Chinese Aviation Industry

You will need to conduct wind tunnel testing, check changes to the center of gravity and stresses on pylons and wing. Then conduct tests with the engine on the wing.
Finally replacing the engines is like half the cost of a new aircraft usually.

It is probably not worth the cost to re-engine.

In the case of the US tankers and B-52 bomber the engines were not manufactured anymore and the extra range/time on station makes a massive improvement in technical characteristics.

gelgoog said:

In the case of the US tankers and B-52 bomber the engines were not manufactured anymore and the extra range/time on station makes a massive improvement in technicals characteristics.

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I would expect replacing WJ-6 with WJ-10 would yield similar benefits, from most accounts I've heard, WJ-6 is just a terrible engine in both efficiency and reliability.

gelgoog said:

You will need to conduct wind tunnel testing, check changes to the center of gravity and stresses on pylons and wing. Then conduct tests with the engine on the wing.
Finally replacing the engines is like half the cost of a new aircraft usually.

Click to expand...

If they decide to start making new special mission Y-9s with WJ-10s as some people have rumored, it'll be something they'll have to figure out anyways making replacing the existing fleet easier. Engines might be half the cost of a normal aircraft but with special mission aircraft the electronics onboard is usually much more expensive than the actual base aircraft making it more economical for reengining rather than just retiring them and procuring new aircraft.

Tomboy said:

from most accounts I've heard, WJ-6 is just a terrible engine in both efficiency and reliability.

Click to expand...

It should be. The Ivchenko Al-20 was basically a TV-2 turboprop designed at Kuznetsov design bureau by Junkers engine designers. It is an early 1950s engine. Stalin era. The TV-2 engine design was passed to Zaporizhzhia, Ukraine to be serially produced there, that is when it became the Al-20.

Kuznetsov design bureau designed the more advanced NK-4 engine as a replacement for TV-2 but it was not accepted. A lot of people think this was more due to politics than anything.