Peter,
Re your question about the 747-some more figures for you........
The following weights are the max structural limits for British Airways Rolls Royce powered 747-400's:
Zero Fuel Wt...........246,750kg
Taxi Wt..................397,800kg
Takeoff Wt.............396,890kg
Landing Wt.............285,760kg
Hope that's of some use!
Good luck, and hope you get to fly the beast one day
