An aircraft auxiliary power unit assembly includes an aircraft skin providing a cavity. The aircraft skin is secured to a structure in an assembled condition and provides an opening. An auxiliary power unit is arranged within the cavity and secured to the structure. The aircraft skin substantially covers the auxiliary power unit in the assembled condition. An inlet duct is removably secured within the opening and is selectively connected to the auxiliary power unit between installed and service positions. The installed and service positions are with the aircraft skin in the assembled condition. A method of servicing the auxiliary power unit includes removing the auxiliary power unit inlet duct from the opening in the aircraft skin. The auxiliary power unit that is arranged within the cavity of the aircraft skin is exposed. A portion of the auxiliary power unit is serviced through the opening.