wonder if the WS-20 nacelle has thrust reversers. it would be important for short field performance and ground maneuverability.
I would expect so. More interesting is the question whether it can reverse the core exhaust too, or just the bypass stream (as is usual on high-BPR engines). Uniquely, the F117 on the C-17 has this ability, and due to its low-BPR design with bucket-type reversers, so does the old D-30KP.
Photos of the Y-20 I’ve seen suggest y-20’s wings are simpler than the C-17’s, with smaller high lift devices and no overwing spoilers. so I suspect the short field aerodynamic performance would not be the equal of the C-17.
Actually the opposite is true - the C-17 has very simple fixed-vane drop-hinge (as opposed to sliding track) flaps, while the Y-20 basically copies the Il-76 fully articulated triple-slot flap system. The difference is a bit deceptive though because the simplified flaps were the subject of extensive prior research and optimization (YC-15), but most importantly take advantage of innovative solutions.
Firstly, external blowing - the engines are positioned higher (but also further forward, to avoid inducing locally supersonic flow in cruise), so the exhaust stream blows over the flaps when extended. Secondly, as on the 787, A350 and A400M the spoilers can deflect *downward* to control the width of the slot between main wing and fixed flap vane and provide smooth camber. Although the Y-20 most definitely does have spoilers, I doubt they have this function and the engine positioning suggests there is no external blowing either.
Still, the Il-76 does quite well in terms of short field performance (though at the cost of much higher mechanical complexity), so I expect the Y-20 will be decent.
