Brown Field Municipal Airport Land Use Compatibility Plan

APPENDIX CAIRPORT LAND USE COMPATIBILITY CONCEPTSCompatibility ObjectiveIn an idealistic sense, the compatibility objective with respect to aircraft overflight is the same as fornoise: avoid new land use development that would be disrupted by overflight activity and lead toannoyance and complaints. However, given the extensive geographic area subject to overflights, thisobjective is unrealistic except relatively close to the airport. A more realistic objective of overflightcompatibility policies, therefore, is to help notify people about the presence of aircraft overflights nearairports so that they can make more informed decisions regarding acquisition or lease of property in theaffected areas.MeasurementCumulative noise metrics, such as CNEL, Day-Night Average Sound Level (DNL), or Equivalent SoundLevel (Leq), are well-suited for use in establishing land use compatibility policy criteria and are the onlynoise metrics for which widely accepted standards have been adopted. However, these metrics are notvery helpful in determining the extent of overflight impact areas. Locations where overflight concernsmay be significant are typically well beyond where noise contours can be drawn with precision. Flighttracks tend to be quite divergent and noise monitoring data are seldom available. Moreover, even if thecontours could be drawn precisely, the noise levels indicated by such contours may not be much abovethe ambient noise levels.For the purposes of airport land use compatibility planning, two other forms of noise exposureinformation are more useful. One form is the momentary, maximum sound level (L max ) experienced onthe ground as the aircraft flies overhead while landing at and taking off from a runway. These noiselevels can be depicted in the form of a noise “footprint”, as shown on Exhibits C-3 and C-4 for a varietyof air carrier and general aviation aircraft. Each of these footprints is broadly representative of thoseproduced by other aircraft types similar to those shown. The actual sound level produced by any singleaircraft takeoff or landing will vary not only among specific makes and models of aircraft, but also fromone operation to another of identical aircraft.In examining the noise footprints, two additional points are important to note. One is the importance ofthe outermost contour. This noise level (65 dBA L max ) is the level at which interference with speechbegins to be significant. Land uses anywhere within the noise footprint of a given aircraft operationwould experience noise, even if only briefly, that could be disruptive to outdoor conversation. Indoors,with windows closed, the aircraft noise level would have to be at least 20 dBA louder to result in similareffects.C–22Brown Field Municipal Airport Land Use Compatibility PlanJanuary 25, 2010