AC 23.1419-2C

Subject: Certification of Part 23 Airplanes for Flight in Icing Conditions

Date: 7/21/04 Initiated By: ACE-100

AC No: 23.1419-2C Change:

1. PURPOSE. This Advisory Circular (AC) sets forth an acceptable means, but not the only means, of demonstrating compliance with the ice protection requirements in Title 14 of the Code of Federal Regulations (14 CFR) part 23. The Federal Aviation Administration (FAA) will consider other methods of demonstrating compliance that an applicant may elect to present. This material is neither mandatory nor regulatory in nature and does not constitute a regulation.

2. CANCEL LATION. AC 23.1419-2B, Certification of Part 23 Airplanes for Flight in Icing Conditions, dated September 26, 2002, is canceled. In addition, all policy related to the certification of ice protection systems on part 23 airplanes, issued prior to this AC is cancelled.

3. APPLICABILITY. The guidance provided here applies to the approval of airplane ice protection systems for operating in the icing environment defined by part 25, Appendix C. The guidance should be applied to new Type Certificates (TCs), Supplemental Type Certificates (STCs), and amendments to existing TCs for airplanes under part 3 of the Civil Aviation Regulations (CAR) and part 23, for which approval under the provisions of § 23.1419 is desired.

S/

Dorenda D. Baker Manager, Small Airplane Directorate Aircraft Certification Service

CONTENTS

Paragraph Page

1. Purposei

2. Cancellationi

3. Applicabilityi

4. Related Regulations and Documents1

5. Related Reading Material4

6. Background6

7. Planning8

8. Design Objectives9

9. Analyses and Ground Testing9

10. Flight Test Planning19

11. Flight Tests20

12. Performance and Flying Qualities30

13. Ice Shedding44

14. Placarding and AFM45

15. Instructions for Continued Airworthiness48

Appendix A DefinitionsA-1

Appendix B Guidelines for Determining Certification Basis on Flight in Icing

Approval STCs and Amended TCsB-1

Appendix C Guidelines for Supplemental Type Certificates (STC) and

Amended Type Certificates on AirplanesC-1

Appendix D Guidelines for Certifying Ice Protection Systems on Airplanes

Not for Flight in Icing Approval (“Non-Hazard” Basis)D-1

Appendix E Guidelines for Approval of Replacement Parts for Airframe

Deicing SystemsE-1

Appendix F ChecklistF-1

Appendix G Part 23 Subpart B Tests for Section 23.1419 at Amendment 23-43G-1

Appendix H AFM Limitations and Normal Procedures SectionsH-1

TABLES

Number Title Page

1 Flight In Icing Requirements1

2 Fluid Capacity18

3 Ice Accretion Definitions34

4 Natural Icing Performance and Handling Qualities Tests38

5 Flight Test Tolerances38

6 Failure Ice Accretion Flight Tests41

E-1 Summary of Test Requirements for Replacement of

Airframe Deicing ComponentsE-1

F-1 ChecklistF-1

G-1 Part 23 Subpart B Tests for Section 23.1419 at Amendment 23-43 ... G-1 ii

4. RELATED REGULATIONS AND DOCUMENTS.

a. Regulations. By their adoption in amendment 23-14, which shows their requirements are directly related, §§ 23.929, 23.1309, and 23.1419 are applicable to a part 23 airplane icing certification program regardless of the certification basis for the basic airplane; however, for those airplanes certificated in accordance with part 3 of the CAR and part 23 through amendment 23-13, the application of these sections may be limited to the equipment being used for ice protection. Some systems that were previously approved on the airplane may need to be modified to improve their reliability when those systems are utilized as part of that airplane's icing approval.

(1) With the adoption of amendment 23-43, § 23.1419 was revised to do the following:

to specify that the performance, controllability, maneuverability, and stability must not be less than that required by subpart B of part 23; add the requirement for flight testing in measured, natural icing conditions; provide specific test requirements; clarify the requirements for information that must be provided to the pilot, and allow approval of equivalent components that have been previously tested and approved, and that have demonstrated satisfactory service if the installations are similar.

(2) Prior to the adoption of amendment 23-43, some part 23 airplanes were certificated for flight in icing using § 25.1419.

(3) In addition to the previously mentioned requirements (§§ 23.929, 23.1309, and

23.1419), the following sections should be applied depending upon the ice protection system design and the original certification basis of the airplane. Many of the following requirements in Table 1 are also applicable, even without approval for flight in icing conditions. Further guidance on establishing a certification basis for flight in icing approval can be found in Appendix B.

TABLE 1. FLIGHT IN ICING REQUIREMENTS

Date of Airplane Type Certification Application CAR/Title 14 CFR Status Icing Certification Requirements Prior to February 1, 1965 Part 3 of the CAR, (May 15, 1956, as amended through amendment 3-8) Sections 3.85(a) and (c),

3.85a(a) and (c), 3.382, 3.383,

3.446, 3.575, (including note following (b)), 3.652, 3.652-1,

3.665, 3.666, 3.681, 3.682,

3.685, 3.686, 3.687, 3.690,

3.691, 3.692, 3.712, 3.725,

3.758, 3.770, 3.772, 3.777,

3.778, and 3.779 1

TABLE 1. FLIGHT IN ICING REQUIREMENTS (Continued)

Date of Airplane Type Certification Application CAR/Title 14 CFR Status Icing Certification Requirements On or after February 1, 1965 Recodification

Sections 23.65, 23.75, 23.77,

23.773, 23.775, 23.1301,

23.1351, 23.1357, 23.1437,

23.1541, 23.1559(b),

23.1583(h), 23.1585, and

23.1419 (boot requirement before amendment 23-14) On or after July 29, 1965 Amendment 23-1 Add § 23.1325 to the above part 23 requirements.

On or after February 5, 1970 Amendment 23-8 Add § 23.1529 to the above part 23 requirements.

On or after December 20, 1973 Amendment 23-14 Add §§ 23.853(d), 23.929 and

23.903(c) to the above part 23 requirements, significant revision to § 23.1419.

On September 1, 1977

Amendment 23-20

Add §§ 23.1327 and 23.1547 to the above part 23 requirements.

On or after December 1, 1978

Amendment 23-23

Add §§ 23.863, and 23.1416 (in lieu of the boot requirement of § 23.1419 before amendment 23-14) to the above part 23 requirements.

On or after February 17, 1987 Amendment 23-34 For commuter category airplanes, add §§ 23.67(e)(2),

23.67(e)(3), 23.997(e), and

23.1199(b) to the above part 23 requirements.

On or after February 4, 1991

Amendment 23-42

Add §§ 23.1323(e) and

23.1325(g) to the above part 23 requirements.

TABLE 1. FLIGHT IN ICING REQUIREMENTS (Continued)

Date of Airplane Type Certification Application CAR/Title 14 CFR Status Icing Certification Requirements On or after May 10, 1993

Amendment 23-43

Add §§ 23.905(e),

23.1093(a)(6), and 23.1307(c) to the above part 23 requirements; significant revision to § 23.1419, added Subpart B sections and natural icing flight test requirement.

On or after September 7, 1993

Amendment 23-45

Add §§ 23.773(b), 23.775(f),

23.775(g), and 23.1525 to the above part 23 requirements.

On or after March 11, 1996 Amendment 23-49 Add § 23.1326 to the above part 23 requirements.

b. Advisory Circulars. Copies of current editions of the following publications may be downloaded from the FAA's Regulatory and Guidance Library (RGL) www.airweb.faa.gov/AC or obtained from the U.S. Department of Transportation, Subsequent Distribution Office, Ardmore East Business Center, 3341 Q 75th Avenue, Landover, MD 20785:

AC 20-73 “Aircraft Ice Protection,” April 21, 1971.

AC 20-115B “Radio Technical Commission for Aeronautic, Inc. Document RTCA/DO-178B,” January 11, 1993.

AC 20-117 “Hazards Following Ground Deicing and Ground Operations in Conditions Conducive to Aircraft Icing,” December 3, 1982.

AC 20-147 “Turbojet, Turboprop, and Turbofan Engine Induction System Icing and Ice Ingestion,” February 2, 2004.

AC 21-16D “RTCA Document DO-160D,” July 21, 1978.

AC 21-40 “Application Guide for Obtaining a Supplemental Type Certification,” May 6, 1998.

AC 21.101-1 Establishing the Certification Basis of Changed Aeronautical Products,” April 28, 20003.

AC 23-16A “Powerplant Guide for Certification of Part 23 Airplanes and Airships,” February 3, 2004.

AC 23-17A “Systems and Equipment Guide for Certification of Part 23 Airplanes,” June 27, 2002.

AC 23.143-1 “Ice Contaminated Tailplane Stall (ICTS),” December 20, 2001.

AC 23.629-1A “Means of Compliance with Section 23.629, Flutter,” October 23, 1985.

AC 23.1309-1C “Equipment, Systems, and Installations in Part 23 Airplanes,” March 23, March 12, 1999.

AC 91-74 “Pilot Guide Flight in Icing Conditions,” December 12, 2002.

Copies of the current AC may be purchased from the Superintendent of Documents, P.O.

Box 371954, Pittsburgh, PA 15250-7954. Make check or money order payable to the Superintendent of Documents:

AC 23-8B “Flight Test Guide for Certification of Part 23 Airplanes,” August 14, 2003.

5. RELATED READING MATERIAL.

a. FAA Orders.

FAA Order 8110.4B, “Type Certification,” April 24, 2000.

b. FAA Technical Reports. The following FAA technical reports can be obtained from the National Technical Information Service in Springfield, Virginia 22161:

(1) FAA Technical Report DOT/FAA/CT-88/8, "Aircraft Icing Handbook" (March 1991), includes reference material on ground and airborne icing facilities, simulation procedures, and analytical techniques. This document represents all types and classes of aircraft and is intended as a working tool for the designer and analyst of ice protection systems.

(2) FAA Technical Report ADS-4, "Engineering Summary of Airframe Icing Technical Data," and Report No., FAA-RD-77-76, "Engineering Summary of Powerplant Icing Technical Data," provide technical information on airframe and engine icing conditions, and methods of detecting, preventing, and removing ice accretion on airframes and engines in flight. Although most of the information contained in ADS-4 and FAA-RD-77-76 reports is still valid, some is outdated, and more usable information is now available through recent research and experience, and is included in the Aircraft Icing Handbook.

(3) FAA Technical Report DOT/FAA/AR-01/91, "A History and Interpretation of Aircraft Icing Intensity Definitions and FAA Rules for Operating in Icing Conditions" (November 2001), provides a good reference for understanding icing operational rules.

(4) FAA Technical Report DOT/FAA/AR-02/68, "Effect of Residual and Intercycle Ice Accretions on Airfoil Performance" (May 2002), details icing tunnel testing to determine intercycle and residual ice on a 23012 airfoil, and wind tunnel testing of uniform sandpaper and intercycle ice shapes.

(5) FAA Technical Report DOT/FAA/CT-TN86/11, “Fluid Ice Protection Systems.”

c. Technical Standard Order (TSO): A copy of the current edition of the following publication may be obtained from the Federal Aviation Administration, Aircraft Certification Service, Aircraft Engineering Division, Technical Programs and Continued Airworthiness Branch—AIR-120, 800 Independence Avenue, SW, Washington, DC 20591 or from the FAA website at www.faa.gov:

TSO-C16 “Air-Speed Tubes (Electrically Heated),” September 1, 1948.

TSO-C54 “Stall Warning Instruments,” October 15, 1961.

d. SAE Documents. The Society of Automotive Engineers (SAE), Inc. Aerospace Recommended Practice (ARP) and Aerospace Information Report (AIR) documents are available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001 or from their website at www.sae.org:

ARP4761 “Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment,” December 1, 1996.

AIR4367 “Aircraft Ice Detectors and Icing Rate Measuring Instruments, “April 1, 1995.

AIR5504 “Aircraft Inflight Icing Terminology,” September 17, 2002.

AIR1168/4 “Ice, Rain, Fog, and Frost Protection,” July 1, 1989.

ARP4087 “Wing Inspection Lights – Design Criteria,” April 1, 1996.

AS393 “Airspeed Tubes Electrically Heated,” August 14, 2002.

AS403 “Stall Warning Instruments,” July 15, 1958.

The SAE and a working group for Task 11A of the FAA Inflight Aircraft Icing Plan have developed the following documents:

ARP5903 “Droplet Impingement and Ice Accretion Computer Codes, October 16, 2003.

ARP5904 “Airborne Icing Tankers,” October 21, 2002.

ARP5905 “Calibration and Acceptance of Icing Wind Tunnels,” September 18, 2003.

e. Miscellaneo us Documents.

(1) British Specification (BS) 2G-135, “Specification for Electrically-Heated Pitot and Pitotstatic Pressure Heads”

(2) American Society for Testing and Materials (ASTM) G76-95, “Standard Test Method for Conducting Erosion Tests by Solid Particle Impingement Using Gas Jets”

6. BACKGROUND.

a. Prior to 1945, airplanes were certificated under part 4 of the CAR. Section 04.5814 required that if deicer boots were installed, they would have a positive means of deflation. There were no other references to an ice protection system in part 4. When separate regulations (part 3 of the CAR) were written for normal category airplanes, this requirement for positive means of deflating deicer boots was incorporated without change in § 03.541. In 1949, § 03.541 was renumbered as § 3.712.

b. Ice protection was not addressed again until part 3 of the CAR was revised in 1962 by amendment 3-7. This amendment added §§ 3.772 and 3.778, which required that information be provided to the crew specifying the types of operation and the meteorological conditions to which the airplane is limited by the equipment installed. This section gave icing as a specific example of the meteorological conditions to be delineated. This change required a list of all installed equipment affecting the airplane operation limitations. The list also identified this equipment by its operational function. This list of equipment later became known as the “Kind of Equipment List (KOEL).”

c. In 1964, part 3 of the CAR was recodified into part 23. After recodification, § 3.712 became § 23.1419, and §§ 3.772 and 3.778(h) became §§ 23.1559 and 23.1583(h). In 1965, § 23.1325 was revised by amendment 23-1 to take into account the effect of icing conditions on static pressure dependent instruments. This requirement applies to all airplanes regardless of whether or not they have an ice protection system approved under § 23.1419. In the latter part of 1968, the FAA instituted an extensive review of the airworthiness standards of part 23. As a result of this review, the FAA issued amendment 23-14 (November 1973), which made several substantive changes in the interest of safety to part 23. This amendment introduced a new § 23.929, which required engine installation ice protection and completely revised § 23.1419 to establish standards for ice protection systems. It also introduced a new § 23.1309, which established reliability and noninterference requirements for installed equipment and systems.

These three sections are directly related, as defined in § 21.101, to the certification of an ice protection system because of the increased reliance on this system when operating the airplane in an icing environment.

d. Specific standards for pneumatic deicer boots, which were contained in the former § 23.1419, were inadvertently omitted in amendment 23-14. The FAA, realizing that a specific standard for pneumatic deicer boot systems was needed, issued amendment 23-23 in 1978, which added § 23.1416, pneumatic deicer boot system. As currently configured, certification requirements are limited to those icing conditions produced by supercooled clouds as defined by part 25, Appendix C, and do not require design or proof of capability to operate in freezing rain and drizzle, snow, or mixed conditions.

e. In 1987, with the creation of the commuter category, airplanes that had weight, altitude, and temperature limitations for takeoff, en route, climb, and landing distance were being certificated. Required climb performance for commuter category airplanes is defined in § 23.67(c) and § 23.77(c).

f. With the adoption of amendment 23-41 (effective November 26, 1990), § 23.1309 retained the existing reliability requirements adopted by amendment 23-14 for airplane equipment, systems, and installations that are not complex and do not perform critical functions.

For those cases where the applicant finds it necessary or desirable to include complex systems and/or systems that perform critical functions, amendment 23-41, § 23.1309, provides additional requirements for identifying and certificating such equipment, systems, and installations. This amendment permitted the approval of more advanced systems having the capability to perform critical functions.

g. In 1991, with the adoption of amendment 23-42 (effective February 4, 1991), § 23.1323(e) was added to require a heated pitot tube, or an equivalent means of preventing malfunction due to icing, and to clarify the requirement that a heated pitot tube be part of the system approval for flight in icing conditions. Also, § 23.1325(g) was added to allow airplanes that are prohibited from flight in Instrument Meteorological Conditions (IMC) to be certificated without an alternate static air source.

h. In 1993, with the adoption of amendment 23-43 (effective May 10, 1993), § 23.905(e) was added to require that ice shed from the airplane not damage a pusher propeller.

Section 23.1093(a)(6) specified ice protection requirements for fuel injection system designs with and without metering components on which impact ice may accumulate. Also, § 23.1307(c) was added to require the airplane type design to include all of the equipment necessary for operation in accordance with the limitations required by § 23.1559.

Section 23.1419 was revised to do the following: to specify that the performance, controllability, maneuverability, and stability must not be less than that required by subpart B of part 23; add the requirement for flight testing in measured, natural icing conditions, provide other specific test requirements, and to clarify requirements for certification by similarity.

i. In 1993, with the adoption of amendment 23-45 (effective September 7, 1993), the following sections were added: (1) section 23.773(b) to provide requirements for the pilot compartment view to address the environment expected in all the operations requested for certification; (2) section 23.775(f) to clarify the criteria for determining the cleared windshield area that is necessary to assure safe operation in icing conditions; (3) section 23.775(g) to require that a probable single failure of a transparency heating system may not adversely affect the integrity of the airplane cabin or danger of fire; and (4) section 23.1525 was revised to require the establishment and inclusion of kinds of operations authorized in the Airplane Flight Manual (AFM) as specified by § 23.1583(h).

j. In 1996, with the adoption of amendment 23-49 (effective March 11, 1996), § 23.1325(g) was revised by exempting airplanes that are prohibited from flight in icing conditions from the requirements of § 23.1325(b)(3). Also, § 23.1326 was added to require the installation of a pitot tube heat indicating system on those airplanes required to be equipped with a heated pitot tube.

Airplanes that are approved for instrument flight, or for flight in icing conditions, would be required to be equipped with a heated pitot tube and a heated pitot tube indicator. See AC 23-17A for guidance on compliance to § 23.1326. Section 23.1323(e) was recodified to § 23.1323(d).

7. PLANNING.

a. Flight in Icing Approval. The applicant should submit a certification plan at the start of the design and development efforts. Refer to FAA Order 8110.4B. The certification plan should describe all of the applicant's efforts intended to lead to certification. This plan should identify, by item to be certificated, the certification methods that the applicant intends to use. It should provide for a certification checklist. Regarding § 23.1419, it should clearly identify analyses and tests, or references to similarity of designs that the applicant intends for certification of the ice protection system. These methods of showing compliance should be agreed upon between the applicant and the FAA early in the type certification program. Detailed guidance for STCs or amended TCs on part 23 airplanes approved for flight in icing can be found in Appendix C of this AC. It is imperative that the applicant obtains FAA concurrence prior to conducting certification tests. The certification plan should include the following basic information:

(1) Airplane and systems descriptions, including dimensions, operating envelope and limitations, and other data that may be relevant to certification for flight in icing conditions;

(2) Ice protection systems description;

(3) Compliance checklist that addresses each applicable section of part 23 and the proposed methods of compliance (to be agreed upon between the applicant and the FAA early in the certification program);

(4) Analyses or tests performed to date;

(5) Analyses or tests planned;

(6) Projected schedules of design, analyses, testing, and reporting.

b. Installations without Flight in Icing Approval. There may be times when applicants may want to certificate an ice protection system installation but do not want to obtain flight in icing approval. In the past these systems have been called “non-hazard” installations. This means that the aircraft is prohibited from flight in icing conditions but there is some ice protection to facilitate an exit from an inadvertent icing encounter. Guidance for the approval of these types of ice protection systems can be found in Appendix D of this AC.

c. Replacement Parts for Airframe Ice Protection Systems. The requirements leading to approval of replacement airframe deicing systems or airframe thermal deicing or anti-icing systems are detailed in Appendix E.

8. DESIGN OBJECTIVES. The applicant must demonstrate by analyses and tests that the airplane is capable of safely operating throughout the icing envelope of part 25, Appendix C. The envelope can be reduced for airplanes certificated for operation where systems or performance limitations (e.g., altitude), not related to ice protection, exist.

Appendix F lists various influence items that should be examined for their effect on safety when operating in icing conditions.

9. ANALYSES AND GROUND TESTING. The applicant normally prepares analyses to substantiate decisions involving application of selected ice protection equipment and to substantiate decisions to leave normally protected areas and components unprotected. Such analyses should clearly state the basic protection required, the assumptions made, and delineate the methods of analysis used. All analyses should be validated either by tests or by methods agreed to by the FAA. This substantiation should include a discussion of the assumptions made in the analyses and the design provisions included to compensate for these assumptions. Analyses are normally used for the following:

a. Areas and Components to be Protected. The applicant should examine those areas listed below to determine the degree of protection required:

(1) Leading edges of wings, winglets, and wing struts; horizontal and vertical stabilizers; and other lifting surfaces;

(2) Leading edges of control surface balance areas if not shielded;

(3) Engine induction system and any portion of the airframe from which accumulated ice could be ingested

(4) Accessory cooling air intakes that face the airstream and/or could otherwise become restricted due to ice accretion;

(5) Antennas and masts;

(6) Fuel tank vents;

(7) External tanks, including fuel tip tanks;

(8) Propellers;

(9) External hinges, tracks, door handles, and entry steps;

(10) Instrument transducers including pitot tube (and mast), static ports, angle-of-attack sensors, and stall warning transducers;

(11) Forward fuselage nose cone and radome;

(12) W indshields;

(13) Landing gear;

(14) Retractable forward landing lights;

(15) Ram air turbines;

(16) Ice detection lights if required; and

(17) Any other external protuberance.

An applicant may find that protection is not required for one or more of these areas and components. If so, the applicant should include supporting data and rationale in the analysis for allowing them to go unprotected. The applicant should demonstrate that allowing them to go unprotected does not adversely affect the handling or performance of the airplane.

b. Ice Accretion Analyses.

(1) Impingement Limit Analyses. The applicant should prepare a droplet trajectory and impingement analysis of the wing, horizontal and vertical stabilizers, propellers, and any other leading edges that may require protection. This analysis should consider the various airplane operational configurations and associated angles of attack. This analysis is needed to establish the upper and lower aft droplet impingement limits that can then be used to establish the aft ice formation limit and the extent of the protection surface coverage needed. The largest droplet size within part 25, Appendix C will determine the maximum impingement limits. More specific information can be found in AC 20-73, “Aircraft Ice Protection.”

(2) Critica l Ice Accretions. The critical ice accretions for which operational characteristics are to be evaluated should be determined for each flight phase as discussed in paragraph 12.b. of this AC. The parameters to be considered are the flight conditions (e.g., 10