In June 2001, following the fifth meeting of the Committee on Aviation Environmental Protection (CAEP/5), the Council of ICAO adopted a new ‘Chapter 4’ noise standard, which is more stringent than the current ‘Chapter 3’ standard.
In order for an aircraft to qualify for the Chapter 4 standard, the following criteria must be met as a minimum:
- The relevant Chapter 3 noise limit at each certification point (flyover, sideline or approach) must not be exceeded, i.e. no trade-offs between points are permitted;
- Relative to the Chapter 3 standard, the minimum margin at any two certification points must be at least 2 EPNdB;
- Relative to the Chapter 3 standard, the cumulative margin at the three certification points must be at least 10 EPNdB.
From 1 January 2006, the Chapter 4 standard applies to newly certificated aircraft, although manufacturers may also opt to re-certificate some of their existing Chapter 3 designs to the Chapter 4 standard.