 However, these airframes retained the original Colt Mk 12 cannons of the A-4Cs.In 1983, a third order of 8 TA-4S saw 16 stored A-4Bs from the Aerospace Maintenance and Regeneration Center being converted and rebuilt as the TA-4S-1 trainers (eight airframes).In 1985, as a result of four A-4S being written off in separate accidents, coupled with the low serviceability of the original batch of A-4S.