CHAPTER 3 CHAPTER 3 Airport Noise Control
3.5 Noise Certification
the visual approach slope indicator system (VASIS) to avoid unnecessary low flying.
• Performing the final descent at a steeper than normal angle. Descents of 4 degrees have been used, but 3 degrees is a more normal angle.
• Two-segment approaches with the initial descent at 5 or 6 degrees of flaring to 3 degrees for the final approach and touchdown.
• Low-grade approaches with reduced flap settings and lower engine power settings demonstrate some reduction of noise. Reducing flap settings on the B737 from the normal 30 degrees reduces the noise by 2 EPNdB.
• Use of continuous-descent approaches employing secondary surveillance radar for height information. This prevents the use of power in a stepped descent and consequently reduces noise under some parts of the descent path. A combination of low-power and low-drag approach procedures has been used in the past with
considerable success at Frankfurt Airport, which has severe environmental noise problems owing to its position within an urban area.
Runway Operations
The most significant improvement in noise impact that can be achieved when aircraft are on runways is control of the use of thrust reversal. Although thrust reversal is usually about 10-dB below takeoff noise, it is an abrupt noise that occurs with little warning. Aircraft operations should be restrained from the use of thrust reversal on noise-nuisance grounds, except in cases where no other adequate means of necessary deceleration is available or where the airport setting does not require noise-control strategies.
Insulation and Land Purchase
Some relief to noise nuisance can be attained by the use of sound insulation. In some countries, those adversely affected by defined levels of noise nuisance are eligible for governmental or airport authority grants that must be used for double glazing or other sound-insulation procedures. Schemes of this nature operate, for example, in the noise- impacted areas around London Heathrow and Schiphol Amsterdam.
A more direct, although more expensive, method of reducing noise nuisance was adopted at LAX, where many homes and businesses in the immediate vicinity of the airport were purchased by the airport through mandatory purchasing procedures (eminent domain). In some cases, this type of action is the only recourse open to an airport when continued operation means intolerable living and working conditions for the neighboring population.
The first generation of jet-powered commercial aircraft predated Annex 16 and early versions of the FAR. Such aircraft therefore were not covered by ICAO and the FAR, and airplanes such as the Boeing 707 and the DC-8 were designated as “non-noise-certificated (NNC).” The first standards for aircraft designed before 1977 were included in Chapter 2 of Annex 16, and airplanes such as the Boeing 727 and the Douglas DC-9 were designated as “Chapter 2 aircraft.” In the parallel FAR, these were Stage 2 aircraft. Newer equipment was required to meet the improved standards on noise emission embodied in the later Chapter 3 (Stage 3) regulations. Examples of Chapter 3 aircraft are the Boeing 767 and the Airbus 319 (ICAO 2008a).
In order to reduce the noise nuisance from aircraft, the ICAO regulations have become more stringent over time, ensuring that fleets of older, noisier aircraft have been phased out and replaced with new air transport aircraft that are considerably quieter than similarly sized equipment of 50 years ago. Over time, aircraft have been required to conform to the increasingly more severe requirements by the periodic issuance of Chapter 2, Chapter 3, a n d Chapter 4 regulations; these have been promulgated by ICAO after international discussions and agreements (ICAO 2008a). Parallel regulations are the Stage 2, Stage 3, and Stage 4 modifications to the FAR in the United States (FAA 2012).
ICAO and FAA certification standards principally relate to the noise generated by an aircraft on approach and while on the runway and on flyover. The form of these standards is shown in Figures 3.6 and 3.7. Three noise-measurement points are defined under the approach and takeoff paths and laterally to the side of the runway. Maximum noise levels are set at these reference noise-measurement points; permitted noise levels are set to be dependent on maximum certificated takeoff weights, with the rationale that small, very noisy aircraft are socially undesirable and therefore should not be certificated. There are absolute maximum noise limits for even the largest aircraft. When examining Figure 3.6, it can be seen that an aircraft with noise characteristics plotting above or to the left of the curves is acceptable; those with plots to the right or below the curve fail to meet certification standards. The FAR are now identical to ICAO regulations. Figure 3.7 shows the location of the noise-measurement points.
FIGURE 3.6 Aircraft noise certification limits. (Sources: FAA, ICAO.)
FIGURE 3.7 Location of noise-measurement points. (Sources: FAA, ICAO.)
In October 2001, the ICAO plenary meeting adopted a new and stricter Chapter 4 standard. This banned Chapter 2 aircraft from operating in major aviation states after April 1, 2002. Starting on January 1, 2006, newly certificated airplanes were required to meet Chapter 4 noise standards, as were Chapter 3 airplanes for which recertification to Chapter 4 was requested. The principal differences in requirements include
• A cumulative 10-dB over Chapter 3 levels
• The sum of the improvements at two measurement points to be at least 2 dB
• No tradeoffs permitted
• Standards for certification only not for new operational restrictions such as phaseouts
• Specific exemptions for new operating restrictions for developing countries
For general reference purposes, Table 3.1 shows the noise levels generated by a number of certificated aircraft in general usage in 2012 (FAA 2010).
Source: FAA AC36-3H.
TABLE 3.1 Measured Aircraft Noise Levels