You can pass your details on at the roadshow but as far as I'm aware there are no sim assessments on site (unless things have changed recently).
Just be aware an offer of DEFO on the A380 isn't necessarily guaranteed. Things can change according to requirements and you could be placed on whichever fleet you are needed on at that particular time.
If you come here do it for the right reasons not simply because of type, otherwise you may be disappointed. And come here with an open mind without any presumptions or unrealistic expectations on what you may read on Pprune... it makes the adjustment A LOT easier!
