Three Thursday-afternoon academy sports bits, one per service: 1. Army at Benning, on TV: It’s a little early for Saturday college football, but if you’ve got the itch, scratch it with “Army Spring Football Mission: Fort Benning,” a 60-minute documentary on the Black Knights’ trip to Georgia for a scrimmage at Doughboy Stadium. Catch a short preview here, during which Army head coach Rich Ellerson says the magic words regarding the Benning experience for all Black Knights fans: “It’s going to pay off on Saturdays.” CBS Sports Network will air the doc at 8 p.m. Eastern, according to an Army…