AF447 wreckage found

[RWA]

Quoting Lonewolf_50:-

RWA, from the discussions over at tech log, Alpha Protect works in normal law.

Blowed if I know for certain, Lonewolf - I'd be surprised if even 'Bus-drivers' are absolutely certain, from the extraordinarily-complex documentation, what the systems may do or not do in different circumstances. But, according to this, in Alternate Law 'Alpha Floor' is lost, but AoA monitoring continues:-

http://www.smartcockpit.com/data/pdf...light_Laws.pdf

Quoting EMIT:-

Remark EMIT: IF after all, the PF did not himself STEER the a/c into the zoom climb, then at least he should have seen the pitch change to 15 degr nose up, a very inappropriate pitch at that altitude, and should have tried to steer that pitch down to a normal value of 2 or 3 degrees above the horizon. This was not done, a lot of backstick was maintained.

I fear that you're now just making things up, EMIT. 'A lot of backstick' was not applied, leave alone 'maintained' - even the BEA states that the PF did exactly what he should have done, applied forward stick, controlled any tendencies to roll, and levelled the aeroplane out:-

"At 2 h 10 min 16, the PNF said "so, we’ve lost the speeds" then "alternate law […]". The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb. The PF made nose-down control inputs and alternately left and right roll inputs. The vertical speed, which had reached 7,000 ft/min, dropped to 700 ft/min and the roll varied between 12 degrees right and 10 degrees left."

No 'backstick' at all?

[iceman50]

RWA

You are now the one making things up.

A lot of backstick' was not applied, leave alone 'maintained' - even the BEA states that the PF did exactly what he should have done, applied forward stick, controlled any tendencies to roll, and levelled the aeroplane out:-

Your previous quote from post 1994

"From 2 h 10 min 05 , the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall warning sounded twice in a row.

My bolding and colour change.

Pray tell why if the aircraft was in Alpha Prot it would increase the AOA by pitching UP!! Plus in ALT LAW 1/2 Alpha Prot is not available. Roll is direct which is why there could have been slight over-controlling in roll. High AOA and High speed protections could also have been lost. Once the AOA had been sensed greater than 30 degrees Abnormal Attitude Law would have been in place to allow recovery of the A/C. (Pitch control alternate law with no protections as mentioned before and Roll would now be direct - NO auto-trim from that point on and Manual Pitch trim required. This would be displayed on the PFD.)

You are like a dog with a bone and need to just relax and wait for further information to be given out by the BEA. With your continued misinformation and lack of understanding you seem to be trying to prove your own conspiracy theory.

[Zorin_75]

But, according to this, in Alternate Law 'Alpha Floor' is lost, but AoA monitoring continues:

See footnote 17: Protection totally lost if DUAL ADR failure or ADR disagree.
If there had been AoA protection we wouldn't have this thread.

[cwatters]

What speed does the "Low Speed Protection" kick in?

Edit: Ah i see footnote 18

"If dual ADR failure then low speed stability is lost"

[bearfoil]

A330 has a Horizontal Stabilizer.

It articulates, making it in essence also a variable incidence wing.

With aft fuel, the THS must work against its primary function, that of keeping the Nose UP.

If the THS AoA increases too much it will STALL

If it STALLS, the NOSE will drop like a stone, and the a/c will likely ROLL as well.

A pilot, seeing the NOSE DROP, and roll right. WILL INPUT NU AND ROLL LEFT.

IF Pilot overcontrols, the a/c will CLIMB, perhaps alarmingly, and said climb may become unrecoverable.

just a thought.

[Lonewolf_50]

RWA:
Based only on my understanding of the resource you cited, and a slightly dated training manual on the A330, the automatic feature (alpha protection) would induce control inputs (you could say "fight the pilot" or "help the pilot since what he's doing is heading in the wrong trend") in normal law, but in alternate law, that AoA related feature doesn't (should not?) do that. Stall warning should sound if the AoA is deciphered as a value approaching stall. (It appears that it did ... but also that there are some quirks at very low airspeeds regarding that feature).

What is frustrating in understanding this incident, for me, is the number of parameters that need both Airspeed and AoA as inputs, and the coupling of Airspeed to AoA, and problems this poses for the flight control system when those fundamental inputs are spurious or obviously erroneous, or "voted out." (Note: since the mishap was reported, there has been a Greek Chorus of pilots who point out that flying pitch and power is where one begins to deal with erroneous airspeed problems ... and there is also a considerable body of pilot experience that points to hand flying at altitude becoming a lost art ... )

Systems complexity considered, once in alternate law the speed protection can be overridden by pilot. Whether or not the computer sensed an overspeed protection requirement (and thus a kick off of the autopilot) has been discussed at some length. The consensus seems to be that AP kicked off due to crap airspeed inputs, not due to overspeed sensed (erroneously or otherwise).

As the bits and pieces of info come out of the investigating team, the discussion on Tech Log forum has been skeptical of initial (via the high speed protection feature?) NU input commanded by the robot. Part of the support for that skepticism has been the kinetic energy tradeoff (q) and the recorded pilots back stick inputs (along with roll inputs). These inputs look to have accounted for the pitch attitude and altitude gain (and of course, actual airspeed loss, versus displayed which was for a while all wrong).

Originally Posted by sources albeit dated

High speed protection is active, depending on flight conditions, at / above Vmo / Mmo, and a pitch up load factor up to +1.75g is added to the pilot input when speed exceeds Vmo+6kt or Mmo+.01.
Speed is limited to Vmo+15kt or Mmo+.04 even with full forward stick.
If full forward stick is applied suddenly, speed is limited to Vmo+35 or Mmo+.07 and then returns to the above values.
The protection is deactivated when the speed returns to V/Mmo.
The AP will disengage if the high-speed protection is active.
In Alt 1 ... Above V/Mmo an over-rideable nose up demand is introduced. ... Alternate 2 Pitch control laws are identical to Alternate 1
Protections are as in Alternate 1
... in the case of failure of 3 ADRs, no high speed protection.

What I glean from this is:
if all three of the sensors that feed airspeed info to the flight computers and displays went pear shaped -- the evidence points to this based on pitot icing -- then the automatic pitch up would NOT happen since in Alt 2 that feature is disabled. This presumes that the flight computers more or less were functioning as advertised.

Whether or not a suprious voltage or oddball computer decision entered into this cannot be known as of today. It may be unknowable, if such transpired. There does not seem to be much of any evidence to support that class of malfunction. If such did happen, it didn't leave much of an audit trail.

Svarin has made some thought provoking posts and analysis in that regard, recommend taking a look at his inputs if you have not already.

Cheers

[bearfoil]

Lonewolf50

From the outset and per BEA the PF made one NURL at a/p drop. It was not continuous. The climb is unexplained, although High speed Prot is a candidate, certainly.

[Lonewolf_50]

Thanks bear, I just read PJ2's latest Tech log post on how much SS deflection it takes to start a climb. He related to about six inch control deflection on a yoke controlled jet. Most enlightening. Also the deciphering of the BEA reports on when the inputs to the nose began to drive the nose higher, in concert with TOGA. Paints a different picture.

I think it well to bear in mind that, per the basic systems information publicly available, unless you counter any nose up input you makes on the SS, your nose up input remains within the system.

Put another way, if you put a little nose up in, you need to take the same amount out to restore level flight, unless you are attempting to trade airspeed for altitude. As I understand the Law they were in, (Alternate) the computer won't think through that for you. You must mind your pitch attitude and counter correct for your various inputs.

More than one pilot who flies at high alt has pointed out to how delicately one must handle the big jets at high Mach numbers and high altitudes. Hand flying. (Seems to require some practice to master, like any sort of flying).

If I misunderstand the controls, please correct me.

[bearfoil]

Yes. And NO. In a powered system, especially one with a tagalong "Trimmer" (also described as a variable incidence wing set), it is a bit more complicated? "Stop the Roll". "Relax back stick".

Ab initio complaints from the CFI? Once rolling an A330, or Pitching it, with a "helper" as big as my house, the Physics is different? Not really, perhaps surprising is more accurate.

IF PF's first NU was in some way additive to an existing rotation of some description, it explains a bit how the rotation could have been emphatic enough to elicit 7kfpm? If he held it enough (before the seat started to really push him up!) to allow that big slab to acquire the power to really move her tail, Bob is then someone's uncle........?

The BEA later mention "repeated ND inputs" by the Pilot, but have they attached these to an attempt to recover from the climb? BEA's bon mots need to be sorted by time on a linear graph, perhaps that is forthcoming.

[Lonewolf_50]

Yes. And NO. In a powered system, especially one with a tagalong "Trimmer" (also described as a variable incidence wing set), it is a bit more complicated? "Stop the Roll". "Relax back stick".

Not quite as simple as "relax back stick." That leaves the "up" command in place. Worth reviewing the on line resource, A330-A340 Flight Crew Training Manual . pdf. (Dated, June 2005) regarding SS and high speed protection, if Alpha Prot isn't working. (Seems not to have been, else no stall, right?).
See pages 27 and page Page 34 of that .pdf.

Note: pull side stick up, release. Nose stays up, up you go. Push side stick forward, and then release, to change pitch. If you don't, up you will keep going ...

IF the magnitude, in displacement and time, of your nose up command isn't equaled by the magnitude, in displacement and time of the nose down command, THEN your nose will stay more "up" than "level." (See the pictures).

I have been intrigued by the discussion about what happened deep into the event, when the AoA had gone high, plane was falling, and questions on control effectiveness in well developed stall arise. But we are not talking about that time, the concern at hand is upset initiation.

I honestly don't think it's that complicated.

The complexity begins when one sorts through laws that rely on the AoA input, and Airspeed inputs, and being aware of which law is operating. Some of the laws do some work for you. Some hundreds of posts into this discussion, we have the pilot's own words to tell us which law state to examine: alternate law. Fewer things at work for you.

I'll await further input in re Abnormal Attitude law. Some parameters were met. But some information (leaks?) to date suggest that due to airspeed being erroneous, AA not in play. I hope that gets officially addressed.

Ab initio complaints from the CFI? Once rolling an A330, or Pitching it, with a "helper" as big as my house, the Physics is different? Not really, perhaps surprising is more accurate.

Zero-value-added prose.

IF PF's first NU was in some way additive to an existing rotation of some description, it explains a bit how the rotation could have been emphatic enough to elicit 7kfpm?

Based on what data point? Were there an already existing rate of climb in progress, do you not think the FDR would have that data, and the info be part of the summary?

If he held it enough (before the seat started to really push him up!)

Do you mean "if he had held nose down" enough? Seat push him up? What means this?

to allow that big slab to acquire the power to really move her tail, Bob is then someone's uncle........?

Zero value added, though droll.

As you slow down, the magnitude of force acting on your airfoil reduces as square of the velocity change. Does one get to a point of lost control effectiveness? Good question.

The BEA later mention "repeated ND inputs" by the Pilot, but have they attached these to an attempt to recover from the climb? BEA's bon mots need to be sorted by time on a linear graph, perhaps that is forthcoming.

One certainly hopes for more clarity in the next report.

[bearfoil]

Howdy lonewolf.

The "relax back stick" I qualify in the next phrase "ab initio commands from CFI?"

It is elementary in a cessna. Not so in a big rig.

I've lost [QUOTE] function, so to answer "what data point"? I would say:

Unable. If it's there, BEA have NOT stated it. Simply because we want to believe, we do. Why? Can I say for certain the a/c was not trending in rotation UP? Simply because it is not included? PF input NU and Roll Left. From BEA, we see it everywhwre. Supposedly as his first action after "I have the controls". Is it? Really? In the DFDR, did PF start with a clumsy grab at the Stick after a/p drop, and input NDRR? Was he recovering from his own mistake? No?

BEA will (IS?) living to regret the accommodation it made to Airbus. They must reveal more, and then more, each time stopping unsatisfactorily with "Wait for the final Report".

[TioPablo]

RWA, from the discussions over at tech log, Alpha Protect works in normal law. At some point early in the AF 447 event, the pilots reported alternate law. At that point, Alpha Prot should not have been a factor in the behavior of the aircraft.

I would say... Next time: make a big glider of it... Without any doubt.

[xcitation]

Climb

Bearfoil

From the outset and per BEA the PF made one NURL at a/p drop. It was not continuous. The climb is unexplained, although High speed Prot is a candidate, certainly.

The report does not explicitly say how long the nose-up input was. IMHO it was continuous from 2h 10 min 05 "...nose up input." until 2 h 10 min 16 "...nose-down control inputs". At most this was for 11 seconds and resulted in the climb from FL350 to FL375 which sounds reasonable.
We can speculate if/why the PF intentionally made the climb as he did not adjust the thrust during the change in FL despite announcing he had control before the manouver. This initial nose up would appear to be counter intuitive given the stall warning and desire to maintain cruise altitude. Unfortunately the IAS on the right PFD used by PF was not recorded on the FDR. Did the ADIRUs give bogus attitude indications? It would explain the bizarre "inputs made by the PF were mainly nose-up".

From 2 h 10 min 05 , the autopilot then auto-thrust disengaged and the PF said "I have the
controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall
warning sounded twice in a row. The recorded parameters show a sharp fall from about 275 kt
to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments
later in the speed displayed on the integrated standby instrument system (ISIS).

Note 1: Only the speeds displayed on the left PFD and the ISIS are recorded on the FDR; the speed
displayed on the right side is not recorded.

Note 2: Autopilot and auto-thrust remained disengaged for the rest of the flight.


At 2 h 10 min 16, the PNF said "so, we’ve lost the speeds" then "alternate law […]".

Note 1: The angle of attack is the angle between the airflow and longitudinal axis of the airplane.
This information is not presented to pilots.

Note 2 : In alternate or direct law, the angle-of-attack protections are no longer available but a
stall warning is triggered when the greatest of the valid angle-of-attack values exceeds a certain
threshold.

The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started
to climb. The PF made nose-down control inputs and alternately left and right roll inputs. The
vertical speed, which had reached 7,000 ft/min, dropped to 700 ft/min and the roll varied
between 12 degrees right and 10 degrees left. The speed displayed on the left side increased
sharply to 215 kt (Mach 0.68). The airplane was then at an altitude of about 37,500 ft and the
recorded angle of attack was around 4 degrees.

[Lonewolf_50]

@ xcitation

From the outset and per BEA the PF made one NURL at a/p drop. It was not continuous. The climb is unexplained, although High speed Prot is a candidate, certainly.

FWIW, that quote isn't from me, it's from bearfoil.

The report does not explicitly say how long the nose-up input was.

Indeed, which leaves one wanting in terms of understading PF actions.

IMHO it was continuous from 2h 10 min 05 "...nose up input." until 2 h 10 min 16 "...nose-down control inputs". At most this was for 11 seconds and resulted in the climb from FL350 to FL375 which sounds reasonable.

Ten seconds of nose up input. Continuous or intermittent? If continuous, that's quite a bit of nose up).
(What can you do with ten seconds of sustained "nose up" command in a given aircraft. ) Well, in a small plane, I could loop a T-28 in around ten seconds of continuous nose up (pitch toward stomach) input (a 3.5 g maneuver) back when the earth was nearly new ,and I was learning to fly. I doubt AF 447 pitch input was anywhere near 3.5 g, heck, the acft control system is limited to 2.5 g pull.

Unfortunately the IAS on the right PFD used by PF was not recorded on the FDR. Did the ADIRUs give bogus attitude indications? It would explain the bizarre "inputs made by the PF were mainly nose-up".

Aye. thanks.

[goldfish85]

Quote:
"The cases are completely different."
It is a remarkable coincidence that both zoomed at 4.2 deg AoA

[RWA]

Quoting excitation:-

The report does not explicitly say how long the nose-up input was. IMHO it was continuous from 2h 10 min 05 "...nose up input." until 2 h 10 min 16 "...nose-down control inputs". At most this was for 11 seconds and resulted in the climb from FL350 to FL375 which sounds reasonable.

None of the mentions of 'inputs' record the length of any of the inputs, excitation? However, the context - particularly the fact that the BEA note does not go on to record any climb, but instead quotes the PNF talking about the speeds - strongly suggests that the PF achieved his object (corrected the roll and duly levelled out). I've only flown light stuff (mainly gliders, as it happens ) but even I know that a roll tends to produce less lift from the wings, so that a touch of 'up elevator' is often required to maintain altitude when recovering from an uncommanded roll?

And further, had the PF kept the 'noseup' on, I can't imagine ANY aeroplane taking 11 seconds to respond? Or, if any do, I wouldn't want to fly on them?

"Unfortunately the IAS on the right PFD used by PF was not recorded on the FDR."

I believe that normal practice is for the senior first officer (and therefore PIC while the captain is on his break) to remain in his accustomed righthand seat. This is supported by the BEA quoting the captain as saying, "He's taking my place"?

"Did the ADIRUs give bogus attitude indications?"

Now that's a heck of a good question! And it caused me to look back at a summary of all those 24 ACARS messages. And yes, all three ADIRUs appear to have reported problems simultaneously:-

"34123406IR21,EFCS1X,IR1,IR3"

Looking further, I found something I'd missed earlier - even ISIS, the standby instrument system, appears to have reported problems too:-

34220006ISIS 1,,,,,,,ISIS(22FN

There's an analysis of all the messages below. I can't vouch for its accuracy, but if it IS accurate, and the pilots were presented with a mass of instruments that were either blanked out or reading wrong, the BEA (which only listed the ACARS messages in its first report, without any explanations, and didn't mention them at ALL in the note) is going to have a helluva lot of explaining to do one of these days........

http://www.iag-inc.com/premium/acars2.pdf

[EMIT]

Attitude

From where suddenly come the ideas that the attitude indicators were giving false indications? Wouldn't such a thing, massively important, have been reported in the BEA note?

The "failures" that are distilled from the ACARS messages have been explained a long time ago: systems report OWN failures, but also failures FROM OTHER SYSTEMS, with whom they communicate. Because of that setup, you may encounter the system identifiers IR1, IR2 and IR3 in situations where,e.g. the Air Data units are faulty.

[RWA]

Quoting EMIT:-

"From where suddenly come the ideas that the attitude indicators were giving false indications?"

In my case, from the very first press reports on the accident, plus subsequent amplification?

"Wouldn't such a thing, massively important, have been reported in the BEA note?"

You'd have thought so, wouldn't you? But the note doesn't mention it at all. And all the original BEA interim report said about them was, basically, that they aren't supposed to have anything to do with any investigation :-

twenty-four automatic maintenance messages were received between
2 h 10 and 2 h 15 via the ACARS system. These messages show inconsistency
between the measured speeds as well as the associated consequences.

1.16.2.5 Partial conclusion
At this stage of the investigation, the messages analysed allow us to conclude
that various monitoring processes were triggered. At least one of them
corresponds to an inconsistency in the speed measurements. Several of the
cockpit effects messages recorded could correspond to the consequences of
these monitoring processes:
AUTO FLT AP OFF,
AUTO FLT A/THR OFF,
AUTO FLT REAC W/S DET FAULT
F/CTL RUD TRV LIM FAULT,
F/CTL ALTN LAW,
FLAG ON CAPT (F/O) PFD SPD LIM,
FLAG ON CAPT (F/O) PFD FD.
Note: the CFR was designed to facilitate maintenance operations; it is therefore not
intended to be used for investigation purposes.

"The "failures" that are distilled from the ACARS messages have been explained a long time ago....."

Fine then - apologies, I must have missed it. Please post a link to the 'explanation' you're referring to?

[xcitation]

EMIT

Attitude

From where suddenly come the ideas that the attitude indicators were giving false indications? Wouldn't such a thing, massively important, have been reported in the BEA note?

It would be remarkable I agree. I am trying to explain why would the pilots maintain a generally nose up attitude for 4 minutes of stall descent. There are many possibilities. I find it incredulous that all 3 simply forgot basic stall recovery. IMHO either they ignored the instruments or the instruments failed or both.

The "failures" that are distilled from the ACARS messages have been explained a long time ago: systems report OWN failures, but also failures FROM OTHER SYSTEMS, with whom they communicate. Because of that setup, you may encounter the system identifiers IR1, IR2 and IR3 in situations where,e.g. the Air Data units are faulty.

But did it record every failure? e.g. do we know what the right PFD showed for speed. It should be noted that in other A330 incidents false stall warnings have been generated and in those occasions correctly ignored. Could this be why they ignored most of the stall warnings?

Note 1: Only the speeds displayed on the left PFD and the ISIS are recorded on the FDR; the speed

displayed on the right side is not recorded.

[jcjeant]

Hi,

Can I suggest that if all participants in this theater were all together in the cockpit of the 447 the night of the event .. the end of the flight would be the same (splash)