Impulse Radio Ultra Wide Band (IR-UWB) is a promising technology to address Wireless Sensor Network (WSN) constraints such as low power consumption. Existing network simulation tools do not provide a complete WSN simulation architecture, with the IR-UWB specificities at the PHYsical (PHY) and the Medium Access Control (MAC) layers. In this paper, we propose a WSN simulator based on the IR-UWB technique and taking into account the application specificities depending on the channel propagation characteristics. The main application addressed in this paper is the Structure Health Monitoring for aircrafts. Electromagnetic simulations of the real channel propagation inside the aircraft are done and the obtained channel propagation model is introduced in the WSN simulator for a very good accuracy. This WSN simulator allows to establish the best network topology, under the constraints of an application, even for very high number of wireless sensor nodes.