Le Monde is reporting that AF447 was flown at the wrong speed through turbulence from the moment problems arose with its flight control systems and until it broke apart in flight.
It also says Airbus is about to issue an advisory to all A330 operators to manually maintain recommended speeds when flying through adverse conditions. This presumably means the minimum manoeuvring speed although it doesn’t use that term.
Whether a jet is flown too fast or too slowly through turbulent air there are serious risks of loss of control and structural damage. Too slow a speed can cause a high altitude stall. Too fast a speed can break critical control surfaces especially if fierce changes in wind directions or updrafts and downdrafts are encountered. Airline operating procedures include company rules for avoiding or managing these risks based on manufacturer recommendations following certification.
However the now widely reported versions of the automated service messages that have been leaked to the media by sources in Air France imply that the pilots may no longer have been getting correct airspeed data because of problems with external sensors, including icing. (Icing at 35,000 feet is considered extremely rare, because it is generally too cold for water to exist and without water present ice particles would remain loose and not freeze on to surfaces.)
Le Monde reports that sources close to the official French investigation dispute the widely published chronology of automated messages received from AF447 in particular the timing of a message that reported breakdowns in the ADIRU units and other flight control computers. It repeats the most detailed of those reports as they appear in the Brazilian press and doesn’t report any alternative version that might have been offered by its sources near the French investigation.
However it does report that the last message, a cabin vertical speed alert, occurs either immediately before or after the jet broke apart, and was caused by the decompression that either led to or was a consequence of the breakup.
Morning update: Some of the debris collected in the search area is material washed off or thrown off cargo shipping. A large fuel slick has also been identified as maritime in origin. However real wreckage from AF447 is also being collected by helicopters and delivered to search vessels with many vessels still en route to the debris areas from France and Brazil. No bodies have been sighted and none are expected to be found this far into the search and recovery operation which is focused on looking for wreckage that may contain more clues as to what happened late on 31 May and early on 1 June.
Debate continues at the technical level as to whether the A330-200 was flown too fast or too slow through severe turbulence by pilots who appear to have been receiving faulty air speed readings. The automated messages received in the Air France operations centre in Paris via satellite confirm that the Airbus flight computers had been disabled early in the crisis and that it was being flown under manual rules until it broke apart and crashed.
6 Comments
Call me a Tech Nerd, but, I’d just like to say how interesting I find these articles. Very informative and entirely fasincating. Cheers & thanks.
“35,000 feet…generally too cold for water to exist”
You don’t mean ‘too dry’?
Your right Mark. I should have said both too dry and too cold. Some weather authorities discussing this convergence zone have quoted normal readings of around -37C and it will be very interesting to see what the inquiry learns about the conditions on the day. One theory mentioned elsewhere is that the pitot problem may have been due to its getting jammed with an unusual density of ice crystals, however there was also a reference in Le Point, a weekly but which has a website to white frost forming on one of them. There is a problem with that report in that it was dark and the pitot can’t be observed from within the cabin, and the ‘frost’ would have to have been solid ice. This is just one of those little anomalies in the leaks from Air France or sources close to the inquiry that I’m watching to see if they get resolved. I have no doubt there is something in all of them but they may have been mangled in the telling or reporting.
Ben. I’ve read posts from pilots who report icing as high as 39,000 feet. I also think back to the British Airways B777 that ‘crash-landed’ onto the runway at Heathrow last year with its engines producing only idle thrust. Correct me if I’m wrong but haven’t the preliminary investigations (or at least suspicions) put that down to an accumulation of ice in fuel lines/tanks/pumps during the extended, high altitude flight over Siberia?
The short answer concerning BA038 is Yes, but the water was said to have come from within the fuel tanks as a residue which because of the design of the RR engines used had accumulated undetected in a manner which led to the both engines experienced an uncommanded power roll back shortly before crash landing at Heathrow. The flight had experienced very cold temperatures en route as you point out and the final report of the investigation has not yet been released. There was no abnormal external icing of the BA flight.
“”You don’t mean ‘too dry’?”"
No, “Le Monde” means too cold. It is dry because of the absence of water vapour, due to it being …. too cold!