FAA AC 20-73 : 2006

1. PURPOSE
2. CANCELLATION
3. APPLICABILITY
4. RELATED ADVISORY CIRCULARS, DOCUMENTS, READING MATERIAL,
    AND NOMENCLATURE
5. ICE PROTECTION REGULATORY DEVELOPMENT BACKGROUND
6. APPLICABLE AIRFRAME, ENGINE, AND PROPELLER ICE PROTECTION
    REQUIREMENTS
    6.1 Ice Protection Requirements: Unintended Exposure to
         Icing Conditions
    6.2 Ice Protection Requirements: Intentional Operations
         in Known and Forecast Icing Conditions
    6.3 Ice Protection Requirements: Operating Safely in
         Icing Conditions
7. CERTIFICATION PROCEDURES
    7.1 Certification Procedures: General
    7.2 Certification Procedures: Airframe Manufacturer
    7.3 Certification Procedures: Engine Manufacturer
8. COMPLIANCE MEANS
    8.1 Compliance Means: Analysis
    8.2 Compliance Means: Tests
    8.3 Compliance Means: Surfaces Without Ice Protection
    8.4 Compliance Means: Ice Inspection Lights and Cues
    8.5 Compliance Means: Reference to Previously
         Accomplished Tests
    8.6 Compliance Means: Perform Intended Function
         Icing Conditions
9. AIRPLANE LIGHT MANUAL (AFM)
    9.1 AFM: Limitations
    9.2 AFM: Operating Procedures
    9.3 AFM: Performance Information
    9.4 AFM: Airworthiness Directives for Severe Icing
         Conditions
10. ROTORCRAFT
    10.1 Rotorcraft: General
    10.2 Rotorcraft: Compliance
    10.3 Rotorcraft Flight Manual
11. AIRCRAFT FROST AND CLEAR ICE CONSIDERATIONS
12. AIRPLANE DE/ANTI-ICING BEFORE TAKEOFF
13. EXTENDED RANGE OPERATION WITH TWO-ENGINE AIRPLANES (ETOPS)
    ICING CONSIDERATIONS
14. REFERENCES
APPENDIX A - RELATED REGULATIONS AND DOCUMENTS
    A.1 Regulations
    A.2 Advisory Circulars
    A.3 Related Reading Material
APPENDIX B - NOMENCLATURE
    B.1 Terms
    B.2 Acronyms and Symbols
    B.3 References
APPENDIX C - BACKGROUND OF ICE PROTECTION REGULATORY DEVELOPMENT
    C.1 Transport Category Airplanes (14 CFR Part 25)
    C.2 Normal, Utility, Acrobatic, and Commuter Category
         Airplanes (14 CFR Part 23)
    C.3 Aircraft Engines (14 CFR Part 3)
    C.4 Rotorcraft (14 CFR Parts 27 and 9)
    C.5 References
APPENDIX D - COMPONENT CE PROTECTION SYSTEM DESIGN AND
             CERTIFICATION PROCESS FLOWCHARTS
APPENDIX E - METEOROLOGICAL CONDITIONS
    E.1 Icing Cloud Specifications
    E.2 Using 14 CFR Parts 5 and 29, Appendix C
    E.3 References
APPENDIX F - OPERATIONAL FACTORS
    F.1 Airplane Operational Factors
    F.2 Rotorcraft Operational Factors
    F.3 Engine Operational Factors
APPENDIX G - ICING CONDITIONS EXPOSURE TIME
APPENDIX H - ICE PROTECTION SYSTEMS
    H.1 Ice Protection Technologies and Operating Modes
    H.2 References
APPENDIX I - DROP IMPINGEMENT AND WATER CATCH
    I.1 Drop Impingement and Water Catch
    I.2 References
APPENDIX J - PROPELLER ICE PROTECTION
    J.1 Propeller Ice Protection
    J.2 References
APPENDIX K - ICE AND ICING CONDITIONS DETECTION
    K.1 Ice and Icing Conditions Detection
    K.2 Installation Location
    K.3 System Considerations
    K.4 Certification of Ice Detectors
    K.5 References
APPENDIX L - WINDSHIELD CE PROTECTION
APPENDIX M - FINDING NATURAL ICING CONDITIONS FOR TEST PURPOSES
    M.1 Background
    M.2 Statistical Guidance
    M.3 Experience
    M.4 Using Forecasts of Icing Conditions
    M.5 Professional Guidance
    M.6 References
APPENDIX N - INSTRUMENTATION
    N.1 Instrumentation
    N.2 References
APPENDIX O - WAYS TO EVALUATE ICING EXPOSURES RELATIVE TO
             APPENDIX C
    O.1 Background
    O.2 Appendix C Converted to Distance- or Time-Based
         Envelopes
    O.3 References
APPENDIX P - USING ICING RATE TO DOCUMENT ICING EXPOSURES
    P.1 Background
    P.2 Data From an Icing Rate Sensor
    P.3 Converting Icing Rate to Icing Intensity
    P.4 Data a Sheet for Documenting Icing Exposures
    P.5 References
APPENDIX Q - ICE SHEDDING
    Q.1 Ice Shedding
    Q.2 References
APPENDIX R - ICE SHAPES
    R.1 Protected Surfaces
    R.2 Unprotected Surfaces
    R.3 Ice Protection System Failure Ice Shapes
    R.4 Critical Ice Shapes
    R.5 Methods for Determining (Predicting) Ice Shapes
    R.6 Correlation of Predicted (Simulated) and Natural
         Ice Shapes
    R.7 References
APPENDIX S - ICE-CONTAMINATED HORIZONTAL STABILIZER
             (TAILPLANE) STALL
    S.1 Ice-Contaminated Horizontal Stabilizer (Tailplane) Stall
    S.2 References
APPENDIX T - ARTIFICIAL ICING FLIGHT TESTS: ICING TANKERS AND
             SPRAY RIG TESTS
    T.1 Icing Tanker Tests
    T.2 Spray Rig Tests
    T.3 References
APPENDIX U - ICING WIND TUNNEL TESTS
    U.1 Icing Wind Tunnel Tests
    U.2 References
APPENDIX V - AIRCRAFT FROST AND CLEAR ICE CONSIDERATIONS
    V.1 Aircraft Frost and Clear Ice Considerations
    V.2 References

Specifies type certificate and supplemental type certificate applicants how to comply with the ice protection requirements of Title 14 of the Code of Federal Regulations (14 CFR) parts 23, 25, 27, 29, 33, and 35. It also provides guidance for aircraft type certificate holders on how to maintain the aircraft's airworthiness when operating in an icing environment.