Options for Reducing Lead Emissions from Piston-Engine Aircraft (2021) / Chapter Skim
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The number "100" refers to 100LL's octane rating and "LL" stands for "low lead." Lead is added in the form of tetraethyl lead to 100LL to achieve the octane rating needed for the safe operation of high-performance aircraft with high-compression engines, which account for about one-third of the fleet and an even larger percentage of fleet fuel consumption. Because 100LL can be used by all kinds of pistonengine aircraft, this single grade is the only type of fuel consistently available to GA aircraft operators.
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From page 2... ...
existing non-leaded fuel alternatives to avgas used by piston-engine general aviation aircraft, and (c) mitigation measures to reduce ambient lead concentrations, including increasing the size of run-up areas, relocating run-up areas, imposing restrictions on aircraft using avgas, and increasing the use of motor gasoline.
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From page 3... ...
EXISTING UNLEADED FUEL ALTERNATIVES The only specified and available unleaded avgas, UL94, has the potential to be used in about half to two-thirds of existing piston-engine aircraft, although these are generally the lower-performance aircraft that account for less fuel burn and flight hours. Aircraft would need to acquire FAA certification approvals to use UL94, which many newly produced aircraft do not have.
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From page 4... ...
Although it was not feasible to assess the ramifications on the industry, it is the judgment of the committee that restricting the use of this large and important component of the GA fleet would not be a viable mitigation. By comparison, restrictions on the fuel used by piston-engine aircraft, such as requirements for the use of UL94 by some or all low-performance aircraft that do not need to use high octane fuel, would require that substantial numbers of airports establish the requisite fuel storage and dispensing capacity to sufficiently ensure the unleaded fuel's widespread availability such that aircraft operators could be confident that the fuel will be available along their routes of flight.
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From page 5... ...
Hence, assessing whether changing the location of run-up areas will achieve appreciable benefits in mitigating hot spots for ambient lead concentrations requires detailed information on specific conditions at individual airports, and particularly those that have moderate to high traffic activity, which number in the hundreds or more. A MULTI-PATHWAY APPROACH FOR MITIGATING AVIATION LEAD Achieving continuing, and potentially full, reduction of lead from aviation is a challenge for which there is currently no single known technical solution that is certain to be available in the near term.
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From page 6... ...
Some mitigations would confer ancillary benefits that would justify their pursuit, even where the lead reductions could be relatively modest, such as increasing awareness in the aviation industry about the degree of lead exposure that aviation causes to encourage widespread change. Pursuing them together would account collectively for reduced lead in aviation, and would increase the probability of significant technical breakthroughs sufficient to achieve the ultimate goal of no leaded avgas.
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From page 7... ...
Timeframe for lead Near-term Near-term Near- to mid-term Mid-term Far-term for ap- Unknown; may Far-term; pace of reduction benefits if preciable reduc- require technical reduction depends started soon tions and will breakthrough on cost, rate of require technical innovation, and advances extent of applicabil ity to GA fleet Focus of implemen- Airport manage- FAA flight Fuel supply chain, Fuel supply chain Engine and air- Fuel supply chain, Technology detation ment standards, especially refiners and airports, craft makers especially fuel velopers, aircraft pilot instruction especially fuel developers and manufacturers, and and training storage and dis- engine and aircraft aircraft owners programs, GA pensing capacity makers community Possible policy ac- Provide data and Provide training Directives and/or Incentives and fi- Directives and/ Public–private R&D support, tions for facilitating tools for analysis and education incentives, perhaps nancial assistance or incentives collaborative FAA certification, implementation and identify- materials; en- focused on refiners for airports to applicable to GA (PAFI-like) for and incentives for ing operations gage in aware- add fueling ca- industry R&D, testing, and aircraft owners to changes ness campaigns pacity; eased FAA certification incur expense certification 7 continued
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Main sources of Variability in Potential to af- Refiner capacity to Feasibility of Ability to design Potential to meet Rate of innovauncertainty in airport-specific fect practices meet tighter lead adding fuel sup- suitable engines fuel performance tion, certification achieving effective factors specifications ply chain (refiners for all high- requirements challenge, cost, and implementation and airports) ; performance owner interest certification aircraft Ancillary benefits Greater lead Greater lead Environmental Changes in poland concerns awareness and awareness and and health impacts lutants, including interest in lead- interest in lead- related to other greenhouse gases free fuels and free fuels and fuel components over life cycle propulsion propulsion NOTE: 100VLL = 100 octane very low lead aviation gasoline; FAA = Federal Aviation Administration; GA = general aviation; PAFI = Piston Aviation Fuels Initiative; R&D = research and development; UL = unleaded.
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From page 9... ...
Pilots and aircraft owners, airport managers and personnel, and aircraft technicians would understand the hazards created by leaded avgas to themselves and the local community, and would follow best practices for containment during refueling, locating and timing engine runups, proper disposal of inspected fuel samples, and exposure protections. Airports would purposefully move pre-takeoff run-up areas to reduce the proximity of lead concentration hot spots to people where airport location, traffic activity levels, and exhaust interactions warrant such a response.
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From page 10... ...
The fuel would be made available at many high- and mediumvolume airports where supplemental fuel storage and dispensing capacity exists or can be economically added. This development has the potential to result in lead reductions that could exceed 40 percent when combined with 100VLL being used by legacy high-performance aircraft, although this full reduction may not be achieved due to expected limits on the availability of an unleaded grade at many lightly used airports where the cost of adding more fueling capacity may be prohibitive.
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From page 11... ...
In parallel, within a decade or so, all newly produced gasoline-powered aircraft, including high-performance aircraft, would be certified to use an unleaded avgas grade, which may need to be a lower octane grade if a safe unleaded drop-in replacement for current 100LL is not established in time. Aircraft operators could choose to transition their aircraft systems to use this fuel once it is sufficiently available along their routes of flight and at their home base airports.
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From page 12... ...
It will be important that the transition to using avgas with lower or no lead content also coordinate with efforts seeking to reduce or eliminate GHG emissions, given the shared concerns with developing and certifying new aircraft technology, the supply and distribution systems for GA aircraft fuels, and broad awareness within the GA community. ONGOING NEED FOR RESEARCH, DATA, AND ANALYSIS While ample evidence and knowledge exist about the harm caused by lead pollution to highlight the need to initiate a comprehensive set of aviation lead mitigations now, there also remains a compelling need for more research and data to inform the design and assessment of mitigations and to target them in the most effective manner.
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From page 13... ...
should conduct more targeted monitoring and enhanced computational modeling of airborne lead concentra tions at airports of potential concern, as indicated by its most recent screening study, to evaluate aircraft operations that are main contributors to lead hot spots and designing airport-specific mitigation measures. In addition to airports found to have airborne lead concentrations exceeding the concentration of the lead National Ambient Air Quality Standards (NAAQS)
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From page 14... ...
14 OPTIONS FOR REDUCING LEAD EMISSIONS FROM PISTON-ENGINE AIRCRAFT A key message of this report is that a lead mitigation strategy focused almost entirely on developing an unleaded drop-in fuel that would eliminate aviation lead emissions has a high degree of uncertainty of success given the formidable technical challenges. Additional mitigation measures are available that could be applied in the near- and mid-term to make progress in reducing lead emissions and exposures while other approaches having the potential for much larger impacts are being pursued.
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