HazelNuts39

That's another intriguing thing. The ADR's calculate Mach and CAS quasi-simultaneously from the same pitot and static pressures. Why would there be a delay of two seconds between Mach and CAS?

From Interim Report no.2:

DozyWannabe

Yes - quite clearly, although the deflection is clearly less in the earlier part of the graph - the question is, what was their altitude and airspeed in the two phases you highlight - it looks like the system was deflecting the elevators relevant to cruise speed in the first part, and lower airspeed in the second.

@pax2908 below - there'll always be debate over that one. The only difference is that the THS trim would have had to be wound on manually rather than happening automatically, which a lot of people were using as an argument in favour of Direct Law until the report came out, reasoning that the PF would not have wanted that much nose-up deflection. However the CVR now indicates that is precisely what the PF was trying to achieve - the big question now is why.

pax2908

Re. jcj (elevator vs sidestick) because the control loop is not 'direct law' so as long as the a/c is responsive in pitch, the g demands can be achieved with relatively small deflections? One question is, whether direct law might have been more appropriate?

Microburst2002

this is too long a thread.

Can anyone tell me what was the pitch attitude and the thrust at the time of the AP/ATHR disconnection?
I believe that, if they were normal (about 2.5º) but the atmosphere was somewhat turbulent and at night, somatogravic illusions could have played a very important rol, along with lack of hand flying in skills.

I can't see why else he would pull up in the first place, unless attitude was too low, or thrust was in idle and altitude decreasing or something like that.

There must be a reason, other than total inability to fly straight and level.

A33Zab

I did have the same observations,

Few seconds before AP disconnect (Line 1B)

Note: Thrust Lever was taken out of CLB detent (THR lock Ulocked) but not moved to intercept N1 T/L target or the instinctive disconnect was used. Line C2

[Engine Control Unit ECU: The autothrust is in Memo Mode. The power level is latched to its prior state provided that the throttle has been in the
Max. Continuous or Max. Climb detents for at least 2 seconds.
The throttle must stay in one of these detents in order to hold Memo Mode]


T/L retarded to below CLB detent. few seconds before Line 3C.

Line 4C and at the same time THS (-3.8°) starts to move NU.
Did T/L movement below CLB detend resets a logic(FMGEC)? and did thereafter the TOGA initiate this THS movement? (Normal TO~15° pitch/TO thrust) Line 4C/4E
After the TOGA T/L was few seconds into MCT/FLX detent(N1 continued at 100%+) Line 5C before T/L was positioned in IDLE and THS movement seemed to stop at -13.5° (Line 5E)
At that time there was a full elevator command on the SS. Line 5D

jcjeant

Hi,

Pitch protection in alternate law ? or .. ?

BOAC

I fear it is time to delve a little deeper into the 'management' side of this.

Those of us with a little experience know that when (a less experienced) PF gets confused, it is pointless shouting rapid commands at him/her since, like a stall warning, they either will not register or will further confuse.

So, I ask, why did PNF ('Duty Captain') NOT take control much earlier? It is either a further indictment of AF training of their co-pilots for LHS relief (or simply for being a pilot) OR was there an extra person or persons in the flight deck that may have inhibited PNF from the firm take-over of control that was necessary? Do we know from the CVR?

grity

jcjeant the elevator and THS is very detailed here:
http://www.pprune.org/tech-log/45687...ml#post6610567
or s.44

the stick movements are detailed on the 3.report s 31 and s 32

s.31 was also my databasis for the stick-movment of the first 10 sec after 2:10:07
(what you call making mayonaise)

if PF was never before flying in altlaw at this altitude in his live, than he was a very fast lerning pilot: he need just 20 sec to learn how to hold the wings level and no longer to overreact....learning by doing but he really should have learnd this not in this situation

and I think the PNF had (maby partiell) realised the movements of the PF stick, he made one comment abaut it:
2 h 11
PNF: Surtout essaie de toucher le moins possible les commandes en en latéral hein
Above all, try to touch the controls as little as possible in in lateral, huh

DozyWannabe

@jcjeant - Nothing to do with any "protections" as such, travel limiters on hydraulic surfaces have been around for donkey's years (you don't want the same input:deflection ratio at cruise as you do at takeoff or on approach!). It looks to me like the limiters were functioning as they should have been - restricting surface travel while apparently in stable cruise phase and giving maximum authority when things started to go pear-shaped.

@BOAC - Indeed, and this is the similarity to the Birgenair case that I feared - in the Birgenair case it was put down to the command gradient because the Captain (ex-military jock, very senior) was PF, and the F/O (PNF) was relatively junior, despite the fact that the PNF clearly had a better handle on the situation. Why the more experienced F/O (PNF) felt he could not take command from the junior F/O (PF) I cannot fathom. In fact there was an intriguing exchange at one point where the PNF calls for "controls on the left" and starts making inputs, but shortly thereafter the PF regains control and continues handling as before (alas incorrectly). To our French cousins - would you expect "controls on the left" to be a demand for both pilots to make left bank inputs or was he in fact calling for control and overruled by his junior?

@grity (and others) - I've started noticing a reference to "squirrelly" behaviour (very sensitive controls) in Alt Law, which was earlier refuted by PJ2 - who said that the controls in Alternate were slightly more sensitive, but that the difference was barely noticeable in practice. Can we stick to what we *know*, please? The point the BEA were making was that there seemed to be insufficient hand-flying training *at altitude* in AF - the FL was the main factor, not the control law.

SaturnV

BOAC, are you suggesting the wife was or had been in the fourth seat?

---And that's why the fourth seat was retrieved, if only to check the straps?

This was a flight crew that after the SELCAL check with ATLANTICO, apparently switched immediately to the DAKAR frequency. And a flight crew that left the radar in CAL mode until 0208.

The Captain had asked the PF whether he wanted to take his rest and the PF said he wasn't sleepy. The Captain apparently then took his rest during the period that the PF would have been resting.

Is the PF unbelted because that facilitates his turning around if he wants to talk to someone behind him?

All that said, its hard to believe the presence of a fourth person on the flight deck would not have been hinted at by now, through some leak to the media.

hetfield

IF there was a fourth person on the flight deck it should have been mentioned already by the BEA reports........................

BOAC

Saturn - no, not suggesting, just asking. It is known that some European airlines are not as correct in resticting access to the flight deck as most UK ones (DB and SR of Virgin excepted, of course) so I felt it a valid question.

SaturnV

BOAC, without the complete transcript, we don't know the extent of any extraneous conversation.

The CVR record begins shortly after midnight, and the only apparent observation with respect to external weather that's noted from the start of the CVR until after 0200 is when overflying the coast at Natal, where the captain remarks that the weather has been good.

There apparently is no discussion by the flight crew of the message from dispatch received at 0030 alerting them of Cbs between SALPU and TASIL. (The third interim report again specifically notes this message.) The range of the radar is reset after the SELCAL check at 0135, but it is left in CAL mode.

GarageYears

There was a comment by HarryMann (http://www.pprune.org/tech-log/45687...ml#post6610754) that perhaps the PF was hearing a different airflow sound and wrongly associated this with high speed - absolutely that is possible!

As I noted previously, I have been involved in Level D sound simulations for over 20 years now and would certainly find it likely that the aerohiss heard at an abnormal attitude such as that experienced by AF447 on the way down would likely be similar to the noise normally associated with high Mach.

This would be somewhat similar to the sound when an aircraft achieves some level of sideslip, which is particularly noticeable due to the asymmetric flow of air over the cockpit.

In a stall such as that experienced by AF447, with a significant and unusual AoA, the airflow breaking over the nose and windshield would be turbulent and certainly sound "different". I doubt it would be identical to that of high Mach cruise (which just tends to significantly louder than normal - the change from 0.82M to 0.85M for example is significant in dB terms), but for any pilot I suspect it would be noticeable.

In my comfy office, it is easy to say that the clues were all there - attitude and altitude (or more explicitly rate-of-descent), but I will add this - most simulators would do a very poor job of representing this sound condition - in fact I would so bold as to say they would do a crappy job and would likely generate little, if any sound, since forward airspeed is the driving parameter for the aeronoise sound cues (a combination of Mach and CAS).

As I write this post, I am now attempting to think through what would be needed to drive this abnormal descent sound cue - probably a function of AoA and vertical speed...

Golf-Sierra

Hello,

BEA report, page 109, Annexe 4, vitesse verticale[FT/Min] (bright red)

Up to 02:12 it was consistently negative, but then it jumped up to 0, stayed for a while and then oscilated. Just before impact it went positive to about 2500 ft/min a couple of times.

Why?

At an extreme rate of descent (-16'000 ft/min) what would the altitude tape look like? Would it be clear they are falling, or would it simply be a blur?

Could this strange fluctuation in the v/s indication be the 'straw that broke the camel's back' which completely confused the crew. Did the PF completely disregard the loss in altitude as he was convinced that the altitude indication was also unreliable?

Shadoko

Could the airflow created by the thrust alter the direction of "natural" airflow due to the flight path? And the resulting AoA of the rear surfaces would be very different of the one of the wing?
Another question: at the same moment (when a/c right banked until 40°), what stopped this right wing plunge? The low wings configuration vs fuselage (so the entire fuselage has a "lateral drag" in this attitude) or the "lateral drag" of the vertical stabiliser (and then initiated the right turn: begining of a spin dive?)?

DozyWannabe

But at the same time would it not be prudent to check the altimeter (which would have been significantly unwinding at this point)? If AF had passed on the bulletin sent by Airbus regarding the problems with the Thales pitots and subsequent UAS incidents, then surely this knowledge should have been - if not at the front of their minds - at least easily accessible?

Don't get me wrong, I have long argued that the situation these guys found themselves in would have required the best of their abilities (a tall order at 2am) and more than a spoonful of luck to diagnose and correct, but if they *had* been able to bring their "A" game, a glance at the power settings and the ADI should have given them a clue as to their predicament. Admittedly this is 20/20 hindsight, but given the Birgenair and Aeroperu incidents 14 years previously - has it not percolated through the piloting fraternity that when you have a UAS situation (and ice is the likely culprit) that the only readings you should rely on are your attitude indicators, thrust settings and altimeter?

Looking at the DFDR sidestick traces, it seems that a nose-up attitude was commanded almost throughout the sequence - why? Did he "tense up" and not realise he was ordering back-stick? I ask this because from my Air Cadet days I remember that stall and back-stick was a no-no.

hulotte

Le pilote en place CdB prend la priorité. Le manche CdB est positionné à gauche en butée.

Commande à gauche:
Meaning : LHS (PNF , FO) had asked for taking over flight control !!! and act as PF

Then RHS (junior) take over control using priority knob

DozyWannabe

Bloody hell - what was going on in that flight deck? Surely "I have control" means just that, but if what you're saying is true, PNF said "I have control", the PF ignored him and he didn't say a word!

GarageYears

The very first explicit reference to ALTITUDE occurs here:

It would seem that Altitude was not high on the list of concerns until nearly 60 seconds AFTER the Capt returned to the cockpit, at least from the words spoken.

The point of my post and the original mention by HarryMann was an attempt to understand the PF's comment regarding "crazy speed"... I do have some concerns that he may have thought the opposite - i.e. crazy LOW, but that would not agree with the use of the Speedbrakes.... so it has to be crazy as in 'fast'? But then you wouldn't select TO/GA in that case.

A lot of confusion basically, which I think sums it up.