Will Russia be able to fund and develop the Su57 on their own? Seems quite ambitious.
I don't see why not, they are almost there anyway.
If I recall correctly the first serial production jets will enter service next year while the new engine is probably 3-5 years away from operational use. Russia aren't in a hurry to acquire them, having only ordered an initial twelve, but that is also consistent with how they ordered and subsequently built up the Su-35 fleet.
If that is the case, why is India walking away right now if they are so close? That is throwing a lot of cash away near the finish. Something doesn't add up here.
These are kinda my thoughts on the whole situation - not a specific reply to your post BTW, but I don't think they're close at all - just because it's flying doesn't mean anything. The complicated stuff is to follow, and honestly it's a little ridiculous how nonchalant people are about them casually coming up with a 5th gen engine as if it's a given - they've been blowing up their flagship engines since early in the cold war, and they're only better now because nothing is pushing the envelope - which they'll need to do big time with this aircraft. The engine technology is the key to true 5th gen performance (at least, as far as the program being a technological leap for Russia) and they don't seem too close.
My point is - how are they going to pursue flight envelope expansion and software / control surface fine-tuning and such if the aircraft isn't even near its target thrust or speeds? The engines are a huge deal, maintenance and range are probably severely limited as well.
As far as India is concerned, I'd imagine they can draw the same conclusions we can about less-than-ideal RCS performance, especially from the rear, bottom, etc. Fit & finish seems poor (imagine that) lines, hinge points, joints, panels, etc Okay they're prototypes, but this stuff should have been ironed-out on a computer screen yet it's in flying config now. It's just not going to be an aircraft with the perfected design/construction and stealth elements of the F-35, much less the uncompromising F-22.
They seem to hint at avionics and sensors as being a major issue, which is easily a possibility. Based on the way Russia tries to do things (especially given the propaganda spin they've already been having fun with regarding the aircraft) it's possible that sensor, targeting, and general avionics are FAR behind schedule/budget and they just wanted to get the thing into the air. I doubt they've been able to provide India with anything ON PAPER that says they're in the right direction. Obviously not performance yet, no RCS data either (even w/o the metal cowls there still doesn't appear to be RAM yet) - I don't think they've tested any weapons bays, trapeze launchers, etc. There's a LOT of new stuff to figure out.
Lockheed not only leveraged their own experience with advanced S/A-friendly cockpit design and ergonomics, but they've got countless sub-contractors out there providing key components for their 5th gen aircraft and (for better or worse) a nearly unlimited budget. I'm sure Russia can achieve similar success eventually
, but it's going to be a VERY long process, and the ability of the SU-57 to provide and receive tactical battlefield information, decipher it in real time, relay it to appropriate elements, etc - in a sensor-fused manner may never be achieved to the degree of the F-35. In order for the aircraft to be effective, the cockpit and avionics need to function in an "organic" manner, which is another 5th generation design element that will be difficult to match.
In this day and age, the flexibility of the F-35 and the information it's able to deal with and provide in a dynamic battlefield environment is really becoming a key marketing point for Lockheed. I think most would agree that it's unlikely any aircraft will approach it in those aspects for decades. That could be a major SU-57 turn-off for India, though they have less to integrate with in the first place I suppose. From my point of view, the SU-57 has always been somewhat of an interceptor (Russia's favorite type of plane!) Yes it has a large payload, ground attack capability, and 3D vectoring.. but IMHO an all-around 5th gen plane needs all-around stealth. I don't really think India needs a big expensive twin engine plane optimized for BVR head-on stealth engagements, they need a modern swiss army knife (like everyone else right now!) Russia didn't design the SU-57 to be a hot-selling export, they built it to counter US 5th gen based around their own needs, and "pride" of having something that looks better on paper.
Plus could you imagine the maintenance, parts, software, and other logistical issues that would plague India if they were the ONLY ones outside of Russia operating the type? Meanwhile the F-35 has complex integrated parts networks spanning the entire globe and it's already largely IN PLACE.
Yeah the F-35 is expensive, but there's a reason why everyone seems to b!tch and moan publicly for months or years then buy it anyways.