---
kind: "section"
citation: "14 C.F.R. § 36.11"
title: "14"
number: "36.11"
heading: "Acoustical change: Helicopters."
url: "https://uscodex.org/cfr/14/36.11"
---

# §36.11. Acoustical change: Helicopters.


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)](/cfr/14/21.93.md?p=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)](/cfr/14/36.805.md?p=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.

## Notes

### Amendments

[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]

### Authority

Authority: 42 U.S.C. 4321 et seq.; 49 U.S.C. 106(f), 40113, 44701-44702, 44704, 44715; sec. 305, Pub. L. 96-193, 94 Stat. 50, 57; E.O.11514, 35 FR 4247, 3 CFR, 1966-1970 Comp., p. 902.

### Source

Source: Docket No. 9337, 34 FR 18364, Nov. 18, 1969, unless otherwise noted.

### Amendments

[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]