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
accordance with paragraph (b)(2) of this section, is an acceptable alternative in determining the lateral noise level.
a. Explanation
This section specifies criteria for an applicant to calculate lateral reference flight paths.
b. Supplemental Information
None
c. Procedures
None
303. Section B36.7(b)(4)
The takeoff reference speed is the all-engine operating takeoff climb speed selected by the applicant for use in normal operation; this speed must be at least V2+10kt (V2+19km/h) but may not be greater than V2+20kt (V2+37km/h). This speed must be attained as soon as practicable after lift-off and be maintained throughout the takeoff noise certification test. For Concorde airplanes, the test day speeds and the acoustic day reference speed are the minimum approved value of V2 +35 knots, or the all-engines-operating speed at 35 feet, whichever speed is greater as determined under the regulations constituting the type certification basis of the airplane; this reference speed may not exceed 250 knots. For all airplanes, noise values measured at the test day speeds must be corrected to the acoustic day reference speed.
a. Explanation
This section specifies airspeed criteria that an applicant must use to calculate the takeoff reference flight path of subsonic transport category large airplanes, jet airplanes and Concorde airplanes.
b. Supplemental Information
(1) Supersonic Airplanes: This AC does not address the noise certification requirements for supersonic transport category airplanes, other than Concorde (See section 1d).
c. Procedures
(1) V2 Takeoff Airspeed: Criteria for determining V2 takeoff airspeeds are specified in 14 CFR Part
25.107 “Takeoff Speeds”.
(2) Applicant's Responsibility: The applicant is responsible for determination of appropriate takeoff reference airspeeds for airplane maximum weights.
304. Section B36.7(b)(5)
The takeoff configuration selected by the applicant must be maintained constantly throughout the takeoff reference procedure, except that the landing gear may be retracted. Configuration means the center of gravity position, and the status of the airplane systems that can affect airplane performance or noise. Examples include, the position of lift augmentation devices, whether the APU is operating, and whether air bleeds and engine power take-offs are operating;
a. Explanation
None
b. Supplemental Information
(1) Applicant’s Options for Selection of Takeoff Configuration: The noise certification takeoff configuration that is selected by the applicant must be within the airworthiness approved configurations, as recorded in the AFM. Example: If the applicant has certificated flap settings 2, 5 and 10 and those settings are identified in the AFM, then they are valid options for noise measurements during takeoff. Flap setting 0 is not a valid option in this example. Noise certification compliance for a configuration that is different from the tested configuration may require re-testing or an equivalency finding by the FAA.
c. Procedure
(1) Applicant's Responsibility: An applicant is responsible for demonstrating that an appropriate airplane takeoff configuration is selected and maintained for the calculation of the reference takeoff procedure.
305. Section B36.7(b)(6)
The weight of the airplane at the brake release must be the maximum takeoff weight at which the noise certification is requested, which may result in an operating limitation as specified in § 36.1581(d); and
a. Explanation
This section specifies criteria for defining a reference maximum takeoff weight of an airplane.
b. Supplemental Information
(1) Part 36 section 36.1581 Requirements: An airplane reference maximum takeoff weight for noise certification which is less than the maximum weight established under applicable airworthiness requirements must be furnished as an operating limitation in the limitations section of the airplane flight manual.
c. Procedure
(1) Applicant’s Responsibility: An applicant must define and obtain FAA approval of an airplane maximum takeoff weight to calculate reference EPNL values.
306. Section B36.7(b)(7)
The average engine is defined as the average of all the certification compliant engines used during the airplane flight tests, up to and during certification, when operating within the limitations and according to the procedures given in the Flight Manual. This will determine the relationship of thrust/power to control parameters (e.g., N1 or EPR). Noise measurements made during certification tests must be corrected using this relationship.
a. Explanation
This section specifies criteria for defining an airplane’s average engine thrust (power) characteristics.
b. Supplemental Information
None
c. Procedure
(1) Applicant’s Responsibility: An applicant must define and obtain FAA approval of an airplane’s average engine thrust (power) characteristics to calculate reference EPNL values.
307. Section B36.7(c) Approach reference procedure:
The approach reference flight path must be calculated using the following:
308. Section B36.7(c)(1)
The airplane is stabilized and following a 3° glide path;
a. Explanation
This section specifies the reference conditions that an applicant must use in calculating an approach reference flight path.
b. Supplemental Information
None
c. Procedures
None
309. Section B36.7(c)(2)
For subsonic airplanes, a steady approach speed of VREF + 10 kts (VREF + 19 km/h) with thrust and power stabilized must be established and maintained over the approach measuring point. VREF is the reference landing speed, which is defined as the speed of the airplane, in a specified landing configuration, at the point where it descends through the landing screen height in the determination of the landing distance for manual landings. For Concorde airplanes, a steady approach speed that is either the landing reference speed + 10 knots or the speed used in establishing the approved landing distance under the airworthiness regulations constituting the type certification basis of the airplane, whichever speed is greater. This speed must be established and maintained over the approach measuring point.
a. Explanation
This section specifies the criteria that an applicant must use to determine reference approach airspeeds for subsonic transport category large airplanes and jet airplanes.
b. Supplemental Information
None
c. Procedures
None
310. Section B36.7(c)(3)
The constant approach configuration used in the airworthiness certification tests, but with the landing gear down, must be maintained throughout the approach reference procedure;
a. Explanation
None
b. Supplemental Information
(1) Approach Airworthiness Certification: Under the airworthiness regulations, airplanes are frequently airworthiness-certificated for more than one approach configuration. Such configurations may include:
(i) Multiple approach/landing flap settings and landing weights;
(ii) In-flight operable APU;
(iii) Environmental Control system operational conditions;
(iv) Engine bleed valve operational conditions.
The configuration that is most critical from a noise standpoint is the configuration that must be used for determination of reference approach EPNL values.
(2) Emergency Approach Configuration: Some airplanes are equipped with emergency in-flight operable equipment such as emergency air-turbine driven generators and emergency air-turbine driven hydraulic pumps. Emergency equipment operation is not a part of normal approach airworthiness approved configurations that require part 36 compliance.
(3) Restricted Configurations: On some airplanes, flap settings may be limited in order to comply with part 36 maximum noise levels (See section B36.5). For Stage 3 airplanes that require a flap limitation in order to comply with part 36, the installation of soft-guards and incorporation of appropriate AFM limitations are required. In addition, placards may be installed to provide appropriate information to the flight crew. Soft-guards make it obvious that limited flap settings are not to be used for normal operation, and would indicate any use of the unapproved settings by deformation of the soft-guard. For safety purposes, at the discretion of the flight crew, soft-guards allow use of noise restricted flap settings (that are airworthiness approved) for emergency conditions.
c. Procedures
(1) Applicant’s Responsibility: An applicant is responsible for demonstrating that an appropriate airplane configuration is selected and maintained in determining a noise certification approach reference procedure. This includes evaluating which approach configuration is most critical for approach noise certification and identifying that critical configuration in a noise certification compliance demonstration plan.
311. Section B36.7(c)(4)
The weight of the airplane at touchdown must be the maximum landing weight permitted in the approach configuration defined in paragraph (c)(3) of this section at which noise certification is requested, except as provided in § 36.1581(d) of this part; and
a. Explanation
This section specifies criteria for defining the reference maximum landing weight of an airplane for noise certification.
b. Supplemental Information
None
c. Procedures
None
312. Section B36.7(c)(5)
The most critical configuration must be used; this configuration is defined as that which produces the highest noise level with normal deployment of aerodynamic control surfaces including lift and drag producing devices, at the weight at which certification is requested. This configuration includes all those items listed in section A36.5.2.5 of appendix A of this part that contribute to the noisiest continuous state at the maximum landing weight in normal operation.
a. Explanation
This section specifies criteria for defining the reference configuration of an airplane for noise certification.
b. Supplemental Information
None
c. Procedures
(1) Most Critical Approach Configuration: An applicant must determine the most noise-critical configuration at the airplane’s maximum landing weight by evaluation of appropriate measured noise data and/or experience, or similarity with other airplane models. The results of this evaluation must include the effects of items listed in section A36.5.2.5.
Note: Example items warranting consideration are as follows:
(i) Flaps extended to the extreme approved landing flap position (e.g., 30º flaps) for turbojet airplanes and to the least approved landing flap position (e. g. 10° flaps) for turbo-propeller airplanes;
(ii) A/C (Environmental Control System) operating;
(iii) Landing gear extended;
(iv) Operation of an APU in-flight;
(v) Maximum approved landing gross weight, and
(vi) Inter-compressor bleed trimmed to maximum trim stop.
313. Section B36.8 Noise Certification Test Procedures
314. Section B36.8(a)
All test procedures must be approved by the FAA.
a. Explanation
This section specifies a requirement for FAA approval of an applicant’s proposals for airplane noise certification test procedures and noise measurements.
b. Supplemental Information
(1) Test Witnessing: An FAA observer, or appropriately delegated designee, must witness airplane noise certification tests to ensure compliance with a FAA approved noise certification compliance demonstration plan. (See paragraph 6-3(f) of reference 7 of this AC.)
c. Procedures
(1) Constant Configuration: A flight crew must not modify the takeoff or approach configurations during noise certification testing. They must set the airplane configuration (including engine thrust (power), flap position, APU and A/C operation, gear position, etc.) in sufficient time to stabilize all conditions prior to the initial 10 dB-down point, and maintain that configuration constantly until after the final 10 dB-down point.
Note: throttle movement during the noise measurement is not permitted, except as required by the pilot-in-command to ensure safety. If this occurs, the noise level certification test condition is invalid, and is to be repeated.
315. Section B36.8(b)
The test procedures and noise measurements must be conducted and processed in an approved manner to yield the noise evaluation metric EPNL, in units of EPNdB, as described in appendix A of this part.
316. Section B36.8(c)
Acoustic data must be adjusted to the reference conditions specified in this appendix using the methods described in appendix A of this part. Adjustments for speed and thrust must be made as described in section A36.9 of this part.
317. Section B36.8(d)
If the airplane’s weight during the test is different from the weight at which noise certification is requested, the required EPNL adjustment may not exceed 2 EPNdB for each takeoff and 1 EPNdB for each approach. Data approved by the FAA must be used to determine the variation of EPNL with weight for both takeoff and approach test conditions. The necessary EPNL adjustment for variations in approach flight path from the reference flight path must not exceed 2 EPNdB.
a. Explanation
This section specifies limits on EPNL adjustments due to differences between takeoff and approach test weight and the maximum weight at which noise certification is requested.
b. Supplemental Information
(1) Applicability of section B36.8(d): The requirements of section B36.8(d) do not apply when approved equivalent noise measurement and evaluation procedures are used to develop Noise-Power-Distance (NPD) data for airplane noise certification compliance. (See sections 2.1.2 and 3.1.2 of the appended ICAO TM).
c. Procedures
None
318. Section B36.8(e)
For approach, a steady glide path angle of 3° ± 0.5° is acceptable.
a. Explanation
This section specifies limits on airplane deviations from a 3° glide path during approach noise certification measurements.
b. Supplemental Information
(1) Applicability of section B36.8(e): The requirements of B36.8(e) regarding limits on glide path deviations do not apply when approved equivalent noise measurement and evaluation procedures are used to develop Noise-Power- Distance (NPD) data for airplane noise certification compliance (See sections 2.1.2,
2.1.1.3, 2.1.1.4, and 3.1.2(a) of the appended ICAO TM).
c. Procedures
(1) Applicant's Responsibility: The applicant is responsible either for ensuring that approach tests are conducted within specified glide path tolerances, or for obtaining approval for equivalent noise measurement and evaluation procedures if testing is not to be conducted within specified tolerances.
319. Section B36.8(f)
If equivalent test procedures different from the reference procedures are used, the test procedures and all methods for adjusting the results to the reference procedures must be approved by the FAA. The adjustments may not exceed 16 EPNdB on takeoff and 8 EPNdB on approach. If the adjustment is more than 8 EPNdB on takeoff, or more than 4 EPNdB on approach, the resulting numbers must be more than 2 EPNdB below the limit noise specified in section B36.5.
a. Explanation
None
b. Supplemental Information
None
c. Procedures
(1) Integrated Method: An applicant must use the “integrated method”, specified in section A36.9.4, when approved equivalent noise measurement and evaluation procedures result in EPNdB adjustments greater than 8 EPNdB for takeoff and 4 EPNdB for approach (See requirements specified in section A36.9.1.2).
320. Section B36.8(g)
During takeoff, lateral, and approach tests, the airplane variation in instantaneous indicated airspeed must be maintained within +3% of the average airspeed between the 10 dB-down points. This airspeed is determined by the pilot’s airspeed indicator. However, if the instantaneous indicated airspeed exceeds +3 kt (+5.5 km/h) of the average airspeed over the 10 dB-down points, and is determined by the FAA representative on the flight deck to be due to atmospheric turbulence, then the flight so affected must be rejected for noise certification purposes.
Note: Guidance material on the use of equivalent procedures is provided in the current advisory circular for this part.
a. Explanation
None
b. Supplemental Information
(1) Airspeed Variations: Possible causes and potential effects of airspeed variations during noise certification measurements are discussed under section A36.2.2.2(f) of this AC.
c. Procedures
None
321. - 349. [RESERVED]
350. PART A - GENERAL
351. Section F36.1 Scope [To be completed later.]
352. PART B - NOISE MEASUREMENT
353. Section F36.101 General Test Conditions [To be completed later.]
354. Section F36.103 Acoustical Measurement System [To be completed later.]
355. Section F36.105 Sensing, Recording, and Reproducing Equipment
356. Section F36.107 Noise Measurement Procedures [To be completed later.]
357. Section F36.109 Data Recording, Reporting, and Approval [To be completed later.
358. Section F36.111 Flight Procedures [To be completed later.]
359. PART C - DATA CORRECTION
360. Section F36.201 Correction of Data [To be completed later.]
361. Section F36.203 Validity of Results [To be completed later.]
362. PART D - NOISE LIMITS
363. Section F36.301 Aircraft Noise Limits [To be completed later.]
364. - 374. [RESERVED]
XV. 14 CFR PART 36 APPENDIX F. FLYOVER NOISE REQUIREMENTS FOR PROPELLER - DRIVEN
SMALL AIRPLANE AND PROPELLER-DRIVEN, COMMUTER CATEGORY AIRPLANE CERTIFICATION TESTS PRIOR TO DECEMBER 22, 1988