Recent increases in fuel prices have driven the commercial aviation industry to focus on fuel efficiency. The efficiency of propellers and prop-fans has produced renewed interest in advanced “open rotor” engine designs. To contribute to the design process, noise predictions need to accurately identify the issues associated with these new designs and must forecast the annoyance of the population near airports due to the new noise sources. Spectra from propeller designs are typically dominated by tones at harmonics of the blade passage frequency, whereas turbofans generate much smoother spectra. Disagreement already exists regarding the need for tone corrections for turbofans, with certification noise levels including a tone correction and community noise contours not including one through the use of Day-Night Level (DNL). A tone-corrected DNL (DNLT) is presented and compared to alternative metrics, including those with and without tone and duration corrections, for turbofan, turbo-prop, and open rotor engines. The compatibility of DNLT with existing DNL contours will be demonstrated, as well as the predictive capability of the certification points with respect to various contour metrics. The results will show the variance between the contours from the different metrics as well as the need for regulatory bodies to consider the potential for increased annoyance above that predicted by DNL. In addition, the applicability of the identified metrics within the FAA’s Aviation Environmental Design Tool will be addressed.

ANTICIPATED OUTCOME

An assessment of a large set of metrics will be produced for turbofan and open rotor engines. The variation between metrics will be used to quantify the impact of metric selection for each engine architecture.

PARTICIPATING UNIVERSITY

Georgia Institute of Technology

LEAD INVESTIGATOR

Jimmy Tai, School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0150 jimmy.tai@aerospace.gatech.edu

PROJECT MANAGER

Natalia Sizov, natalia.sizov@faa.gov

REPORTS

• Open Rotor Noise Impact on Airport Communities. Dimitri Mavris, Jimmy Tai, Russell Young, Ben Havrilesko. Project 35 final report. July 2011, Report No. PARTNER-COE-2011-007. Download (pdf 4.2MB)