Mid-air collisions of manned rotorcrafts with Unmanned Arial Systems (UASs) or drones, are a major risk to helicopters as they may result in significant loss of human life, injuries, and property damages. The current Federal Aviation Regulation (FAR) for rotorcrafts are based on the utilization of a 1.0 kg (2.2-lb) bird only. The aim of this research is to develop a methodology which can be utilized to certify a helicopter for small UAS collision using computer-based modelling and impact analysis of the most common drone, 1.2 kg (2.7-lb) quadcopter, on the windshield of a typical helicopter. In this study, meshing of detailed CATIA geometry of a 1.2 kg DJI Phantom III UAS is done in the LS-PrePost, and then verified by simulating the free fall impact on a rigid plate and comparing the result to the vertical drop test experiment at the WSU-NIAR. The 1.0 kg (2.2-lb) and 1.8 kg (4.0-lb) drone models are also developed in the LS-PrePost using a mass scaling formulation. The Smooth Particle Hydrodynamics (SPH) technique is used to model the 1.8 kg bird and verified by simulating its impact on different aluminum plates and comparing the results with the experimental values. Similarly, the 1.0 kg and 1.2 kg bird models are created using the verified geometrical relationship. Lastly, a FE model of a single-layer acrylic windshield and helicopter is generated from the CAD geometry, on which the 1.0 kg SPH bird is numerically impacted to examine the windshield impact response. The three drone models are impacted separately on the windshield using LS-DYNA to obtain the safe thickness and the simulation results and failure damages are compared with the results from the equivalent bird strikes. The comparative study demonstrates that the damage caused by the drones are different and severer than that of the bird models. Therefore, this research proposes that hazard severity of UAS should be considered in the FAA regulations for rotorcraft components airworthiness certifications.