I think maybe they are worrying that 250 people will not be able to make it off the upper deck in an emergency evac without maiming or killing most of them.
Of course! Because Europeans can't build aeroplanes, they'd obviously design one with upper deck exits that didn't work.
from
http://denver.bizjournals.com/phoeni...y1.html?page=2
"Since it's a double-decker aircraft, the escape slides are tremendously long in some instances. The walls of one section of the test facility will be 60-feet high," Oney said. "It's a clear-span structure. That means there are no posts. It's required because of the type of testing that we have to do with these very large slides."
Early models of the A380 aircraft will accommodate 550 passengers in a three-class, two-level structure. Later models are expected to carry as many as 650 passengers.
The aircraft is so large, it has 16 emergency doors and requires 16 escape slides, compared to a 747 aircraft which requires 12, Oney said. Later models will have 18 emergency exits and require 18 escape slides, he said.
The longest upper-deck slide for an A380 will exceed 50 feet, while the longest upper-deck slide on a 747 is 46 feet, he said.
The slides are made of a nylon-based fabric that is coated with urethane or neoprene. They have to be packed tightly into small bundles placed at the foot of emergency exit doors.
The FAA requires Goodrich to conduct between 2,000 and 2,500 tests on the slides to make sure they can accommodate a large number of passengers quickly and withstand wind, rain and other harsh weather conditions.
The upper-level slides, which are wide enough for two people, have to enable the evacuation of 140 people per minute, Probett said. It's also an FAA requirement that the slides enable a 90-second evacuation of 550 passengers from the A380, she said.