In this contribution, experimental analysis is introduced to determine the unloading characteristics of granular solid from flights. In a flighted rotary drum operated at optimum-loading. The studied unloading characteristics are: kinetic angle of repose of solid reside inside a flight, individual flight holdup, final discharge angle, cascading rate, and height and time of falling curtains. These characteristics are determined as a continuous function of the flight angular position. The tested drum is 0.5m diameter and 0.15m length, the rpm changes from 1 to 5, two number of flights 12 and 18, and two flight length ratios 0.375 and 0.75 are researched. Results revealed that: flights holdup is mainly influenced by flight length ratio among other studied parameters. Maximum height of falling curtains can be achieved when operating rotary drums at optimum-loading, since the bottom solid bed is no longer exists compared to over-loaded drums.