took me a while to figure this one out too. still not too sure how i did it, but here's
what i did. after shooting down the helicopter, don't rappell down straight away. run
around, find a rpg, the fire the rpg at the sandbags directlt opposite the rappell place.
pick up a normal gun, go down, and a gap should have appeared in the sand bags. for some
unknown reason this didn't happen the first time i tried, god knows why. all i can say is
give it a go. good luck!!!

ahhhhhhhh this is pissing me off, how the hell do u do it!!!!!!!!!!!!!!

after shooting down the helicopter wait until the men all charge the sandbagged entrance
then as they all die there wil be a big explosion , and a gap will appear , go into that
being careul to kill all the men who attack you ,go up the stairs and left when u reach
the top , straight along the corridor to the end , and through the gap where a wall has
been blown apart , then through the doors on your left

Yeah this happened to me, i feel your pain!!! First time I tried there was a bug in the
programme and a gap didnt appear in the side entrance. i had to restart the chapter and
after doing so, after shooting down the hellicopter a tank appears and shoots a gap in the
side entrance open. Hey presto!! :o)