Arm the emergency release and escape in under 2:30 on Sulaco Falls
The end of Sulaco Falls (Mission 3) is a hanger where you must operate some computer terminals while fighting Weyland's troops. When you enter the hanger, there will be an upstairs platform that you need to get up to. In the first room there's a computer to arm. Once finished, proceed to the end of the platform where the next computer is. Before you get to it, your "walkway" will collapse. Turn around to see a new room open up (with enemies inside) and once cleared, use the computer in there. Wait for the new pathway to arrive and proceed to the final computer. Once you're finished, quickly hop down to the lower level and proceed to the ramp of your dropship. This will unlock on Recruit difficulty if you finish under 2 and a half minutes when the cutscene starts to play. If your takin too long, pause and select "restart checkpoint" to try again. The video below shows the layout and strategy.
Location: Mission 3 - Sulaco Falls At the very end of mission 3 you will come to some sort of hangar. The relevant section for this achievement begins as soon as you enter this area. You have two minutes and thirty seconds to activate three switches and enter the dropship. It's recommended to play on the easiest difficulty (Recruit). This allows you to rush into the enemy groups without dying. Use a shotgun to take them out while running to the next switch. After all switches are activated you simply drop down and go to the dropship. The missions will end here and the achievement pops during the next cutscene. Make a backup of your save game so that you can try it again without replaying the entire mission.
You can do this on soldier difficulty easily. when you get to the room, run to the stairs on the right hand corner and go up them. there will be a console that you have use to arm the first bomb. then run all the way around the catwalk and a piece of it will fall. you have to turn around and several guys will come out a newly opened door. kill them quickly and go in the room and use the console by the window. now run back out and go to where the piece of the catwalk fell. a crane will now move an empty cargo box over so you can jump through it and arm the last console. now just drop down and ignore the army of guys down there and all you have to do is board the ship (essentially you just have to get on the ramp or get very close to it). A cut scene will began and you just get the achieveme