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Old 18th Jun 2009, 21:41
  #1901 (permalink)  
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Just a word to clarify that ISIS doesn't receive "attitude from internal gyros", it receives inputs from ADIRU1 and 3.

The problem, as said earlier, is that ISIS containts are classified. I know it sounds weird but again, no one opens up this box !!

While it is true that it gets inputs from ADIRU 1 and 3, it is also true that it contains gyros !!
What inputs from ADIRUs ? I have no idea because the Airbus doumentation does not describe this. It could be to compare data, or to receive inputs from AOA and such....

It also is linked to ILS receiver 1 for example as you can display the LOC/GS sacles and diamonds.

As a matter of fact, ISIS needs to "align" its ATTitude on power up, and has an in flight ATT re-initialization button as well.

So the GYRO, Attitude information IS definitely self contained !

It is a BACKUP instrument. We know how to use it, we know what can go wrong with it, we do not know how it works inside !
Do we really need to ? not so sure.

By the way it is powered by BOTH the DC ESS bus and Hot Bus 1
My apologies, I may be wrong. (damn! I hate when I'm wrong) And I hate (!) that "need to know - nice to know", Airbus philosophy )
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Old 18th Jun 2009, 22:16
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Exclamation "Everyday Equatorial Weather"...ahem

Quote from Captainflame:

"Weather analysts report that the Convective weather pattern that night in that area did not present anything out of the ordinary, everyday equatorial storm system."

This is just the possible complacency I have mentioned in previous posts.... there is no such thing as 'everyday equatorial storms'. These storms happen frequently and their activity vastly exceeds the structural integrity of most commercial aircraft. Full Stop! Wise up please to some sort of 'go-ahead-itis'.

NO COMMERCIAL AIRCRAFT SHOULD GO WITHIN 100nm LATERALLY of CB - ICTZ (Tropical Cumulo-Nimbus clouds) activity.....for any reason...FULL STOP. NEVER, EVER, don't even think about it.... or trying to overfly it. That is from MANY years experience and many grey hairs of wisdom!!

Many pilots/carriers have lived to tell the tale of bizarre encounters in this area. ICTZ CB activity that spans the globe around the equator is where Hurricanes/Typhoons form. I strongly feel that any FD crew operating anywhere in this area should be given specific AVOIDANCE weather understanding. Daylight views are one thing, however, night many long-haul flights operate over....all one relies on is forecast, PIREPS, experience and WX Radar.

No matter how fancy and colourful the radar is; unless you are trained to interpret it accurately and trust that it is accurately reporting; you only have 'historical' data to go by. Vast activity happens in mere seconds at equatorial levels from a few hundred feet AGL to over 50,000ft.

At night, even with the most sophisticated WX radar, reports etc., what you see on screen is only an INTERPRETATION of what is going on. Dark red means dark red. Light green means light green. Both could indicate activity beyond the structural capacity of the commercial aircraft. Maybe this is also a speciality with new part-composite structures, such as used by Airbus & others in contemporary designs....whereby....the actual structure is not designed to 'X' structural is designed to be used in conjunction with 'damping devices' such as spoilers operating to assuage (lessen) vertical forces, for example.

We can get into many complicated design/structural issues if we want in this forum. However, there just seems a primordial lack of concern about flying into weather in the ICTZ, specifically anywhere near CB reports.

If you don't go anywhere near (as above), even if that means diversion/turn back you will have many happy landings and happy PAX (and fellow crew), who haven't endured many long minutes/hours of uncomforteableness/fear.

I rest my case.

Aiming for 'smooth as Silk' until I die and then let me be lifted to the heavens from mother earth in the widest ICTZ storm....sorta thing, guys & gals.


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Old 18th Jun 2009, 22:20
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rates of drift according to Dorian B 20.47 today

Looking at DorianB`s charts (20.47, today thursday june 18)
With a certain amount of approximation....
I take estimate last position report as 0210/04
Distance of first centre of debris June 06 from above,66km
Distance travelled June06-07...........................9km
........................ June 07-08..........................30km
.........................June 08-09...........................35km
.........................June 09-10...........................50km
Any drift from Jun01-06 may be guessed at roughly 13km per day if impact at Last Pos Rept....
OR if drift was 9km per day or less ,impact was just 20 km from LPR,
At the most around 50-60 km beyond LPR if practically no drift; less than 4 mins at Mach.8
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Old 18th Jun 2009, 22:36
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This is reassuring (not): "An A340 operator reported the loss of ISIS followed, during the same flight, by the loss of all Electronic Instrument System (EIS) Display Units (DU). The failure mode of ISIS has been identified as a time counter fault after 145 hours of ISIS continuous power supply. AD/A330/28 (DGAC AD F-2004-117) mandates the operational procedure to recover lost EIS Display Units, pending a new EIS standard addressing the misbehavior. Situations where EIS DUs and ISIS are simultaneously unavailable may result in hazardous consequences in certain phases of flight. This Directive requires a periodic on ground-reset procedure to prevent the ISIS failure by clearing the time counter." AD/A330/42 Integrated Standby Instrument System 13/2004 The temp fix was to cut power to the ISIS for more than 5 secs so it would reset.
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Old 18th Jun 2009, 22:41
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lomapaseo, PJ2

Yes, there was quite a discussion before on the mobile crew rest (MCR), which posts have been deleted, including mine, one of which gave the link to the similar MCR on the 340 now reposted by PJ2. Thanks for that.

In the previous posts it was confirmed by a fellow poster, obviously in the know, that MCR on Air France's 330's are positioned below deck at the hight of the 3L/R doors just aft of the wing box.

The debris photo of part of the MCR outside panel as reposted by lomapaseo seems to show heavy underside damage, possibly caused by this part coming loose from the structure that is locked in the floor of the hold.

Just as lomapaseo theorises that this supports inflight break up, I'm still there with a theory of a low vertical and horizontal speed (mostly) intact, tail first impact (making the V/S breaking away, while damaging the rudder base), followed by a further deceleration in which the a/c broke aft of the wings, releasing the cargo container there (inter alia).

Obviously the real and heavily filled cargo containers crushing the MCR, allowing the part on the photo to break free.

Just trying to see what could have happened.
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Old 18th Jun 2009, 22:43
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I am surprised that timer wraparound faults are not addressed better.... It is possible that this is a similar issue here which lead to a tragic ending because it happened in bad weather.
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Old 18th Jun 2009, 22:44
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I was merely refering to weather analysts pont of views. TO THEM it wasn't any particular CB cluster. As you say they happen mean like in "everyday" ?

It was in response to a previous post from a non aviation professional who was mentioning typhoons or hurricanes !!

I was certainly not implying that these things shouldn't be avoided.

So relax, avoid as you wish, retire soon, happy landings !
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Old 18th Jun 2009, 22:55
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Swept wing stalls

PJ2, ttcse, others,

Not familiar with the referenced book, my experience comes from having an interest in the manner since I like aerobatics, working in the industry 30 years, and proprietary manufacturer data.

The tips of swept wing transports stall first due to induced flow upwash angles. You all know the leading edge produces negative pressures. Pick a wing station inboard. As the air passes next to that inboard station, but outboard from it, it senses that negative pressure and starts flowing upward. Therefore, that wing element sees a slightly higher local AOA. This follows for each chord wise strip, or tiny section of wing, and by the time you reach the tip, the induced upwash can be 2-4 degrees higher than the reference airplane AOA at cruise conditions. Wing twist is set by this for best efficiency. As you increase AOA in the clean configuration, the tip will stall, with an attendant nose up pitch break, and is a terrible stall characteristic. Good reason for not stalling a swept wing transport in the cruise configuration. True now as it was in the beginning.

Tip stall is mitigated by the use of flaps and slats for the T.O. and lndg configurations, and are used to tailor acceptable stall characteristics.

Flat spins are sensitive to cg position and power effects. The aerobatic single engine airplanes I've flown won't go flat without almost full power. This is due to prop wash increasing elevator power, forcing the tail down. Some of them are driven by prop centrifugal force and torque, like the Russian monster, the Yak-52. Some will recover very quickly just by chopping power and applying corrective controls. The Yak-52 wants a few more turns before it recovers once it's wound up.

You don't have a prop on an airliner, but there are underslung engines providing a nose up moment. Is it enough, maybe, nobody's ever done the math. One thing though, you don't want these big airplanes spinning. Boeing experience on the 707 taught everyone that. The 707 did a snap roll a couple of different times. They recovered the airplane due to the design requirements of the time. Think they certified under CAR 4a. Much more demanding than the current regs, so the 707 is a tough bird, still significantly damaged, but it returned the crew.

Not hard to envision current airliners tearing themselves apart in a spin. The engines would go, moving cg aft, maybe it goes flat. And/or the empennage would go, and/or the nose breaks lose. Who knows. The crew would be under tremendous g load in a fully developed spin. Due to inertia and mass, it would take a couple of turns to really wind up.

Hope this helps.
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Old 18th Jun 2009, 23:09
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Very interesting article on the US Coast Guard providing drift analysis technology and support:

Air France Flight 447 Recovery Assisted By U.S. Coast Guard And
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Old 18th Jun 2009, 23:11
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ClippedCub - yes, it does, many thanks for your time and effort. We'll see what else emerges in the next weeks.

Sorry, the book I'm referencing is "Handling the Big Jets" by D.P. Davies, first out in 1967, last ed. 1971 - can be found online and is the best (and, perhaps aside from "Flying the Wing"), only book on handling large transports which doesn't cater to manufacturer spin but is instead written with great knowledge and even humour, to airline pilots.

It is both the easiest thing and a very difficult thing to conjur a series of circumstances from the first hint of difficulty to initial degradation to the beginning of the actual accident sequence. One thing is for sure - there's a lotta people out there including cockpit crews, "into the books".
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Old 18th Jun 2009, 23:18
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"Handling the Big Jets" by D.P. Davies
If it's stood the test of time, must be good. The physics don't change so the book will still be valid.

Another geometric characteristic that would promote flat spinning in airliners would be the fuselage cylinder ahead of the wing. At extremely high AOA, it would produce a drag force in the positive lift direction ahead of the cg.
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Old 18th Jun 2009, 23:20
  #1912 (permalink)  
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Originally Posted by captainflame
we know what can go wrong with it,......................
Do we really need to ?..................
What is apparent here is that no-one DOES seem to know what can go wrong with it, so the answer to your second question is a resounding YES!

Wth such a spider's web of computer cross-chat, it is surely vital to have some sort of independent backup for that 'Titanic' moment when the infallable safety net breaks. Even basic uncorrupted attitude would be a start. TAS and ALT are not essential, you can live without profile rate for quite a while.

Originally Posted by PJ2
While one can guess, I do not know what is meant by the terms, "accelerometer" and "gyrometer" in the "ISIS" box. The key in that understanding is, of course, whether or not if ADIRS 1 & 3 fail, does the standby horizon fail?
- up until the last week or so I had, in my blissfull ignorance, assumed that ISIS would have a mini-platform, thus requiring those "accelerometer" and "??gyrometer??" in the 'box'. Now I'm left wondering.
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Old 18th Jun 2009, 23:47
  #1913 (permalink)  
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ISIS Attitude information is independant of all three of the ADIRUS.

Regarding the ADIRU 1 + 3 inputs into the ISIS:

The ISIS has 2 possible power sources (ESS and Hot Bus)

When passing through 50kts the power source for the ISIS changes from the ESS to the Hot bus. How does it know when to do this? The airspeed information from ADIRU 1 + 3. Hence the reference to ADIRU 1 + 3 inputs.

This thread has gone interglactic in its amount of information. It reads like 80 people yelling at once. Good luck to you all and I hope we find the cause soon.
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Old 18th Jun 2009, 23:47
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AIB Presentation 2003,

Considering connection with IR Bus ADIRU 1 / 3,
besides the supply switching.


Two ARINC 429 high-speed buses provide the ISIS indicator with the ADIRU ground speed information.
This information is used as a backup source for ISIS ground/flight condition.


Optional magnetic heading.

The magnetic heading provided by the IR1 or IR3 enables the display of the magnetic heading information.
In case of detected failure of the selected ADIRU, a red HDG Flag is displayed in place of the magnetic heading indications.


Last edited by A33Zab; 19th Jun 2009 at 07:06.
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Old 19th Jun 2009, 00:29
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Just a word to clarify that ISIS doesn't receive "attitude from internal gyros", it receives inputs from ADIRU1 and 3.
Someone please clarify.Is the ISIS a mini PFD or a genuine standby instrument?This is at the heart of the matter.Forget wreckage,concentrate on what the crew had available to them in the last minute.This will tell the story.

This is what I could gather :
at 0210Z : from bottom to top :
- FlAG ON Capt PFD
- EFCS2...1..EFCS1...AFS
- EFCS1...X2..EFCS2X

at 0211Z :

at 0212z:
- IR2...1,EFCS1X, IR1, IR3

at 0213Z :

at 0214z:
- ADVISORY.../...
Above is ACARS summary from Lemurian.

Question(s) for Airbus pilots:

a)data for triple pitot heat failure is surely relevant here;not what happened but it amounts to the same thing.In that case,what it says is that one of the ADR's should be turned off to trigger the ECAM "ADR DISAGREE".If icing anticipated,turn off 2 ADR's?Why?Does it not follow that the 02:12 ACARS message "NAV ADR DISAGREE" was in response to pilot action?ie pilot de-selects ADR(s) OFF.If the multi-pitot failure/blockage theory is correct,theres nothing for the computer to find disagreement with.Theyre all three plain wrong.So the pilot must intervene to generate the ECAM warning.Is this correct?

b)It mentions it again for dual pitot heat failure;the inherent risk is that the computer will lock out the one remaining good ADR.So the pilot must turn off one of the faulty ADR's and trigger the NAV ADR DISAGREE which in turn will lead to ADR CHECK procedure.
So NAV ADR DISAGREE warning can either be computer-generated OR pilot-action generated(Pilot switches OFF faulty ADR).Correct?

d)Now that one ADR has been disabled and the ECAM warning generated what next?For ALT LAW to kick in,there must be disagreement between 2 remaining ADR's,either speed or AoA.If speed disagrees in the remaining two ADR's,crew fly unreliable airspeed procedure.If speed does not disagree,AoA is culprit,and crew ignores spurious STALL warnings(Air Caraibe).Is that about right?

e)The ECAM message in the Air Caraibe incident was FCTL ADR DISAGREE,not NAV ADR DISAGREE.What does this indicate?How telling is it that both 447 and Caraibe began with AP/FD disconnects?

f)In ALT LAW roll control is same as for Direct?Please enlighten.Sensitivity issues?

g)With a CAS of say 90 knots on all 3 ASI's at time of RUD TRAVEL LIMIT warning,could rudder deflection of 31 degrees been mandated by the computer as the limit?

h)What is the QRH procdure(2.20) for flight with all 3 ADR's out.ECAM apparently only covers single ADR op?Would 3 ADR's out=Direct Law?

I know Im out of my depth(never piloted/travelled on an Airbus) but no-ones asking questions that relate to what the crew had available to them in the last minute.What did they see??

Last edited by Rananim; 19th Jun 2009 at 00:49.
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Old 19th Jun 2009, 00:44
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NO COMMERCIAL AIRCRAFT SHOULD GO WITHIN 100nm LATERALLY of CB - ICTZ (Tropical Cumulo-Nimbus clouds) activity.....for any reason...FULL STOP. NEVER, EVER, don't even think about it.... or trying to overfly it. That is from MANY years experience and many grey hairs of wisdom!!

I guess you never fly through Texas with thunderstorms as big then. You would have to deviate over Oklahoma with those parameters.
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Old 19th Jun 2009, 01:13
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and for the ISIS-less Pilots......

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Old 19th Jun 2009, 01:27
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Good post there, these are the questions many others would like to see answered too, I suspect.
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Old 19th Jun 2009, 02:33
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The Air Caraibe report shows that the NAV ADR Disagree is a consequence of clogged/iced Pitot tubes and static ports and slightly different patterns of errors on each ADM generating the disagreement, making air speed and maybe also barometric altitude erroneous/inconsistant (this may be a potential problem for the TCAS ?). The NAV ADR disagree did not require a manual intervention of the pilots on one of the ADIRUs to appear.
All the faulty instruments, the ADIRUs, the ISIS and the TCAS appear to be inputed by Pitots, static ports or barometric pressure sensors. What if these Pitots and the airframe (static ports) were rime iced crossing a cumulonimbus ? If in the mist of a tropical cell, subjected to turbulences, severe icing conditions, a gradual deprivation of all air references (air speed), followed by a cascade of faulted nav instruments, multiple alarms in the cockpit, unreliable/unconsistant indicators, loss of flight assistances/protections, maybe a stall due to erroneous air speed which surprised everyone on board ? (pilots trying to understand/cope with the multiple failures, air crew). A stall followed by a dive, resulting in an overspeed during which the vertical aileron (and the spoilers ?) may well have been ripped off (not protected anymore against excessive manoeuvers in alternate law) before a critical airframe break up.
Hope these black boxes will be recovered soon.
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Old 19th Jun 2009, 02:48
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inertial reference

All the faulty instruments, the ADIRUs, the ISIS and the TCAS appear to be inputed by Pitots, static ports or barometric pressure sensors.
The ISIS and IR2 faults were related to inertial reference faults/disagreements. I can't see how airspeed and barometric data would per se generate them.

If they were later caused by a "shaking to hell" a/c it's another story...
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