RetiredF4

You need to know what systems have failed, it has to be communicated by the system..

corect, but in the context we are discussing here utter nonsense. The first reason you mention yourself, you should always stay in the envelope. Protections are not there to motivate to reckless flying and testing out the envelope protections. The second reason is neglecting the vital point, how to take care to stay in the envelope.

I would always fly like all protections are gone. I had none for twenty years, and i wouldnīt rely on one now. And i hope that the pilots i fly with do the same. But as some of the laws and sublaws influence the FBW system also on the input output level, we have to know those limitations to understand, what the system can do and canīt do, and how the manual inputs are translated to the flightcontrols. Example that comes to mind is "roll direct" (overall Law Alternate, but in roll direct).

The degraded laws canīt be reduced to the fact protections yes or no, those changes are the least important one, because the flight should always be kept within the flight envelope and protections should not be tested. But the degradation might have influence on the handling depending on the systems affected by the degradation, and thus on the asociated flight control inputs.

Itīs not a question to stay inside the envelope, itīs a question how to do that. and therefore the functionality and the limitations of the input system are relevant and have to be present, to do the right thing to stay inside that envelope.

Those "flat" statements" are comparable to an instructor who acts like answering to his student pilot, when asked how to handle flying and arising problems:
Cobbler, stick to your trade.

Most points of this list would have stayed what they had been in the beginning, unnoticed sidenotes and excursions. You are the guy who has a great part in leading the discussions to these points again and again, who zeroīs in on those points and distracts the thread OT.

Most participating posters here show their interest in discussing the circumstances of this accident without focusing blame or making comparisons between different manufacturers. You have a valuable part in it concerning your knowledge as a software engineer. But your jumping in with the A v B theme and your permanent war with one or two posters motivated out of the past is hindering in these discussions. I would know nothing about this A v B stuff, as i have none expierience in B and none worth to mention in A and i donīt care, who builds the aircraft i go on leave, as long as it is safe, but thanks to you i know now more negative touched stuff about it than i ever would have liked to know.

End of discussion for me.

AlphaZuluRomeo

CONF iture, you're quibbling here. The correct sentence would be "Alpha Floor, where the system commands maximum thrust to help preventing stall."

I agree that Alpha floor => TOGA is to have the max performance regarding altitude. But I disagree on the "only".
Indeed, with Alpha floor => TOGA active, if you keep your current altitude (or path), then you may gain speed on this path => lower AoA => go farther from the stall risk.

Clandestino

They read and understand their manuals.

Good advice, wrong address.

Not this MacMillan. Do you perchance live in a country where googlesearch of "Who killed MacMillan?" is blocked? Try with: FlightSafety Foundation, Accident prevention, November 1989.

Simples. It was cutting edge at the time. Not any more. Nowadays it is proven, reliable and well known system - except for those who don't want to know.

Real world engineers know that no improvement comes without costs, either strictly financial or improvement in one area is inseparable from degradation in other. It's a tough world outside.

Real world physics demands that aeroplane has enough energy for sustained flight, no appeal against that allowed or useful. Lack of energy results in either decay of airspeed and increase of AoA untill aerodynamic stall or depletion of potential gravitational energy and collision with ground or objects attached to it, such as trees. Alpha protection at Habsheim prevented first scenario from occurring but lack of energy made the second one inevitable. Such a situation is colloquially known as low & slow. Contrary to some uninformed beliefs, FBW does not include distortion-of-Newtonian-physics protection.

So? Procedures based on attitude gauges (two big, one small) were not followed despite competent authorities' belief that following them is way to dig out oneself out of UAS was many times validated in real world.

Another remarkable thing is how the CM2's reaction to stall warning is to keep quiet yet always to pull, eventually pulling to back stop. One never pulls to backstop on airborne Airbus unless performing GPWS or low level windshear escape, none of which are applicable at FL350.

Legally, he never had command of the aircraft and would have never had it unless both capt and SFO were incapacitated. If under "command" is meant knowledge and skills needed to successfully fly the aeroplane, he lacked that at the time of the accident.

Simples. Air data based protections ned reliable air data to work reliably. They were not available. That's what is meant by very technical term "Alternate law".

Correct, but there is even simpler way to make autotrim work in the opposite direction: push the stick.

It's cheaper that way, when the fuel is cheap and aircraft/crew time expensive. Anyway, it's not that critical as maximum operating mach has inbuilt margin, which must not be used up deliberately.

In the real world, achieving 17.9°pitch at cruise altitude when the target is 5° is not normal or tolerable. That it can turn out to be fatal is not news to some of us. Hopefully, most.

Protection limits are displayed all the time on PFD when protections are available. Attitude protections marks are replaced with yellow X signs when lost, alpha prot and alpha max speeds disappear from the speed tape. IMHO, clear enough for anyone who knows his aeroplane sufficiently and pays attention to speed and attitude.

If the crew (C) has no knowledge (R) to draw upon, all the management (M) is useless.

You shouldn't be thinking that. Protection activation is very serious safety occurrence and more often than not is bound to be investigated by the independent air safety investigative body, not just airline safety dept. In the first world, at least.

Errr... similar but not quite the same. There are radical differences in protections use between Viper and 'Bus. On Viper one would go regularly to full back stick in ACT (or real stuff) to get maximum rate turn, either G or lift limited. On Airbus, intentional activation of alpha prot by pulling full back stick is reserved only for GPWS or low level windshear escape and you have to do some pretty bad planing or be once in a 10E4 lifetimes unlucky to get there. DozyWannabe seemingly cannot get the message through, the one that all Airbus pilots must be familiar with: protections absolutely do not interfere with normal flying, they stop the pilot from doing something that he shouldn't be doing.

I think you are now talking about dumbing down the pilot training down to level of system operators, which is impossible. Pilots have it covered on the very first page of any Airbus manual, the one stating this manual does not cover what the basic airmanship should. Airbus manual is not meant to teach people how to fly, but to acquaint the proficient pilot with the peculiarities of the aeroplane. If your protection is dependent on the correct functioning of a system and system goes AWOL, knowing you will lose the protection is not just basic airmanship. It is basic intelligence.

Could be, but chances are very low. It is not unreliable airspeed but rather ADC DISAGREE that is either result of pitot, static or AoA disagreement, with spurious stall warning effected only in the last case. It would be possible to think that "unreliable airspeed" implies "unreliable stall warning" but it would take quite a lot of creative misunderstanding and magical thinking to get there.

While the internal dialog of the doomed crew is matter of considerable conjecture even for experts, CVR and FDR readouts show utter confusion and tragically maladjusted reactions. Stall warning goes uncommented, except for CM1 comment "Qu’est-ce que c’est que įa ?" It did go off a few times while commander was back in cockpit, yet even he did not consider worthy of commenting on it. CM1 recognizes and verbalizes that speed indications are lost, only to exclaim "Fais attention ā ta vitesse!" (watch your speed!) ten seconds later. We are looking at the three pilots who went into territories totally unknown to them, got thoroughly scared and managed to kill themselves and all on board through panicky reaction. How and how much did the aeroplane, regulators, airline and pilots themselves contributed to tragic inability to cope with minor malfunction is something that has to be resolved. Last thing I want to see in the final report is that BEA was unable to determine what made the crew's situational awareness fall to pieces and confession "I killed Bonin" twentysomething years later.

EDIT:

Tens of thousands pilots do it every day. Staying inside envelope we call "flying", excursions are called "falling".

AlphaZuluRomeo

gums,

Comparing the Viper and the Airbii is possible (they both fly) but one must take care.
If I undertood you correctly, you're not happy because of the multiple potential levels of degradation of the FBW in the airliner. And you base your PoV on the much simpler (in term of number of possibilities) of the Viper.
Let's not forget that the Viper cannot be flown without FBW computation (i.e. no Direct law, nor mechanical reversion), due to its instable nature. But the pilot can eject.
On the other hand, one doesn't eject from an airliner. But in the same time the airliner is stable, hence it can be flown without FBW computation (i.e. Direct law in pitch or in mechanical reversion).

RetiredF4

You sure did notice, that we are discussing the "falling" here in this thread.

Lyman

Remember, Airbus had all the data BEA had when BEA released the famous memo: "No new mechanical issues have been found..."

1 . Stall warning fluctuates in Stall, it was intermittent, and can lead to confusion.


Doze: Short question, one word necessary only. Is Overspeed protection active in Alternate Law 2 ?

CONF iture

Negative.
Thrust won’t prevent stall – Stall is question of AoA not of thrust.
You could have TOGA and still stall if the airplane is not alpha limited - AF447

I do maintain :
Alpha Floor does not command maximum thrust to prevent stall, but only to provide maximum performance in term of altitude gain when high AoA are reached and want to be maintained.

But you can still comment the following part, that’s where DozyWannabe is in difficulty :
You can permanently disable the autothrust function, and therefore lose Alpha Floor, but you can still maintain full back stick without stalling, IDLE thrust. The system will maintain Alpha Max for you - NO STALL - Going down YES - BUT NO STALL - STILL FLYING

averow

A very cogent and succinct summary if there ever was one.

If I am driving my high-tech car down a highway and all of the electronic displays vanish from the screen and cruise (throttle) control drops off, what do I do ?

I sit bolt upright in my chair, put my right foot on the gas pedal, keep the car moving at what seems to be the same speed based on traffic around me and other cues. Then and only then do I troubleshoot.

It seems that flying reasonable (and easily obtained) pitch and power settings might have done the same for AF 447 when things became very confusing very quickly....

DozyWannabe

We're discussing the accident timeline as a whole, and that includes how the aircraft went from "flying" to "falling". Consequently Clandestino's point remains valid - if the PF had stayed within the envelope then there wouldn't be 8 pages (and counting) of discussion on the subject.

Also - I'm not talking A v B, except on the specific occasions when Boeing's FBW implementation has been brought up - and even then it's only to compare and contrast as opposed to being a fanboy for either. If I've been more prolific than I should be (and believe me that does concern me) then it has only been to answer the wilder theories that keep coming - we know journalists frequently peruse this site and I don't want misinformation showing up in the press during the slow news days of summer.

No.

[EDIT : A "soft" Overspeed protection is available in Alt1, but it can be overridden by pilot input - if you're attempting to suggest that the PF got mixed up between Alt1 and Alt2, then I don't think it's likely - because the inputs made were sufficient to override the "soft" protection. ]

I posted that exact functionality several times - no difficulty at all, and it's a feature - not a bug. However for that to work, the aircraft systems must be in Normal Law, and AF447 wasn't.

Also, the permanent autothrust disable command (hold down disconnect for >45s) is only intended for use in the case of erratic autothrust behaviour stemming from a failure - as far as I know this has never happened on the line.

[EDIT :
Did you see this (my bold)?

The two ways of decreasing AoA are to reduce pitch and/or increase airspeed. If reduction of pitch is undesirable, the only way you can reduce AoA is to increase airspeed by increasing thrust.

So AZR is in fact correct in general terms. Airspeed (and by extension thrust) indirectly influence the AoA, but they are crucial factors in its determination.

]


I've got to say thanks to Clandestino - being a line pilot he can bring anecdotal experience from the line into the discussion in a way that I can't - and also has the clout to be more brutally honest than I feel I can get away with:

Lyman

Doze, bear with me. Is it active in ALTERNATE LAW 1?

Clandestino. I have trouble finding any mistakes in your voluminous posts, and will grant that your knowledge of the system is exquisite.

bubbers44. You have a pov, namely that some actions of this crew failed airmanship 101.

Nice and tidy, "basic airmanship". Sounds nice. If what one wants is basic airmanship on the Bus flight deck, you will have a long wait. It is a myth.

One does not enter the cockpit as an airman on these aircraft possessed only of basic skills. That is absurd. You are victim to the myth that a "concierge" may pilot hese airplanes. That was always a lie. The system was not designed for a low time bug smasher. It was designed for a systems operator, who is also a flyer.

Well and good. 99.999999% of the time. At a time when things get difficult, the system's good traits disappear, and one is left with a potential bag of snakes that cannot be flown intuitively. Again, systems. But in trouble, the system morphs. Its alterations are taught, briefly, and trained, haphazardly, for why waste money on a system whose dependability is on a par with other fleets? Herein lies the snake.

447 is a textbook case of the best plans of mice and men gang aft agley. It is fair to mention the other 30 odd occurrences of UAS and the nice safe though disparate outcomes....

This accident started with an aircraft in autoflight experiencing trouble. At first, merely turbulence, then temperature fluctuations, air mass inconsistencies, and other cascading problems that caught the complete attention of the crew probably only when it was too late. I have said from my first post here, that the accident had its beginnings in the last seconds of autoflight, and the first seconds of manual control.

Unfamiliar. I've said that whilst flying, and always had a voice on the radio, or next to me to add some grok to the conditions. No such resource for the crew of 447, of that we know. The crew was unfamiliar. With the conditions, with each other, and with the aircraft.

To claim simplistically that this tragedy was due incompetence in the seats is outrageous, even obscene.

In blaming, the community finds a lightning rod. A way to pitch their own shortcomings and fears into the bag that is clutched by the dead. It is cruel, and unwarranted.

It's a big bag, and dozens of characters have their guilty mitts on it. If one wants to say that the chain of tragedy starts with the PF's first aft stick, fine, I say that too. Consider the conditions, and take a long look at yourself, and your surroundings. A simple explanation can be correct, but well short of the truth...

AlphaZuluRomeo

CONF iture,

"Thrust won’t prevent stall – Stall is question of AoA not of thrust."
Yes, thank you, I'm aware of that. Thrust alone won't prevent stall. I never said otherwise.

Now, do you disagree with the following?
For an aircraft following a given path (alt stable, descending or climbing), and all other parameters equal, more thrust = more speed = less AoA
(not when stalled, but Alpha Floor engages itself before stalling)


Lyman,

"Doze: Short question, one word necessary only. Is Overspeed protection active in Alternate Law 2 ?"
DW posted the requested "one word answer", but I'm wondering: Were U kidding when asking? ALT LAW 2 was because of a failure of the speed measurement, detected by the aircraft systems. How would a protection based on speed then be active?

GarageYears

Wrong.

This accident started when the crew on the flight deck decided NOT to re-route around the weather in front of them, unlike the other flights taking similar routes that night. Everything that followed is consequential to that simple choice - go through or around. Have we forgotten this?

I have sat back and read the last umpteen posts and it seems there are two camps, both polarized in position - Airbus fans and Airbus not-fans. I am struggling to find a not-fan that is a 'bus driver, i.e. those that actually know the systems and characteristics of the airplane family all seem pretty happy with it. As with all complex things there could be improvements, but I have seen none posited that would be earth-shattering and would have prevented this accident.

So far I have seen no plausible explanation for the zoom-climb (call it what you will...) that caused the stall. The stick-stirring at least in my book is a result of an "oh-" moment that caught the PF by surprise and without the tools in his toolbox to cope. The fact that "doing nothing" (or next to nothing - a minor roll correction at worst) would have saved PPRuNE many thousands of posts and was the closest thing to the right action is a sad thought, but the only one that makes sense.

We can continue to explore this or that protection in this or that sub-mode, but in my book if you reach a condition that relies on that protection to avoid disaster, well some level of disaster has already occurred. In the same way the stall warning is supposed to alert the crew BEFORE a stall actually occurs, the protections are there to prevent the aircraft achieving an attitude that is computed to threaten the aircraft. I don't believe any of the protection limits are restrictive in any normal flight mode? If the protections have gone away due to the loss of a critical input (i.e. airspeed) the airplane does not fall out the sky - it simply becomes wholly dependent on the PF, whereas before it was dependent on the PF+protections. In other words the most important "protection" is the PF. The problem here is that particular protection also seems to have "gone out to lunch" - unfortunately the airplane doesn't function too well once that happens.

Lyman

Interesting how one can bemoan polarities whilst contributing mightily to them...

I am not wrong, which in itself is no great accomplishment, merely a reading whilst in an objective state. I describe the Met that caused what was likely the procuring cause of the problem, you repeat me, and then claim I am wrong? No wonder there are ten thousand posts.

Narrowing one's view is a poor substitute for open discussion. There will be no one "conclusion" it is in the nature of holy cheese....

Ahh...weather. Catchall numero uno.....

GarageYears

Lyman - I beg to differ. You state the conditions they FLEW INTO as the precipitous start - it was flying INTO the conditions AT ALL that was wrong from the beginning.

If they had diverted, no accident. Quiet different - but I bet you'll argue. You do, you see?

They didn't divert - they flew into the soup you describe. The soup in itself was not a killer - it was the response of the crew and most everything they did from then on that did them in - not the aircraft.

Lyman

GY,

I absolutely see your point. The problem is in trying to make narrow what is a very wide cascade. Besides, we do not know that a simple mechanical malfunction of the flight computer didn't start the ball rolling. The weather itself, by most accounts, was not sufficiently fierce to have been necessarily the cause of upset. By upset, I mean a sufficient encounter to cause auto to be lost. To, it is seemingly benign enough to cause many here to comment on the less than skillful effects of its handling.

Divert? How far? I thought "flying into a cell" had been discarded... And if they did not blunder into the cell, how did turbulence cause this accident? Are you saying that it was not "ICE"? BEA issued its favorite (and only) theory long ago. The likelihood that some glitch, heretofore unexplained, will be announced is zero, pet theories get discarded in the final, virtually never.

OK465

High speed stability IS still available with only 1 functional ADR (i.e. 2 ADR's on the 'fritz') in ALT2.

MacMillan told me.

In the incident under discussion, the 'plumbing' caused temporary problems with all 3 ADR's, which 'latched' ALT 2...

When an ADR is recovered, is high speed stability regained?

If 2 ADR's are recovered, is low speed stability regained?

Is VLS redisplayed?

A little help here on the academic side only, please...

Lyman

Howdy do...

When an ADR is recovered, is high speed stability regained?

hello......

Doze

[EDIT : A "soft" Overspeed protection is available in Alt1, but it can be overridden by pilot input - if you're attempting to suggest that the PF got mixed up between Alt1 and Alt2, then I don't think it's likely - because the inputs made were sufficient to override the "soft" protection. ]

I am attempting to suggest that the aircraft got it mixed up.... If the aircraft is in zoom, having been triggered by Overspeed, does the THS trim automatically, or is elevator sufficient and does that explain the "hiatus" of the THS in the initial ascent? Why would the Protection need AUTOTRIM? (Trying to think like a programmer....) BTW, how would NU inputs by the PILOT defeat similar input from the soft protection, they too would be commanding Nose UP. Or is there a nose up protection from additives? He said, facetiously....

Also, if active (they were), would flight directors show the order, explaining PF's "following the climb"? Pushing the bars up into the zoom trajectory?

If in zoom, (entering zoom), would the solution trigger STALLSTALL? "What was that?" Now, how do I explain the lack of OVERSPEED alert? Because I think it unlikely that the initial STSALLSTALL was produced by the pilot's inputs, he is limited in PITCH. The aircraft 'protection pilot' is not.....

Otto and Bonin, too many chefs spoil the souffle?

Doze?

roulishollandais

02:10:05 alt2 law
02:10:08 "alt2 law" displayed on ECAM
02:10:22 "alt2 law" said by the PM to the PF

also PM needed 14 seconds TO READ THAT very short message!

CRAZY ECAM!

F-16 did not need that ! Would you imagine gums with his LEF and that ECAM?!!!

Airbus system is a bad counterfeit of the very first F-16 FBW system never achieved ?!!!

Lyman

Bonjour roulishollandais.

Three seconds to display the change in Law to the pilots, yet the man whose job it is to Monitor, takes an additional fourteen seconds. He strikes me as a little bit anal, and actually pretty good so far at his charge. Hmm. He is eager to nudge the PF in re: some other things, so perhaps he thought it unimportant until "later". For the moment, then, can we imagine how long fourteen seconds is under the circumstances? Is it at least possible then, that PF believes NORMAL is the LAW, at first? His displays are not recorded, and certainly the ECAM has received the LAW degrade data? How can we be sure? Certainly we know that the first they know for sure, is at PM's remark.

All the while the a/c is turning the pebbles over re: speeds, and the direction the logic is pointing, the pilots must be aware? What is the prompt that the a/c is mulling over some extremely critical decisions? Is there one? Something like, "HORN, WAKE UP flyboy, get your ess together, possible controls LAW rethink in process"? The timeline and chronology is for some reason sparse......?

Old airline bromide. Flying: "99 percent boredom, one percent panic...."
eh?

AlphaZuluRomeo

Seriously, Lyman, again?

If the aircraft is in zoom, having been triggered by Overspeed, then the FDR has recorded the overspeed condition.

As we know that no overspeed condition was recorded on flight AF447, trying to explain the events as the consequence of an overspeed is null and void.