by Nicholas P. Miller
The Transportation Research Board (TRB) recently released ACRP Document 19: Integrated Noise Model Accuracy for General Aviation Aircraft, the result of research conducted by a team of consultants led by HMMH. HMMH was retained to conduct this research project to determine the cause and recommend changes to the Integrated Noise Model (INM), which currently incorrectly computes the noise created by many of the General Aviation Jets. The study compared INM produced sound exposure levels and climb profiles with measured sound exposure levels and radar reported climb profiles. HMMH found that the INM assumed all aircraft used maximum power for takeoff, while in practice, pilots used a “derated” thrust to preserve engine life, creating lower takeoff altitudes, and generally lower levels than the INM computed. HMMH developed a method that would use the INM modeling in a realistic manner, duplicating the procedures used by pilots and are in communication with FAA to assist if possible in correcting the INM modeling. In the future, modeling would be more accurate, noise exposures realistic, and better decisions will be made about land use and aircraft noise around airports where General Aviation jets operate.