For an air crash in which the ‘black boxes’ or any trace of the 228 victims may never be recovered, much has been learned about what happened to AF447 the Air France A330-200 jet that crashed in the mid-Atlantic early on 1 June.
This is because of a series of automated status messages relayed via satellite from the flight to the airline’s operational base in Paris.
And it is the reason why Qantas and all other A330 operators received an old fashioned telex message overnight recommending strict adherence to Airbus’s recommendations for flights where the pilots get unreliable airspeed indications from the instruments.
The advisory says the recommended speeds and the attitude of the jet need to be constantly maintained in these situations.
The ACARS or Aircraft Communications Addressing & Reporting System messages sent from AF447 to Paris provide almost real time monitoring of aircraft performance for maintenance purposes.
This screen grab from france2 TV last night shows a discussion of part of the ACARS message log from AF447
Each line logs an ACARS message which itself is a string of code in letters and numbers not shown here. The messages do not necessarily arrive at the airline base in real time but are often stored for transmission in a package at regular intervals especially if a ground receiving station will come within range in a reasonable time. The last message of any type sent from AF447 is believed to be at the top of this list, and contained an advisory of vertical cabin speed, thought by the investigators to have been generated by depressurisation that occurred just before or after the aircraft broke up.
That and similar systems are expected to evolve in the near future to something able to replace voice and flight data recorders by continually archiving that information at airllne operations bases.
But not yet, because the bandwidth, necessary satellites and other technical requirements aren’t quite ready and perhaps pilot associations aren’t either.
ACARS messages showed that AF447 flew at the wrong speed through severe turbulence until the jet broke apart, and then fell into the sea, leaving widely dispersed wreckage trails.
They show that as the flight began traversing the turbulent intertropical convergence zone, a belt of severe storms that extends from South America to Africa, the flight control mode used in normal Airbus operations was disconnected.
It has not been determined if the pilots made the disconnection, as would often be the case when manoeuvring between storm cells or if the disconnection was an automatic response to a failure in some of the flight control systems.
This change, from normal law or alternate law, as Airbus calls the main flight control modes, is something all A330 pilots are trained in managing. It is itself normal.
But then the dragons spring into view in the ACARS messages. A series of electrical faults begin to overwhelm the jet. They crucially include the ADIRU units which inform other systems that integrate data or move the control surfaces on the wings and tail as to how fast the jet is moving, how fast the air itself is moving up or down in turbulence, whether the jet is drifting, where it is pointed, and how level or inclined the nose of the jet is.
There are indications of ice forming over pitots that directly measure air flows.
Ice is not supposed to form at 35,000 feet. It is too cold there for water to exist, which means ice particles can’t stick to the surfaces. But it seems icing did occur.
AF447 was, suddenly, in all sorts of trouble, and the pilots, who never tried to use the radio in this final period, were getting inconsistent airspeed measurements according to the Airbus advisory.
It is not clear if this resulted in the jet flying too slowly, and falling prey to a high altitude stall, or too fast, and having critical control surfaces on the wing or tail broken by the severe updrafts and downdrafts it was encountering, which could rapidly lead to overstressing of the airframe and rupture.
(Nor is it known if a ground collision between this jet and another Air France plane at Paris in 2006 may have left an undetected weakness in one side of the wing.)
The very last message sent via ACARS is a vertical cabin speed alert, which was triggered by a cabin depressurisation that either happened immediately before or after the main body of the jet broke apart.
Search update: Despite false identification of debris and a fuel slick from shipping as having come from AF447 the search effort remains focused on an area close to the last known position of the jet before it ceased transmitting ACARS messages. Most of the wreckage is now assumed to have sunk to the sea bed. Specialised submersible equipment which may have the best chance of detecting signals from the flight data and voice recorders and retrieving them will not reach the area until next Friday.
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According to ATC, they said they were talking with the pilot and then suddenly AF447 vanished from the radar. A terrorist could have hidden a time bomb into a suitcase. Like Pan Am 103.
Since the only global satellite network available these days is Iridium, I will assume that the ACARS satellite communication was indeed over the Iridium network.
Assuming this is the case, what happened to the location data that is associated with all incoming MO-SBD packets? Sure, its an ellipsoid that is 10km squared, but it seems like Air France would have had a very good idea (with over 10 data points) where this jet was. Was this data element forgotten about?!
In fact GPS coordinates were included in many of the ACARS messages, although this wasn’t learned by the media for several days. This makes it clear Air France knew exactly where the jet was at key moments as it entered the tropical convergence zone, and could see, as it would have expected, that the crew were trying to navigate around the storm cells as shown by deviations from the nominal flight path. The onset of a stream of unprecedented failure messages and then the cabin vertical speed alert at the end of them left the airline in no doubt that AF447 had crashed. The only explanation I can think for declaration of such a large search area on the first day was uncertainty as to how far and in what direction the jet or parts of it might have travelled after that last message, and the dispersal effects of currents and wind. By the second day we see a much tighter search area declared, although given the false leads caused by flotsam and jetsam from shipping it also means there may not be much surface wreckage, and will make locating the black box flight recorders even more urgent. My hunch is that Air France knows far more about this accident than it has until now seen fit to share with the public.
Air France and the French Government will do all in its power to protect the Airbus name. I reckon their early statements about not locating the black box recorders are part of that strategy. That makes it easy put it all down to pilot error – flying into massive storm cells which stressed the jet beyond its design limits. There will still be questions however about aircraft system failures – multiple computers, sensors, probes, fly-by-wire technologies, composite materials, etc etc. I read a post by one older jet pilot who has flown through violent columns of cloud at the equator. He stated quite plainly that had this aircraft been one of the earlier Boeings or Douglas jets it would have survived such a flight into storm cells as he had. Moreover, the absolute reliance on automation in Airbus aircraft not only can increase pilot workloads but amplify the risk of loss of control when all of these automated systems fail or at least briefly malfunction (as with the recent Qantas Airbus off the WA coast). Conflicting and bizarre instrument readings confuse pilots who can then lose complete control (eg, manually fly the plane at inappropriate high or low speeds). I was amazed to read that the Airbus side-sticks (in lieu of traditional control columns) are independent of each other so a movement from one pilot can be cancelled or doubled by the opposite or same movement by the other pilot. That is scary. Fingers crossed they locate the records and reveal the truth.
The air france plane that “crashed”, first by ligthning at 40,000
feet???Anyway, planes get hit by lightning all the time!
http://www.etravelblackboard.com/showarticle.asp?id=91390 In an area that
has no radar coverage ie nobody can see whats done to it, and now they say
they’ll never find a black box that emits a beacon hmmmmmmmmmmm
Looks like someone shot it down, probably someone was on the plane who
needed to disapear (a drug lord of the other side which is being supported?)
With 90 km
http://au.news.yahoo.com/a/-/mp/5626926/new-debris-found-from-air-france-jet/
of wreckage and instant down (nobody text messaged anything, pilot didn’t
say anything, just emergency messages from plane) it exploded for sure.
Could have been a military accident? Like the USA shot the Iranian one or
Russia shot the Ukraine one, somebody could have accidently fired at it from
a nuclear submarine, I mean they are so stupid they crash into each other!
http://www.thesun.co.uk/sol/homepage/news/article2240543.ece
Anyway, I’d first be looking very very closely who was on that plane!
In the early days of Ansett’s first ‘all electric’ jets, I wouldn’t fly on them having been put off by my RAAF pilot colleagues that fly by wire was inherently dangerous. I know that the technology has improved greatly and that most civilain planes have some degree of computerised control, but I still feel that the primary flight controls should have an electro-mechanical over-ride function rather than just being computer controlled. The incident in WA with the QF A330 highlighted the huge cockpit workload required when something goes awry in fly by wire aircraft. I have never forgotten the old adage constantly briefed by my fighter jock colleagues when I was an air defence tactical controller – fly the plane first.
Alex
The ‘most electrical’ of jets of all so far, the 787 may be only days away from first flight now and I have to say, I’ve been looking forward to flying on this with enthusiasm and frustration given the delays. But let’s hope that adage–fly the plane first–is front of mind for all the pilots that fly this incredible jet. That message, fly the plane first, is one that my trusted sources when it comes to all types have emphasised down the years. And one of them, a privater pilot these days, never goes into the air without a little bag of back up aids for the day, or night, when everything in front of him goes blank, or tells him there is about 18 minutes of backup battery power on hand.
Given that 70% of the Earth is covered in water, wouldn’t you think they would make black-boxes that didn’t sink like a stone? It’s almost as if they don’t want the black-boxes retrieved.
There’s a tradeoff between them being able to float, and being able to withstand a high speed impact with terrain. 70% of the Earth may be covered in water, but I’m sure that aircraft flights are concentrated mostly in the other 30%.
One should have thought that all comercial jets would have heated pitot tubes and they are unlikely to freeze up at 35000 feet. It is rediculous if Airbus did not have them.