A surveillance system is configured to detect a rotary-wing aircraft approaching a fixed facility and provide a warning upon detection. The system includes acoustic processing nodes that receive acoustic signals from the environment surrounding the fixed facility. As the nodes receive the acoustic signals, the nodes perform a spectral analysis of the signals to detect if the source of the acoustic signals is a rotary-wing aircraft. Additionally, based upon the acoustic signals, the nodes detect an altitude of the rotary-wing aircraft and a distance between the rotary-wing aircraft and the fixed facility. In the case where the system identifies the rotary-wing aircraft as encroaching a predefined geographical area outside of the facility, based upon the altitude and distance between the rotary-wing aircraft and the facility, the system generates a warning to allow security forces to intercept the rotary-wing aircraft prior to its arrival at the facility.