Well if we put this into context, AirFrance the AIRLINE itself has a message reported of a Short circuit via ACARS from the plane Itself, In Systems (Electronics) Its an abnormal low-resistance connection between two nodes of an electrical circuit that are meant to be at different voltages. This results in an excessive overcurrent limited only by the Thevenin equivalent resistance of the rest of the network and potentially causes circuit damage, overheating, fire or explosion. Now if I read further on in my book, It says Common usage of the term implies a condition arising from failure of electrical insulation, from natural causes (lightning, wind, and so forth)


So the likelyhood could be a Lightning strike, in a storm (Possible, not defineable) and lightning strikes at, this is what can happen; YouTube - An electric pole on fire

What passengers describe as "strange" is often just normal, moderate turbulence or aircraft movement. I would pay attention if the flight crew were making the above statement. Not pax.

AVOD/IFE systems often have problems. It usually doesn't indicate anything sinister.

If you read back over the last 26 or thereabouts pages of postings, you will see a number of intelligent speculative posts (and a large number of truly idiotic ones) about what might have happened. Nobody, however, can explain what actually did happen until all the facts are in, and even then maybe not with 100% certainty. We just have to wait.

At the moment, I personally, and hopefully everyone else here, can tell you that, with the current information that has been provided to the public, no member of the public can truly explain to you what has would have happened with the a/c. All that members of the public are able to do is speculate on what has happened, and a large amount of this speculation could very easily, and I dare say with the current information we have likely will, be proven wrong once the official investigations are finished and far more information is revealed. I would also strongly caution you as a member of media, against publishing anything that has not been supported by very credible sources. This is because once something comes from the media, most people will believe it is fact, and that could include people personally affected by this. The effects of informing people based on information that is not independently verified and checked against many sources unless coming from a highly credible one (the government being an example in some but certainly not all countries) can be far further reaching and worse than expected.

What does trepidou'e mean?

If we could do this, anxious relatives wouldn't have to wait months, if not years to find out how their loved ones died.

I'm sure that as a eager journalist you want to have all the answers yesterday. Sadly, no-one knows yet what happened to flight 447, there have been some educated guesses already here, some downright stupid ones too. I'm not going to add to the speculation on this tragic accident, I have attended the aftermath of aircraft accidents and I can tell you that the images will be with me until the day I die. Let's hope the authorities find out quickly what happened.

On another note, surely in this day & age we should not be relying on seriously out dated HF in some of the most remote parts of the world.
Or at the very least get better equipment-perhaps like the HF in Austrailia since that always has been very clear & easily contactable.
Again, the penny pinchers may be indirectly one of the links in a crash but they as usual will never be held to account.
So how much is safety really worth?

Not necessarily. A "short" is when, for some reason, you have an abnormally low resistance in a circuit which results in an extremely high current flow almost instantly. Now, a common cause of that is the failure of electrical insulation in a circuit and the increase in current is so much it will cause excess heat which could cause the insulation on adjacent cabling to fail, leading to an overvoltage in a lower voltage circuit as you describe as bare cables decide to touch each other.

The cause of the original degradation could be many, of which an overvoltage from a lightning strike is one, but not the only, cause.

Let's just wait on the reports, shall we.

With regards to ELTs on Airbus aircraft. There would have been likely three ELTs on the aircraft. One is fixed, its located in the rear ceiling area of the cabin with an external antenna, its the small antenna in front of the fin. Its controls are located in the overhead panel in the flightdeck. As the aircraft is likely to of broke up the chances are the ELT and antenna still being in serviceable state are very small.

There are also two portable ELTs located in the cabin but these would have to be activated by anyone that could have got to them.

Some information about the ELTs that may have been to this MSN are found here: ELTA : Elt, power supply, satellite transmission, physico-chemical analysis

As for the ELBs on the DFDR and CVR these activate on contact with water. If you want some specs here's a website for the manufacurer of one type of ELB its: Dukane Seacom Aviation Products

I have seen this posted several times, but have not seen a reply to it. Would someone explain / comment on ADIRU, ISIS, PRIM 1 and SEC 1 faults.

Elt/elba
 

There are different variants of ELT's, broadcasting on at least three different frequencies (121.5, 243 and 406 Mhz), the 406 MHz now being fashionable since it is traceable by satellites and can modulate a registered ID and an optional GPS calculated position onto the carrier frequency.

However, there is a big difference regarding crash sustainability to blackboxes like CVR and FDR. The latter do not have to work after a crash, it's good enough if they keep recorded information.

An ELT however must work after a crash only. This means that it must be powered and wired to an antenna which in itself must not be obstructed by large metallic structures (faraday cage) or what's even worse - water.

Even the technically less burdened will understand that it is not so easy to construct and place an ELT that will be working after its holding structure crashed into the water (or into a rock) at a few hundred knots. An ELT is therefore totally useless for the purpose of tracking an aircraft that slammed into the sea. Black Box beacons that will work submerged are transmitting their pings in a way not detectable by satellites or flying aircraft.

However, it is possible and systems are commercially available to track an object (persons, cars, ships, containers, etc.) via satellite (and GPS position) as long as it it travelling. Then, in an emergency, the end of a track would indicate the position of the stricken object.

Mephisopheles: Are you of the opinion that better communications equipment could have prevented this accident?

ITCZ without an operable radar? It has happened...
 

IIRC, back around the 1996 time frame, an Air France 744 was scheduled to fly the Jo'burg-CDG route. Upon accepting the aircraft, the flight crew noted that the wx radar was inop. After much discussion, the decision was reached to launch, but with a massive wx deviation around the ITCZ. Approaching the line of wx over central Africa, intense lightning was observed. Crew even called up a local control tower which was reporting heavy rain and lightning. Despite large wx deviations, crew ended up flying through a CB. After extreme turbulence and in flight upset, aircraft was diverted to Nice. Structural damage as well as one fatality were the results.

As detailed in book "Catastrophes Aeriens".

Two earlier posts provide some data that I haven't yet seen put together. The timining is interesting.

First, this from The Aviation Herald:

And then this from a weather analysis:

If these are correct, it puts the ACARS messages occurring during the most severe convective system.

Failure Mode Analysis
 

During design and certification it is incumbent upon the manufacturers and agencies to consider an "infinite" number of failure modes and satisfy themselves that systems and software will react to failure modes in a manner that does not compromise the safety or integrity of the aircraft.

Human fallibility will surely miss something along the way, as any software designer will attest. The design response to this is to provide redundancy.

The few data that seems to be emerging here does suggest that here could be a situation where the system responses may not have been appropriate. It is a moot point as to whether human control responses may have been more suitable.

For this reason it is critically important to recover as much evidence as possible.

At the million volt level of lightning, insulators can become conductors.

Air, for instance, is an superb insulator, but put a few tens of million volts across it and it will conduct.

The heating effect is caused by multiplying Volts by Amps to get Watts.

The behaviour of lightning when it strikes is sometimes bizarre.

Which is why all sorts of equipment ( e.g aircraft) are tested in a lightning test chamber.

The ADIRUs(Air Data Inertial Reference Unit) provide information such as Altitude, Airspeed and other air data information as well as inertial position which is an independant navigation position for the aircraft, search for inertial navigation on the net and you'll get an idea about what its all about. There are three ADIRUs on this type of aircraft.

The ISIS(Integrated Standby Instrument System) is electronic version of the back up instruments. It contains all the required sensing elements in a single unit to provide similar information to the ADIRUs

Prim 1 is one of the primary flight control computers of which there are three.
Sec 1 is one of the secondary flight control computers of which there are two. These are brains behind the flight control system. There are three laws for the FBW system and these are Normal Law, Alternate Law and Direct Law.

Besides that, inside an airplane is a perfect Faraday Cage which is also immune to external interferences.

Not quite correct. A Faraday cage depends on being effectively grounded, which an aircraft in flight is not.

Cheers,
Dave

Facts !
 

[Quote Aviation Herald]
New information provided by sources within Air France suggests, that the ACARS messages of system failures started to arrive at 02:10Z indicating, that the autopilot had disengaged and the fly by wire system had changed to alternate law. Between 02:11Z and 02:13Z a flurry of messages regarding ADIRU and ISIS faults arrived, at 02:13Z PRIM 1 and SEC 1 faults were indicated, at 02:14Z the last message received was an advisory regarding cabin vertical speed.
.../...
The sequence of messages reportedly received via ACARS raises memories of the Accident: Qantas A333 near Learmonth on Oct 7th 2008, sudden inflight upset injures 74 people on board and Incident: Qantas A333 near Perth on Dec 27th 2008, navigation system problem, and turns attention towards the emergency airworthiness directive released by both FAA and EASA, see also EASA issues updated emergency directive regarding Airbus A330 and A340 ADIRU issues.
[End of quote]

Seems to me the most accurate and troubling facts... (But i'm not a pro)

BBC News


Shallow water, or light turbine?



Folk should get some idea of the scale of potential power when talking about lightning. The worst scenario could see an aircraft vaporized. The total energy in a mature cell is up there with an atomic bomb. It's just that the the discharge is seldom focused in line with an airborn hull.

Faraday cages, and fiber-optic's immunity, is nothing but wishful thinking.

I know from personal experience, that a 'bolt' can enter an aircraft. The light intensity, once the sheath has been irradiated away, would saturate then destroy the fiber data-lines.

A discharge goes much where it wants. My biggest went in what became a 4" hole in the top of the wing, round the rubber fuel bags, and out a similar hole - in line with the top hole. I'm under no illusion that if the 'bolt' had been more vigorous, we'd have lost the wing in moments.

I found this very interesting and factual analysis of the weather condition prevailing near the INTOL and TASIL location at the time AF447 would have been flying in the area, I though some would find it interesting. I assume that the author of this analysis is okay to share it on a forum since he made it available on the internet.

Air France 447 - AFR447 - A detailed meteorological analysis - Satellite and weather data

If the link isn't working, try a bit later, it is because the server is too busy, or down...

Shallow water or light turbine
 

The Brazilian AF press release makes a few points quite clear...
1,) They are not identifying the objects as belonging to AF447...
2.) It wasn't a turbine that was seen floating, but rather a drum-like object....

Cheers
Tail Chase

Loose_rivets;
Yes, concur, but perhaps you misperceive the intent of the metaphor of a "faraday cage" as used in this discussion. It is useful in conveying an understanding as to why 99.9% of aircraft struck by lightning are not affected. That's all that was intended I think - in lightning strikes, the aircraft is simply part of the path "on the way to electrical ground". That lightning can do the damage described may be true in terms of the energy levels contemplated but the hull losses simply aren't there.

Of far greater concern here, I think you'd agree, is the power of convective columns within the thunderstorm cell(s) and the possibility of low to poor radar returns from same. Like most who do/did this work, I've seen it once or twice and been surprised at the violence of "what wasn't supposed to be there according to the radar"...

poison;
I think looking for cause(s) in the area of electrics/lightning/emergency elect configs etc is looking in the wrong areas; the reasons for saying this have been resident in this thread for about a dozen pages when BOAC first asked the question about the #3 VHF. The ACARS and #3 VHF systems are powered by the AC1 and DC1 buses respectively; the AOM does not list the bus(es) which power the SATCOM but most assuredly SATCOM would not be powered in any abnormal electrical configuration. Only the #1 VHF is powered by the DC ESS bus in either the Emergency Electrical Config or Flight on Batteries Only.

FYI, the ACARS switches automatically from #3VHF to SATCOM when out of VHF range.

If the ACARS sent "maintenance" messages etc then obviously it was working and therefore so was the #3 VHF, ergo the electrical system was working up to the point where, it is rumoured only, flight control/autopilot system maintenance messages, (see previous posts re the possible nature of the messages) were being sent. There is some mention here of "alternate law". Of course, it is impossible to know this at the moment until either the messages are verified and made available publicly, or the DFDR is found.

We don't know what the aircraft was doing or how it was performing after these messages were sent therefore, with present knowledge, even "intelligent" speculation is not possible from that point on and we will have to wait for other sources of facts. The DFDR/CVR will be of immense assistance. Though AF runs a FOQA program, I doubt that the QAR would have survived but we can hope.

4 PW's
You talk about "uninformed drivel" having said in the same post "I read somewhere that Air France 447's wing touched an A320 rudder". Apart from the fact that it was an A321 and happened in Paris this happened in 2006!!!!
I would call this uninformed or not bothering to check your inputs as so many others do or rather do not do.

Curiosity is a part of human nature. There is nothing wrong in speculation. Yes, some posts are repeated over and over again and get boring, but most of readers can filter through it. If you don't like this thread, simply don't read it instead of telling other people what to do. Every regular visitor here knows that crash-related threads contain lots of useless posts.

There is no harm done in speculating here. It does not endanger any hypothetical survivors, it does not hinder the search and recovery efforts, it does not hinder the investigation in any way. If crash-related info and speculation starts getting censored and restricted to the members of the profession, aviation will appear scarier to the general public because they are hiding something. Less people will fly, airlines will make more losses and lots of professional members of this forum will lose jobs. We passengers are paying your wages - and despite often having no clue, we like to be informed.

I do not contribute to PPRuNe (the reason is I have nothing to contribute, being an SLF), but I enjoy reading it, including speculations - I am sure many others do either.

lexxity

Lady Lexxington

Join Date: Jul 2004
Location: The Manor House
Age: 29
Posts: 964


Replying to post #487. Ditching has already been discussed and dismissed due to several factors amongst them the weather, the dark and the sea conditions found on the open sea as opposed to somewhere like the Hudson.

I've never sailed across the South Atlantic, only the North and the swells can be awesome, enough to toss a 70,000grt vessel, designed for those conditions, about so I don't see an airframe standing a chance. I do stand to be corrected though.
http://static.pprune.org/images/stat...ser_online.gif http://static.pprune.org/images/buttons/report.gif
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Guess we'll have to rewrite past history and advise people that actually survived ditching in open water in the past that they in fact didn't make it. I've flown with a pilot that survived one. He talked about his ditching being easy, as opposed to the other crew that he knew about that ditched in the North Pacific or Atlantic under adverse conditions and survived.

Swells in the ocean can be awesome. And sometimes the seas are amazingly smooth. U.S. television show covers fishing in the Bering Sea in winter. Sometimes it's amazingly calm, and other times there are terrible sea states. Airframes can, and have, survived water landings(ditchings) so they are survivable.

Unfortunately a debris field has been found so it appears, from the limited information available, that a ditching was not attempted.

Metal fatigue does happen, and has brought down planes in the past. So a bad repair or generally something missed could well be a contributor 3 years later, especially in extreme turbulence no? Not just metal fatigue but there was a case where a tail strike was badly repaired which lead to (correct me if I'm wrong) decompression and an in-flight breakup?

I am uninformed, but I wouldn't dismiss anything in this aircrafts history.

MU3001A

Unfortunately I doubt we will ever know but one thing is for sure that if the comms in that area were little more than non existent the crew would have had an additional source to refer to. As is the case things tend to go wrong when you a farthest away for anywhere & with little or no comms.

cockpitvisit

Good post indeed.


Metal, indeed has a very long memory.

As we all know, bend a piece of metal often enough and long enough and it will break. The trick is to discover where the metal intends to break.

They had degraded flight controls, no autopilot and no flight instruments.

Partial control
 

Is it true to say that on Alternate Law, the A/C can be manually controlled thru the stabilizer and the rudder?

SLF, non-journo question. If all the controls, autopilot etc., are knocked out, how long does it take for them to reboot under 'normal' conditions?

PJ2 -
I submit that if the radar in use today isn't capable of "seeing" this kind of convective activity, that you avoid these areas completely. Using the C-Band radar we had, I don't recall an active cell failing to show up on the scope.....providing the operator knew how to use it.

I find it very frustrating that with the availability of sat. internet access in the back, with the resultant access to excellent real-time wx data including radar, the SLF have better weather information than we do up front at times. How long will it take to incorporate a useful, current data stream to the cockpit. I guess only the bean counters know the answer to that one.

My understanding is that the "AP Disconnect/alternate law" message preceded the later string of system failures. If correct then the indication is some sort of "upset" or turbulence induced unusual attitude prior to other issues...or am I misreading the information available. Based on the early comments by AF it seems in line with the picture of an upset followed by various system failures indicating some type of catastrophic failure.

If a sudden unexpected extreme turbulence event caught the pilots by surprise and forced the plane into a position of unusual attitude severe enough to disconnect the AP would the switch to alternate law create problems in recovering the aircraft?

I didn't really want to comment on this, so I won't speculate on the reasons why AF447 crashed.
However, what worries me is that it seems some professionals are really dismissive of the potential of lighning damage on modern aircraft.

I've read through all of the posts and it seems strange that no one has mentioned positive lightning, which account for less than 5% of all strikes.
Positve strikes are at least 6, and often up to 10 times more powerful than standard strikes. Modern passenger aircraft are not built to withstand positive strikes as the technology is not available: the discovery of positive lightning is pretty recent.
Positive lighning occurs when a positively charged leader forms at the cloud, and a negatively charged streamer issues from the ground.

Positive strikes can occur far away from CB (of course, originating in CB), due to their immense energy which can reach up to 300KA and would therefore far exceed the 20nm cordon recommended for CB avoidance for shear/turblence/strikes etc. Compare this to standard negative strikes of up to 30 KA and it is easy to see why these strikes are very dangerous.
For pilots who dismiss lightning strikes as almost harmless, well, you'd be right. Up to 95% of the time. It is unlikely to happen, but it can and has bought down aircraft, Pan Am 214 is an example.

Regarding the flight control law questions:

No entirely true. In normal law the flight contol computers provide various protections which keep the aircraft within operating and structural limitation. The first level of degradation is alternate law in which some of those protections are lost, but the aircraft still flies normally. The next level of degradation is direct law, at this point, the aircraft does not have any protections but still flies like any normal aircraft with full control authority. The last level of degradation is manual back-up where the pilot has only rudder and manual pitch trim to control the aircraft while computers are reset. Manual reversion is not designed to be used to control the aircraft in other than straight and level flight as a temporary siutation. I have landed the 332 in the sim in manual reversion and it can be done, but the chances of being in that situation are exceedingly slim.

Regarding the PRIM and SEC question, the loss of PRIM 1 and SEC 1 would probably leave the aircraft in alternate law which is not an emergency situation in itself but would be another distraction if more failures were occuring. With any 1 of the 3 prims, and 1 of the 2 secs the aircraft is in normal law. The degredation logic is somewhat complex, but with any 1 of either type of the flight computers you could at least have direct law.

The flight computers are all independently designed and built by different companies to ensure that a design or manufacturing flaws could not affect all of the computers.

Hi Coyote44, Alternate Law is no big issue - some of the magic protections will be lost depending on the failure (bank angle, g, overspeed, alpha etc). The aircraft effectively becomes a traditional airplane. Then comes Direct Law, which is still fully functional control of flight, before it eventually degrades to rudder, trim and thrust control only.

A330 Flight Controls
 

PRIM 1 and SEC 1 refer to the FLIGHT CONTROL PRIMARY COMPUTER (FCPC)

ISIS Integrated Standby Instrument System

ADIRU Air Data Inertial Reference Unit

I suggest an excellent article on A330/340 Flight Controls

http://www.davi.ws/avionics/TheAvion...ook_Cap_12.pdf

Snaproll & Sika
 

Thanks for the input. I was merely trying to enquire if their systems could've degraded to backup mode, which in severe turbulance would've been impossible to control, IMHO.

I am a SLF and I have been bashed many times for my comments but there are two posts on this thread that I must criticize.

Metal fatigue occurs over the time, a strike (i.e. with another object) will not have any significant impact on the metal fatigue failure. CI611 went down 20 over years after being poorly repaired...

Faraday cage...it is an ideal conductor therefore does not need to be grounded (actually is otherwise)...one of its function is to protect from lightening strikes... Wikipedia has a quite good description of it...

edit: deSitter gave a accurate description of a Faraday cage

FSLF

Coyote, the short answer is yes. If all the computers were lost and they were in manual reversion and they were in severe turbulence, then the plane would be almost impossible to control.