I think it is reasonable to argue that Y-20's development and other work on larger sized aircraft (H-6K, Y-9 etc) would have provided a sufficient base of experience such that key subsystems such as cockpit, flight control system, navigation and avionics etc, could all be developed for a "military specific" C919 airframe.
That is no doubt true, but given the breadth and depth of international participation in the C919, it's simply a big task in terms of scale (if not so much skill). Furthermore, if it took much more than 5 years, the availability of the WS-20 could become a moot point, as by then the CJ-1000A may well be just around the corner.
I think that's what crash8pilot wanted to express - while it's hard to overstate the significance of this milestone for the Y-20, the relevance to the C919 is much more limited than foxmulder is suggesting.
To be frank, as much as WS-20 marks a remarkable progress in China's aviation industry, the engine is still on part to the Boeing-737 engines of the 1980s and 1990s. It is at least a generation or more behind the LEAP. Nonetheless, it still marks a significant progress by Beijing, and I will not rule the possibilities of militarized C919 platforms using the WS-20. Yet, civilian airliners require much higher standards.Calm down ... with the WS-20 the C919 will surely be able to fly but it takes times, money and even more with the WS-20 it won't reach its performance parameters since it is an older generation engine. As such, to be competitive, they need to wait for the CJ1000A
There are tankers in the same size-bracket as the C919 (MTOW around 80t), but these are invariably derived from tactical transports rather than airliners (KC-130J, KC-390). Their market is small air forces which cannot afford a separate fleet of dedicated, heavy tankers or countries with a requirement to refuel helicopters - neither applies to China.
7 built and used. 2 in Canada 5 German. They are useful as not every mission or nation needs a large tanker. They cost a lot of money, time and man hours. Even a small tanker for a nation that badly needs them can be significantly useful. H6 conversation like other bombers conversations tend to be a stop gap. Mostly built until better options become available.Seriously? One is produced like 5 from old airframes as "just in case" option, the other is a brainstorming exercise. H-6 example would be slightly better for your point I guess... lol.