We introduce UPSim (UxNB Propagation Simulator), a ray tracing-calibrated, semi-deterministic solution for spatially consistent FR3 air-to-ground propagation modeling in uncrewed aerial vehicle (UAV) networks. Instead of launching rays for every receiver position, UPSim derives deterministic visibility regions from 3D building geometry via shadow projection. It then augments these regions with line-of-sight (LOS) state-specific and altitude-aware path loss, correlated large-scale fading, and small-scale fading. Calibration and validation against FR3 ray tracing data using the global 3D-GloBFP building dataset demonstrate that UPSim accurately reproduces empirical channel distributions. Furthermore, the resulting maps support route-based analysis of channel evolution over complex urban layouts, exposing critical trajectory-level statistics such as outage distances. Consequently, UPSim offers a highly scalable, practical middle ground between computationally expensive full ray tracing and purely stochastic channel generation for mobility-aware planning and radio-map construction in aerial access scenarios.