# 14 CFR § 36.11: Acoustical change: Helicopters > Federal · Regulations · In force URL: https://www.frixlaw.com/law-library/statutes/ecfr-14-36.11 ## Section - **Citation:** 14 CFR § 36.11 - **Heading:** Acoustical change: Helicopters - **Jurisdiction:** Federal - **Kind:** Regulations - **Status:** In force - **Text as of:** September 22, 2026 - **Source:** Publisher's official text - **Location:** Title 14—Aeronautics and Space > CHAPTER I—FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION > SUBCHAPTER C—AIRCRAFT > PART 36—NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS CERTIFICATION > Subpart A—General ## Text This section applies to all helicopters in the primary, normal, transport, and restricted categories for which an acoustical change approval is applied for under § 21.93(b) of this chapter on or after March 6, 1986. Compliance with the requirements of this section must be demonstrated under appendix H of this part, or, for helicopters having a maximum certificated takeoff weight of not more than 7,000 pounds, compliance with this section may be demonstrated under appendix J of this part. (a) General requirements. Except as otherwise provided, for helicopters covered by this section, the acoustical change approval requirements are as follows: (1) In showing compliance with the requirements of appendix H of this part, noise levels must be measured, evaluated, and calculated in accordance with the applicable procedures and conditions prescribed in parts B and C of appendix H of this part. For helicopters having a maximum certificated takeoff weight of not more than 7,000 pounds that alternatively demonstrate compliance under appendix J of this part, the flyover noise level prescribed in appendix J of this part must be measured, evaluated, and calculated in accordance with the applicable procedures and conditions prescribed in parts B and C of appendix J of this part. (2) Compliance with the noise limits prescribed in section H36.305 of appendix H of this part must be shown in accordance with the applicable provisions of part D of appendix H of this part. For those helicopters that demonstrate compliance with the requirements of appendix J of this part, compliance with the noise levels prescribed in section J36.305 of appendix J of this part must be shown in accordance with the applicable provisions of part D of appendix J of this part. (b) Stage 1 helicopters. Except as provided in § 36.805(c), for each Stage 1 helicopter prior to a change in type design, the helicopter noise levels may not, after a change in type design, exceed the noise levels specified in section H36.305(a)(1) of appendix H of this part where the demonstration of compliance is under appendix H of this part. The tradeoff provisions under section H36.305(b) of appendix H of this part may not be used to increase any Stage 1 noise level beyond these limits. If an applicant chooses to demonstrate compliance under appendix J of this part, for each Stage 1 helicopter prior to a change in type design, the helicopter noise levels may not, after a change in type design, exceed the Stage 2 noise levels specified in section J36.305(a) of appendix J of this part. (c) Stage 2 helicopters. For each helicopter that is Stage 2 prior to a change in type design, after a change in type design the helicopter must either: (1) Remain a Stage 2 helicopter; or (2) Comply with Stage 3 requirements and remain a Stage 3 helicopter thereafter. (d) Stage 3 helicopters. For a helicopter that is a Stage 3 helicopter prior to a change in type design, the helicopter must remain a Stage 3 helicopter after a change in type design. [Doc. No. 26910, 57 FR 42854, Sept. 16, 1992, as amended by Amdt. 36-25, 69 FR 31234, June 2, 2004; Amdt. 36-30, 79 FR 12044, Mar. 4, 2014] ## Nearby sections - [14 CFR § 36.0 § 36.0 Applicability and statements of compliance for aircraft that do not conform to a type certificate.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.0.md) - [14 CFR § 36.1 § 36.1 Applicability and definitions.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.1.md) - [14 CFR § 36.2 § 36.2 Requirements as of date of application.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.2.md) - [14 CFR § 36.3 § 36.3 Compatibility with airworthiness requirements.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.3.md) - [14 CFR § 36.5 § 36.5 Limitation of part.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.5.md) - [14 CFR § 36.6 § 36.6 Incorporation by reference.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.6.md) - [14 CFR § 36.7 § 36.7 Acoustical change: Transport category large airplanes and jet airplanes.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.7.md) - [14 CFR § 36.9 § 36.9 Acoustical change: Propeller-driven small airplanes and propeller-driven commuter category airplanes.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.9.md) - [14 CFR § 36.11 § 36.11 Acoustical change: Helicopters.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.11.md) - [14 CFR § 36.13 § 36.13 Acoustical change: Tiltrotor aircraft.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.13.md) - [14 CFR § 36.101 § 36.101 Noise measurement and evaluation.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.101.md) - [14 CFR § 36.103 § 36.103 Noise limits.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.103.md) - [14 CFR § 36.105 § 36.105 Flight Manual Statement of Chapter 4 equivalency.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.105.md) - [14 CFR § 36.106 § 36.106 Flight Manual statement of Chapter 14 noise level equivalency.](https://www.frixlaw.com/law-library/statutes/ecfr-14-36.106.md) --- Source: Frix Law Library, https://www.frixlaw.com/law-library/statutes/ecfr-14-36.11. 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