Defending your position at the ferris wheel was the hardest part for most players in the original game.
However, I found this video on youtube which made this part so much easier.
All credits goes to NZL KNUCKLEZ for the video.
I got attacked by two enemies that came in front of me so be ready for that. But after that you should be safe till the helicopter arrives.
Jezz41 said: Just want to add you can put C4 down before putting Cpt. MacMillan at the spot next to the Ferris wheel. After you put him down it will restock all your C4 so you can use 12 instead of 6.