China originally bought 14 new and 6 used IL-76 starting in the early nineties, of which 14 are still used in the transport role. Four have been converted into KJ-2000 AEW&C aircraft and the remaining serve as test aircraft.
Further attempts to increase the number of available IL-76 airframes failed when a 2005 contract with Russia for the delivery of 34 IL-76 and 4 IL-78 refuelling aircraft could not be executed.
Only in 2010 has China been able to purchase another 10 used IL-76 airframes from Russia and Belarus, which are now in the process of being overhauled, with the first delivered this month.
To help speed up development of the Y-20, the Chinese sought assistance from the Ukrainian Antonov aircraft design bureau, with which has an extensive working relationship and which has extensive experience designing transport aircraft, including the An-124 and An-225.
Both the Y-7 and Y-8 transport aircraft currently used by the Chinese military trace their roots to aircraft originally designed by Antonov, which also helped in improving both aircraft for China.
According to Ukrainian claims, 3 design candidates were submitted to the Chinese to address their requirements for the Y-20.
- the turboprop An-70
- the An-77, a version of the An-70 with turbofans
- the An-170, a heavily modified and larger version of the An-70
The Y-20 design will address some of the shortcomings of the IL-76 design. The IL-76 fuselage and cargo hold is relatively narrow, which is a significant drawback in the transport role.
In general, most cargo tends to bulk out before they hit their weight limit. The Y-20 fuselage and cargo hold has thus been made wider and more efficient than the IL-76, allowing better cargo dimensions.
The Y-20 is also more aerodynamically efficient than the IL-76, which is a relatively outdated design. Modern composites and advanced avionics will also be incorporated into the Y-20. A supercritical wing may also be used.
The original design of the Y-20 also had to be changed to account for the increase in the weight of China's latest tank designs, which it must carry, such as the ZTZ-99A2, which comes in at around 60 tons.
The Y-20 will initially use the Russian Soloviev D-30KP2 engine, the same engine used in the IL-76MD. Three engines are in development for the Y-20:
- the WS-18 based on the D-30KP2
- the WS-20 based on the WS-10A engine
- the CJ-1000A and derivatives, which is best suited but may not be available as quickly as the previous two
In the meantime, China has ordered 239 D-30 engines from Russia, 55 in 2009 and 184 in 2011. They will be used on the IL-76 and Y-20 aircraft, but also in the upgraded H-6K bomber aircraft.
Credit original poster, via Chinese Internet