You want it to be really long eh?
Well, heres an idea.
You take the enemy camp, which beforehand you are informed is the location of a high ranking officer. You attack, but a Mi-17 takes off before you can stop it. Whilst Intel trys to track the helo, which almost certainly has the officer on board, a wave of BMPs attack you.
After they are destroyed, intel located to area, and you are to join a new squad (i'm presuming most of your old squad are dead by now) which is coming via M113 to the camp.
You board and join your new squad. The M113 takes you to an area close to the enemy choppers location, and everyone gets out. Before you move out, you leader tells you to take an AA launcher from the M113, to take out the Mi-17 if it takes off again.
You attack the base, and the Mi-17 is destroyed before it takes off (because it has no fuel of something)
Then, an enemy Mi-24 attacks, and you have to use the AA launcher to destroy it. If you have used it, you will hav to resort to enemy light machine guns and maybe a .50 cal machine gun.
Anyway, just an idea.
Hope it helps ;D