Mon 9 July 2012 – The United States Environmental Protection Agency (EPA) has adopted new oxides of nitrogen (NOx) emissions standards for aircraft engines with rated thrusts greater than 26.7 kilonewtons (kN), which primarily power commercial passenger and cargo aircraft. Specifically, the EPA is adopting two new tiers of more stringent NOx emission standards to bring the United States into line with standards approved by ICAO. NOx is an important precursor gas in the formation of tropospheric ozone and also secondary particulate matter, which are common air pollutants in urban areas where airports are located. The EPA has also been under strong pressure for some years by environmentalists to rule on leaded avgas fuel used in small piston aircraft on public health grounds and the FAA has announced it is planning the transition from leaded to unleaded fuel for most of the US general aviation fleet by 2018.
The new NOx rule is being implemented under the US Clean Air Act, which directs the EPA Administrator to “propose aircraft engine emission standards applicable to the emission of any air pollutant from classes of aircraft engines which in her judgement causes or contributes to air pollution that may reasonably be anticipated to endanger public health or welfare.”
According the EPA, around 154 million people in the United States live in designated so-called nonattainment areas and the new rule will allow it to enforce the ICAO emission standards adopted by ICAO, and will be useful to states in attaining the ozone, particulates and nitrogen dioxide standards established under the National Ambient Air Quality Standards.
Specifically, the EPA is adopting two new tiers of more stringent NOx standards, referred to as Tier 6 (or CAEP/6) and Tier 8 (or CAEP/8). The standards will apply differently depending on the date the engine model received its original type certificate.
Engine models that were originally certificated prior to the effective date of the rule – 18 July 2012 – may continue production without meeting Tier 6 standards, which are around a 12% reduction in emission levels from the current Tier 4 standards, until 31 December 2012. This delay in complying with the Tier 6 standards for previously certificated engine models is intended to allow for an orderly transition. Engine models certified after 1 January 2014 must comply with Tier 8 standards, which represent a 15% reduction from Tier 6 levels.
Tier 6 levels were actually adopted by ICAO in 2005 with an implementation date in 2008, and Tier 8 standards adopted by ICAO in 2008 to take effect in 2014.
The EPA is also adopting several additional changes that would affect all aircraft gas turbine engines that are subject to current emission requirements. The agency is clarifying when a design variation of a previously certified engine model causes the emission characteristics of the new version to become different enough from its parent engine that it must conform to the most current emissions standards. The EPA is also amending the emission measurement procedures. In addition, the EPA is requiring all gas turbine and turboprop engine manufacturers that are subject to exhaust emission standards to report to the EPA emission data and “other information necessary for the purpose of conducting emission analyses and developing appropriate public policy for the aviation sector”.
The EPA has faced heavy criticism from environmental groups over perceived non-action to deal with the health effects caused by lead in general aviation (GA) aviation gasoline (avgas). Friends of the Earth (FOE) first petitioned the EPA to act in 2006 and having failed to secure an adequate response from the agency took out a lawsuit in March.
According to the EPA’s own estimates, 16 million people reside and 3 million children attend schools in close proximity to the 22,000 airports in the US where leaded avgas may be used. Findings by the EPA have shown that 16 areas in the United States were in violation of airborne lead standards and that the fuel, known as avgas or 100LL (100 octane low lead), was now the largest source of airborne lead emissions in the country.
“The EPA has repeatedly concluded that lead is extremely toxic to humans, wildlife and the environment, and causes health effects even at low doses,” said Marcie Keever, FOE’s Legal Director, in March. “The EPA’s continuing failure to do what the law [the Clean Air Act] requires and address this pollution leaves us no choice but to take this critical public health issue to the courts. The health of airport workers, pilots, passengers and surrounding communities from continued exposure to leaded aviation gasoline hangs in the balance.”
Although lead was phased out of car gasoline use over 15 years ago in the United States, the move is not quite as simple for piston engine manufacturers, which claim that removing lead completely from avgas was technically “formidable”. However, the GA industry said in 2010 that it was “aggressively working to further reduce the lead content of avgas, by an additional 20% from the already low 100LL standard.”
Unveiling a report two weeks ago, the FAA committed to developing “a fiscally responsible action plan” to meet its goal of making an unleaded fuel available for most of the GA fleet to replace 100 octane low-lead (100LL) by 2018.
The FAA said it was considering recommendations contained in a final report by the Unleaded Avgas Transition Aviation Rulemaking Committee, which summarised the key issues the GA faces in the development and deployment of an unleaded avgas.
Noted the committee: “A drop-in unleaded replacement fuel that can be seamlessly deployed for the existing fleet of aircraft is not currently available and may not be technically feasible. The industry needs a programme to conduct fleet-wide evaluation, certification and deployment of replacement avgas. Since the current fuel, 100LL avgas, is widely available, there are no market driven reasons to introduce a new fuel.”
The committee found that the effort to test new fuels would cost the FAA around $57.5 million over the next 11 years.
However, the report has recommended, which the FAA has accepted, implementing an action plan, involving the FAA, EPA and industry, which covers tasks, costs and timing in developing unleaded avgas. The FAA says it has started the initial R&D work at the FAA Technical Center and has hired a transition consultant to start forming an industry-government collaborative organisation.
In the meantime, a group of sport aviators have come together in the United States to form the Aviation Fuel Club, which offers members access to aviation-standard Sport Fuel 91+ octane, ethanol-free, unleaded gasoline at smaller airports across the country.
The EPA, which has been regulating on aircraft engine emissions since 1973, is also facing action from environmental groups over greenhouse gas emissions such as CO2, which the agency has so far resisted from taking a decision on rulemaking (see article).
EPA – NOx emissions standards
FAA – Avgas committee report
Friends of the Earth
Aviation Fuel Club
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