"As far as the letter designations, I'm not sure  who introduced the concept. The A-man was the crew  chief, and his job was to oversee the whole bomb and  gun loading procedure. He racked the bombs and helped  with any final arming wire installation and bomb  loading post checks. The B-man's first job was in the  pre-check of the aircraft weapon system. He would  climb up into the cockpit and pickle off all the bomb  racks while the rest of the crew checked to make sure  the racks would release. On a rare occasion, we would  have to swap out a rack prior to loading. The B-man  would also help in loading the first bomb, but after  that he was usually involved in installing the arming  wires after the bombs were loaded. The C-man was the  MJ-1 driver, and his job was to get the bomb into  position so the crew chief could rack it in from the  loading table. The C-man would also help in the  loading of the guns. The D-man's job usually  positioned him at the tail fin, and his job was to  help guide the bomb into position. All bomb crew  members would help in the loading of the guns, final  arming wire installation and revetment clean-up after  the load, making sure that all pieces of arming wire  and scraps from the loading process were picked up.  Bomb loading crews who had been together for a while  as ours was, became extremely efficient at loading an  aircraft in a short period of time."