(f) The standards set forth in paragraphs (a), (b), (c), (d) and (e) of this section refer to a composite gaseous emission sample representing the operating cycles set forth in the applicable sections of subpart G of this part, and exhaust smoke emissions emitted during operations of the engine as specified in the applicable sections of subpart H of this part, measured and calculated in accordance with the procedures set forth in those subparts.
Explanation For TF, T3 and T8 engines the following chart (Figure 4) provides a graphical representation of the smoke emissions requirements. This chart reflects the requirements of Subpart D as well. In general, the threshold of plume visibility can be expected to lie between SN 25 and SN 30. However, visibility is a complex function of the tailpipe diameter, viewing angle, background and meteorological conditions. Differences in any one, or any combination, of these factors, from the average, can be expected to influence this relationship. For example, a plume which is not visible when viewed in a direction normal to its axis could appear to be visible when viewed at an angle more nearly parallel to its axis. In addition apparent plume visibility seems to vary with local ambient humidity. That is, when plumes can be seen they seem to become darker as humidity increases. The regulatory intent is to assure a non-visible plume when viewed in a direction normal to the plume axis. Smoke Number (SN) 50 45 40 35 30 25 20 15 10 SN=83.6(rO)-0.274
.
SN=50 - maximum allowed SN=34 @ rO=26.7 kilonewtons SN=22 @ rO=129 kilonewtons 0 50 100 150 200 250 300 350 400 450 Rated Output (rO) - kilonewtons FIGURE 4: Smoke Emission Requirements Fo r New or In Use TF, T3, and T8 Engines
(3) – 49. Reserved Page 25
Table 2: Exhaust Emissions - Summary of Requirements
CLASS DATE STANDARD T8 Each aircraft gas turbine engine in use, or manufactured, on or after February 1, 1974 SN ≤ 30 TF ≥ 129 kN (29,000 pounds) Each aircraft gas turbine engine in use, or manufactured, on or after January 1, 1976 SN ≤ 83.6×(rO)-0.274 (rO in kN) T3 Each new aircraft gas turbine engine manufactured on or after January 1, 1978 SN ≤ 25 TF, T3, T8 >26.7 kN (6,000 pounds) Each new aircraft gas turbine engine manufactured on or after January 1, 1984 Each new aircraft gas turbine engine manufactured on or after July 7, 1997 HC ≤ 19.6 g/kN rO CO ≤ 118 g/kN rO TF, T3, T8 >26.7 kN Engines where the first production model was manufactured on or before December 31, 1995 and where the date of manufacture of the engine was on or before December 31, 1999 - effective July 7, 1997 NOX ≤ (40 + 2(rPR)) g/kN rO TF, T3, T8 >26.7 kN Engines where the first production model was manufactured after December 31, 1995 and where date of manufacture of the engine was after December 31, 1999 - effective July 7, 1997 NOX ≤ (32 + 1.6(rPR)) g/kN rO For rPR ≤ 30 and:
26.7 kN< TF, T3, T8≤ 89.0 kN TF, T3, T8 >89.0 kN Engines of a type or model for which the date of manufacture of the first individual production model was after December 31, 2003 NOX ≤ (37.572 + 1.6 rPR –
0.2087 rO) g/kN rO NOX ≤ (19 + 1.6 rPR) g/kN rO For 30< rPR< 62.5 and:
26.7 kN< TF, T3, T8≤ 89.0 kN TF, T3, T8>89.0 kN Engines of a type or model for which the date of manufacture of the first individual production model was after December 31, 2003 NOX ≤ (42.71 + 1.4286 rPR –
0.4013 rO + 0.0642 rPR(rO) g/kN rO NOX ≤ (7 + 2.0 rPR) g/kN rO For rPR ≥ 62.5:
All engines Engines of a type or model for which the date of manufacture of the first individual production model was after December 31, 2003 NOX ≤ (32 + 1.6 rPR) g/kN rO TF < 26.7 kN Each gas turbine engine manufactured on or after August 9, 1985 SN ≤ 83.6×(rO)-0.274 ≤ 50 (rO in kN) T3, T8, TSS, TF ≥ 26.7 kN Each gas turbine engine manufactured on or after January 1, 1984 SN ≤ 83.6×(rO)-0.274 ≤ 50 (rO in kN) TSS Each gas turbine engine manufactured on or after January 1, 1984 HC ≤ 140 (0.92)rPR g/kN rO TP ≥ 1,000 kW (1340 HP) Each gas turbine engine manufactured on or after January 1, 1984 SN ≤ 187×(rO)-0.168 (rO in kW) Page 26
Explanation:
Table 2, above, is a summary listing (by class of aircraft engine) of the smoke and gaseous emission regulatory levels for both new and in-use engi nes. Included as well are the ICAO CAPE 4 NO X standards effective after 12/31/2003, listed in terms of rated pressure ratio.
IV. Subpart D — Exhaust Emissions (In-Use Aircraft Gas Turbine Engines)
50. § 34.30 Applicability The provisions of this subpart are applicable to all aircraft gas turbine engines of the classes specified beginning on the dates specified in § 34.31.
(4) § 34.31 Standards for exhaust emissions
(a) Exhaust emissions of smoke from each in-use aircraft gas turbine engine of Class T8, beginning February 1, 1974 shall not exceed a smoke number (SN) of 30.
(b) Exhaust emissions of smoke from each in-use aircraft gas turbine engine of Class TF and of rated output of 129 kilonewtons (29,000 pounds) thrust or greater, beginning January 1, 1976, shall not exceed:
SN = 83.6(rO)-0.274 (rO is in kilonewtons)
(c) The standards set forth in paragraphs (a) and (b) of this section refer to exhaust smoke emissions emitted during operations of the engine as specified in the applicable section of subpart H of this part, and measured and calculated in accordance with the procedure set forth in this subpart.
Explanation Table 2, above lists by Class and by applicabl e date the smoke and gaseous emission regulatory levels.
(Note: this table is attached to Subpart C of this AC as a composite C-D compilation of requirements) Page 27
V Subpart E — [Reserved]
VI. Subpart F — [Reserved]
VII. Subpart G — Test Procedures for Engine Exhaust Gaseous Emissions (Aircraft and Aircraft Gas Turbine Engines)
18. §34.60 Introduction
(a) Except as provided under §34.5, the procedures described in this subpart shall constitute the test program used to determine the conformity of new aircraft gas turbine engines with the applicable standards set forth in this part.
(b) The test consists of operating the en gine at prescribed power settings on an engine dynamometer (for engines producing primarily shaft power) or thrust measuring test stand (for engines producing primarily thru st). The exhaust gases generated during engine operation must be sampled continuousl y for specific component analysis through the analytical train.
(c) The exhaust emissions test is designed to measure hydrocarbons, carbon monoxide, carbon dioxide and oxides of nitrogen conc entrations, and to determine mass emissions through calculations during a simulated aircraft landing-takeoff cycle (LTO). The LTO cycle is based on time in mode data during high activity periods at major airports. The test for propulsion engines consists of at least the following four modes of engine operation: taxi/idle, takeoff, climbout, and approach. The mass emissions for these modes are combined to yield the reported values.
(d) When an engine is tested for exhaust emissions on an engine dynamometer or test stand, the complete engine shall be used with all accessories which might reasonably be expected to influence emissions to the atmo sphere installed and functioning, if not otherwise prohibited by §34.62(a)(2).
(e) Other gaseous emissions measurement systems may be used if shown to yield equivalent results and if approved in advance by the Administrator or the Administrator of the EPA.
Supplemental Information Engines have generally been tested without off-take bleeds and accessory loads other than those necessary for the engine’s basic oper ation, consistent with ICAO Annex 16, paragraph 2.1.5.2.
Paragraph 34.60(d) is intended to be consistent with the procedures specified in Annex 16, with consideration for special cases where accessory loads might be large enough to influence emissions.
19. §34.61 Turbine Fuel Specification For exhaust emissions testing, fuel meeting th e specifications listed below shall be used.
Additives used for the purpose of smoke supp ression (such as organometallic compounds) shall not be present.
Explanation:
The fuel specification in Part 34 matches the, amend ed, ICAO fuel specification in Annex 16, Vol. II, Second Edition, 1993. This spec ification is typical of Jet A aviation fuel. Although EPA chose to adopt, by reference, the measurement and compliance procedures of ICAO Annex 16, Vol. II, Second Edition, Appendix, 2, 3, 5 and 6, they chose not to adopt by refer ence the ICAO fuel specification.
Instead they listed the fuel properties and allowable ranges of values.
Specification for Fuel to be Used in Aircraft Turbine Engine Emissions Testing Property Allowable range of values Density kg/m3 at 15°C 780 – 820 Distillation temperature °C 10 % boiling point 155 – 201 Final boiling point 235 – 285 Net heat of combustion MJ/kg 42.86 – 43.50 Aromatics, volume % 15 – 23 Naphthalenes, volume % 1.0 – 3.5 Smoke point, mm 20 – 28 Hydrogen, mass % 13.4 – 14.1 Sulphur, mass % less than 0.3% Kinematic viscosity at -20°C, mm2/s 2.5 – 6.5 Supplemental information:
Aircraft gas turbine engines can and do use a variety of fuels. The specific fuel type and composition can and often does have a significant effect on engi ne emissions. Knowing the fuel types in general use is important in establishing a baseline of em issions from the existing and future fleet of commercial aircraft which affects regulatory requirements. It is important when comparing emission levels from one engine with those from another. It is particularly important in evaluating engine emission levels relative to a regulation that was based, in part, on an assumed fuel specification.
Because fuel type and composition varies it was necessary to establish a fuel specification which fairly represented typical aircraft gas turbine engine fuels which are in use. The ICAO amended fuel specification is a reasonable international consensus specification, which was the result of over fifteen years of study and negotiation.
In 1972 the EPA Proposed Rule Making specified ASTM D1655 as the requirement that test fuels must meet. They allowed the use of nonmetallic additives as specified in ASTM D1655 but prohibited the use of additives used for the purpose of smoke suppression.
In 1981 ICAO published "International Standards and Recommended Practices Environmental Protection, Annex 16, Volume II, Aircraft Emission s, first edition, 1981" which included a specific detailed turbine engine test fuel specification. In 1982 the EPA adopted the 1981 ICAO fuel specification bringing the U.S. into alignment with ICAO. However, in 1984 the EPA changed its fuel specification, broadening the ranges of allowable test fuel naphthalene s, aromatics and hydrogen content, viscosity and final boiling point values in re sponse to manufacturers difficulty in obtaining fuels meeting the ICAO test f uel specification. The EPA expected ICAO to amend its fuel specification to match the EPA specification.
In 1988 ICAO did amend its fuel specification but rather than addressing the disparity between EPA and ICAO it further widened the range of accept able fuels by broadening, again, the ranges of allowable test fuel naphthalenes, aromatics and hydrogen content, viscosity and final boiling point values.
In 1993 ICAO, once again, amended its fuel specificat ion substituting density for specific gravity and changing the units of net heat of combusti on from kilojoule/kilogram (kJ/kg) to megajoule/kilogram(MJ/kg). EPA anal yzed and evaluated the resulting ICAO fuel specification with respect to its effect on aircraft gas turbine engine emissions and on general fuel availability in the Page 31
U.S. One particular concern was a decision by EPA to adopt the ICAO NOx standards. Fuel type and composition affect emissions and these standards were based on the latest ICAO fuel specification.
If the EPA decided not to adopt the ICAO fuel specifications the U.S. and ICAO NOx standards would not be entirely consistent.
EPA found that changing from specific gravity to density and kilojoules to megajoules would, obviously, not affect either emissi ons or fuel availability. In comparing actual U.S. jet fuel characteristics to differences between EPA and ICAO test fuel specifications EPA concluded that, for distillation temperatures and hydro gen content, where there were di fferences, the effect would be negligible, i.e., "not discernable". For the bro ader range of aromatics a nd naphthalenes, testing on the high end of the range would be more severe for em issions and would not effect in-use emissions.
That is, based on current U.S. jet fuel characteristics, fuels used by in-use aircraft gas turbine engines would be likely to have lower values of aromat ics and naphthalenes than used in testing and therefore lower emissions. As a result EPA adopted the 1993 ICAO test fuel specification for the purpose of certification emission testing.
Part 34 reflects, as it must, the EPA standard. Although not spelled out in Part 34 the EPA states that manufacturers should, unless otherwise specified, comp ly with the latest version of the aviation test fuel specifications from the American Soci ety for Testing and Materials, ASTM, "Standard Specifications for Aviation Turbine Fuels," D1655. There is no mention of the use of non metallic additives. Additives used for smoke suppression , such as organometallic compounds, shall not be present.
20. §34.62 Test procedur e (propulsion engines).
(a)(1) The engine shall be tested in each of the following engine operating modes which simulate aircraft operation to determine its mass emission rates. The actual power setting, when corrected to standard day conditions, should correspond to the following percentages of rated output. Analytical correction for variations from reference day conditions and minor variations in actual power setting should be specified and/or approved by the Administrator:
Mode Class TP TF, T3, T8 TSS Taxi/idle Takeoff Climbout Descent Approach (*) 100 90 NA 30 (*) 100 85 NA 30 (*) 100 65 15 34 * See paragraph (2) of this section
(2) The taxi/idle operating modes shall be carried out at a power setting of 7 percent rated thrust unless the Administrator determines that the unique characteristics of an engine model undergoing certification testing at 7 percent would result in substantially different HC and CO emissions than if the engine model were tested at the manufacturers' recommended idle power setting. In such cases the Administrator shall specify an alternative test condition.
(3) The times in mode (TIM) shall be as specified below:
Mode Class TP TF, T3, T8 TSS Taxi/idle Takeoff Climbout Descent Approach
26.0 Min.
0.5
2.5 N/A
4.5
26.0
0.7
2.2 N/A
4.0
26.0
1.2
2.0
1.2
2.3
(b) Emissions testing shall be conducted on warm ed-up engines which have achieved a steady operating temperature.
21. §34.63 [Reserved]
22. §34.64 Sampling and analytical procedures for measuring gaseous exhaust emissions.
The system and procedures for sampling and measurement of gaseous emissions shall be done in accordance with Appendices 3 and 5 to International Civil Aviation Organization (ICAO) Annex 16, Environmental Protection, Volume II, Aircra ft Engine Emissions, Second Edition, July 1993, which are incorporated herein by reference. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. This document can be obtained from the International Civil Aviation Organization (ICAO), Document Sales Unit, P.O. Box 400, Succursale: Place de L'Aviation Internationale, 1000 Sherbrooke Street West, Suite 400, Montreal, Quebec, Canada H3A 2R2. Copies may be reviewed at the FAA Office of the Chief Counsel, Rules Docket, Room 916, Federal Aviation Administration Headquarters Building, 800 Independence Avenue, SW., Washington, DC, or at the FAA New England Regional Offce, 12 New England Executive Park, Burlington, Massachusetts, or at the Office of the Federal Register, 800 North Capitol Street, NW., Suite 700, Washington, DC.
23. § 34.65—34.70 [Reserved]
24. § 34.71 Compliance with gaseous emission standards Compliance with each gaseous emission standard by an aircraft engine shall be determined by comparing the pollutant level in grams/kilonewton/thrust/cycl e or grams/kilowatt/cycle as calculated pursuant to §34.64 with the applic able emission standard under this part. An acceptable alternative to test ing every engine is described in Appendix 6 to ICAO Annex 16, Environmental Protection, Volume II—Aircraft Engine Emissions. Second Edition, July 1993, effective March 20, 1997. This incorporation by reference was approved by the Director of the Federal Register in accordance wi th 5 U.S.C. 552(a) and 1 CFR part 51. This document can be obtained from, and copies may be reviewed at the respective addresses listed in §34.64. Other methods of demonstrating compliance may be approved by the FAA Administrator with the concurrence of the Administrator of the EPA.
[(Amdt. 34-2, Eff. 9/98)] Page 33
VIII. Subpart H — Test Procedures for Engine Smoke Emissions (Aircraft and Aircraft Gas Turbine Engines)
25. §34.80 Introduction Except as provided under §34.5, the procedures described in this subpart shall constitute the test program to be used to determine the conformity of new and in-use gas turbine engines with the applicable standards set forth in this part. The test is essentially the same as that described in §§34.60-34.62, except that the test is designed to determine the smoke emission level at various operating points representative of engine usage in aircraft. Othe r smoke measurement systems may be used if shown to yield equivalent results and if approved in advance by the Administrator or the Administrator of the EPA.
Supplemental information The regulatory smoke standards established by EPA and ICAO were set to ensure the invisibility of the engine exhaust when viewed across the plume. Smoke level is determined indirectly, by means of the loss of reflectance of a filter used to tr ap smoke particles from a prescribed mass of exhaust per unit area of filter. The result is a dimens ionless number “SN.” Usi ng generalized relationships between engine thrust and exhaust duct diameters, an empirically derived relationship between smoke number (SN) and engine thrust was developed. The information available to develop this relationship came from early gas turbine engines with straight jet or low bypass ratios. There was little or no dilution of the engine core exhaust gas wh ich is not the case with modern, high bypass, engines. ICAO, which defines – by reference – the measurement standard, requires smoke to be measured at or near the engine exhaust nozzle exit plane, which is consistent with the requirements for using SN as an indicator of visibility for the early engines. Some current engine designs, however, extend the bypass cowling beyond the core nozzle and for these, by definition, the measurement plane includes the bypass airflow. This results in a lower SN, and some question about the relationship of SN to plume visibility for these designs. Introduction of ultra high bypass ratio engines, such as the ducted or unducted prop fan engines will serve to further complicate this situation. The measurement me thod itself has proven to be physically robust, repeatable and reliable, but time consuming and expensive – particularly for traverse testing.
As a direct result of the narrowly defined sm oke number, demanded by the prescribed method of measurement and its implied correl ation with engine exhaust plume visibility, finding an alternate, equivalent smoke method has proven to be challengi ng. Such a method must necessarily correlate with smoke number, not with plume visibility, i.e., any measured value arrived at using an alternate method must be associated unambiguously with an equivalent smoke number. Some engine manufacturers use an optical device that provides continuous, almost real time smoke measurement.
This device is patterned after the Hartridge optical smoke meter. Their experience has been that the optical measurements correlate well with in-house ICAO Appendix 2 stained filter measurements with considerable savings in engine test time. If an engine manufacturer wanted to use such a device for certification it would be allowed upon demonstration, by means of actual test data, that the device was equivalent to Appendix 2. It should be mentioned that the correction found at a single manufacturer’s facility has not been demonstrated between engine manufacturers facilities so some caution is advised when assessing equivalency. Because smoke measurement is time consuming, particularly during traversing, and places great demands on the engine, finding an alternate and less costly method is and will continue to be attractive.
The smoke measurement standard was developed for engines that generated smoke at considerably higher levels than are seen today. This affect s the relative accuracy of the method. The measurement is considered (by the SAE E-31 committee which developed the method) to be no more accurate than ± 3 SN. At smoke levels of SN 50-60 this represents an accuracy of 6-5%. At regulatory standards of 30 and below, relative accuracy becomes 10-20% or more.
Also significant is the requirement to "...provide evidence to the certificati on authority, by means of detailed traverses, that the proposed probe design and position does provide a representative sample for each prescribed power setting." ICAO Appendix 2 does not provide a definition of "representative" nor does it specify any procedures by which conformance to this requirement can be demonstrated.
Because traversing is time consuming, costly, and highly problematic with some new engine designs, this lack of definition and test of 'representativen ess' is a serious problem and must be addressed, almost uniquely, for each emissions certification test for which there is a traversing requirement. As with gaseous emissions to a first approximation how well the exhaust was sampled can be estimated from a carbon balance which relates the total carbon measured (mostly CO 2) to a measured value of fuel-air ratio. For engine modes above idle a nec essary condition could be agreement between fuelair ratios arrived at from emissions and performance measurements within ± 10%. This would not, however, be a sufficient condition. The variability of smoke is typically greater than the variability of CO2, the dominant species, and so additional work needs to be done. Because smoke, as with the gaseous emissions, seems to be normally (gaussi an) distributed, in the core at least, standard statistical techniques can be used to estimate the mean value for the exhaust and the number of sampling points necessary to arrive at the required c onfidence level. The information to do this can come from prior data or from trial traverses on the current or previous, similar, engines. Note that evidence of a satisfactory probe design can be as simple as having proven the design on a previous, similar, engine. Similarity would, then, need to be proven to the certificating authority.
The smoke sampling and measurem ent procedures sta ndardized in ICAO Annex 16, Volume II, second edition, 1993, Appendix 2, are deriv ed from an SAE standard, SAE Aerospace Recommended Practice (ARP) 1179, Aircraft Gas Turbine Exhaust Smoke Measurement. ARP 1179, first issued in 1971, is the result of a co llaborative government/industry effort to develop a consensus standard for measuring smoke from these sources. It is a dynamic standard which is actively managed by the SAE E-31 committee but has changed little over the years. ICAO maintains an observer on the E-31 committee. Agreeable changes in ARP 1179 can be reflected in future versions of ICAO Appendix 2. With the ICAO procedures being called out by reference (40 CFR part
87), any changes in Appendix 2 will necessarily be reflected in the requirements of Part 34.
The relationship of CO 2 to fuel is straight forward given the fuel formulation. For example, a typical kerosenic fuel in the middle of the specific ation for fuel hydrogen mass ration would have a formulation C12H23. Knowing the atomic weights of carbon (12) and Hydrogen (1.008) you calculate the relative mass of carbon in this fuel molecule to be 0.86, or 1 kg of fuel would contain 0.86 kg of carbon. Taking the atomic weight of oxygen to be 16, a similar calculation shows that 1 kg of fuel, upon complete combustion, would yield 3.16 kg of CO 2 (these numbers are rounded for illustrative purposes). For an engine running at high power, say a fuel to air of 0.02 kg fuel/kg air the resulting CO2 mass ratio would be .02*3.16 or approximately .063 kg CO 2 per kg of air. Taking the molecular weight of CO 2 to be 44.01, air to be 28.96 and the specific weight of air to be 1.225 kg/m 3 the volumetric ratio is seen to be 0.0416 or 4.16%. Since CO 2 instruments read in volumetric percent, this is the value the instrument should read when the engine is operating at 0.02 f/a. Obviously the reverse calculation, fuel to air ratio from measured volumetric CO 2, proceeds in a similar fashion.
This relationship is convenient as a nominal indi cator of sampling status assuming you know the fuel to air ratio, i.e., by multiplying the fuel to air rati o by 200 you should arrive at an approximate value of CO2 in volumetric percent.
26. §34.81 Fuel Specifications Fuel having specifications as provided in §34.61 shall be used in smoke emission testing.
Supplemental information The requirement for emissions certification testing wi th a fuel which meets a particular specification provides a fixed point of reference for the engine. It provides for some degree of control over the effect of fuel composition on smoke formation and em ission. It also helps in the assessment of the Page 35
effects of changing technology. It will not ens ure continued conformance to the smoke emissions standards if a fuel outside of the ICAO fuel specification is used in practice.
27. §34.82 Sampling and analytical procedures for measuring - smoke exhaust emissions The system and procedures for sampling and measurement of smoke emissions shall be done in accordance with Appendix 2 to International Civil Aviation Organization (ICAO) Annex 16, Volume II—Aircraft Engine Emissions, Second Edition, July 1993. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. These materials are incorporated as they exist on the date of the approval and a notice of any change in these materials will be published in the Federal Register. Frequent changes are not anticipated. This document can be obtained from the International Civil Aviation, P.O. Box 400, Succursale: Place de L' Aviation Internationale, 1000 Sherbrooke Street West, Montreal, Quebec, Canada H3H 2R2. Copies may be inspect ed at the FAA Office of the Chief Counsel, Rules Docket, room 916, Federal Aviation Administration Headquarters Building, 800 Independence Avenue, SW., Washington, DC, or at the FAA New England Regional Office, 12 New England Executive Park, Burlington, Massachusetts, or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
Supplemental information ICAO Appendix 2 was derived, almost exclusively, from SAE Ae rospace Recommended Practice ARP1179 “Aircraft Gas Turbine Engine Exhaust Smoke Measurement.” This Aerospace Recommended Practices and, by implication, ICAO Appendix 2 truly represents a significant cross section of the affected aircraft community. The U.S. government was represented by the EPA and precedents, the FAA, Bureau of Mines, NASA, Ai r Force and the Navy. The commercial sector included airlines, airframe manufacturers, engine manufacturers, fuel suppliers, calibration gas suppliers and instrument manufacturers. Over the years, as the methods ev olved, many tests were conducted both by individual groups and as collabora tive efforts. Data and information that resulted was freely shared, discussed and factored into this ARP as appropriate. The method that resulted, while not perfect, is well understood, repeatable and is robust. However there are some problems which have arisen due to changing engine designs and the intent of ensuring low visibility exhaust plumes.
28. §34.83 – 34.88 [Reserved]
29. §34.89 Compliance with smoke emission standards Compliance with each smoke emission standard shall be determined by comparing the plot of the smoke number as a function of power setting with the applicable emission standard under this part. The smoke number at every power setting must be such that there is a high degree of confidence that the standard will not be exceeded by any engine of the model being tested. An acceptable alternative to testing every engine is described in Appendix 6 to ICAO, Annex 16, Environmental Protection, Volume II, Aircraft Engine Emissions, Second Edition, July 1993. This incorporation by reference was approved by the Di rector of the Federal Re gister in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. This document can be obtained from the address listed in 34.64. Other methods of demonstrating compliance may be approved by the Administrator with the concurrence of the Administrator of the EPA.
Supplemental information In agreeing to use the ICAO Compliance procedur es, EPA has concluded, by implication, that the combination of the test and the compliance proce dures will result in as surance that, with 90% confidence 100% of the engines produced, model and type, will meet the smoke standard if the engine or engines tested for smoke, meet the standard.