We already know as of 16th February 2016 that RR
is offering an Extra Performance version of its Trent XWB 84 with EIS in Q4
2019. This will feature a 1% improvement in fuel consumption.
We already know that RR
is well forward with is 'plastic' fan, which will (together with its containment) be lighter that the hollow titanium RR
fans currently in service.
My guess is that this new fan will pass more air than the current models, whilst spinning at lower speeds. Why? Because each aerofoil will be 'thinner' thus causing less obstruction to the airflow. A slightly larger diameter fan might be possible under the existing wing, thus improving sfc even further, and improving the engine-out margins for hot or high.
Thus in my view RR
already have the technology in place to do a Trent XWB 97+ which will be all that is necessary for a potential A350-1000+ conceived as being slightly below the 777-9 in terms of payload-range. This -1000+ would address 80-90% of the heavy twin airline market, and so sell well against the 777-9.
New customers for the 777-8 are surely non-starters for all practical purposes, no it does not even get onto the racecourse. The A350-900 Extra Long Haul with its Singapore Airlines treatment yet to be applied to the A350-1000 makes the -8 and its long timescale a lost bet.
I have not been backward in suggesting that owing to the pure bad luck of low oil prices, the money already expended on the 777-9 (optimised at a niche of only 10-20% of the heavy twin market) has already disappeared into this (now) black hole of a project. The three partners, Boeing, GE
and the ME3 need in my opinion need to review their situation, like Scrooge was want to do, before benefiting the black hole with further largess.