On most default and better payware AC, there is a noticeable 'jolt' upon landing, which increases in severity as landed FPM increases. But it seems on some payware, such as the Capt Sim C130 or the Iris C27, there is no particular impact effect - no real difference between landing at, say, 200 FPM versus 500 FPM. Is there a simple setting in the AC's respective .air files that can be adjusted to produce a more realistic landing impact effect?

That's probably just a quirk of the way the contact points and CoG are arranged.

The jolt isn't a feature of the .air file as far as I know, but a feature emulated by a gauge or such. The only ways of getting it generically on every aircraft, that I know, are accu-feel and ezdok, both offer landing shock effects that are visual and audible.

 

Of course, both bring other advantages that make them must-haves for many.