Never forget one of our 321's getting off the ground with water in the 'weight on wheel' sensors. Not only would the gear not retract, but the computers went bonkers (as one would imagine given the machine thought it was on terra firma).
Being the nosey git that I am, I had a nose on the FD......the ECAM was full of red....
Speaking to the pilots, they both said how surprised they were when they selected gear up and the computers had one heck of a 'moment'!!
