This post is mainly about A330 pitot tubes and in particular the educational story of two nasty icing incidents at A330-operator Air Caraibes which I relate below. There’s no getting round the fact that the pitot issue has to be a major focus of the investigation until proven otherwise – but I would say now that in the long term it may not be the primary issue. That, I suspect, is more likely to be the question of how this aircraft came to be in the middle of a storm in the first place. We shall see.
Anyway, meanwhile back to pitot tubes, which it’s now reported that Air France is going to replace within days rather than weeks following pressure from its pilots’ unions SNPL and the much smaller ALTER. Seems there may be EASA action too.
Sources in the unions are putting it about that there have been quite a few pitot icing incidents on A330s, which I don’t think is disputed by anyone. And it turns out that two of them, in August and September last year, are unusually well documented.Air Caraibes Atlantique is a Paris Orly-based airline that flies twoA330-200s and two A330-300s to the French territories of Guadaloupe andMartinique. In a lengthy memo (full, complex, and French text below)company flight safety officer Hugues Houang describes how bothA330-200s (F-OFDF and F-OPTP) encountered severe icing in virtuallyidentical circumstances on flights between Paris and Martinique atFL350. He tells the story of DF in detail, but says the two weresimilar.
The aircraft climbed 300ft in an unsuccessful attemptto clear
the icing turbulence, then encountered severe turbulence and reduced speedaccordingly, and then suffered pitot icing – identifiable because thedetected temperature climbed to the temperature of the ice (-5C)instead of the so-called total air temperature (-14C TAT – airtemperature plus air friction heating).
Over the next 2-3minthings got quite unpleasant, with multiple warnings reminiscent ofAF447 and a period in alternate law. The crew appears to have done agood job working their way through the <unreliable speedindication> checklist facing a welter of ECAM messages and a stallwarning among other things.
Everything eventually ended happily,and what then happened was that “the management very rapidly decided toimprove the safety level of our flights by modifying the pitots on therest of the fleet”. The fix was to replace the Thales pitots, partnumber C16195AA ,with part number C16195BA. Here’s what Thales saysabout them in its literature.
UnsurprisinglyAir Caraibes then requested a meeting with Airbus and the main pointthey raised with them is very interesting. Not the pitot issue itself,but “we stressed the difficulty encountered by the crew in using the<unreliable speed indication> checklist”.
You can probably see why in the the full text below on p.12even if you don’t read French. In different places Airbus haspotentially contradictory advice regarding stall warnings in thesecircumstances which is extremely difficult to reconcile in the coldlight of day and harder still in severe turbulence with the ECAM doingits thing.
Houang concludes: “Despite these contradictoryaspects the pilots of DF knew how to react the two inappropriatestall-warnings. Furthermore the Airbus engineers understood all thedifficulties encountered by the crew in applying rapidly andeffectively the <unreliable speed indication> procedure.”
Hesays the engineers agreed to consider modifying the checklists and attime of writing on 8 December last year he was waiting to see whathappened.