Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

AF 447 Search to resume

Tech Log The very best in practical technical discussion on the web

AF 447 Search to resume

Old 18th Dec 2010, 19:55
  #2601 (permalink)  
 
Join Date: Jan 2002
Location: USA
Posts: 286
will begin in the north of the 40NM radius probability circle and extend south to the Last Known Position.
Am I missing something. Why so far North, and not any further South than the LKP? I surely hope that they will look in unsearched areas. Perhaps they know a lot more than has been indicated. Either way, lets hope for sucess.
wes_wall is offline  
Old 18th Dec 2010, 20:13
  #2602 (permalink)  
 
Join Date: Jun 2009
Location: NNW of Antipodes
Age: 77
Posts: 1,330
promani
I thought that WHOI was given the task of finding AF447 in February?
Le Figaro article has been written for a French audience! My understanding is that WHOI is the prime contractor and "Alucia" is the vessel contracted to carry their Remus AUVs and personnel.

wes_wall

.. will begin in the north of the 40NM radius probability circle and extend south to the Last Known Position.
I wouldn't be placing any sort of odds on what has been reported. Some of it is nothing more than speculation.
mm43 is offline  
Old 18th Dec 2010, 21:41
  #2603 (permalink)  
 
Join Date: Jul 2009
Location: Not far from a big Lake
Age: 78
Posts: 1,458
If the search is only North of LKP is indeed true, then they are absolutely discounting the possibility of AF447 losing control in Normal Law either at or slightly before the ACARS sequence.
From the BEA Perpignan accident report:
When the stall warning sounded, the Captain reacted by placing the thrust levers in the TO/GA detent and by pitching the aeroplane down, in accordance with procedures. The nose-down input was not however sufficient for the automatic compensation system to vary the position of the horizontal stabilizer, which had been progressively deflected to the pitch-up stop by this system during the deceleration. The Captain controlled a left roll movement, caused by the stall. The aeroplane’s high angle of attack and the roll movements generated asymmetry, and a speed variation between ADR 1 and 2 appeared. This increasing divergence caused a rejection of the three ADRs by the FAC then the ELAC. The flight control system then passed into direct law. It is likely that the crew did not notice this due to the emergency situation and the aural stall warning that covered the warning of a change of flight control laws.
The point of the above is to show that a AF447 departure from controlled flight in Normal Law would be expected to cause the ADRs to reject and the control laws to degrade.
If no recovery, the aircraft would be found close to LKP, even possibly South of LKP.
Machinbird is offline  
Old 19th Dec 2010, 01:11
  #2604 (permalink)  
 
Join Date: May 2010
Location: MA, USA
Posts: 126
New search/La Figaro

My French was never good enough, but Google's translation is:

from La Figaro:
The research will once again take place in a circle of 40 nautical miles (72 kilometers) around the last known position of the flight AF447. The goal is to finish browsing north of the area that was observed last spring and then systematically sweep the entire area back down south and the last known position of the aircraft. Many experts believe that because the wreck lies further south.
I can see that this might be interpreted various ways, but I would interpret it to mean that the area east and north of the last search area will be covered, that LKP is included in the search area, and also a large portion of the southern area. I am thinking that "sweep the entire area back down south" refers to the area of the 40nm circle, and not to the area searched in phase 3.
auv-ee is offline  
Old 19th Dec 2010, 02:09
  #2605 (permalink)  
 
Join Date: Jul 2009
Location: Not far from a big Lake
Age: 78
Posts: 1,458
In close association with the first Le Figaro article, there was a very interesting article regarding who is participating in the search...... and who isn't. See Link: Le Figaro - France : Nouvelle campagne mi-février pour retrouver l 'AF 447 Please pardon the rough Google translation:

INVESTIGATORS DENOUNCED THE WASTE OF PRIOR RESEARCH
By Fabrice Amedeo
17/12/2010
The Bureau of Investigation and Analysis (BEA), who led the first three campaigns, loses his hand on the ground. It is the U.S. Woods Hole Oceanographic Institute who took control of operations.

Operation Last Chance sounds a bit like a disavowal previous . Three missions have been organized in the South Atlantic. The first, launched a few hours after the tragedy , helped recover bodies and debris from the aircraft. The second, launched one month later, tried to capture the signal of the black box before it goes out. The third, organized last spring, has combed the area defined on the basis of studies rétrodérive. This method is based on the positions of bodies and debris recovered and to define the position of the wreckage through a study of the currents. In vain ...
This time, the Bureau of Investigation and Analysis (BEA), who led the first three campaigns, loses his hand on the ground. It is the U.S. Woods Hole Oceanographic Institute who took control of operations while on-site coordination will be ensured by a framework of Airbus. "The BEA is the guarantor of the independence of research and investigation, said a close case, but we will work differently." Meaning: more efficiently. Interviewed by Le Figaro, BEA refuses him, to comment and explained that, for now, "nothing is finalized."
The Alucia that will be equipped submarines Remus. During the last operation, boarding submarine ROV has indeed squandered the funds made available by Airbus and Air France. "They have not been once to the sea," laments an investigator. This material was indeed expected to go up the black boxes and pieces of wrecks that have never been located. Reportedly, the ROV had been rented at exorbitant prices to the Navy, for diplomatic reasons, on the advice of pressing the Embassy of France to the United States. "Officials no idea what the subsea intervention have interfered in the investigation, expressed regret one of its members. This proved disastrous. "Sonars onboard were also used. "They swept plains on the outskirts of the search area, said an investigator, but were never able to rake the area with high probability which is very mountainous."
The study methodology rétrodérive also ineffective in this region of the globe where the currents are very irregular and at times of the year (June) where there is not mainstream but rather a gradual rotation their direction. "The models had forecast 0.1 knot of drift, an investigator said. Once there, we realized they were ten times stronger. "Within the survey, were also strong voices in denouncing the methodology of the Bureau of Investigation and Analysis (BEA), which wanted to keep hold of the studies and did not adequately take into account the findings of a team of Chinese scientists from the Massachusetts Institute of Technology (MIT). Air France and Airbus have promised that this time, there would be no squabbles of ego and the systematic sweep of the area increased the chances of success.
Machinbird is offline  
Old 19th Dec 2010, 02:42
  #2606 (permalink)  
 
Join Date: Jun 2009
Location: NNW of Antipodes
Age: 77
Posts: 1,330
The study methodology rétrodérive also ineffective in this region of the globe where the currents are very irregular
- when sorted into readable English is:-
A study of the backtracking methodology reveals it was ineffective in this region of the globe where the currents are very irregular
So, who is getting the blame for this? The Drift Working Group as a whole, or the BEA for not supporting the WHOI/MIT methodology?

Irrespective of the politics involved, the BEA will assume responsibility for any recovered wreckage once it has been raised to the surface.

mm43 is offline  
Old 19th Dec 2010, 15:29
  #2607 (permalink)  
 
Join Date: Jul 2009
Location: France - mostly
Age: 80
Posts: 1,689
gossip

mm43;

I thought you had consciously ignored the second article in lefigaro.fr.

We have seen more stories from Fabrice Amedeo picking up gossip from unnamed sources 'close to' the investigation. Fascinating read, to be taken with more than a grain of salt, IMHO.

regards,
HN39
HazelNuts39 is offline  
Old 19th Dec 2010, 16:35
  #2608 (permalink)  
 
Join Date: Jun 2009
Location: NNW of Antipodes
Age: 77
Posts: 1,330
More gossip

HN39;
I thought you had consciously ignored the second article in lefigaro.fr.
No, I didn't consciously ignore it, I just didn't see it! However, I agree with you that Fabrice Amedeo seems to not only enjoy his coffee, but has an ear tuned to the relevant small talk.

Fabrice Amedeo pour -

Non! Non!
Ce n'est pas, "Trois missions ont été organisées dans l'Atlantique Sud."

Mais il est, "Trois missions ont été organisées dans l'Atlantique équatorial du Nord."

mm43

Last edited by mm43; 19th Dec 2010 at 19:36. Reason: le message en français
mm43 is offline  
Old 21st Dec 2010, 17:32
  #2609 (permalink)  
 
Join Date: May 2010
Location: USA
Age: 72
Posts: 18
New Pitot Warning

. . . . . . . Airbus has discovered that in some cases two Pitots can give matching, incorrect speed data, which could lead pilots to re-engage autopilot prematurely . . . .

Read more: CBC News - World - Airbus gives new warning on speed sensors
MountainWest is offline  
Old 22nd Dec 2010, 15:46
  #2610 (permalink)  
 
Join Date: Jun 2009
Location: Dorset
Posts: 30
ACARS Message Timing Anomalies

The ACARS messages are intended to be read by a maintenance crew sometime before the aircraft lands in order that they can be prepared for a repair/ box swap. They are relatively low urgency, low criticality messages; 'anomalies' could be seen for a number of reasons, such as:-

1. Source Message Generation Delay.
The originating sub-systems usually check inputs from sensors, possibly via an AtoD converter, against predefined criteria (range check, rate check, comparison) and may conclude that the input is 'bad'. The corresponding output(s) to other sub-systems over the ARINC 429 would be marked as 'invalid' with a default value; if further readings over subsequent cycles are still bad, then a 'failure' maintenance message may be generated by the sub-system. i.e. the fault goes from being possibly intermittent to 'hard'. The period of time between the first 'bad' reading and the failure message being generated could be 10's of seconds. The message may be given a time stamp when the fault count was started. If the Pitot readings were suspect some time in the minute(s) before 02:10; the AP could then be the first sub-system to complain, then later (message 14) the 'hard failure' was registered and (message 18) the NAV ADR Warning was generated. This possible maintenance message delay before a fault is declared 'hard' could explain why the Failure messages (19 & 20) time stamped at 02:11 are 'after' the message at 02:12 and the one at 02:13 (message 24) is after 02:14.
2. Potential for Missing Messages
It is possible that some messages were not transmitted due to a full buffer within the CMC. I would expect that the message queue handling software would have a wrap around buffer with protection to prevent the buffer 'over filling'. However, the assumption may have been made that only a few maintenance messages per flight would be the norm. The nominal transmission rate of one message every 6 seconds allows for a sustained rate of 10 messages per minute. A buffer size of 10 messages could (with lack of hindsight) seem sufficient. During 02:10 the flood of 15 (or more) messages within a minute may have caused some messages to be 'lost'.
3. Messages not exactly every 6 seconds
From the SITA website (www.sita.aero/file/1569/Aircom_new_generation_services.pdf) the satellite communication uses a Carrier Sense Multiple Access (CSMA) protocol for Media Access Control (MAC). This mean that before an aircraft starts transmitting, it first checks to see if anyone else is transmitting. To avoid repeated retries if 2 aircraft happen to be in phase on a 6 second cycle, the time between transmissions for each aircraft would have a different, random 'jitter' applied to the basic 6 second cycle.
4. Messages at 15 second interval
There are 3 messages (10, 13 & 16) that all have a received interval gap of 15 seconds; my assumption is that these could be messages that were not acknowledged as having been received by the ground station. Comms protocol usually require that if the transmitting station does not receive an 'ACK' from the end receiver within an appropriate time interval (3 seconds would seem to me to be not unreasonable), it will hold off transmitting the 'next' message and resend the unsuccessful message again. This would give a 9 second delay on top of the normal 6 second cycle.
5. Message 18 gap of 31 seconds
Message 18 seems to be where the message buffered has just been flushed as the time stamp and received time are both in the same minute. That would suggest to me that the gap is due to no messages being generated for 5 cycles of the 6 second transmission slots
6. Loss of Signal
I seem to remember reading somewhere that the INMARSAT link uses a once per minute status message (unrelated to ACARS messages) to monitor which aircraft are still in range. In which case the sat comms would know if the link was 'lost' or not.
Conclusion: The flood of 15 (or more) messages, their interpretation, from diverse sub-systems and all at 02:10 could suggest that the aircraft went rapidly into a chaotic flight state, probably a bit before 02:10. In which case point of impact would be as likely S of LKP as N.

Last edited by VicMel; 22nd Dec 2010 at 16:19.
VicMel is offline  
Old 22nd Dec 2010, 17:57
  #2611 (permalink)  
 
Join Date: Jun 2009
Location: Bedford, UK
Age: 66
Posts: 1,245
ACARS system knowledge

Ok, but surely the investigating team is fully clued up on ACARS and would be capable of generating possible scenarios ? If the search area is still to the north seems they either came to a different conclusion or this line of analysis escaped them. The latter would be deplorable so I hope not.
Mr Optimistic is offline  
Old 22nd Dec 2010, 20:17
  #2612 (permalink)  
 
Join Date: Aug 2009
Location: Germany
Age: 63
Posts: 1,809
Cool

Hi,

. . . . . . . Airbus has discovered that in some cases two Pitots can give matching, incorrect speed data, which could lead pilots to re-engage autopilot prematurely . . . .

Read more: CBC News - World - Airbus gives new warning on speed sensors
Airbus is warning pilots about a dangerous potential malfunction of speed sensors on aircraft like the Air France A330 that crashed into the Atlantic last year, killing all 228 people aboard, including a Canadian.
Malfunction and failure are different things
If it's a malfunction is to the manufacturer (or the airline) to fix it .. not the pilots !
jcjeant is offline  
Old 22nd Dec 2010, 20:31
  #2613 (permalink)  
 
Join Date: Feb 2008
Location: Europe
Posts: 80
EASA warns A330 crews: Check speeds if autopilot disengages
GobonaStick is offline  
Old 22nd Dec 2010, 20:39
  #2614 (permalink)  
 
Join Date: Jul 2009
Location: USA
Age: 58
Posts: 28
AP Reconnect

So assume the AP was reconnected with two faulty tubes reading the same, would the ACARS messages that followed be consistent or inconsistent with that???---thinking of the PRIM and SEC faults.
thermalsniffer is offline  
Old 22nd Dec 2010, 21:17
  #2615 (permalink)  
bearfoil
Guest
 
Posts: n/a
The possibility of Upset prior to 2:10 is addressed in many places here on Thread.

Upset would include (potentially) bad AS and IRU's. Leading to Computer failures.
Is this not correct? The Computer is NOT programmed to fly in upset, nor is the a/p.

I thought we had determined all this.
 
Old 22nd Dec 2010, 22:25
  #2616 (permalink)  
 
Join Date: Jan 2005
Location: France
Posts: 2,316
Originally Posted by thermalsniffer View Post
So assume the AP was reconnected with two faulty tubes reading the same....
It wouldn't need that...
All it would need is two pitots icing up in a closely similar manner.... and that wouldn't be the first time that has happened.
And yes, the ACARS messages would have been very similar, initially.
ChristiaanJ is offline  
Old 26th Dec 2010, 20:54
  #2617 (permalink)  
 
Join Date: Jun 2009
Location: Dorset
Posts: 30
ACARS Messages on AP reconnect

Having worked on fault detection/management on Avionics sub-systems I find difficult to comprehend how there could be such a sudden 'burst' of ACARS messages, 15 (or more) of them, in a minute, from diverse sub-systems. Such a sudden burst suggests that some messages would have been generated by different sub-systems at the same time. There may not have been time for the pilot to reconnect the AP before all of these other warnings came up on his screens; the AP would probably have been the least of his worries!
Considering that the pitots are all in the same environment (and located in the same area!), it is quite possible that two (or all 3) pitots iced up in a similar fashion. However, I would not expect them to ice-up in synch. Instead, I would expect that one pitot would provide 'bad' data before the other and the degradation (warnings from other sub-systems) to be a more gradual process. As a comparison, the data derived from QF72 FDR (Table 3 in www.atsb.gov.au/publications/investigation_reports/2008/aair/ao-2008-070.aspx) shows:-
1. The first event at 04:40:28 as AP1 disconnect
2. Some other warnings that perhaps resulted in a few (a lot less than 15, I would think) ACARS messages over the next minute.
3. Another minute before the first pitch down event occurred
4. Nearly another 3 minutes (04:45:11) before Flight Control went to Alternate Law
This is in a situation where 9 parameters from ADIRU 1 were recorded in the FDR as having “spikes”, with one (AoA) having a recorded 42 “spikes”, with probably other spikes not recorded.
In comparison on AF447, only a single sensor/parameter is seen as being the prime suspect in supplying 'bad' data, but the Flight Control Alternate Law Warning was just two messages later, probably occurring somewhere between 0 and 12 seconds after the first event (also AP disconnect). Is it really possible that pitot icing could have caused such 'instant chaos'?
VicMel is offline  
Old 26th Dec 2010, 21:09
  #2618 (permalink)  
bearfoil
Guest
 
Posts: n/a
VicMel

I think it is unlikely a pitot tube caused the avalanche of ACARS, as you also propose. Of more interest to me is the operation of the a/c prior to the AP disconnect that occurred within the parameters of control limits the AP was programmed with. These limits are not narrow, the Pitch allowables are I believe 24 degrees (15 U and 9 D). The Roll limits are 45 degrees per side, for a total excursion of 90 degrees. Is it possible that the crew were satisfied with a rough ride that took the a/c to its limits of "comfort"? We hear from time to time of the explicit Faith put into this a/c by its pilots, and a desire to fly to the AP disconnect as a conscious decision is certainly plausible. If at this time, Law regression and bunk weather forced an immediate decision on the part of this crew to NOT re-engage AP, upset may have already occurred, and as has been explained so many times, conditions of flight were marginal perhaps in ALL respects, and control may not have been recaptured. To me, it is difficult to imagine an orderly march of messages in transmitted messages of ACARS, the sheer number alone suggests that the system had been totally overwhelmed v/v sequencing prior to AP drop. If upset had occurred in this way, the failure of three pitots virtually simultaneously suggests an Unusual attitude or two were involved in the bunk AS reads. imo.

bear
 
Old 26th Dec 2010, 21:38
  #2619 (permalink)  
 
Join Date: Jan 2005
Location: France
Posts: 2,316
VicMel,
I'm afraid you're barking up the wrong tree...

Events with two out of three pitots icing up synchronously, with the A/P "believing" the wrong data, and similar strings of fault messages, have already happened.

They didn't lead to a crash, because the pilots understood the problem in time, and used "pitch and power" to "fly out of it"... which is why we have the full sequence of fault messages from the FDR, rather than a fragmentary sequence of ACARS messages.

The very recent Airbus memo about not re-engaging the A/P too soon after a "loss of speed data" event also clearly points to their thoughts about the subject.... bearing in mind that they may not know a lot more about what actually happened to AF447, but that they know a lot more than we do about how the systems and aircraft would behave in similar circumstances.
ChristiaanJ is offline  
Old 27th Dec 2010, 17:20
  #2620 (permalink)  
 
Join Date: Jun 2009
Location: NNW of Antipodes
Age: 77
Posts: 1,330
ICAO High Level Safety Conference (2010)

Following the ICAO 2010 High Level Safety Conference, the Interstate Aviation Committee (IAC/MAK) comprising many of the independent republics of the former Soviet Union, has presented a brief report on their assessment of real-time data transmission by aircraft over oceanic FIRs, in low density traffic regions and outside inhabited areas.

The ICAO Flight Recorder Working Group is already engaged in assessing the viability of alternative means of recovering flight data, and the ICAO has accepted the IAC/MAK paper as part of this investigation.

The paper, which has been translated by the IAC/MAK into English can be viewed at:-
IAC Flight Data Paper

References within the paper are made to the AF447 situation, and it would seem probable that the recent reference by Le Figaro to the Russian Army being involved in discussions with the BEA, could more correctly be described as Interstate Aviation Committee instigated.
mm43 is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.