i guess for run from shilka only diving to earth is not enough.......
Bullets are not guiding! Only flying ballistic.
If pilot does see tracers incoming then he has 1-2 sec. to make any maneuver. This would avoid predicted point of burst intercept + chance to hit.
This is why Shilka is not exactly aiming for the predicted impact point, rather is sprays the ammo at an area around of it.
PS: And this is the exact reason, why its range (5,5km) and effective range (2,5km) is different.