Unsung war

How the heck do you shoot down that darn C-130 down at the launch
center.
At the start you see him coming quick !! fly by !!
no time to shoot at all.
Game very slow and lags when you try a port turn on him by this
time C-130 drops payload your pretty much done at that point
at lest I am done hit start button !! the bad guys over run the
launch center so fast....

Any help ???...

Thanks