Go to a red and white, upright gas cylinder (can be found at all military bases and captured places) and aim at the valve at the top. Fire your grappling hook at it. You should now be latched on.

Aim at the valve at the top (the guide will turn red) and fire one bullet at it.

You will fly more or less straight up in the air. You have to jump off though as it starts to lose power as it will explode.