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-   -   AF 447 Search to resume (part2) (https://www.pprune.org/tech-log/449639-af-447-search-resume-part2.html)

mm43 25th Apr 2011 11:11


But that doesn't explain without an initial UAS upset why the aircraft finished up so close to the LKP even if it did enter an unrecoverable stall following the attempted A/P reset.

The only thing we positively know at this time is at the nominal 0210z AOC report, the aircraft was west of the track. This probably occurred within 30 seconds of the report and not as a premeditated crew action. Unless of course an over-speed event was already occurring, and the heading of the a/c could have been anywhere.

So in 5 minutes the a/c would appear to have gone effectively nowhere. Methinks there must have been more than one upset. In that respect only, your scenario doesn't quite fit, though I am keen to hear a better explanation.

HazelNuts39 25th Apr 2011 11:28

Originally Posted by Svarin
FMGEC1 fault triggering a CPC reset or change of configuration, not a real descent (other messages exist for relief valves and other conditions).

The CPC commanding a change of cabin pressure exceeding 1800 fpm during 3 seconds? Which other messages (cockpit effect or FLR) exist?

Bobman84 25th Apr 2011 12:15

So it's the 25th of April now, not far from 26th.

Any updates in regards to the recovery vessel's position?

rotor12 25th Apr 2011 12:34

The last position :
Carte en temps réel des navires - AIS - trafic maritime et positions

mmciau 25th Apr 2011 12:39

IIRC the Craft should be near station on 26 April .

thermalsniffer 25th Apr 2011 12:51

prim and sec shutdowns

How do the prim and sec faults layer into your scenario?

Stated differently, does AP re-engagement come before or after these messages?


GerardC 25th Apr 2011 13:27

Clearance - No clearance - we take the deviation we need - The information on the weathear deviations will be broadcasted or/and monitored directly on VHF 123.45 that everybody should syntonize ... unless I'm wrong and the appropriate frequency is different in that area (?)
You are right, we ALL take whatever weather deviation is needed, AND (preferably before deviating...) we send a message (HF or CPDLC) : "request deviation up to XX Nm due to weather".
Do not forget these routes are not as crowded as the NAT OTS area : after dozens of SA crossings (before and after AF 447 crash), I can't remember of much (if any) "deviation" chat on 123,45 (or 121,5).

Concerning the questions about ACARS transmissions, sorry, I fail to understand the point : as long as the system is in VHF range, ACARS goes through VHF (as it is much cheaper). When out of VHF range (or if no VHF network exists), the system switches automatically to SATCOM without any crew action.
You get F/D alert messages :
- in VHF range, if you move VHF frequency out of the "DATA" position ;
- out of VHF range, if satcom is lost.

HF data transmission works fine for RA (or pleasure boats email traffic).
At the moment (and in the near future), it is not used (or planned to be used) for commercial aviation.

Svarin 25th Apr 2011 14:23

thermalsniffer wrote :

How do the prim and sec faults layer into your scenario?
Here we need to refer to the MEL, where a procedure is outlined for a PRIM1 dispatch, or a SEC1 dispatch. In both cases, a fault message appears on ECAM 30 seconds after engine start. Let us assume then that a PRIM1 or a SEC1 turned OFF for whatever reason will trigger an ECAM message 30 seconds later (some kind of self-check or whatever it is FCCs do in these situations)

Let us then examine closely the timing of 3 ACARS messages :

2:13:45 WRN/WN0906010213 279002506F/CTL PRIM 1 FAULT
2:13:51 WRN/WN0906010213 279004006F/CTL SEC 1 FAULT
2:14:20 FLR/FR0906010213 22833406AFS 1,,,,,,,FMGEC1(1CA1),INTERMITTENT

FMGEC1 is a FLR message, its correlation window opened one minute before transmission, minus 5 seconds for ACARS sending, thus : 02:13:15.
PRIM1 FAULT and SEC1 FAULT are cockpit effects, but then let us factor in the 30 seconds delay as above. This gives a time of 02:13:15.

Interesting ?

Now more : both PRIM1 and SEC1 messages appear right after the "possible loss of signal" window.

Interesting ?

glad rag 25th Apr 2011 14:28

Well here's hoping they find the recorders and they have viable data.

Svarin 25th Apr 2011 14:32

mm43 wrote :

The only thing we positively know at this time is at the nominal 0210z AOC report, the aircraft was west of the track. This probably occurred within 30 seconds of the report and not as a premeditated crew action.
1 - yes, AOC position at 02:10:34 (minus 5 seconds sending) was 3 NM west of track. AOC have higher priority than maintenance messages, their sending is likely to be close to real time.

2 - how do you know it was not through deliberate crew action ? For my part, I take it as another hint that they were awake and circumnavigating CBs, not as an upset that would have kicked them 3 miles offtrack.

jcjeant 25th Apr 2011 15:25


To wait until the arrival of the research boat on the site .. you can read this ... communication does not automatically mean information

Multiupload.com - upload your files to multiple file hosting sites!

bearfoil 25th Apr 2011 15:41


"The other is:
1. Initial UAS leading to upset, leading to loss of AP
2. Manual recovery
3. FD bars re-appear

4. Catastrophic LOC due to following FD orders"
Why have you assumed upset caused by UAS?? "First" Upset may have been generated by #4 ?? I think your short sequence is probably bankable. If 447 was occupied soldiering on 3:15 past LKP whilst dealing with UAS, they would have been 20nm past LKP and after things went pear, did they attempt a turn back to Brazil? Or, ......

Now 3:15 of continued flight would mean the "Fasten Seat Belt" was on and alerted, so perhaps another look at the conclusion that recovered victims were necessarily unbelted may be needed...

rotor12 25th Apr 2011 15:47

The Ile de Sein will be on site this night

henra 25th Apr 2011 15:57

Originally Posted by HazelNuts39 (Post 6410944)
The AD suggests that the initially commanded movement of the elevator could be too abrupt when the real speed of the airplane is much greater than what the AP 'thinks' it is.

Hmmm, my line of thinking went more in the direction that the actual speed was lower than what the sensors showed.
This would mean that following re-engagement of AP at a lower altitude 'Otto' would try to pull up at best climb (or max climb?) for the determined airspeed.
If the real speed is lower than what Otto thinks that's a perfect receipe for disaster. Trim Nose up, to high of a pitch angle and the engines below CG pushing hard causing further pitch up. Having no visual reference makes it hard to determine timely that something is going South.

The really intriguing question is: Why would the two gentlemen in row 0a/b be confident enough to re-connect the AP immediately after a significant upset.
On the other hand in the AD it was mentioned that exactly this happened in two prior cases. And the FPV being back maybe further increasing the confidence in everything being fine again.
Maybe even knowing they were in degraded law in heavy IFR they thought the AP might be the safer choice.

Just speculation though although a picture is starting to form...

bearfoil 25th Apr 2011 16:05


"Too abruptly" is not necessary for upset, imo. It may simply be a "routine" recapture of a/s and alt? Stall and LOC could follow either way. The AD would be more dramatic if such an occurrence (too abruptly) were possible, no?? Now this is semantics, but if immediate LOC were possible, wouldn't this a/c be under a bit more official sanction??

I do not believe the pilots wanted back in Auto immediately after losing the a/p. If their control had resulted in recapture of Bars and Bird, wouldn't they monitor for a bit ?

just sayin'

(edit) I don't know bout anyone else, but one word that gives me the willies is INTERMITTENT.

ACLS65 25th Apr 2011 16:36


HF data transmission works fine for RA (or pleasure boats email traffic).
At the moment (and in the near future), it is not used (or planned to be used) for commercial aviation.
Actually HACARS or HFDL (High Frequency Data Link) predates SATCOM ACARS and is still in use by a significant number of commercial airliners. I see a lot of traffic from HA, CO, AC, NW, NCA. UP, US, GTI, LH, ZS, AV, etc on everything from A319 to B777. One I don't see is AF, at least from my location.

My guess would be as SATCOM came out some carriers, manufacturers, etc may have moved to it and removed the HF capability, some may have both, and possibly some just have VHF and HF ACARS.

These initial ACARS systems have been extended to offer worldwide coverage, even in mid-ocean and
sparsely inhabited areas, using the Inmarsat facilities and HF data link, and to cover not only company
communications but also ATC services, starting with predeparture and oceanic clearances.
On aircraft delivered since 1998, the ACARS unit has been replaced by the Air Traffic Services Unit
(ATSU), which is designed to also accommodate safety-related ATC functions using the Aeronautical
Telecommunications Network (ATN), offering the majority of ATC and other communication services now
using voice, and more importantly, offering profitable migration to the ATN. The ATSU is the first unit to
host software from a number of different vendors. The same ATSU is also used on the A320 family of aircraft.
The ATN upgrade is being implemented to be available when the corresponding communication and
ATC services are in service.
From: New Avionics Systems —Airbus A330/A340


DingerX 25th Apr 2011 16:41

Okay, I went back and read it over again, and yes, you're right that the message in question is stamped to the minute 0213.

Here's what I understand (repeating what's been said before):

Cockpit Effect messages go out as soon as they are received.
A fault message opens a correlation window of one minute. At the end of the minute, those messages are prioritized and transmitted.

Of the 25 ACARS transmissions:

there are a slew of 17 messages, fifteen stamped 0210 and two stamped 0211 that are transmitted practically without interruption (with holes for two others), these were received from 0210:10 to 0212:16

Thirty-five seconds later (2:12:51), there's another sequence of three messages: one cockpit effect (stamped 0212) and two more faults (stamped 0211), ending with the one received at 2:13:14.

The gap observed between the message sent at 2 h 13 min 14 s and the one sent at 2 h 13 min 45 s is due, at least in part, to a temporary interruption in the communication link between the aircraft and the satellite
Transmission number 24 is sent at 2:14:20, refers to an intermitten FMGEC fault as reported by the AFS, and on this hypothesis, would be due to re-engaging the autopilot and causing a violent pitching.

So, on this hypothesis, the aircraft was flying smoothly. After the last cockpit alarm at around 2:12:40 (the NAV ADR disagree), things returned to normal. While the messages are going out to the satellite, at around 2:13:15, or at most forty seconds after the last NAV ADR disagree warning (or, if I'm wrong about how the ACARS WRNs are queued, all of seventy-five seconds), the crew punches in the autopilot and brings about the upset.

So it boils down to Svarin's question about that AFS message: does it imply that the A/P was on?
AFS may be 'Airbusese' for Autopilot, but generally differences in names imply differences in functions. Could a fault in the FMGEC relate to something like its envelope or airspeed functions? Does having the A/P off and being in Alternate Law 2 shut down the FMGEC?
The awkward wording of the BEA is to say, if there were a "Cockpit effect", it would have been a disconnection of the autopilot. From this I don't think we should be inferring that the A/P was on. It _could_ have been, and it _could_ have happened that way, but the questions on the interpretation suggest that there may not be any data to support it.

Whatever the "right answer" is, there will be data that has no relevance. But I'm not sure we can claim that there were no thunderstorms.

Svarin 25th Apr 2011 17:02

No first upset
henra wrote :

The really intriguing question is: Why would the two gentlemen in row 0a/b be confident enough to re-connect the AP immediately after a significant upset.
Why ? Maybe because there was no first upset... Just an unpleasant but otherwise normally manageable UAS... When it is over, back to normal ops, get A/P back on. No need to tell the cabin crew.

Fronl1ne 25th Apr 2011 17:14

Hi all,

Only SLF here, but one with reason to be flying to Brazil 3 times per year, and so have been watching your ruminations with great interest.

Just a quick question and then I will return back to the cheap seats.

Why can't the Pitot Tubes have a second, back up set recessed into the body of the aircraft and kept warm as toast and free of crystals, if/until required and deployed much in the same way the RAT is?

For a multi-million dollar aircraft moving 200 odd people about the planet, would that really represent a financial cost too far for manufacturer and customer alike?

It's been bothering me for a while that one.

Thank you for your time. Now slipping back into the undergrowth.

Chris Scott 25th Apr 2011 17:15

Hello HN39,

“I've been trying to imagine the mechanism by which re-engagement of the autopilot at corrupted airspeed would cause a violent upset. The AP controls altitude, so the first assumption one needs to made is that the altitude at re-engagement differs from the s elected altitude. Let's assume it is lower. The AP will then command movement of the elevator control to initiate climb to capture the selected altitude. The AD suggests that the initially commanded movement of the elevator could be too abrupt when the real speed of the airplane is much greater than what the AP 'thinks' it is. [...]”

I was considering a similar idea, though not necessarily with the extra control authority associated with under-reading ASI that you suggest. The possibility of a high FD pitch-bar, and the AP following same, may be subject to two points:
(1) pilots are warned not to engage the AP unless and until the FD command bars are very close to neutral;
(2) (tentatively) does the FMGC not default from ALT (hold) mode to the basic HDG/VS mode (or TRK/FPA mode, if appropriate) in the event that the aircraft deviates a certain amount from the selected altitude? (Currently have no manuals to hand, and a 30Kb/s internet connection, so cannot research this.)

In the event of (2) coming into operation, it could even have resulted from a relatively small excursion below the selected altitude. As the PF adjusted the VS selector-knob to a positive value, ALT* mode would take over sooner or later, possibly causing a pitch-up initially. Many of us have reason to remember the great authority of ALT* mode (altitude-capture mode) on the A330 and other Airbuses, and the potential problems associated with that in the past. No doubt Airbus addressed this issue in the 1990s. However, if the speed was already at or near the low-speed buffet, for whatever reason, any pitch-up would be... unfortunate. I appreciate, of course, that like me you may be pursuing a scenario in which under-reading of IAS leads the speed to be higher than normal. (Did the intakes freeze before the drain holes, etcetera...)

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