K & 200K in ALT2(B). It is constant, and the same in Normal at 330K. I don't even see full elevator deflection in Normal at 200K with a full ND SS input.
The logic that if present elevator is insufficient to provide the gee demanded by stick position then the system will increase the elevator deflection until the demand is satisfied must apply in both directions.
So if the demanded gee from full forward SS in OK’s simulation exercise was satisfied by ¼ ND elevator then the answer to his original question:
With gains fixed for 330 knots, can you get FULL nose down elevator in a developed stall? is that you can get all you need to satisfy the limiting manoeuvre capability built into the control system, even if this is a lot less than full elevator travel.


However, if ¼ ND deflection was not enough to satisfy the commanded gee then following the logic that led to 30 deg NU but going in the opposite direction one should have seen more than ¼ ND elevator.


To repeat though – ¼ ND elevator seems to be nowhere near enough to provide the -1g manoeuvre limit built into the protection system.
And finally, I have just been looking at a video of an A330 simulation of AF447 stall and recovery kindly supplied by another PPRuNer, and one of the sequences shows full ND SS to be accompanied by at least ¾ ND elevator.
Help!