Appendix C to Part 36 - Noise Levels for Transport Category and Turbojet Powered Airplanes Under § 36.201

Sec. C36.1Noise measurement and evaluation. C36.3Noise measuring points. C36.5Noise levels. C36.7Takeoff reference and test limitations. C36.9Approach reference and test limitations.

Section C36.1 Noise measurement and evaluation. Compliance with this appendix must be shown with noise levels measured and evaluated as prescribed, respectively, by appendix A and appendix B of this part, or under approved equivalent procedures.

Section C36.3 Noise measuring points. Compliance with the noise level standards of section C36.5 must be shown—

(a) For takeoff, at a point 21, 325 feet (6,500 meters) from the start of the takeoff roll on the extended centerline of the runway;

(b) For approach, at a point 6,562 feet (2,000 meters) from the threshold on the extended centerline of the runway; and

(c) For the sideline, at the point, on a line parallel to and 1,476 feet (450 meters) from the extended centerline of the runway, where the noise level after liftoff is greatest, except that, for an airplane powered by more than three turbojet engines, this distance must be 0.35 nautical miles for the purpose of showing compliance with Stage 1 or Stage 2 noise limits (as applicable).

Sec. C36.5Noise levels.

(a) Limits. Except as provided in paragraphs (b) and (c) of this section, it must be shown by flight test that the noise levels of the airplane, at the measuring points described in section C36.3, do not exceed the following (with appropriate interpolation between weights);

(1) Stage 1 noise limits for acoustical changes for airplanes regardless of the number of engines are those noise levels prescribed under § 36.7(c) of this part.

(2) Stage 2 noise limits for airplanes regardless of the number of engines are as follows:

(i) For takeoff. 108 EPNdB for maximum weights of 600,000 pounds or more, reduced by 5 EPNdB per halving of the 600,000 pounds maximum weight down to 93 EPNdB for maximum weights of 75,000 pounds and less.

(ii) For sideline and approach.—108 EPNdB for maximum weights of 600,000 pounds or more, reduced by 2 EPNdB per halving of the 600,000 pounds maximum weight down to 102 EPNdB for maximum weights of 75,000 pounds and less.

(3) Stage 3 noise limits are as follows:

(i) For takeoff.

(A) For airplanes with more than 3 engines. 106 EPNdB for maximum weights of 850,000 pounds or more, reduced by 4 EPNdB per halving of the 850,000 pounds maximum weight down to 89 EPNdB for maximum weights of 44,673 pounds or less;

(B) For airplanes with 3 engines—104 EPNdB for maximum weights of 850,000 pounds or more, reduced by 4 EPNdB per halving of the 850,000 pounds maximum weight down to 89 EPNdB for maximum weights of 63,177 pounds and less; and

(C) For airplanes with fewer than 3 engines—101 EPNdB for maximum weights of 850,000 pounds or more, reduced by 4 EPNdB per halving of the 850,000 pounds maximum weight down to 89 EPNdB for maximum weights of 106,250 pounds and less.

(ii) For sideline, regardless of the number of engines. 103 EPNdB for maximum weights of 882,000 pounds or more, reduced by 2.56 EPNdB per halving of the 882,000 pounds maximum weight down to 94 EPNdB for maximum weights of 77,200 pounds or less.

(iii) For approach, regardless of the number of engines—105 EPNdB for maximum weights of 617,300 pounds or more, reduced by 2.33 EPNdB per halving of the 617,300 pounds weight down to 98 EPNdB for maximum weights of 77,200 pounds or less.

(b) Tradeoffs. Except to the extent limited under §§ 36.7(c)(1) and 36.7(d)(3)(i)(B) of this part, the noise level limits prescribed in paragraph (a) of this section may be exceeded at one or two of the measuring points specified in section C36.3 of this appendix, if—

(1) The sum of the exceedances is not greater than 3 EPNdB;

(2) No exceedance is greater than 2 EPNdB; and

(3) The exceedances are completely offset by reductions at other required measuring points.

Sec. C36.7Takeoff Reference and Test Limitations.

(a) This section applies to all takeoff noise tests conducted under this appendix in showing compliance with this part.

(b) Takeoff power or thrust must be used from the start of takeoff roll to at least the following altitude above the runway:

(1) For Stage 1 airplanes and for Stage 2 airplanes that do not have turbojet engines with a bypass ratio of 2 or more, the following apply:

(i) For airplanes with more than three turbojet engines—700 feet (214 meters).

(ii) For all other airplanes—1,000 feet (305 meters).

(2) For Stage 2 airplanes that have turbojet engines with a bypass ratio of 2 or more and for Stage 3 airplane, the following apply:

(i) For airplanes with more than three turbojet engines—689 feet (210 meters).

(ii) For airplanes with three turbojet engines—853 feet (260 meters).

(iii) For airplanes with fewer than three turbojet engines—984 feet (300 meters).

(iv) For airplanes not powered by turbojet engines—1,000 feet (305 meters).

(c) Upon reaching the altitude specified in paragraph (b) of this section, the power or thrust may not be reduced below that needed to maintain level flight with one engine inoperative, or to maintain a four percent climb gradient, whichever power or thrust is greater.

(d) A constant takeoff configuration, selected by the applicant, must be maintained throughout the takeoff noise test, except that the landing gear may be retracted.

(e) For applications made for subsonic airplanes after September 17, 1971, and for Concorde airplanes, the following apply:

(1) For subsonic airplanes the test day speeds and the acoustic day reference speed must be the minimum approved value of V2+10 knots, or the all-engines-operating speed at 35 feet (for turbine engine powered airplanes) or 50 feet (for reciprocating engine powered airplanes), whichever speed is greater as determined under the regulations constituting the type certification basis of the airplane. These tests must be conducted at the test day speeds±3 knots. Noise values measured at the test day speeds must be corrected to the acoustic day reference speed.

(2) For Concorde airplanes, the test day speeds and the acoustic day reference speed must be 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, except that the reference speed may not exceed 250 knot. These tests must be conducted at the test day speeds ±3 knots. Noise values measured at the test day speeds must be corrected to the acoustic day reference speed.

(3) If a negative runway gradient exists in the direction of takeoff, performance and acoustic data must be corrected to the zero slope condition.

Sec. C36.9Approach reference and test limitations.

(a) This section applies to all approaches conducted in showing compliance with this part.

(b) The airplane's configuration must be that used in showing compliance with the landing requirements in the airworthiness regulations constituting the type certification basis of the airplane. If more than one configuration is used in showing compliance with the landing requirements in the airworthiness regulations constituting the type certification basis of the airplane, the configuration that is most critical from a noise standpoint must be used.

(c) The approaches must be conducted with a steady glide angle of 3°±0.5° and must be continued to a normal touchdown with no airframe configuration change.

(d) All engines must be operating at approximately the same power or thrust.

(e) For applications made for subsonic airplanes after September 17, 1971, and for Concorde airplanes, the following apply:

(1) For subsonic airplanes a steady approach speed, that is either 1.30 Vs +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 greatest, must be established and maintained over the approach measuring point.

(2) 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, must be established and maintained over the approach measuring point.

(3) A tolerance of ±3 knots may be used throughout the approach noise testing.