AC 27.1B, Chg 4 5/1/2014
• Paragraphs that do not correspond with a FAR number either remain in Chapter 3 and are renumbered as MG paragraphs, or are now an appendix.
• In order to stay aligned with FAR numbering, Appendices A and C are reserved for future AC material.
b. Paragraphs revised to incorporate technical guidance are AC 21.35, 27.561, 27.952, 27.1305,
27.1309, 27.1351, 27.1353, MG 2, and MG 4 (FADEC). AC 27.661, Rotorblade Clearance, contains new material added as a result of National Transportation Safety Board NTSB) recommendations.
c. New paragraphs added are AC 27.1B and 27.2A, Gross Weight; AC 27.602, Critical Parts; and AC MG 12, External Loads. These paragraphs correspond with recent harmonized regulatory changes.
d. The AC is now divided by Subparts and page numbers reflect the relevant FAR Subpart.
e. "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 that 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.
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Order 0 Perica Fa erica sort erd desion erectorate far wit Order 8110.4, 1ype Certificatior Eric Bries Acting Manager, Rotorcraft Directorate Aircraft Certification Service Page ili
CONTENTS Page No.
CHAPTER 1 - PART 21 CERTIFICATION PROCEDURES FOR
PRODUCTS AND PARTS AC 21.16 Special Conditions ...... FAR 21-1 AC 21.31 Type Design................. FAR 21-2 AC 21.33 Inspection and Tests... .FAR 21-2 AC 21.35 Flight Tests..... FAR 21-2 AC 21.39 Flight Test Instrument Calibration and Correction Report FAR 21-6 CHAPTER 2 - PART 27 AIRWORTHINESS STANDARDS:
NORMAL CATEGORY ROTORCRAFT
SUBPART A
GENERAL AC 27.1 Applicability .. A-1 AC 27.1A Applicability ... A-1
AC 27.1B ApplicabilityA-2
AC 27.2 Special Retroactive Requirements. A-2 AC 27.2A Special Retroactive Requirements A-4
SUBPART B - FLIGHT
GENERAL
AC 27.21 Proof of ComplianceB-1
AC 27.25 Weight Limits... B-3 AC 27.25A Weight Limits.. B-4 AC 27.27 Center of Gravity Limits.. B-4.2 AC 27.29 Empty Weight and Corresponding Center of Gravity. B-6.2
AC 27.31 Removable BallastB-7
AC 27.33 Main Rotor Speed and Pitch Limits B-7
PERFORMANCE AC 27.45 Performance - General. B-9 AC 27.45A General .. B-18
AC 27.45B GeneralB-18
AC 27.45C Performance - General B-18 Page No.
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AC 27.1B, Chg 9 6/23/23 SUBPART B - FLIGHT (continued) PERFORMANCE (continued) AC 27.49 Performance at Minimum Operating Speed. B-24.2 AC 27.51 Takeoff... B-25 AC 27.51A Takeoff... B-26 AC 27.65 Climb: All Engines Operating B-26.2 AC 27.65A Climb: All Engines Operating B-28 AC 27.67 Climb: One Engine Inoperative B-28 AC 27.71 Autorotation Performance B-29 AC 27.73 Performance at Minimum Operating Speed. B-32 AC 27.75 Landing ..... B-34.1 AC 27.75A Landing .. B-35 AC 27.79 Limiting Height - Speed Envelope B-37 AC 27.79A Limiting Height - Speed Envelope B-45 AC 27.87 Height-Speed Envelope. B-45 AC 27.87A Height-Velocity Envelope. B-45.1
FLIGHT CHARACTERISTICS AC 27.141 Flight Characteristics - General B-46 AC 27.143 Controllability and Maneuverability B-48 AC 27.143A Controllability and Maneuverability B-52.2 AC 27.151 Flight Controls. B-52.8 AC 27.161 Trim Control .. B-53 AC 27.171 Stability: General B-53 AC 27.173 Static Longitudinal Stability. B-54 AC 27.173A Static Longitudinal Stability. B-55 AC 27.175 Demonstration of Static Longitudinal Stability. B-58 AC 27.175A Demonstration of Static Longitudinal Stability B-60.2 AC 27.177 Static Directional Stability. B-60.6 AC 27.177A Static Directional Stability. B-60.7
GROUND AND WATER HANDLING CHARACTERISTICS AC 27.231 Ground and Water Handling Characteristics - General B-61
AC 27.235 Taxiing ConditionB-61
AC 27.239 Spray Characteristics.. B-62
AC 27.241 Ground ResonanceB-63
MISCELLANEOUS FLIGHT REQUIREMENTS
AC 27.251 VibrationB-68
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SUBPART C - STRENGTH REQUIREMENTS
GENERAL
AC 27.301 LoadsC-1
AC 27.303 Factor of SafetyC-1
AC 27.305 Strength and Deformation C-2
AC 27.307 Proof of StructureC-2
AC 27.307A Proof of StructureC-3
AC 27.309 Design LimitationsC-4
FLIGHT LOADS AC 27.321 Flight Loads - General.. C-5 AC 27.337 Limit Maneuvering Load Factor C-5 AC 27.339 Resultant Limit Maneuvering Loads C-8 AC 27.341 Gust Loads.. C-8 AC 27.351 Yawing Conditions .. C-9 AC 27.361 Engine Torque.. C-14
CONTROL SURFACE AND SYSTEM LOADS AC 27.391 Control Surface and System Loads - General. C-15 AC 27.391A Control Surface and System Loads - General C-15 AC 27.395 Control System.. C-15 AC 27.395A Control System.. C-17 AC 27.397 Limit Pilot Forces and Torques. C-17
AC 27.399 Dual Control SystemC-18
AC 27.401 Auxiliary Rotor Assemblies C-18 AC 27.401A Auxiliary Rotor Assemblies C-20 AC 27.403 Auxiliary Rotor Attachment Structure C-20 AC 27.403A Auxiliary Rotor Attachment Structure C-21 AC 27.411 Ground Clearance: Tail Rotor Guard C-21 AC 27.413 Stabilizing and Control Surfaces C-22 AC 27.413A Stabilizing and Control Surfaces C-24 AC 27.427 Unsymmetrical Loads... C-24
GROUND LOADS AC 27.471 Ground Loads - General C-28 AC 27.473 Ground Loading Conditions and Assumptions. C-28 AC 27.475 Tires and Shock Absorbers. C-29 AC 27.477 Landing Gear Arrangement C-29 Page v
AC 27.1B, Chg 4 5/1/2014 Page No.
SUBPART C - STRENGTH REQUIREMENTS (continued) GROUND LOADS (continued) AC 27.479 Level Landing Conditions C-29 AC 27.481 Tail-Down Landing Conditions C-30 AC 27.483 One-Wheel Landing Conditions C-31 AC 27.485 Lateral Drift Landing Conditions C-31 AC 27.493 Braked Roll Conditions. C-32 AC 27.497 Ground Loading Conditions: Landing Gear With Tail Wheels C-32 AC 27.501 Ground Loading Conditions: Landing Gear With Skids. C-34 AC 27.501A Ground Loading Conditions: Landing Gear With Skids. C-35 AC 27.505 Ski Landing Conditions C-35
WATER LOADS AC 27.521 Float Landing Conditions C-37
MAIN COMPONENT REQUIREMENTS
AC 27.547 Main Rotor StructureC-38
AC 27.549 Fuselage, Landing Gear, and Rotor Pylon Structure C-38
EMERGENCY LANDING CONDITIONS AC 27.561 Emergency Landing Conditions - General C-40 AC 27.561A Emergency Landing Conditions - General C-41 AC 27.561B Emergency Landing Conditions - General C-42 AC 27.561C Emergency Landing Conditions - General C-43 AC 27.562 Emergency Landing Dynamic Conditions C-44 AC 27.563 Structural Ditching Provisions C-81 AC 27.563A Structural Ditching Provisions C-81
FATIGUE EVALUATION AC 27.571 Fatigue Evaluation of Flight Structure C-83
AC 27.571A Fatigue Evaluation of Flight Structure for Category A CertificationC-86
AC 27.573 Damage Tolerance and Fatigue Evaluation of Composite.. C-88 Rotorcraft Structures Page vi
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SUBPART D - DESIGN AND CONSTRUCTION
GENERAL AC 27.601 Design... D-1 AC 27.602 Critical Parts... D-2 AC 27.603 Materials .. D-4
AC 27.605 Fabrication MethodsD-4
AC 27.607 Fasteners ... D-6 AC 27.609 Protection of Structure. D-6
AC 27.610 Lightning ProtectionD-8
AC 27.611 Inspection Provisions .. D-11 AC 27.613 Material Strength Properties and Design Values. D-13 AC 27.613A Material Strength Properties and Design Values. D-14 AC 27.619 Special Factors . D-16 AC 27.621 Casting Factors. D-17 AC 27.623 Bearing Factors. D-27 AC 27.625 Fitting Factors. D-28 AC 27.625A Fitting Factors D-29 AC 27.629 Flutter. D-29 ROTORS AC 27.653 Pressure Venting and Drainage of Rotor Blades. D-31 AC 27.659 Mass Balance.. D-31 AC 27.661 Rotor Blade Clearance. D-31 AC 27.663 Ground Resonance Prevention Means .. D-33 AC 27.663A Ground Resonance Prevention Means D-35
CONTROL SYSTEMS AC 27.671 Control Systems - General D-36 AC 27.672 Stability Augmentation, Automatic, and Power-Operated Systems... D-36 AC 27.673 Primary Flight Control .. D-37 AC 27.674 Interconnected Controls D-37
AC 27.675 StopsD-38
AC 27.679 Control System Locks.. D-40 AC 27.681 Limit Load Static Tests. D-40.1 AC 27.683 Operation Tests.. D-41 AC 27.685 Control System Details. D-41 AC 27.685A Control System Details. D-42 AC 27.687 Spring Devices .. D-43 AC 27.691 Autorotation Control Mechanism. D-43 AC 27.695 Power Boost and Power-Operated Control System D-44 Page vii
AC 27.1B, Chg 4 5/1/2014 Page No.
SUBPART D - DESIGN AND CONSTRUCTION (continued)
LANDING GEAR AC 27.723 Shock Absorption Tests D-47
AC 27.725 Limit Drop TestD-50
AC 27.727 Reserve Energy Absorption Drop Test.. D-50 AC 27.727A Reserve Energy Absorption Drop Test. D-51 AC 27.729 Retracting Mechanism D-51
AC 27.731 WheelsD-54
AC 27.733 TiresD-55
AC 27.735 Brakes...D-56
AC 27.737 Skis . D-58
FLOATS AND HULLS AC 27.751 Main Float Buoyancy... D-59 AC 27.753 Main Float Design. D-60 AC 27.755 Hulls D-60
PERSONNEL AND CARGO ACCOMMODATIONS AC 27.771 Pilot Compartment D-62 AC 27.773 Pilot Compartment View D-63 AC 27.775 Windshields and Windows D-68 AC 27.775A Windshields and Windows D-68 AC 27.777 Cockpit Controls. D-68 AC 27.779 Motion and Effect of Cockpit Controls D-69 AC 27.783 Doors . D-72.2 AC 27.783A Doors . D-74 AC 27.785 Seats, Berths, Safety Belts, and Harnesses. D-74 AC 27.785A Seats, Berths, Safety Belts, and Harnesses D-78 AC 27.785B Seats, Berths, Litters, Safety Belts, and Harnesses D-80 AC 27.787 Cargo and Baggage Compartments. D-80 AC 27.787A Cargo and Baggage Compartments. D-82 AC 27.801 Ditching .. D-82 AC 27.805 Flight Crew Emergency Exits D-91 AC 27.807 Emergency Exits .. D-91 AC 27.807A Emergency Exits .. D-93 AC 27.807B Emergency Exits . D-93 AC 27.831 Ventilation .. D-94 AC 27.833 Heaters .. D-96 Page vili
AC 27-1B, Chg 9 6/23/23 Page No.
SUBPART D - DESIGN AND CONSTRUCTION (continued)
FIRE PROTECTION AC 27.853 Compartment Interiors. D-98 AC 27.853A Compartment Interiors D-99 AC 27.855 Cargo and Baggage Compartments.. D-99 AC 27.859 Heating Systems... D-101 AC 27.861 Fire Protection of Structure, Controls, and Other Parts D-105 AC 27.861A Fire Protection of Structure, Controls, and Other Parts D-106 AC 27.863 Flammable Fluid Fire Protection D-107
EXTERNAL LOADS AC 27.865 External Load Attaching Means D-109 AC 27.865A External Load Attaching Means D-110 AC 27.865B External Loads (previously MG 12) D-111
MISCELLANEOUS AC 27.871 Leveling Marks. D-133 AC 27.873 Ballast Provisions. D-133
SUBPART E - POWERPLANT
GENERAL AC 27.901 Installation. E-1 AC 27.901A Installation E-5 AC 27.903 Engines. E-5.2 AC 27.903A Engines E-7 AC 27.903B Engines . E-9 AC 27.903C Engines. E-10.1 AC 27.907 Engine Vibration E-10.1a
ROTOR DRIVE SYSTEM AC 27.917 Design.. E-10.2 AC 27.921 Rotor Brake. E-11 AC 27.923 Rotor Drive System and Control Mechanism Tests E-12 AC 27.923A Rotor Drive System and Control Mechanism Tests E-17 AC 27.923B Rotor Drive System and Control Mechanism Tests E-18 AC 27.927 Additional Tests.. E-19 AC 27.927A Additional Tests.. E-21 AC 27.931 Shafting Critical Speeds. E-21 Page ix
AC 27-1B, Chg 4 5/1/2014 Page No.
SUBPART E - POWERPLANT (continued) ROTOR DRIVE SYSTEM (continued) AC 27.935 Shafting Joints... E-26 AC 27.939 Turbine Engine Operating Characteristics E-26
FUEL SYSTEM AC 27.951 Fuel System - General E-29 AC 27.952 Fuel System Crash Resistance.
AC 27.953 Fuel System Independence E-56 AC 27.954 Fuel System Lightning Protection E-57 AC 27.955 Fuel Flow E-58 AC 27.955A Fuel Flow E-62 AC 27.959 Unusable Fuel Supply .. E-64 AC 27.961 Fuel System Hot Weather Operation E-65 AC 27.961A Fuel System Hot Weather Operation E-67
AC 27.963 Fuel Tanks: GeneralE-67
AC 27.963A Fuel Tanks: GeneralE-68
AC 27.963B Fuel Tanks: General... E-68 AC 27.965 Fuel Tank Tests. E-69 AC 27.967 Fuel Tank Installation.. E-70 AC 27.969 Fuel Tank Expansion Space. E-72 AC 27.969A Fuel Tank Expansion Space E-72 AC 27.971 Fuel Tank Sump.. E-73 AC 27.971A Fuel Tank Sump.. E-74 AC 27.973 Fuel Tank Filler Connection E-74 AC 27.973A Fuel Tank Filler Connection E-75 AC 27.975 Fuel Tank Vents. E-76 AC 27.975A Fuel Tank Vents. E-77 AC 27.975B Fuel Tank Vents.. E-77 AC 27.977 Fuel Tank Outlet.. E-78
FUEL SYSTEM COMPONENTS AC 27.991 Fuel Pumps E-80 AC 27.991A Fuel Pumps E-81 AC 27.993 Fuel System Lines and Fittings. E-81 AC 27.995 Fuel Valves E-82 AC 27.997 Fuel Strainer or Filter ... E-82 AC 27.997A Fuel Strainer or Filter ... E-83 AC 27.999 Fuel System Drains. E-84 AC 27.999A Fuel System Drains. E-85 Page x
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SUBPART E - POWERPLANT (continued)
OIL SYSTEM AC 27.1011 Engines - General ... E-86 AC 27.1013 Oil Tanks.. E-86 AC 27.1015 Oil Tank Tests .. E-87 AC 27.1017 Oil Lines and Fittings... E-88 AC 27.1019 Oil Strainer or Filter... E-88 AC 27.1019A Oil Strainer or Filter... E-89
AC 27.1021 Oil System DrainsE-90
AC 27.1027 Transmission and Gearboxes: General. E-90
COOLING AC 27.1041 Cooling - General E-92 AC 27.1041A General . E-94 AC 27.1043 Cooling Tests. E-94 AC 27.1045 Cooling Test Procedures E-97 AC 27.1045A Cooling Test Procedures E-98
INDUCTION SYSTEM AC 27.1091 Air Induction E-99 AC 27.1091A Air Induction E-100 AC 27.1093 Induction System Icing Protection E-101 AC 27.1093A Induction System Icing Protection E-112.1
EXHAUST SYSTEM AC 27.1121 General .. E-113 AC 27.1123 Exhaust Piping .. .. E-114
POWERPLANT CONTROLS AND ACCESSORIES AC 27.1141 Powerplant Controls: General E-117 AC 27.1141A Powerplant Controls: General E-118 AC 27.1143 Engine Controls.. E-118 AC 27.1143A Engine Controls. E-119 AC 27.1143B Engine Controls. E-119 AC 27.1145 Ignition Switches. E-120 AC 27.1147 Mixture Controls.. E-120
AC 27.1151 Rotor Brake ControlsE-121
AC 27.1163 Powerplant Accessories E-122 Page No.
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AC 27-1B 029/23 6/23/23 SUBPART E - POWERPLANT (continued)
POWERPLANT FIRE PROTECTION AC 27.1183 Lines, Fittings, and Components. E-124 AC 27.1185 Flammable Fluids.. E-125 AC 27.1187 Ventilation and Drainage E-126 AC 27.1189 Shutoff Means.. E-127 AC 27.1191 Firewalls .. E-128 AC 27.1193 Cowling and Engine Compartment Covering .. E-132 AC 27.1193A Cowling and Engine Compartment Covering E-133 AC 27.1194 Other Surfaces. E-134 AC 27.1195 Fire Detector Systems.. E-135
SUBPART F - EQUIPMENT
GENERAL AC 27.1301 Function and Installation F-1 AC 27.1303 Flight and Navigation Instruments. F-1 AC 27.1305 Powerplant Instruments F-7 AC 27.1305A Powerplant Instruments F-8 AC 27.1305B Powerplant Instruments F-9 AC 27.1305C Powerplant Instruments F-11.1 AC 27.1307 Miscellaneous Equipment F-12 AC 27.1309 Equipment, Systems, and Installations.. F-13 AC 27.1309A Equipment, Systems, and Installations. F-30 AC 27.1309B Equipment, Systems, and Installations F-30.1 AC 27.1316 Electrical and Electronic System Lightning Protection F-31 AC 27.1317 High-Intensity Radiated Fields (HIRF) Protection F-32 INSTRUMENTS: INSTALLATION AC 27.1321 Arrangement and Visibility. _ F-34 AC 27.1322 Warning, Caution, and Advisory Lights F-34.2 AC 27.1323 Airspeed Indicating System F-39 AC 27.1325 Static Pressure Systems F-40 AC 27.1327 Magnetic Direction Indicator F-41 AC 27.1329 Automatic Pilot System F-41 AC 27.1329A Automatic Pilot System F-51 AC 27.1329B Automatic Pilot System and Flight Guidance System F-52.1 AC 27.1335 Flight Director Systems F-53 AC 27.1335A Flight Director Systems. F-54.1 AC 27.1337 Powerplant Instruments F-54.2 AC 27.1337A Powerplant Instruments F-54.3 Page xii