In addition to moving the run-up areas, the effects of using MOGAS in aircraft that are certified to use it were evaluated. Substituting an unleaded fuel has the benefit of reducing lead emissions throughout the airport footprint and reducing the overall Pb inventory. A significant number of aircraft models and engines are already certified for use with MOGAS. MOGAS use in aircraft requires low compression ratio engines, in addition to those that can operate on a lower octane rating fuel. Based on these approved aircraft, the emission inventories for each of the three airports were modified by setting Pb emissions from aircraft certified to use MOGAS to zero. Again, modeling was performed using AERMOD, with only the amount of emissions changed.
Richard Lloyd Jones Jr. Airport
Approximately 33% of the observed piston-engine landing and takeoff fleet and 45% of the activity-weighted fleet at RVS had aircraft models and engines certified to use MOGAS. The difference between the observed fleet and activity-weighted fleet fractions resulted from flight schools with certified aircraft performing multiple operations per day.
When accounting for aircraft that can use MOGAS, the maximum three-month average at RVS fell from 52 ng/m3 to 34 ng/m3, a 35% reduction. The total reduction was less than the fraction of aircraft because the aircraft certified to use MOGAS tended to have lower overall fuel consumption rates. Figure 17 shows the three-month average modeled concentrations around the RVS airport for the November–January averaging period (the period with the highest modeled three-month average concentration) for (a) the base-case scenario; and (b) the scenario using MOGAS. For this analysis, the aforementioned maintenance engine testing emissions were set to zero. In addition to reducing the maximum hotspot concentration, the replacement of AVGAS with MOGAS also significantly reduced the total area with modeled concentrations greater than 10 ng/m3.
Figure 17
Modeled Three-Month Average Concentrations from November-January at RVS
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