Airbus crash/training flight

[hetfield]

If speed brakes (extension/arming), slats/flaps, or gear were commanded or extended either alternately or normally - does this change any auto-pilot, stall, FADEC logic

AFAIK, plenty......

[captplaystation]

Many years ago I remember being told on my DC9 course that you should always lower the gear before arming the speedbrake for landing, the reason given was that in case of a problem with Air/Ground logic you would receive full ground spoiler on selecting gear down. :eek:
I was led to believe that someone had learned this the hard way, and continued to respect this sequence of selection in 20 yrs of 737 flying.
Can someone tell us if this failure mode is feasible with A320 Air/Ground logic failure.

[Clandestino]

There are no alternate procedures for extending flaps/slats or arming ground spoilers on A320. Manual gear extension will leave the gear bay doors dangling and will deprive you of nosewheel steering. Extending the slats or activating engine anti-ice rises minimum idle N1 but otherwise doesn't affect "FADEC logic". A320 isn't difficult to fly in direct law - it evens feel livelier and trimming by wheel, C-172 style, felt quite fun, at least for me. Mind you, that was in the sim, I can't recall that my company's fleet ever suffered degradation into alternate law. A colleague of mine, flying in the ME, once had dual radalt failure. He claims that real aeroplane behaves even better in direct law than sim. Air/ground sensing on A320 controls much more than just ground spoilers and spoilers are armed after the final hi-lift devices config is set, anyway. Please be patient and wait for the report. Thank you.

[OFSO]

French newspaper "Le Figaro" quoted this evening on Catalan TV as stating accident was definitely caused by a sensor remaining covered following of work on aircraft, described as "grave error" by factory.

I have no idea as to whether Le Figaro have inside information or this is a conjecture expanded to a cause.

[OFSO]

Perpignan : un défaut de peinture à l'origine du crash


Thierry Vigoureux
24/01/2009 |
INFO FIGARO - Une panne des instruments de bord après la révision en atelier semble probable et Airbus vient d'envoyer un bulletin de sécurité à tous ses clients sur les vols de contrôle après révision.

http://www.lefigaro.fr/icones/coeur-.gif Les techniciens du Bureau d'Enquêtes et d'Analyses pour la sécurité de l'aviation civile (BEA), basé au Bourget, semblent avoir avancé sur le scénario de l'accident de l'Airbus A 320 survenu en mer au large de Perpignan le 27 novembre dernier (http://www.lefigaro.fr/actualite-france/2008/11/29/01016-20081129ARTFIG00109-a-l-equipage-n-a-pas-donne-l-alerte-.php). Sept personnes, des pilotes et des techniciens aéronautiques, avaient trouvé la mort.
Lors des opérations de peinture effectuées dans un atelier de Perpignan qui remettait l'avion loué à XL Airways Germany aux couleurs d'Air New Zealand, des capteurs sur le fuselage auraient été cachés par une couche de protection. Ce qui auraient rendu inefficaces les calculateurs et les commandes électriques de vol.Le déroulement de cet accident intriguait les experts car il était, théoriquement, impossible.
En approche finale avant d'atterrir à Perpignan, l'A 320 s'est cabré puis a décroché. Une manœuvre censée être impossible car les commandes électriques de vol de l'A 320 stabilisent automatiquement l'avion, éventuellement contre le gré du pilote. Les situations scabreuses sont donc impossibles. A moins que les sondes et les capteurs aérodynamiques situés sur les ailes et le fuselage n'aient pas rempli leurs rôles et n'aient pas alimenté en données les calculateurs de bord sur la vitesse, la pression, l'attitude de l'avion, etc. Les systèmes de sécurité intégrés aux commandes de vol deviennent alors inefficaces.

Scénario plausible


Reste à savoir pourquoi ces circuits de mesure doublés, voire triplés, n'ont pas fonctionné.Ce scénario est suffisamment plausible pour qu'Airbus ait envoyé hier à ses 218 compagnies aériennes clientes un bulletin de sécurité rédigé en collaboration avec le BEA à partir des premières informations tirées des enregistreurs de vol. Cette note, diffusée dans le monde entier, vise avant tout à éviter qu'un accident semblable ne se produise et recommande des mesures préventives comme le demande l'Organisation mondiale de l'aviation civile. C'est une garantie essentielle pour permettre à la sécurité dans le transport aérien de progresser.
L'enquête judiciaire ne doit pas interférer. Elle passe après l'enquête technique et s'efforcera plus tard de déterminer des responsabilités. Airbus met aussi en garde sur la conduite des vols de contrôle effectués après des opérations de maintenance, comme ce fut le cas à Perpignan.
L'avionneur rappelle les consignes sur les vols à basse vitesse qui ne doivent pas être effectués à basse altitude et donner lieu à un briefing spécifique.La presse néo-zéalandaise, alimentée la semaine dernière par des déclarations du procureur de Perpignan faisant état de données techniques incomplètes ou mal comprises, évoquait la possibilité d'une poussée soudaine des moteurs avant l'accident. Mais cette information ne peut être interprétée, faute d'être resituée dans la chronologie du vol.

[Fark'n'ell]

OFSO

Translation sil vous plait.

[Luap]

Google translation:

Perpignan: a failure to paint the cause of the crash


Thierry Vigoureux
24/01/2009 |
INFO FIGARO - A failure of on-board instrumentation after revision workshop seems likely and Airbus has just sent a security bulletin to all its customers on flights after revision control.

The technicians at the Bureau of Investigation and Analysis for the Safety of Civil Aviation (BEA), based on location, appear to have advanced on the scenario of the crash of the Airbus A 320 occurred at sea off Perpignan November 27 last. Seven people, pilots and aviation technicians, had died.
During the operations carried out in a paint shop Perpignan calling the aircraft leased to XL Airways Germany in the colors of Air New Zealand, sensors on the fuselage had been hidden by a layer of protection. What would make ineffective the computers and the electrical vol.Le course of this accident puzzled experts because it was theoretically impossible.
On final approach before landing at Perpignan, the A 320 reared then stalled. A maneuver meant to be impossible because the electrical flight of the A 320 automatically stabilize the plane, possibly against the will of the driver. Egregious situations are impossible. Unless the probes and sensors on aerodynamic wings and fuselage have not fulfilled their roles and are not supplied with data onboard on speed, pressure, the attitude of the aircraft, etc.. Security systems integrated with the flight controls become ineffective.

Plausible


It remains to know why these circuits measuring doubled or even tripled, not fonctionné.Ce scenario is plausible enough that Airbus had sent yesterday to its 218 airline customers a security bulletin written in collaboration with the BEA from Initial information from the flight recorders. The note, circulated throughout the world, is intended primarily to prevent a similar accident from happening and recommends preventive measures as requested by the World Organization for Civil Aviation. It is an essential guarantee for the security in air transport to grow.
The judicial inquiry should not interfere. It goes after the technical investigation and will try later to determine responsibility. Airbus also cautions about the conduct of flights made after control of maintenance operations, as was the case in Perpignan.
The manufacturer recalled the instructions on flights at low speed which should not be conducted at low altitude and give rise to a press briefing spécifique.La New zéalandaise, fueled last week by statements by the prosecutor Perpignan reporting data Technical incomplete or poorly understood, evoked the possibility of a surge engines before the accident. But this information can not be interpreted, if not viewed in the chronology of the flight.

[Admiral346]

That translation is so poor...

[GMDS]

On final approach before landing at Perpignan, the A 320 reared then stalled. A maneuver meant to be impossible because the electrical flight of the A 320 automatically stabilizes the plane, possibly against the will of the driver

This implies that if the "electrical flight" (what a crap term) is erroneous, for whatever reason, the stabilization might be erroneous as well, possibly against the will of the driver.

This quite sums up the design flaw of the Airbus system. Murphy said quite rightly that if something can go wrong, eventually it will. Even in a Bus. Therefore depriving the driver of the final authority is a serious flaw.

I don't know where atakacs got his information from:
I have numerously advocated for a big red "kill all automation, let me fly this" button and I have been told that it was indeed available...
I have yet to find that button, but it would make the Bus a safer equippment to fly.

[dudduddud]

I dont think you can take any stock in these automatically generated translations. 'Electric flight' is a term google translator came up with. Meanins and terms can be mixed up.

You should have seen the babel translator version :o

[HundredPercentPlease]

Quote:
I have numerously advocated for a big red "kill all automation, let me fly this" button and I have been told that it was indeed available...
I have yet to find that button, but it would make the Bus a safer equippment to fly.

I am no expert, but what about:

1: FAC 1+2 off. (Alternate law)

2: Gear down (Direct law).

[IcePack]

Having just re-converted back onto the bus. After 12 yes on boeing. I still can not understand how they could have flown around for so long without any problems only to have the machine do something un-controlable on approach.???

[Safety Concerns]

Before this thread ends up going in the ridiculous direction of Boeing/Airbus, Fly-by-wire/Manual control lets not forget one thing.

There has already been accidents due to this type of mistake and all were Boeings are far as I can remember. The aircraft could not be manually controlled due to erroneous air data readings.

So erroneous air data information is just that, erroneous. It will in all probability lead to tragedy and has no respect for aircraft manufacturer. Therefore the boeing/airbus, manual/automated nonsense is not required here.

[atakacs]

There has already been accidents due to this type of mistake and all were Boeings are far as I can remember. The aircraft could not be manually controlled due to erroneous air data readings.
Actually there was an A300 in Kenya (?) which crashed at takeoff because of erroneous stall warnings to the crew (although the exact cause of those bogus warnings where not established it was definitely sensor or computer related).
That being said most if not all "bad sensor" induced crashes where during night operation, in which case getting inexact readings from some or most instruments is obviously quite challenging (albeit survivable in most cases with the benefit of hindsight). Here they were flying with reasonably good visibility yet they still lost the aircraft. I can certainly foresee surprise and panic when the Bus decides to do something unexpected (this time because of possibly paint damaged sensors) but I am still convinced that there is no adequate takeover procedure for the pilot to regain control when things get out of hand. One can mention the A330 test flight that went bad and where the chief test pilot did not manage to recover in time because (among other factor, admittedly) he did not understand what the plane was doing or the TAM 320 where the crew was refused any kind of braking because the automation systems did not like what the pilot was doing. In both (and other cases) the pilots might have had a chance if they could quickly revert to a fully human controlled flight. I'm pretty sure this will be the case here too...

One might argue that the various automation built into the Airbus FWB systems did actually save the day more often than not by overriding the pilot and it is quite conceivably the case. But I would still be more reassured if there would be a quick way to get back full control of the plane and if the FWB pilots would be actually trained to take over when they don't understand what's going on (just remember the Flash Airline pilot whose only answer to increasing excessive bank angle was to revert to the autopilot... it was a 737 but it's NOT the attitude to have).

[All-Ex]

A Birgenair B757-225 crashed in 1996. Speed indications were wrong because of obstructed pitot tube. But back then problems started very early in the flight.

Narrative:
Flight ALW 301 departed Puerto Plata for a charter flight to Frankfurt via Gander and Berlin at 23:42 LT. At 80 knots on take-off the captain found out that his air speed indicator (ASI) wasn't working properly. The co-pilot's indicator seemed to work fine. While climbing through 4700 feet the captain's ASI read 350 knots (real speed was about 220kts); this resulted in an autopilot/autothrottle reaction to increase the pitch-up attitude and a power reduction in order to lower the airspeed. At that time the crew got 'Rudder ratio' and 'Mach airspeed' advisory warnings. Both pilots got confused when the co-pilot stated that his ASI read 200 knots decreasing while getting an excessive speed-warning, followed by a stick shaker warning. This led the pilots to believe that both ASIs were unreliable.
Finally realizing that they were losing speed and altitude they disconnected the autopilot (which, fed by the captain's faulty ASI, had reduced the speed close to the stall speed) and applied full thrust. At 23:47:17 an aural GPWS warning sounded. Eight seconds later the aircraft struck the ocean.
The incorrect ASI readings were possibly caused by an obstructed pitot tube, which had left uncovered for 3-4 days prior to this flight.

PROBABLE CAUSE: "The crew's failure to recognize the activation of the stick shaker as a warning of imminent entrance to the stall, and the failure of the crew to execute the procedures for recovery from the onset of loss of control."

[NigelOnDraft]

The Airbus Safety message text seems to have been removed (?) But from the Flight article, which I think fairly accurately reproduces what was said:It said during painting and maintenance it was important to protect all aerodynamic data sensors.

It has also said that tests such as low speed tests "must be performed at safe altitude and be preceded by a recall of basic rules as regards to minimum speeds and recovery actions".Might I suggest we do not think this is, as suggested above, exclusively applicable to "Static Ports". It might have been... but these are not the "sole" sensors.

I find the second paragraph more interesting... and possibly making comments such as:This quite sums up the design flaw of the Airbus system. Murphy said quite rightly that if something can go wrong, eventually it will. Even in a Bus. Therefore depriving the driver of the final authority is a serious flaw. I still can not understand how they could have flown around for so long without any problems only to have the machine do something un-controlable on approach.??? not relevant ;)

There are numerous types of sensor, and numerous versions of each sensor. We do not what, or how many, were affected and when. But the second para seems to be giving out some clues as to the conduct of the "tests", possibly when combined with some sensor errors :ooh:

NoD

[Safety Concerns]

well we can speculate about many different scenario's but won't know the facts until they are published.

I would agree though that under normal circumstances blocked/covered probes/ports should become apparent immediately.

Angle of attack probes though could be a different story.

[BOAC]

The aircraft (Boeing) could not be manually controlled due to erroneous air data readings. - I know not about the 777 (nor Airbus), but certainly up to that model ALL Boeings can ALWAYS be 'manully controlled' in that situation. It is not easy, by any means, due to misleading and confusing instrument readings, but it is something we practice in the simulator with success. There are specific Boeing procedures and settings for crews to help with this, and I would expect the AB to be the same.

IF the problem was a taped over static port, it must surely have shown itself earlier in the flight, so there should be discernable data? It would result in an increasing airspeed indication during descent which, I suppose, could have caused the auto system to reduce actual speed to compensate until Alpha Floor AoA was reached? As to why this may have caused loss of control, I know not - any AB folk to comment? I appreciate that the unexpected onset of TOGA could cause a huge pitch up but I thought the AB control system was designed to cope with that - unless of course it was being flown manually.

I have not read right back in the thread, but do we know the wx conditions prevailing around the crash site?

[Safety Concerns]

@BOAC

you are of course correct and I could have worded it better. My point though was that it really makes no difference whether it was a digital aircraft or analogue. Erroneous air data is a difficult situation to handle.

I do not subscribe to this Boeing manual control or Airbus automated control nonsense. Both manufacturers aircraft are inherently safe.

[GMDS]

I truly understand the uproar of the Airbus lobby, them therefore bringing up the (somewhat childish) "but it can happen and happened to Boeing too....."
This is true and it also lead to accidents, yes.

Fact is simply, that in a sensor malfunction with erroneous data and electronic flight signals, the one still allows to be flown with the good old a$$ relying on attitude, RPM, sound and so forth. The other one does not, see Qantas incident.

For my part, I simply and sincerely prefer the earlier, even if the systems are less elaborated and sophisticated and those marvels might have saved one or two. This however applies just as much to the other system (beeing childish myself). And remember: You do not HAVE to disconnect everything, but at least there you CAN.

[Fundi-Ya-Ndege]

It does always seem to go to the Boeing vs Airbus thing but there have been several losses or near losses of 737's with rudder hard over problems and they were not fly by wire issues but hydro-mechanical (I'm sure someone will be able to correct this assumption for me :}) and no amount of manual reversion would have saved them as the solution was in fact not to pull but push in order to get better response from the ailerons ( I think that makes sense but see above proviso..... )
Any system can and will be subject to murphy's law and having done more than 5000 hours on the bus I am pretty satisfied that it will look after me.

[Ptkay]

In the fever of A vs. B argument you seem to forget, that the most expensive and sophisticated AC in the world was downed by a sensor error as well...

A rather expensive experience at 2 billion dollar price tag.

No system is 100% immune against human error and simple, stupid negligence...

[IcePack]

About 13 years ago an A320 became very difficult to control on a go-around at Hong Kong. Something to do with the Flaps locked in the full position but the flap lever in posn 3. If I am right this situation can not occur these days as the control laws in effect take their que from actual flap position NOT lever position. Now what could paint/tape do to the flap position sensor ?
As I've said before the results of the investigation will be very interesting to read. As for Boeing/Airbus they are both a/c so if you set an sensible attitude and set a sensible thrust setting you will get a sensible flight profile. But in normal law will the Airbus allow you to set a sensible attitude & thrust, if the flight control computers are getting erroneous data. I know you can in the Boeing (75/76) but as am just back on the Airbus am not convinced you could. But then again I may be totaly wrong.;)

[Knackered Nigel]

Firstly, I am not one to speculate, hence rarely post on this forum. However I do find the continous "Manual vs Auto" "Boeing vs Airbus" argument somewhat tedious. No aircraft is perfect, they all require the crew to be trained thoroughly and to know the procedures to be carried out should failures occur.

Of course, as I fly the 'bus I do feel somewhat defensive, but not to the extent of thinking one fundamentally safer than the other (give me Normal Law anyday :) )

An airbus can be flown manually either in Normal Law, or if things go wrong, Alternate and then Direct. They all offer some protections, Normal Law giving you the ability to pull back full stick and bank fully without fear of losing control. A fabulous attribute, surely.

Now on the subject of Unreliable Air Data, if that should happen to be a factor here, no aircraft can cope with it. It is up to the pilots to notice the problem and then carry out Memory Drills for datum pitch and power settings.

I did this just the other day in the sim as it happens as part of my recurrent check. Very odd and disturbing to see conflicting readouts on PFDs, but once you have noticed a discrepancy, you are halfway there to staying safe.

Whatever the cause of the crash, it is a great loss for the families and friends involved. Let's all wait for the official results.

[hetfield]

Maybe we can concentrate the discussion to the following question:

Which airplane(s) will be out of control if pitot/static ports, AoA-vanes are blocked/jammed.

Concerning 727, A300 I know the answer. A320/340 and the qantas incident I don't recall.

[BEagle]

Angle of attack probes though could be a different story.

Yes, I've had this on the ancient coal-fired 4-jets I used to fly for HMFC.

No-one except us god-like Qualified Flying Instructors was normally allowed to practise flapless or slatless approaches. One day, I was flying a practice flapless approach in an aged old VC10K when all of a sudden, at around 800 ft agl, the stall warning system suddenly operated the stick pusher....

Fortunately I was able to overcome the large nose down pitching moment, executed a go-around, landed off the next approach and threw the old wreck at the maintenance people. Or 'engineeers' as they liked to call themselves.

They found a couple of 'interesting' facts:

It had been stuck in some god-forsaken desert $hithole supporting Bliar's wars for some weeks and the AoA probe bearing was gummed up with sand and crap, so that when it moved jerkily on the approach, it triggered a false 'phase advance' signal (spurious detection of a rapid increase of AoA).

The 'lift rate modifier' box (which corrects the stall protection system trigger AoA values for configuration) had NEVER been connected since BWoS allegedly re-built the old heap a decade or so earlier - the wires were neatly tucked behind the associated black box, but had never actually been connected.

http://i14.photobucket.com/albums/a341/nw969/Internet/zxzxz.jpg
Post-maintenance test flights could often prove most interesting, which is why very few of us were cleared to conduct them. But as long as you remembered the basics and didn't rush into blind checklist reading, things were normally OK.

[forget]

........... and threw the old wreck at the maintenance people. Or 'engineers' as they liked to call themselves.

That could have been very nasty. Did you ever look into which particular (non engineer) sky god carried out the acceptance test flight? Or who wrote the acceptance check list? That would have been a useful activity.

[Dani]

It was rather obvious that this accident has something to do with the air data sensors. I mentioned it in the very beginning

Click here (http://www.pprune.org/4558678-post44.html)

But noone believed me...

It is very well possible that the air data error only occured in a special set of configuration and was not yet dangerous in the beginning of the flight. Only when they pulled the levers or pushed the buttons, something went wrong. Let's see what the specialists will find out!

Dani

[BEagle]

The unconnected Lift Rate Modifier had gone undetected for many years - it was only when the stick pusher went off that the error was found.....

The real problem was the sticky AOA probe and the fact that aircraft were rarely flown to the limits they once were when airframes were rotated between training and operational use.

Various other horrors were found on other aircraft - mainly down to poor conversion by BWoS, not as a result of routine maintenance. For example, when refuelling from other aircraft, we used to dump the stall protection system to prevent spurious warnings or idents at AAR speeds caused by airflow disturbance. But one VC10K was found to have NEVER had a serviceable stall dump system; the pin in the linkage had never been fitted as corrosion in the locating hole proved only too clearly.

An old BOAC teaspoon was also found floating about in the electrical bay - it had been there throughout the aircraft's entire service with Gulf Air after they bought it from BOAC - and it had then been rebuilt by BWoS for the RAF....:hmm:

But the A320 accident has yet to be explained. Back now to the thread, I hope!

[UNCTUOUS]

It said during painting and maintenance it was important to protect all aerodynamic data sensors.

It has also said that tests such as low speed tests "must be performed at safe altitude and be preceded by a recall of basic rules as regards to minimum speeds and recovery actions".

When trapped water in a static system freezes during flight, above that freeze altitude the ASI will underread (and below that height it will overread - dangerous wrt (to) stall speed). Altimeters may freeze and VSI will......

Of course it all depends upon how many static ports there are - and how they're plumbed in to air data.....

[GMDS]

Gentlemen, you are missing the point and the arguments.
This is not a slagging match A vs B!
Adhering to the thread this is about an accident of a Airbus.

Sensors and computers will always be prone to failures or mishandling. My criticism is that with the Airbus philosophy, a failure leading to erroneous electronic inputs or commands is not easy enough to counter. We know this aircraft pitched erroneously before crashing. We all assume that this was not done by deliberate pilot inputs.

Many assume that it has been done by electronic inputs, or at least caused by such. The reason has to be determined. We also know that Airbus technology does only allow a override of these electronic inputs in special circumstances (alt or dir law). To reach such a condition, there needs to be some switching. With ADIRU faults there is a procedure (CB pulling) which is not suited as a emergency procedure, no CB pulling/switching is designed for such operations, therfore it is not suited for events like Qantas experienced.

To reach dir law, with switching of PRIMs or SECs, there is no ECAM or other procedure determined as how to reach such status in an emergency, therfore again it is not suited for an emergency situation.

Any other aircraft will allow a pilot intervention, with some force and by switching off the AP/AT and such a procedure IS suited for a emergency situation, as it is a natural, trained and instant manoever.

Airbus might come up with some drill or memory items to counter erroneous, rapid inputs of electronic flight, and I would warmly welcome such procedures. But as long as there is only CB pulling or overhead switching, I will uphold my criticism of the Airbus system as it remains prone to catastrophies for such situation, as remote they may be and as much they might be induced by non Airbus systems/outside human error.

The pilots should always be armed with a direct, instant and easy intervention capability.
That is my criticism.

[hetfield]

@GMDS

Spot on! I totally agree with you. Have flown 340 and 320, now on A300 I feel much better about that particular issue.

regards

[captplaystation]

GMDS,
As a confirmed Boeing luddite I find that info disquieting but not entirely surprising. :ooh:
I knew there had to be a good reason to sit in uncomfortable seats in a cramped noisy little space, now I know why. :rolleyes:

[atakacs]

GMDS

Excellent post - my view exactly


The pilots should always be armed with a direct, instant and easy intervention capability.

I'm afraid that the ultimate answer by Airbus, although not worded in those exact terms, is "we know better, it is actually a feature of the aircraft not to let you take over"...

That's possibly as key point where they "philosophically" differ from Boeing.

[Safety Concerns]

Sorry the last few arguments are technically flawed.

Both Boeing and Airbus build inherently safe aircraft. But the type of technology used dictates the type of approach to be taken by the flight crew as problems will manifest themselves in different ways due to different technologies.

Safety statistics do not support any of your comments about a potentially flawed philosophy or the need for humans to be given more control over an "automated" process.

The direction this thread is taking actually highlights nothing more than a human reluctance to accept change and does not advance the discussion on the Excel tragedy.

[DC-ATE]

Rubbish. Even the Space Shuttle can be flown manually if need be.

[Safety Concerns]

@dc-ate someone has already said it but it holds true. This thread is showing the holes in peoples knowledge and nothing else.

An Airbus can be flown manually and the whole argument has no place here in a discussion about a dreadful accident.

Once you are able to distinguish between fact and fiction come back and say something sensible. Otherwise your post reflects your own knowledge levels.

[BOAC]

a human reluctance to accept change - going slightly 'off thread' here (and NOT directed at Airbus), but there is an understandable reluctance to embrace 'change' at any cost. The B2 accident referred to before shows what can happen when sensors and chips have such authority as to render the a/c unflyable in a failure mode. It is not "the need for humans to be given more control over an automated" process" so much as "the need for humans to be given..." (while pilots remain in cockpits) a way to take over when things don't work as they should, allied to the training to fully understand what the system is doing. I have for a long time believed that failure to provide the latter was a key factor in the early days of the 'modern' Airbus and certainly caused a few crashes. Until we have infallible systems there is going to be the need for pilots to be able to revert to the old-fashioned way of doing it - assuming pilots are still trained to do that............................. Anything which prevents raw input producing raw control, albeit without all the bells and whistles, is dangerous.

[DC-ATE]

Thank you, I have returned.

Any time you take away ANY portion of control of a human-operated flying device, you increase the odds of an unsuccessful outcome in the event of an emergency.

[lomapaseo]

I must have missed something.

I never suspected they was a question about whether it could be flown manually but the issue was that you do need recognition and reaction time and therfore a safe altitude.

I could be confused but wasn't this the issue?

[Safety Concerns]

I maintain that this discussion is irrelevant and not related to this awful situation.

Aeroperu 603 says it all. Now please get back to topic which is what actually happened with the Excel aircraft.

[atakacs]

I maintain that this discussion is irrelevant and not related to this awful situation.

Aeroperu 603 says it all. Now please get back to topic which is what actually happened with the Excel aircraft.

Aeroperu was very different because it was a night fly over sea. The pilot never fully understood that their instruments where not working correctly (they might / should have but it wasn't obvious without any outside reference).

Here is was daylight. There is absolutely no doubt that the crew realized immediately that the plane was not behaving as expected. My completely uninformed theory is that they actually fought against the automation and lost the "battle". I would go further and pretend that they might have had a better chance if they could quickly and simply kill all automation, had adequate training to do so and hand fly the beast...

Obviously this might or might not be confirmed in the final report... as such this discussion is perfectly on topic (as much as my understanding of PPRunE goes, of course...)

[Knackered Nigel]

GMDS - I disagree with the core of your statements.

To gain control of the Airbus in an unreliable airspeed/data scenario (ie pitot or static ports/sensor fault) you...

Disconnect autopilot (if engaged) by pressing red button on sidestick
Switch off flight directors
Disconnect autothrust press button on side of thrust levers
Pitch and Power to memory drill datums

It won't pitch up erroneously in manual flight.

How do other aircraft differ?

I am in no way making inferences about the actions of the crew in this scenario, just highlighting that the Airbus is as safe as any other jet with unreliable air data.

[IcePack]

KN. See my prev. Post yes it can in normal law if the sensors give erroneous info to the flt control computers. You need direct law for direct "manual" flt. That is why this tragic accident possibly happened if one is Reading behind the lines of the airbus release.

[NigelOnDraft]

Knackered Nigel

It won't pitch up erroneously in manual flight.
I disagree I'm afraid... and I fly the thing as well ;)

A lot of posters are getting hung up on the AP... which in the Airbus is a fairly dumb thing, and subject to the same Flt Control Laws as we are in Manual Flying...

If we limit ourselves to Normal Law, then the Airbus, with/without AP, has defined Pitch, Roll and AoA limits. If it determines it is exceeding those, then it will apply controls to try and get within those limits, whether AP is in or out e.g. if it (thinks) is at 70AoB to the left, it will roll right. Trouble is if it was in, say, a 45AoB turn to the right, but thought it was 90AoB to the left, it will roll to 75AoB right, and try to roll more :{

Of course, the design of multiple IRs / sensors, and degraded Flt Control modes as things fail, is designed to prevent the scenario above occurring. However, it did in the QF72 incident, where, as I understand it, in Manual Flight it "pitched down hard" to reduce a perceived excessive AoA.

Quite where, even if, this fits in to this accident we have yet to find out... and whether the test schedule requirements, with/without known sensor errors / failures, created the final loss of control....

AFAIK the 777 has had similar control "issues" due faulty sensors... although full control inputs are supposed to "override" any protections... ?

NoD

[ChristiaanJ]

Any time you take away ANY portion of control of a human-operated flying device, you increase the odds of an unsuccessful outcome in the event of an emergency.Maybe....
You also increase the odds of an imbecile "taking control" and crashing the "human-operated flying device"....
The Habsheim crash is the textbook example.

As an ancient aeronautical engineer, not a PF, I'm in favour of the "boing", then stick shaker, then stick pusher, all known and anticipated, rather than having the aircraft decide for you what it thinks is best ... But I may be wrong.

CJ

[daikilo]

I think the Airbus telex was intended to remind all concerned that procedures should be followed, no matter the outcome of this investigation.

[OilCan]

Knakered Nigel

It won't pitch up erroneously in manual flight.


I also disagree I'm afraid....even a manual aircraft can pitch up erroneously in manual flight, whether imbecile induced or a broken bell crank/lever/sproket/cable/turnbuckle/split pin or floo floo valve thingy.!!! (take your pick)

I'm intrigued by the 'computer/sensor' debate but presumably they only send the push/pull intention, it requires something more substantial to actually alter the bernoullies.:8

Sometimes when we make complicated things, we expect complicated problems.....buts its the simple things we forget.:hmm:

[stillalbatross]

The pilots should always be armed with a direct, instant and easy intervention capability.
That is my criticism.

Completely agree, on the 737 for instance, when the aircraft is about to throw in uncommanded rudder and roll on its back as it does time and again there should be an additional set of pedals to counter it..............

[atakacs]

I think the Airbus telex was intended to remind all concerned that procedures should be followed, no matter the outcome of this investigation.
My take is that any informed reader can infer a lot more than that from this "telex". It's by no way the final report but you can bet that the root cause was some sensor failure post paint job and some procedures not followed...

Will see in 18 months... ;)

[GMDS]

Completely agree, on the 737 for instance, when the aircraft is about to throw in uncommanded rudder and roll on its back as it does time and again there should be an additional set of pedals to counter it..............

I agree, but there you go yourself with the A vs B slagging.
The rudder design of the 737 proved to be a serious flaw and, i believe, has been corrected. Therefore I would have hoped that Airbus might consider its design not adequate enough (i.e. Qantas incident and eventually this one as well) and provide us with a solution. I don't know how easy it would be.

Let's face it, the same faults on a, say, 777 could have been overcome with switching off AP/AT and some force. This is instinctive and instantanoeus. I disagree with the presumption that this is possible with a Airbus. For that I say again you would need some overhead PRIM/SEC switching. There is no procedure for that and overhead switchings is not instinctive and instantaneous.

Pointing at other aircraft designs, failures and subsequent accidents does in no way let anyone off the hook with their own design. If weaknesses are detected, reported and therefore known, operators, crew and passengers have a right to expect the manufacturor to come up with a viable and flyable solution. Bulletins and accident reports may be a lead to that, but they are NOT the required solutions.

For such events and for the average pilots (that would be me), the situation in an Airbus and having to expect the unexpected, today this design lacks the as I said instinctive and instantaneous possiblity of intervention.

[OFSO]

That fine science fiction writer, Robert A. Heinlein, wrote in "The Moon's A Harsh Mistress" of the utter stupidity of controlling everything from transport to environment to writing paychecks using one large computer system, with no manual reversion or as he called it, the possibility of "jury-rigging" while a problem was solved: because "if it can go wrong, it will".

He'd have been interested in this present discussion.

R

[HotDog]

atakacs,
I do enjoy your comments on various subjects before the publication of the official findings.:rolleyes:

The most accurate one so far is;Will see in 18 months... :ok:

[Smilin_Ed]

If we always waited for the final report to comment, there would be no PPRuNe. :}

[Capcom]

Soooooo .. after 565 posts it comes down to this:-
.
How do the Airbii keepers of the logic :E ensure in future that the pilot/s can override the automation when, the automation is known to be taking the day off i.e.
.
... visual reference and other clues like …. errrm …. geez :suspect: .. ****e … we are slow (heaps less airframe slipstream noise), or :ooh: ****e, we are stuck to the cabin roof … :eek:
.
... for whatever reason i.e. taped over sensors, or an air data reference unit hissy ..... GIVEN that …
.
OBVIOUSLY, following on from that …. and ... CONVERSLY …
.
.... be smart enough to know when the automation should not allow an "Imbecile" :ooh: (previous poster description) to override automation went it does know best?!?!?!? … if in fact it REALLY does know better??? :{
.
http://www.improvresourcecenter.com/mb/images/smilies/popcorn.gif

[TeachMe]

I think some posters here have hinted at a question that would need to be answered to assess the automation and philosophy of Airbus, and that is:

'How may accidents has the automation and design philosophy prevented?'

Unfortunately that is obviously a question that can never be answered, therefore it is hard to make a good argument for or against that automation. Really, would a big red override button have saved this plane, but have resulted in two other accidents? We will never know.

[DC-ATE]

Can those that are in favor of all this automation explain what the purpose of the pilot is?

[lomapaseo]

Can those that are in favor of all this automation explain what the purpose of the pilot is?

to feed the dog

[GearDown&Locked]

Opposite argument: what benefits would bring in terms of safety the existence of that big red "Cessna 172 law" button that would silence all the automation? How many accidents would such device had prevented so far.

Suddenly at the mere hiccup of an ECAM screen every Aibus/B777/whatever Captain would be extremely tempted to press it, for whatever reason, probably with a wider range of results, good or bad. Would any Captain want that much responsibility (by pressing said button) on his/her shoulders?

[On Guard]

Gear Down

Why should we be scared of pressing a big red button that merely gives us control of an a/c. Back when we flew GA we were in big red button mode all the time.

I feel some today are being over awed by all the automation, at the end of the day they are aircraft and simple to fly. If you can't fly them then you need to question your position.

Some great advice I was given as a F/O was to learn how to operate the aircraft in every mode, automated or not, and to push myself while I was an F/O so that when I moved to command the a/c posed no loading upon me, allowing me to manage and observe.

[glad rag]

Can those that are in favor of all this automation explain what the purpose of the pilot is?

To ditch the aircraft of course!:}:}

[ChristiaanJ]

...pressing a big red button that merely gives us control of an a/c.At Habsheim, that 'big red button' would simply have caused the aircraft to do a wing-over into a big fireball.

As they say at school: "discuss".

"merely..." ???
Do you really want the aircraft dumped in your lap in Cessna 152 mode when you're already knee-deep in the soft brown matter?

I was hoping for a serious discussion rather than the usual A vs B session.

As an engineer, I have no axe to grind. I was just hoping for some intelligent input.

CJ

[Smilin_Ed]

Would any Captain want that much responsibility (by pressing said button) on his/her shoulders?Yes he would, provided the "Cessna 172 Mode" is flyable to a reasonable degree.

[CONF iture]

At Habsheim, that 'big red button' would simply have caused the aircraft to do a wing-over into a big fireball
ChristiaanJ, you will have to justify how you can advance such a statement ?


An Airbus can be flown manually and the whole argument has no place here in a discussion about a dreadful accident
There is no question about that, but QF72 also proved that a protection can take over a nicely manually flown airbus and do the mess it did ...

[framer]

Would any Captain want that much responsibility (by pressing said button) on his/her shoulders?

Geez thats a sign of the times isn't it?? It's an aircraft, the responsibility is already on the Captains shoulders....he/she just wants control so they can meet said responsibilities. I have flown with people who get lost in the automation while descending below 5000ft, any pilot worth their salt recognises it, disconnects everything and flys the bloody thing.
(None of this is in reference to the German crew, just to the above quote)

[OilCan]

Would any Captain want that much responsibility (by pressing said button) on his/her shoulders?

...so whos responsibility is it if he doesn't??:confused:

[GMDS]

@ TeachMe

'How may accidents has the automation and design philosophy prevented?'

Unfortunately that is obviously a question that can never be answered, therefore it is hard to make a good argument for or against that automation. Really, would a big red override button have saved this plane, but have resulted in two other accidents? We will never know.

Well, there is such possibility (allthough not a button) on the fly by wire 777. Now look at it's record. There has been no incident where the automatic overriding capability was used and as a consequence a situation was worsened. On the other hand the QF72 incident could be directly linked to the automation giving wrong inputs and the pilot not beeing able to intervene fast enough due to absence of such feature.

Hypothetical arguments as yours are very delicate. As you said, we might never know. But real incidents with findings exist and they stay awkwardly in the room to cry for a SOLUTION.

[Smilin_Ed]

With the FBW system having gone berserk, would the "Big Red Button" actually work. After all, it would have to be part of the system.:confused:

[Clandestino]

One thing that's sure is that it wasn't trainning, but rather post-maintenance test flight. Sud747 or moderators, please change the topic title accordingly, thank you.

There was no mention in media that ATC was told that anything out of the ordinary happened on the flight, it wasn't cut short, there was no communication of changed intentions, so whatever happened, manifested itself suddenly and unexpectedly on approach and that's not something you'd see with ports taped over or probes blocked.

There was a leak from the state prosecutor (although this might be mistranslation and fellow might actually be the investigating judge) that there was pitchup, surge in power, stall and crash. Some have used this statement by complete aviation amateur to theorise about FBW Airbus protections gone awry. Well the only protection that gives you pitch-up is high-speed protection and I have reasons to believe that the aeroplane was nowhere near its Vmo of 350 kt on DME arc. Protections are also designed to shut themselves off if there are discrepancies between all three air data or inertial reference sensors. There was also a question of pitch-power coupling in A320. In normal law, there's always ample and timely application of autotrim to counter any pitch changes with power, whether flying manually or with AP engaged. If you're out of normal law, alpha floor is deactivated i.e. there's no automatic TOGA power to fight with.

However, we still don't know what happened and everything and anything I've written may or may not be related to the accident and for the time being, this accident absolutely cannot be used as an argument to move Airbus approach to flight controls and automation in any direction.

If you're reffering to some old accident, please check out Aviation Safety Network (http://aviation-safety.net/index.php) and acquaint yourself with the facts about it. There are database entries for each and every accident and significant incident that happened to transport category aeroplane from 1943 onwards, FBW Airbi included. I'd especially recommend the site to PPRuNers peppering their posts with "QF72" - it might help them include "MH124" into their vocabulary. And while browsing through the reports, bear in mind that it is not the responsibility of the accident investigators to answer to a question "why did it happen?" What they're telling us is what happened, how it happened and what we have to do to prevent it from reccuring. They never, ever blamed anyone or anything.

[TheShadow]

Well the only protection that gives you pitch-up is high-speed protection and I have reasons to believe that the aeroplane was nowhere near its Vmo of 350 kt on DME arc. Protections are also designed to shut themselves off if there are discrepancies between all three air data or inertial reference sensors.
.
All on here would be surprised by how quickly the IAS winds back to zero in the climb, once water freezes in the static lines. Similarly, how very quickly it winds UP after the aircraft descends below the height at which it freezes and blocks static pressure changes reaching the ADIRU's, In fact, does it even need to freeze? Maybe water can just quickly flow to and collect at a low-point due to the attitude change of a descent/config change inducing a flow and a blockage.
.
Now I'm guessing that the A320 doesn't have independent static pressure line systems for each of its ADIRU's - so there'd be an effect upon all threeADIRU's and no shut-off of protections per:
Protections are also designed to shut themselves off if there are discrepancies between all three air data or inertial reference sensors.

So you have a rapidly increasing IAS in the approach/descent sensed by all three ADIRUs and it generates a programmed response of a rapid pitchup and power increase...... into an aerodynamic stall/spin.
.
Just a theory but........ any arguments against the logic and feasibility?
.
Maintenance => aircraft repaint and/or aircraft wash => water in static system......... => freezes at height (maybe during system checks on pressn system).

[TheShadow]

from this link (http://www.aaiu.ie/upload/general/4703-0.pdf)
.
Incident: Boeing 747-200, N520UP, Dublin Airport,12 May 2000: Report No 2004-004
.
6 February 2004

SYNOPSIS

The aircraft took off from Dublin Airport for a check flight following the completion of C check maintenance at Team FLS. After take-off, significant airframe vibration was encountered. The crew then deduced that both airspeed indicators were under-reading significantly. Following declaration of an emergency, and trouble-shooting by the crew off the east coast of Ireland, the aircraft returned safely to Dublin. After landing it was discovered that the flap system had suffered damage. It was found that the static drain ports in the Avionics and Electrical (A&E) bay, connected to both the Captains and the First Officers instruments, were left open after maintenance. This resulted in both airspeed indicators under-reading by a significant amount.
.

[PBY]

Quote:
Well the only protection that gives you pitch-up is high-speed protection and I have reasons to believe that the aeroplane was nowhere near its Vmo of 350 kt on DME arc. Protections are also designed to shut themselves off if there are discrepancies between all three air data or inertial reference sensors.

Another protection that gives you pitch up, even though as a byproduct, is if you are close to stall and the protection gives you full power. With the engines at full power and slow speed, you will get a pitch up. Even though the alpha floor is not designed to give you pitch up, the pitch up at very slow speed might not be overrideable.

[camel]

excuse my ignorance ....but is there no kind of stick pusher on the airboos?
or something similar ?

i understand its designed so that it 'cant' stall ...but what happens if it actually does get into a stall due to some combination of windshear/failures/errors etc? will the 'systems' reduce the angle of attack ..wait ..and then add power ?

[Dysag]

You mean a mechanical device to push the sidestick to tell the computer what the pusher/shaker wants to do?

[PBY]

As far as I know (and I study the airbus manuals regularly), there is no mentioning of any stick pusher. The idea behind an airbus is, that it cannot stall (?!). So why should they design something against a situation, that cannot happen? (not that I myself belief, that the aircraft cannot stall).

[lomapaseo]

As far as I know (and I study the airbus manuals regularly), there is no mentioning of any stick pusher. The idea behind an airbus is, that it cannot stall (?!). So why should they design something against a situation, that cannot happen? (not that I myself belief, that the aircraft cannot stall).

I also believe that an Airbus can stall, when it's computers and the pilots are not in sync. So I agree with you that a stick pusher would be useless in that case since it would likely be out of the loop as well.

[NigelOnDraft]

but is there no kind of stick pusher on the airboos?
or something similar ?There is... (in Normal Law). You cannot fly it at greater Alpha than Alpha Max... so the "stick pusher" is there in software.

See QF72 for this coming into effect - aircraft "percieves" it is at Alpha far in excesss of Alpha max, and pushes hard to reduce Alpha...

NoD

[Fargoo]

excuse my ignorance ....but is there no kind of stick pusher on the airboos?
or something similar ?

No stick pusher or shaker on the A320 , the aircraft will repeatedly shout "Stall,Stall" at you though.

[airfoilmod]

Why ? To rub salt in the wound? Would I PA to the back... "Stall......

If FBW can't fix it, and PF (or P2) aren't equipped to, is it a cruel joke played by some writer of SW ?

AF

[NigelOnDraft]

No stick pusher or shaker on the A320 , the aircraft will repeatedly shout "Stall,Stall" at you thoughTrue... but can only get to this point in Altn/Direct Law. Normal as above should prevent getting to this point...

Why ? To rub salt in the wound? Would I PA to the back... "Stall......Well, rather like a Stall Warner in a C152 I would think :ok:

NoD

[Clandestino]

Seemingly I'll have to elaborate on Airbus protections. The guess that a320 doesn't have independent static pressure line systems for each of its ADIRU's is utterly wrong - they're completely independent, units 1 and 2 using signals from two ADMs each, one for left , one for right static port. ADIRU 3 uses one ADM in duct connecting left and right stby ports. When I wrote that the only protection that pitches nose up is high speed protection, some readers interpreted it as a severe pitch-up, which it is not. It's very gentle (with its limit of 1.75g unlikely to be ever achieved) and it turns off as soon as speed is 349kt. If you hold the stick against the forward stop, it will maintain a couple knots above Vno.

There's absolutely no programmed response of a rapid pitchup and power increase
in any of the A320 protections. Rapid increase of power called alpha-floor is triggered by FAC calculating that aircraft has reached high AoA. If the aeroplane is near its Vmo, it cannot enter the alpha-floor or, as G-limit is reached at AoA well bellow one needed for A-floor activation.

As for "gimme big red button so I can fly it out myself" brigade, protections are based on comparing data from all three ADIRUS. All three agree - fine. One fails, other two agree - fine. Two agree, third doesn't - still fine as it's outvoted. If one fails, two disagree or all three disagree - protections are off and you're on your own, the FBW has pressed the big red button for you and now your stick commands aileron displacement in roll and you might still have G-command in pitch or you have direct stick-to-elevators-displacement. Now you can stall the aeroplane, roll it on its back, overspeed it, perhaps even over-G it, whatever you choose to do or let the aeroplane do through sheer stick incompetence. As long as things work as designed, there is no way that protection can throw you in extreme attitude believing that it's saving the day. And what if they don't? We'll have to wait for ATSB to have its final say on QF72, the first recorded instance of faulty AoA signal not getting outvoted - in twenty years of FBW Airbi operations.

[lomapaseo]

Clandestino

Thank you:ok:

[Smilin_Ed]

Clandestino: In the event the voting process goes haywire, is there a way to manually get to the point where the pilot(s) have the full control as you describe when you have all three units disagreeing? :confused:

[SIDSTAR]

Clandestino,

System design very well explained except for the case where two similar but erroneous inputs are sensed by the ADRs (from Pitot/Static system). In such a case, the aircraft doesn't know that it's being fed inaccurate speed information and will try to follow the erroneous signals believing that the voting process is disregarding the "outlier" (quaint Airbus terminology) signal which happens to be the only valid one.

In the sim I have seen pilots become totally confused in level flight at a safe altitude when faced with apparently conflicting information on speed. To be fair to Airbus, they do have that "big red button" - Disconnect the automation and fly the memory pitch/power values. The real problem is in being able to recognise the fact that you have a problem. How I'd react if all that happened as I was turning base after an uneventful(?) 90 minute flight, I'd rather not speculate.

In the Excel case, it seems apparent that whatever happened, it was so unexpected as to take the crew completely by surprise.

Is there any information on the A320 experience levels of the two Excel pilots and were they trained for test flying something as complex as the 320?

[Knackered Nigel]

Smilin_Ed...

Attitude from IRS.. so if all 3 ADR data unreliable or suspect, use pitch/power datums in manual flight. Turn off 2 of 3 adrs (1 retains stall warning function). Use datum settings to fly climb/cruise/descent/approach profile to land somewhere.

[KRviator]

Chaps, what if we're looking at this the wrong way?

The media (Terrible source, I know :rolleyes: )has reported both a "Surge in power" and also a "Power Surge". We all seem to be assuming they are referring to the same event. But what if they aren't? What if the "Power Surge" is referring to a genuine electrical spike of some kind?

Does anyone have any input as to how the systems on the Airbus (OR Boeing for that matter) tolerate such a power spike, or what happens if they don't tolerate it?

Obviously everything is designed to withstand a lightning strike so something has gone terribly wrong in that case, but it has anyway, hasn't it?

Just a thought...

[camel]

NOD and others,thanks for the replies.

in theory then ,if you are flying a dme arc ,and the a/c gives you a sudden unexpected 'stall stall' warning whilst manouvering to stay on the arc (in a turn) what would be the correct recovery ? for each of the the different laws u were flying in ?

give it a couple of seconds to sort itself out ..and see what it does ...or disconnect everything and fly yourself out of it ?

[NigelOnDraft]

camel... Difficult to say... there is a drill, much as any aircraft:

Full Power
Reduce Back Pressure / Attitude
Roll Wings level
....
However, if it occurs when in Normal Law then something has failed... so maybe that failure also leads to the Stall Warning.

In practice, you will have to assess the Flt Conditions and decide if it could be "real", or whether is is spurious. As with a PPL Stall lesson, there are other symptoms of the stall (attitude, speed, power) that should help you decide. Default is "real" of course, but how long do you push for / maintain full power ?

Woolly answer, sorry ;)

NoD

[HotDog]

Does anyone have any input as to how the systems on the Airbus (OR Boeing for that matter) tolerate such a power spike, or what happens if they don't tolerate it?

Not familiar with Airbus systems but possibly not dissimilar to B747 Electrical systems.

The main generator voltage output is controlled by a regulator contained in the individual generator control units.

A sensing circuit continually measures the generator output voltage and informs the regulator as to how much energy should be applied to the generator field to maintain the proper output.

Excitation faults, generator differential faults, open phase faults, difference current faults, speed faults, synch bus faults will activate appropriate actions to protect associated load circuits.

[Obie]

There is a stall warning and a stall recovery procedure on the A320, Camel.

So, what does that tell you, Matey?

[camel]

Obie

thanks for the info ...not feeling hungry right now so.. have a nice weekend.

[aguadalte]

Cessna 172 Mode
Quote:
Would any Captain want that much responsibility (by pressing said button) on his/her shoulders?
Yes he would, provided the "Cessna 172 Mode" is flyable to a reasonable degree.

That's something that could easily be done through the instinctive disconnection push button installed on the side-stick, making it work this way: Once you press it one time, it disconnects the AP; the second time, you stop the "cavalry charge"; if you keep it pressed, you get your priority...and you could get your Alternate Law 1 too...(and have real control of your aircraft, without loosing a great deal of protections, but to the extent, that you can override them!).
Once you're in control of your bird, and have solved your problem, you could select your Auto-Pilot ON again, and regain your Normal Law capability :8(provided required conditions are still met.)
Simple, easy and pilot friendly.:E

Fly Safe

[Clandestino]

What is known, so far, is that the aeroplane crashed as it was returning from acceptance test flight and that's it. Everything else is uncertain. We don't know if it stalled, whether it pitched up and what was the active control law before the crash.


There is a stall warning and a stall recovery procedure on the A320

Stall warning is available in alternate and direct law, when there's no alpha-prot to stop the aeroplane from stalling. However it is possible to get false stall warning in normal law, if AoA probe is damaged. I'm not sure if this FCOM warning can be interpreted as "single (out of three) damaged AoA probe can cause false stall warning", but if it can, it may imply that voting rules are not the same for AoA and speed/attitude. QF72 final report will be very, very interesting reading indeed.

Procedure commonly refered as stall recovery (full power, decrease pitch, wings level) is actually recovery from approach to stall. The significance is that it is initiated as soon as stall warning goes off and therefore before actual stall takes place. If one allows the airliner's wing(s) to stall fully, this procedure does not guarantee recovery, or at least recovery that doesn't include overspeed/overstress/ground contact and its success is largely dependent on all-up weight, centre of gravity and luck.

In the event the voting process goes haywire, is there a way to manually get to the point where the pilot(s) have the full control as you describe when you have all three units disagreeing?

It is possible to get into direct law with some simple switching but the procedure is strictly unofficial and, as I'm unaware of any occurence of voting process gone haywire, i think it's unnecessary. I stand to be corrected, of course, if some incident/accident report shows otherwise.

System design very well explained except for the case where two similar but erroneous inputs are sensed by the ADRs (from Pitot/Static system).

We have three indepentent systems, each required to be very reliable. Suddenly two of them simultaneuosly fail in the exactly same manner and their false outputs are diverging from real values with the very similar amplitude over time. I didn't take this scenario into consideration as my opinion is that chances of its occurence are virtually nil.

and you could get your Alternate Law 1 too...(and have real control of your aircraft, without loosing a great deal of protections

I beg to differ. One loses every protection in Alt law (EDIT: except G protection, thanks for reminding me). What Airbus euphemistically calls "reduced protections" are really not much of a protection at all.

[NigelOnDraft]

One loses every protection in Alt lawNot too sure... there's a form of Low Speed / High Speed / Load Factor protection. Sure - not as "hard" as Normal Law, but with systems degraded, a good compromise?

NoD

[airfoilmod]

Reading Clandestino and NigelOnDraft.......and disconcerting.......

[PBY]

Yes, there are still protections in alternate law. In fact, there is 2 kinds of alternate law.
I will call it an alternate law and alternate law without speed stability (my own description).
Both of them have load factor protections. You loose load factor protection only in direct law.
The "better" alternate law still have low speed stability and high speed stability. The only difference with normal law is, that it is overridable. If high speed protection in normal law kicks in and you push the stick all the way forward and keep it forward, the airplane will pitch up against your input. If you do the same in the alternate law with speed protection, you have to let the stick go, before it will start to pitch up. So you can override it. But in alternate law without speed stability you don't have low and high speed stability. In both cases you have load factor limitation as mentioned above and also yaw damping (unless you lost yaw damping due to ADR failure.
I hope, it makes sense.

[hetfield]

The terminology "LAW" is very accurate in this context. Means, the pilot may have have NOT the FULL authority of the aircraft.

Only unauthorized tricks (FACs OFF, Gear Down) bring the aircraft back to basic flying mode if the automatics f*** of., maybe....

[aguadalte]

Quote:
and you could get your Alternate Law 1 too...(and have real control of your aircraft, without loosing a great deal of protections
I beg to differ. One loses every protection in Alt law (EDIT: except G protection, thanks for reminding me). What Airbus euphemistically calls "reduced protections" are really not much of a protection at all. Clandestino:
I think you have to check your Manuals again, on this one. Unless your FCOM's are different from mine, ALT1 gives you still a lot of protection but you can override it! And since my idea was to give the option for the pilot to regain complete control of his aircraft while keeping some protection (to prevent a stressing situation to develop into a worse one), I'm reassuming my suggestion as a good one.

Yes, there are still protections in alternate law. In fact, there is 2 kinds of alternate law.
I will call it an alternate law and alternate law without speed stability (my own description).
Both of them have load factor protections. You loose load factor protection only in direct law.
The "better" alternate law still have low speed stability and high speed stability. The only difference with normal law is, that it is overridable. If high speed protection in normal law kicks in and you push the stick all the way forward and keep it forward, the airplane will pitch up against your input. If you do the same in the alternate law with speed protection, you have to let the stick go, before it will start to pitch up. So you can override it. But in alternate law without speed stability you don't have low and high speed stability. In both cases you have load factor limitation as mentioned above and also yaw damping (unless you lost yaw damping due to ADR failure.
I hope, it makes sense. PBY: Thanks for clarifying this subject in a manner that non-pilots can understand it. As a matter of fact, there are two ALT LAW levels and I was refering to the very first level, that not only, gives the pilot the required amount of protection a stressfull situation may require and at the same time, gives the pilot full authority to override it.;)

[Clandestino]

We're talking semantics here. I never wrote that there are no high and low speed stabilities in alt 1. Just they're not much of a protection compared to high speed protection and alpha protection.

To put things into perspective: while this talk about protections and losses of it scares beejabbers out of interested observes with not much background knowledge of Airbus operations, activating the prot or degradation into alternate law is FDM red event and these get duly reported by our safety bulletin and I cannot recall ever reading about one or other. Ergo, it's not something one would see on a daily or even yearly basis.

[OilCan]

...so many interpretations from guys who supposedly fly the same aeroplane!!!!!

now i'm more concerned.:\

[GMDS]

OilCan

That sums it up: They all "supposedly" fly the aircraft.

Sorry for that sarcasm, but I get the same feeling. So many interpretations, so many explanations, so many Airbus-Rocket-Scientists with even more fancy theories -- and when the proverbial s#!t hits the fan, the poor average skippers ,as my poor soul itself, should know it all, switch it all and with his superiour knowledge of all the wonderful programs and how to circumnavigate them when they screw up, he'll come up as a Sully II.

I always thought that "keep it simple" is the remedy -- and it should.

[Safety Concerns]

What the safety statistics actually show us is that more automation leads to fewer accidents and much better reliability. As so often happens in this world though, never let a good story get in the way of the facts.

[Dysag]

I get the impression that some folks here believe that when you manipulate that great big column in a 777, you're moving the control surfaces directly.

Far from it: you're just making inputs to the flight control computers which then decide how to wiggle the moving surfaces. The only big difference from an Airbus is that the Boeing doesn't have the (anti-stall etc) protections.

[GMDS]

@ Safety Concerns: No one has contested that.

Automation has brought us the blessings of ACAS, GPWS, Cat3 and so forth. The one little setback, and these discussed incidents point in that direction, is that with every progress there are new problems arising. If we deal with them properly, then it's real progress. If we try to cover up the shortcomings, then we devaluate it.
There is no question that envelope protection is a great progress. The moment however that one of these features supposedly lead to aggravating a situation (almost proven on QF72, suspected on the NZ incident) and the involved parties display a reluctance to engage fully, from that moment you get some pros suspicious.

A pilot wanting to pull on a yoke/stick and the aircraft not willing to follow his command, for whatever reason, shows a situation that SHOULD NOT BE TOLERATED. It should be engaged with adequate measures, not only explained and discarded as extremely remote and therefore claiming the system beeing safe enough.

I truly hope most of my fellow pros would agree on that.


@Dysag
You are not entirely correct. When in manual on a 777, you actuate on the Actuator Control Electronics, they transmit to the Primary Flight Computers, these send back the signal which is executed by the ACEs.
If the envelope control protection in the PFCs intervene, you will feel resistance, BUT with a little force you can actuate the ACEs directly and therefore override any possibly erroneous input by a PFC.
That is the huge difference in both fly by wire systems. Such a feature would have worked on QF72.

[Lemurian]

Truly an amazing thread, and quite indicative of the "aero-culture" of the majority of the posters in this forum.
Either we're talking about aviation safety or Pprune has become the last refuge of the vocal anti Airbus brigade.
Just two comments :
1/- Why do they only concentrate on the paint on the static part of the safety bulletin ?
As far as I still can read, there were TWO recommendations in it :
As a result of the investigation's preliminary work and without prejudging the outcome of the investigation, the aircraft manufacturer's flight safety department in France today issued new recommendations to Airbus operators.

It said during painting and maintenance it was important to protect all aerodynamic data sensors.

It has also said that tests such as low speed tests "must be performed at safe altitude and be preceded by a recall of basic rules as regards to minimum speeds and recovery actions".

Air New Zealand chief executive Rob Fyfe today welcomed the recommendations.(extract from the YahooXtra article).
Is the bit about performing low speed tests at a safe altitude, with a proper briefing just for the dogs ?

2/- The so-called technical discussion on A-vs-B FBW smacks of so much bias and intellectual dishonesty that it's hardly worth mentioning, and the fact that people talk about "Prims and Secs" (which are not in the architecture of the 320 family but on the 330 and later models) shows the level of awareness of what's involved.The folllowing statement is quite representative of the general atmosphere :
If the envelope control protection in the PFCs intervene, you will feel resistance, BUT with a little force you can actuate the ACEs directly and therefore override any possibly erroneous input by a PFC.
That is the huge difference in both fly by wire systems. Such a feature would have worked on QF72.
First I would say that on a particular MH flight, it didn't work.
Second, taking into account the Hudson ditching, which happened in Alpha prot, but two knots below Alpha prot speed and just 3 above Alpha max can the anti-A brigade please describe how easy that would have been on any other type (increased efforts on the yoke and inside continuous stick shaker... yeah! easy as pie !)
As far as I'm concerned, I'd still wait for the official prelim.
And I hope that the majority on this thread won't eat their caps. I'd gladly provide the mustard.

[GMDS]

Don't get excited, Lemurian. It's as if you'd throw a stone into a sheepherd, the one thats hit shouts the loudest ....
I repeatedly said that it's not a A vs. B argument. It's about a Airbus particularity i don't like. If someone else goes the A-B way, i only clarified some misconceptions.

To your argument:
Second, taking into account the Hudson ditching, which happened in Alpha prot, but two knots below Alpha prot speed and just 3 above Alpha max can the anti-A brigade please describe how easy that would have been on any other type (increased efforts on the yoke and inside continuous stick shaker... yeah! easy as pie !)

it goes down the same road.

By the way the LHR almost idle approach was done in exactly this manner, and it worked to save a bad situation just as the Hudson incident did.

Once more, i am not on a anti-Airbus crusade, i simply point out that there is a weakness and i don't like the way it is dealt with. The responsable people should accept that there is room for improvement and should act accordingly.

[NigelOnDraft]

GMDS Once more, i am not on a anti-Airbus crusade, i simply point out that there is a weakness and i don't like the way it is dealt with. The responsable people should accept that there is room for improvement and should act accordingly.There are weaknesses in all designs, that then cause accidents, and strong points in each design that are never really acknowledged when they prevent accidents. But to be honest, it is not up to us, the pilots, how these are certified or balanced.

I fly Airbus. I'd rather fly certain B machines for the fun of flying them, but would then get slandered for hand flying in a busy TMA :{

There is no evidence yet that this accident was FBW related... as a few posts above, there seem 2 recommendations not directly related to FBW. It has always been my opinion that the "unusual" nature of the Flight (post Maint, post lease Flt Test) would be a factor in the accident - that's just the way the swiss cheese works i.e. drawing conclusions from it and relating them to normal Pax operations will probably not be appropriate :=

Of course B aeroplanes never have such issues http://www.pprune.org/rumours-news/358016-easyjet-b737-pitch-down-incident-12-january.html

In summary, I did not design the Airbus, I just sit in the damn thing. But it does it's job, in a low workload and efficient manner... as do varous B products. Posts above were just to correct or clarify other posters points... and I see no need for a big red button - the aircraft systems do that perfectly well by design, and if and when that design is found wanting, as with all types, it will be modified by the appropriate parties based on evidence, not armchair experts who just don't like it, probably because it's french :)

NoD

[PJ2]

GMDS;
Once more, i am not on a anti-Airbus crusade, i simply point out that there is a weakness and i don't like the way it is dealt with. The responsable people should accept that there is room for improvement and should act accordingly.
The same claims and comments were made by dozens on the TAM A320 Congonhas accident regarding the thrust levers. "If only Airbus had designed...(fill in the blank)". NoD is right - every design is a compromise which satisfies conflicting requirements. The conclusions arrived at there and should be here were the correct ones: The A320 design is highly successful, has millions of uneventful landings, does not have a record of crew difficulties with the thrust levers, the sidestick, the C* Laws or anything else in the design. You may be uncomfortable and don't like the way it is dealt with and that's fine so long as such differences contribute to an improvement of the design without compromising other aspects of the airplane. I respectfully suggest that such a contribution can't be credibly offered unless you've spent a lot of time in the aircraft, not just flying it but learning deeply about it. Forgive me if I'm wrong about your background!

There isn't very much that the engineers haven't thought of, but there are a few from the early days. The VS/FPA issue had the potential for a human factors accident even before Strasbourg as I have seen the confusion personally on NPA's in the maritimes. Understanding "IDLE/OPEN DESCENT" and the autothrust system has been another for those transitioning to the airplane from another type.

I always felt that if a student could, while turning and climbing or descending, as well as on the approach, take the airplane from fully automated flight to fully manual flight and back again with everything engaged, without the passengers ever knowing something had changed "up front", s/he knew the airplane pretty well. Disconnecting the automation and flying the airplane like a 172 was another key to understanding, but this is where training, not the airplane, fail miserably.

The record of the design speaks for itself. The accident rate is no worse than any other design and the automation and fault-handling design is better than most. Those who call for the big red button simply don't understand a host of issues, many of which are related to such design matters.

All that acknowledged, the point illustrated by the QF72 incident may be something that Airbus should and perhaps is looking at - we don't know. A "BRB" won't solve such a problem for many reasons, weight for a separate "intervention" system not the least of these problems. The 727 on manual reversion with only one rudder working was certainly a handful and required very careful inputs, as does a 320 being flown on stabilizer and rudder alone, both of which are serious emergencies.

[Lemurian]

Another example of the arguments of the brigade I was referring to and Clandestino's reply :
We have three indepentent systems, each required to be very reliable. Suddenly two of them simultaneously fail in the exactly same manner and their false outputs are diverging from real values with the very similar amplitude over time. I didn't take this scenario into consideration as my opinion is that chances of its occurence are virtually nil.
There was, Clandestino, a more to the point answer, IMO : That this kind of failure is more likely to happen -however remote it might be- on a Boeing FBW as the boxes are the same. Airbus had these computers made by different electronics manufacturers in order to augment the un-likeliness of it happening.
But of course, Boeing products are totally trouble free, aren't they ?

As no one had taken the hint I made, just look into the description of a chandelle...or ask the 320 TRIs who've performed the required manoeuvres for a post-maintenance acceptance test...and compare these to the two-surfers' witness reports...And then re-read the Airbus recommendation, past the static port bit.
Still no clue ?

[Lemurian]

By the way the LHR almost idle approach was done in exactly this manner, and it worked to save a bad situation just as the Hudson incident did.
I respectfully beg to disagree.
The common characteristics of the two incidents is the cool-headedness of the Flight deck crews.
That said, one was trying to extend the glide as far as possible,
The other was to touch-down (on the water) at as low a speed as possible.
Piloting-wise, those are completely different strategies.
I don't say it would have been impossible on a T7, but a lot more difficult, due to the vastly increased effort on the yoke while trying to ignore the stall warning.

[burty]

What the safety statistics actually show us is that more automation leads to fewer accidents and much better reliability

We are told this on a regular basis, highest level of automation etc etc, yet look at Southwest, limited automation and a fantastic safety record (sans two overruns). While automation has fantastic advantages (Cat 3 ILS for example), it's absence in the highest form should not necessarily lead to disaster?? And yes I know Southwest are hooking up everything again but...

[Bruce Waddington]

Burty,

You write "We are told this on a regular basis, highest level of automation etc etc,"

Airbus states very clearly that pilots must learn to use the appropriate level of automation, which may be none.

Those who tell us to always use the highest level of atutomation are disregarding one of the 'Golden Rules' and should be made to stand in the corner until they have them memorized.

During my time in the A319, A320, A321, A330 and A340 I saw two common errors among our fleet pilots. The first was not disengaging the automatics when they could no longer help you ..... and the second was not engaging them when they could.

best regards,

Bruce Waddington

[Huck]

There is no excuse for not maintaining the highest level of hand-flying skill.

Except laziness.

In our MD-11's we've backed off from the "highest level" idea also. Our new mantra is "proficiency in all levels." Lo and behold, no tail strikes in quite some time......

[vanHorck]

Not all airlines encourage flying AP off...

Some airlines actively discourage GA flying

The airlines interest may be to promote automation over pilot skills. Perhaps there are statistics on the matter?

[DC-ATE]

"The airlines interest may be to promote automation over pilot skills. Perhaps there are statistics on the matter?"

The airline's interest is to eventually eliminate the pilot altogether!

[Condor99]

Still no mods here to change the title of this thread?
Definitely this was nothing about a "training flight"!
Please, update. Thanks by advance.

[llondel]

I remember some time ago a report that said it was better to let the humans fly the aircraft with the automatics watching to warn of errors than it was to let the automatics fly the aircraft with the humans watching.

Humans make mistakes and become complacent - how many know they've read something and seen what they expect to see, not what's really there? If your automatics generally work fine and only report errors on sensor failure, how many people are going to immediately believe there's a problem the one time it really is a serious error?

[airfoilmod]

Don't innovate well. Not good at deductive reasoning, and have very little time in the sim (sic). They aren't skeptical, don't have families at home and have no time in type on other aircraft. Once they "fail", they're done, largely.

On UAL 232 what happens w/o a dead heading C/A in the back to suggest constant differential thrust on the remaining two?

Just Sayin'

[zerosum69]

what are the switch selections which have to be made (on the overhead panel i assume) to fly the aircraft in normal law?


is there a recall drill in the emergency checklist to do this?

[aguadalte]

Don't innovate well. Not good at deductive reasoning, and have very little time in the sim (sic). They aren't skeptical, don't have families at home and have no time in type on other aircraft. Once they "fail", they're done, largely.

On UAL 232 what happens w/o a dead heading C/A in the back to suggest constant differential thrust on the remaining two?

Just Sayin'

Can you please elaborate a little bit more, for better understanding your point please?
Thanks

[NigelOnDraft]

what are the switch selections which have to be made (on the overhead panel i assume) to fly the aircraft in normal law?None... the default with everything working is Normal Law...

NoD

[airfoilmod]

In a general way, I mean to contrast the fundament and perspective of failure.

The Culture of automation seems to be up for criticism here. Likewise the Stick and Rudder brigade. What is important is the Interface twixt the two. Calling a "sidestick" a Stick is presumptuous to some, myself included. The Bus isn't a video game per se, but some pilots are offended by its "arrogance". It's a machine. So is a Boeing.

No Human can leverage the control surfaces on a modern jet, hence boosted controls. It is the motivation for and "thought" behind that impetus that fuels the argument. I tend to favor Red Button, a return to all human pilotage innovating and "creating" a solution in an emergency.

There would be no controversy if many pilots didn't consider the Bus an attempt in some fashion to usurp a pilot's ultimate COMMAND.

AF

[aguadalte]

Agree.
And what kind of solution would you accept? Meaning, what kind of interface between the red button and the automatisms?

[airfoilmod]

Depends on your POV. Some would have the "auto" revert to "manual", some would have it revert to more "auto". If on the one hand, auto can be overridden and hand flown, the hand fly folks would say, why the auto in the first place? I have two recent incidents to fall back on.

BA038. Engines were running, but refused commanded thrust.
1549. Engines were running, but idling. Both are odd results given a qualified crew on deck. Suspicion falls on FADEC.

If engines are spooling and burning fuel, why aren't they increasing when "commanded". The 64 $ question, perhaps. Time will tell.

[NigelOnDraft]

BA038. Engines were running, but refused commanded thrust.
....
If engines are spooling and burning fuel, why aren't they increasing when "commanded". If you read the AAIB Bulletins quite clear :ooh: To increase thrust requires increased Fuel Flow... and if the (extra) fuel cannot get there, no increase in thrust ;)

NoD

[bubbers44]

The United 232 DC10 that landed using differential thrust would have been flown as they did whether or not the check airman in back had come up to the cockpit or not. They had no choice and the only solution to get it on the ground under control was using that technique.

For some reason the captain elected to let the pilot sitting in the jumpseat operate the throttles to line up with the runway. All went well until the power was reduced for touchdown and it cartwheeled off into the corn field. A lot of people survived so the teqhnique worked but the captain might have had a better perspective from his normal flying position making the final adjustments from his seat in my opinion.

[zerosum69]

thanks nigel - my mistake, i was referring to direct law. what is the sequence you follow to engage that?

i always imagined it would be easy to make this transfer (if you ever had to do it, it would be in a confusing situation, where the flight control logic wasnt responding as you expected or the instruments were giving strange indications).

is this an emergancy drill?

[J.O.]

Direct law is a failure mode that is a consequence of certain failures, such as dual hydraulic loss or a loss of both radio altimeter systems. It is not something that the crew will "select" all on their own when they "think" they need it.

[NigelOnDraft]

There is no button or drill that the crew perform to "select" a different Law specifically... the aircraft systems determine which Law you are in.

There are drills / buttons / levers that have the effect of changing the Law e.g. lowering the Gear in Altn law will put you in Direct law... but you lower the gear so you can land, not to effect the change ;) There are even some drills where you deactivate systems etc. for the purpose of a law change.

In general, the law changes are transparent to the pilots in flying terms, and I can see no great need to wish to fly in 1 Law or another...

NoD

[aguadalte]

I think the problem here is that, regarding Flight Controls Laws, it is the aircraft logics that "decides" when the bird is sick. It then downgrades the Law to a certain level. The pilot has nothing to do with it (except when performing ECAM actions or selecting some systems off, or selecting Gear Down).

If, by any chance, (coming back to this thread's subject), ADR's got (all of them) the same erroneous information - leading to high speed wrong indication, followed by automatic speed protection - one may think that, there was nothing a pilot could do to counteract the automatic pitch up inputs, except by using non-standard procedures (like inducing the aircraft to an Anternate or a Direct Law) and this is really against all of the Airbus philosophy and formation.

Someone suggested a Red Button. I suggested a change in the software/logics of the use of the instinctive disconnection push button, located in the side stick, to "bring" the aircraft into a "status" (Alternate Law 1) which would bring the aircraft back to manual, although maintaining a great deal of protections. This would be a pilot friendly status, once he could effectively handle and override aircraft built-in protections in case a serious situation arises. Once the problem was solved, he could return to Normal Law (provided certain conditions met) by switching the Auto Pilot ON.

Regarding some comments I've seen here in this thread, I'd like to leave a small message: Please don't play with our intelligence and don't play the role of those guys who think we don't know enough of the aircraft to even make any type of suggestion. Just give us the benefit of doubt, to someone who flies airbuses for almost 20 years, who has studied the system and who has, at least, looked at the Manuals, before coming to this thread making "suggestions"...

Please do not infer from my words any agenda against Airbus. My sole agenda is against arrogance and for flight safety.

As I said before: Airbuses are great aircraft, but they could be better.
Fly Safe;)

[Clandestino]

The subject of this thread is the accident of which next to nothing is known, yet many a post is written as if protection gone awry has been proven to cause the crash.

[stickyb]

I think the problem here is that, regarding Flight Controls Laws, it is the aircraft logics that "decides" when the bird is sick. It then downgrades the Law to a certain level.

Speaking not as a pilot but as a computer boffin, I think that statement is fatally flawed. No computer yet in use aloft has an "adaptive" or "evolutionary" capability. All the computers used aloft run according to very strict rules - those in the program laid down by the software writers.

There are usually only 2 reasons why computers and automation go haywire:

The program has become corrupted
The program didn't cater for a particular situation.We must remember that, whatever the make or model, the computers are only doing (or not doing) what they have been told to do. Of course I am simplifying like crazy and there is a whole army devoted to writing specifications and then ensuring that the finished product adheres to that specification, but the bottom line is usually "if the automation misbehaves don't blame the automation, blame the software designer/writer"

As for wanting a big red button to kill the automation and revert to hand flying, there is not and can never be such a thing. You could have a button that would cut out some of the automation, but to cut it all out is impossible - the physical links between the pilot and the things he needs to control are no longer there, having been replaced by electrical signals.

[GMDS]

aguadalte

Absolutely spot on and well put! :ok:

GMDS

[lomapaseo]

stickyb
Quote:
Originally Posted by aguadalte
"I think the problem here is that, regarding Flight Controls Laws, it is the aircraft logics that "decides" when the bird is sick. It then downgrades the Law to a certain level. "

Speaking not as a pilot but as a computer boffin, I think that statement is fatally flawed. No computer yet in use aloft has an "adaptive" or "evolutionary" capability. All the computers used aloft run according to very strict rules - those in the program laid down by the software writers.


Well here I was agreeing with aguadalte and you come in with an authorative sounding statement that doesn't seem to me to match the discussion.

Perhaps there is a misunderstanding among us of the meanings.

Could you precise a little more why/how the aguadalte statement is flawed?

[llondel]

What can happen, and I know it occurs with anti-lock brakes on both aircraft and cars, is that if the computer systems receive a set of conflicting inputs, there can be a deliberate decision on the part of the software to drop out and let the pilot/driver do the work without software interference/assistance. As such, it's similar to option 2 from stickyb's post although it's not going haywire, it's deliberately giving up control.

If there's a bug in the software then it may do strange things if it receives an unusual combination of inputs, either by something crashing or (more subtle) causing an overflow in an intermediate part of the software that produces incorrect output. I think they lost an Ariane rocket to this one once.

[esa-aardvark]

to llondel...
Ariane V failure was definately a software failure.

Without going into details the onboard computers
contained inertial reference software which was not
needed after launch. On Ariane IV which it was designed for
it was normally left running, this practice also used on V.
Due (I remember) to higher slew rate of the short fat Ariane V
some kind of data conversion error occured. This caused
an error to be presented to the flight computer, which in turn
demanded full delection of the motors, ie game very over.

Someone will correct me I'm sure.

Lessons to be learned....
At least try to validate under flight conditions, but I'm not
sure how that would relate to aviation software

[OFSO]

esa-aardvaark wrote "someone will correct me I'm sure".

Not really, old colleague, but I'd say the failure was caused by using segments of software from an earlier ARIANE in a later model where it wasn't appropriate.

And here's another one: when commissioning a new spacecraft in orbit, instead of action 'A' happening when command 'A' was transmitted, action 'B happened when 'A' was transmitted and action 'A' happened when 'B' was transmitted.

Representatives of the French constructor of the spacecraft who were present were asked to explain. Pulling out an old envelope and consulting notes written on the back, the French engineer squinted at the scruffy paper and said "we 'av changed ze software just before launch..."

Not a rumour, I was present when it happened.

[aguadalte]

What can happen, and I know it occurs with anti-lock brakes on both aircraft and cars, is that if the computer systems receive a set of conflicting inputs, there can be a deliberate decision on the part of the software to drop out and let the pilot/driver do the work without software interference/assistance. As such, it's similar to option 2 from stickyb's post although it's not going haywire, it's deliberately giving up control.

If there's a bug in the software then it may do strange things if it receives an unusual combination of inputs, either by something crashing or (more subtle) causing an overflow in an intermediate part of the software that produces incorrect output. I think they lost an Ariane rocket to this one once.

...and what happens, when all the sensors receive the same information (pressure lines frozen with water, leading to wrong - but not abnormal - parameters messages to flight computers?

[[Steve]]

"Could you precise a little more why/how the aguadalte statement is flawed? "

Speaking as another computer boffin (and one who has been responsible for software where failure could result in loss of life) I read it as stickyb actually agreeing with the main assertion -- as I understand it -- that it is *really* hard for a computer to know when it is incapable of producing the correct outputs for a given set of inputs. aguadalte suggests a "big red button" (BRB), which stickyb claims is not feasable.

I tend to agree with both of them :-)

Where I disagree with stickb is in his assertion that a BRB is not feasible. If the software already has the ability to gracefully degrade the level of automation, then another input that forces it to do so is an increased complexity, but one not nearly as large as the complexity involved in "knowing" all the exceptions that should cause this to happen automatically.

What worries me, however, is whether such a manual override would lead to more or less problems. The obvious example is where some un-commanded pitch up or down is overridden by flying more "manually". However in other cases where a pilot is under extreme stress, or where (s)he becomes situationally unaware, the BRS usage or the actions taken thereafter may be inappropriate and lead to a worse outcome.

From my reading here, some pilots are of the view that they should be given the opportunity to overstress an aircraft if flying within the limits will result in a less desirable outcome. I understand (poorly, probably) that Airbus' attitude is that the automation should help prevent you getting into that place between a rock an a hard place -- which does not directly address the issue.

In my case, the operators of the software were (are) not in personal danger, and the additional cost of dealing with tricky cases was considered unwaranted, so we opted for a system that simply suggested the "correct" action, but left the operator to manually move the controls (in a manner of speaking) and hence with the ultimate authority and ability to override the automatic suggestions. I am in awe of the software which runs aboard modern aircraft, as in many cases other design decisions have been taken (and with great success).

An interesting question from my perspective is "How often do the various protections governing (say) Normal law get triggered in a way that protects the pilot and aircraft from a negative outcome vs how many times have there been incidents where these protections or the erroneous triggering of them has resulted in a negative outcome?" (I ask this because I have no idea)

I've been trying to write this last paragraph for some time. Please excuse me if I express myself poorly. Even if it were shown that pilots were statistically a far worse bet than potentially failing computers, I would hate to be the pilot who may meet his fate *knowing correctly* that all he needed to do was override a computer :-(

[Clandestino]

...and what happens, when all the sensors receive the same information (pressure lines frozen with water, leading to wrong - but not abnormal - parameters messages to flight computers?

FCOM 1.30.50 and 1.34.10 refer. Probes are heated, heating is monitored by ECAM, ducts for ADIRU 1 & 2 are short and independent, chances for all of them to froze simultaneously are appx once in a quintillion hours of operation.

[GMDS]

What worries me, however, is whether such a manual override would lead to more or less problems

The eternal argument not to act.

Fact is that on the other fly-by-wire product, there has not been one incident where a manual override of a computer has led to a worse situation. (Not that i would know of an incident where computers gave erroneous signals, though.)
Fact is as well, that in at least one Airbus (QF72) such erroneous signals led to an erroneous input that was at first not recuperable by the pilot. (A override capability would have been very welcome I suppose.)

Reread the two facts and then the entry argument and very basic common sense will give you an answer, at least to me ......

[aguadalte]

FCOM A320 - 1.27.30 Page 2

SmartCockpit - Airline training guides, Aviation, Operations, Safety (http://www.smartcockpit.com/pdf/plane/airbus/A320/systems/0010/)

Please go to that page and take a look at the schematics. You'll find out the conditions for RECONFIGURATION CONTROL LAWS on A320. Maybe then, you may understand that, despite of being highly improbable, one could fly in a situation where the aircraft doesn't downgrade to alternate law, trapping the pilot among protections "active" leading to lost control. If, by chance, for instance, you get wrong (yet within parameters) hight speed information through all ADR's, the system will be kept in Normal Law, and High Speed Protection will keep active sending a nose up input and pilots will be unable to bring nose down. (That would be a case for a "Red Button" or a new logic to the instinctive disconnection push button, in order to bring the Law's to a degradation mode, where the pilot still have control of the aircraft).

Please tell me, if I'm wrong. :E(I'd rather be wrong...):sad:

P.S.- What is the probability of 4 engines failure? Yet it has happened ...:rolleyes:

[galexy]

British airways B747 once lost all four engines due to volcanic ashes. but i believe they got them back also and made a emergency landing. This flight was from manila.

thanks

[Clandestino]

Fact is as well, that in at least one Airbus (QF72)

As long the final report is not out, it is not a fact!!!!!!

However this report is final, I recomend it for those interested in FBW architecture and voting issues. (http://www.atsb.gov.au/publications/investigation_reports/2005/AAIR/aair200503722.aspx) I apologise for being unable to provide Airbus example.

despite of being highly improbable, one could fly in a situation

How do you find yourself in a highly improbable situation is beyond me.

What is the probability of 4 engines failure? Yet it has happened ...

Seeeeeveeeereeely small, unless you inadverently enter the VA cloud, or have your chip detectors installed without O-rings on them, when it's quite high.

Clandestino
as of today, former Airbus driver.

[zerosum69]

stickyb: clearly, there are no pushrods and for FBW you will always have an electronic middle-man to some extent. However i thought the idea of direct law was to have a simple backup bit of software that was highly unlikely ever to cause control problems due to software/sensor malfunction. I'm just surprised that the pilot apparently cant easily select it.

i understand why its designed to degrade automatically to direct law in some non normal situations when you drop the gear etc - to ensure the thing will definitely flare when you pull the stick back etc.. but what about the oh **** scenario where the plane suddenly bunts towards the ocean for no apparent reason? Don’t you need a way to tell it to stop obeying the busted AOA probe and deflect the elevator back to where you want it?

(this discussion is not intended to speculate on the accident cause)

[forget]

BA 747/Volcanic Ash. This flight was from manila.

Kuala Lumpur - Perth.

[GMDS]

As long the final report is not out, it is not a fact!!!!!!


... true, forgive me for that imprecision. As we are on a rumor network, what other than an erroneous computer input could it be? Gust?? Pilot lying?? Yes, I am sarcastic here ...

On a lighter note Clandestino, enjoy your retirement, or did you really change to the dark side?

[llondel]

aguadalte:

I don't trust computers to handle anything more serious than trivial fault conditions and I design them and things using them. Ultimately they have a set of instructions on what to do, which is presumably arrived at by a bunch of experts writing down a load of scenarios, what inputs indicate problems and what the automatics should do about it. They only need to miss one, or consider it so unlikely that they don't need to accommodate it. Even nuclear power station design has the concept of a probability threshold for accidents to limit the cost of safety.

As for all the instruments giving the wrong answers, I'd say that a lot of pilots would find it difficult to fly as well, although given the Mk.1 eyeball, they'd stand more chance than a machine, at least in daylight. (Aeroperu with the ports taped over and in the dark?)

[Clandestino]

Thanks GMDS, I'm not retiring, just switching seats and type.

what other than an erroneous computer input could it be?
After reading ATSB preliminary report (especially the diagrams at the back) I'm more concerned about output than input. It seems that one AoA signal was spiking wildly, second was stable and third, sadly, is not mentioned in prelim. I'll wait for final report before worrying more, though.

[DC-ATE]

If (BIG IF) the accident report were to come out showing a fault in the
FBW/computer system on board, does anyone really think that FBW will be
eliminated from this model or any other model aircraft? Of course not. But, then again, I doubt very much the report would indicate that whether it was true or not.

Aside from the cost savings involved and the fact that engineers now-a-days grew up with arcade games and computer games, what is the big deal with FBW anyway? As someone pointed out, the DC8/9 were the last 'real' airplanes that were cable-operated. FBW originated with the need to control very unstable military fighters. What's the need, other than cost, to carry it over to commercial aircraft? The old saying, "If it ain't broke, don't fix it" would apply here I would think.

If you couldn't tell, I'm not in favor of computers telling the pilot what to
do and what not to do. And, I like the idea of the control wheel and
throttles, etc. connected to something by cables, not an electric current.

[Clandestino]

If (BIG IF) the accident report were to come out showing a fault in the FBW/computer system on board, does anyone really think that FBW will be eliminated from this model or any other model aircraft?

FBW was found at fault at Bilbao and part of it (alpha protection) had to be modified afterwards. Perhaps we'd live fat, dumb, and happy with unmodified
FBW if it weren't for Iberia crew putting the A320 through its paces.

I'm not in favor of computers telling the pilot what to do and what not to do.
Good, because on Airbus it's the pilot telling the computers what to do. Computers only refuse if one tries to: pitch above 30 deg ANU or below 15 AND, bank over 67 degrees, overspeed, stall or over-G the aeroplane. One just has to fly nicely and smoothly to avoid computer intervention.

[lomapaseo]

[Steve]

I've been trying to write this last paragraph for some time. Please excuse me if I express myself poorly. Even if it were shown that pilots were statistically a far worse bet than potentially failing computers, I would hate to be the pilot who may meet his fate *knowing correctly* that all he needed to do was override a computer :-(




You express yourself quite clearly :ok:

and of course one could add a BRB but the trades would be complex and difficult to certify. But then again our amature discussion of this in this thread gives us something to entertain :}

[Smilin_Ed]

How do you find yourself in a highly improbable situation is beyond me.

Ask the flight deck crew of USAir 1549 about improbable situations.:)

[DC-ATE]

Clandestino -
"Good, because on Airbus it's the pilot telling the computers what to do. Computers only refuse if one tries to: pitch above 30 deg ANU or below 15 AND, bank over 67 degrees, overspeed, stall or over-G the aeroplane. One just has to fly nicely and smoothly to avoid computer intervention."
---
Well, there just might be a time when those computer limitations NEED to be exceeded. If the airplane can't handle it, then there might just be something wrong with the design.

[Clandestino]

US Airways 1549? Yukla 27 set the precedent, flying through flock of ducks (or were they geese?) and knocking out both engines is not quite an improbable situation.

Well, there just might be a time when those computer limitations NEED to be exceeded.

Into what?!? Stall? Overspeed? Spiral dive? It would be overstatement if I were to say that it's the matter of good airmanship to avoid situations where only limitation busting can save the day - it's the matter of simple self-preservation.

[lomapaseo]

US Airways 1549? Yukla 27 set the precedent, flying through flock of ducks (or were they geese?) and knocking out both engines is not quite an improbable situation

Agree.

However, in any product caused accident the exact combinations of all causal factors should be thought to be improbable beforehand.

In this accident there may be a surprise ingredient not recognized beforehand. (other example would be the BA038)

[DC-ATE]

Whatever it takes to save the airplane.

[DozyWannabe]

DC-ATE:
Well, there just might be a time when those computer limitations NEED to be exceeded. If the airplane can't handle it, then there might just be something wrong with the design.
There's a video doing the rounds of YouTube where Bruce Dickinson (of Iron Maiden fame, and Astraeus pilot) takes the A320 for a "test drive". One thing you realise very quickly from watching the video that you won't get from reading the numbers is that the A320 is actually capable of getting and staying in some pretty extreme attitudes without exceeding the airframe's tolerances - and the computer helps it stay there.

It's a *massive* misconception that the A320 FBW system is there to "tell the pilot what to do" or "stop the pilot 's natural ability to command". The A320 FBW will do *exactly* what the pilot tells it, and stay there as long as it is possible to maintain the attitude commanded.

If you think you'll need more than 67 degrees of roll to get out of a situation in an airliner I'd be as concerned as to your abilities as you are about the A320's!

[Brakes on]

DC-ATE,
If the airplane can't handle it, then there might just be something wrong with the design.
Whatever it takes to save the airplane.
Save the airplane? The computer limits the forces on the aircraft to design limits (with a margin, I assume). If you fly the aircraft manually, how do you know where these limits are?

[DC-ATE]

Well, I don't feel like arguing the point here, but no one has shown me where the FBW system is BETTER than what we had before.

[Brakes on]

DS-ATE,
Run out of arguments?
May I suggest you read the last paragraph of my post again? Maybe this will give you a clue on how (part of) the FBW will help the pilot not to overstress the plane.

[DC-ATE]

I've read your last paragraph a few times. It does not tell me why FBW is BETTER than before.

There are those that listen to CNN and those that listen to FOX. Nothing anyone can do will change their minds.

[stickyb]

stickyb


Well here I was agreeing with aguadalte and you come in with an authorative sounding statement that doesn't seem to me to match the discussion.

Perhaps there is a misunderstanding among us of the meanings.

Could you precise a little more why/how the aguadalte statement is flawed?

Sorry if I did not make myself clear first time around. The false statement i was trying to counteract is "the computer decides". The computer decides absolutely nothing that its programmer hasn't told it to. Behind every computer program is a human programmer (why does everyone think of Mr Gates?). Too many people think "the computer" can decide things - it doesn't, just regurgitates what the programmer put there. That's where the GIGO syndrome came from (Garbage In, Garbage Out)

The other point about the Big Red Button is that is not a simple task of switching of the automatics, if you did that most modern planes would fall straight out of the sky. The only thing a BRB can do is switch off some of the automatics - the key question will always be which ones do you trust and which ones do you dump.

[flash8]

Too many people think "the computer" can decide things - it doesn't, just regurgitates what the programmer put there. That's where the GIGO syndrome came from (Garbage In, Garbage Out)

With all due respect, and not to be off topic, I don't think many people believe that computers have autonomy of mind. And as for Programming, the fundamentals here are not so much what was intended but what was unintended.

Most critical Software (as far as I know) is formally verified using a methodology such as VDM or Z, as well as isolated n-team n-version programming and polling/voting (or at least it was for the 744 RR EEC). Intended operation is well defined and documented (and probably published somewhere).

Even with n-teams and n-versions in n-languages with n-formal verifications the question is can insidious side effects (for example through multiple system interaction) cause unintended issues through all versions - resulting in a poll and vote for the wrong side?

Of course a faulty initial Specification screws everything up.

Its a few years since my Soft Eng degree so I hope I still make sense.

[lomapaseo]

stickyb

I'm cool now, I suspected it was a fortran language problem between us :). Some of you have made a good education out of this for those of us willing to learn. I probably will pick up and use from this some simple-flying explanations when trying to explain this to non-aviation folks.

[belloldtimer]

G'day,

You said "as long as the final report is not out" is there a preliminary reprot. I've just seached thru the thread and can't find one, could you post a lnk to it if you have it.

Thanks Steven:8

[Clandestino]

@belloldtimer:

We were discussing A330 upset, prelim is here:

AO-2008-070: In-flight upset, 154 km west of Learmonth, WA, 7 October 2008, VH-QPA, Airbus A330-303 (http://www.atsb.gov.au/publications/investigation_reports/2008/AAIR/aair200806143.aspx)

@Iomapaseo:

Sorry, page break made it look as if it was out of nowhere.

[lomapaseo]

Clandestino

AO-2008-070: In-flight upset, 154 km west of Learmonth, WA, 7 October 2008, VH-QPA, Airbus A330-303

I'm not sure why you posted a link without any explanation:confused:

In my view it does not relate to the accident being discussed since this thread should now consider the statement about a surge in power associated with the pitch up.

In my view if there was any direct correlation with the accident in the link, Airbus would have indicated so in their Safety office release.

[Safety Concerns]

this thread has got ridiculous. So

AOA sensors painted over and stuck in one position. A/C stalled and crew performed actions as any crew would do on any aircraft, digital or analogue but it was sadly too late.

Change the bloody boeing v airbus record

[aguadalte]

Dear SC:
I'm quite astonished with the acrimony on your last post.
I thought that you would render some credit to the Safety Concerns name you have chosen to sign your opinions on this forum. Only someone who doesn't have a clue on the importance of the differences of philosophy and design between B & A, may think that it all resumes to a "bloody boeing v airbus record"...;):sad:

[Safety Concerns]

Dear aguadalte, I think you know I respect your opinion but I feel you have misunderstood mine here.

[belloldtimer]

Boys and girls,

Can't we play together. The palyground is big enough for one and all witout fighting about petty things, afterall our primary goal is information to avoid furhter loss of life and liberty isn't it ? Correct me if I'm wrong but the sole purpose of this forum is the dissemination of information to other professionals in the same field.

Yes/No:D

[CONF iture]

Quote:
Fact is as well, that in at least one Airbus (QF72)
As long the final report is not out, it is not a fact!!!!!!
Clandestino, do you mean Airbus rushed to publish a RED OEB just for fun ?


Also, as you mention the Malaysian 777 case, and so did others earlier, that incident is very different from the Qantas case :

The upsets were AP as well as pilot induced.
In the case of QF72 the airplane was nicely manually flown but the protection did the mess.


Now, to know if one simple (guarded) push button should be installed in the FBW Airbus in order to easily go back to the basic DIRECT LAW ... why not ?
Not a big deal, almost any other airplane fly in DIRECT LAW anyway, do they fall out from the sky ?
To me it would be a very simple way to make sure protections don't play a trick when in doubt ...




The A320 FBW will do *exactly* what the pilot tells it, and stay there as long as it is possible to maintain the attitude commanded
QF72 also demonstrates the Airbus FBW can also do what the pilot never told him to do.

[Safety Concerns]

which is why the A V B argument doesn't belong here.

We would like to know what happened to an A320 and why. I am not interested in egoistical nonsense about man being better than a machine.

As I stated very early on both, in fact all manufacturers build inherently safe aircraft. Please get back to what happened and not what might have happened with superman at the controls.

[Clandestino]

For the n-th time:

From the ATC's viewpoint, flight was proceeding normally untill the radar and radio contact was lost as the aeroplane was returning to land. Maybe I'm mistaken but I believe if some significant fault (and probe or ADIRS fault is significant) during acceptance test flight, flight is cut short and aeroplane is returned to maintenance, untill the time it's pronounced fit for another try. Blocked probes would result in anomalous readings immediately after lift-off, followed by prompt return.

Regarding the Perpignan accident, we're no smarter than we were three days after the crash.

Clandestino, do you mean Airbus rushed to publish a RED OEB just for fun ?

Whatever was written in it, it was published it because Airbus deemed it it necessary. If any aviation-related entity believes that non-acting has serious safety implications, it will act on the basis of high probability and not wait for certainity. OEB's can be withdrawn or ammended.

Now, to know if one simple (guarded) push button should be installed in the FBW Airbus in order to easily go back to the basic DIRECT LAW ... why not ?

Because pilots have their performance and limitations, too. If a pilot is so confused and behind the aeroplane that he allows it to enter protection, then he might start panicking and cut-out the protection that's doing it's job in mistaken belief that it's gone beserk. Mind you: no FBW protected aeroplane, be it Boeing, Airbus, Tupolev or Embraer, has been lost to stall or spiral dive in everyday operation yet. And protections are far easier to implement and more effective if you have FBW than classic controls.

That is not to say that protection makes anyone & his dog able to fly an Airbus. Staying out of protections still demands skill, concentration and foretought. And very seldom something goes seriously wrong and one ends up in altn or direct law and then Airbus needs the pilot at the controls as much as DC-3 needs it.

[aguadalte]

Quote:
Now, to know if one simple (guarded) push button should be installed in the FBW Airbus in order to easily go back to the basic DIRECT LAW ... why not ?
Because pilots have their performance and limitations, too. If a pilot is so confused and behind the aeroplane that he allows it to enter protection, then he might start panicking and cut-out the protection that's doing it's job in mistaken belief that it's gone beserk. Mind you: no FBW protected aeroplane, be it Boeing, Airbus, Tupolev or Embraer, has been lost to stall or spiral dive in everyday operation yet. And protections are far easier to implement and more effective if you have FBW than classic controls.

That is not to say that protection makes anyone & his dog able to fly an Airbus. Staying out of protections still demands skill, concentration and foretought. And very seldom something goes seriously wrong and one ends up in altn or direct law and then Airbus needs the pilot at the controls as much as DC-3 needs it.

That is why:
I suggested a change in the software/logics of the use of the instinctive disconnection push button, located in the side stick, to "bring" the aircraft into a "status" (Alternate Law 1) which would bring the aircraft back to manual, although maintaining a great deal of protections. This would be a pilot friendly status, once he could effectively handle and override aircraft built-in protections in case a serious situation arises. Once the problem was solved, he could return to Normal Law (provided certain conditions met) by switching the Auto Pilot ON.:ugh:

[Lemurian]

Twenty-one years after the service entry of the first FBW airliner, followed byb the A330, 340, B777, the Falcon X, the A380 and soon the B787 and the A350, we still find advocates of the cables-and-pullies solution.
May I just remind them that cables can break, controls can be mis-set and that happened with dire consequences.
From the B777, there will not be another airliner with mechanical links either to the flight controls or the engines. Live with it or choose another trade.
But in fact, the whole thread is about Airbus-hating, however loud the hypocritical denials are...Going just a bit farther, it's all about not trusting the dastardly conspirative (?) French, sentiment illustrated here :
If (BIG IF) the accident report were to come out showing a fault in the
FBW/computer system on board, does anyone really think that FBW will be
eliminated from this model or any other model aircraft? Of course not. But, then again, I doubt very much the report would indicate that whether it was true or not.
For D-cate in particular, this piece, written by the US-ALPA with the help of NASA could be an eye-opener. Please note that on all these manoeuvres, the Airbus showed a better performance than the Boeing, but for "subjective reasons", the test pilots still prefer the Boeing...Go figure.
At least, they were quite honest about it.
Mind you: no FBW protected aeroplane, be it Boeing, Airbus, Tupolev or Embraer, has been lost to stall or spiral dive in everyday operation yet.
Either I read you wrong or you're wrong : The Gulf Air 320 off the coast of Bahrain and the Armavia IMO qualify for these characteristics.

[Enderby-Browne]

...it was published because Airbus deemed it necessary...
is not the same as "...it was published because Airbus deemed it an important safety issue..."

Much of what Airbus says, does and publishes is for Airbus' sake, first and foremost. Any consequent positive industry-safety repercussions are therefore a side-effect and it would be naïve in the extreme to delude oneself into thinking otherwise.

[fr8tmastr]

I think many are missing the point of FBW as it concerns AB/Boeing. Its not the FBY that's limiting anything, the electric wire just replaces the cable going to the actuator.
The AB/Boeing philosophy differs when it comes to the red button, to disconnect the computer, not the FBW.
I have also read about all the protections AB gives you, like stall over g etc. But nobody has mentioned it also limits roll rate and pitch rate. So say for instance the hypothetical flock of birds is dead ahead. A pilot given enough time might try to sharply turn to avoid. The airbus will turn just fine, but only at a certain roll rate, you want more? too bad. Is that a major concern? heck no, but its there, and that IMO is one of the reasons why the stick and rudder pilots are less happy with the AB FBW compared to the Boeing FBW.

[Clandestino]

Either I read you wrong or you're wrong : The Gulf Air 320 off the coast of Bahrain and the Armavia IMO qualify for these characteristics.

Ermmm.. nope, they don't. In spiral dive aeroplane attains severe nose down attitude either through massive sideslip towards the lower wing or by banking through 90 deg and pitching up (relative to aeroplane's coordinate sys, not ground) - example is Flash air accident. Airbus limits bank to 67 deg, but sidestick has to be out of neutral for banks greater than 33. Pitch is limited to 15 AND and 30 ANU. What Gulf Air and Armavia tought us is that disoriented pilots can stay within the limits and yet drive the fully serviceable aeroplane into water. Now there is food for thought for those who advocate "I-have-full-control" button. And Aquadealte, we we been here before just a couple days ago. Please do read your FCOM and understand it. I have expressed myself imprecisely first time, my apologies, but I do maintain that speed stabilities in altn law with reduced protections are not worthy of being called protections as they can be overriden. Your proposed red button would leave pilot able to overbank aeroplane, attain severe pitch-up or pitch down, stall it or overspeed it. In my book this isn't "maintaining a great deal of protections" at all.

[By George]

There is nothing wrong with Airbus or FBW technology, it does seem to me the interface between this technology is easier to understand and work with on a Boeing than an Airbus. How can anybody forget the early accidents on the A320, the Bangalore one, for example, where the crew were in 'open descent' with 'zero altitude' selected in the window. With an Airport elevation of 1800' they flew a perfectly serviceable aircraft into the ground, simply because they did not understand the mode they were in. I don't hate Airbuses I prefer Boeings.

[Dysag]

I think it's you who is being a little naïve.

What is the difference between "for Airbus'/Boeing's sake" and for safety's sake?

How long do you think a company in this business would last if it got a reputation for doing less than maximum to ensure the safety of its planes? Product liability lawyers would descend on them like locusts and devour everything.

The company could spend 30 years building a business and reputation only to lose it, with all the customers, overnight. Bankrupt. No chief executive could risk it.

[Lemurian]

I have also read about all the protections AB gives you, like stall over g etc. But nobody has mentioned it also limits roll rate and pitch rate. So say for instance the hypothetical flock of birds is dead ahead. A pilot given enough time might try to sharply turn to avoid. The airbus will turn just fine, but only at a certain roll rate, you want more? too bad. Is that a major concern? heck no, but its there, and that IMO is one of the reasons why the stick and rudder pilots are less happy with the AB FBW compared to the Boeing FBW.
You should get more information before you write something that's so patently wrong : The roll rate of a 737 is nowhere near what can be achieved with an A320.
As for avoidance, have a look into the BEA reports on a collision that was avoided near Montpellier between an A320 and a glider. The conditions were : The 320 under autopilot, descending toward the MPL pattern and suddenly a glider fills the windscreen ; the captain just punched the side-stick to the right to full deflection...roll rate achieved over 60°/s...the tip of the glider's fin nicked the outer underside of the A320 left wing and the glider pilot didn't even realise that he was millimeters from certain death.
Now put another type of airliner in the same situation, think of the effort needed to get out of A/P and the inertia of control cables, rods (you name it)...That exercise has been simulated and the result is exactly the opposite of your assertion.
The beauty of that set-up on the 'Bus is that the pilot can have a totally care-free handling of his aircraft within the limits of maximum performance, in the case above 67° of bank, without the hindrance of "increased yoke effort" some advocate as being the best solution.
Having flown both types, I certainly know where my preference is.

[fdr]

Hmmmm.... er,... a roll rate in excess of 180 degrees a second probably would beat the A320, and we have recorded that off a B737 before today. Now, the aircraft was aerodynamically stalled and with a substantial yaw rate, but... there you go. :}

Then again, the A320 has achieved some wild roll rates when the flight control laws got messed up a bit too, with the gain of the spoilers being incorrect for the TE flap configuration, the dreaded OEB 117 badness. Now it only got about 100 deg/sec on that, but still quite surprising.:)

:Ejust to put oil on the fire, the A320/330 have pretty nice controls, compared to the B737, most planes do. Heck even the B777 while possibly BAC's nicest equipment to date is not as nice on the control laws (in normal law) as the A330. System logic/crew interface is something altogether different.... ;). whatever floats your boat.

[CONF iture]

the captain just punched the side-stick to the right to full deflection...roll rate achieved over 60°/s...
Are you flying a Mirage ... Lemurian ?

That being said, it does not mean I share the view expressed by fr8tmastr in his last comment.

[Graybeard]

Since geese fly in formation at same exact altitude, to slipstream the one ahead, a sharp bank upon seeing a gaggle ahead would double the chance of one engine eating some, while reducing the chance of a multiple engine strike to near zero. Seems like a good gamble, if the FAs don't get upset.

GB

[NotPilotAtALL]

Hello,

Are you flying a Mirage ... Lemurian ?

Dunno wich Mirage fly Lemurian .. but for the Mirage 2000 .. 60°/S roll rate is peanuts :)

The aircraft has a redundant fly-by-wire automatic flight control system, providing a high degree of agility and easier handling, together with stability and precise control in all situations. Fighter's Airframe is naturally unstable, and so it is coupled with FBW commands to obtain the best agility; however, in override mode it is still possible to exceed a 270 deg/sec roll rate and allows the aircraft to reach 11 g (within the 12 g structural limit), instead of nine when engaged. The system is reliable with no known losses due to its failure.

Regards. http://smilies.sofrayt.com/%5E/a/bye.gif

[CONF iture]

Dunno wich Mirage fly Lemurian .. but for the Mirage 2000 .. 60°/S roll rate is peanuts
No doubt ... but in our airliner's world 270 is not that common and 60 must be 4 times what Lemurian's plane would deliver ...
It does not really help a demonstration when numbers are over exaggerated.
I have not much respect left for the BEA but not sure they would write such thing ...

[Lemurian]

or the Mirage 2000 .. 60°/S roll rate is peanuts
Please note that the value of 60°/s is achievable on direct law. On the incident I referred to,the rate was around 20 to 25°/S instantaneous. On a normal flight, the average is 15°/s.
a roll rate in excess of 180 degrees a second probably would beat the A320, and we have recorded that off a B737 before today. Now, the aircraft was aerodynamically stalled and with a substantial yaw rate, but... there you go
Please don't tell me it was normal OPS :)

[BEagle]

Since certain recent Airbus FBW 'events' appear to have been caused by shoddy maintenance organisations not following correct LRU installation requirements, would the ability to provide 'Direct Law on Demand' actually work under such circumstances?

Perhaps there needs to be some form of 'idiot proofing' to make it physically impossible for maintenance people to replace FBW LRUs incorrectly?

[CONF iture]

For D-cate in particular, this piece, written by the US-ALPA with the help of NASA could be an eye-opener. Please note that on all these manoeuvres, the Airbus showed a better performance than the Boeing, but for "subjective reasons", the test pilots still prefer the Boeing...Go figure.
Easy to figure out in a few words : keep it simple !

Not looking for an equipment which does miracles but just something that behaves with consistency, something easy to read, nothing more.

Said many times before : Put on the market a more humble version of the 320 and you’ll have a fantastic equipment.

And if FBW Airbus was that ultimate tool that Bernard Ziegler always claimed it was, it would show immensely in the accident / incident database …

[Safety Concerns]

Since certain recent Airbus FBW 'events' appear to have been caused by shoddy maintenance organisations not following correct LRU installation requirements

What are you referring too?

[NARVAL]

about Are you flying a Mirage ... Lemurian ?
The roll rate of the A320 in normal law is 15 degrees per second
That is with sidestick fully to the side. And only below 250 knots because as speed builds up above Va the full authority is progressively reduced. Luckily the A320 which met a glider was at 250 knots and flight level 80 or thereabout.
The captain used full rudder to increase roll rate and that probably helped a lot, but the plane never could exceed 15 degrees of bank per second. Which is quite fair for an airliner.
The problem which could happen (and did not in that case) would be the pilot flying deciding to bank left while the Captain taking over in a reflex action banks right…not much time for a briefing in those circumstances…maybe it is easier when you see those big hairy paws jumping on the yoke, instead of those unseen subtle movements behind the scenes…

[DC-ATE]

".....the pilot flying deciding to bank left while the Captain taking over in a reflex action banks right....."

Interesting question. Who wins in a conflict like that? The strongest, or does the Captain's sidestick have priority?

[night_flight99]

Narval stated:

"The problem which could happen (and did not in that case) would be the pilot flying deciding to bank left while the Captain taking over in a reflex action banks right…not much time for a briefing in those circumstances…maybe it is easier when you see those big hairy paws jumping on the yoke, instead of those unseen subtle movements behind the scenes…"

I think your logic is self defeating. In an airbus the standard procedure for taking control, and ensuring that you have control, is to press the red button and keep it pressed (whilst stating "I have control"). You then have absolute control and you decide which way you are going to turn. In a Boeing I would suggest that control would be dictated by whoever had the biggest biceps attached to those hairy paws! Could be a costly battle if they didn't agree which direction they were going don't you think?!

It is dis-appointing that threads such as this one have become another forum for the constant airbus v boeing slagging matches. This thread is about a serious accident where people have died. Instead of debating this in a factual way it becomes a forum for anonymous posters to display their prejudice. Could we not acknowledge that both Boeing and Airbus build generally excellent aircraft. Whilst they may have a different design philosophy they each have lots of strengths and fortunately very few weaknesses.

Some of the level of debate on this thread further erodes the credibility of Pprune as a forum for professional pilots. In order that each posting gains the appropriate credibility perhaps each poster could add their experience on type(s) before commenting. It might help separate the wheat from the chaff.

night_flight99

10,000 hours
(Current on 757 with 7,500 hours on 320 series).

[Dysag]

When someone posts "does the Captain's sidestick have priority?", I wonder where they have been these past 30 years.

You now have the answer.

The Airbus FBW family has sold 5 times as many as the your darling "fly-by-cable" DC-8, and it's now the industry standard, along with the latest Boeings. All those 777 (soon to be 787) pilots will agree. Wake up.
.

[DC-ATE]

Dysag -
"When someone posts "does the Captain's sidestick have priority?", I wonder where they have been these past 30 years.
You now have the answer.
The Airbus FBW family has sold 5 times as many as the your darling "fly-by-cable" DC-8, and it's now the industry standard, along with the latest Boeings. All those 777 (soon to be 787) pilots will agree. Wake up."


It just so happens I've been retired for nearly twenty years, and know absolutely nothing about the Airbus fleet. So, please don't tell me to "wake up". I thought my question had some merrit for someone who does not know.

Sorry if I offended you.

[Dysag]

Very sorry DC-ATE, I just hope I make it to 20 years in retirement. We need the experience of guys like you.

My beef is more with youngsters who think the 737 is modern. When we were young we reached for the stars, even if we fell short. Now the kids are very happy with the old junk.

Seems I owe you a beer, or three. By the way, I loved the DC-8, second only to the Convair 880/990.

But, seriously, FBW is now the standard, love it or hate it. It's the old fly-by-cable which is exotic.
.

[DC-ATE]

Dysag -
"Very sorry DC-ATE, I just hope I make it to 20 years in retirement. We need the experience of guys like you.
Seems I owe you a beer, or three. By the way, I loved the DC-8, second only to the Convair 880/990.
But, seriously, FBW is now the standard, love it or hate it. It's the old fly-by-cable which is exotic."

Thanks for the offer. Wish I drank beer...I'd collect!
Don't know 'bout that..."...loved the DC-8, second only to the Convair 880/990." The 990 was certainly the fastest over the fence! But, to each his own. I got my foot stuck between the armrest and the wall on an 880 on the way down as it depressurized. Fuselage, was kinda skinny!

I'd still like to know, being as how the side sticks are not 'connected', what happens when one pushes one way and the other guy pushes the other.

Thanks.

[Sky Wave]

DC ATE

If one pushes left and the other pushes right the result is zero.

I also believe that if they both push half left the result is the equivalent of one pilot pushing full left. The system sums the input of both controllers.

There is a sidestick priority button where by one pilot can override the other. It works on the basis that the last person to press the button gets priority.

SW

[Dysag]

The two sidestick inputs are normally summed by the computer, unless one side takes control by pressing the red button.

I just have a problem with youngsters who do think their old junk is great because they don't know any better.

Anyway, all modern planes are FBW, and there's no going back.

[md80fanatic]

Anyway, all modern planes are FBW, and there's no going back.

Agreed.

Before you know it they will all be FWP as well. That's "Flight without Pilot" for those who are wondering. FBW is just another step towards this, and yes there is no going back.

[CONF iture]

I think your logic is self defeating. In an airbus the standard procedure for taking control, and ensuring that you have control, is to press the red button and keep it pressed (whilst stating "I have control"). You then have absolute control and you decide which way you are going to turn
That's the procedure as it is written in the manuals and it looks good on paper, that’s also how it is teach in the simulator and that works just fine, but in real life, when the unexpected comes around, incident reports show that more often that we may think, the instinctive reflex is to simply grab the stick and move it resulting in a dual input … Only after a few seconds the red button is usually pressed.

Regarding the seriousness of the thread, it would be easier if guys pretending demonstrating something based on a specific report could restrain from publishing numbers nowhere to be seen in that very report …
Thanks for your attention Lemurian.

[Sonic Bam]

Okay I haven't seen anything new coming out of official sources recently. Has anybody else seen anything new?

The debate on ABS performance, ABS design theorum, ABS ops, ABS software heirarchy, ABS v BOE, etc., is great but what's going on with the accident investigation?

[PJ2]

DC-ATE;

This is likely in the thread earlier on but I'm just lighting up the computer after a few days away.

As Dysag says, the 320 sidestick inputs are summed but the important point is, they are summed algebraically.

Double sidestick input is a serious no-no in 320-type aircraft. It continues to occur however, at least as shown in flight data analysis. Usually it's a training-line indoc situation. That said, CONF iture, you are absolutely right in what really happens.

What some transitioning to fbw (Airbus style) initially may not appreciate because it may not be emphasizd in training is, the stick does not control ailerons/elevators; - it "requests" a roll-rate or a g-force. You may still recall a CWS mode - Control Wheel Steering - where, when engaged the airplane "stayed" in the last attitude set by the controls before engaging. That is essentially what fbw/sidestick control is. "No input, no change".

The autoflight-autothrust-flight director-flight management guidance computer systems are deeply intertwined with one another, all talking to each other. The non-moving thrust levers is a non-issue in such a system as the various flight modes look after thrust when the levers are set in their normal flying position, called the "CLB" or climb position. In this mode depending upon climb, cruise or descent, the engines will respond to airspeed, rate of climb or cruise speed commands from the FMGC, (Flight Management Guidance Computer).

For example, in a climb, with autothrust engaged but the a/c being manually flown, power is "on the elevator". That means power is adjusted by FADEC to match the thrust required to maintain an airspeed which is set by the cost index. Usually that's the old max continuous, about 92% N1. If one pulls back, the airspeed will bleed off only because 92% isn't sufficient thrust to keep both the climb and the speed, but power is still governed "by the elevator" in manual flight. To understand this better, take the opposite case where the rate of climb is reduced by gently pushing forward on the stick - the rate of climb will decrease, but without touching the thrust levers, the power will come back to match the speed being commanded by the FMGC.

In descent, the usual auto-flight modes are either "IDLE, OPEN DESCENT" or VNAV. VNAV is a calculated path that is managed by both the autothrust and autopilot - the speed is permitted to vary to take advantage of energy before bringing up the power from Idle.

"OPEN DESCENT" means the engine thrust is commanded to idle, (about 35% N1). The autothrust will not bring the power up until the selected altitude is captured. In this case, it is airspeed, not power, that is "on the elevators". To better understand this, if the sidestick is pulled back slightly, the airspeed will reduce and continue to do so until a minimum speed calculated by the flight augmentation computers using weight, angle-of-attack and CAS is reached, at which point the autothrust will revert from "IDLE" to "SPEED" and the "OPEN DESCENT" mode to "V/S", (to prevent a huge power increase to "chase" the originally targeted speed).

For this reason, in manual flight the flight directors must either be followed or turned off as they are indicating the "thinking" behind the autothrust system. If turned off, the autothrust reverts to the "SPEED" mode to again protect the airplane.

The other vertical modes are either variations on this theme or protections which guard against speed gain/loss or v/s excursions higher than certain values.

The sidestick is a very powerful little handle and is best flown gently, usually with the hand near the base to avoid large inputs.

As an aside, while the US Airways flight will have had "Alpha-prot", (stall protection), the fbw system would not have protected this airplane from stalling in this case because the engines were incapable of delivering TOGA (Takeoff/Go Around) power. In "Alpha-prot", the airplane is not pitched down to reduce the AoA - the only airplane response is to increase power, so Captain Sullenberger had to fly the speed indicated on the PFD, (Primary Flight Display) just above the alpha-max stall speed and by the initial indications, this is just what he did. See the graphic below - likely he would have flown between Vls and Alpha Prot but we'll know more after the reports.

http://img131.imageshack.us/img131/3290/pfdspeedtapenormlawig3.png

[DC-ATE]

Thank you Sky Wave, Dysag and PJ2 for the info on the side sticks. It still scares me!

Dysag - "I just have a problem with youngsters who do think their old junk is great because they don't know any better."

Well, I'm working on becoming an octogenarian. Not sure that qualifies me as a "youngster" or not. I feel like one anyway! Probably act like one at times as well. I just have a problem with some of this newer equipment that is slowly taking the pilot out of the loop. But, PLEASE don't call "my" DC-8 "old junk". Not while I'm still around anyway. Those and the Connies (along with a couple of others) took good care of me for thirty years.

[PJ2]

It still scares me!
Understand! But it works beautifully, even elegantly.

The '8 was my "first love" in the late 50's/early 60's and I had the good fortune and pleasure of a few thousand hours in it before transitioning to the 727, then the 1011, then the 76'.

Congratulations on the octagenarian goal - I would not have guessed that from your writing - like Dysag, I hope to make it as well.

Cheers, sir.

[DC-ATE]

PJ2 -
"Congratulations on the octagenarian goal - I would not have guessed that from your writing..."

Well, thank you. I'm not there yet; got a few to go, but hopefully, I'll make it. Even though airplanes might've given me the grey hairs I still have, it might have also given me some extra time.

Hope you all enjoy the "new age" of aviation. Good luck!

[aguadalte]

And Aquadealte, we we been here before just a couple days ago. Please do read your FCOM and understand it. I have expressed myself imprecisely first time, my apologies, but I do maintain that speed stabilities in altn law with reduced protections are not worthy of being called protections as they can be overriden. Your proposed red button would leave pilot able to overbank aeroplane, attain severe pitch-up or pitch down, stall it or overspeed it. In my book this isn't "maintaining a great deal of protections" at all.

I'm very sorry to disagree with you Clandestino, but:
I was "proposing" a "solution" that would put the pilot always in control. On the T7, pilots are always in control of the aircraft, because the system allows them to override protections...
One has to choose: either one has "your" type of protections and face the risk of being a "hostage" of an aircraft that flies the way it was designed/programmed to fly or, one has the chance to really have control of it flying a bird that allows those protections to be overridden.
I know what I would choose, if I had the chance to...:sad:

[Lemurian]

PJ2
As an aside, while the US Airways flight will have had "Alpha-prot", (stall protection), the fbw system would not have protected this airplane from stalling in this case because the engines were incapable of delivering TOGA (Takeoff/Go Around) power. In "Alpha-prot", the airplane is not pitched down to reduce the AoA - the only airplane response is to increase power, so Captain Sullenberger had to fly the speed indicated on the PFD, (Primary Flight Display) just above the alpha-max stall speed and by the initial indications

Sorry, but there is a rat here :
On the 320, "Alpha prot" is just an AoA protection : between "prot" and "max", the side stick commands alpha directly. However, the angle of attack will not exceed alpha max even if the pilot pulls the stick all the way back. If the pilot releases the stick, the airplane will return to alpha prot and stay there. That,regardless of the thrust you have available.
On the other hand, Alpha floor is the protection which is triggered with a high AoA and the airplane would go into a TOGA mode.
With the obvious lack of thrust, the system stays in AoA protection mode.
That's in all probability what happened to US 1549 as one of the NTSB press conferences mentioned that at their point of ditching, they were two knots below "prot" speed and just five knots above "alpha max" speed for their configuration.

[PJ2]

Lemurian;

Thank you - I should have remembered that and you are absolutely correct.

Cheers.

[NigelOnDraft]

PJ2 - sorry, but I do not recognise some of the A320 I fly from your post :ugh:

For example, in a climb, with autothrust engaged but the a/c being manually flown, power is "on the elevator". :ooh: In V/S maybe, but normal (OP) CLB modes it is juts like a Boeing or C152 - Climb Power and Pitch controls IAS...

....take the opposite case where the rate of climb is reduced by gently pushing forward on the stick - the rate of climb will decrease, but without touching the thrust levers, the power will come back to match the speed being commanded by the FMGC.Ditto - V/S only (and just as a Boeing).

As an aside, while the US Airways flight will have had "Alpha-prot", (stall protection), the fbw system would not have protected this airplane from stalling in this caseAgain, and as corrected above by Lemurian, not correct... IMHO ;)

so Captain Sullenberger had to fly the speed indicated on the PFD, (Primary Flight Display) just above the alpha-max stall speed Alpha Max / Alpha Prot are not speeds - they are Alpha values. VLS is a "speed"... and hence why in a turn or level off, the 2 Alpha values will increase, and potentially mask VLS.

I flew B757/767 prior A320 (and after A340)... The AP modes, once you "translate them" are fairly similar... the FBW protections only come into play when you exceed what you would fly in normal flight. Alpha Floor / Max only come into play with serious abuse, and after a Stick Shaker would have gone off on a Boeing. And in the 1549 case, I doubt any FBW "protections" were invoked, though as above, the Alpha Prot area seems to have been entered... if it was entered gently, Alpha Floor (TOGA) is only asked for "somewhere" in the Alhpa Prot area, and there are a couple of other reasons why it might not have been triggered here (<100R / Engine Out + Slats/Flaps). And even if it was triggered, seems it was not going to get anything :{

NoD

[DC-ATE]

It appears to me that you A-320 drivers can't agree on just what goes on with your FBW systems during various phases of flight.:bored:

[NARVAL]

Quote Night Flight99: I think your logic is self defeating. In an airbus the standard procedure for taking control, and ensuring that you have control, is to press the red button and keep it pressed (whilst stating "I have control").
Thank you for your answer. I did not go to the end of my reasoning (such as it is) wishing to be short…my mistake. I did not criticize the A320 which I have flown a few years, nor the FBW system, but the side stick in that case…as opposed to a yoke as in the 777 for example. You are right in your description of the priority system but I hope you do not imagine that with a glider filling the windscreen, somebody will say I have control (the captain did not) and push the priority button etc…it is all reflex action. In that case the captain acted on the sidestick laterally and the pilot in the pitch axis (down). I just tried to say that the copilot seing the hands of the captain jumping on the controls will stop doing anything (that’s the best decision in such cases).
As for the original subject of the thread, I shall wait with you for more information, feeling very sad for the crew, and having a thought too for the mechanics who work very well in Perpignan, as elsewhere. I flew many test flights there after heavy overhauls, plus painting jobs, and I can tell you that static ports, pitot tubes, angle of attack vanes were checked on the ground by the mechanics then by the crew before the flight.

[Graybeard]

"I can tell you that static ports, pitot tubes, angle of attack vanes were checked on the ground by the mechanics then by the crew before the flight."

Makes one wonder, then, if the letter from Airbus isn't a diversion..

GB

[Clandestino]

It appears to me that you A-320 drivers can't agree on just what goes on with your FBW systems during various phases of flight.

Keyword being "appears".

Not everyone discussing here is an Airbus driver, nor is discussion limited to bus drivers only.

Not everyone claiming to be Airbus driver actually is one.

Rules of the game are quite simple: anyone can have his say but the FCOM trumps all.

[DC-ATE]

Is "FCOM" your acronym for Flight Computer?

Are you an Airbus driver?

[Fargoo]

Is "FCOM" your acronym for Flight Computer?

Are you an Airbus driver?

FCOM = Flight Crew Operating Manual.

[BEagle]

Flight Crew Operating Manual

[Pull what]

But there again Beagle you never flew the Airbus, did you?

[CONF iture]

It appears to me that you A-320 drivers can't agree on just what goes on with your FBW systems during various phases of flight.
You are correct Sir.

The overall system is more complex than we think.
FCOM is fine (or is it ... ?)
Flight Crew Training Manual provides instructive reading.
In flight, a lot happens but time does not always allow to analyse properly.
Best option is the Flight simulator to take advantage of the frozen position and try to understand what's going on ?

There are so many possible combinations depending if you're flying manually or not, A/THR ON or OFF, FD ON or OFF, if you follow them or not, there are the numerous mode reversions, the mode protections ... and altitude AGL interfer as well ...

Anyway, a lot to check in your Flight Management Annunciator if you want to have a chance to monitor all these subtleties. No wonder not so much spare time to monitor the geese outside ...

Among the Airbus drivers, the are many things we are made aware one day but cannot remember days further. It takes a lot of continuous reading and Pprune is a good tool for that purpose. No one has to believe what's written on this site but it's a good place to dig deeper and many opportunities for learning or ... reminding.

The sidestick is a very powerful little handle and is best flown gently, usually with the hand near the base to avoid large inputs
Absolutely correct, it's what many guys do, it's what I personally do and get comfortable with ... but still, I don't think I should as the day I need to press the red button and keep it pressed I won't be in my usual setting with the armrest becoming useless.

Question :
Anyone made an estimate regarding the GW of US1549. I was thinking somewhere between 60 and 65 tons ?

[DC-ATE]

Sorry.....don't know how to make those pretty blue boxes with the quote in them.

CONF iture -
"Originally Posted by DC-ATE
It appears to me that you A-320 drivers can't agree on just what goes on with your FBW systems during various phases of flight.
You are correct Sir.
The overall system is more complex than we think.
FCOM is fine (or is it ... ?)
Flight Crew Training Manual provides instructive reading.
In flight, a lot happens but time does not always allow to analyse properly.
Best option is the Flight simulator to take advantage of the frozen position and try to understand what's going on ?
There are so many possible combinations depending if you're flying manually or not, A/THR ON or OFF, FD ON or OFF, if you follow them or not, there are the numerous mode reversions, the mode protections ... and altitude AGL interfer as well ...
Anyway, a lot to check in your Flight Management Annunciator if you want to have a chance to monitor all these subtleties. No wonder not so much spare time to monitor the geese outside ..."


Thank you for that. It just makes me all that more uncomfortable thinking about the whole system. What ever happened to K.I.S.S.?

I flew the 737-300 for a spell and had to constantly tell the Co-Pilot (sorry, First Officer) to get his head out of the cockpit and FLY the airplane!

[Dysag]

CONF iture, I'd vote for 65000kg. I'm not sure which type of tons you refer to!


DC-ATE: re KISS.

In the 70's you probably had an Operations Manual and a Flight Manual. Easy to distinguish.
Then some bright chap invented the Flight Crew Operating Manual. Since when there's been a generation of trainees wondering... now is that the ops manual or the flight manual...

[CONF iture]

Thank you for that. It just makes me all that more uncomfortable thinking about the whole system. What ever happened to K.I.S.S.?

I flew the 737-300 for a spell and had to constantly tell the Co-Pilot (sorry, First Officer) to get his head out of the cockpit and FLY the airplane!
Not sure what KISS is for exactly but I can guess the concept behind and approve it.
Nowadays, one of the most common advice you will hear during a sim training is : Read your FMA ! (in other words : stay inside)

Thanks Dysag, tonnes would be probably more appropriate ...

[vanHorck]

No news from the French authorities still?

[DC-ATE]

Not sure what KISS is for exactly but I can guess the concept behind and approve it.


Nothing personal but..........Keep it Simple, Stupid.

[TyroPicard]

The sidestick is a very powerful little handle and is best flown gently, usually with the hand near the base to avoid large inputs.

I disagree with your hand position. The sidestick is designed to be held with the thumb on top, putting your index finger comfortably near the Transmit switch - if you can't fly and transmit simultaneously you are not in control of the situation. (Ask Sully). And a small movement is far more difficult to achieve holding the sidestick near the base - there is a breakout force to overcome, which is easier with a longer lever. (Ask the TP's).
Regards
TP (Not a TP)

[PJ2]

TyroPicard;

Yes, the stick is designed to fit the hand. That said, the hand doesn't necessarily stay in one position for all regimes. At any one time the hand can slide down the stick to "dampen" inputs for example in turbulence on approach, and move further up for slightly more authority when needed - there's no hard/fast rule, nor should there be.

Also, I disagree with your comment on the hand position & transmit button statement "as a rule", but yes, that certainly works when required as in the Hudson River case. Normally, the PNF is doing the radio work and cockpit discipline would mandate that only one pilot do the communications work unless the captain deems that circumstances require otherwise, of course.

The point of the original comment is, there is a tendency to "stir the pot" with large stick movements, particularly in turbulence, even to the point where the stops are reached. That's not the way to fly fbw aircraft as the computers and control surfaces are already doing their best to maintain the last position requested by the stick. Airbus recommends small corrections, not large ones.

[Sonic Bam]

Okay I haven't seen anything new coming out of official sources recently. Has anybody else seen anything new?

The debate on ABS performance, ABS design theorum, ABS ops, ABS software heirarchy, ABS v BOE, etc., is great but what's going on with the accident investigation?
Sorry to be a bore but ....

Has anybody got any "Rumours and News" that has anything to do with this accident?

[PJ2]

DC-ATE;

Sometimes discussing techniques and even how the 320 works is like watching a roomful of economists come to an agreement. Sometimes they're talking about the same thing but the language gets in the way and sometimes mistakes in knowledge, judgement or memory are made. The airplane "behind the panel" is complex but flying it is not.

NoD is correct in his responses as far as they go, (including the similarity to Boeing in V/S in the circumstances described and the Alpha modes as Lemurian indicates), but in descent, the airplane operates as described and this is an important point because in "IDLE - OPEN DESCENT" mode, the airplane does not operate like a Boeing.

The speed is indeed "on the elevator" in descent, (thank you again NoD for the clarification in the climb case - my year-and-a-half retirement is catching up with me I think!) and the engine power will not increase until and unless the altitude set in the altitude window on the Flight Control Unit panel, (glareshield panel), is captured.

If the pilot pulls back slightly on the stick, the speed will decrease and continue to do so until reaching a speed just above the "lowest selectable" speed, (Vls in the graphic) at which time the descent mode will change from Idle-Open Descent to Vertical Speed and the autothrust reverts to "SPEED". This "mode reversion" occurs in other autothrust-manual flight circumstances as part of the protections under "Normal (fbw) Law".

This design was the result of an accident at Bangalore, India in which the altitude selected was set too low to be captured during the approach and the autothrust stayed in the "Idle - Open Descent" mode until ground contact. The Flight Director system was similarly change so that if either or both FD's were switched off, the A/T system reverted to SPEED, to bring the power up. Previous to this accident, this was not the case.

The prevention of this accident was straightforward, and the same as any other airplane - take over the airplane, in this case by pushing the thrust levers forward, commanding a thrust increase from the engines to arrest the rate of descent - no different than the Boeing or a C152. The crew failed to do this and the airplane performed exactly as commanded by the crew.

Normally in descent when approaching the cleared altitude, one reaches for the throttles and pushes them up as a natural reaction (on the '8 for example), but not in the 320 (and Boeing with A/T's on, for that matter) - the autothrust will bring up the engines when the altitude is captured. But if the airplane is leveled off above the selected altitude as described, the 320's engines will not accelerate. To demonstrate the speed decay a bit I would ask transition line indoc students on the airplane to fly manually and "level off" just above the altitude selected in the FCU window. When the speed began to decay a few knots, one could pull the speed knob which maintained the current speed or one could turn the F/D's off to revert to the SPEED mode. The importance of this was to show why IDLE-OPEN DESCENT mode was never to be used below 1000ft AGL and if it did occur, how to handle it - fly the 320 like a 152.

In my view, airline managments and training departments alike do not emphasize nearly enough the fact that the 320 is just another airplane and can and should be disconnected entirely from the automation - it hand-flies beautifully. I know crews today are still reluctant to disengage the autothrust because they are not taught properly how to and are reluctant to grab a mitt-full of throttle and push when needed. It's still an airplane - clearly, Scully is keenly aware of that fact.

The airplane is indeed complex and difficult to explain in text in a forum - afer one flies the aircraft for a period of time, say six months, it becomes second nature.

[CONF iture]

The Flight Director system was similarly change so that if either or both FD's were switched off, the A/T system reverted to SPEED, to bring the power up. Previous to this accident, this was not the case.
Actually, both FD's need to be switched off.
Switching off only one of them won't allow the system to revert to SPEED mode ... That's one of the catches !

And for Sonic Bam, still nothing on the horizon ...

[DC-ATE]

Thanks for all that PJ2.

The more I read, the happier I am that I'm outta there!

[Dysag]

People born in the early 1900s could probably figure out how a steam engine works.

People under 30 don't even ask "how does my cellphone send photos?" It's obviously not necessary to know.

And in between, there's the rest of us.

I grew up knowing how my car worked. After all, I had to take it apart a lot. Now I have no idea, it's just too full of black boxes.

It's not an easy adjustment to make, and when your life depends on stuff working properly, it can be uncomfortable.

But just because we can't take it apart to see how it works, it's not necessarily exotic any more.

The 4700 Airbus A318/319/320/321/330/340/380s in service have a flight control system which is now the norm, not the exception.

[ExSp33db1rd]

..........have a flight control system which is now the norm, not the exception.

Good points, and even steam engines exploded and scalded people, nothings' perfect, I appreciate DC-ATE's points of view - same era - but we have to accept that life moves on. Not easy.

[TyroPicard]

PJ2
The sidestick has a fixed breakout force. This is easier to overcome, with more control, if your hand is near the top - simple levers/moments theory.
A "small" movement at the base is a "larger" movement at the top - the same "small" movement at the top is a "smaller" movement at the base.
It ain't rocket surgery.

[NigelOnDraft]

PJ2... You really are making me get back in the books here ;)

If the pilot pulls back slightly on the stick, the speed will decrease and continue to do so until reaching a speed just above the "lowest selectable" speed, (Vls in the graphic) at which time the descent mode will change from Idle-Open Descent to Vertical Speed and the autothrust reverts to "SPEED". This "mode reversion" occurs in other autothrust-manual flight circumstances as part of the protections under "Normal (fbw) Law".The Reversion you quote is correct for older A320 series aircraft... newer or modified ones just turn the FDs off and go to SPEED.

What I do disagree with is This "mode reversion" occurs in other autothrust-manual flight circumstances as part of the protections under "Normal (fbw) Law".IMHO this is nothing to do with FBW... It can occur in any law in which FDs are available, and is part of the FMS (Flight Management / Guidance System).

...and this is an important point because in "IDLE - OPEN DESCENT" mode, the airplane does not operate like a BoeingMy "recollection" (which maybe wrong) is that (Idle) OP DES is pretty much like FLCH is a B757/767...

NoD

[Lemurian]

All this discussion about mode reversions is a bit confusing and re-inforces the prejudiced one's bias aginst modern flight management systems.
Be it a Airbus, or an Embraer, a Boeing...or any brand one cares to mention, the principles are the same as those that have been used since flight controls have been used :
A pilot has at his disposal a pitch control and an engine. Full stop.
The rest is a matter of flight path management, which in turn breaks down to "Energy Management". That is, exactly, what piloting is about.
From that principle, a pilot can elect to have :

either a fixed engine output - idle, climb, max continuous, TOGA - and control the desired speed with the pitch control, or
follow a fixed vertical path of his choice -vertical speed, Vnav, or an electric glide path of any sort, in which case the speed is controlled by the pitch control and the engine is used to control the vertical trajectory. (There is nothing new, nothing hidden lurking behind the pilot as that is the way we're taught to fly an ILS).

Now, a pilot is supposed to know what he wants, isn't he ?
either he flies "raw data" and he does it exactly like he would a Cessna 172, a DC-8 or a 777,
or he uses the accuracy brought by the flight director, he will get the help of the command bars, but first he has to sign a contract with the FD : "I want to fly with the thrust at hand, you help me control the speed I want with the stick/yoke. As a proof of your agreement I want you to show me , on the FMA, a fixed thrust mode (Idle / Clb / Max Cont / TOGA ) and the Open mode / FLT CHG.
If I need a fixed path, I want to see on the FMA that you'll take care of the engine, therefore I want to see "THRust" and a confirmation of the path you'll help me follow : VNav, GP...
I said there was a contract. "If I don't follow the pitch command bar, you are allowed to "revert" to a mode that will keep our energy management on the safe side, and tell me at once what you've done through an alert and a clearly stated mode change."

That is all there it is about Flight management, and, to me, these "reversions" are quite logical and straightforward.
I might also add that in circumstances where the "FD or A/P acts funny", the -very easy - solution is "BACK TO BASICS" AND REPROGRAM THE DAMN THING ! In most occasions, the pilot has been distracted and hasn't followed the terms of the original contract.

[DC-ATE]

Dysag -

People born in the early 1900s could probably figure out how a steam engine works.

People under 30 don't even ask "how does my cellphone send photos?" It's obviously not necessary to know.

And in between, there's the rest of us.

I grew up knowing how my car worked. After all, I had to take it apart a lot. Now I have no idea, it's just too full of black boxes.

It's not an easy adjustment to make, and when your life depends on stuff working properly, it can be uncomfortable.

But just because we can't take it apart to see how it works, it's not necessarily exotic any more.

The 4700 Airbus A318/319/320/321/330/340/380s in service have a flight control system which is now the norm, not the exception.


Well, Dysag, and others: You boys stick with your new fangled toys and I'll just go along with my old needle/ball and airspeed and hopefully, we'll all get to wherever it is we're going safely.

[CONF iture]

PJ2
The sidestick has a fixed breakout force. This is easier to overcome, with more control, if your hand is near the top - simple levers/moments theory.
A "small" movement at the base is a "larger" movement at the top - the same "small" movement at the top is a "smaller" movement at the base.
It ain't rocket surgery.
I follow your logic here, but still, I'd like to disagree on it :
Except when AP is engaged, I don't really feel any breakout force, there is a neutral point for sure but that's it.
There is more precision to be gained when using the tip of 2 fingers than when soliciting the wrist.
Just my own appreciation, but I feel more comfortable the way PJ2 put it than the way you describe it, even if I do think you are correct.

Anyway, it does not hurt talking of these things as the BEA still does not communicate on Perpignan ... at least directly.

During this time, the report on the Etihad 346 in TLS is now available in English ... but people still remain silent even if the BEA report is a blatant inconsistency !

[Teddy Robinson]

CONF .. agreed .. PIO is the likely result of trying to fly it like a flight sim toy..

[PJ2]

NoD;
Yeah, me too, (back in the books, that is).
My "recollection" (which maybe wrong) is that (Idle) OP DES is pretty much like FLCH is a B757/767...
Yes, except (I believe), if you level off a Boeing anywhere in a descent but not at the Selected Altitude, the power will come up to maintain the speed in FLCH because the Speed mode is always engaged. In Idle-Open Descent the power will not come up - not until ALT*/ALT because "Idle" is engaged, not Speed.

On the mode reversion, thanks. I think on the first point, we're talking about the above point - in descent in Idle-Open, the airplane will decelerate until Vls + 4 at which time the A/T system reverts to Speed - I couldn't recall if the F/D's were removed or not.

TyroPicard;

I understand your point in terms of small movements at the base, large up top. The sidesticks I've used do not seem to have a breakaway resistance and thus the method suggested for turbulence works academically and it works in practise. Clearly one never lets the airplane get away with anything one doesn't want!, but that said, the slight, "felt" resistance is precisely what makes the method work well. It keeps forces at the bottom of the stick from moving the stick either too rapidly or too far. It's a judgement thing after all. Some sticks are more resistant than others, just as some Thrust Levers move very easily, others not quite so - at least in my experience - (we got our first 320's in the late 80's and still have them plus 319's & 321's, -the latter of which I have not flown).

CONF iture - oh, okay, I thought the F/D system had been modified so that if one F/D was switched off the AT reverted to Speed - thanks. In any case, for a TCAS Resolution Warning, our SOPs require both F/D's to be switched off so that "Speed" is the available mode.

I could never understand why Airbus just didn't install one pushbutton for the F/D's if both either had to be on or off, but, like the answer I got in 1991 when I asked (foolishly, at the time, given AB's willingness to listen to customers and users), something else about the VNAV system, the reply in a heavy French accent was, "..zat ees zee whay zee hairplan ees design". Nothing further was forthcoming - they opened up to pilots and customers somewhat after a few..."incidents".

Anyway - passing time while the current theory regarding paint and sensors awaits confirmation or ?

[J.O.]

"..zat ees zee whay zee hairplan ees design".

PJ2:

Was that ET by chance? :p I remember asking him a similar question. It was also explained that the independent FD buttons were to provide the necessary redundancy in the case of a total loss of one of the FMGCs.

[PJ2]

Hi J.O. - no, that was Charlie Nagel in Toronto and it was '92, not '91 (guess what else goes after technical knowledge!), but ET gave us a really fine lecture-presentation-lesson on "Why We Designed the 320 the Way We Did" at a Flight Safety Symposium put on by USAir (now US Airways) in Pittsburgh a few years ago - it was the most entertaining, delightful and educational talk a pilot could have heard about the 320 at the time.

Thanks for the comment on the FD's - makes sense, just like the airplane, if one keeps with it long enough!

[CONF iture]

PJ2, not too long ago, you and I could not agree on an issue regarding the RETARD call out philosophy - here (http://www.pprune.org/rumours-news/351097-ten-indicted-over-tam-crash-4.html#post4575935)
My point was based on a recommendation addressed to Airbus, a recommendation that Airbus decided not to follow ...

I could never understand why Airbus just didn't install one pushbutton for the F/D's if both either had to be on or off, but, like the answer I got in 1991 when I asked (foolishly, at the time, given AB's willingness to listen to customers and users), something else about the VNAV system, the reply in a heavy French accent was, "..zat ees zee whay zee hairplan ees design". Nothing further was forthcoming - they opened up to pilots and customers somewhat after a few..."incidents".

I make this point because what you mention here was exactly one of the 62 recommendations made after the Bangalore accident in 1990.
No need to say Airbus decided not to follow it ...

[PJ2]

CONF iture;

Yes, and another recommendation early in the design stage and which is, I believe, a legal matter with some of the AB engineers involved, is the V/S - FPA indication which, until long after Strasbourg, was not modified to be more clear. I suspect there are a number of other items which may or may not be part of the list of 62.

Would these changes have prevented an accident?

Perhaps, perhaps not; we can't rewind and play the tape over to see.

As I said then and say now, thorough, knowledgable training and equally thorough checking by knowledgable standards pilots can be cited in each of these accidents just as much as human factors causes may be found in faulty design. I know of none of the 320 accidents in which this one factor is not at work. Of course, the Habsheim captain ought to have known better from the get-go.

I have personally seen the VS/FPA error made on an approach into YHZ06 but it was caught almost immediately because the FMA was being carefully monitored as per our training. Yes, the smaller numbers and no (or tiny) decimal did not highlight the error but the FMA did. That was emphasized from Day One - if it's not on the FMA, the airplane isn't doing it, and if it is on the FMA, make sure it's what you want and expect - if not, re-program or disconnect everything. To emphasize, I know and have flown with many, many crews on the 320 series and 330/340 series who are literally afraid to disconnect the autothrust and don't even know how. That is partially a professional issue in terms of seeking the answer and then practising but it is also a standards and training issue which does not ensure that your crews are completely at home in all regimes of automation and manual flight. To me that was and remains, an unacceptable level of competence for an airline crew but that position though widely held among aircrews who flew the airplane, was outvoted by the bean counters and managers infatuated with the notion that "automation will do everything because that's what we've paid for".

To return to the Congonhas accident in re the Retard call, I would agree but the origin of the call was never intended to remind the pilots of the thrust lever position on the ground but in the air at 20, or 30ft depending upon autoland engaged or not, as the thrust levers do not move back to IDLE on their own as do some (but not all) Boeings. Certainly leaving one thrust lever in the "Full thrust commanded" position would not be a reasonable thing for an engineer to anticipate and design against, would it? Are not taught "from the cradle" to pull the throttle(s) off to land?, (to be sure, no sarcasm intended here CONF iture).

On the autobraking, spoiler deployment, reverse availability issue in CONF 3, after the Lufthansa accident at Warsaw, the design was changed and for a good reason. In fact long before that change came out and long before the Warsaw accident, 320 pilots knew how to get oleo-compression/wheelspin so reverse and spoilers were available in a CONF FULL, slippery runway-smooth landing circumstance.

I'm not about to hold onto allegiances where they are inappropriate - that isn't how safety work is done of course, (I know you know this). But I submit the above for consideration - training, training, training, and once the airplane is understood it is as straightforward to operate as any other design with it's own foibles, compromises and traps for young players.

That doesn't mean the safety message in these accidents isn't dismissed or plain missed. It isn't news to you that no design is without the above problems so I won't spend a second on the "perfect" airplane.

Quick question - Why do you suppose AB did not implement one, two, some, all, of the recommendations after Bangalore? Would you agree that AB has responded to the CONF 3 and FPA issues? As an A320 pilot, what other issues do you see that are both outstanding and a safety trap?

The dialogue is much appreciated - I fully realize it is off-topic but this is interesting and it readies the thread for awaited information on the accident that began this discussion.

PJ2

[ExSp33db1rd]

Well, Dysag, and others: You boys stick with your new fangled toys and I'll just go along with my old needle/ball and airspeed and hopefully, we'll all get to wherever it is we're going safely.


Took off in my 1200 cc VW powered microlight ( LSA to the USA's ) the other day, got airborne, no airspeed - yeah, pitot cover still in place. Not proud of it, but it happened. No airspeed, but not stalling either, so drop the nose a bit to increase the margin, level off, set cruise rpm, turn downwind - and don't touch anything ! Line up, reduce to approach rpm, keep the nose on the numbers - no problem.

( with a stall speed of 35 kts. and 1100 mtrs of smooth tarmac - hardly a challenge, really, once one had got over the initial shock )

Wonder what a FADEC or EICAS or FMS might have done ?

Sorry, slightly off thread I guess !

[Lemurian]

ExS33db1rd,

Wonder what a FADEC or EICAS or FMS might have done ?
I'm quite surprised at the question. What is the speed check we do during the takeoff roll for ?

Grizzled,
Edited. Don't encourage the village idiots.

[ExSp33db1rd]

What is the speed check we do during the takeoff roll for ?


Good point, in fact I've abbreviated the whole event, even to the point of not explaining how I'd got into that situation in the first place - a good ( actually poor of course ) example of not re-starting a check list when interrupted, details unimportant - in fact my comment of no airspeed should have read wrong airspeed, 'cos strangely, tho' blocked by a cotton sleeve - not plastic - the airspeed did in fact build on application of power, and the power weight ratio is such that a Vr of about 40 kts comes up very quickly, so rapid increase of apparent airspeed wasn't an immediate concern, and it wasn't until the airspeed needle continued to build, right around to full scale deflection of the ASI, approx 180kts, with a Vne of 104 kts, that I realised what had happened. Can't explain the high airspeed as opposed to no airspeed, but haven't spent a lot of time thinking about that aspect yet, more concerned with why I fell into a trap. I guess I was lucky that the IAS was so wildly in error, had it been a mere 5 - 10 kts ......... you work it out.

[grizzled]

As soon as I typed that line I figured (even hoped?) this would happen.

And I'm happy to see that Delia is sticking to the traditional "finely grated reggiano." Here in The Sandbox a lot of restaurants have started placing great slabs of parmesan on top of the salad, and it just doesn't work. The bits of reggiano have to be small enough that your tongue and tatebuds are getting little zaps of it -- not great wads.

Grizz

[CONF iture]

PJ2,

So much food for thought in your last post.

I think the following will mainly resume what is on my mind :

You advocate : Training, training, training.
Bernard Ziegler position : My airplane is perfect, even my doorman could fly it.
What a contrast !?

Of course YOU are the one to be correct, and coming from the father of the 320 technology, his comment is plain arrogance, way out of touch from the reality, and clearly reflects the unwillingness to accept any criticism, as constructive it aims to be.
Never publicly acknowledge a possible weak link in the selected technical options.
Stick to your gun. Keep modification to the minimum but do not admit any error and certainly not any fault in the initial concept.

Not familiar with the CONF 3 issue regarding Warsaw accident, so I’ll have to go in the research mode first … but I can illustrate my statement through the VS-FPA episode.

According to the BEA report, one contributory factor to the Air Inter accident was the lack of difference between VS and FPA selection on the FCU as well as the absence of numeric value in the FMA only true reflection of the FCU entered figure.
Airbus did follow the recommendation this time … but you may not be aware that during the last trial on Ste-Odile in late 2007, Bernard Ziegler defended the idea that the pilots deliberately set HDG-VS at a negative value of 3600 ft / min and therefore the conception of the FCU had nothing to do with the accident and was just fine as it was before modification.
Airbus and BZ have been relaxed of any charge, which is, in my view, still correct.
Even if the initial conception was not ideal, it was of course not designed in a harmful way.


A quick word on the RETARD call out logic.

Are not taught "from the cradle" to pull the throttle(s) off to land?Absolutely correct, but the same applies to the rotation : Would we need a PULL call out at Vr ?
My words to Airbus and there are not only mine : No need for any RETARD call out , but if you choose to go with it, do not fool the crew by canceling it before ALL thrust levers comply to the request, especially when the consequences are huge.

Reports confirm Congonhas is not an isolated case, something, bizarre, I concede, is repeating on the Airbus side, so just go with the very simple recommendation to be applied and improve the chance the next crew will identify their omission before it’s getting catastrophic one more time.