Section 231 of the Clean Air Act (CAA) directs the EPA Administrator to ``issue proposed emission standards applicable to the emission of any air pollutant from any class or classes of aircraft or aircraft engines which in his judgment causes, or contributes to, air pollution which may reasonably be anticipated to endanger public health or welfare'' (42 U.S.C. 7571(a)(2)). Under this authority EPA has conducted several rulemakings establishing emission standards and related requirements for several classes (commercial and general aviation engines) of aircraft and aircraft engines.In 1973, EPA promulgated emission regulations for vented fuel, smoke, and exhaust (HC, NOX, and CO) emissions (38 FR 19088, July 17, 1973). Three tiers of standards were promulgated: retrofit standards for in-use engines, standards[[Page 25357]]for newly manufactured engines (those engines built after the effective date of the regulations) and for newly certified engines (those engines designed and certified after the effective date of the regulations). On August 16, 1976 (41 FR 34722) EPA promulgated emission standards for supersonic aircraft engines. On January 7, 1980 (45 FR 1419), EPA rescinded all gaseous emission requirements for piston engines (P1) and auxiliary power units (APU). On December 30, 1982 (47 FR 58462) EPA revisited aircraft engine emissions and amended regulations as follows: (1) Withdrew HC, CO, and NOX emission standards for gas turbine engines used only for general aviation applications, for aircraft gas turbine engines of rated thrust less than 26.7 kN, and for newly certified aircraft gas turbine engines (i.e., engine models produced for the first time) in all rated thrust categories; (2) Withdrew CO and NOX, emission standards for newly manufactured aircraft gas turbine engines (i.e., engines already being produced) of rated thrust equal to or greater than 26.7 kN; (3) Decreased the stringency of the HC emission standards for newly manufactured aircraft gas turbine engines of rated thrust equal to or greater than 26.7 kN; (4) Revised smoke emission standards for turboprop engines to agree with existing U.S. Air Force smoke standards; (5) Revised compliance date for all gaseous emission standards from January 1, 1983 to January 1, 1984; (6) Exempted engine models produced in quantities of 20 units per year or less or not more than 200 units total future production; (7) Redefined the idle power set point for engine compliance testing; (8) Revised the test fuel specification for engine compliance testing; and (9) Transferred responsibility and authority for evaluation of requests for exemption from emission standards to the Secretary of Transportation (DOT).On October 18, 1984 (49 FR 41002) EPA amended the test fuel specifications by broadening the ranges of allowable test fuel naphthalenes content, hydrogen content, viscosity, and final boiling point values. Prior to today's action <this text is lifted from the introduction to the Califironia Federal Implementation Plan (FIP) Aviation Component>, EPA regulations were limited to smoke and fuel venting emissions standards for all commercial jet aircraft classes (turboprop engines (TP), turbofan and turbojet engines (TF),turbine engines of the JT3D model family (T3), turbine engines of theJT8D model family (T8), and turbine engines for aircraft designed to operate at supersonic flight speeds (TSS)) and HC emission standards for newly manufactured aircraft gas turbine engines (TF, T3, and T8) with a thrust greater than 26.7 kN. Separate HC emission standards exist for gas turbine engines employed in supersonic aircraft, and the smoke standards vary for the several different classes of engines (see40 CFR part 87 for a summary of EPA's aircraft engine emission control requirements and 14 CFR part 34 for the Secretary of Transportation's regulations for ensuring compliance with these standards in accordance with section 232 of the Clean Air Act).
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