Flight Test Methodology for Verification of Precipitation Static Protection in Civil Aircraft Radio Navigation Systems

The verification of Precipitation static (P-static) protection for the radio navigation system of civil aircraft is a critical test item for airworthiness certification. However, determining the presence of P-Static on the aircraft fuselage and assessing whether its discharge interferes with the radio navigation system remains challenging, with testing methods still under exploration. By analyzing airworthiness certification test provisions, the necessity of conducting flight tests for P-static protection verification of the radio navigation system was clarified. Based on existing conditions for civil aircraft flight tests, a comprehensive flight test method was proposed to verify the P-satic protection capability of the radio navigation system. This method includes determining external meteorological conditions, measuring electrostatic parameters, and designing aircraft maneuvers and states. The test plan was validated on a test aircraft. Discharge current data measured on a discharger indicates that during the flight of a civil aircraft through cirrus clouds, negative charge accumulated on the aircraft's surface, leading to electrostatic discharge. The maximum peak discharge current recorded was 330 μA. P-satic radiation field data were obtained near the Automatic Direction Finder (ADF) antenna; the radiation energy is primarily concentrated within the 200 MHz range, with some energy distribution still observed between 200 MHz and 500 MHz. Within the 200 MHz range, the signal amplitude exceeds the background noise, and stable peaks appear at multiple frequency points, with the maximum amplitude reaching up to 50 dBm.confirming the presence of a P-Static environment. This achieved the objective of evaluating the functional performance of the radio navigation system in an electrostatic environment, providing technical support for P-Static protection verification flight tests and offering a reference for the practical application of electrostatic protection design.