This report constitutes the second formal deliverable of the Preliminary Impact Assessment of communications architectures for UAS contract number EASA.2008.C20 (procedure OP.08). The report details the work that has been undertaken since the publication of the Inception report. In creating this project, EASA has initiated a process that will lead to the implementation of a regulatory policy to permit the use of UAS in non-segregated airspace. The objective of this study is to provide an initial input and guidance for the Regulatory Impact Assessment (RIA) process. This will be achieved through a Preliminary Impact Assessment on the safety and other factors that will be affected by the architecture(s) used for UAS communication systems. In the end the regulations, while protecting safety, should not over-constrain technical and business choices.