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AF 447 Search to resume

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AF 447 Search to resume

Old 23rd Jun 2010, 16:46
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Saturn and Lonewolf50.. I agree,that was my point too..
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Old 23rd Jun 2010, 17:22
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butterfly:

If you get a chance, read the weather analysis at Tim Vasquez site, in detail. If you have already, sorry, I am late to the party on that bit of insight.
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Old 23rd Jun 2010, 18:48
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Originally Posted by SaturnV
The meteorology is dynamic, and I don't believe I've seen a mapping of the atmospheric conditions existing at the time that LH and IB were on the track post ORARO.
You have it here below for a 45 minutes window.
As we can see, the system was pretty similar for LH, AF447 and IB.
Now, I could also take the liberty to place a 55000 feet CB for any of those flights.
The meteorology is dynamic and that's why a deviation 10 miles to the left can be only 3 miles 20 minutes later or 30 miles to the right another further 12 minutes.









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Old 23rd Jun 2010, 20:32
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jimbeetle

June 1 search grids


I believe mm43 said the westernmost grid boundary on the wider box was 10 NM to the left of the track.

June 2 (includes the boxes flown on June 1)

Unfortunately, the debris noted on the chart was not from AF447, and the Brazilian optimism was unfounded.

June 6


June 6 recovery of first debris and bodies. (square at the bottom is the last reported position)


Cumulative search grids June 1-5

Disregard the circle centered on the last reported position.

__________________
CONFiture, thanks for the images.
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Old 23rd Jun 2010, 22:36
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Originally Posted by jimbeetle
Anyway, all that is basically an aside to my main point -- not everything floats -- some hunks of the airframe are somewhere close to where AF447 impacted. And my assumption is that is somewhere not far from the LKP. I guess I still can't wrap my mind around the BEA assumption that the FDR can CVR would drift so far.
I believe that the dominant opinion here on PPRuNe and at BEA, is not that the recorders drifted far from the point of impact, but that the point of impact is not close to LKP. That does not mean that the point of impact is not close to LKP, just that is it believed to be elsewhere, and that is why the search has been conducted elsewhere.

From what I have learned in this thread, the point of impact is believed by BEA to be somewhere inside of a 40nm radius of LKP, because the position reports were transmitted at 4min intervals and 40nm represents the distance that the a/c could cover in 4min at cruise speed.

The area north and west of LKP has been searched most thoroughly exactly because that is the area where the point of impact was calculated to be, based on backtracking the drift of the floating debris. The drift models are based on the available wind and current data, and assumptions about the exposure to air and to water of the various bits of debris. This approach is based on BEA's belief (from examination of recovered wreckage) that the a/c impacted the water intact, and thus all debris drifted from a single point.

The goal of the search is to locate the large parts that sank quickly (mostly in place under the point of impact), and then to fan out from that point to find individual items. So far, no debris has been identified on the bottom, so the working assumption must now be that the point of impact is not in the area already searched. Because the area directly under LKP has not been thoroughly searched, the possibility that the a/c is under LKP has not been eliminated.
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Old 23rd Jun 2010, 23:19
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Originally posted by auv-ee ...

... the point of impact is believed by BEA to be somewhere inside of a 40nm radius of LKP, because the position reports were transmitted at 4min intervals and 40nm represents the distance that the a/c could cover in 4min at cruise speed.
I think you meant to say,

" ... because the ACARS reports were transmitted at 1min intervals and 40nm represents the distance that the a/c could cover in 5min at cruise speed."

mm43
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Old 24th Jun 2010, 01:41
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Originally Posted by mm43
I think you meant to say,

" ... because the ACARS reports were transmitted at 1min intervals and 40nm represents the distance that the a/c could cover in 5min at cruise speed."
I think you are being charitable. I wrote what I recalled but evidently that is incorrect.

Reviewing post 1178 by GreatBear (http://www.pprune.org/5715414-post1178.html), assuming that analysis is largely correct, I see that the ACARS position reports come every 10 minutes, and the reason for the 40nm circle is that ACARS fault messages started soon after the 0210 LKP report, and ended 4-5min later, when they would have continued had the a/c not ended flight. Is that about right, or am I still missing something important?
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Old 24th Jun 2010, 03:00
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While on the subject of being charitable, there has also been an assumption made that the a/c ground speed was less than 478KTS, whereas there is a possibility that a prolonged over-speed event took place and the manner in which the a/c impacted with the sea was as a result of a deep stall induced during a recovery attempt.

I doubt the over-speed part of the above, and believe that we should be looking very closely at any of the area within the 40NM radius that has not been visited by TPL's, the REMUS AUV's and the ORION side-scan sonar (SSS). More particularly those areas that didn't receive an initial aerial search.

Also, the SNA "Emeraude" doesn't appear to have had her sonar operating at maximum efficiency in the period up to 30 June 2009, and those areas covered by her in that period deserve a closer look if they haven't been subsequently covered by other means. Without being privy to the [classified] operating depth of the "Emeraude", its not really possible to be much more charitable with regard to her efforts.

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Old 24th Jun 2010, 03:11
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I'd like a little assistance in ACARS reporting criteria. A while back I mentioned an old post regarding the normal law protection mode having the potential to cause a pitch up into a stall upon bogus sensing an approaching violation of the Vmo/Mmo limit airspeeds. If at time ~0208-0209Z before the primary string of ACARS events, the aircraft simultaneously filled all 3 pitot tubes with water or ice from one of the Cb cells it encountered thus plugging all bleed ports in the pitot tubes and then flew into colder ice that plugged the pitot inlets, it would then be possible to pressurize all 3 pitot systems in a fairly synchronous manner from water vapor pressure in the presence of pitot heat.

Would such an event (an apparently valid overspeed indication) show on the ACARS reporting? The original post by PILOTAYDIN indicated that there were no ECAM messages in the simulator session he participated in. I believe CONFiture earlier indicated that such a pitch up would require ace level systems knowledge to halt before it caused a stall.

If ACARS would tattle on activation of the Vmo/Mmo protections then we can pretty well eliminate a Vmo/Mmo protection induced pitchup prior to the current known ACARS events.

It would be useful to conclusively eliminate such a scenario since otherwise AF447 could be already on its way down in a deep stall at LKP and this would change the search strategy.
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Old 24th Jun 2010, 11:14
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OK Machinbird, it's time I do a little learning.

You have a flight control computer monitoring the instruments. How often does it scan them? If it's not too obsolete a design scanning instruments 10 times a second should be quite easy and any "buzz" that might introduce to control operation would be damped by the mass of the aircraft. They might even manage as many as 100 scans a second.

But 10 is a reasonable sounding, to me, bottom end. Am I in the ballpark with this swag? (Scientific Wild A** Guess)

If it is, that means all three probes would have had to plug up synchronously within a fraction of a 100 ms or less scan interval. That means a virtually instantaneous transition from open bore to plugged for all three probes within the same scan.

I'm untutored here; but, two things stand out here as just a little fantastic for my engineering tastes.

Going from open to clogged that fast without literally dunking it in a fluid of some sort bothers me as a concept, especially at an altitude testimony here suggests makes the Sahara Desert look like the Riviera except possibly for very small super cold ice crystals. The plane would have had to fly into a front of just the right shape of a density that would have severely shaken even the loaded mass of AF447 pretty badly. And it must have had just the right shape to turn the trick.

Alternatively, and possible even harder to imagine, we would have all three probes progressing over say several seconds in such perfect synchronism to escape being noticed in the 10 times per second or faster scans.

Based on my supposition of the computer's scan rate the three simultaneously clogged probes scenarios beggar my imagination. And the thought that the pilots would not notice it happening with the sudden penetration of a very thick layer of moisture in some form blotting out the stars "does not compute." They'd have had to be comatose or something.
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Old 24th Jun 2010, 11:54
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CONFiture

The left track is believed to be the LH flight. The BEA has not identified it, only to say the plane was AMDAR equipped. The FL is 325 In the interim report, the FL for the LH flight is not given. No indication of which flight is the track on the right.

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Old 24th Jun 2010, 11:55
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Hi JD-EE. I think you have overcomplicated the situation a bit. There are smoothing functions after the initial reading of the sensors. The data from the 3 airspeed channels are compared for consistency and must be within X knots of each other to be considered acceptable. The 3 channels are then averaged in some manner and that number is used as the airspeed. If any channel is out of the acceptability window of x knots for y seconds, then it is rejected and the remaining two channels are used as the basis for airspeed. If those remaining two channels then fail a consistency check, that is when all heck breaks loose.
The system is going to hang together for a little while before data inputs begin to get rejected (at least y seconds).
I'll have to dig out the reference for airspeed data processing again and post it.
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Old 24th Jun 2010, 13:11
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Is this new or old information about Airbus loss of airspeed emergency procedures??

Air France Crash Investigator Examines Airbus Emergency Drill - BusinessWeek

There seems to be a disagreement among the parties about something fundamental.
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Old 24th Jun 2010, 13:41
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SaturnV,
The references are in the Interim Report #1 on page 65, and I think you did quote them yourself earlier.
  • LH507 B744 20min earlier FL350 Left Deviation by 10NM
  • AF447 A332 FL350 Last Known Position 3NM Left of the Airway (That last info has still to be explicitly mentioned in a BEA Report ...)
  • IB6024 A34? 12min later FL370 Right Deviation by 30NM

The job of the BEA is to analyze all of the available information, not to keep some under the bed. But that idea of the monster CB in which the AF447 crew flew blind fully could be too convenient.
I want to hear more on those Pitot tubes and how all the Pitot events have been dealt with at the company level, the manufacturer level, the regulatory authority level ?

JD-EE,
Three probes can block at a similar rate, it very unlikely, but it is not impossible, enough that the Manuals and Procedures talk about it.
How many times did we hear during the pre departure briefing : "In the very unlikely event of a depressurization or a ditching ..."
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Old 24th Jun 2010, 14:07
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In the Business Week article, the Air France pilot who was quoted clearly implied that the response to loss of airspeed signal is to fly the aircraft without changing pitch. Does he mean that the pilot ought to override the autopilot, or simply to trim, or retrim, a particular nose pitch/attitude?
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Old 24th Jun 2010, 14:26
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Analog And Digiltal Data

JD-EE and others

Permit an old software designer to make some comments. For your knowledge
I am no pilot, the closest I have come is by designing and debugging software for high altitude rockets at Esrange. Those programs were only running once and for a short time - any problem and the rocket would self-destruct.

Air data (pressute, temperature, etc) in the A330 are measured as close to the ports as possible and immediately digitized (some types of very accurate probes even present their value initially as a number). From the schematics available for the A330, this primary air-data handling is done by the ADM-units - one for each probe. The ADM-units are connected to the ADIRU-units by signal cabling. On these cables data are requested and/or transmitted in digital form using a standard protocol. The use of a common bus reduces the amount of wiring needed.

The tranfer of data can usually operate in three ways:
Clocked mode: A central system clock triggers data transfer at given times between the various units via the common data bus. Each unit then has its own time window for communication
Polled mode: A unit higher in the system polls a unit lower in the system. The lower ranked unit then responds with either a "no data" answer or sends the requested data. Thus the higher unit controls the use of the common bus.
Interrupt mode: A lower unit can send a "data available" signal on a dedicated interrupt line to request attention. Also in this case the higer unit controls the use of the bus. However, I don't think this mode is used on large aircraft because of the extra wiring needed to carry unique interrupt information to and from all units and the rather slow variation in measured data probably doesn't require interrupt mode.

In none of these cases is any higher ranked computer "scanning" analog signals. However, such scanning may occur in some simple on/off cases, e.g. the postion of various switches. This will need additional wiring,

As far as I have understood, the A330 systems don't operate in a clocked mode. This makes debugging of software much more difficult than in a clocked system. An old proverb states that "given the right data all computer systems will give the wrong result". Regardless of all testing and verification, some strange bugs may still hide in the code. There is at least one published example of this kind of bug found hidden in several versions of code used in an ADIRU unit during a long time.

Regards
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Old 24th Jun 2010, 15:01
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emergency manoeuver/UAS memory items

Hi Auv-ee, Aguadalte and HN39
This emergency manoeuver (5░/CLB) of the UAS procedures mentioned in Business Week is the one suppressed at cruise altitude by Air France 5 days after the AF447 crash. It is in line with HN39 computations (Mach number decreasing close to the lower boundary of the A330 flight envelope at high altitude), and with the contribution of Aguadalte. But the crew involved in the BBC simulation successfully managed the UAS applying this memory item (5░/85% in the BBC simulation, to compare to the pitch/thrust tables in the QRH: 3.5░/78.9% if I remember correctly). The 2nd interim report states that this memory item has not really been implemented in the past UAS events (all planes remained in their flight envelope, even when they decided to initiate a descent when the stall alarms sounded): the AF447 may have been the first known aircraft to apply this memory item with the fatal consequences we know ?
Jeff
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Old 24th Jun 2010, 16:32
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Hyperveloce:
Although we are only guessing, yes, I think it is possible that, that AI emergency procedure (if followed) may have contributed, especially in a turbulent environment, to a low speed stall at high altitude, in the AF447 case.
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Old 24th Jun 2010, 16:43
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..but what bothers me still, is that I don't see any reference to the 2:13:14 ACARS message in the last BEA interim report:
.1/FLR/FR0906010211 34123406IR2 1,EFCS1X,IR1,IR3,,,,ADIRU2
(1FP2),HARD
Does anyone knows the technical explanation for this message?
Why don't we see an explanation for this message in the last interim, as it was done for other messages (from page 35 to page 41 in the report)?
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Old 24th Jun 2010, 18:58
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There is a significant mis-understanding occurring here regarding the UAS QRH drill.

Someone here has already hinted at the problem - the UAS drill caters to failure of airspeed information at low altitudes, (as a result of the Birgenair and Aeroperu B757 accidents). The inital pitch attitude of 5deg, under the configuration anticipated, is reasonable.

The memorized portion of the UAS QRH drill does NOT require a "5deg" pitch attitude above MSA or circuit altitude. The last memorized item at the bottom of the drill states:

"When at, or above MSA or Circuit Altitude: Level off for troubleshooting."

The read-and-do section of the QRH drill then states:

ľ GPS ALTITUDE ............................................................ .........Display on MCDU

To level off for troubleshooting:
ľAP/FD ............................................................ ......................OFF
ľA/THR ............................................................ ......................OFF

Then the drill requires an assessment of configuration for which it provides pitch and power settings:




NOTE that between FL 200 and FL360, the Speed is 260kts and the required Pitch and Power are stated as "3.5deg/71.9%N1".

Assuming appropriate training and airmanship, I cannot imagine that an experienced crew would, at FL350, slavishly pitch the aircraft up to 5deg upon loss of airspeed information. They would, I expect, instinctively know what would happen if they did this, and changed what was working well, (in terms of pitch and power) moments before the loss of airspeed information.

Although Bloomberg/Businessweek reported it, the original story leaves out important details regarding this drill and speculates without either understanding the drill and the airplane or knowing all the facts, which remain locked in the DFDR and CVR.

PJ2

Last edited by PJ2; 24th Jun 2010 at 19:11.
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