An accessory system for a gas turbine engine having a driveshaft with an axis of rotation is provided. The accessory system includes a towershaft coupled to the driveshaft and driven by the driveshaft along a towershaft axis of rotation. The accessory system also includes a shaft including a first shaft bevel gear coupled to a towershaft bevel gear. The shaft is rotatable by the towershaft along a shaft axis of rotation and defines an air-oil separator. The shaft axis of rotation is transverse to the towershaft axis of rotation. The accessory system includes a first accessory drive shaft having a first accessory bevel gear driven by the shaft. The accessory system also includes a second accessory drive shaft having a second accessory bevel gear driven by the shaft.