Performance evaluation of Unmanned Aerial Vehicle ad hoc networks Unmanned Aerial Vehicles (UAVs) can form an ad-hoc network to communicate and cooperate with each other via wireless links. UAV ad hoc networks have the potential to provide reliable and real-time services using single-hop or multi-hop communications. However, the network topology of a UAV ad-hoc network is highly dynamic because of the fast flying UAVs that result in short lived communication links between UAVs. In mission critical applications, small delays could result in catastrophic outcomes. Thus it is required for UAVs to exchange their information as quickly as possible (with shortest possible delay). In this paper, we evaluate the performance of UAV ad hoc networks by considering the effect of network size on throughput, energy consumption and effective transmission range (total coverage range). Numerical results obtained from simulations are presented to evaluate the performance of UAV ad hoc networks. Our results show that when network size (the number of UAVs) increases, the throughput per UAV and energy consumption decrease while the total networktransmission range (effective coverage range) increases.