Experimental study on aircraft landing gear noise

An experimental investigation on aircraft landing gear noise is presented. The study includes systematic testing and data analysis using a full-scale Boeing 737 landing gear. The database covers a range of mean flow Mach numbers typical of landing conditions for commercial aircraft and various landing gear configurations, ranging from a fully dressed, complete gear to cleaner configurations involving only some parts of the complete gear. This enables the examination of noise radiation from various groups of the gear assembly and the derivation of functional dependencies of the radiated noise on the How Mach number at various far-field directivity angles and on various gear geometry parameters. It is shown that the noise spectrum can be decomposed into three frequency components, namely, the low-, mid-, and high-frequency components, respectively, representing contributions from the wheels, the main struts, and the small details such as hoses, wires, cutouts, and steps. It is found that these different frequency components have different dependencies on flow parameters and gear geometry. Based on the spectral decomposition in the three frequency domains, normalized spectra are derived for all three components and a model for the overall sound levels is developed as a function of flow and geometry parameters.