A diffusing S-duct aircraft intake system is computationally studied for the effects of inlet icing and wall heat transfer on engine face distortion. A Reynolds-Averaged Navier-Stokes (RANS) code with k-ω SST turbulence model is used to simulate the compressible viscous flow in the duct. The glaze ice accretion on the inlet lip is simulated as a fixed protrusion from NASA LEWICE3D code. The shape and size of the ice on the inlet lip are assumed to remain constant even in the case of the heated wall. The case of zero external heat transfer is modeled by the adiabatic wall boundary condition, and constant-wall temperature is used to simulate the heated wall effect. The freestream Mach number of 0 . 85 and glaze ice condition on the inlet lip produce massive flow separation at the lip and internal shock cell structure in the S-duct. The heated wall creates additional vorticity and thus increases the engine face distortion level. The areaaveraged total pressure distortion at the engine face in a freestream Mach number of 0 . 85 is increased by ~7% in the heated wall case as compared to the adiabatic flow. NOMENCLATURE DCtotal pressure distortion coefficient, defined in Equation (5) DP total pressure distortion parameter, defined in Equation (4) LWC liquid water content, g/m 3