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124 Aircraft Noise: A Toolkit for Managing Community Expectations the last decade. The action may also require preparation of environmental documentation if the changes result in new or increased impacts within a 65 DNL contour. Example of Technique for Public Information: Comparative Noise Exposure of a Single Straight-out Departure Against Three Divergent Departure Routes (166) 8-3 Example of Alternative Flight Tracks Video (prepared for ACRP 02-05 project) 8-4 Take Off Thrust and Flap Management Procedures Purpose: This strategy utilizes specifically designed departure climb procedures to minimize noise impacts over communities. The FAA has issued Advisory Circular 91-53A, Noise Abate- ment Departure Profile, which specifically outlines power setting and flap management tech- niques for aircraft to minimize noise for communities located either "close-in" to, or "distant" from, the airport. The National Business Aircraft Association has also designed a set of proce- dures to be used by general aviation jet aircraft. Close-in procedures are designed to reduce the noise levels over land uses close to the takeoff end of the runway by providing thrust cutbacks during climb between 1000 and 3000 feet altitude. Distant procedures provide for a thrust cut- back at a greater distance from the airport with consequent reduction of noise levels beyond 18,000 feet from the runway end. ICAO has established similar procedures. Limitations: Airlines have adopted different definitions of these procedures for their own use. Any measure that varies from the airlines standard "close-in" or "distant" procedures requires special approval from the FAA. Airlines may request carriers to use the measure that is most appropriate to the need at the airport, but it is the pilot and carrier who actually implement the measure in flight. Implemented by: Airlines/operators with guidance from airports and FAA. Public reaction: The selection of a "close-in" or "distant" departure procedure is typically transparent to the person on the ground. The noise levels generated by Stage 3 aircraft do not vary by many decibels and the location of the variance differs by aircraft type and procedure. Con- sequently, it is virtually impossible for a layman on the ground to identify what aircraft is using what procedure. Example of Technique for Public Information: Comparative Noise Footprint of the MD-83 Using Close-in or Distant Departure Climb Profiles (167) 8-5 FAA Advisory Circular 91-53A, Noise Abatement Departure Profile (168) 8-6 NBAA material on its noise abatement program, including quiet climb and descent proce- dures at (169) Approach Thrust and Flap Management Procedures Purpose: This strategy utilizes specifically designed profiles to minimize noise impacts over communities. These may take the form of flap and thrust management during descent, the development of intercept altitudes that assure that aircraft turn onto final approach courses at points farther away and at higher altitudes that have been previously used, or the use of Verti- cal Navigation courses that set descent and level segments to minimize the noise produced over populated areas. The NBAA has included information on quiet flying during approach proce-