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AF447

Old 15th Jun 2009, 06:01
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Mad(flt)Scientist: "If the FMGEC (or whatever its called?) is spitting out an ADR DISAGREE, is that going to then cause either the ADR parts to consider themselves potentially invalid, or other systems to do so? (The FMGEC in effect is "policing" the ADR data in that model)"

The sensors police themselves, but do not police each other. It's up to the data user to compare inputs and apply logic. If there is an airspeed miscompare among the 3 Air Data units for example, the user that receives and compares them will report the outlier to the Centralized Management Sytem, which relays ADR 2 Fault to the ACARS. The user will continue to use and compare other ADR outputs that are valid.

This is why the TCAS Fault stands alone in the reports at 02:10. It does not directly relate to the other faults that could be traced to iced pitot tubes. It may indicate intermittent cabling shaken by turbulence, a lightning strike to an antenna, or a myriad other possibilities, so it may point to the initial aircraft failure - or not.

GB
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Old 15th Jun 2009, 07:23
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TCAS Fault

Greaybeard:

As mentionned meany times before on this thread, "TCAS inop" is a resulting listed inop system in the ECAM "ADR disagree" STATUS page on the Airbus.

It is so decribed in FCOM Vol3, under the list of ECAM messages which present ECAM checklists/actions AND STATUS page.

IT SO HAPPENS THAT ALL THE ACARS MESSAGES from AF447 ARE CONSISTENT WITH AN ADR DISAGREE MESSAGE.

For the last time !
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Old 15th Jun 2009, 07:27
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French investigators (BEA) have announced a press conference coming up on Wednesday:

The BEA will be holding a press conference concerning the ongoing operations at sea in its premises at Le Bourget on Wednesday, 17th June, from 10 to 11 am.
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Old 15th Jun 2009, 07:53
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ADR Faults

Greaybeard:

When the system compares ADR data and sense one is going astray, it disregards and eliminates that source and only uses the 2 remaining.

ADR DISAGREE comes on after, when the 2 remaining ADR don't agree either. It's the PRIMs (F/CTL computer) that reject this data. Resetting them will not restore Normal Law.

Thresholds to reject an ADR : CAS and TAS, 16Kts for 10s, MACH 0,05 for 10s, ALT 3000ft for 1s, AOA 3,6 for 10s, Static pressure 5HPA for 1s. This means a sudden and significant variation of the ADR data will eliminate that Air data source !

Since the air data is corrupted, erroneous, wrong or along those lines, the FMGEC eliminates the CAS from the PFDs (SPD LIM Red flag, loss of "Vls").

Also, the A/C being in "Alternate Law without portections", the "flight envelope" parts of both FMGECs are considered INOP !! thus triggering a fault message on the FMGECs.

Note that the LOAD FACTOR protection is still working !!

Similar incident on another A330, another company, another day, but with same pitots, WAS attributed to icing of the probes! It lasted 2 minutes 20s, from 22h22,20s to 22h24,40s (reengagement of FDs and APs !!) and triggered ECAM messages and PFD flags similar to AF447 ACARS messages.
For 1m26s, the PF is in manual flight, without APs, without FDs, without FPV (Bird) and without A/THR.

Cheers

Last edited by captainflame; 15th Jun 2009 at 08:11.
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Old 15th Jun 2009, 08:31
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.... trying to catch up

Without good news reports in this part of the world and having tried to wade through 80 pages of the thread with intermittent success, is it fair to say the position is ????? :

The AF447, an A 330, departed from the cruise at FL350 without any radio calls.

It appears to have suffered an inflight break up or at least a partial break up which made it uncontrollable.

Potential reasons are overspeed or stall due to issues with speed sensing or violent turbulence in CBs. The aeroplane's composite structure may have some or no bearing.

AF are replacing some parts of the pitot system because of issues of icing on one type of pitot assembly found on some airbusses. Some other owners in the world fleet of A330 and other models of Airbus are following suit or may even be further advanced with retofitting.

A number of ACARS messages over a 4 minute period indicate various malfunctions or changes in system configuaration but without specialist access to the data it is not clear what that is telling us.

When / If the FDR and CVR are recovered that may / probably will, tell us more.

Without shooting me out of the sky for not having read all the posts (I have an airport to build) is that a fair summary ? or can somebody please help me understand the full story to date.

Dave Gittins

Last edited by Dave Gittins; 15th Jun 2009 at 14:11. Reason: corrections to add "stalling" and more about the pitots following some help from others
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Old 15th Jun 2009, 10:03
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Prevention

As I am not an expert in accident investigation I just wonder if the outcome would have been the same if......

1) All large transport aircraft operating under ETOPS rules were required to have "RealTime" weather information superimposed on the Map/Weather display. (Available on many exec jets)

2)The bottom line in event of multiple failures that the pilot is able to fly the aircraft albeit with cables and rods. (as in Boeing)

3) The Maximum Normal Operating Altitude be reduced from the manufacturers optimum altidude by 2000 feet.

The above would of course be at a cost.......BUT what are you worth?
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Old 15th Jun 2009, 10:05
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JD-EE - I am not a composites expert, and neither am I making any claims - I merely stated a personal opinion, that composites appear to rely on the resins for the composite material behaviour and abilities.

One has to examine all facets of a disaster, to improve knowledge. There are obviously, real, current reservations, about the effects of aging, long-term UV exposure, and contamination by fluids and other chemicals on composites durability and strength.
One thing I find rather amazing, and to me, quite simplistic - is the "tap" test on composites, to determine if internal de-lamination has occurred. One would think, that with aircraft, a much more sophisticated examination process would already be in place.

The following Airbus composites testing conference paper looks very impressive - but the testing appears to lack at least two (vital, I would have thought) additional features - the effects of UV aging, and chemical and fluid contamination on the composites, at the same time as destructive testing was taking place.

As we all well know, laboratory and factory testing is excellent in many applications - but rarely, does it take the place of actual in-field service, with all its additional factors that cannot always be considered, in a lab and engineering planning environment.
I notice that Eurostar (by Evektor), along with other manufacturers, insist that their metal frame is still superior to composites.

New Scientist article - Composite aircraft may hide dangerous flaws - tech - 22 November 2007 - New Scientist

Airbus Composite testing conference (2004) - http://www.aer.bris.ac.uk/comptest20...mptest_109.pdf
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Old 15th Jun 2009, 10:29
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In photos 1 and 3 one sees in more detail how the rudder failed. The bent mounting pins that are visible are bowed in the center, no doubt levered from their mounting lugs in the empennage, showing that the tail was pulled off by aerodynamic forces and not bent randomly or forward by impact forces. This again is consistent with the visible damage to the lower part of the rudder. We also see how the composite material has failed along the opposed cross hatch of fibers.
Really! That's terrific stuff

If I'm looking at the same (1 & 3) pictures of the VS you are then I'd say...

You could earn a fortune as a 'remote accident investigator' just using small low resolution pictures taken around the other side of the world, saving BEA, FAA, AAIB an absolute fortune.


== UV damage to composites ==

Bearing in mind the comments in several posts above:
Is this really a serious concern, when there are multiple layers of (UV resisting) paint and UV light however strong would doubtless penetrate one or two laminate layups?
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Old 15th Jun 2009, 11:06
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TCAS affected by Pitot Icing? Why should it be?

Graybeards said (at

post 1549 that:
"Ref: "There are five official, damning reports on A330 and A340 aircraft operated by

major airlines suffering complete failure of all flight instruments in flight. Pitot probes

iced up in meteorological conditions at night, by day, in cloud and in clear air."

The early failures reported by AF447 ACARS all seem to be explainable by iced pitot tubes, save

for the TCAS Fail. TCAS does not use airspeed, just altitude via the transponder.


Air data Altitude failure will cause the transponder to revert to Mode A. I'm not sure if it would report failure of its altitude input to the CMS/ACARS, but it didn't report a Fault.

Transponder reversion to Mode A will not cause a TCAS Fail condition, but a TCAS OFF condition.

Therefore, we have a TCAS Fault that occurred nearly simultaneously with the airspeed sourced faults, but unrelated."
It would appear that some are flummoxed by the TCAS failure msg on ACARS (TCAS needing and acquiring static pressure only).
Correct me if I'm wrong but, depending upon exactly how the ADIRU derives and passes the static pressure, the pitot icing failure may be related.
i.e.
Pitot pressure = dynamic pressure (i.e. IAS) plus static pressure

The ASI derives a normally correct airspeed by balancing the pitot derived static against the static pressure sensed from the static ports (and fed into the ADIRU as a digital signal by a transducer).

IAS (or dynamic pressure) = pitot pressure minus static port sensed pressure

So if your static lines ice up due to trapped water freezing as you climb, then those two differently derived static pressures will become increasingly unequal and the ASI will wind back to zero (in a climb/opposite in a descent). In the cruise, the IAS will simply "freeze".

So it depends which static pressure is being fed to the ADIRU and at what stage? Is it simplistically static port sensed pressure (with its built-in pressure error) or is it the resolved average of the two differently sourced static pressures? Once the pitot ices over, that average would be duff.
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Old 15th Jun 2009, 11:16
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Captain Crunch -

Nice post.....[#1573] UNTIL those last two paragraphs.

1st - We'll see if the appointment was "wise indeed".

2nd - Simply isn't gonna happen.
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Old 15th Jun 2009, 11:28
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Photage from the debris found

Cabin crew seat found floating in the Atlantic

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Old 15th Jun 2009, 11:42
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Composite testing

Just as a general reply to all the non-composite experts and non-stress engineers.

Yes, when we test composites we artificially age and damage test pieces. We also typically test in a hot wet condition (humidity in particular has a negative effect on the structural properties of CFRP).

Can we all stop making out that the engineers (i.e. me) have no idea how to design composite structures. After 20 years of design and testing we do.

The rudder failures that so many of you are so excited about were design failures not composite problems. My point being that ingress of hydraulic fluid requires something to leak the fluid on to the composite.

And finally, whoever it was that brought up that some manufacturers say composites are no good. This will probably be because they are not capable of manufacturing composite primary structure. Airbus was saying that composite fuselages were a bad idea, right up until they canned the old A350 program and restarted with a composite fuselage.

Can I please ask that anyone writing a post that begins with the phrase "I'm not an expert" dosn't. There are a lot of experts on this forum but it's annoying to have to trudge through the wild speculation to find the interesting/insightful comments.
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Old 15th Jun 2009, 11:52
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In the late 1980s, McDouglas bought back the high time DC-9, fuselage #2, and subjected it to pressurization cycles, bringing the total to 200,000, IIRC. Has similar testing of high time composite components been performed?
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Old 15th Jun 2009, 11:54
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All very true, but as I have studied composite construction and use for 30 years, I can no longer remain silent as I read this thread.

Composites are safe.

Composites age and we have few methods of assessing them as they do so.

But what a lot of you are missing is that these composite tails have a history. Have you forgotten the litres of water drained from AA Airbus tails/ have you forgotten the issue of internal collapse of the structure due not just to oil based contaminants, but also the effect of repeated freezing and expansion in flight cycles of ingress affected composites.

And what about the manufacturing flaws - flaws over and above a critical size. Who is going to look for those. What about the repaired new fins that are alleged to have existed.

The cause of this accident remains unknown. until we know ALL the facts, we will never know what happened as a casue or a consequence.

Best wait until then before we unpack past accidents and past debates.
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Old 15th Jun 2009, 11:58
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Originally Posted by Dave Gittins
It appears to have suffered an inflight break up or at least a partial break up which made it uncontrollable.
Potential reasons are overspeed or stall due to issues with speed sensing or violent turbulence in CBs. The aeroplane's composite structure may have some or no bearing.
- in answer to your request, DG, I would say the jury are still undecided on this. It is even possible (as far as I can ascertain) that it might even have attempted to ditch.
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Old 15th Jun 2009, 12:07
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I am totally technically uninformed apart from osmosis over 30 years in the industry plus being the son of a LAME and will sign and post that.

In this tradgedy, 228 souls have been lost.

My 2 bob's worth is that I feel an aeroplane has been bitten by "Coffin Corner" being too heavy and too high for a warm pool of air sucked up by CB's and found itself in a stall or overspeed conundrum.

The pilots may well have chosen a "box canyon" way out that overcomplicated the situation that led them directly into an unavoidable CB and the coup de grace. The flight deck crew took that knowledge with them.

The bottom line is we have lost some wonderful aircrew and passengers.

They seem to have been a little lost in the analysis.

Hopefully no blame will be appointed or apportioned until some solid facts come to light, and Airbus should not be hung over the Coffin Corner side of things until all facts are in.

The last major CC events were from memory transcontinental Boeing 727-200s.

Rest peacfully good souls on board AF447. May your loss not be in vain.

EWL
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Old 15th Jun 2009, 12:22
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Re several posts concerning the pilot making inadvertent inputs on the sidestick in turbulence:

My instructor in Toulouse urged us to treat the sidestick as you would a dog s***, ie, only touch it if you have to, as theoretically the fbw will hold its current trajectory. But easier said than done, most especially in AF's predicament....
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Old 15th Jun 2009, 12:26
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Overtalk: "So if your static lines ice up due to trapped water freezing as you climb, then those two differently derived static pressures will become increasingly unequal and the ASI will wind back to zero (in a climb/opposite in a descent). In the cruise, the IAS will simply "freeze"."

Why are you introducing static line freezing, when the only known suspect is the pitot tubes? Airspeed needs static pressure, as by definition it is static pressure subtracted from ram air pressure. Altitude, (static pressure) does not need Airspeed, except for trimming correction at high angles of attack. Altitude errors provide a whole different list of faults.

There is nothing in the ACARS reports suggesting Altitude Fault or disagree. Remember, the CMS report to Maintenance is a guide to the mechanic on which box to change on a short turnaround, so it may say ADR Fault, or ADR disagree. It doesn't say Airspeed Fault, or Altitude Fault. Those are left for the mechanic to find in the BITE, Built-In Test Equipment, testing.

Beyond that, a Pressure Altitude Fault will not trigger a TCAS Fault, as the Transponder is in between, relaying own ship altitude to the TCAS. Again, a Pressure Altitude Fault will cause the transponder to revert to Mode A, putting the TCAS in OFF mode. Remember the Legacy collision in Brazil? The transponder in Standby had put the TCAS in OFF, and didn't trigger a TCAS Fail, that the crew would have more likely seen.

GB
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Old 15th Jun 2009, 12:48
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TCAS Inop is Not TCAS Fail

Capitan Flame: "When the system compares ADR data and sense one is going astray, it disregards and eliminates that source and only uses the 2 remaining."

So why wasn't there an ADR Fault transmitted at 0210, if that were the source of the TCAS Fault as you say?

There has been no rational symptom of Altitude Fault shown in all these pages. All the ACARS reported faults downstream of the ADR are traceable to Airspeed Fault, save for the TCAS. Indeed, in the prior incidents, airspeed indication was lost or faulted, with no mention of altitude indication fail or disagree.

GB
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Old 15th Jun 2009, 12:50
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Dave Gittins, I replied to you recommending that you read this story, which will do a lot to bring you up to date:-

Air France crash: What is known so far | csmonitor.com

For some reason my post was deleted. Maybe because I went on to make some further points. So I'll leave it at that.

Just 'click,' mate........
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