The main objective of this study is to assess the performance of T56 turboprop engine using the exergoeconomic, sustainability and environmental damage cost analysis methods at different power loadings. The unit exergy cost of the shaft power decreases from 76.34 $/GJ at 75%-mode to 58.32 $/GJ at Takeoff-mode due to increasing the shaft power. The unit exergy cost of the kinetic exergy increases 599.43 $/GJ at 75%-mode to 666.76 $/GJ at Takeoff-mode because of the unit exergy cost of the exhaust gaseous with the increase in the fuel flow. The sustainability analysis indicates that the gas turbine has the highest sustainability index. Increasing the fuel flow rate raises the environmental pollutants and the environmental damage cost rate. The environmental damage cost rates of the engine are calculated to be 423.94 $/h at 75%-mode, 576.97 $/h at 100%-mode, 634.93 $/h at military-mode and 665.85 $/h at Takeoff-mode. The total cost rate consists of the sum of the fuel cost, the capital investment cost, the operating and maintenance costs, and the environmental damage cost. The total cost rates of the engine are determined to be 1702.59 $/h at 75%-mode, 2100.26 $/h at 100%-mode, 2220.42 $/h at military-mode and 2284.50 $/h at Takeoff-mode. (C) 2013 Elsevier Ltd. All rights reserved.