Advisory of Transportation U.S. Department crau ar Federal Aviation Administration Subject: CERTIFICATION OF NORMAL Date: 7/30/97 AC No: 27-1A CATEGORY ROTORCRAFT Initiated by: ASW-110 Change:
1. PURPOSE:
a. This is a total revision of AC 27-1 dated 8/29/85, with changes 1, 2, 3, and 4 dated 9/16/87, 4/24/89, 9/12/91, and 8/18/95 respectively, incorporated. In addition, new material plus changes to existing paragraphs have been incorporated. This consolidated version is now renumbered as AC 27-1A and replaces AC 27-1 in its entirety. This revises existing material in 14 paragraphs and adds new material for 17 paragraphs.
b. This AC does not change regulatory requirements and does not authorize changes in, or deviations from regulatory requirements. This AC establishes an acceptable means, but not the only means of compliance. Since the guidance material presented in this AC is not regulatory, terms having a mandatory definition, such as "shall" and "must," etc., as used in this AC, apply either to the reiteration of a regulation itself, or to an applicant who chooses to follow a prescribed method of compliance without deviation.
c. This advisory circular provides information on methods of compliance with 14 CFR Part 27, which contains the Airworthiness Standards for Normal Category Rotorcraft. It includes methods of compliance in the areas of basic design, ground tests, and flight tests.
2. CANCELLATION. AC 27-1, Certification of Normal Category Rotorcraft, August 29, 1985, is canceled in its entirety.
3. BACKGROUND. Based largely on precedents set during rotorcraft certification programs spanning the past 39 years, this AC consolidates guidance contained in earlier correspondence among FAA headquarters, foreign authorities, the rotorcraft industry, and certificating regions.
4. PRINCIPAL CHANGES:
a. Paragraphs 32, 45, 58, 338, 532, 619, 621, 633, 641, 720, 726, 765, 775, and 777 are revised to incorporate technical guidance.
b. New paragraphs 31A, 58B, 63A, 218B, 218C, 230A, 423B, 447, 454B, 456, 459A, 460B, 563B, 568, 619B, and 724B are added to Chapter 2.
c. New paragraph 781B is added to Chapter 3.
d. Paragraph 447, § 27.951, General, is renumbered to Paragraph 446. Paragraph 447 now addresses § 27.952, Fuel System Crash Resistance.
For sale by the U.S. Govemment Printing Office Superintendent of Documents, Mail Stop: SSOP, Washington, DC 20402-9328 ISBN 0-16-049210-6
e. The following appendix has been added:
Appendix 1 Rotorcraft One-Engine-Inoperative (OEI) Power Assurance
f. Use of the term "FAA/AUTHORITY" replaces "FAA" as appropriate. "FAA/AUTHORITY" as used in this document means FAA or another airworthiness authority that has adopted this AC as a means of compliance with the appropriate regulation referenced.
5. DEVIATIONS. As rotorcraft designs vary from conventional configurations, it may become necessary to deviate from the methods and procedures outlined in this AC. These procedures are only one acceptable means of compliance with Part 27. Any alternate means proposed by an applicant will be given due consideration. Applicants are encouraged to use their technical ingenuity and resourcefulness to develop more efficient and less costly methods of achieving the objectives of Part 27. Regulatory personnel and designees should respond to such efforts by the use of engineering judgment in fostering any such efforts as long as the letter and spirit of Part 27 and the Federal Aviation Act are respected. It is recommended that unusual or unique projects be coordinated a sufficient time in advance with the Rotorcraft Standards Staff, ASW-110, or with the appropriate airworthiness authority, to ensure timely and uniform consideration.
6. APPLICABILITY. This material is not to be construed as having any legally binding status and must be treated as advisory only. However, to ensure standardization in the certification process, these procedures should be considered during all rotorcraft type certification and supplemental type certification activities.
7. PARAGRAPHS KEYED TO FAR PART 27. Each paragraph has the applicable amendment to Part 27 shown in the title. All of the original guidance material has been retained as appropriate, even as changes are made to the regulations. This is accomplished through the use of "A," "B," etc., paragraphs which follow the original numbered paragraphs. These subsequent paragraphs provide updated guidance information or changes to policy that parallel a specific rule change.
The guidance material in the original paragraph (for earlier amendments) still applies and is modified as explained in each of the later paragraphs for later amendments. The applicable amendment number will only appear in the title line for the "A," "B," etc., paragraphs. The guidance material in the initial paragraph is intended to apply to all amendments except as modified by the later paragraphs. Each ensuing "A," "B," etc., paragraph will be identified with an amendment level to indicate the rule change that precipitated the policy change.
8. RELATED PUBLICATIONS. FAA Certification personnel and designees should be familiar with Order 8110.4, Type Certification, and Order 8100.5, Aircraft Certification Directorate Procedures.
Eric Bries Acting Manager, Rotorcraft Directorate Aircraft Certification Service
TABLE OF CONTENTS CHAPTER 1 - FAR 21 CERTIFICATION PROCEDURES FOR PRODUCTS AND PARTS Page No.
1.-3. RESERVED
4. FAR 21.16 Special Conditions. 1
5.-7 RESERVED
8. FAR 21.31 Type Design.. 6
9.-11. RESERVED
12. FAR 21.33 Inspection and Tests.. .. 10
13.-15. RESERVED
16. FAR 21.35 Flight Tests.. . 14
17.-23. RESERVED
24. FAR 21.39 Flight Test Instrument. .. 24 Calibration and Correction Report
25.-30. RESERVED CHAPTER 2 - FAR 27 AIRWORTHINESS STANDARDS: NORMAL CATEGORY
ROTORCRAFT SECTION 1. GENERAL
31. FAR 27.1 Applicability 31 31A. FAR 27.1 Applicability 31
32. FAR 27.2 Special Retroactive Requirements 31
33.-41. RESERVED SECTION 2. FLIGHT - GENERAL
42. FAR 27.21 Proof of Compliance. 43
43. FAR 27.25 Weight Limits. 44
44. FAR 27.27 Center of Gravity Limits46
45. FAR 27.29 Empty Weight and Corresponding Center of Gravity. 48
46. FAR 27.31 Removable Ballast 49
47. FAR 27.33 Main Rotor Speed and Pitch Limits . 49
48.-57. RESERVED SECTION 3. PERFORMANCE
58. FAR 27.45 General ..61 58A. FAR 27.45 General ... 70 58B. FAR 27.45 General .. 70
59. FAR 27.51 Takeoff .77
SECTION 3. PERFORMANCE (continued) Page No.
60.-62. RESERVED
63. FAR 27.65 Climb: All Engines Operating. .. 82 63A. FAR 27.65 Climb: All Engines Operating.. .. 84
64. FAR 27.67 Climb: One Engine Inoperative.. 84
65. FAR 27.71 Glide Performance ............. ..85
66. FAR 27.73 Performance at Minimum Operating Speed. .. 88
67. FAR 27.75 Landing ..... .. 90
68. RESERVED
69. FAR 27.79 Limiting Height - Speed Envelope 95 69A. FAR 27.79 Limiting Height - Speed Envelope 103
70.-79. RESERVED SECTION 4. FLIGHT CHARACTERISTICS
80. FAR 27.141 General. . 114
81. FAR 27.143 Controllability and Maneuverability .. .. 115
82. FAR 27.151 Flight Controls 120
83. FAR 27.161 Trim Control .. 121 84 FAR 27.171 Stability: General 122
85. FAR 27.173 Static Longitudinal Stability.. . 122 86 FAR 27.175 Demonstration of Static Longitudinal Stability. 123
87. FAR 27.177 Static Directional Stability ... 128
88.-95. RESERVED SECTION 5. GROUND AND WATER HANDLING CHARACTERISTICS
96. FAR 27.231 General . 138
97. FAR 27.235 Taxiing Condition. 138
98. FAR 27.239 Spray Characteristics 139
99. FAR 27.241 Ground Resonance 140
100.-109. RESERVED SECTION 6. MISCELLANEOUS FLIGHT REQUIREMENTS
110. FAR 27.251 Vibration. . 155
111.-120. RESERVED SECTION 7. STRENGTH REQUIREMENTS - GENERAL
121. FAR 27.301 Loads. 168
122. FAR 27.303 Factor of Safety.. 168 IV
SECTION 7. STRENGTH REQUIREMENTS - GENERAL (continued) Page No.
123. FAR 27.305 Strength and Deformation 168
124. FAR 27.307 Proof of Structure. 169 124A. FAR 27.307 Proof of Structure. 170
125. FAR 27.309 Design Limitations. 170
126.-135. RESERVED SECTION 8. FLIGHT LOADS
136. FAR 27.321 General .. 182
137. FAR 27.337 Limit Maneuvering Load Factor. 182
138. FAR 27.339 Resultant Limit Maneuvering Loads 185
139. FAR 27.341 Gust Loads. 185
140. FAR 27.351 Yawing Conditions. 186
141. FAR 27.361 Engine Torque. 190
142.-151. RESERVED SECTION 9. CONTROL SURFACE AND SYSTEM LOADS
152. FAR 27.391 General . 202 152A. FAR 27.391 General. 202 FAR 27.395 Control System 202 153A. FAR 27.395 Control System. 204 FAR 27.397 Limit Pilot Forces and Torques 204 FAR 27.399 Dual Control System. 205 FAR 27.401 Auxiliary Rotor Assemblies 205 156A. FAR 27.401 Auxiliary Rotor Assemblies. 207 FAR 27.403 Auxiliary Rotor Attachment Structure. 207 157A. FAR 27.403 Auxiliary Rotor Attachment Structure 208
158. FAR 27.411 Ground Clearance: Tail Rotor Guard 208
159. FAR 27.413 Stabilizing and Control Surfaces 209 159A. FAR 27.413 Stabilizing and Control Surfaces.. ..211 FAR 27.427 Unsymmetrical Loads.. 211
161.-169. RESERVED SECTION 10. GROUND LOADS
170. FAR 27.471 General .. 225
171. FAR 27.473 Ground Loading Conditions and Assumptions. 225
172. FAR 27.475 Tires and Shock Absorbers 226
173. FAR 27.477 Landing Gear Arrangement 226
174. FAR 27.479 Level Landing Conditions. 226
SECTION 10. GROUND LOADS (continued) Page No.
175. FAR 27.481 Tail-Down Landing Conditions 227
176. FAR 27.483 One-Wheel Landing Conditions.. .. 228
177. FAR 27.485 Lateral Drift Landing Conditions. .. 228
178. FAR 27.493 Braked Roll Conditions....... .. 229
179. FAR 27.497 Ground Loading Conditions: 229 Landing Gear With Tail Wheels
180. FAR 27.501 Ground Loading Conditions 231 Landing Gear With Skids 180A. FAR 27.501 Ground Loading Conditions: 232 Landing Gear With Skids
181. FAR 27.505 Ski Landing Conditions... 233
182.-192. RESERVED SECTION 11. WATER LOADS
193. RESERVED
194. FAR 27.521 Float Landing Conditions.. 245
195.-204. RESERVED SECTION 12. MAIN COMPONENT REQUIREMENTS
205. FAR 27.547 Main Rotor Structure. 258
206. FAR 27.549 Fuselage, Landing Gear, and Rotor Pylon Structure 258
207.-217. RESERVED SECTION 13. EMERGENCY LANDING CONDITIONS
218. FAR 27.561 General .. 271 218AFAR 27.561 Emergency Landing Conditions - General.. .272 218B. FAR 27.561 Emergency Landing Conditions - General 272 218C. FAR 27.561 Emergency Landing Conditions - General.. .. 273
219. FAR 27.562 Emergency Landing Dynamic Conditions. 273
220. FAR 27.563 Structural Ditching Provisions.. .274 220A. FAR 27.563 Structural Ditching Provisions. . 274
221.-229. RESERVED SECTION 14. FATIGUE EVALUATION
230. FAR 27.571 Fatigue Evaluation of Flight Structure. .. 285 230A. FAR 27.571 Fatigue Evaluation of Flight Structure for Category A Certification 288
231.-240. RESERVED VI
SECTION 15. DESIGN AND CONSTRUCTION - GENERAL Page No.
241. FAR 27.601 Design. .. 300
242. FAR 27.603 Materials .. . 300
243. FAR 27.605 Fabrication Methods.. 301
244. FAR 27.607 Fasteners.. 302
245. FAR 27.609 Protection of Structure302
246. FAR 27.610 Lightning Protection... 303
247. FAR 27.611 Inspection Provisions ..... .. 306
248. FAR 27.613 Material Strength Properties 306 and Design Values 248A. FAR 27.613 Material Strength Properties .308 and Design Values
249. FAR 27.619 Special Factors . .. 309
250. FAR 27.621 Casting Factors 309
251. FAR 27.623 Bearing Factors .. 319
252. FAR 27.625 Fitting Factors .. 320
253. FAR 27.629 Flutter.. 321
254.-264. RESERVED SECTION 16. ROTORS
265. FAR 27.653 Pressure Venting and Drainage of Rotor Blades . 334
266. FAR 27.659 Mass Balance. 334
267. FAR 27.661 Rotor Blade Clearance... .. 334
268. FAR 27.663 Ground Resonance Prevention Means.. 335 268A. FAR 27.663 Ground Resonance Prevention Means. .. 337
269.-277. RESERVED SECTION 17. CONTROL SYSTEMS
278. FAR 27.671 General .. 348
279. FAR 27.672 Stability Augmentation, Automatic,. .. 348 and Power-Operated Systems FAR 27.673 Primary Flight Control..... .349 FAR 27.674 Interconnected Controls. .. 349 FAR 27.675 Stops.. . 350
FAR 27.679 Control System Locks351
FAR 27.681 Limit Load Static Tests... 352 FAR 27.683 Operation Tests. 353 FAR 27.685 Control System Details... .. 353 286A. FAR 27.685 Control System Details... .354 FAR 27.687 Spring Devices.. 355
288. FAR 27.691 Autorotation Control Mechanism 355 VII
SECTION 17. CONTROL SYSTEMS (continued) Page No.
289. FAR 27.695 Power Boost and Power-Operated Control System ... 356
290.-297. RESERVED SECTION 18. LANDING GEAR
298. FAR 27.723 Shock Absorption Tests. .. 367
299. FAR 27.725 Limit Drop Test.. . 370
300. FAR 27.727 Reserve Energy Absorption Drop Test. .. 370 300A. FAR 27.727 Reserve Energy Absorption Drop Test.. ... 371
301. FAR 27.729 Retracting Mechanism ... 371
302. FAR 27.731 Wheels .. .. 374
303. FAR 27.733 Tires. 375
304. FAR 27.735 Brakes. 376
305. FAR 27.737 Skis 378
306.-315. RESERVED SECTION 19. FLOATS AND HULLS
316. FAR 27.751 Main Float Buoyancy 390
317. FAR 27.753 Main Float Design .. 390
318. FAR 27.755 Hulls. 391
319.-329. RESERVED SECTION 20. PERSONNEL AND CARGO ACCOMMODATIONS FAR 27.771 Pilot Compartment. ,404 FAR 27.773 Pilot Compartment View .405 FAR 27.775 Windshields and Windows. .410 332A. FAR 27.775 Windshields and Windows. .410 FAR 27.777 Cockpit Controls.. .410 FAR 27.779 Motion and Effect of Cockpit Controls ... ..411 FAR 27.783 Doors .414 335A. FAR 27.783 Doors .. .416
336. FAR 27.785 Seats, Berths, Safety Belts, and Harnesses .416 336A. FAR 27.785 Seats, Berths, Safety Belts, and Harnesses . 420
337. FAR 27.787 Cargo and Baggage Compartments.. . 422 337A. FAR 27.787 Cargo and Baggage Compartments. .424
338. FAR 27.801 Ditching. 424
339. RESERVED
340. FAR 27.807 Emergency Exits. 433 340A. FAR 27.807 Emergency Exits 434 VIlI
SECTION 20. PERSONNEL AND CARGO ACCOMODATIONS (continued) Page No.
341.-344. RESERVED
345. FAR 27.831 Ventilation 439
346. FAR 27.833 Heaters .. .440
347.-356. RESERVED SECTION 21. FIRE PROTECTION
357. RESERVED
FAR 27.853 Compartment Interiors454
FAR 27.855 Cargo and Baggage Compartments .455
360. FAR 27.859 Heating Systems.. 456
361. FAR 27.861 Fire Protection of Structure, Controls, and Other Parts. 460 361A. FAR 27.861 Fire Protection of Structure, Controls, and Other Parts 462
362. FAR 27.863 Flammable Fluid Fire Protection 463
363.-372. RESERVED SECTION 22. EXTERNAL LOAD ATTACHING MEANS
373. FAR 27.865 External Load Attaching Means. 475 373A. FAR 27.865 External Load Attaching Means 476
374.-383. RESERVED SECTION 23. MISCELLANEOUS (DESIGN AND CONSTRUCTION)
384. FAR 27.871 Leveling Marks.. .487
385. FAR 27.873 Ballast Provisions.. 487
386.-396. RESERVED SECTION 24. POWERPLANT - GENERAL
397. FAR 27.901 Installation.. .. 500 397A. FAR 27.901 Installation.. 503
398. FAR 27.903 Engines.. .. 504 398A. FAR 27.903 Engines... .506
399. FAR 27.907 Engine Vibration.... . 508
400.-420. RESERVED IX
SECTION 25, ROTOR DRIVE SYSTEM Page No.
421. FAR 27.917 Design. .. 530
422. FAR 27.921 Rotor Brake.. 531
423. FAR 27.923 Rotor Drive System and Control Mechanism Tests 532 423A. FAR 27.923 Rotor Drive System and Control Mechanism Tests 537 423B. FAR 27.923 Rotor Drive System and Control Mechanism Tests 538
424. FAR 27.927 Additional Tests.. 539 424A. FAR 27.927 Additional Tests.. 541
425. FAR 27.931 Shafting Critical Speeds541
426. FAR 27.935 Shafting Joints... 546
427. FAR 27.939 Turbine Engine Operating Characteristics 546
428.-445. RESERVED SECTION 26, FUEL SYSTEM
446. FAR 27.951 General 567
447. FAR 27.952 Fuel System Crash Resistance 569
448. FAR 27.953 Fuel System Independence. 595
449. FAR 27.954 Fuel System Lightning Protection 596
450. FAR 27.955 Fuel Flow... 597 450A. FAR 27.955 Fuel Flow. 601
451. RESERVED
452. FAR 27.959 Unusable Fuel Supply. 605
453. FAR 27.961 Fuel System Hot Weather Operation 605 453A. FAR 27.961 Fuel System Hot Weather Operation 607
454. FAR 27.963 Fuel Tanks: General.. . 607 454A. FAR 27.963 Fuel Tanks: General . 608 454B. FAR 27.963 Fuel Tanks: General . 608
455. FAR 27.965 Fuel Tank Tests . 609
456. FAR 27.967 Fuel Tank Installation.. . 610
457. FAR 27.969 Fuel Tank Expansion Space . 612 457A. FAR 27.969 Fuel Tank Expansion Space ..613
458. FAR 27.971 Fuel Tank Sump.... ..613 458A. FAR 27.971 Fuel Tank Sump.. . 614
459. FAR 27.973 Fuel Tank Filler Connection.. .. 615 459A. FAR 27.973 Fuel Tank Filler Connection ..615
460. FAR 27.975 Fuel Tank Vents.. 616 460A. FAR 27.975 Fuel Tank Vents. .618 460B. FAR 27.975 Fuel Tank Vents. ..618
461. FAR 27.977 Fuel Tank Outlet. ..619
462.-482. RESERVED
SECTION 27, FUEL SYSTEM COMPONENTS Page No.
483. FAR 27.991 Fuel Pumps. .. 641 483A. FAR 27.991 Fuel Pumps.. 642
484. FAR 27.993 Fuel System Lines and Fittings 642
485. FAR 27.995 Fuel Valves. 643
486. FAR 27.997 Fuel Strainer or Filter.. .. 643 486A. FAR 27.997 Fuel Strainer or Filter. … 644
487. FAR 27.999 Fuel System Drains.. ..645 487A. FAR 27.999 Fuel System Drains.. 646
488.-497. RESERVED SECTION 28. OIL ŞYSTEM
498. FAR 27.1011 General 657
499. FAR 27.1013 Oil Tanks. 657
500. FAR 27.1015 Oil Tank Tests. 658
501. FAR 27.1017 Oil Lines and Fittings.. 659
502. FAR 27.1019 Oil Strainer or Filter 659 502A. FAR 27.1019 Oil Strainer or Filter 660
503. FAR 27.1021 Oil System Drains.. 661
504. FAR 27.1027 Transmission and Gearboxes: General 661
505.-515. RESERVED SECTION 29. COOLING
516. FAR 27.1041 General ..674 516A. FAR 27.1041 General 676
517. FAR 27.1043 Cooling Tests. 676
518. FAR 27.1045 Cooling Test Procedures 679 518A. FAR 27.1045 Cooling Test Procedures 680
519.-530. RESERVED SECTION 30. INDUCTION SYSTEM
531. FAR 27.1091 Air Induction.. .. 693 531A. FAR 27.1091 Air Induction.. .. 694
532. FAR 27.1093 Induction System Icing Protection.. .. 694 532A. FAR 27.1093 Induction System Icing Protection .706
533.-547. RESERVED XI
SECTION 31. EXHAUST SYSTEM Page No.
548. FAR 27.1121 General.. 722
549. FAR 27.1123 Exhaust Piping .. 723
550.-560. RESERVED SECTION 32. POWERPLANT CONTROLS AND ACCESSORIES
561. FAR 27.1141 Powerplant Controls: General 737 561A. FAR 27.1141 Powerplant Controls: General 738
562. RESERVED
563. FAR 27.1143 Engine Controls. 740 563A. FAR 27.1143 Engine Controls. 740 563B. FAR 27.1143 Engine Controls. 741
564. FAR 27.1145 Ignition Switches 741
565. FAR 27.1147 Mixture Controls 742
566.-567. RESERVED
568. FAR 27.1151 Rotor Brake Controls .745
569. FAR 27.1163 Powerplant Accessories 746
570.-583. RESERVED SECTION 33. POWERPLANT FIRE PROTECTION
584. RESERVED
585. FAR 27.1183 Lines, Fittings, and Components. 764
586. FAR 27.1185 Flammable Fluids. 764
587. FAR 27.1187 Ventilation 766
588. FAR 27.1189 Shutoff Means. 767
589. FAR 27.1191 Firewalls 768
590. FAR 27.1193 Cowling and Engine Compartment Covering. 772 590A. FAR 27.1193 Cowling and Engine Compartment Covering 773
591. FAR 27.1194 Other Surtaces. 774
592. FAR 27.1195 Fire Detector Systems... .775
593.-616. RESERVED SECTION 34. EQUIPMENT - GENERAL
617. FAR 27.1301 Function and Installation .. 804
618. FAR 27.1303 Flight and Navigation Instruments.. ..804
619. FAR 27.1305 Powerplant Instruments. ..805 619A. FAR 27.1305 Powerplant Instruments.. .. 806 619B. FAR 27.1305 Powerplant Instruments.. .. 806
620. FAR 27.1307 Miscellaneous Equipment ..807 XII