as the captain had earlier explained to sergeant scarburg the c-7a ( caribou ) would be the transport aircraft that would deliver the team to the dz ( drop zone ) in cambodia ; however , he still had two problems : 1 ) jump qualified personnel are required to undergo refresher training every six months ( none of sarge 's men had ) 2 ) sarge believed none of his team had ever jumped from a caribou ( they hadnt ) .