Introduction

In support of the work programme agreed upon at CAEP/7 for the Technology Task Group (TTG) of Working Group 1 (WG 1), a panel of Independent Experts (IEP) was selected and tasked with leading a review of technologies being developed for reducing aircraft community noise in the mid term (10 years) and in the long term (20 years). A formal review was held on September 29 through October 1^st, 2008, in Seattle, Washington. This review was preceded by a Noise Technology Workshop on September 26^th , 2008, which was held in conjunction with, and at the conclusion of, the CAEP Steering Group meeting in Seattle. The Noise Technology Workshop consisted of policy overview presentations by the various stakeholders attending the CAEP Steering Group meeting, and included a high-level overview of the various aircraft noise reduction technology programs being conducted in Europe, the U.S., Japan, Canada, and Russia.

WG 1, with approval of the Steering Group, selected the following members of the Noise Technology Independent Expert Panel:

Jean Beslon - France

Wajid Chishty - Canada

Philip Gliebe - USA

Dennis Huff - USA

Hirokazu Ishii - Japan

Yuri Khaletskiy - Russia

Brian J. Tester - UK

Mr. Gliebe was subsequently selected to chair the Panel, with assistance from CoChairs Dennis Huff and Brian Tester.

The Independent Experts Review consisted of detailed presentations on aircraft noise reduction, beginning with a summary of aircraft noise sources and the relative contributions of various engine and airframe-related sources to the total aircraft noise for typical aircraft designs currently in use. Presentations were given by various industry and government representatives on component noise reduction research programs, highlighting noise reduction concepts being pursued and the progress in noise reduction that has been either demonstrated or projected thus far. For the engine, component noise reduction technology status presentations were given for fan noise, jet noise, core noise, and nacelle/liner suppression. Airframe noise source reduction status was also presented, covering landing gear noise, flap and slat noise, and engine-airframe related noise sources. A presentation was also given on novel aircraft concepts, including the "Functionally Silent Aircraft."

Other presentations included material on integration of the various components of engine and aircraft noise and their potential reductions to forecast the total aircraft system community noise impact, advanced experimental diagnostic techniques for measuring noise sources, and advanced computational techniques for predicting the behaviour of engine and airframe noise sources.

This executive summary reports the key findings and conclusions arrived at by the Independent Expert Panel (IEP) as a result of assessing the information presented at the Noise Technology Workshop and the Independent Expert Review Meetings. The panel also developed a methodology for evaluating the potential benefits of various noise reduction technology concepts for various classes of aircraft. The panel key findings and conclusions were based on results generated using this methodology, as well as on panel member past experience, expertise and knowledge of the subject matter. The panel is grateful to members of ICCAIA who provided the presentation material and provided clarification answers to questions raised by the IEP. ICCAIA also graciously provided additional data on the performance of various noise reduction concepts so that the panel could better evaluate their impact on projected aircraft system noise.

The IEP presents herein their recommendations for potential aircraft noise reductions that can reasonably be expected in the mid term (10 years), and in the long term (20 years), relative to today's in-service aircraft.