AC 36-4C

116. Section A36.2.2.2(f)76

117. Section A36.2.2.2(g)77

118. Section A36.2.2.377

119. Section A36.2.2.479

120. Section A36.2.3 Flight path measurement80

121. Section A36.2.3.180

122. Section A36.2.3.281

123. Section A36.2.3.383

124. Section A36.3 Measurement of Airplane Noise Received on the Ground83

125. Section A36.3.1 Definitions84

126. Section A36.3.1.184

127. Section A36.3.1.284

128. Section A36.3.1.384

129. Section A36.3.1.484

130. Section A36.3.1.584

131. Section A36.3.1.684

132. Section A36.3.1.785

133. Section A36.3.1.885

134. Section A36.3.1.985

135. Section A36.3.1.1085

136. Section A36.3.1.1185

137. Section A36.3.1.1285

138. Section A36.3.1.1385

139. Section A36.3.1.1485

140. Section A36.3.1.1585

141. Section A36.3.1.1686

142. Section A36.3.2 Reference environmental conditions86

143. Section A36.3.2.186

144. Section A36.3.3 General86

145. Section A36.3.3.187

146. Section A36.3.3.288

147. Section A36.3.4 Windscreen88

148. Section A36.3.4.188

149. Section A36.3.5 Microphone system88

150. Section A36.3.5.188

151. Section A36.3.5.288

152. Section A36.3.5.389

153. Section A36.3.5.489

154. Section A36.3.6 Recording and reproducing systems91

155. Section A36.3.6.191

156. Section A36.3.6.291

157. Section A36.3.6.391

158. Section A36.3.6.492

159. Section A36.3.6.592

160. Section A36.3.6.692

161. Section A36.3.6.792

162. Section A36.3.6.892

163. Section A36.3.6.992

164. Section A36.3.7 Analysis systems94

165. Section A36.3.7.194

166. Section A36.3.7.294

167. Section A36.3.7.394

168. Section A36.3.7.494

169. Section A36.3.7.595

170. Section A36.3.7.695

171. Section A36.3.7.795

172. Section A36.3.8 Calibration systems96

173. Section A36.3.8.196

174. Section A36.3.9 Calibration and checking of system96

175. Section A36.3.9.196

176. Section A36.3.9.296

177. Section A36.3.9.397

178. Section A36.3.9.497

179. Section A36.3.9.597

180. Section A36.3.9.697

181. Section A36.3.9.797

182. Section A36.3.9.897

183. Section A36.3.9.998

184. Section A36.3.9.1098

185. Section A36.3.10 Adjustments for ambient noise100

186. Section A36.3.10.1100

187. Section A36.3.10.2101

188. Section A36.4 Calculation of Effective Perceived Noise Level From Measured Data101

189. Section A36.4.1 General101

190. Section A36.4.1.1101

191. Section A36.4.1.2101

192. Section A36.4.1.3101

193. Section A36.4.2 Perceived noise level102

194. Section A36.4.2.1102

195. Section A36.4.3 Correction for spectral irregularities103

196. Section A36.4.3.1103

197. Section A36.4.3.2108

198. Section A36.4.4 Maximum tone-corrected perceived noise level109

199. Section A36.4.4.1109

200. Section A36.4.4.2110

201. Section A36.4.5 Duration correction110

202. Section A36.4.5.1110

203. Section A36.4.5.2111

204. Section A36.4.5.3111

205. Section A36.4.5.4111

206. Section A36.4.5.5112

207. Section A36.4.6 Effective perceived noise level112

208. Section A36.4.6112

209. Section A36.4.7 Mathematical formulation of noy tables113

210. Section A36.4.7.1113

211. Section A36.4.7.2113

212. Section A36.4.7.3 Calculate noy values using the following equations:113

213. Section A36.4.7.4113

214. Section A36.5. Reporting of Data to the FAA117

215. Section A36.5.1 General117

216. Section A36.5.1.1117

217. Section A36.5.1.2117

218. Section A36.5.1.3117

219. Section A36.5.2 Data reporting117

220. Section A36.5.2.1118

221. Section A36.5.2.2118

222. Section A36.5.2.3118

223. Section A36.5.2.4118

224. Section A36.5.2.5118

225. Section A36.5.3 Reporting of noise certification reference conditions119

226. Section A36.5.3.1119

227. Section A36.5.4 Validity of results119

228. Section A36.5.4.1120

229. Section A36.5.4.2120

230. Section A36.5.4.3120

231. Section A36.6 Nomenclature: Symbols and Units123

232. Section A36.7 Sound Attenuation in Air127

233. Section A36.7.1127

234. Section A36.7.2127

235. Section A36.7.3129

236. Section A36.8. [Reserved]130

237. Section A36.9. Adjustment of Airplane Flight Test Results130

238. Section A36.9.1130

239. Section A36.9.1.1131

240. Section A36.9.1.2133

241. Section A36.9.2 Flight profiles134

242. Section A36.9.2.1 Takeoff Profile134

243. Section A36.9.2.2 Approach Profile141

244. Section A36.9.3 Simplified method of adjustment145

245. Section A36.9.3.1 General145

246. Section A36.9.3.2 Adjustments to PNL and PNLT146

247. Section A36.9.3.2.1148

248. Section A36.9.3.2.1.1 PNLT Correction150

249. Section A36.9.3.2.1.2150

250. Section A36.9.3.2.2150

251. Section A36.9.3.3 Adjustments to duration correction151

252. Section A36.9.3.3.1151

253. Section A36.9.3.3.2151

254. Section A36.9.3.4 Source noise adjustments152

255. Section A36.9.3.4.1152

256. Section A36.9.3.4.2152

257. Section A36.9.3.5 Symmetry Adjustments152

258. Section A36.9.3.5.1152

259. Section A36.9.4 Integrated method of adjustment153

260. Section A36.9.4.1 General153

261. Section A36.9.4.2 PNLT computations154

262. Section A36.9.4.2.1157

263. Section A36.9.4.2.2158

264. Section A36.9.4.2.3158

265. Section A36.9.4.3 Duration correction158

266. Section A36.9.4.3.1158

267. Section A36.9.4.4 Source noise adjustment158

268. Section A36.9.4.4.1158

269. Section A36.9.5 Flight Path Identification Positions159

270. Section A36.9.6 Flight Path Distances159

271. - 289--RESERVED160

XIV. APPENDIX B TO part 36--NOISE LEVELS FOR TRANSPORT CATEGORY AND JET

AIRPLANES UNDER § 36.103161

290. Appendix B to Part 36-Noise Levels for Transport Category and Jet Airplanes Under § 36.103 161

291. Section B36.1 Noise Measurement and Evaluation161

292. Section B36.2 Noise Evaluation Metric161

293. Section B36.3 Reference Noise Measurement Points162

294. Section B36.4 Test noise measurement points162

295. Section B36.5 Maximum Noise Levels163

296. Section B36.6 Trade-Offs165

297. Section B36.7 Noise Certification Reference Procedures and Conditions166

298. Section B36.7(a) General conditions:166

299. Section B36.7(b) Takeoff reference procedure:167

300. Section B36.7(b)(1)167

301. Section B36.7(b)(2)168

302. Section B36.7(b)(3)168

303. Section B36.7(b)(4)169

304. Section B36.7(b)(5)169

305. Section B36.7(b)(6)170

306. Section B36.7(b)(7)170

307. Section B36.7(c) Approach reference procedure:171

308. Section B36.7(c)(1)171

309. Section B36.7(c)(2)171

310. Section B36.7(c)(3)171

311. Section B36.7(c)(4)172

312. Section B36.7(c)(5)173

313. Section B36.8 Noise Certification Test Procedures173

314. Section B36.8(a)173

315. Section B36.8(b)174

316. Section B36.8(c)174

317. Section B36.8(d)174

318. Section B36.8(e)175

319. Section B36.8(f)175

320. Section B36.8(g)175

321. - 349. [RESERVED]176

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, 1988177

350. PART A - GENERAL177

351. Section F36.1 Scope [To be completed later.]177

352. PART B - NOISE MEASUREMENT177

353. Section F36.101 General Test Conditions [To be completed later.]177

354. Section F36.103 Acoustical Measurement System [To be completed later.]177

355. Section F36.105 Sensing, Recording, and Reproducing Equipment177

356. Section F36.107 Noise Measurement Procedures [To be completed later.]177

357. Section F36.109 Data Recording, Reporting, and Approval [To be completed later177

358. Section F36.111 Flight Procedures [To be completed later.]177

359. PART C - DATA CORRECTION177

360. Section F36.201 Correction of Data [To be completed later.]177

361. Section F36.203 Validity of Results [To be completed later.]177

362. PART D - NOISE LIMITS177

363. Section F36.301 Aircraft Noise Limits [To be completed later.]177

364. - 374. [RESERVED]177

XVI. 14 CFR PART 36 APPENDIX G. TAKE-OFF NOISE REQUIREMENTS FOR PROPELLER-

DRIVEN, SMALL AIRPLANE AND PROPELLER-DRIVEN, COMMUTER CATEGORY

AIRPLANE CERTIFICATION TESTS ON OR AFTER DECEMBER 22, 1988178

375. PART A - GENERAL178

376. Section G36.1 Scope178

377. PART B - NOISE MEASUREMENT178

378. Section G36.101 General test conditions178

379. Section G36.101(b)179

380. Section G36.101(c)181

381. Section G36.101(d)182

382. Section G36.103 Acoustical measurement system182

383. Section G36.103(b) & (c)182

384. Section G36.103(d)183

385. Section G36.105(a)184

386. Section G36.105(b)&(c)184

387. Section G36.105(d)185

388. Section G36.105(e)186

389. Section G36.105(f)187

390. Section G36.105(g)187

391. Section G36.107 Noise measurement188

392. Section G36.107(b)190

393. Section G36.107(c)191

394. Section G36.109 Data Recording, Reporting and Approval192

395. Section G36.109(b)193

396. Section G36.109(c) & (d)193

397. Section G36.109(e)194

398. Section G36.109(f)194

399. Section G36.109(g)194

400. Section G36.111 Flight procedures195

401. Section G36.111(b)196

402. Section G36.111(c)196

403. Section G36.111(c)(1)197

404. Section G36.111(c)(2)198

405. PART C - DATA CORRECTION199

406. [RESERVED]199

407. Section G36.201 Correction of Data199

408. Section G36.201(b)200

409. Section G36.201(c)201

410. Section G36.201(d)201

411. Section G36.201(d)(1)202

412. Section G36.201(d)(2)203

413. Section G36.201(d)(3)204

414. Section G36.201(d)(4)206

415. Section G36.203 Validity of Results208

416. PART D - NOISE LIMITS209

417. Section G36.301 Aircraft Noise Limits209

418. −429. [RESERVED]210

XVII. 14 CFR PART 36 APPENDIX H- NOISE REQUIREMENTS FOR HELICOPTERS UNDER SUB-

PART H [To be completed later]211

XVIII. 14 CFR PART 36 APPENDIX J- ALTERNATIVE NOISE CERTIFICATION PROCEDURE FOR

HELICOPTERS UNDER SUBPART H HAVING A MAXIMUM CERTIFICATED TAKE-OFF

WEIGHT OF NOT MORE THAN 6,000 POUNDS [To be completed later]211

APPENDICES

APPENDIX 1 – ICAO Committee on Aviation Environmental Protection - Environmental Technical Manual On The Use Of Procedures In The Noise Certification Of Aircraft, Steering Group Approved Revision 7 APPENDIX 2 – VNTSC Certification Validation Package APPENDIX 3 – Guidelines for Correction of Aircraft Noise Levels for the Effects of Background Noise APPENDIX 4 – Equivalent Procedures and Demonstrating "No Acoustical Change” for Propeller-Driven Small Airplanes and Commuter Category Airplanes

FIGURES

FIGURE 1 Document Format FIGURE 2 Noise Time History with Thrust (Power) Reduction FIGURE 3 Normal Full Thrust (Power) Take-Off FIGURE 4 Flight Path Intercept Take-off FIGURE 5 Take-off Flight Path FIGURE 6 Approach With Full Landing FIGURE 7 Flight Path Intercept Approach FIGURE 8 Approach Flight Path Deviations FIGURE 9-12 RESERVED FIGURE 13 Configuration for 1/2 in. Inverted Microphone Over Plate FIGURE 14 Graphic Representation of Adjusted Measurement Location FIGURE 15 Typical Test and Reference Flight Paths FIGURE 16 Obstruction Free Noise Measurement Cone (Flyover Case Illustrated) FIGURE 17 Temperature/Relative Humidity Test Window

(Note: The figures identified in the above list were developed for AC 36-4C. Figures contained within part 36 itself have not been included in this list.)

TABLES

TABLE 1 Example - Atmospheric Measurements TABLE 2 Example - Atmospheric Measurements TABLE 3 Example – Atmospheric Sound Attenuation Coefficients TABLE 4 Example – Effective Layer Depth TABLE 5 Rate of Atmospheric Absorption (α) at 500 Hz Frequency TABLE 6 Student’s t Distribution For 90 Percent Confidence Interval

(Note: The tables identified in the above list were developed for AC 36-4C. Tables contained within part 36 itself have not been included in this list.)

8. PART 21 - GENERAL

As part of the overall aircraft certification requirements identified in part 21, applicants must comply with the noise certification requirements of part 36. An applicant for a type certificate must show that the aircraft meets the applicable requirements of part 36 (part 21, section 21.17). In addition, an applicant is entitled to a type certificate for an aircraft if the applicant submits the type design, test reports, and computations necessary to show that the product to be certificated meets the applicable airworthiness and aircraft noise requirements (part 21, sections

21.21 & 21.25). Similar requirements are imposed for aircraft manufactured in a foreign country for import into the United States (part 21, section 21.29). Refer to the part 21 regulations for specific regulatory language.

a. Explanation

None

b. Supplemental Information

(1) Airworthiness Certification: All aircraft requiring noise certification by the FAA are required to meet the applicable airworthiness requirements of part 21, which identifies the specific airworthiness standards for each aircraft type and product, such as:

i. Part 23 for normal, utility, acrobatic, and commuter category airplanes,

ii. Part 25 for transport category airplanes,

iii. Part 27 for normal category rotorcraft,

iv. Part 29 for transport category rotorcraft,

v. Part 33 for aircraft engines,

vi. Part 35 for propellers,

vii. Primary category aircraft, and

viii. JAR-VLA aircraft.

(2) Changes in Type Design. Part 21 section 21.93(b) requires compliance with the appropriate part 36 “acoustical change” requirements for a voluntary type design change of an aircraft that may increase the noise levels of that aircraft, regardless of whether the change in type design is classified as a minor or major change in part 21, section 21.93(a). See paragraph 16 of this AC for further discussion of acoustical change.

9.-11. [RESERVED]

I. CERTIFICATION PROCEDURES FOR PRODUCT AND PARTS 14 CFR PART 21

12. PART 36 – SUBPART A-GENERAL

a. Explanation

This Subpart specifies the Applicability of part 36, Definitions of Terms Unique to part 36, part 36 Requirements as of the Date of Type Certificate Application, Airworthiness Compatibility requirements, Limitations, Information on References, and Acoustical Change Requirements.

b. Supplemental Information

None

c. Procedures

None

13. Section 36.1 Applicability and definitions

14. Section 36.1(a)

This part prescribes noise standards for the issue of the following certificates:

(1) Type certificates, and changes to those certificates, and standard airworthiness certificates, for subsonic transport category large airplanes and for subsonic jet airplanes regardless of category.

(2) Type certificates and changes to those certificates, standard airworthiness certificates, and restricted category airworthiness certificates, for propeller-driven, small airplanes, and for propellerdriven, commuter category airplanes except those airplanes that are designed for "agricultural aircraft operations" (as defined in § 137.3 of this chapter, as effective on January 1, 1966) or for dispersing fire fighting materials to which § 36.1583 of this part does not apply.

(3) A type certificate and changes to that certificate, and standard airworthiness certificates, for Concorde airplanes.

(4) Type certificates, and changes to those certificates, for helicopters except those helicopters that are designated exclusively for "agricultural aircraft operations" (as defined in § 137.3 of this chapter, as effective on January 1, 1966), for dispensing fire fighting materials, or for carrying external loads (as defined in § 133.1(b) of this chapter, as effective on December 20, 1976).

a. Explanation

This section specifies aircraft types and categories to which part 36 requirements are applicable as a condition for issuance of type certificates (TC), changes to type certificates, supplemental type certificates (STC), amended type certificates and airworthiness certificates.

b. Supplemental Information

(1) Applicable Requirements: Unless otherwise specified, the date to be used for determining the applicability of the appropriate part 36 standards for an aircraft type design is the date on which application for a type certificate was made. An application for type certification is effective for the time periods specified in section

21.17(c) of part 21.

(2) Noise Related Type Certification Requirements: See paragraph 6-3(h) of reference 7 of this AC.

II. NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS CERTIFICATION 14 CFR PART 36

(3) Supplemental Type Certificates: See paragraph 6-3(j) of reference 7 of this AC.

(4) Definitions of Terms: Paragraph 4 of this Advisory Circular provides definitions for the following terms related to the aircraft types and categories within Items (1) – (4) of section 36.1(a).

Aircraft Large Aircraft Airplane Small Aircraft Helicopter Propeller Airplane Categories (See Note A) Jet Airplane

- Acrobatic Turboprop Airplane (See Note C)

- Commuter

- Normal

- Primary

- Restricted (See Note B)

- Transport

- Utility Helicopter Categories

- Normal

- Transport

Notes:

(A) Airplane Categories and Aircraft Classes: Part 1 recognizes a distinction between Airplane Categories (e.g., acrobatic, commuter, normal, primary, restricted, transport and utility) and Aircraft Classes (e.g., Conventional Takeoff and Landing (CTOL), Vertical Takeoff and Landing (VTOL), Short Takeoff and Landing (STOL), Reduced Takeoff and Landing (RTOL), and Supersonic Transports (SST)). The noise certification requirements contained in part 36 are specified for several Airplane and Helicopter Categories but not for STOL, RTOL, SST (except for Concorde), or VTOL Aircraft Classes.

(B) Restricted Category Propeller-Driven Large Airplanes: Propeller-driven large airplanes that have been type certificated in the restricted category (See part 21, section 21.25) are not required to demonstrate compliance with the requirements of part 36. In the absence of part 36 applicability, an Environmental Assessment is required (See FAA Order 8110.B (reference 7 of this AC) paragraph 6-3(d) for additional information).

(C) Turboprop Airplanes: Turboprop-powered airplanes are included under the part 36 requirements applicable to propeller-driven airplanes (i.e. subsonic transport category large airplanes; propellerdriven small airplanes, including acrobatic, normal, restricted, and transport categories; or propeller-driven commuter category airplanes).

c. Procedures

None

15. Section 36.1(b)

Each person who applies under part 21 of this chapter for a type of airworthiness certificate specified in this part must show compliance with the applicable requirements of this part, in addition to the applicable airworthiness requirements of this chapter.

a. Explanation

This section specifies that an applicant must comply with appropriate airworthiness requirements and part 36 requirements as a part of the total aircraft certification process.

b. Supplemental Information

(1) Aircraft Configuration for Noise Certification: An applicant’s proposal for an aircraft configuration to be certified under the requirements of part 36 must include any type design changes that may be a result of airworthiness standards testing and analysis, and which would result in acoustical changes (See section 36.1(c), Supplemental Information item number (2) for FAA criteria on when aircraft type design changes represent an acoustical change). If an applicant does not propose the appropriate aircraft configuration, additional noise certification testing and analysis may be required.

c. Procedures

None

16. Section 36.1(c).

Each person who applies under 14CFR part 21 of this chapter for approval of an acoustical change described in § 21.93(b) of this chapter must show that the aircraft complies with the applicable provisions of Sections 36.7, 36.9, or 36.11 of this part in addition to the applicable airworthiness requirements of this chapter.

a. Explanation:

This section specifies part 36 requirements when “ voluntary” changes are made to the type design of an aircraft under the provisions of part 21.

b. Supplemental Information:

(1) Acoustical Change: Part 21, section 21.93(b) defines an aircraft “acoustical change” and specific aircraft configurations excepted from part 36 requirements. The text of part 21, section 21.93(b) is as follows (Also see paragraph 6-3(i) of reference 7 of this AC).

(b) For the purpose of complying with part 36 of this chapter, and except as provided in paragraphs (b)(2), (b)(3), and (b)(4) of this section, any voluntary change in the type design of an aircraft that may increase the noise levels of that aircraft is an “acoustical change” (in addition to being a minor or major change as classified in paragraph in paragraph (a) of this section) for the following aircraft:

(1) Transport category large airplanes.

(2) Jet (Turbojet powered) airplanes (regardless of category). For airplanes to which this paragraph applies, “acoustical changes” do not include changes in type design that are limited to one of the following– (I) Gear down flight with one or more retractable landing gear down during the entire flight, or

(ii) Spare engine and nacelle carriage external to the skin of the airplane (and return of the pylon or other external mount), or

(iii) Time-limited engine and/or nacelle changes, where the change in type design specifies that the airplane may not be operated for a period of more than 90 days unless compliance with the applicable acoustical change provisions of part 36 of this chapter is shown for that change in type design.

(3) Propeller driven commuter category and small airplanes in the primary, normal, utility, acrobatic, transport, and restricted categories, except for airplanes that are:

(I) Designated for “agricultural aircraft operations” (as defined in 34 137.3 of this chapter, effective January 1, 1966) to which § 36.1583 of this chapter does not apply, or

(ii) Designated for dispensing fire fighting materials to which § 36.1583 of this chapter does not apply, or

(iii) US registered, and that had flight time prior to January 1, 1955 or

(iv) Land configured aircraft reconfigured with floats or skis. This reconfiguration does not permit further exception from the requirements of this section upon any acoustical change not enumerated in § 21.93(b).

(4) Helicopters, (except for those helicopters that are designated exclusively for “agricultural aircraft operations”, as defined in § 137.2 of this chapter, as effective on January 1, 1966, for dispensing fire fighting materials, or for carrying external loads, as defined in § 133.1(b) of this chapter, as effective on December 20, 1976). For helicopters to which this paragraph applies, “acoustical changes” include the following type design changes:

(i) Any changes to, or removal of, a muffler or other component designed for noise control.

(ii) Any other design or configuration change (including a change in the operating limitations of the aircraft) that, based on FAA-approved analytical or test data, the Administrator determines may result in an increase in noise level.”

(2) Voluntary Changes in Type Design: A voluntary change in the configuration of an aircraft means a change in the type design of that aircraft. Examples of voluntary changes in aircraft type design that may affect part 36 certificated noise levels are as follows:

i. Increased engine thrust (power) to improve aircraft performance;

ii. Maximum gross weight changes;

iii. Limitations on operational flap settings related to noise;

iv. Hardware revisions (e.g., vortex generators, flap configuration, wing tip stabilizers, wing tip fuel tanks, etc.);

v. Engine modifications to improve engine performance, acceleration, deceleration, or surge margin protection;

vi. Addition of wing or body hardware to improve aerodynamics;

vii. External nacelle changes to improve air flow patterns;

viii. Engine inlet changes to improve ice protection;

ix. Reduction of engine blade tip clearances to improve inlet flow characteristics, and;

x. Modifications to engine/nacelle acoustic treatments.

(3) Acoustical Change Criteria: A voluntary change in the type design of an aircraft that may result in an increase in its certificated noise levels is defined as an “ acoustical change.” The numerical criteria used by the FAA in defining an acoustical change is a change in certificated flyover, lateral or approach noise levels of

0.10 EPNdB/dB (A) (if such changes are not formally tracked by an FAA approved method) or 0.30 EPNdB/dB (A) if an applicant has obtained an FAA approved plan to track and sum cumulative changes. These criteria are also provided in section 1.4.3 of the appended ICAO TM and are established to limit the cumulative effects of multiple small changes.

(4) No Acoustical Changes: Type design changes that do not result in an “ acoustical change” as defined in part 21, section 21.93(b) are referred to as “no acoustical changes” (NAC).

(5) NAC Cumulative Effects: When type design changes result in reduced noise levels, an applicant may elect not to provide the full part 36 substantiation, but instead provide FAA with data and/or information to substantiate a NAC. However subsequent type design changes may require full part 36 certification because of cumulative acoustical effects. Example: An applicant proposes a configuration change which will reduce the noise levels by approximately 2.1 dB for the flyover noise measurement point, 1.1 dB for the lateral noise measurement point, and with no change in noise level at the approach noise measurement point.

FAA verifies that the noise levels were reduced, and the applicant accepts the pre-change configuration certificated noise levels as published in the AFM to apply to this change in type design. The applicant may not make another type design change as a NAC that increases the flyover noise level and the lateral noise level without providing substantiation of the cumulative effects of this type design change on AFM noise certificated levels. Multiple type design changes must be evaluated on a cumulative basis (as a combined single configuration) for each noise measurement point for the purposes of determining whether there is an acoustical change.

(6) Non-Standard Jet Airplane Configurations: Sections 21.93(b)(2)(i) and (ii) specify exceptions under which certain changes in jet airplane type design are not subject to compliance with 14 CFR part 36 requirements because such configurations are not intended for normal operations, but are typically required for maintenance operations (e.g., ferry flights, transporting engines to aircraft that cannot be ferried, etc.).

(7) Time-Limited Changes: Time-Limited engine or nacelle changes on jet airplanes for periods of up to 90 days (as specified in part 21, section 21.93(b)(2)(iii)) may be necessary for continued airplane operation until maintenance can be performed on the original engines or nacelles that were changed. These changes must comply with applicable airworthiness standards and the maintenance, preventative maintenance, rebuilding and alteration inspection requirements of part 43. Such changes do not require compliance with part 36 requirements even though they may result in an increase in airplane noise levels, relative to the certificated noise levels. FAA policy (See Federal Register Vol. 64, No. 225, Page 65655, dated November 23, 1999) permits the 90 day period allowed by part 21, section 21.93(b)(2)(iii) to continue to be used after December 31, 1999, but only for maintenance-related purposes. It cannot be used for meeting Stage 3 requirements due to lack of an adequate number of spare engines or nacelles, or insufficient number of engines or nacelles to operate a Stage 3 fleet at a given time. Section 21.93(b)(2)(iii) may only be used to intermix engines when maintenance is required and no conforming engine or nacelle for the configuration is available.

(8) Special Purpose Aircraft: Type design changes to propeller-driven small airplanes and helicopters do not need to comply with the provisions of part 36 when they are operated for special purposes as specified in part 21, sections 21.93(b)(3)(i-iv) and 21.93(b)(4).

c. Procedures

(1) Applicant’s Responsibility: Pursuant to section 21.93(b), an applicant must identify type design changes that affect an aircraft’s certificated noise levels by aircraft serial number and must demonstrate part 36 compliance for those aircraft. The noise levels approved by the FAA for the modified aircraft must be documented in an FAA Approved AFM or RFM by either a revision to the AFM or RFM (typically an option only available to the aircraft manufacturer), an AFM or RFM Supplement (for Supplemental Type Certificates and Field Approvals), or a Supplemental AFM or RFM (for aircraft that do not have a FAA Approved AFM or RFM).

Configurations and modifications for which noise approval is required must be found to comply with applicable airworthiness requirements specified in part 21 as well as the requirements of part 36 [reference section 36.3].

(2) NAC Approvals: FAA may approve results of component laboratory demonstrations, backto-back noise comparisons from ground tests or flight tests of each configuration, acoustical analyses, etc as acceptable for substantiating that an applicant’s proposed changes to an aircraft type design is an NAC. The results from these evaluations must be applicable to an aircraft’s certified noise levels at the part 36 reference noise measurement points.

17. Section 36.1(d)

Each person who applies for the original issue of a standard airworthiness certificate for a subsonic transport category large airplane or for a jet airplane under14CFR part 21 § 21.183 must, regardless of date of application, show compliance with the following provisions of this part (including Appendix B):

(1) The provisions of this part in effect on December 1, 1969, for subsonic airplanes that have not had any flight time before-- (I) December 1, 1973, for airplanes with maximum weights greater than 75,000 pounds, except for airplanes that are powered by Pratt & Whitney Turbo Wasp JT3D series engines;

(ii) December 31, 1974, for airplanes with maximum weights greater than 75,000 pounds and that are powered by Pratt & Whitney Turbo Wasp JT3D series engines; and

(iii) December 31, 1974, for airplanes with maximum weights of 75,000 pounds and less.

(2) The provisions of this part in effect on October 13, 1977, including the stage 2 noise limits, for Concorde airplanes that have not had flight time before January 1, 1980.