A brushless starter-generator system is contained within a single housing. The housing has a first end with an opening to receive a drive spline from a motive source and an opposing second end. A brushless, rotating machine is located adjacent the first end and is kinetically connectable to the drive spline. A power control unit is adjacent the second end and electrically coupled to the brushless, rotating machine. The brushless, rotating machine is selected from the group consisting of a synchronous machine, a permanent magnet machine, and an induction machine. Electrical and mechanical interfaces are identical to a like-rated brushed version for a true “drop-in” replacement capability to facilitate replacements and up-grades.