A 3D computer model named AIPAC (Aircraft Ice Protection Analysis Code) suitable for thermal ice protection system parametric studies has been developed. It was derived from HASPAC, which is a 2D anti-icing model developed at Wichita State University in 2010. AIPAC is based on the finite volumes method and, similarly to HASPAC, combines a commercial Navier-Stokes flow solver with a Messinger model based thermodynamic analysis that applies internal and external flow heat transfer coefficients, pressure distribution, wall shear stress and water catch to compute wing leading edge skin temperatures, thin water flow distribution, and the location, extent and rate of icing. In addition, AIPAC was built using a transient formulation for the airfoil wall and with the capability of extruding a 3D surface grid into a volumetric grid so that a layer of ice can be added to the computational domain. Currently, the grid extrusion capability is used in AIPAC for the so called one-shot ice shape computation. The icing tunnel data used in the validation of the proposed computer model were obtained at the NASA Icing Research Tunnel using a range of in-flight icing conditions and bleed air system mass flows and hot air temperatures. Predicted leading edge skin temperatures and runback ice location are compared to the experimental data. Correlation between experiment and analysis was good for most of the test cases used to assess the performance of the simulation model. AIPAC's transient formulation will also allow future development of a thermodynamic model for the simulation of electro-thermal de-icing systems.