Prediction of Engine Casing Temperature of Combat Aircraft for various operating conditions needs modeling of convective and radiative heat flow from the jet pipe to the casing. Radiation modeling which implies modeling of multiple reflections and scattering is done here by the radiance-irradiance approach. The engine layout is approximated by three co-axial cylinders and axially discretized. The shape factors (which account for the directional dependence of radiation heat flow) for various configurations needed in radiation modeling are analytically obtained by a sequence of shape factor algebra from standard configurations. The resulting non-linear algebraic equations of combined convection and radiation heat flow are solved by an iterative technique to give the engine casing temperatures which may be used for infrared signature studies.