a. Explanation
This section specifies the portions of the test and reference flight paths that are significant for computation of EPNLr (i.e., encompassing the 10 dB-down points), the symbols for airplane positions at different time intervals, and noise angles (which are equated between respective test and reference flight paths).
b. Supplemental Information
(1) Emission Angles: For the integrated method, each one-half second noise data record will define a separate noise emission angle. This angle will then define the location of each data record along the reference flight path. The distance between consecutive data records along the reference flight path divided by the reference path speed provides the time interval between reference data records. The reference duration of each of these data records can be determined by obtaining the average of the two intervals between the adjacent data records. (This may be different than 0.5 seconds). See section 6.6 of the Appended ICAO TM for discussion of time interval computations using the integrated method.
c. Procedures
(1) Elevation Angles: If the integrated method is used for lateral noise measurements and it is not possible to equate the elevation angle for the test flight path to that for the reference flight path after equating test and reference noise emission angles, then the elevation angle differences should be minimized using a method approved by the FAA.
262. Section A36.9.4.2.1
In paragraphs A36.9.4.2(a)(2) and (b)(2) the time tr1 is later (for Qr1Kr > Q1K) than t1 by two separate amounts:
(1) The time taken for the airplane to travel the distance Qr1Qr0 at a speed Vr less the time taken for it to travel Q1Q0 at V;
(2) The time taken for sound to travel the distance Qr1Kr - Q1K.
Note: For the flight paths described in paragraphs A36.9.4.2(a) and (b), the use of thrust or power cut-back will result in test and reference flight paths at full thrust or power and at cut-back thrust or power. Where the transient region between these thrust or power levels affects the final result, an interpolation must be made between them by an approved method such as that given in the current advisory circular for this part.
a. Explanation
This section specifies the factors that relate to the difference in the emission times between the reference flight path and the test flight path using the integrated method.
b. Supplementary Information
(1) See section 6.6 of the Appended ICAO TM for discussion of time interval computations using the integrated method.
c. Procedures
None
263. Section A36.9.4.2.2
The measured values of SPL(i)1 must be adjusted to the reference values SPL(i)r1 to account for the differences between measured and reference noise path lengths and between measured and reference atmospheric conditions, using the methods of section A36.9.3.2.1 of this appendix. A corresponding value of PNLr1 must be computed according to the method in section A36.4.2. Values of PNLr must be computed for times t0 through tn.
264. Section A36.9.4.2.3
For each value of PNLr1, a tone correction factor C1 must be determined by analyzing the reference values SPL(i)r using the methods of section A36.4.3 of this appendix, and added to PNLr1 to yield PNLTr1. Using the process described in this paragraph, values of PNLTr must be computed for times t0 through tn.
265. Section A36.9.4.3 Duration correction.
266. Section A36.9.4.3.1
The values of PNLTr corresponding to those of PNLT at each one-half second interval must be plotted against time (PNLTr1 at time tr1). The duration correction must then be determined using the method of section A36.4.5.1 of this appendix, to yield EPNLr.
a. Explanation
This section specifies the method of determining the duration correction needed to obtain EPNLr when using the “integrated” method.
b. Supplementary Information
(1) See section 6.6.7 of the appended ICAO TM for discussion of adjusted EPNL computations when using the “integrated” method.
c. Procedures
(1) Application of Band Sharing Adjustment for “Integrated” Method: See the Supplementary Information and Procedures presented in A36.4.4.2. This adjustment must be applied to the maximum PNLTr before calculation of the Duration Correction and EPNLr.
(2) Application of High-Altitude Site Jet Noise Adjustment for “Integrated” Method: When the Equivalent Procedure for use of high-altitude test sites (Elevation > 1200 feet MSL) is employed, and the “Integrated” adjustment method is used to determine EPNLr values, the adjustments must be applied either to the measured one-third octave band sound pressure levels, SPL(i,k), or to the adjusted one-third-octave-band sound pressure levels, SPL(i,k)r, throughout the entire 10 dB-down period. See Appendix 6 of the appended ICAO TM, for information on the equivalent procedure for testing at high-altitude sites.
267. Section A36.9.4.4 Source noise adjustment.
268. Section A36.9.4.4.1
A source noise adjustment, D3, must be determined using the methods of section A36.9.3.4 of this appendix.
269. Section A36.9.5 Flight Path Identification Positions.
Position Description
A Start of Takeoff roll B Lift-off C Start of first constant climb D Start of thrust reduction E Start of second constant climb F End of noise certification Takeoff flight path G Start of noise certification Approach flight path H Position on Approach path directly above noise measuring station I Start of level-off J Touchdown K Noise measurement point Kr Reference measurement point K1 Flyover noise measurement point K2 Lateral noise measurement point K3 Approach noise measurement point M End of noise certification Takeoff flight track O Threshold of Approach end of runway P Start of noise certification Approach flight track Q Position on measured Takeoff flight path corresponding to apparent PNLTM at station K See section A36.9.3.2 Qr Position on corrected Takeoff flight path corresponding to PNLTM at station K. See section A36.9.3.2 V airplane test speed Vr airplane reference speed
270. Section A36.9.6 Flight Path Distances.
Distanc e Unit Meaning
AB feet (meters) Length of takeoff roll. The distance along the runway between the start of takeoff roll and lift off.
AK feet (meters) Takeoff measurement distance. The distance from the start of roll to the takeoff noise measurement station along the extended center line of the runway.
AM feet (meters) Takeoff flight track distance. The distance from the start of roll to the takeoff flight track position along the extended center line of the runway after which the position of the airplane need no longer be recorded.
QK feet (meters) Measured noise path. The distance from the measured airplane position Q to station K.
QrKr feet (meters) Reference noise path. The distance from the reference airplane position Qr to station Kr.
K3H feet (meters) Airplane approach height. The height of the airplane above the approach measuring station.
OK3 feet (meters) Approach measurement distance. The distance from the runway threshold to the approach measurement station along the extended center line of the runway.
OP feet (meters) Approach flight track distance. The distance from the runway threshold to the approach flight track position along the extended center line of the runway after which the position of the airplane need no longer be recorded.
a. Explanation
This section specifies the flight path identification positions, their symbols, and associated units.
b. Supplemental Information
None
c. Procedures
None
271. - 289--RESERVED
290. Appendix B to Part 36-Noise Levels for Transport Category and Jet Airplanes Under § 36.103
Sec.
B36.1 Noise measurement and evaluation.
B36.2 Noise evaluation metric.
B36.3 Reference noise measurement points.
B36.4 Test noise measurement points.
B36.5 Maximum noise levels.
B36.6 Trade-offs.
B36.7 Noise certification reference procedures and conditions.
B36.8 Noise certification test procedures.
a. Explanation
Appendix B addresses the noise measurement and evaluation requirements, test and reference procedures, and maximum noise levels (noise limits) that FAA uses as the basis for assessment of compliance of subsonic transport category large airplanes and jet airplanes with part 36.
b. Supplemental Information
None
c. Procedures
None
291. Section B36.1 Noise Measurement and Evaluation.
Compliance with this appendix must be shown with noise levels measured and evaluated using the procedures of appendix A of this part, or under approved equivalent procedures.
a. Explanation
This section specifies that an applicant’s noise measurement and evaluation methods must conform to those of Appendix A or to FAA approved equivalent procedures for compliance with the maximum noise level (noise limit) requirements of part 36 section B36.5.
b. Supplemental Information
None
c. Procedure
None
292. Section B36.2 Noise Evaluation Metric.
The noise evaluation metric is the effective perceived noise level expressed in EPNdB, as calculated using the procedures of appendix A of this part.
a. Explanation
XIV. APPENDIX B TO part 36--NOISE LEVELS FOR TRANSPORT CATEGORY AND JET AIRPLANES UNDER § 36.103
This section specifies that the noise evaluation metric to be used in showing compliance with the noise limits is the Effective Perceived Noise Level (in units of EPNdB). See section A36.4 for a description of EPNL and the methodology for its calculation.
b. Supplemental Information
None
c. Procedures
None
293. Section B36.3 Reference Noise Measurement Points.
When tested using the procedures of this part, except as provided in section B36.6, an airplane may not exceed the noise levels specified in section B36.5 at the following points on level terrain:
(a) Lateral full-power reference noise measurement point:
(1) For jet airplanes: the point on a line parallel to and 1,476 feet (450 m) from the runway centerline, or extended centerline, where the noise level after lift-off is at a maximum during takeoff.
For the purpose of showing compliance with Stage 1 or Stage 2 noise limits for an airplane powered by more than three jet engines, the distance from the runway centerline must be 0.35 nautical miles (648 m). For jet airplanes, when approved by the FAA, the maximum lateral noise at takeoff thrust may be assumed to occur at the point (or its approved equivalent) along the extended centerline of the runway where the airplane reaches 985 feet (300 meters) altitude above ground level. A height of 1427 feet (435 meters) may be assumed for Stage 1 or Stage 2 four engine airplanes. The altitude of the airplane as it passes the noise measurement points must be within +328 to -164 feet (+100 to -50 meters) of the target altitude. For airplanes powered by other than jet engines, the altitude for maximum lateral noise must be determined experimentally.
(2) For propeller-driven airplanes: the point on the extended centerline of the runway above which the airplane, at full takeoff power, reaches a height of 2,133 feet (650 meters). For tests conducted before August 7, 2002, an applicant may use the measurement point specified in section B36.3(a)(1) as an alternative.
(b) Flyover reference noise measurement point: the point on the extended centerline of the runway that is 21,325 feet (6,500m) from the start of the takeoff roll;
(c) Approach reference noise measurement point: the point on the extended centerline of the runway that is 6,562 feet (2,000 m) from the runway threshold. On level ground, this corresponds to a position that is 394 feet (120 m) vertically below the 3° descent path, which originates at a point on the runway 984 feet (300 m) beyond the threshold.
a. Explanation
This section specifies the locations of reference noise measurement points for flyover, lateral and approach noise measurements.
b. Supplemental Information
None
c. Procedures
None
294. Section B36.4 Test noise measurement points.
(a) If the test noise measurement points are not located at the reference noise measurement points, any corrections for the difference in position are to be made using the same adjustment procedures as for the differences between test and reference flight paths.
(b) The applicant must use a sufficient number of lateral test noise measurement points to demonstrate to the FAA that the maximum noise level on the appropriate lateral line has been determined. For jet airplanes, simultaneous measurements must be made at one test noise measurement point at its symmetrical point on the other side of the runway. Propeller-driven airplanes have an inherent asymmetry in lateral noise. Therefore, simultaneous measurements must be made at each and every test noise measurement point at its symmetrical position on the opposite side of the runway. The measurement points are considered to be symmetrical if they are longitudinally within 33 feet (–10 meters) of each other.
a. Explanation
This section specifies FAA requirements when test noise measurement points are not located at reference noise measurement positions and the criteria for selection of lateral noise measurement points for jet airplanes and propeller-driven airplanes.
b. Supplemental Information
(1) Measured Lateral Noise Levels: Measured lateral noise levels may not be the same at symmetrical noise measurement points even when the data are adjusted for airplane position (for flight directly over the extended runway centerline). The direction of engine or propeller rotation may be an important factor in the non-symmetrical nature of measured lateral noise. Inlet shielding may cause turbojet-powered airplanes to exhibit 1-2 dB differences in lateral noise levels. Propeller-driven airplanes may exhibit differences in lateral noise levels in excess of 6 dB. Due to their inherent lateral noise asymmetry, for propeller-driven airplanes, section B36.4 requires that simultaneous measurements be made at each and every test noise measurement point at its symmetrical position on the opposite side of the runway.
(2) Maximum Lateral Noise Levels: An applicant may conduct noise measurements at several altitudes over symmetrically located noise measurement points in accordance with an FAA approved noise compliance demonstration plan to determine the maximum lateral noise levels. Typically, a 2nd order curve fit through the adjusted noise levels as a function of airplane altitude is sufficient to determine the maximum average lateral noise level and the altitude at which it occurred. Valid noise certification test data cannot be discarded.
(3) Maximum Lateral Noise Levels (Alternative Procedure): Section B36.3(a)(1) contains an alternative procedure whereby the maximum lateral noise level may be assumed to occur at the point (or its approved equivalent) along the extended centerline of the runway where the airplane reaches 985 feet (1427 feet for Stage 1 or Stage 2 four engine airplanes) altitude above ground level. Section 2.1.3.2 of the appended ICAO Environmental Technical Manual describes a similar equivalent procedure. However, unlike the ICAO TM equivalent procedure, use of the alternative procedure contained in section B36.3(a)(1) is not restricted to engines with bypass ratios of more than 2. Prior approval from the FAA is required to use this alternative procedure.
c. Procedure
(1) Applicant’s Responsibility: An applicant must include proposed equivalent procedures for lateral noise measurements in a noise compliance demonstration plan for FAA review and approval.
295. Section B36.5 Maximum Noise Levels
Except as provided in section B36.6 of this appendix, maximum noise levels, when determined in accordance with the noise evaluation methods of appendix A of this part, may not exceed the following:
(a) For acoustical changes to Stage 1 airplanes, regardless of the number of engines, the noise levels prescribed under § 36.7(c) of this part.
(b) For any Stage 2 airplane regardless of the number of engines:
(1) Flyover: 108 EPNdB for maximum weight of 600,000 pounds or more; for each halving of maximum weight (from 600,000 pounds), reduce the limit by 5 EPNdB; the limit is 93 EPNdB for a maximum weight of 75,000 pounds or less.
(2) Lateral and approach: 108 EPNdB for maximum weight of 600,000 pounds or more; for each halving of maximum weight (from 600,000 pounds), reduce the limit by 2 EPNdB; the limit is 102 EPNdB for a maximum weight of 75,000 pounds or less.
(c) For any Stage 3 airplane:
(1) Flyover.
(i)For airplanes with more than 3 engines: 106 EPNdB for maximum weight of 850,000 pounds or more; for each halving of maximum weight (from 850,000 pounds), reduce the limit by 4 EPNdB; the limit is 89 EPNdB for a maximum weight of 44,673 pounds or less;
(ii) For airplanes with 3 engines: 104 EPNdB for maximum weight of 850,000 pounds or more;
for each halving of maximum weight (from 850,000 pounds), reduce the limit by 4 EPNdB; the limit is 89 EPNdB for a maximum weight of 63,177 pounds or less; and
(iii) For airplanes with fewer than 3 engines: 101 EPNdB for maximum weight of 850,000 pounds or more; for each halving of maximum weight (from 850,000 pounds), reduce the limit by 4 EPNdB; the limit is 89 EPNdB for a maximum weight of 106,250 pounds or less.
(2) Lateral, regardless of the number of engines: 103 EPNdB for maximum weight of 882,000 pounds or more; for each halving of maximum weight (from 882,000 pounds), reduce the limit by
2.56 EPNdB; the limit is 94 EPNdB for a maximum weight of 77,200 pounds or less.
(3) Approach, regardless of the number of engines: 105 EPNdB for maximum weight of 617,300 pounds or more; for each halving of maximum weight (from 617,300 pounds), reduce the limit by 2.33 EPNdB; the limit is 98 EPNdB for a maximum weight of 77,200 pounds or less.
a. Explanation
This section specifies maximum noise levels (noise limits) at flyover, lateral and approach reference noise measurement points as a function of airplane maximum takeoff gross weight. For the flyover noise measurement point, the maximum noise levels (noise limits) are specified for the number of airplane engines as well as maximum weight.
b. Supplemental Information
(1) Stage Definitions: Definitions of Stage 1, Stage 2, and Stage 3 airplanes are given in section
36.1 of Subpart A.
(2) Acoustical Change: Requirements for FAA approval of Stage 1, Stage 2 and Stage 3 airplane Acoustical Changes, applied for under, Part 21.93(b) are specified in section 36.7 of Subpart A.
c. Procedures
(1) Maximum Noise Levels (Noise Limits): Flyover, lateral and approach maximum noise levels (noise limits) for Stage 2 and Stage 3 airplanes are given below. FAA uses Equations A through E to determine these levels (limits).
Stage No. of Engines Maximum Weight (MTOGW), pounds Flyover Limit, dB Lateral Limit, dB Approach Limit, dB 2 Any number 75,000 and less 93.0 102.0 102.0 2 Any number between 75,000 and 600,000 See Eqn. A See Eqn. B See Eqn. B 2 Any number 600,000 and more 108.0 108.0 108.0
3 Fewer than 3 106,250 and less 89.0
3 Fewer than 3 between 106,250 and 850,000 See Eqn. C 3 Fewer than 3 850,000 and more 101 3 Three 63,177 and less 89.0 3 Three between 63,177 and 850,000 See Eqn. C 3 Three 850,000 and more 104.0 3 More than 3 44,673 and less 89.0 3 More than 3 between 44,673 and 850,000 See Eqn. C 3 More than 3 850,000 and more 106.0 3 Any number 77,200 and less 94.0 3 Any number between 77,200 and 882,000 See Eqn. D 3 Any number 882,000 and more 103.0 3 Any number 77,200 and less 98.0 3 Any number between 77,200 and 617,300 See Eqn. E 3 Any number 617,300 and more 105.0
Eqn. A: Limit Flyover EPNL = 93.0 + 5.0 [(log (Maximum weight /75,000)) ÷ (log 2.0)] Eqn. B: Limit Approach EPNL = 102.0 + 2.0 [(log (Maximum weight /75,000)) ÷ (log 2.0)] Eqn. C: Limit Flyover EPNL = 89.0 + 4.0 [(log (Maximum weight / ‘K’)) ÷ (log 2.0)], where:
Number of Engines Eqn. C ‘K’ value Fewer than 3 106,250 Three 63,177 More than 3 44,673
Eqn. D: Limit Lateral EPNL = 94.0 + 2.56 [(log (Maximum weight /77,200)) ÷ (log 2.0)] Eqn. E: Limit Approach EPNL = 98.0 + 2.33 [(log (Maximum weight /77,200)) ÷ (log 2.0)]
Note: Maximum weights are considered to be the certificated maximum takeoff gross weight (MTOGW) at brake release for Flyover, Lateral and Approach noise measurement points
296. Section B36.6 Trade-Offs.
Except when prohibited by sections 36.7(c)(1) and 36.7(d)(1)(ii), if the maximum noise are exceeded at any one or two measurement points, the following conditions must be met:
(a) The sum of the exceedance(s) may not be greater than 3 EPNdB;
(b) Any exceedance at any single point may not be greater than 2 EPNdB, and
(c) Any exceedance(s) must be offset by a corresponding amount at another point or points.
a. Explanation
This section specifies the noise level tradeoffs an applicant may use in demonstrating Stage 2 and Stage 3 compliance with part 36.
b. Supplemental Information
(1) Tradeoff Provisions: Tradeoffs are permitted in determining compliance with the Stage 2 and Stage 3 maximum noise level (noise limit) requirements of part 36 because of the cumulative aspects of noise
exposure. Limited “exceedances” to the flyover, lateral and approach noise limits are acceptable when compensated by noise reductions at the other noise measurement points,
(2) Stage 1 Airplanes: FAA does not permit an applicant to use tradeoffs to increase Stage 1 airplane flyover, lateral or approach noise levels.
c. Procedures
(1) Use of Tradeoffs: The following example demonstrates how tradeoffs are used:
Airplane Classification = Stage 3 Number of Engines = 3 Airplane MTOGW = 300,000 pounds Stage 3 Noise Limits:
Flyover = 97.99 EPNdB Lateral = 99.01 EPNdB Approach = 102.56 EPNdB Demonstrated Noise Levels:
Flyover = 99.83 EPNdB Lateral = 98.19 EPNdB Approach = 101.54 EPNdB Total Exceedance:
Flyover = +1.84 EPNdB Total Reduction:
Lateral + Approach = (-0.82) + (-1.02) = 0 EPNdB
This airplane complies with part 36 maximum noise level (noise limit) requirements for a Stage 3 airplane through the use of tradeoffs. Note that, as illustrated by this example, the tradeoff analysis is typically conducted to two decimal places.
297. Section B36.7 Noise Certification Reference Procedures and Conditions.
298. Section B36.7(a) General conditions:
(1) All reference procedures must meet the requirements of section 36.3 of this part.
(2) Calculations of airplane performance and flight path must be made using the reference procedures and must be approved by the FAA.
(3) Applicants must use the takeoff and approach reference procedures prescribed in paragraphs (b) and (c) of this section.
(4) [Reserved]
(5) The reference procedures must be determined for the following reference conditions. The reference atmosphere is homogeneous in terms of temperature and relative humidity when used for the calculation of atmospheric sound attenuation coefficients.
(i) Sea level atmospheric pressure of 2116 pounds per square foot (psf) (1013.25 hPa);
(ii) Ambient sea-level air temperature of 77°F (25°C, i.e. ISA+10°C);
(iii) Relative humidity of 70 per cent;
(iv) Zero wind.
(v) In defining the reference takeoff flight path(s) for the takeoff and lateral noise measurements, the runway gradient is zero.
a. Explanation
This section specifies the airworthiness criteria, reference atmospheric conditions and runway gradient to be used for calculation of takeoff and approach reference procedures
b. Supplemental Information
(1) Reference Conditions and Procedures: Uniform reference conditions and procedures are required in order to have a common basis of comparison of the values of EPNLr which are obtained for airplanes tested under a range of conditions, with the part 36 noise limits.
(2) Equivalent Procedures: The FAA does not permit equivalent procedures for certification reference procedures (e.g., 3o glide path).
c. Procedures
None
299. Section B36.7(b) Takeoff reference procedure:
The takeoff reference flight path is to be calculated using the following:
300. Section B36.7(b)(1)
(1) Average engine takeoff thrust or power must be used from the start of takeoff to the point where at least the following height above runway level is reached. The takeoff thrust/power used must be the maximum available for normal operations given in the performance section of the airplane flight manual under the reference atmospheric conditions given in section B36.7(a)(5).
(i) For Stage 1 airplanes and for Stage 2 airplanes that do not have jet engines with a bypass ratio of 2 or more, the following apply:
(A): For airplanes with more than three jet engines--700 feet (214 meters).
(B): For all other airplanes--1,000 feet (305 meters).
(ii) For Stage 2 airplanes that have jet engines with a bypass ratio of 2 or more and for Stage 3 airplanes, the following apply:
(A): For airplanes with more than three engines--689 feet (210 meters).
(B): For airplanes with three engines--853 feet (260 meters).
(C) For airplanes with fewer than three engines--984 feet (300 meters).
a. Explanation
This section specifies the reference engine thrust (power) and minimum altitude for thrust (power) reduction that an applicant must use to calculate reference flight paths for Stage 1, Stage 2, and Stage 3 airplanes.
b. Supplemental Information
(1) Takeoff Without Thrust (Power) Reduction: Average engine takeoff thrust (power) must be used throughout the takeoff flight path without reducing thrust (power). Some applicants find that it is simpler to test with takeoff thrust (power) only - when values of EPNLr do not exceed part 36 maximum noise levels (noise limits). This is especially true for turboprop powered transport category airplanes. On or after August 7, 2002, lateral noise levels must be determined using a flight path for which takeoff thrust (power) is used throughout, i.e., thrust (power) reduction will not be permitted.
c. Procedures
(1) Reference Takeoff Procedure With Thrust (Power) Reduction: For calculation of a takeoff reference procedure that includes a thrust (power) reduction, average engine takeoff thrust (power) is used at the point of brake release and maintained as the airplane proceeds along the runway, rotates and lifts off according to normal airworthiness requirements. The airplane then retracts the landing gear, and establishes a first segment
climb gradient prior to reaching an appropriate altitude for thrust (power) reduction. Beyond this altitude the second segment climb gradient is established at reduced thrust (power) and maintained throughout the 10 dB- down period. Aerodynamic control surfaces (including flap position) are maintained constant throughout this procedure. See section 2.2.1 of the appended ICAO TM.
(2) Thrust (Power) Reduction Altitude: The thrust (power) reduction altitude proposed by the applicant must be equal to or greater than the minimum altitudes specified in section B36.7(b)(1).
Note: FAA policy requires an applicant to take into account the following two airplane operational factors in determining an altitude for thrust (power) reduction within a reference flight path (Also see section 2.2.1 of the appended ICAO TM):
(i) A one-second delay to account for pilot recognition and response prior to movement of the throttles to the reduced thrust (power) position.
(ii) An average period of time for an airplane’s engines to spool-down from takeoff thrust (power) to reduced thrust (power).
(3) Spool-Down Tests: FAA-witnessed flight tests of an airplane to be used for noise certification measurements are required to obtain at least six acceptable spool-down times of each engine from average engine takeoff thrust (power) to reduced thrust (power) at the lowest maximum weight to be certified. These tests should be conducted at altitudes approximately 3000 feet AGL and at airspeeds comparable to reference airspeeds as defined in section B36.7(b)(4). An applicant's proposal for these tests must be included in a noise compliance demonstration plan.
301. Section B36.7(b)(2)
Upon reaching the height specified in paragraph (b)(1) of this section, airplane thrust or power must not be reduced below that required to maintain either of the following, whichever is greater:
(i) A climb gradient of 4 per cent; or
(ii) In the case of multi-engine airplanes, level flight with one engine inoperative.
a. Explanation
This section specifies the minimum thrust (power) that is required after an airplane has reached a minimum altitude for thrust reduction as required by section B36.7(b)(1).
b. Supplemental Information
(1) Lapse Rate Effect on Engine Thrust (Power): The climb gradient after reducing thrust may decrease because, for a constant thrust (power) setting, as the airplane altitude increases there is a decrease in engine thrust (power) due to lapse rate.
(2) Single Engine Airplane Reduced Thrust (Power) Requirements: For single engine airplanes, the minimum reduced thrust (power) required is that which is necessary to maintain a 4% climb gradient.
c. Procedures
None
302. Section B36.7(b)(3)
For the purpose of determining the lateral noise level, the reference flight path must be calculated using full takeoff power throughout the test run without a reduction in thrust or power. For tests conducted before August 7, 2002, a single reference flight path that includes thrust cutback in