Looking at various sources of data (as a non pilot) it would seem that an 359 or 351 can fly for about 21hr 30 min with a reasonable (just under 20 tonne) payload. Allowing for reserve and day to day variations in wind speeds this equates to a roughly 19:30 hr flight or a 20 hr block time. This would allow JFK - SYD in both directions, LHR - SYD but not SYD - LHR with any meaningful payload. I recently checked an M.Sc. thesis which calculated (from Jepperson data) that calculated that a 77L with maximum fuel but a reduced TOW could carry 72 pax (data below) but I then calculated that fitting three auxiliary tanks it might be feasible.to carry a sensible payload. My question is would SYD - LHR be possible? I don't know about the 778 but you would either need a higher gross weight 359 (probably just under 30 tonnes) or a shortened 351 (think of the 747 SP) with additional tankage. Obviously both would require development & certification which may not be justifiable for a short production run - and there is unlikely to be a high demand. Do you think that we will see SYD - LHR nonstop in the near future or will we need an extra stop. (Many years ago SQ flew LHR - SIN non stop witha 743 but but had to make a technical stop in the reverse direction.)
Thoughts anyone?
Technical appendices (from a novice)
359 - OEW 136.5, Payload 19.5, Fuel 124.0 TOW 280.0 tonnes
77L SYD - LHR winter (worst time of year)
Forecast duration: 21:14 Total reserves 2:03 (more than required, but make an allowance for adverse winds, routing, altitude, etc)
OWE 144,846 kg
Trip fuel 134,643
Contingency 10,916
Total fuel 145,559
Payload 6,583
TOW 296,989
However this is below the 77L MTOW which is about 345 tonnes and if the three optional fuel tanks are included and an additional 17t of fuel is carried the payload will increase by roughly the same about allowing a full load in high premium configuration.