9.13 General Aviation, Piston

Multiple Categories

9.13.1 Introduction

Considered in these categories are criteria pollutant emissions (particulate, organic, NOx, SOx, and CO) from general aviation aircraft piston engines during their operations at the various airports in the Bay Area.

Category Description
456 General, Piston (Livermore)
463 General, Piston (Hayward)
475 General, Piston (Oakland North)
489 General, Piston (Buchanan Field)
496 General, Piston (Gnoss Field)
503 General, Piston (Marin /Smith Ranch (Pvt))
505 General, Piston (Parrett/Angwin)
507 General, Piston (Calistoga Airpark (Pvt))
510 General, Piston (Inglenook/Napa)
511 General, Piston (Napa County)
520 General, Piston (Half Moon Bay)
527 General, Piston (San Carlos)
534 General, Piston (San Francisco International)
541 General, Piston (Palo Alto)
548 General, Piston (Reid-Hillview)
555 General, Piston (San Jose International)
562 General, Piston (South County)
593 General, Piston (Travis Aero Club)
597 General, Piston (Sonoma County)
615 General, Piston (Petaluma Sky Ranch)
619 General, Piston (Santa Rosa Air Center)
626 General, Piston (Sonoma Valley/Schelville)
632 General, Piston (Sonoma SkyPark)
1689 General, Piston (Byron)

In the piston engine, the basic element is the combustion chamber in which the mixture of fuel and air are burned, and energy is extracted by a piston and crank mechanism driving a propeller.

9.13.2 Methodology

The general aviation categories are considered an area source category since they cover facilities / emission sources that are not directly permitted by the District, and hence not systematically cataloged. Emissions for area source categories are determined using the formula:

Current Year Emissions = Base Year Emission X Growth Profile, and,

Base Year Emission = Throughput X Control Factor X Emission Factor

where,

  • throughput or activity data for applicable base year(s) is determined using a top-down approach (e.g. state-, national-level data);
  • emission factor is derived from general literature, specific literature and reports, and/or source testing results provided by Air District staff;
  • control factor (if applicable) is determined by District and state rules and regulations in effect;
  • and, historical backcasting and forecasting of emissions is based on growth profiles as outlined in the Trends section of this chapter

More details on throughput, county distribution, emission factors and controls is provided in the following subsections.

Normal flight and ground operation modes of the aircraft constitutes the landing/takeoff (LTO) cycle. For criteria pollutant emission inventory, the LTO cycle is grouped into five modes, which is equivalent to two operations in an airport activity. These include:

  1. Start-up, idle and taxi out,
  2. Takeoff,
  3. Climb out to about 2,300 feet–this height is considered the average mixing depth in the Bay Area and assumed inversion height, wherein aircraft exhaust emissions are released below it,
  4. Descent/approach from about 2,300 feet, touch down, and landing run,
  5. Taxi in, idle and shutdown

For greenhouse gas (GHG) emission inventory, in addition to LTO cycle explained above, the aircraft landing approach and climb out modes above 2,300 feet elevation and aircraft cruise mode in the District’s air space is also included.

The information on number of operations and fleet mix were obtained from the airports, the Federal Aviation Administration (FAA), and the Metropolitan Traffic Commission (MTC). Estimates of aircraft mix for each of the airports were developed based on historical activity and data on home-based aircraft.

(a) Activity Data / Throughput

The information on number of operations and fleet mix were obtained from the airports, the Federal Aviation Administration (FAA), and the Metropolitan Traffic Commission (MTC). Estimates of aircraft mix for each of the airports were developed based on historical activity and data on home-based aircraft.

(b) County Distribution / Fractions

Emissions were distributed to the county location of each airport, where SFO is in San Mateo County, OAK is in Alameda County, SJC in Santa Clara County, and to about two dozen smaller airports with piston aircraft activities in their corresponding counties.

(c) Emission Factors

The landing and take-off (LTO) cycle has its equivalent operating time-in-mode (TIM) which is the time for a particular aircraft to go through each of the five modes. Composite modal emission rates (MER) for various types of aircraft engines in general aviation use were developed based on information from the International Civil Aviation Organization (ICAO) Aircraft Engine Emissions Data Bank390, the Intergovernmental Panel on Climate Change (IPCC)391, the FAA’s Aviation Environmental Design Tool (AEDT)392, the U.S. Environmental Protection Agency (EPA) document AP-42393, and the California Air Resources Board (CARB)394.

Emission rates vary according to engine type and operating mode. Emission factors for a specific aircraft were estimated by the equation:

\[ \text{EMF} = \text{N} \times \sum{\left( v_e / v_t \right)_{m,p}} \times \text{TIM} \]

(d) Control Factors

No emission controls have been implemented by the Air District for these categories.

(e) Speciation

The ROG/TOG ratios applied to this category or this group of related categories are based on an Air District internal speciation profile. Multiple data sources have been used for developing speciation profiles, such as Air District-approved source tests, TOG speciation ratios used by other regional air quality agencies, and relevant literature including latest speciation profiles developed by CARB395 and the US Environmental Protection Agency396. For this category or group of categories, ROG constitutes 89.69% of TOG. Further assessment and improvement of ROG/ TOG speciation profiles has been planned in future inventory updates.

The PM2.5/PM and the PM10/PM ratios applied to this category or this group of related categories are based on an Air District internal speciation profile. Multiple data sources have been used for developing speciation profiles, such as Air District-approved source tests, PM speciation ratios used by other regional air quality agencies, and other relevant literature. These ratios are not necessarily consistent with the latest speciation profiles developed by CARB397 or the US Environmental Protection Agency. For this category or group of categories, PM2.5 constitutes 99.4% of total PM and PM10 constitutes 99.2% of total PM. The Air District staff routinely review speciation profiles and may update ratios as needed for improving emissions estimates.

(f) Sample Calculations

TOG emissions, given a composite EF of 0.345 lb TOG per LTO:

\[ 61,199\ \text{LTO/yr} \times 0.345\ \text{lb/LTO} \div 365\ \text{day/yr} \div \text{2000 lb/ton} = 0.028\ \text{ton/day}\ \text{TOG} \]

9.13.3 Changes in Methodology

No changes to methodology were made in this version of the base year emissions inventory.

9.13.4 Emissions

A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.

The continuing effort in aircraft improvement, development of newer engine technology and their phasing in will result in reduced emissions from general aviation sector.

9.13.6 Uncertainties

The aircraft landing and take-off (LTO) cycle emission factors can be improved if more accurate local airport data was available for the aircraft operational modes such as, Landing approach, Taxi/idle-in, Taxi/idle-out, Take-off, and Climb-out. Use of actual verses typical or standard data, such as, time in each mode and throttle settings will also help improve emission factors, therefore, an improved and accurate emissions inventory.

9.13.7 Contact

Author: Sukarn Claire

Reviewer: Ariana Husain

Last Update: November 06, 2023

9.13.8 References & Footnotes

  1. The International Civil Aviation Organization (ICAO). https://www.easa.europa.eu/domains/environment/icao-aircraft-engine-emissions-databank↩︎

  2. The Intergovernmental Panel on Climate Change (IPCC). https://www.ipcc.ch/↩︎

  3. The FAA’s Aviation Environmental Design Tool (AEDT). https://aedt.faa.gov/↩︎

  4. EPA. 1995. AP-42. Compilation of Air Pollutant Emissions Factors. < https://www.epa.gov/regulations-emissions-vehicles-and-engines/regulations-nitrogen-oxide-emissions-aircraft>↩︎

  5. The California Air Resources Board. http://ww2.arb.ca.gov/homepage↩︎

  6. CARB. 2022. ORGPROF. https://ww2.arb.ca.gov/speciation-profiles-used-carb-modeling↩︎

  7. U.S. EPA. 2022. SPECIATE. https://www.epa.gov/air-emissions-modeling/speciate↩︎

  8. CARB. 2022. PMSIZE. https://ww2.arb.ca.gov/speciation-profiles-used-carb-modeling↩︎

  9. Metropolitan Transportation Commission (MTC) Publications. https://mtc.ca.gov/tools-resources/mtcabag-library↩︎