Both civil and military HF applications are now demanding improved reliability and availability, higher throughput and reduced operator workload. In order to meet these demands, automation is clearly the way forward. The specification for an automatic radio control system (ARCS) is currently under development within NATO. The intention is for this system to improve the availability of communications, whilst reducing the reliance on experienced HF radio operators. Computer simulation is playing a key role in the derivation of optimum protocols for ARCS, which is a critical process in the specification of the system. Many different protocols and network management techniques can be evaluated under identical conditions to determine their impact on the network performance. The performance data provided by these simulations can then be used to guide the design of ARCS. This paper describes the ARCS network simulator, a computer model which has been designed to simulate ARCS networks to allow the investigation of timing issues due to different protocols and network loads. The construction of this model is described. However, the main aim of this paper is to describe the results from several simulated networks, and the conclusions that can be reached concerning the way forward for ARCS.