An electrical generating system for an aircraft comprising: a first shaft (106, 206) drivably connected with an engine gearbox of the aircraft; a second shaft (108, 208) co-axial with the first shaft (106, 206) and drivably connected with a generator of the aircraft; and a connection unit (110, 210) in which the first and second shafts are selectively engageable with one another, the connection unit comprising, a solenoid coil (118, 218), an armature (134, 234) co-axial with the first (106, 206) and the second (108, 208) shafts, a plurality of balls (132, 232) positioned circumferentially around the armature (134, 234) in contact with the armature, wherein the armature includes a first cylindrical segment (135, 235) and a second cylindrical (136, 236) segment, wherein the armature is selectively movable between a first axial position and a second axial position responsively to actuation of the solenoid coil, wherein the first axial position of the armature positions the armature so that the balls (132, 232) are in contact with the first cylindrical segment (135, 235), wherein the second axial position of the armature positions the armature so that the balls (132, 232) are in contact with the second cylindrical segment (136, 236), wherein the balls engage with both the first and second shaft when the armature is in the first axial position so that the balls are positioned to transmit torque loading, through the balls, between the first shaft and the second shaft, wherein the balls engage with only one of the first or second shaft when the armature is in the second axial position so that the first shaft and the second shaft are free to rotate independently of one another. a first shaft (106, 206) drivably connected with an engine gearbox of the aircraft; a second shaft (108, 208) co-axial with the first shaft (106, 206) and drivably connected with a generator of the aircraft; and a connection unit (110, 210) in which the first and second shafts are selectively engageable with one another, the connection unit comprising, a solenoid coil (118, 218), an armature (134, 234) co-axial with the first (106, 206) and the second (108, 208) shafts, a plurality of balls (132, 232) positioned circumferentially around the armature (134, 234) in contact with the armature, wherein the armature includes a first cylindrical segment (135, 235) and a second cylindrical (136, 236) segment, wherein the armature is selectively movable between a first axial position and a second axial position responsively to actuation of the solenoid coil, wherein the first axial position of the armature positions the armature so that the balls (132, 232) are in contact with the first cylindrical segment (135, 235), wherein the second axial position of the armature positions the armature so that the balls (132, 232) are in contact with the second cylindrical segment (136, 236), an armature (134, 234) co-axial with the first (106, 206) and the second (108, 208) shafts, a plurality of balls (132, 232) positioned circumferentially around the armature (134, 234) in contact with the armature, wherein the armature includes a first cylindrical segment (135, 235) and a second cylindrical (136, 236) segment, wherein the armature is selectively movable between a first axial position and a second axial position responsively to actuation of the solenoid coil, wherein the first axial position of the armature positions the armature so that the balls (132, 232) are in contact with the first cylindrical segment (135, 235), wherein the second axial position of the armature positions the armature so that the balls (132, 232) are in contact with the second cylindrical segment (136, 236), wherein the balls engage with both the first and second shaft when the armature is in the first axial position so that the balls are positioned to transmit torque loading, through the balls, between the first shaft and the second shaft, wherein the balls engage with only one of the first or second shaft when the armature is in the second axial position so that the first shaft and the second shaft are free to rotate independently of one another.