An inlet door system includes a duct, an inlet door, and a plurality of openings. The duct is configured to extend from the auxiliary power unit (APU) to an intake opening formed in an outer surface of an aircraft. The duct includes an inlet port, an outlet port, and a duct sidewall extending between the inlet port and the outlet port. The inlet door includes an inner surface, an outer surface, and an outer peripheral edge between the inner and outer surfaces. The door is rotationally coupled to the duct, and is configured to selectively rotate between a closed position and a plurality of open positions. The openings extend through the inlet door between the inner surface and outer surface, and each opening is disposed adjacent to the outer peripheral edge.