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30 6.1 Overview There is a single worksheet, denoted with a purple-shaded tab in the EIAT, used for selecting options for defining gasoline properties. The two aviation gasoline properties that factor into the inventory analysis are lead content and density. Worksheet 6.1 is where the option for defining aviation gasoline is selected by the user and parameter values are set. 6.2 Gasoline Parameters: Worksheet 6.1 Worksheet 6.1 is where the method and data for aviation gasoline parameters are set for the inventory analysis. Of the two fuel parameters, gasoline density exhibits little variation but gasoline lead content is variable and a key modeling assumption. There is one required action for this worksheet: the selection of the approach option for the source of the gasoline parameter data. There is an optional action to supply the gasoline param- eter data if the facility-specific approach option is selected. Please note that in this guidance method, the lead content is strictly defined as the amount of lead in gasoline and not the amount of tetraethyl lead (TEL) in gasoline, which is a different metric. Table 19 summarizes the options for gasoline parameter data; this table also appears in Work- sheet 6.1. The preferred approach is that facility-specific data be collected and entered. In the absence of this, the user must specify use of one of two screening approaches: current FAA/EPA defaults or ACRP 02-34 results. The gasoline parameters for the screening inventory options are presented in Table 20. The FAA/EPA default models lead content at the maximum allowable for 100 grade âlow leadâ (i.e., 100LL) and does not provide a citation for density (U.S. EPA 2013b). The ACRP 02-34 value is the average over the three locationsâ locally collected gasoline samples. The ACRP data show a margin with respect to the maximum of about 75 percent, but the data by location were highly variable. The FAA/EPA default assumes only 100LL gasoline used in all facilities nationally; the ACRP 02-34 project found only 100LL gasoline available at the three facilities studied. FAA survey data for 2012 show that piston engines consume predominantly, but not exclu- sively, 100LL gasoline (FAA 2013b). The national consumption data are summarized in Table 21. Grade 100 aviation gasoline has a maximum lead limit twice that of 100LL, and on-road motor gasoline (MOGAS) has no lead. Nearly all aircraft can use 100LL (Coordinating Research Council Aviation Gasoline Data C H A P T E R 6
Aviation Gasoline Data 31 2011), and some aircraft are designed to operate on a range of fuels that includes MOGAS (Rotax 2009). At the facility level, if additional grades (other than 100LL) are dispensed, then an assess- ment of the proportions of fuel dispensed would be necessary to determine the appropriate overall lead content to use in the inventory method. FAA Airport Master Record data (i.e., Form 5010) provides a listing of fuels dispensed by airport; a cursory look shows that Grade 100 gaso- line may be available in Hawaii and Utah. It is important to note that (1) TEL is present in aviation gasoline for critical performance criteria (i.e., to improve anti-knock properties) and (2) aviation gasoline is a highly refined product produced in batches (Chevron 2006). Recent Coordinating Research Council 100LL gasoline samples collected at airport fixed-based operations (89 samples covering eight refiner- ies) showed an average lead level that was 85 percent of the maximum, but the range observed included the maximum allowable limit (Coordinating Research Council 2011). Based on the available information, it is highly recommended that lead content be mod- eled based on local airport data collection due to the variability of this parameter. Data sources include (1) fuel drop certificates provided to the FBOs or (2) direct sample collection with laboratory analysis. It should be noted that data should be collected from all FBOs with different fuel suppliers, and that lead content will vary over time. In the absence of airport-specific infor- mation, the secondary recommendation is that the maximum allowable lead content be mod- eled in the EIAT. As such, the ACRP 02-34 average results are reported here (for informational purposes), but these are not recommended for use in inventory calculations. Table 19. Options for defining aviation gasoline properties. Option Title Description Screen 1 FAA/EPA Default Lead content modeled as maximum allowable; density as 2011 NEI. Screen 2 ACRP 02-34 Data Average observed in sampling at three locations as part of ACRP 02-34. Facility Specific Facility Data, User Supplied User-supplied values for lead content and density. Table 20. Gasoline parameter data for screening inventory options. Gasoline Parameter Screening Inventory Option FAA/EPA Default ACRP 02-34 Data Lead Content (g/gallon) 2.12 1.60 Gasoline Density (lb/gallon) 6.00 5.95 Table 21. National gasoline consumption by grade in piston aircraft. Gasoline Grade U.S. Consumption (Thousand Gallons) 100LL 168,232 100 15,207 MOGAS 2,440 Other gradesa 114 a Includes 91 grade aviation gasoline, which has the same maximum lead limit as 100LL. Source: FAA (2013b)
