Joe Egginton wrote:

That's 12 mph vertical speed Jack, I thought Jumbos were much quicker
than that. Though I suppose it's the horizontal speed I'm thinking about.

That's correct. 1,000 feet per minute would be good for a fully
laden Jumbo on a hot day.

A Jumbo just after take off can be extremely heavy and climb very badly
indeed, but of course the weight reduces in flight as fuel is consumed.
If an engine failure occurs just after take off, the climb is minimal
and if two fail after take off - well. "Windsor Castle. Here we
come"

That's why they have to dump the "disposables" if a problem
occurs when heavy - fuel, baggage, toilet contents (you will have
heard of those blue-ice meteorites) in that order.

Phil will tell us where the approved dumping grounds are.

Jack