Originally Posted by
flyboy777
Ah so range is a factor!
I think the payload (increased due to more fuel for range) is the key perhaps? The higher the payload the higher the take off speed theoretically. So whilst Dubai is possible, London would require such high speeds there would be a blow out?
Still, I wonder how hot Johannesburg is at 9pm?
Surely it all comes down to weight? There are a set of performance graphs
here. Page 47 (number on the sheet!) seems to suggest that without any other de-rating the MTOW is derated by 75,000 pounds at 5,500ft, 15oC temperature elevation and an unlimited runway - note the tire limit on take off speed. I'm sure Jumbodriver will correct me, but doesn't that 75,000 pounds (25% of max with another 8-10% required for reserves) mean you lose 1/3 of the potential range, or you have to take out cargo and/or passengers which makes the trip potentially un-economic. Higher temperatures make these numbers even worse.