| Abstract:In airworthiness certification practice, the noise level of the aircraft is evaluated by combining the flight noise data of the
baseline aircraft and the noise data of the derivative engine, and correcting the noise from ground noise to flight noise, so as to avoid the
uncertainty brought to tests by the complex atmospheric conditions and other factors. In order to effectively assess the airworthiness compli?
ance of the derivative aircraft, the main influencing factors leading to the difference between the engine ground and flight noise were
systematically identified, and a method of correcting the ground noise to the flight noise was established. The acoustic ray method was
adopted to eliminate the influence of atmospheric inhomogeneity on the far-field sound propagation, which improves the accuracy
compared with the traditional method treating the atmosphere as homogeneous. Based on the framework of the ICAO recommended method,
the corresponding calculation procedures for the influencing factors such as amplitude, directivity change, and sound attenuation were
established, and the effective perceived noise levels at the flyover and lateral measurement points for airworthiness noise compliance
verification under different takeoff flight trajectories were corrected with the data of ground fan noise and jet noise of the CF34-10A engine
under different operating conditions. The results show that the established correction method can utilize the engine ground static test noise
to achieve flight noise assessment. |
