It was EZY6359 yesterday pm; A320 I believe. Descent c. FL250 over the Alps into Turin, in pretty thick convective cloud; thick enough to see only the first few m of the wing.
At one stage the entire wing leading edge had that ice.
It looks like 5cm max on the wing leading edge. I was surprised at this, as I have believed that the hot air ice protection completely prevents ice forming. I was tempted to ask the pilot(s) afterwards about it but thought that if they mismanaged the situation they would not have wanted to talk about it.
Only slats 3-5 are deiced. So the wings photos are normal. Nacelles not my subject so cannot comment.
Not too much as seen in flight – though I´m surprised to see this build up IF the cowl and wing ANTI-ice are selected on (or auto – I can´t remember Airbus!) Well, I´m not sure about the A320 – perhaps not all of the leading edge´s are heated.
For dispatch – Zero is is acceptable on those surfaces.
Xtophe wrote:
Only slats 3-5 are deiced. So the wings photos are normal
What I recall as well 
As to the engine’s nacelle… well, either it is severe icing and in a descent the system, with engines idling, is not able to cope (no worries, the shedding of ice at this thickness would normally not damage the fan blades), or forgotten/switched on late. This kind of icing can take place pretty fast.
Yeager wrote:
For dispatch – Zero is is acceptable on those surfaces.
Good luck on that. For out the MEL or MMEL, and my memory, it will state in the vein of “for flight not encountering icing conditions”. Few days in a year when say an hour flight climbing to the higher levels and then descending, all whilst not penetrating a cloud, are possible.
The Airbus (yeah, repeating myself…) has been designed as “ice resistant”, meaning only part of wings LE are de-iced, whilst none of the tail surface are. Suspected ice accretion? Add a few knots on Vref and you good to go
Yeager wrote:
For dispatch – Zero is is acceptable on those surfaces.
Yep. Before departure, all must be clean.
Dan wrote:
Good luck on that. For out the MEL or MMEL, and my memory, it will state in the vein of “for flight not encountering icing conditions”. Few days in a year when say an hour flight climbing to the higher levels and then descending, all whilst not penetrating a cloud, are possible.
I think what he referred to is that there is no ice at all acceptable for take off.
Dan wrote:
meaning only part of wings LE are de-iced, whilst none of the tail surface are. Suspected ice accretion? Add a few knots on Vref and you good to go
Wow. I had no idea. Thanks for that tidbit of information, I never knew.
What is well known is that the A32x series ARE quite uncritical for icing as opposed to other airplanes, where ice can turn lethal very very fast.
Namely the Fokker 28-70-100 series, the Challengers and the MD80 with the jets and the ATR with turboprops. The Fokkers could simply become unflyable even with very few deposit on the wings, so can the Challengers. There are at least 4 known fatals with Fokkers which were not properly de iced and quite a few Challengers as well. The MD80 was quite dangerous when clear ice formed at the wing roots on the ground and those were shed on take off and went straight through the engines. SAS lost one that way. Also one Fokker 70 had to land off airport when in severe ice both engines failed near Munich.
The ATR on the other side has had some very ugly accidents when it accumulated ice in flight. Roselawn, Como and the Dom-Rep come to mind.
Actually Airbus uses the term Vapp and not Vref as I stated above… still, below the Vapp table as used, so a 5 or 10 knots increment possible.
And this is how Airbus describes its systems, excerpts (my punctuation, bold and italic):
Wing leading edges:
Such large aircraft as the Airbuses are significantly more icing resistant than smaller aircraft. This is due to the size and thickness of their wing. It was found that thick wings collect less ice than thin ones. That’s why it was determined unnecessary to de-ice the full wingspan.
Tailplane
It should be noted that the tailplane and the fin also have leading edges that can pick up ice, but they are not de-iced. This is because it has been proven they both have large margins relative to their maximum needed efficiency.
Engine intake leading edges
These are the most carefully de-iced, because the engine fan should be best protected. Hot air is bled from the engine compressor and heats the whole of the nacelle leading edge.
Rare to see ice succeed to build up on heated surfaces. It must have either been as Dan described (forgotten to switch on) or a SH*TLOAD of ice.
Looks like some convection around.
The ice accumulated in under a minute, and remained until about 3000ft AGL – roughly the 0C level. I reckon de-ice was not switched on because much of the later flight was in VMC. The relevant section of the flight was also bumpy, with some people panicking
Cabin crew were told to get seated, which is unusual.
Looking at Snoopy’s wx pic, surprising they didn’t avoid it – would have been on radar pretty clearly.
I had already given some info re the anti/de-icing on airliners here 
surprising they didn’t avoid it
Not here to condemn nor to defend (ex-colleagues) but all is not WYSIWYG with weather radars, takes years of experience to set the radar and interpret the returns. Also, unless in a dire situation, one can’t just deviate off course… and there is terrain.
OTOH they may have just been engaged in racetrack vs holding procedures discussions and got distracted some, who knows…
Dan wrote:
For dispatch – Zero is is acceptable on those surfaces.
Good luck on that. For out the MEL or MMEL, and my memory, it will state in the vein of “for flight not encountering icing conditions”. Few days in a year when say an hour flight climbing to the higher levels and then descending, all whilst not penetrating a cloud, are possible.The Airbus (yeah, repeating myself…) has been designed as “ice resistant”, meaning only part of wings LE are de-iced, whilst none of the tail surface are. Suspected ice accretion? Add a few knots on Vref and you good to go
I said for dispatch. You obviously would not dispatch without de-icing those surfaces?? I´m wasn´t referring to dispatching in accordance with MEL and any systems inop.
Mooney_Driver wrote:
I think what he referred to is that there is no ice at all acceptable for take off.
100% correct.
