165 For VFR-only airplanes, an applicant should submit a certification plan that describes the airplane lightning protection design for structure, controls, and systems.
Compliance may be demonstrated by any of the following: Design review, reference to aircraft lightning protection design handbooks, calculations or analysis, lightning test data, or system lightning qualification.
For any other airplane, an applicant should submit a certification test plan describing the analyses or tests to be used to show lightning protection effectiveness. The lightning compliance should, as a minimum, include the following steps:
a. Define the lightning zones for the entire aircraft, and describe the method for determining the zones, such as lightning strike attachment model tests, similarity to previous airplane designs, or service experience.
b. Evaluate the lightning direct effects protection for all flight critical portions of the airframe, flight controls, and propulsion systems. Define the lightning qualification tests and damage assessment procedures. Fuel system lightning protection compliance should be demonstrated by compliance to 23.954.
c. Evaluate lightning indirect effects protection for the airplane and its electrical and avionics systems. Include both upset and damage assessment for the electrical and avionics systems.
d. Define the test procedures, test parameters, analysis methods simulation techniques, and lightning waveforms and test voltages and currents used to demonstrate the lightning protection compliance.
e. Define the airplane grounding and bonding design features, particularly for composite structures. Demonstrate airplane grounding and bonding tolerance to environments such as vibration, temperature and corrosion.
Define instructions for continued airworthiness of the airplane lightning protection, including maintenance practices and repairs for structure.
The following documents are applicable:
AC 20-155, SAE Documents to Support Aircraft Lightning Protection Certification.
This AC states that SAE ARP5412A, Aircraft Lightning Environment and Related Test Waveforms, and ARP5414A, Aircraft Lightning Zoning, are acceptable for certification.
AC 20-53B, Protection of Aircraft Fuel Systems Against Fuel Vapor Ignition Caused by Lightning. This AC addresses ignition hazards caused by direct effects on main and auxiliary fuel tanks, fuel tank components and plumbing, and the indirect effects (upset or damage) on analog or digital electronic and electrical systems that could
Change 1 AC 23-17C 7/16/2012
166 lead to ignition hazards on wires or equipment such as fuel quantity probes located in a fuel tank cavity containing fuel vapor.
AC 20-136A, Protection of Aircraft Electrical / Electronic Systems Against the Indirect Effects of Lightning,” December 21, 2006.
SAE ARP 5412A, “Aircraft Lightning Environment and Related Test Waveforms,” February 21, 2005.
SAE ARP 5414A, “Aircraft Lightning Zoning,” February 16, 2005.
SAE ARP 5415A, “Users Manual for Certification of Aircraft Electrical/Electronic Systems for the Indirect Effects of Lightning,” May 14, 2002.
SAE ARP 5416, “Aircraft Lightning Test Methods, “March 17, 2005.
SAE ARP 5577, "Aircraft Lightning Direct Effects Certification,” September 30, 2002.
Amendment 23-49 and Subsequent
A proposed revision in NPRM 94-21 explains the change in the title of § 23.867 as follows: “This proposed revision would change the heading that precedes the section from "Lightning Evaluation" to "Electrical Bonding and Lightning Protection." It would also revise the section heading form "Lightning protection of structures" to "Electrical bonding and protection against lightning and static electricity." The proposed revisions more accurately clarify the content of the section.”
167 Section 8. Miscellaneous
23.871 Leveling means
The corresponding rule in CAR 3 is CAR 3.401.
The corresponding airworthiness criteria is section 4.50, Airship Design Criteria, FAA-P-8110-2, Change 2.
Amendment 23-7 and Subsequent
The original rule required “reference marks.”
This amendment has the following explanation in NPRM 67-14: “any means, not just reference marks, are acceptable for leveling the airplane on the ground.”
168 Chapter 2 – Subpart F-Equipment
Section 1. General
23.1301 Function and installation
The corresponding rules in CAR 3 are CAR 3.651 and 3.652.
The corresponding airworthiness criteria is section 6.1, Airship Design Criteria, FAA- P-8110-2, Change 2.
Original Issue and Subsequent
Bench level environmental testing is required for Technical Standard Order Authorizations. It is acceptable data for Type Certificate, Amended Type Certificate, Supplemental Type Certificate and Parts Manufacturer Approval. Policy Memorandum “Standardization and Clarification of Application of 14 CFR Part 23, §§ 23.1301 and 23.1309, Regarding Environmental Qualification”; PS-ACE100- 2005-10039, dated February 16, 2006, provides additional guidance.
Standardization and Clarification of Application of 14 CFR Part 23, §§ 23.1301 and
23.1309, Regarding Environmental Qualification
Summary
This guidance applies to FAA’s 14 Code of Federal Regulations (CFR) part 23, §§ 23.1301 and 23.1309, Amendment 23-41 or later for environmental qualification.
The guidance allows the depth of the environmental qualification to be commensurate with the severity of the hazard. It is based on the five failure condition classifications defined in AC 23.1309-1E ranging from no safety effect to catastrophic. This policy should reduce the amount of environmental qualification, especially for equipment that has no safety effect and equipment that has only minor failure conditions.
Background
For part 23 airplanes, most certification of equipment for environmental qualifications was the same for all the equipment regardless of its failure condition.
In the past, applicants and certification authorities interpreted § 23.1301(d), Function properly when installed, from Amendment 23-20, to mean that equipment, even if it was not required or pertinent to safety, should have the same environmental qualification as equipment essential to safe operation. For airplanes with certification basis including § 23.1309, Amendment 23-41 or later, the FAA is clarifying the interpretation of § 23.1301(d) to focus this activity on items either required by the regulations or having an effect on safety. This interpretation is based on the notice for Amendment 23-20 stating that the main purpose of the amendment is to prevent hazards.
The environmental qualifications will be determined by the failure conditions of the equipment, as defined in AC 23.1309-1E. Currently, software and hardware developmental assurance levels, probability of failures, and lightning and High Intensity Radiated Fields (HIRF) protection levels are determined by the failure condition classification.
Definitions
Equipment Essential to Safe Operation: Equipment installed in order to comply with the applicable certification requirements of part 23 or operational requirements of parts 91 and 135. Also, for environmental qualifications, equipment or a system that has a failure or malfunction that results in anything from minor, to major, to hazardous, to catastrophic failure conditions as defined in AC 23.1309-1E.
Hazard: Any condition that compromises the overall safety of the airplane or that significantly reduces the ability of the flight crew to cope with adverse operating conditions.
Current Airworthiness Regulations, Advisory Material of 14 CFR Part 23, and RTCA Documents or the latest version.
§ 23.1301, Function and installation
§ 23.1309, Equipment, systems, and installations
AC 23.1309-1E, System Safety Analysis and Assessment for Part 23 Airplanes
RTCA/DO-160F, Environmental Test Conditi ons and Test Procedures for Airborne Equipment or equivalent
14 CFR part 23, §§ 23.1301 and 23.1309: These sections contain the general regulatory requirements for the environmental qualifications of installed equipment.
The level of qualification depends on the five failure condition classifications, as defined in AC 23.1309-1E. These classifications are no safety effect, minor, major, hazardous, and catastrophic. TSO articles must also meet the requirements of
23.1301 and 23.1309 when installed in Part 23 aircraft.
Section 23.1301 requires that the installed equipment perform its intended function.
Section 23.1309 requires equipment to not adversely affect equipment essential to safe operation of the airplane or affect other equipment without indicating the effects to the pilot. The following paragraphs provide guidance for environmental qualification for each of the failure condition classifications:
Change 1 AC 23-17C 7/16/2012
Equipment with major, hazardous, and catastrophic failure conditions:
Applicants should design and install the equipment and systems to perform as intended under the anticipated airplane’s operating and environmental conditions that the equipment will encounter. For environmental qualification when using RTCA/DO-160F as an acceptable method of compliance, the applicant must present the appropriate sections and category levels for the airplane installation and environment to the FAA ACO. Equivalent testing methods, analyses, ground or flight tests, and qualification by similarity are also acceptable.
Following the appropriate levels of RTCA/DO-160F may be the most cost effective means for an applicant to comply, because other means of compliance may require more tests and more difficult testing. Testing for the indirect effects of lightning is also required for all of these failure conditions. For systems that have a catastrophic failure condition, testing for HIRF is required. When the proposed regulation is finalized for HIRF, testing for HIRF will also be required for all these failure conditions. For indirect effects of lightning or HIRF, additional guidance is in AC
23.1309-1E and this AC.
Equipment with minor or no safety effect failure conditions: Applicants should design and install the equipment and systems so they perform as intended under the airplane’s operating and environmental conditions that the equipment will encounter.
The applicant should install the equipment and systems in a way that does not adversely affect equipment essential to safe operation. In some cases, the FAA would only accept a ground or flight installation evaluation, or both. If the applicant is using ground or flight installation evaluation for compliance, instructions for these evaluations should consist of good engineering practices. It should include the appropriate operations modes and phases of flight. Although, the FAA would still accept qualitative evaluations for the specific airplane, it may be more efficient to address the environmental requirements by complying with the appropriate sections and levels of RTCA/DO-160. Testing for HIRF and the indirect effects of lightning is not required.
Equipment with no safety effect failure conditions: The primary purpose for environmental testing is to determine the performance characteristics of the equipment. The equipment should function when installed as intended by the manufacturer’s instructions; however, the focus should not be on the reliability of its operation for all installation environments.
Ground and flight evaluations for all equipment installations: The equipment and systems should be installed in a way that does not adversely affect equipment essential to safe operation. The evaluations should determine that neither normal operation nor failure of the equipment would pose a hazard.
Change 1 AC 23-17C 7/16/2012
171 Similarity: For any failure condition it is acceptable for all equipment to show compliance without the need for additional tests by similarity. Only slight differences may exist between the previously certified system and installation and the new system and installation. To use similarity, there must be adequate service history. If there were any problems reported, there should be an adequate history with the product with the changed design to ensure the problems were resolved. A qualitative demonstration of similarity may be acceptable. The applicant is responsible for showing there are only slight differences between the products. If uncertainty exists about the effects of the differences, either additional tests or analysis, or both, should be conducted as necessary to resolve the open issues. Similarity may not apply for a combination of a new aircraft design and a new system design including approved model list.
Conformity: The product or part must have the appropriate design data, approved procedures, and processes to determine conformity of the product or part.
Conformity should be established for all parts with major, hazardous, and catastrophic failure conditions. For parts with minor or no safety effect failure conditions, conformity is recommended. However, if there is no conformity of the parts, when the part is replaced, the new part should be tested for its performance characteristics.
For additional specific environmental qualification guidance, see AC 23.1309-1E, RTCA DO-160F, and the applicable TSO.
Change 1 AC 23-17C 7/16/2012
172 The following table summarizes the environmental qualification process for each failure condition.
Table 1. A Summary for Environmental Qualification as Related to Failure Condition Classifications
Failure Condition Classification Environmental Qualification Catastrophic Must function properly wh en installed. Does not affect other equipment essential to safe operation.
HIRF is required for all equipment.
Testing for indirect effects of lightning is required.
Normally, environmental testing using, RTCA/DO-160, or similarity.
Hazardous Must function properly when installed. Does not affect other equipment essential to safe operation.
Testing for the indirect effects of lightning is required.
Normally, environmental testing using RTCA/DO-160, or similarity.
Major Must function properly when installed. Does not affect other equipment essential to safe operation.
Testing for the indirect effects of lightning is required.
Normally, environmental testing using RTCA/DO-160, or similarity.
Minor Must function properly when installed. Does not affect other equipment essential to safe operation.
It may comply by ground or flight evaluation, or both, or similarity. If several airplane models are involved, it may be more efficient to use RTCA/DO-160.
No safety effects Must function properly when installed. Does not affect other equipment essential to safe operation.
It may comply by ground or flight evaluation, or both, or similarity. If several airplane models are involved, it may be more efficient to use RTCA/DO-160.
Change 1 AC 23-17C 7/16/2012
173 Applicants should expect certificating officials to consider this information when making findings of compliance relevant to new certificate actions. Also, as with all advisory material, this policy statement identifies one means, but not the only means, of compliance.
Amendment 23-7
A proposed revision in NPRM 67-14 explains this change as follows: “This proposal would remove the unnecessary distinction between radio and other equipment that now exists in Sec. 23.1301 (a) (2) and (3), and extend the provisions of Sec. 23.1431 to all equipment, not only radio equipment. There is no basis for distinguishing between radio and other equipment so far as general functioning requirements are concerned. The other changes are intended to bring the sections in closer conformity with the corresponding sections in Part 25 through 29, without substantive change.”
Original Issue through Amendment 23-19
A system/equipment that is neither essential for safe operation nor required by airworthiness or operating rules may be approved if it is not a hazard in normal operation or when it malfunctions/fails. It does not have to perform its intended function.
Section 23.1301 requires that instruments be installed under prescribed limitations.
Therefore, if an instrument manufacturer specifies any allowable installation requirements (that is, panel slope for gyroscopic instruments); the installer should stay within the limitation(s).
Each piece of installed equipment must be either labeled about its identification, function, operating limitations, or any combination. This applies to the manufacturer of the equipment not the installer. The installer is required to verify the intended function and make any placards or flight manual limitations for the installed equipment per Subpart G as necessary.
See ACs 23-8C, “Flight Test Guide for Certification of Part 23 Airplanes; and 20- 41A, “Substitute Technical Standard Order (TSO) Aircraft Equipment.”
Amendment 23-20 and Subsequent All installed systems/equipment should perform their intended functions. For systems/equipment neither essential for safe operation nor required by airworthiness or operating rules, the manufacturer should define the intended functions the FAA will verify as part of the certification project.
Section 23.1301 requires that instruments be installed under prescribed limitations.
Therefore, if an instrument manufacturer specifies any allowable installation
174 requirements (that is, panel slope for gyroscopic instruments); the installer should stay within the limitation. FAA recommends the slope be no more than 15 degrees.
Change 1 AC 23-17C 7/16/2012
175 If applicants want a slope greater than 15 degrees, they should show decisively by tests or analyses the instrument will function properly when subjected to all expected airplane maneuvers.
Each piece of installed equipment must be either labeled about its identification, function, operating limitations, or any combination. This applies to the manufacturer of the equipment not the installer. The installer is required to verify the intended function and make any placards or flight manual limitations for the installed equipment per Subpart G as necessary. There has been a trend for applicants to install equipment, mainly navigation related such as moving maps, labeled as nonrequired, “Not approved for primary navigation” or “Situation Awareness Only (SA- Only).”
Intended Function and Associated Flightcrew Tasks:
(1) In order to show compliance with § 23.1301, the intended function of a system and the tasks expected of the flightcrew must be known.
(2) An applicant’s statement of intended function must be sufficiently specific and detailed that the FAA can evaluate whether the system is appropriate for the intended function(s) and the associated flight crew tasks. For example, a statement that a new display system is intended to “enhance situation awareness” must be further explained. A wide variety of different displays enhance situation awareness in different ways. Examples are terrain awareness displays, vertical profile, and even the primary flight displays. The applicant may need more detailed descriptions for designs with greater levels of novelty, complexity or integration.
(3) An applicant should describe intended function(s) and associated task(s) for:
(a) Each item of flight deck equipment.
(b) Flightcrew indications and controls for that equipment.
(c) Individual features or functions of that equipment.
This type of information is of the level typically provided in a pilot handbook or an operations manual. It would describe indications, controls, and flightcrew procedures.
Novel features may require more detail, while previously approved systems and features typically require less. Some are sufficiently novel that additional scrutiny is required. Applicants may evaluate whether statements of intended function(s) and associated task(s) are sufficiently specific and detailed by using the following questions:
1. Does each feature and functionality have a stated intended function?
2. Are flightcrew tasks associated with the function described?
3. What assessments, decisions, and actions , are flight crewmembers expected to accomplish based on information provided by the system? 4. What other information is assumed to be used in combination with the system?
5. Will installation or use of the system interfere with ability of the flightcrew to operate other flight deck systems?
6. Are there any assumptions made about the operational environment in which the equipment will be used?
7. What assumptions are made about flight crew attributes or abilities beyond those required in regulations governing flight operations, training, or qualification?
Amendment 23-62 and Subsequent
In Docket No. FAA-2009-0738, the Discussion of the Regulatory Amendments stated: The Aviation Rulemaking Committee (ARC) did not make specific recommendations regarding § 23.1301. However, the FAA seeks to clarify the intent of this section, which is frequently misinterpreted and misapplied. Clarifying the intent of § 23.1301 would improve standardization for systems and equipment certification, particularly for non-required equipment and non-essential functions embedded within complex avionic systems. The intent is for the applicant to define proper functionality and to propose a means of compliance acceptable to the Administrator. The FAA expects applicants to coordinate or negotiate deviations from established means of compliance with the Administrator as early as possible to minimize delay to program schedules.
The FAA deleted subparagraph § 23.1301(d) which currently states that equipment must “function properly when installed.” The revision limits the scope since it applies only to equipment required for type certification or the operation. FAA made a related change to clarify similar language in § 23.1309 for proper functionality of installed equipment.
The Final Rule addressed the concerns on § 23.1301(d) by revising § 23.1309(a) and added § 23.1309(a)(3). Further explanation of § 23.1309(a)(3) appears later with §§ 23.1309(a)(1) and (a)(2). Section 23.1301 is adopted as proposed.
Accuracy of the Magnetic Gyroscopically Stabilized Heading System
PURPOSE.
The purpose of this guidance is to provide information on accuracy of the magnetic gyroscopically stabilized heading system that can be displayed on a Horizontal Situation Indicator (HSI) installed in part 23 airplanes.