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AF 447 Search to resume

Old 25th Feb 2010, 20:20
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Originally Posted by vovachan
I am sure this has been discussed, but why can't aircraft on routes over the ocean transmit their FDR data to one another for storage? One of the planes down, the other makes it to land and the data gets downloaded. VHF traffic costs nothing, and so does storage.
I know, that's 320 previous posts to read.
So let me try to answer that very briefly.
NO aircraft at present has ANY equipment on board to transmit a continuous stream of FDR data.
NO aircraft at present has ANY equipment on board to receive and store a continuous stream of FDR data from possibly a dozen aircraft in the vicinity,
VHF or otherwise.
I suppose you can draw the rest of the conclusions?

CJ
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Old 25th Feb 2010, 20:38
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vovachan

CJ has pointed out the the infrastructure doesn't exist. If it did, it wouldn't work in the following situation, and similarly elsewhere:-

http://www.pprune.org/rumours-news/3...ml#post5428608

mm43
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Old 25th Feb 2010, 23:57
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JD-EE
Does anybody have any idea how a shredded AF447 might have sunk?
There is no short answer to this problem. It depends on a number of factors, e.g.

(a).. density of the liquid (1025 kg/m3), or SG 1.025
(b).. density of the object(s) - aluminium, composites, cushions etc..
(c).. permeability, i.e. the rate at which the liquid can displace air in an object
(d).. shape of the object
(e).. surface friction / viscous drag of the object
(f).. inherent buoyancy retained by, e.g. tanks
(g).. crush pressure of items, e.g. cushions, tanks etc..

Incorporate these multitude of items into a homogeneous mass associated with a broken hull, and essentially its a bit of a guess.

In other words many factors will come into play, and not least is the pressure of 397 Atmospheres at a depth of 4,000 meters. Though the important thing to remember is that as the pressure increases, the factor associated with surface friction or viscous drag increases in proportion. That means there is no runaway charge to the bottom.

mm43

Last edited by mm43; 28th Feb 2010 at 16:33.
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Old 26th Feb 2010, 05:00
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AF 447 Search to resume

The Last Four Minutes Of Air France Flight 447


freeinternetpress.com

The crash of Air France flight 447 from Rio to Paris last year is one of the most mysterious accidents in the history of aviation. After months of investigation, a clear picture has emerged of what went wrong. The reconstruction of the horrific final four minutes reveal continuing safety problems in civil aviation.

One tiny technical failure heralded the impending disaster. But the measurement error was so inconspicuous that the pilots in the cockpit of the Airbus A330 probably hardly noticed it.

Air France flight 447 had been in the air for three hours and 40 minutes since taking off from Rio de Janeiro on the evening of May 31, 2009. Strong turbulence had been shaking the plane for half an hour, and all but the hardiest frequent flyers were awake.

Suddenly the gauge indicating the external temperature rose by several degrees, even though the plane was flying at an altitude of 11 kilometers (36,000 feet) and it hadn't got any warmer outside. The false reading was caused by thick ice crystals forming on the sensor on the outside of the plane. These crystals had the effect of insulating the detector. It now appears that this is when things started going disastrously wrong.


Flying through thunderclouds over the Atlantic, more and more ice was hurled at the aircraft. In the process, it knocked out other, far more important, sensors: the pencil-shaped airspeed gauges known as pitot tubes.

One alarm after another lit up the cockpit monitors. One after another, the autopilot, the automatic engine control system, and the flight computers shut themselves off. "It was like the plane was having a stroke," says Gerard Arnoux, the head of the French pilots union SPAF.

The final minutes of flight AF 447 had begun. Four minutes after the airspeed indicator failed, the plane plunged into the ocean, killing all 228 people on board.

Few airline crashes in recent years have subsequently unnerved passengers to quite the same extent. "How was it possible that an Airbus from such an apparently safe airline could simply disappear?" they wondered.

Passengers on the Rio-Paris route are still uneasy as they board their plane. After the accident, the flight number was changed to AF 445. Many frequent flyers have since opted for daytime flights across the Atlantic because pilots can recognize storm fronts more easily during the day.

Another large-scale search for the stricken plane's "black box" flight recorders is due to begin in the coming weeks. Once again some 2,000 square kilometers (800 square miles) of mountainous ocean floor will be swept, some of it by a submarine from from the northern German city of Kiel. "We shouldn't speculate about the causes of the accident until the search has been completed," says Jean-Paul Troadec, the director of the French air crash investigation agency BEA.

Other experts are less guarded in their comments. "We know pretty well why the accident happened," says union boss Arnoux.

'An Accident Like This Could Happen Again'

Over the course of several months of investigation, experts have gathered evidence that allows them to reconstruct with relative accuracy what happened on board during those last four minutes. It has also brought to light a safety flaw that affects all jet airplanes currently in service. "An accident like this could happen again at any time," Arnoux predicts.

Experts reconstructed dozens of incidents involving Airbus planes to try to piece together the puzzle of this particular disaster. Plane wreckage and body parts give crucial clues as to what brought the plane down. Crash investigators also conducted detailed analyzes of the 24 automatic fault messages that the aircraft sent to Air France headquarters by satellite in the run-up to the accident. One particular message - the very last one transmitted before impact - could solve the mystery surrounding flight AF 447.

A half moon lit up the Atlantic Ocean on the night of May 31, offering reasonably favorable conditions for a flight through the dangerous inter-tropical convergence zone. That's where violent thunderstorms rage and columns of thick clouds bar the way like an aerial obstacle course. In addition to the on-board radar, the moon helps pilots identify dangerous cloud formations and take appropriate measures.

On the night of the tragedy, other planes diverted their flight paths and took a detour around the danger zone.

Why then did flight AF 447 head straight into the deadly storm system? Is it possible that the tragedy began even before the plane took off?

Galeao Airport, Rio de Janeiro, 6pm local time: Preparation for takeoff

Captain Marc Dubois, 58, goes through the flight plan of AF 447: He enters a starting weight of 232,757 tons into the on-board computer, 243 kilograms less than the maximum permissible weight for the A330. As well as the passengers' luggage, the ground crews load 10 tons of freight into the cargo bay. Dubois has more than 70 tons of kerosene pumped into the fuel tanks. That sounds a lot more than it actually is, because the plane consumes up to 100 kilograms of kerosene every minute. The fuel reserves don't give much leeway.

It's only by means of a trick that the captain can reach Paris with more than the legal minimum reserves of kerosene that must be in the plane's tanks upon arrival in the French capital. A loophole allows him to enter Bordeaux - which lies several hundred kilometers closer than Paris - as the fictitious destination for his fuel calculations.

"Major deviation would therefore no longer have been possible anymore," says Gerhard Huttig, an Airbus pilot and professor at the Berlin Technical University's Aerospace Institute. If worse came to worst, the pilot would have to stop and refuel in Bordeaux, or maybe even in Lisbon. "But pilots are very reluctant to do something like that," Huttig adds. After all, it makes the flight more expensive, causes delays and is frowned upon by airline bosses.

After takeoff, Dubois quickly takes the plane up to a cruising altitude of 35,000 feet (10.6 kilometers), an altitude known as "flight level 350." According to his kerosene calculations, he has to climb far further, to above 11 kilometers, where the thin air reduces his fuel consumption.

It's not known whether he actually reached this altitude. Three hours after leaving Rio, Captain Dubois contacted Brazilian air traffic control for the last time. "Flight level 350," he reported. It was to be his last communication with the outside world.


Minute One: The Sensors Fail

It's hard to imagine a more precarious situation, even for pilots with nerves of steel: Flying through a violent thunderstorm that shakes the entire plane as the master warning lamp starts blinking on the instrument panel in front of you. An earsplitting alarm rings out, and a whole series of error messages suddenly flash up on the flight motor.

The crew immediately recognized that the three airspeed indicators all gave different readings. "A situation like that goes well a hundred times and badly once," says Arnoux, who flies an Airbus A320 himself.


The responsible pilot now had very little time to choose the correct flight angle and the correct engine thrust. This is the only way he could be certain to keep flying on a stable course and maintain steady airflow across the wings if he didn't know the plane's actual speed. The co-pilot must therefore look up the two safe values in a table in the relevant handbook - at least that's the theory.

"In practice, the plane is shaken about so badly that you have difficulty finding the right page in the handbook, let alone being able to decipher what it says," says Arnoux. "In situations like that, mistakes are impossible to rule out."

Danger of Icing Up

Aerospace experts have long known how dangerous it can be if the airspeed indicators fail because the pitot tubes ice up. In 1998, for example, a Lufthansa Airbus circling over Frankfurt Airport lost its airspeed indicator, and a potential tragedy was only averted when the ice melted as the plane descended. At the time, German air accident investigators at the German Federal Bureau of Aircraft Accident Investigation (BFU) in Braunschweig demanded that the specifications of the pitot tubes be changed to enable "unrestricted flight in severely icy conditions."

As early as 2005, the French aerospace company Thales, which manufactures the pitot tubes used on flight AF 447, set up a project group called Adeline to search for new technical solutions to the problem. According to a Thales document, loss of the airspeed indicators "could cause aircraft crashes, especially in cases in which the sensors ice up."

Aircraft manufacturer Airbus was well aware of the shortcomings of the Thales pitot tubes. An internal list kept by the airline manufacturer shows there were nine incidents involving them between May and October 2008 alone.

More than two months before the Air France crash, the issue had been raised at a meeting between Airbus and the European Aviation Safety Agency. However, the EASA decided against banning the particularly error-prone pitot tubes made by Thales.

In fact, the problem with the airspeed indicators lies far deeper. To this day, the relevant licensing bodies still only test pitot tubes down to temperatures of minus 40 degrees Celsius (minus 40 degrees Fahrenheit) and an altitude of about 9,000 meters (30,000 feet). These completely antiquated specifications date back to 1947 - before the introduction of jet planes.

What's more, most of the incidents of recent years, including that involving the ill-fated flight AF 447, occurred at altitudes above 10,000 meters (33,000 feet).


Minute Two: Loss of Control

Did the pilots on flight AF 447 know about the airspeed indicator failures experienced by colleagues on nine other aircraft belonging to their own airline? Air France had indeed distributed a note about this to all its pilots, albeit as part of several hundred pages of information that pilots find in their inbox every week. One thing is certain: The pilots on flight AF 447 had never trained in a flight simulator for a high-altitude breakdown of the airspeed indicator.

The situation in the cockpit was made even more difficult by the fact that the flight computer of the A330 put itself into a kind of emergency program. The plane's digital brain usually supervises all activity by its pilots - at least, as long as its sensors provide reliable data. Without a speed reading, the computer more or -less throws in the towel, which doesn't make things easier for the pilots.


"The controls suddenly feel completely different to the pilot," says flight expert Huttig. The sheer complexity of the Airbus' systems makes it difficult to control in critical phases of the flight. It would be easier for pilots if they could simply switch the computer off in critical situations, as is possible on Boeing planes.

Pitot tubes sometimes also fail on Boeing aircraft. When Spiegel contacted the American Federal Aviation Administration, the body which oversees civilian flight in the U.S., the FAA confirmed that there had been eight such incidents on a Boeing 777, three on a 767, and one each on a 757 and a Jumbo. Boeing is currently conducting a study on the safety effects of "high-altitude pitot icing on all models in its product line," says FAA spokeswoman Alison Duquette. The FAA did not, however, identify "any safety issues arising" during these incidents.

Could it therefore be that the flight computer, which is hard to manage in emergencies, actually contributed to the loss of control by the Airbus pilots? Air-safety experts Huttig and Arnoux are demanding an immediate investigation into how the Airbus system reacts to a failure of its airspeed sensors.

Unexpected Reaction

In early March, the BFU in Germany is due to publish the findings of its investigation into the near-crash of a Lufthansa A320 two years ago at Fuhlsbüttel Airport in Hamburg, a report that will undoubtedly prove uncomfortable reading for Airbus. In that incident, an unexpected reaction by the flight computer caused the jet's left wing to scrape along the runway while landing. The BFU is due to issue 12 safety recommendations, some of which concern Airbus' computer programs.

So far, it's unclear who was controlling the Air France plane in its final minutes. Was it the experienced flight captain, Dubois, or one of his two first officers? Typically, a captain retreats to his cabin to rest a while after takeoff. Indeed, there's corroborative evidence to suggest that the captain was not sitting in the cockpit at the time of the crash: His body was recovered from the Atlantic, whereas those of his two copilots sank to the bottom of the ocean still attached to their seats. This would suggest that Dubois was not wearing a seatbelt.

In contrast to many other airlines, it is standard practice at Air France for the less experienced of the two copilots to take the captain's seat when the latter is not there. The experienced copilot remains in his seat on the right-hand side of the cockpit. Under normal circumstances, that is not a problem, but in emergencies it can increase the likelihood of a crash.

As a consequence, it was probably the plane's third pilot, Pierre-Cedric Bonin, a dashing amateur yachtsman, who steered the aircraft to its doom. Bonin's wife was also on board, while their two children were at home with their grandfather.


Minute Three: Freefall

Not long after the airspeed indicator failed, the plane went out of control and stalled. Presumably the airflow over the wings failed to provide lift. Arnoux, from the pilots' union, estimates that the plane fell toward the sea at about 42 meters per second (95 mph) - almost the same speed as a freefalling parachutist.

Arnoux's version of events is based in part on the timing of a transmitted error message about the equalization of pressure between the cabin and the outside of the plane, which usually happens at 2,000 meters (7,000 feet) above sea level. Had the airplane nosedived, this alarm would have been triggered earlier. "It takes almost exactly four minutes to freefall from cruising altitude to sea level," Arnoux says.


According to this scenario, the pilots would have been forced to watch helplessly as their plane lost its lift. That theory is supported by the fact that the airplane remained intact to the very end. Given all the turbulence, it is therefore possible that the passengers remained oblivious to what was happening. After all, the oxygen masks that have been recovered had not dropped down from the ceiling because of a loss of pressure. What's more, the stewardesses weren't sitting on their emergency seats, and the lifejackets remained untouched. "There is no evidence whatsoever that the passengers in the cabin had been prepared for an emergency landing," says BEA boss Jean-Paul Troadec.

Two seemingly insignificant lines from the warning reports transmitted by the aircraft show how desperately the pilots fought to keep control. They read "F/CTL PRIM 1 FAULT" and "F/CTL SEC 1 FAULT".

This somewhat cryptic shorthand suggest the pilots tried desperately to restart the flight computer. "It's like trying to turn your car engine off and then on again while driving along the motorway at night at 180 kilometers an hour (110 mph)," says Arnoux.

The attempt to resuscitate the on-board computer proved unsuccessful. For the last 600 meters (2,000 feet) before impact, the pilots' efforts would have been accompanied by the chilling calls of an automated male voice: "Terrain! Terrain! Pull up! Pull up!"


Minute Four: Impact

More than 200 tons of metal, plastic, kerosene and human bodies smashed into the sea. The sheer force of the impact is described in the forensic report, which lists in graphic detail how lungs were torn apart and bones were shredded end to end. Some of the passengers were sliced in half by their seatbelt.

Much of the debris that has been recovered is no larger than a square meter (10 square feet). The shear-lines run at a conspicuous angle. This shows that the plane did not plunge vertically into the sea, but rather hit the water like a flat hand, with the nose of the aircraft pointing upwards at a five-degree angle. Of particular interest is the large tailfin that was recovered from the ocean by the Brazilian navy. This was ripped from its anchoring and catapulted forwards. From this, it can be deduced that the A330 was brought to a halt with a force more than 36 times that of normal gravity: 36g.


Although Airbus continues to play down the significance of the pitot tubes in the crash of its A330, the company's engineers have since developed new technologies that will detect the breakdown of airspeed sensors even before takeoff. Airbus registered a patent for this technology in the U.S. on Dec. 3, 2009. In the words of the patent application, errors in speed measurements "can have catastrophic consequences."

For several years now, Airbus has offered its customers a special safety program - called "Buss" - at a cost of €300,000 per aircraft. If the airspeed indicator fails, this software shows pilots the angle at which they must point the plane.

Up to now, Air France has chosen not to invest in this optional extra for its fleet.

Intellpuke: You can read this article by Spiegel staff writer Gerald Traufetter in context here: Death in the Atlantic: The Last Four Minutes of Air France Flight 447 - SPIEGEL ONLINE - News - International
This article was translated from the German for Spiegel by Jan Liebelt.
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Old 26th Feb 2010, 06:53
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''Passengers were possibly oblivious to the problems''

I don't think so!

If the plane was falling vertically at 95mph with little forward speed they would have felt the g forces equvilent to falling through the air like a sky-diver or worse still attached to a roller-coaster plummeting vertically down a track almost 10,000 meters high. They may have even died from shock before impact. The forensic report would only be able to tell what injuries were sustained AFTER impact not whether for the 4 mins earlier people were going through hell.

The report seems to be really focused on scaring the living daylights out of people which is appalling given that the recorders still havent been found. I also dont like the way the report tries to say flying Boeing is safer than flying Airbus in an emergency situation
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Old 26th Feb 2010, 08:27
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Noelbaba's post - some further insights

The simple solution to the Thales pitot head conundrum is to have a two-stage heat selection. In normal operations selecting higher than the present amperage of pitot heating would cause an overheat failure of the heating coils (the reason why pitot heat is never turned on)
a. In general aviation aircraft until just before take-off or
b. In more complex aircraft turned on (and off after landing) by ground-air sensing
It’s because there is a need for cooling airflow to offset the pitot heating. (stops the pitot covers melting when ground power is applied, for one thing)

However in the case where an airliner cruises at high altitudes for long periods in Ac/As (alto-cumulus /AltoStratus), cloud types which are composed of supercooled ice crystals, then the formula no longer works. i.e. the rate of cooling exceeds the ability of the pitot heater to keep the pitot head warm enough to stop ice entering, congealing and slowly building up to ultimately block the pitot tube. You need a stepped heating arrangement, either automatic or pilot-selected (or preferably auto with a manual back-up)…. To “bump” the amps up to a higher rate of heating. This could be done via an altitude switch or via an OAT threshold (assuming that the OAT sensor is not going to suffer from a similar icing-induced error).

It is readily apparent that EASA and Airbus were aware of this phenomena (of the ingestion, over a period, of super-cooled icing particulates overpowering the pitot heater’s capability). However they never extrapolated this anomaly into an accident scenario. I don’t disagree with the scenario in the "Last 4 Minutes" article above, but I do think that there is a slightly more complex story behind the loss of control. That was much earlier spelt out in The Shadow’s posts at: Air France Flt 447 and The AF447, QF72 and 9M-MRG comparison

Or linked at this URL in this earlier AF447 thread: http://www.pprune.org/tech-log/37643...ml#post5202785

Extract (only):
Exceeding the Envelope but without any Indications of doing that ...
In enroute mode, with the captain in crew rest, the two copilots would have a low level of situational awareness (i.e. cruise ennui) and would probably not detect that the autothrust was increasing incrementally and insidiously to offset a "system-perceived" speed (and Mach) loss trend. The nett result is an A330 moving through the air ostensibly at its scheduled speed but, in actuality, a lot faster than it should be - maybe 25 to 30 knots fast and quickly approaching a borderline Mach for coffin corner (i.e. the upper operating envelope boundary-line). Available cues? A slightly lower nose-down attitude, a marginally lower Angle of Attack, but with the displayed speed and Mach tapes on both the pilots' screens (PFD's) staying steady, yet both Engines’ N1's spooled up a fraction - as the autothrust endeavours to maintain the scheduled speed. Overall gradual and unnoticeable. The autotrim would be very very slowly winding the trimmable horizontal stabilizer nose-down. It all happens so gradually because the ice is building slowly inside the pitot head's intake. But why even slowly? Isn't there a pitot heat operating to stop icing?

The pitot heat can generate (say) 1300x calories/minute of heating but the nett heat loss due to the "already frozen" nature of the steady, continuously impacting ice crystals in a layer of CirroStratus cloud (Cs) might be -1500x (or greater). Respect the uniqueness of flying in layered sheet cloud for lengthy periods. It's completely different to being "in and out" of convective cloud within which there may be relatively short duration encounters with moisture resulting in rapid accumulations of heavy ice (or momentary hail). The nett overpowering result at the pitot heads, over time, is a gradual accumulation of ice in each pitot head. It's all about exposure time. It's not due to a prior blockage, just due to the design and the thermal give-and-take - and that's why all three pitots' heating provisions can gradually become identically overpowered and blocked, all at the same non-alarming rate of ice-crystal feed. The stagnating pressure that normally generates the airspeed feed to each ADIRU will reduce linearly and generate a consequent progressive autothrust boosted increment to recover that speed (just as it would if there was to be a genuine speed loss due to the added drag of airframe ice). The process possibly takes 30 minutes or more. Because it happens so gradually, no-one notices the imbalance (thrust too high, nose slightly low, trimmed nose-down). The throttles (aka thrust levers) don't move in the Airbus (like they would in a Boeing). They have detented "settings". The ADIRS is geared to identify and reject systematic flaws - however it is easily duped by protracted and unique skewing environmental factors. But what could happen to precipitate the terminal upset into a loss of control ?

It would be the autopilot trying to contend with the data conflict and the sudden onset of Mach Crit and disconnecting due to the high aerodynamic out-of-trim loads it's holding. The earlier ACARS transmission recorded that development. Imagine a sudden autorotative roll and the nose dropping and the pilot wrongly assuming a stall/spin, using aileron and fwd stick and adding thrust. Recollect that he's just not seeing a high airspeed or Mach Number ..... so he could be forgiven for assuming a slow-speed stall and taking the wrong action. It's similar (but opposite) to the Buffalo crash of that Dash 8 recently. Suddenly that Dash8 aircraft stalled and the pilot instinctively took go-round action - which involves raising the nose (but if he'd recognized it as a stall, then of course he should have lowered it).
The reason for the AF447 autopilot disconnect is explained in depth in part two . Why wouldn't this have happened to the numerous earlier incident airplanes? Well there's different thicknesses of Cs cloud and different exposure times. As in most accidents, the adverse factors often "stack" to ultimately generate a catastrophe. According to this article the AF447 skipper got high early because he was tight for trip fuel and needed to make savings on his contingency reserve. That would've put him closer to the coffin corner boundary. The happy outcomes for the earlier incidents also tended to accommodate a false sense of security in all (un)concerned decision-makers and aircrews.
Etc etc
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Old 26th Feb 2010, 10:22
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Simple note - USC-28 and OM-55 of the late 70s for the DoD worked as a bent pipe repeater with a "T0" reference at the satellite slaved to its beacon. That allows TDMA and CDMA for multiple links. OLD OLD technology.

For the rest, for brevity here, you have a message here on the system.

And I note that you have generally good insights. I'm, hopefully, adding some ancient experience to the mix.

Addendum
I also note, existing systems (IRIDIUM and INMARSAT-M) are aimed at different markets so are not drop in solutions. However, their in-flight entertainment Internet links could be twisted into working nicely at lower volumes of data.

{^_-}
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Old 26th Feb 2010, 10:27
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Uncle Jay "You're assuming they were still attached to the wings on entry. Probably not true."

Quite the contrary. The wings would preclude straight down by providing slight flotation and a huge current catching sail.

{^_^}
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Old 26th Feb 2010, 10:49
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Originally Posted by noelbaba
Not sure where to even start on that lot, but I must say I am really pleased that between Spiegel and the Union, the flight recorders have been recovered and told them exactly what happened. That way we can put an end to all the hype, scaremongering and random speculation that is based on no evidence at all.

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Old 26th Feb 2010, 12:16
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"Framing" the Argument

Early on, the article revealed its own value:

...more and more ice was hurled at the aircraft...
GB
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Old 26th Feb 2010, 15:08
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Reclearance / redispatch

"Major deviation would therefore no longer have been possible anymore," says Gerhard Huttig, an Airbus pilot and professor at the Berlin Technical University's Aerospace Institute. If worse came to worst, the pilot would have to stop and refuel in Bordeaux, or maybe even in Lisbon."

Luckily 'expert' Huttig is not flying me around, as he has not noticed that the deviations made by the other flights that night were insignificant in fuel usage terms.
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Old 26th Feb 2010, 16:06
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The TAT icing first increasing TAT sounds like it started a series of events and failures that distracted the crew.

What no manual control of pitot/static heat on the 330?

Obviously, eventually yaw damp and pitch limiting devices gave full authority to rip the aircraft to shreds at an unknown airspeed.
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Old 26th Feb 2010, 16:58
  #333 (permalink)  
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Without judgment, I am sure the rheostat at the Pitot Drain can sense moisture at any temperature, and its concomitant and metered increases in applied heat would have solved this problem. What? there isn't such a system?

For me, if prose and comment make it past the mod, I'm interested, and snide comment or "judgment" from others is as a gnat on a Buffalo. This "article" seems at first blush to be written for non-engineers, possibly to include non-pilots. Of course it attracts dismissal from those who don't understand that. It is quite reasonable to assume the junior pilot was flying from LHS, it's been proposed before. It is also supported by the supposition relative to Captain's post crash discovery, and the condition of the "crew rest" capsule, in which he most likely would have been without body restraint.

Investigation involves supposition, that is a fact. It may germinate from a seemingly wild piece of evidence, or none at all. Therefore, to discount a line of reason without reason is as unhelpful as the wildest of proposals.

Yes, this article seems to defend the pilots. Yes, its genesis came from a pilot. Is that a connection to exclude? Of course not, just as ignoring the connection of the authority to the line and manufacturer must be considered.

Look at the recovered spoiler. Assess the condition of the VS/Rudder.
Think of the A/S at upset, and Altitude. Ponder the history of the Thales, the unavoidable comparison to Boeing, (avoiding the knee jerk cheerleading), and the ACARS.

It is proposed that the a/c hit intact, at terminal velocity through the air.

If overspeeding was in play, and a Stall occurred to potentiate the lower a/s, think especially of the Kinetic energy at .83 Mach+ that had to have dumped very quickly, and bearing that in mind continue to consider that the a/c impacted as 'concluded', intact.

Considering what is improbable comes with looking at the (few) pieces left after any accident. It isn't Faith or Politics that must drive the analysis, but an open mind. The most important thing is to mitigate the cause of this tragedy, not protect or condemn any party to it. Pathology, if taken seriously, is a lonely place. The real beneficiaries of the Truth are the humans who trust their lives to this very complicated and wonderful enterprise of Flight. If either Arnaux or Gourgeon end up looking like fools, or worse, no skin off me.
 
Old 26th Feb 2010, 17:42
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Early on, the article revealed its own value:

Quote:
...more and more ice was hurled at the aircraft...


Graybeard,
Don't let this mistranslation from the German colour your judgment of this article.
The original German, Immer mehr Eis wird in den Gewitterwolken über den Atlantik emporgeschleudert, is more properly translated as More and more ice is being blown [hurled, flung, catapulted] upward in the thunderclouds over the Atlantic . "Empor[up, upward]geschleudert" is an intransitive verb in this case and the writer is presumably referring to motion in a convective cell.

Rockhound
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Old 26th Feb 2010, 18:23
  #335 (permalink)  
bearfoil
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I had assumed "vertical development" from my terrible German. Again, patience is required, and some latitude in "judgment" rather then instant rebuke. Rockhound, thanks. I fear no further "conclusions" can be supported without more information, but setting (or resetting) the table of debate serves to polish the basis for further discussion, imo.

Possible. At impact, the VS is proposed to have been "flung" (unfortunate term, eh?) forward, across the top of a Fuselage at 5 degree pitch. The "across the top" follows from "En ligne de vol". Any deviation from the longitudinal axis of the Fuselage would impute a "skid", or "Yaw" relative to direction of "Flight". (Of course "Flight" can only be used advisedly, the BEA concludes accelerations and velocities that preclude this a/c from "flight"). The Vertical vector is longer and fatter than the Horizontal, again following BEA, "strong vertical acceleration" slight Horizontal.

As efficiently as the VS was designed, it wasn't meant to survive much vertical acceleration of any description, only side forces. So on the one hand, its strength to weight ratio defines the engineering consideration, and the architecture of the three joins. Sudden decelaration in a vertical manner suggests that the VS would be driven into its mounts, not "pulled away".

Sudden deceleration in the horizontal would challenge the strength of the hoops in a way they were not designed. However, both vertical and horizontal stresses are handled (imo) quite well in a fortuitous way, because of the structures' need to resist side force. To think that the VS/Rudder "rolled forward" around its forward attachment, after the aft two were sheared, is a challenge; the forward velocity was not high (?).

Possible. At .83 Mach an upset in Pitch caused by high speed Stall would be followed by an almost certain wing drop, resultant Roll, and then Yaw. It isn't necessary to consider a control input to have been the cause of catastrophic failure of the VS/Rudder. Any upset at this a/s would be a bag of snakes, it is highly likely that more than one attitude would be out of limits, not just Pitch.

The Rudder is designed with a taper, of course. Why? Newton. As it deflects and resists the airstream, its load is dependent on the chord of the Rudder and its distance from the Fulcrum (The Fuselage). The shorter chord of the tip produces drag equal to the longer, lower chord, because of its moment arm (leverage). At any deflection more square area is presented to the slipstream at the base than at the top, and for this reason, entertaining the aerodynamic damage to the Rudder at this area is a natural. It also would explain the degree of damage evident in each hoop, with the forward join, as the final and impromptu fulcrum of side load, was shorn.

Conclusion. More possibility of side load and damage at altitude exists than at sea level. If the structure held at the top of this flight, while exposed to enormous air loading, why would it fail (and in the manner proposed) at impact? Arse about. Beyond this, I feel the Spoiler suffered its damage at altitude. Even the condition of the VS suggests this. The battering that the spoiler endured and its subsequent separation speak of Aerodynamic loading, and in lower thicker air than the VS/Rudder had encountered at the initial upset.

In any case, without more from the authority to support the sea level separation of the VS/Rudder, I propose the conclusion needs more basis.

bear

Last edited by bearfoil; 26th Feb 2010 at 19:09.
 
Old 26th Feb 2010, 19:31
  #336 (permalink)  
 
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IF the above article was presented as a dramatic representation of a possible scenario, based on a lot of "ifs" -- and some audience-grabbing hyperbole -- fair enough. To treat it as anything more is the stuff of Jet Blast.
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Old 26th Feb 2010, 19:34
  #337 (permalink)  
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Fair enough, I agree. However, I would propose that portions of the Reports be taken in the same vein. Taking any investigation personally defeats its purpose, imo.

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Old 26th Feb 2010, 21:20
  #338 (permalink)  
 
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So far, it's unclear who was controlling the Air France plane in its final minutes. Was it the experienced flight captain, Dubois, or one of his two first officers? Typically, a captain retreats to his cabin to rest a while after takeoff. Indeed, there's corroborative evidence to suggest that the captain was not sitting in the cockpit at the time of the crash: His body was recovered from the Atlantic, whereas those of his two copilots sank to the bottom of the ocean still attached to their seats. This would suggest that Dubois was not wearing a seatbelt.
-If things happened as it usually does with AF, it is not the Captain that would have been resting at that time of the flight, but one of the copilots. But as things stand, we don't know what actually happened that day.

-It is standard practice in AF to wear a seat belt while in the crew rest area. The Captain might have decided not to wear one that day, were he either in the crew rest or in his seat.
In contrast to many other airlines, it is standard practice at Air France for the less experienced of the two copilots to take the captain's seat when the latter is not there. The experienced copilot remains in his seat on the right-hand side of the cockpit. Under normal circumstances, that is not a problem, but in emergencies it can increase the likelihood of a crash.

As a consequence, it was probably the plane's third pilot, Pierre-Cedric Bonin, a dashing amateur yachtsman, who steered the aircraft to its doom.
-The fact that it is the less experienced of the two copilots that takes the Captain's left seat, does not mean he is the one in command. In AF, it is the pilot sitting on the right hand side (the most experienced) who has command whenever the Captain's not there. In the Captain's absence, the most experienced of the pilots will either move to the RHS if he was not sitting there already, or remain where he is if he's sitting in the RHS. This because it is assumed that a pilot trained to use the instruments from the RHS seat will be more efficient using the same in case of emergency.

This article, together with a number of theories about the accident, is based on assumptions flawed by a lack of knowledge of AF procedures.
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Old 26th Feb 2010, 22:39
  #339 (permalink)  
 
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A couple of questions re the location and security of the captain.

It is assumed that he was in the rest area. If the turbulence was really bad, as is being made out, why would he be unrestrained? If the forecast weather and the experienced actual weather (turbulence, dense CB and lightning) was as bad as is being portrayed, why wouldn't he be on the flight deck where his experience and route knowledge would be at its most useful?

Of course he may have been unrestrained because he was returning to the flight deck at the time of the accident but his assumed absence from the flight deck raises possible questions about the decision not to be in command at a potentially difficult period and adds to the concerns already highlighted about the fuel upload.

I've a particular interest in this accident as I've family in Rio, have flown the route with BA (quite satisfactorily) but AF - which many non-French ex pats in Rio are avoiding at present, not necessarily logically but some at the insistence of their companies - may well have to be used by various family members from time to time.
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Old 26th Feb 2010, 23:08
  #340 (permalink)  
 
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Originally Posted by bearfoil
(Of course "Flight" can only be used advisedly, the BEA concludes accelerations and velocities that preclude this a/c from "flight").
As far as I can see they've stopped using "flight" in that context in the second report - very likely because it wasn't understood. It was a translation of the french that may make more sense in conext in that language, but didn't in english.

As efficiently as the VS was designed, it wasn't meant to survive much vertical acceleration of any description, only side forces. So on the one hand, its strength to weight ratio defines the engineering consideration, and the architecture of the three joins. Sudden decelaration in a vertical manner suggests that the VS would be driven into its mounts, not "pulled away".
Agreed, but the VS was driven into the forward mount, and there was other evidence of sudden vertical acceleration - vertical load pickup arm showing large loads "in the rudder hinge axis".

To think that the VS/Rudder "rolled forward" around its forward attachment, after the aft two were sheared, is a challenge; the forward velocity was not high (?).
There would be a sudden pitch down in the event of a tail-first imapct though ?

Possible. At .83 Mach an upset in Pitch caused by high speed Stall would be followed by an almost certain wing drop, resultant Roll, and then Yaw. It isn't necessary to consider a control input to have been the cause of catastrophic failure of the VS/Rudder. Any upset at this a/s would be a bag of snakes, it is highly likely that more than one attitude would be out of limits, not just Pitch.
Agreed, and I agree that structural failure of VS and/or other parts of the a/c would be quite possible in that event.

However, I don't see how you are going to generate the large force through the rudder hinge axis in that case. I was also going to hold-up lack of depressurisation - but having looked again I think that we don't have a fuselage forward of the aft bulkhead ripped out with the VS (as in I think one attachment is forward of the bulkhead, but it is not still attached to the VS).

We know what an airbus VS ripped off by side loads looks like (587) - and I don't think this one matches up. Also, this one was found with other wreckage, wheras if it separated before impact I'd expect to find it some way back along the track (although I do appreciate that it could separate during an upset in which most horizontal speed has been lost).

We also know that the VS can separate during impact with water -(XL in the Med - BEA probably still have that one to compare).

Last edited by infrequentflyer789; 26th Feb 2010 at 23:29. Reason: edited to fix quoting
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