If I have understood correctly, the 778 has the payload advantage at extreme ranges (16,000km+) but the A35K is likely to have the cost advantage as trip length decreases.
That suggests that the 778 has the economic edge. Of the potential ULH routes, the key routes (SYD / MEL to LHR/JFK) are at those extreme ranges. The success or failure of project sunrise is going to turn on those routes, and the extra payload and therefore revenue potential of the 778 is quite important. If you then look at the routes between 14,500 (upper range of 789) and 16,000km, there isn't much there (MEL - DFW, SYD - ORD, PER - LAX). Everything else is over 16,500km or under 14,500km. Routes under 14,500km is probably best served with a 789 (PER-CDG) or a 779 (SYD-LAX).
I think the gap between the routes suited to the 789, and the routes suited to the 778 isn't big enough, and the routes that fall into the space are not important enough.
What Fred had done on this thread is very good but they are just models, every model has limitations, and for conclusion to be valid one needs to understand them.
For example Fred has not modelled the A350 variable camber wing or the resulting variable CP and reduced downforce on the tail. If we look at the MEL if the aircraft is dispatched for just with pair of spoilers inoperable (which are used as part of the variable camber), it results in an 8% increase in burn. That does not mean however Fred’s model should be reduced by 8%. We are looking at performance differences in the range of a few percent, a few percent however on a ULH flight is significant.
He has also stipulated that step climbs are based upon the ability of being able to achieve 600 fpm, you will get step climbs with less than that on the A350. In reality step climbs are optimised on where the best overall specific ground range is achieved.
I don’t have any inside knowledge on what will be chosen, I have to rely on what QF is saying in public, e.g.
“Qantas will aim to place a new order by the end of 2019, aiming for delivery between 2022 and 2023, Joyce said. He said the planes had to be flexible enough to fly Sydney-London and from Sydney to Hong Kong or Beijing.”
From https://www.scmp.com/news/hong-kong/hon ... s-says-non
The A350-1000 will carry less payload mass compared to the 777-8, however it has more revenue space above the floor the airline can configure for revenue. It also have more volume in the cargo hold, with the ability to carry an extra pallet compared to the 777-8. The A350-1000 should more flexible at the shorter flights indicated of SYD-HKG and SYD-PEK.
This is very similar in the comparison between the A340-600 and the 77W. The A340-600 would lift more payload mass, however had less revenue space above and below the floor.
The same article also said
“Our belief is [ultra-long-haul flights are] not going to be full passenger payload and freight, but there is sufficient capability to make it commercially viable,” Joyce said.”
This directly contradicts the thoughts above advocating higher payloads.
In a related article it states
“However, regardless of the jet chosen to make those marathon 18-20 hour treks, there’s no longer an expectation that it will carry the airline’s previously-stated goal of 300+ passengers across four classes.”
Which again is pointing towards lower payload expectations.
From https://www.ausbt.com.au/qantas-ceo-dia ... pectations
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News