BOAC,
Your quote:
Based on what little I see so far I do NOT consider turbulence to have been a contributory factor in the accident.
Also in 10 minutes a cell can move quite a distance in relation to an avoid distance of 20 miles or so, so the question is not what 449 or IB did, but what 447 did. If I had 2 Drachma for all the different interpretations of 'weather' I have seen in my career I would be able to rescue Greece from bankruptcy.
I rspectfully disagree with your statements here, there is certainly information that turbulence and weather played a role in this accident. For instance:
Other airplanes flying within the same airspace
1. Lufthansa LH 507, Boing 747‐400, Sao Paulo‐Frankfurt, 20 min ahead AF 447, FL 350 , moderate turbulence, diversion 10 NM west
2. Iberia IB 6024, Airbus A 340, Rio de Janeiro‐Madrid, 12 min afterAF 447, FL 370, severe turbulence, diversion 30NM east
3. Air France AF 459, Airbus A330‐203, Sao‐Paulo‐Paris, 37min after AF 447, severe turbulence, FL 350 auf 370, diversion 80NM east
4. TAM Lineas Aereas JJ 8098, A330, Sao‐Paulo‐Paris 40min afterAF 447, FL 370, severe turbulence, emergency descent, flight route 120 NM east
Light turbulence ‐ briefly causes slight, erratic changes in altitude and/or attitude.
Moderate turbulence ‐ similar to light turbulence, but greater intensity. Changes in altitude/attitude occur. Aircraft remains in control at all times. Variations in indicated air speed.
Severe turbulence ‐ large, abrupt changes in altitude/attitude. Large variation in indicated airspeed. Aircraft may be temporarily out of control.
So, AF447 sandwiched between LH and IB, but closer to IB interms of time and distance, may very well have experienced turbulence between moderate and severe. Notice how turbulence got worse as time went on. However AF447 did not divert, but kept on the track towards the weather ahead. Keep in mind in the ITCZ, these storms come off the coast of Africa as individual cells, but often, as in this case very close together. As they get further off the coast, they slow down and generally combine into clusters. The cluster ahead of AF447 consisted of four distinct columns. The youngest and strongest was to the east and had fully developed, the other three were in the process of decay, the most decayed cell being the western most cell. The entire system is moving westward, but at a slow rate of speed. So the flights that diverted eastward needed to stray furthest from the planned route verses LH that diverted westward.
So then the question becomes why did AF447 not divert? A clue might be this from the crew of AF459:
The Captain of Air France, which has flown Sao Paulo-Paris the same night that the flight AF 447 recounts the crossing of the Atlantic.
It is a key witness in the investigation into the disappearance of the Air France Airbus over the Atlantic. The commander of flight AF 459, who left Sao Paulo on Monday, June 1 at 0:10, French time, on board a AirbusA330 similar to the aircraft, which disappeared, wishes to remain anonymous. But he remembers precisely the conditions encountered [that night].
The route earlier in the flight AF 447. Under this pilot, the weather report that day of major cloud masses in the pot black. “The satellite maps indicated a thunderstorm but nothing alarming, he says, they are very frequent in this region.” Once in the intertropical convergence zone, the crew increases the “gain” of his radar, i.e. its sensitivity.
This manipulation can make reading the screen, which is polluted by many unnecessary details, but enhances the reliability of data on clouds. “This manipulation allowed us to avoid a big cloud mass that we would not have identified with the radar in automatic mode.”
According to one of its two co-pilots, “the cloud mass was difficult to detect because there was no lightning.” The flight AF 459 to make a detour of 70 miles or 126 kilometers, while the flight AF 447, spent twenty minutes earlier, to lead through this area, added the officer. His captain did not want to confirm this information.
Another clue as to why might be this:
Air France is reviewing crew training, use of weather radar and the availability of meteorological information for pilots following the loss of flight AF447 over the South Atlantic last month.
Chief executive Pierre-Henri Gourgeon disclosed the measures a week after investigators divulged details about meteorological conditions at the time of theAirbus A330's disappearance, and the course deviations performed by other aircraft in the vicinity.
In a transcript published by the airline after he spoke to a French newspaper, Gourgeon said there was "never any arbitration" between safety and economy and highlighted operations during weather as an example.
"For example, it's written down in black and white that, when there are storms, you go around them," he says. "There is no question of saving on fuel. Pilots are totally free to choose their route."
One of the aspects of the investigation is the choice of flight track by AF447's crew. Investigators have stated that "several" other flights - ahead of, and trailing, AF447 at about the same altitude - altered course to avoid cloud masses.
These flights included another Air France A330 operating the AF459 service from Sao Paulo to Paris. Gourgeon says this crew crossed a turbulent area that had not been detected on weather radar and, as a result, increased the sensitivity - subsequently avoiding a "much worse" area of turbulence.
"Flight 447 didn't have the good fortune to encounter that first warning and may not have been able to avoid the second very active storm," adds Gourgeon.
France's BEA investigation agency says the crew of AF459, which had been 37min behind AF447, detected echoes on the weather radar which "differed significantly" depending on the radar setting.
The crew initially chose to deviate 20nm to the west but the radar then showed an extensive squall line which led them to deviate to the east by 130-150km (70-80nm).
"On the strength of that report, we are going to review the way we use radar," says Gourgeon. "Whether or not that was the cause of the loss of flight 447, we have to examine every factor and improve all of our procedures and rules."
So, was weather a factor? If you think in terms of likelyhood, possibility or even probability, IMO, it will be a factor.
Your quote:
I am pretty certain "the aircraft is at fault" since I believe if the pitots had not failed the accident would not have happened, nor, I personally believe, would it with iced pitots with a 'conventional' FCS, but am keeping an open mind on the rest
Interestingly, four of the five planes that night were Airbus. I wonder which brand of pitot tubes the other three Airbus planes had where pitots didn't fail? Could it have been because of the particular pitot brand in use or because of weather avoidance by diversion from their intended flight path?
Not trying to change your mind, just some information to think about...