Experimental and numerical study is carried out to quantify the accretion growth resulting from ice crystal icing (ICI) on a heatable NACA0012 model. Experiments are performed in the Braunschweig icing wind tunnel encompassing extensive variation of influential parameters such as the supplied heat flux, ice water content, flow velocity, tunnel wet bulb temperature and angle of attack of the test article. Investigations reveal that accretion severity tends to increase for positive wet bulb temperature and the time required for accretion inception reduces with increasing ice water content. Increase in flow velocity tends to have an eroding effect on the accreting ice layer, with accretion shapes shifting from mushroom to conical under the influence of aerodynamic stresses. For negative wet bulb temperatures, increase in supplied heat flux for higher ice water content tends to result in higher accretion growth rates. For constant ice water content and increasing heat flux the cooling power generated from icing cloud is insufficient and takes longer to overcome high temperature gradients resulting in longer accretion inception time. Lastly, upon increasing the angle of attack of the model, the stagnation point shifts to allow for lower tangential aerodynamic stresses on accreted ice layer which leads to increase in icing severity. Experimental results are used to calibrate and validate the numerical models developed at ONERA. The simulations are performed in a two dimensional framework. The unsteady accretion solver is based on an enthalpy approach. An empirical model is used to compute the sticking efficiency. Concerning the phenomenon of erosion, it is taken into account using previously derived models. A heat conduction solver is used to simulate the unsteady thermal behavior of the NACA0012 airfoil. Both solvers are coupled thanks to a Robin-Robin Schwarz method. Initial comparison of accretion growth rates and time of accretion initiation shows good agreement across a wide range of parametric variation.