900 = (33000Pv) / 2900 – Rs Subtracting the first equation from the second results in a difference of about 7 horsepower. The nominal maximum continuous power for the engine is 235.
All the information necessary to calculate the difference in noise levels between the two propeller installations is now available. The difference in the noise levels for the two cases is the algebraic sum of the following adjustments:
a) Decrease in noise level due to increase in reference height:
H = 22 log (679/753) = –0.99 dB
b) Increase in noise level due to increase in helical Mach number:
M = 150 log (0.8181 / 0.7021) = 9.96 dB
c) Increase in noise level due to increase in engine power:
The rated maximum continuous power for the engine is 235 horsepower. The incremental change in noise level is approximately:
P = 17 log [(235+7)/(235)] = 0.22 dB
d) Increase in noise level due to increase in inflow angle:
= 0.5 × (4.15°–3.25°) = 0.45 dB
e) Total change in noise level:
L = –0.99 + 9.96 + 0.22 + 0.45 = 9.64 dB Clearly, an acoustical change exists between the fixed and variable pitch propeller installations unless some other changes are made to the airplane.
(4.3) Change in propeller diameter Calculating the effect on Appendix G noise level of changing propeller diameter without any other change in power or performance is a straightforward application of the following equation:
M= k log (MM/MP) where k equals a constant dependent on the propeller design and Mach number range. A nominal value of 150 is permitted in G36.201 of part 36 if MP is smaller than MM (Parent and Modified respectively).
Although a change in propeller diameter will usually also change performance, if it can be shown that no degradation in takeoff distance or climb performance is created, the airplane performance before the change can be stipulated as the performance after the change. It is clear that an increase in diameter, considered alone, will increase the noise level. It is sometimes desirable to increase propeller diameter to improve climb performance, sometimes at the sacrifice of some cruise capability. The increased noise level caused by the greater diameter can be offset by a reduction in rpm, if the resulting airplane performance is satisfactory. Where this method is used to show "no acoustical change," it will be necessary to pe rform FAA approved takeoff and climb tests to verify Page 25
performance. The following two examples illustrate the e ffect that changes in propeller diameter have on the noise level.
Example 3: The airplane in Examples 1 and 2 is normally equipped with a two-blade propeller having an 84 inch diameter. The same propulsive efficiency is claimed when using the same engine, same propeller rpm, if the propeller is replaced with a propeller of 86 inches diameter. For the same reference height and airplane speed, the difference in noise level between the two installations ma y be calculated as follows. In Examples 1 and 2, the airplane Mach number was 0.1378 and the propeller rotational Mach number was 0.8556 for an 84 inch diameter propeller. For the same altitude and rpm, the rotational Mach number is directly proportional to the propeller diameter, so the rotational Mach number for the 86 inch diameter propeller is 86/84 times 0.8556, or 0.8760. The corresponding Parent and Modified helical Mach numbers before the change and after the change become 0.8666 and 0.8868. The noise level difference is:
M = 150 log (0.8868 / 0.8666) = 1.50 dB If the new propeller has three blades, which would cause a shift in the blade passage frequency, the above analysis would not be adequate to determine the entire effect of the change. The analysis would have to be extended to account for the noise delta caused by the ground reflections and A-weighing filter effects, or flyover tests would have to be conducted.
Example 4: An applicant wishes to replace an existing variable pitch propeller with a diameter of 76 inches for a different pitched propeller with a diameter of 80 inches. The new propeller is designed to provide a somewhat shorter takeoff distance and better rate-of-climb for the airplane. The applicant does not want to go to the trouble of determining the improvement in takeoff distance or climb rate, and is willing to use the existing handbook data to determine reference height.
The applicant has demonstrated to the FAA that, in flight during reference climb conditions, his existing propeller develops 2600 rpm. He believes that, even with a modest limitation on climb rpm to negate the increase in noise level that a larger diameter propeller would normally generate, the larger propeller will still be advantageous. The rpm limitation that would have to be imposed for "no acoustical change" to result, assuming the reference height of 700 ft and true airspeed of 74 kt do not change and the propeller tip shape and thickness are identical, is determined as follows.
Since the airplane climb speed remains the same, the helical Mach number will be the same if the rotational Mach numbers for the two propellers are held constant. The actual reference height and airspeeds are not relevant to this determination. It is not even necessary to calculate the actual Mach numbers, since the rotational Mach numbers will be the same if the products of propeller diameter and rpm remain constant for the two cases. For the original 76 inch propeller, the product is 76 times 2600 or 197,600. The rpm limitation with an 80 inch propeller is therefore 197,600 divided by 80, or 2470 rpm. If this rpm gives satisfactory takeoff and climb performance, limiting climb rpm to 2470 will result in no acoustical change when the larger propeller is installed. Other airworthiness considerations (e.g., engine cooling, stalling, etc.) may need further consideration.
(4.4) Change in engine power Increasing the size of an engine without changing the takeoff weight of an airplane will change the Appendix G noise level. If no change in performance were involved, the level would increase by 17 times the logarithm of the ratio of the increased horsepower to the original horsepower. However, clearly a change in performance does take place. Takeoff distance is shortened, and climb rate is increased. Often, but not always, a propeller change is also made. If the increase in performance offsets the effect on noise level of the change in engine horsepower, no acoustical change occurs. The following example illustrates the required analysis.
Example 5: The airplane in Example 1 is originally equipped with an engine rated at 225 horsepower at 2600 rpm.
The desired installation is for an engine rated at 250 horsepower at 2650 rpm. The same 84 inch two-blade propeller is used in each case. The acoustical effect of this change is evaluated as follows.
Step 1. If propeller efficiency remains the same, takeoff distance varies inversely with engine power and directly as the square of takeoff weight. The takeoff distance to 50 ft height after the increase in horsepower, D50M, without any weight increase, is the original takeoff distance, D 50P, times the ratio of the original horsepower to the increased horsepower:
D50M = D50P × (HPP/HPM) ft In this example:
D50M = 2220 (225) / (250) = 1998 ft Note.— This is an approximation and the final determination for no acoustical change must use FAA approved data from the AFM or the AFMS for the modified airplane. If the applicant chooses not to take credit for (and thus determine per FAA flight test guidelines) the improved takeoff distance, they cannot take credit for the decrease in distance in the acoustical change determination.
Step 2. From equation (15), rate-of-climb for a given airplane configuration is directly proportional to the ratio of engine power to airplane weight, minus the power off sink rate. The constant of proportionality is the unit conversion factor of 33,000 times the propeller efficiency. In Example 1, the product of propeller horsepower developed in climb is less than the rated horsepower due to installation effects and air density less than at sea level. It can be assumed that the same ratio of losses will apply to a slightly higher rated horsepower engine.
Assuming these losses cancel each other out, the apparent propeller efficiency for Example 1 can be stated as the propulsive efficiency, 190, divided by the rated horsepower, 225, for an apparent efficiency of 0.844. Equation
(15) can then be used to determine the rate-of-climb at the increased horsepower:
RCM = (33000) (0.844) (250) / 3000 – 1125 = 1197 ft/m Step 3. Climb angle is given by:
= sin-1 [RC / (1.688 × 60 × Vy)] M = sin-1[1197/(101.3)(90)] = 7.55° Step 4. The reference height after the change, HM, is:
HM = 50 + (8200–1998) tan (7.55) = 872 ft Step 5. Determine reference helical Mach number:
a) At 872 ft the speed of sound is:
cP = 1113.2 ft/s True airspeed is calibrated airspeed divided by the square root of the density ratio:
P= 0.97472
b) Best rate-of-climb speed of 90 kt at sea level becomes a true airspeed at 872 ft of:
VTAS = 90 / 0.97472 1/2 = 91.2 kt
c) Airplane Mach number at 91.2 kt is:
M = (1.688 × 91.2) / 1113.2 = 0.1383
d) Propeller rotational Mach number is:
MR = 0.8725
e) Helical tip Mach number is:
Mh = [(0.1383)2+ (0.8725)2]1/2 = 0.8834 Step 6. Reference horsepower is now 250.
Step 7. Calculate the increment in noise level under part 36 Appendix G operating conditions:
a) Change in noise level due to increase in height:
From Example 1, HP = 690 ft, and from above HM = 872 ft.
H = 22 log (690 / 872) = –2.24 dB
b) Increase in noise level due to increase in helical Mach number:
From Example 2, Mh = 0.8666:
M = 150 log (0.8834 / 0.8666) = 1.25 dB
c) Increase in noise level due to increase in horsepower:
P = 17 log (250 / 225) = 0.78 dB
d) Change in noise level due to change in inflow angle:
In Example 1 the inflow angle was 6.11 degrees with an assumed inflow angle of 4.25°. From equation
(18):
= 0.5 × (4.25°–3.11°) = 0.57 dB
e) Total change in noise level:
The total change in noise level, L, is the algebraic sum of the four adjustments.
L = –2.24 + 1.25 + 0.78 + 0.57 = 0.36 dB The change in noise level due to an increase in horsepower, in this example, is not offset by the effect of improved takeoff performance, resulting in an "acoustical change" of 0.36 decibel. In order to become an NAC situation, some change in rating should take place. A small reduction in allowable takeoff rpm might be reasonable. Several iterations of the above calculations might be necessary to determine the optimum conditions. Any changes in performance where credit is being claimed must be FAA approved, determined using FAA approved methods, Page 28
and published in the FAA approved AFM or AFMS (e.g., improved climb rates, shorter takeoff distances, change in Vy, etc.). Additional airworthiness criteria may need to be reestablished.
(4.5) Increase in drag with no other changes Any modification to an airplane that increases its drag during takeoff and initial climb will increase the Appendix G noise level unless other changes are also introduced. If takeoff distance is increased, or rate-of-climb decreased, or both, the reference height will decrease. The change in level can be calculated from the adjustment equations provided previously if the change in performance can be determined. If an applicant wants to show compliance with the noise regulation via the NAC method, they will probably have to conduct takeoff distance and climb tests. If it looks as though the proposed modification will increase drag sufficiently to make a measurable performance change, then an offsetting change will be required. The amounts of increase or decrease in noise level involved can be calculated by the methods use in the previous examples.
(4.6) Acoustical effects of combined changes Many proposed airplane modifications involve several changes. Examples are replacing an engine and fixed pitch propeller with a higher power engine and a variable pitch propeller, or increasing engine power and takeoff weight at the same time. The acoustical consequences of thes e combined effects can be calculated by combining the methods used in the examples. The sequence for calculating these effects is as follows:
a) Determine the effect changes in takeoff distan ce and rate-of-climb will have on reference height.
b) Determine the effect of helical Mach number caused by any ch anges in airplane speed, propeller rotational speed, or change in speed of sound because of change in reference height.
Note.— The default value of 150 for “k” in the correction equations is only valid when used to determine an increase in helical mach number. It CANNOT be used to reduce the noise level. The 150 factor is a generalized conservative value for simplified calculations where the true “k” value is not determined. Thus it is inherently inaccurate.
c) Determine the effect of an y changes in engine power.
d) Determine any change in noise level due to change in airplane climb angle.
e) Obtain the algebraic sum of the four incremental changes in sound level.
f) If the sum is greater than zero, there are two choices:
— Conduct Appendix G tests as described in the regulation; or — Evaluate different operating conditions to obtain an incremental noise level that is not greater than that of the original airplane. This may be accomplished by derating the engine, reducing fuel/payload, and/or limiting maximum takeoff rpm. One or a combination of these modifications may be iterated until a negative noise increment is obtained by the methods used in the examples.
The cost of not performing an Appendix G noise test should be balanced against the loss of airplane performance or takeoff weight limitations during the lifetime of operation.
101(f) Acquisition of In-duct and/or Near -field Data for Demonstration of NAC
(1) General The FAA has found it acceptable for applicants to conduct engine or component only noise tests to evaluate minor engine changes. Frequently the objective for these tests is to provide evidence that the changes involved produce Page 29
negligible impact on EPNL noise values and may theref ore be categorized as NACs relative to the certificated aircraft configuration. Such testing includes component tests, static engine tests in a test cell, near-field microphone measurements, and in-duct dynamic pressure measurements.
(2) Guiding principles The overall guiding principles to be followed in providing acceptable evidence for substantiation of engine NACs are:
a) the measurements and analyses should adequately model the noise such that small changes in aircraft noise levels can be quantified; and
b) the noise measurement technique and the test e nvironment should not introduce changes to the noise sources that invalidate the predicted small changes in aircraft noise levels.
These guiding principles should be applied in all cases, with details of the approach being justified on a case-bycase basis as appropriate.
Note 1.— It is important that the near-field or in-duct measurements enable a sufficiently accurate prediction of the changes to engine noise in the far field.
Note 2.— It is important that the noise-generating mechanisms of interest are not significantly affected by the test cell environment. The test cell should have an exhaust collector to minimize re-circulation. There should be insignificant inlet distortion or inflow turbulence, or a turbulence control screen or ICD should be employed to minimize such distortions or turbulence. Test cell measurements might not be appropriate for assessing jet noise changes because of the influence of the test cell on the jet development.
Note 3.— Care must be taken to ensure the noise source under investigation is not masked by other unrepresentative noise components. While a reduced acoustic standard of components not under investigation might be acceptable in many cases, there are examples where such differences might invalidate the premise of an NAC (e.g., noise from the intake being masked by a hard-walled bypass duct, or significant noise from an overboard air dump contaminating the measured noise).
(3) Measurement systems Typical measurement systems used to acquire data for substantiation of an engine NAC include:
a) near-field microphones, either in test cells or outdoor facilities;
b) in-duct transducer measurements in the fan inlet or exhaust duct; and
c) core probes to assess combustor or low pressure turbine design changes.
4) Measurement and data analysis procedures The measurement and data analysis process should be accomplished on the basis of the following criteria:
a) an adequate array of transducers should be used to ensure that the measurements adequately model the noise (To determine overall changes in sound pressure level, the measured noise levels will typically need to be averaged azimuthally, radially and/or axially in order to avoid false conclusions being drawn from anomalous readings from single transducers.);
b) environmental conditions in the test setup should be monitored to demonstrate that the local environment
(e.g., test cell temperature) do not cause significant anomalies in the measured noise differences;
c) microphones should be mounted on the test cell wall or on the ground or floor but not in the shadow of any support structures or other test hardware;
d) in-duct transducers should be flush-mounted with minimal loss of area of acoustic treatment. Rakemounted transducers in the flow path should be avoided if they shed wakes that impinge on downstream structures and thereby create significant noise;
e) core probes should be fixed securely to the pylon, boat-tail fairing or other support and not be excessively buffeted by the flow;
f) the specifications of the measur ement system and calibration procedures for microphones, recording and reproducing systems should be in accordance with A36.3 of part 36 (Laboratory calibrations of in-duct transducers and core probes should be conducted be fore and, if possible, after each test. The dynamic range of the transducers should be sufficient to avoid overload.);
g) data should be acquired over the relevant engine operating speeds and for all relevant combinations of engine variables, as specified in the latest version of Reference T13;
h) the interpretation of in-duct meas urements should take into account the possibility that decaying or cutoff acoustic waves may be present that may mask ch anges sensed in the far field of the propagating wave; and
i) two alternative methods could be used in the subsequent analysis of the measured noise levels to demonstrate an NAC:
1) the measured component noise changes could be incorporated into a noise model that predicts the aircraft EPNL. This method has the added value of taking into account in-flight effects and the relative significance of the different noise sources; or
2) in some circumstances, it might be possible to reach the conclusion of an NAC without the need to incorporate the measured component noise changes into a noise model that predicts aircraft EPNL.
The measured noise changes could be examined to see if there is no increase in noise levels at any relevant frequency or engine condition.
Generally, noise models that predict the aircraft noise level expressed in EPNL are based on far-field static test data. Consequently, in either analysis it will be necessary to agree with the FAA on the method for calculating the impact on far-field static noise resulting from near -field microphone measurements or in-duct transducer measurements. This will normally require sound engine ering judgment, seeking out patterns in the data and technical explanations for any observed differences.
Furthermore the statistical uncertainty in the data should be considered. For example if statistical analysis shows that the uncertainty in the data is large and the differences are small, then no conclusions can be drawn from the data. On the other hand if the tests show large decreases in noise levels that outweigh the uncertainty in the data it may be possible to conclude, with reasonable certainty, that the changed engine is indeed quieter than the original engine.
Chapter 2 NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS
CHAPTER TABLE OF CONTENTS
201 EXPLANATORY INFORMATION32
201(a) Part 36 - Subpart A - General32
201(a)(1) Applicability and definitions32
201(a)(2) Aircraft configuration34
201(a)(3) Voluntary changes34
201(a)(4) Airworthiness certificates36
201(a)(5) Airworthiness certificates36
201(a)(6) One-Stage limit36
201(a)(7) Stage 1/ Stage 2 limits37
201(a)(8) Date of application37
201(a)(9) Airworthiness compatibility38
201(a)(10) Limitations of part38
201(a)(11) Configuration consistency39
201(a)(12) Dual stage certification39
201(a)(13) Exempt helicopter modifications39
201(a)(14) Helicopter compliance with part 3639
201(a)(15) Noise limits40
201(a)(16) Stage 2 helicopters40
201(b) Subpart B- Transport Category Large Airplanes and Jet Airplanes40
201(b)(1) Noise measurement and evaluation40
201(b)(2) Noise measurement constraints41
201(b)(3) Flight manual statement of Chapter 4 equivalency42
201(c) Subpart H – Helicopters42
201(c)(1) Noise limits42
201(d) Subpart 0 – Operating Limitations; and Information43
201(d)(1) Procedures, noise levels, and other information44
201(d)(2) Non-flight test data50
201(d)(3) Manuals, markings and placards50
201(d)(4) Supplemental information53
201(d)(5) Index of acceptability53
201(d)(6) Airplane limitations53
201(d)(7) Non-complying agricultural and fire fighting airplanes54
201(d)(8) Operating limitations54
201 EXPLANATORY INFORMATION 201(a) Part 36 - Subpart A - General 201(a)(1) Applicability and definitions §36.1(a)
(1) Applicable requirements Page 32
Unless otherwise specified, the date to be used for determining the applicability of the appropriate part 36 standards for an aircraft type design is the date on which application for a type certificate was made. An application for type certification is effective for the time periods specified in §21.17(c) of part 21.
(2) Noise related type certification requirements See paragraph 7-8 of Reference G4.
(3) Supplemental type certificates See paragraph 7-8 of Reference G4.
(4) Definitions of terms Section 4 of the preamble of this AC provides definitions of terms (see Table 2) related to the aircraft types and categories within Items (1) – (4) of §36.1(a).
Table 2. Aircraft terminology and categories
AIRCRAFT TERMINOLOGY AIRCRAFT TERMINOLOGY Aircraft Large Aircraft Airplane Small Aircraft Jet Airplane Turboprop Airplane (Note 3) Propeller AIRCRAFT CATEGORIES (Note 1) AIRCRAFT CATEGORIES (Note 1) Airplane Helicopter Acrobatic Normal Commuter Transport Normal Primary Restricted (Note 2) Transport Utility Note 1.— Airplane Categories and Aircraft Classes: Part 1 recognizes a distinction between Airplane Categories (e.g., acrobatic , commuter, normal, primary, restricted , transport and utility) and Aircraft Classes
(e.g., Conventional Takeoff and Landing (CTOL), Vertical Takeoff and Landing (VTOL), Short Takeoff and Landing (STOL), Reduced Takeoff and Landing (RTO L), and Supersonic Transports (SST)). The noise certification requirements contained in part 36 are specified for several Airplane and Helicopter Categories but not for STOL, RTOL, SST (except for Concorde), or VTOL Aircraft Classes.
Note 2.— Restricted Category Propeller-Driven Large Airplanes: Propeller-driven large airplanes that have been type certificated in the restricted category (see §21.25 of part 21) are not required to demonstrate compliance with the requirements of part 36. In the absence of part 36 applicability, an Environmental Assessment is required (see paragraph 7-4 of Reference G4 for additional information).
Note 3.— Turboprop Airplanes: Turboprop-powered airplanes are included under the part 36 requirements applicable to propeller-driven airplanes (i.e., subsonic transport category large airplanes; propeller-driven small airplanes, including acrobatic, normal, restricted, and transport categories; or propeller-driven Page 33
201(a)(2) Aircraft configuration §36.1(b) An applicant’s proposal for an aircraft configuration to be certified under the requirements of part 36 must include any type design changes that may be a result of airworthiness standards testing and analysis, and which would result in acoustical changes. (See §36.1(c) for FAA criteria on when aircraft type design changes represent an acoustical change). If an applicant does not propose the appropriate ai rcraft configuration, additional noise certification testing and analysis may be required.
201(a)(3) Voluntary changes §36.1(c)
(1) Examples of voluntary changes in type design A voluntary change in the configuration of an aircraft means a change in the type design of that aircraft. Examples of voluntary changes in aircraft type design that may affect part 36 certificated noise levels are as follows:
a) increased engine thrust (powe r) to improve aircraft performance;
b) maximum gross weight changes;
c) limitations on operational flap settings related to noise;
d) hardware revisions (e.g., vortex generators, flap configuration, wing tip stabilizers, wing tip fuel tanks, etc.);
e) engine modifications to improve engine performance, accelera tion, deceleration, or surge margin protection;
f) addition of wing or body hardware to improve aerodynamics;
g) external nacelle changes to improve air flow patterns;
h) engine inlet changes to improve ice protection;
i) reduction of engine blade tip clearances to improve inlet flow characteristics, and;
j) modifications to engine /nacelle acoustic treatments.
(2) Acoustical change criteria A voluntary change in the type design of an aircraft that may result in an increase in its certificated noise levels is defined as an “acoustical change.” A type design change that does no t result in an “acoustical change” as defined in section§21.93(b) of part 21 is referred to as a “no acoustical change” (NAC). The numerical criteria used by the FAA in defining an acoustical change for airplanes and helicopters are provided in 101(d) and (e) of this AC and are established to limit the cumulative effects of multiple small changes.
(3) NAC cumulative effects When type design changes result in reduced noise levels, an applicant may elect not to provide the full part 36 substantiation, but instead provide FAA with data a nd/or information to subs tantiate an NAC. However subsequent type design changes may require full part 36 certification because of cumulative acoustical effects.
Example: An applicant proposes a configuration change which will reduce the noise levels by approximately
2.1 dB for the flyover noise measurement point, 1.1 dB for the lateral noise measurement point, and with no Page 34
change in noise level at the approach noise measurement point. FAA verifies that the noise levels were reduced, and the applicant accepts the pre-change configuration certificated noise levels as published in the AFM to apply to this change in type design. The applicant may not make another type design change as an NAC that increases the flyover noise level and the lateral noise level without providing substantiation of the cumulative effects of this type design change on AFM noise certificated levels. Multiple type design changes must be evaluated on a cumulative basis (as a combined single configuration) for each noise measurement point for the purposes of determining whether there is an acoustical change.
(4) NAC approvals FAA may approve results of component laboratory demonstrations, back to-back noise comparisons from ground tests or flight tests of each configuration, acoustical analyses, etc as acceptable for substantiating that an applicant’s proposed changes to an aircraft type design is an NAC. The results from these evaluations must be applicable to an aircraft’s certificated noise levels at the part 36 reference noise measurement points.
(5) Non-standard jet airplane configurations Sections 21.93(b)(2)(i) and (ii) specify exceptions under which certain changes in jet airplane type design are not subject to compliance with part 36 requirements because such configurations are not intended for normal operations, but are typically required for maintenance ope rations (e.g., ferry flights, transporting engines to aircraft that cannot be ferried, etc.).
(6) Time-limited changes Time-Limited engine or nacelle chan ges on jet airplanes for periods of up to 90 days (as specified in §21.93(b)(2)(iii) of part 21) may be necessary for continued airplane operation until maintenance can be performed on the original engines or nacelles that were changed. These changes must comply with applicable airworthiness standards and the maintenance, preventa tive maintenance, rebuilding and alteration inspection requirements of part 43. Such changes do not require co mpliance with part 36 requirements even though they may result in an increase in airplane noise levels, relative to the certificated noise levels. FAA policy (see Federal Register Vol. 64, No. 225, Page 65655, dated November 23, 1999) permits the 90 day period allowed by §21.93(b)(2)(iii)of part 21 to continue to be used af ter December 31, 1999, but only for maintenance-related purposes. It cannot be used for meeting Stage 3 requirements due to lack of an adequate number of spare engines or nacelles, or insufficient number of engines or nace lles to operate a Stage 3 fleet at a given time. Section
21.93(b)(2)(iii) may only be us ed to intermix engines when maintenance is required and no conforming engine or nacelle for the configuration is available.
(7) Special purpose aircraft Type design changes to propeller-driven small airplanes and helicopters do not need to comply with the provisions of part 36 when they are operated for special purposes as specified in §§21.93(b)(3)(i-iv) and §21.93(b)(4) of part
21.
(8) Applicant’s responsibility Pursuant to §21.93(b), an applicant must identify type desi gn changes that affect an aircraft’s certificated noise levels by aircraft serial number and must demonstrat e part 36 compliance for those aircraft. The noise levels approved by the FAA for the modified aircraft must be documented in an FAA Approved AFM or RFM by either a revision to the AFM or RFM (typically an option only available to the aircraft manufacturer), an AFM or RFM Supplement (for Supplemental Type Certificates and Field Approvals), or a Supplemental AFM or RFM (for aircraft that do not have a FAA Approved AFM or RFM). Configurations and modifications for which noise approval is required must be found to comply with applicable airworthiness requirements specified in part 21 as well as the requirements of §36.3 of part 36.
201(a)(4) Airworth iness certificates §36.1(d)
(1) Requirements for Issuance of Airworthiness Certificates An airworthiness certificate is issued for each airplane produced, and is a means of distinguishing (by date of issuance) airplanes within a production run that comply with the noise certification requirements of part 36. Prior to the original issuance of a standard airworthiness certificate (see §21.183 of part 21) and regardless of the date of application for certification, compliance with the regulatory requirements of part 36 (including Appendix B) is required for a transport category large airplane, or for a jet airplane regardless of category (see paragraph 7-11(a) of Reference G4). The following table summarizes the requirements of §36.1(d) of part 36.
Table 3. Requirements of §36.1(d) of part 36 Maximum Airplane Weight Airplane Type Engine Configuration Effective Date of Part 36 Compliance Date for Airplanes With Initial Flight Time on or After 75,000 pounds or less Subsonic All engines December 1, 1969 December 31, 1974 Greater than 75,000 Subsonic Without Pratt &Whitney JT3D engines December 1, 1969 December 1, 1973 Greater than 75,000 Subsonic With Pratt & Whitney JT3D engines December 1, 1969 December 31, 1974 Concorde – all weights Supersonic All engines October 13, 1977 January 1, 1980
(2) “Grandfathered” airplanes Airplane types not identified above are “grandfathered” airplanes and are permitted to continue normal operations without showing compliance with the requirements of part 36. For example, the twin-engine propeller-driven Convair 580 or Douglas DC-3 airplanes that first logged flight time before December 31, 1974, did not have to comply with the noise provisions of part 36 and may have received a standard airworthiness certificate under the provisions of §21.183 of part 21, or may have received a standa rd airworthiness certificate under the provisions of the regulations in effect at the time of certification without compliance with part 36.
201(a)(5) Airworth iness certificates §36.1(e)
(1) Requirements for issuance of airworthiness certificates:
An applicant must show compliance of individual airplanes with the requirements of part 36 prior to issuance of airworthiness certificates, as prescribed in §21.183 or 21.185 of part 21 (see paragraph 7-11 of Reference G4).
2) Commuter category airplanes:
Since airworthiness standards for commuter category airplanes became effective February 17, 1987, (under part 21, Amendment 21-59) there are no airplanes in this category with initial flight time before January 1, 1980. All commuter category airplanes are thus required to show compliance with the noise certification requirements of part 36.
201(a)(6) One-Stage limit §36.1(g) Page 36