Fire Wall- I can categorically state ALL 57 British Airways 747-400s have Upper Deck Slides which are useable in the event of tail on ground. Only Door 1 slides will then be unuseable. I am current on the 400 and did my annual safety training today and specifically confirmed this point.
Where does this absurd figure of 1.3 seconds to leave seat and evacuate come from? When in the door, you can see the whole slide and who is on it. In a horizontal attitude, the angle of the slide is shallower than the other slides to cope with the tail on ground situation. If it is OK for the 747-400, how is it not acceptable for the A380? The A380 is the same, just a little bit taller- if it is OK for the 747, it is OK for the A380.