Method for estimating aircraft noise corresponding to changes in thrust and speed during start of takeoff roll

In aircraft noise calculation by international guidelines such as ICAO Doc.9911, NPD (Noise Power Distance) data that relates aircraft thrust and noise are used. In these guidelines net-thrust use as power in NPD data. However, net-thrust of an aircraft engine cannot be measured directly. Therefore, net-thrust has to be estimated using the conversion equation with engine parameters such as N1% RPM and EPR, as well as speed. Meanwhile, for recent aircraft types, the coefficients for the N1% and speed terms of the conversion equation are not available. For this reason, Japanese aircraft noise models use N1% and EPR directly in place of net-thrust to create NPD. These parameters change the most at the start of the takeoff roll, and it is necessary to confirm the validity of the noise calculation in this area. In this study, noise measurements at the side of the runway and aircraft onboard data were analyzed to investigate an alternative method of estimating noise changes to net-thrust. The result shows that it is reasonable to correct the noise according to the speed change in addition to the noise calculation in the section of lower speed state of takeoff roll.