HazelNuts39

BOAC,
After re-reading your post #811 I apologize for missing the point you're making.

Organfreak

And I apologize for missing the points that almost everyone is making!

safetypee

Clandestino, your conclusion “Both pilots commented that speed display was faulty” (#819) assumes a particular interpretation. The absence of airspeed does not imply URA as depicted by the abnormal drill. Also, if the speed display had disappeared off-scale low this may have reinforced the idea of a stall because of the decreasing speed.
Note similar difficulties in determining an UAS situation in the previous events.

Re “Stall...recovery...in...normal...law...was...never...trained”.
You may have overlooked the nuance of my hypothesis, in that because stall ‘wasn’t possible’ in normal law there was a mental conflict with a stall warning and low speed / decreasing speed, before any appreciation (if at all) that the aircraft was in Alt Law. The erroneous mental model might also have been reinforced by the concern over turbulence from adjacent Cbs.
Thus whether trained or not, the PF chose a course of action closest to the perceived situation based on previous experiences / bias. This was to fly a stall recovery based on a false mental model, and with both supportive and conflicting indications of that model.

Therefore the dismissal of the ‘alternative view’ (#816) might be premature. This may involve fundamental surprise - when events occur that challenge existing beliefs. Here there is a strong temptation to find situational solutions which fit the information (check Pprune), and thereby miss the opportunity to learn from a wider (fundamental) view of the accident.

jcjeant

Of course I disagree completely the idea that you made ​​of justice
BEA conclusions and recommendations are there for improve safety
DFDR and CVR were witnesses at the scene of the accident
As in any trial .. if there are witnesses .. the judge and lawyers want to hear their testimony .. not for make recommendations .. but for find if anyone or anything can be responsible of the accident
Now .. if the judges in charge of the AF447 accident don't request (or are denied to acces) the DFDR and CVR .. it's a denial of fair justice ( put away two important witnesses)
In fact .. without the DFDR and CVR ... a tria is useless or at least a truncated trial
A simple example is that of a bus , train or truck accident
They are also equipped with a black box
And that will be part of the documents examined by judicial experts and judges

Lyman

IMHO it takes quite a stretch of imagination to apply designation "under control" to stalled airliner.

Yet you acknowledge 447 was STALLED all the way down; pilot kept the nose up, lowered it, and raised it, roll was responsive though excursive, and yaw was certainly in control.

Explain? Was she fully stalled, partially? Any stall that is recovered with normal controls proves there was control in the STALL. Any STALL. airbus has video of a recovery that proves this.

Lyman

Safetypee.

The logical conclusion suggested by the data show the pilot acting within a perception of Normal Law controlling. Likewise PNF. Nothing contradictory is observed.

The script is that ECAM showed the degraded law immediately, pilot should have seen it, therefore they knew Law changed. There is nothing to show this. The only data we have shows the earliest they knew speeds were lost is at 2:10:16, and the earliest they knew about AL (and NOT AL2) is six seconds later, at 2:10:22. Since the PF acknowledged neither call, we can't conclude, (unless a PPRuNe poster) that he knew about UAS or law change. Throughout the accident time frame.

"We've lost the speeds?.." 2:10:16. This is an odd call, since it means plural. Did they lose "all indications" NO. Or did they lose a bug? Two bugs? Vs? It is not the appropriate recognition of UAS, and it certainly is unaccompanied with any drill. Yet most here assume it is a recognition of UAS? How's that?

2:10:09: "what's that?" BEA claims that is an exclamation by PNF in response to STALL warn. I take it as such, and rhetorical at that. Pilot starts his STALL recovery, and later, PNF says; "you are climbing..." now that might merely mean that PNF accepts PF's STALL recovery, and notices that he is climbing, not acceptable as Approach to Stall recovery was trained at the time.... It is quite possible both pilots see and accept the low speed, Stall Warn, and the recovery maneuver as necessary.

So yes, safetypee, there is not only reason to entertain the theory, but evidence to explain it as you do.

RetiredF4

BEA FR 2.3.3 Stall warning (operation and identification)
Furthermore, in alternate or direct laws as featured in the manufacturer’s manual (FCOM), the stall warning is described as being the combination of the aural warning, the illumination of the Master Warning light on the FCU and the indication on the speed tape, displayed as a red and black strip (Vsw). No clear mention of the buffet phenomenon is ever made.

BEA FR 3.1 Findings
The crew, progressively becoming de-structured, likely never understood that it was faced with a “simple” loss of three sources of airspeed information.


BEA FR 3.1 Findings
The aeroplane went into a sustained stall, signalled by the stall warning and strong buffet. Despite these persistent symptoms, the crew never understood that they were stalling and consequently never applied a recovery manoeuvre. The combination of the ergonomics of the warning design, the conditions in which airline pilots are trained and exposed to stalls during their professional training and the process of recurrent training does not generate the expected behaviour in any acceptable reliable way.

In its current form, recognizing the stall warning, even associated with buffet, supposes that the crew accords a minimum level of “legitimacy” to it. This then supposes sufficient previous experience of stalls, a minimum of cognitive availability and understanding of the situation, knowledge of the aeroplane (and its protection modes) and its flight physics. An examination of the current training for airline pilots does not, in general, provide convincing indications of the building and maintenance of the associated skills

I hope that helps in the discussion.

mm43

Clandestino;An excellent point.

Though the PNF called Alternate Law, there doesn't appear to have been any recognition of the different "flavors", or was there?

At 02:10:17 the PNF stated "Alternate law protections (law/low/lo)" and as we are not privy to the annunciation, particularly the last word, neither can we be sure what the PF actually heard and/or interpreted. I offer that what the PNF may have said in English/French was, "Alternate law, protections allé (gone)". If that was the case, the PNF certainly had reason to "panic" when he noted the actions of the PF, who was ostensibly the PIC. Or was this "panic" also partly that of "fundamental surprise" brought about by the complete lack of CRM being demonstrated.

The Three Mile Island nuclear accident alluded to by safetypee and the "fundamental surprise" aspects the nuclear industry learned from that, could equally have words like "aviation industry" and "Airbus Industrie" substituted in the document to demonstrate that maybe there is a fuse burning somewhere.

We all know of the saying, "Turkeys don't vote for Christmas". Problem is that turkeys don't know about Christmas, and therefore voting for or against it is not an issue.

The same can not be said for all aspects of the Aviation Industry, and a good reason to look again at some of the fundamental issues that have become hidden because they have up until now not been an issue.

BOAC

- realise, if you will - they 'controlled' the a/c into a stall and kept it there with the CONTROLS.

'Out of control' means no ability to manouevre the a/c deliberately. There is ample evidence they had that, in spades. I'll grant you 'out of control' in that they had no idea how to control the aircraft - for a variety of reasons. Then each time they 'did it right' the aircraft sadly told them they had 'done it wrong'.

Ever flown a Porteous loop? Look it up. In an incipient spin -yes. Out of control - no.

RetiredF4

How could he know?

Bolding by me.


2.2.5 Aeroplane behaviour in reconfiguration laws
Alternate 2B law represents a specific case of flight control law reconfiguration. In fact, it occurs when the flight control computers have rejected the three ADR’s. It has the specific characteristic of being associated with the loss of computation and display of the limit speeds. The high and low speed protections that exist in normal law, and sometimes in a reduced manner (high and low speed stability) in alternate law, are lost. There is however no explicit indication, apart from the red SPD LIM flag next to the speed tape (on the ECAM for example), of the level of alternate law that the aeroplane is in. The ECAM message associated with the reconfiguration to alternate law, of whatever type, indicates “PROT LOST”. However, not all of the protections are lost, since the load factor protection remains available, and reduced protections can also exist. The precise identification of the consequences of a reconfiguration in alternate law is thus complicated.
In alternate 2 law, the longitudinal control law remains a load factor law and the lateral control law is a direct law. In the specific case of alternate 2B law, some coefficients used in the longitudinal flight control law become speed-independent and are set for the maximum speed for the aeroplane configuration (330 kt in clean configuration). This hardly modifies the behaviour of the aeroplane in comparison to normal law, but can nevertheless induce an unusual response dynamic when the aeroplane has an abnormally low speed for the configuration.

mm43

Yes, the PNF certainly knew; he read the ECAM. Did he impart the same message to the PF, or did the PF simply not hear it, along with the other audio clues.

The subtile changes to the PFD, as pointed out in the BEA's report, do not appear to have warranted a comment by either pilot. The PF may have conceded this point when he made the comment, "I have no more displays". But I suspect he really was inferring that he couldn't interpret what was being displayed.

Lyman

"In alternate 2 law, the longitudinal control law remains a load factor law and the lateral control law is a direct law. In the specific case of alternate 2B law, some coefficients used in the longitudinal flight control law become speed-independent and are set for the maximum speed for the aeroplane configuration (330 kt in clean configuration). This hardly modifies the behaviour of the aeroplane in comparison to normal law, but can nevertheless induce an unusual response dynamic when the aeroplane has an abnormally low speed for the configuration."

"Alternate 2B law represents a specific case of flight control law reconfiguration. In fact, it occurs when the flight control computers have rejected the three ADR’s. It has the specific characteristic of being associated with the loss of computation and display of the limit speeds


Franzl:
Do you have advice on the abnormal responses (unusual) in this regard? It is why I brought up the possibility that PNF may have been referring to bug speeds lost? Eg. "we've lost the speeds"


Lyman:
"We've lost the speeds?.." 2:10:16. This is an odd call, since it means plural. Did they lose "all indications" NO. Or did they lose a bug? Two bugs? Vs? It is not the appropriate recognition of UAS, and it certainly is unaccompanied with any drill. Yet most here assume it is a recognition of UAS? How's that?


mm43

"The subtile changes to the PFD, as pointed out in the BEA's report, do not appear to have warranted a comment by either pilot. The PF may have conceded this point when he made the comment, "I have no more displays". But I suspect he really was inferring that he couldn't interpret what was being displayed."

He did not. How do you get "Je ne comprends pas" from "J'ai riens vitesses?"

RetiredF4

According to BEA he didn´t know and couldn´t know the different flavors, as it is not comunicated by the system. How come you think otherwise now?

Lyman

"....can induce an unusual response dynamic" when the airplane has an abnormally low speed for the configuration..."

Can this response be a stubborn climb?

Clandestino

How hard is reading the CVR transcript? Seems not very strenuous to me.

It absolutely does. Let me help you a bit, phrase "If the safe conduct of the of the flight is impacted" is a part of the what you call "drill". No need to go to 5° pitch and climb thrust if crew ascertains there is no immediate threat, but procedure must be performed. It wasn't.

Remind me: how did the previous events ended? What was the factor X that made the difference in outcome? Perchance that only two cases of triggering the stall warning due to crew actions were recorded? That in both cases crews reacted to stall warning by pushing the sticks?

You only pull to back stop when recovering from inverted stall. Perish the thought, mental model of stall recovery was nearer to non-existant than false as stall was never recognized.

I'll gladly pass the option to learn from the aces of the base.

Tough. You might find better understanding on lawyers' forum.

As I said, if you have the vested interest in misusing the recorded data, I won't wish you good luck with your case.

They are not covered by the Annex 13 and all the neat stuff we came up with while trying to improve the aviation safety.

Yup. Pitch control went to extremes to satisfy right stick G demand, yet it couldn't as speed was waaay below 1.58 Vs.

Another dazzling display of inability to understand DFDR graphs. Spoilers, ailerons and rudder followed sidestick/yaw damper inputs and flapped like mad, yet the effect on roll and yaw was negligible, as expected in stall.

PF said that there's no good display of the speed. How can one say things he is not aware of while being conscious?

...by pulling on the stick once again. No good.

Is pre-stall buffet really so exotic it warrants special mention in the manuals of the aeroplanes possessing it or we perchance require the aeroplanes lacking it to be equipped with artificial means of its simulation?

You are overgeneralizing, which is understandable as you choose to disregard the cases of A330 /340 UAS where crews either reacted properly to stall warning, or at very least did nothing. So survived.

Fully agree.

After the aeroplane exited envelope, they had no means to control the roll & yaw and only option available in pitch was down. Unfortunately, they did not take it.

Way I see it, if your nose doesn't come up when you pull the stik, you have no positive control.

Exactly.

I have once pulled up too gently, then pushed too hard and flicked off the top of the loop. Does it count?

Small chance. Go read the report... no, don't read, just have a look at the picture on page 39.

Why should he know? WIWOA*, drill was to treat every degradation to alternate law as the worst case. What difference would make if it were ALT1? Low speed stability is overridable, especially so with full back stick.

*When I Was On Airbus

mm43

Simply because the PNF said, "Alternate law protections ...?..". The undecipherable word is possibly "lost/gone" and said either in English or French. I am giving the PNF some credit for adding some "interpretation" to the basic "Alternate law".

CONF iture

QF72 A330
Just short memory ... or desire to look the other way ?
BTW, still no fix, just the same OEB to try to beat the dysfunction ...

jcjeant

So for you .. the judges have vested interests and so they will misusing the recorded data ?
That's new for me .. I suppose you have references ..
As I said before you have a weird idea of what is justice .. but it's your right to think like this ...
Annex 13 what it is worth but can't be seen as a shield
It is not universally respected, and that law is often violated (even in the case of AF447)
On the other hand .. the (superiors) interests of justice(remind .. it's not only some tons of scrap .. it's also 228 dead) can even prevail over this annex (there have been previous)
As you said so .. welcome to the real world
End of the disgression

CONF iture

According to the BEA, the electric stop was at 11 degrees up.
But DozyWannabe, who sat once in a A320 simulator, pretends the A320 airplane has a limitation for the autotrim at 3 degrees. Maybe he knows after all ... but better if he produces the Reference.
True that not everything is black on white in the Airbus documentation dedicated to the pilot ...

Turbine D

Stalls

Lots of talk about stalls:
A 727-200, after leaving JFK was involved in a stall accident when the pitot tubes iced over. Responding inappropriately to the erroneous Air Data information, showing an increasing airspeed, altitude, and rate-of-climb, the co-pilot, who was flying the airplane, continued to raise the nose until the warning went off at FL230. The stick shaker then activated at 420 kts (as recorded on the FDR.) The F/O then misinterpreted the buffet as Mach buffet, as the airspeed was likewise erroneously increasing, and applied yet more back force to the controls. The stall warning continued as the F/O said “There’s that Mach buffet, guess we’ll have to pull it up,” followed by the Capt’s response “Pull it up.” Two seconds later, the aircraft began descending (in a stall) at 15,000 fpm. 43 seconds later, the crew transmitted a Mayday - we’re descending through 12. Five seconds later, the final CVR dialog was spoken by the co-pilot “Pull now....Pull; that’s it.”

So - was this a Deep Stall accident? The answer is decidedly No, if you define a Deep Stall as an airplane attitude and flight condition from which the pilot is unable to recover using pitch and thrust. During flight tests, the airplane was stalled at AOAs of 25 degrees and recovered by relaxing the pull force on the control column. With the use of thrust during recovery, altitude lost was limited to about 2000 ft. Data shows that the AOA can be decreased and stall recovery effected by pushing on the column.
The answer is Yes if you eliminate the “unable to recover” aspect of a “true” Deep Stall. This airplane entered a pilot induced Deep Stall condition and remained in that condition from inducement by the F/O until impact. The crew fixated on the Air Data indications and ignored their Attitude references, which, at 30 degrees nose up, showed an attitude about 25 degrees greater than normal. The co-pilot maintained, with the Capt’s concurrence, heavy back pressure from before entering the stall, through the entire 25,000 ft descent, until impact with the ground. The whole event took 83 seconds. They could have recovered, according to the NTSB report, for up to 40 seconds after entering the stall, by merely - as a minimum - relaxing back pressure on the control column.
Does this sound similar to AF447 except for the altitude and the absence of FBW electronics and sidesticks in the 727?

The F-104 had considerable gyroscopic effect from the single rotating engine. This, combined with the anhedral in the wings, caused a rather violent lateral oscillation in the deep-stall region which eventually resulted in a nose slice bringing the AOA down and allowing recovery.
Chuck Yeager's later flight in the NF-104A (1967 with the rocket) demonstrated the true deep stall characteristics of the F-104 configuration. On this zoom mission, where the engine was shut down at high altitude, the RPM had dropped to almost zero thus negating the lateral oscillation normally associated with an F-104 at high AOA. The airplane stabilized in a deep stall and stayed there all the way down. (Chuck ejected at 7,000 ft.)

I think Gums pointed this out: The F-16 exhibits a deep stall characteristic, probably related to its aft cg (about 6% unstable subsonically) since it does not have a T-tail. Spin tests showed that it could be recovered from the deep stall by rocking the airplane fore and aft with the stick.

The latest in stall recovery: The current fighters (F-22, F-35) "enter and leave" the deep stall region routinely using engine thrust vectoring.