g. Verify System ETDLs Using System Qualification Tests.
(1) Identify the equipment, components, sensors, power systems, and wiring associated with the Level A system undergoing ETDL verification tests, specifically considering the system functions whose failures have catastrophic failure consequences. For complex Level A systems, the system configuration may include redundant equipment, multiple power sources, multiple sensors and actuators, and complex wire bundles. Define the system configuration that will be used for the ETDL verification tests. The cognizant ACO must approve your system configuration for ETDL verification tests.
(2) Verify the ETDLs using single stroke, multiple stroke, and multiple burst tests on the system wire bundles. Use waveform sets and test levels for the defined ETDLs. Show that the system operates within the defined pass/fail criteria during these tests. No equipment damage should occur during these system tests or during single stroke pin injection tests using the defined ETDLs. RTCA/DO-160E, Section 22 provides acceptable test procedures and waveform set definitions. In addition, SAE ARP 5416 provides acceptable test methods for complex and integrated systems.
(3) Evaluate any system effects observed during the qualification tests to ensure these do not adversely affect the system’s continued performance. The cognizant ACO must approve your evaluation.
h. Verify System ETDLs Using Existing System Data (Similarity).
(1) You may base your ETDL verification on similarity to previously certified systems without performing more tests. You may do this when there are:
• Only minor differences between the previously certified system and installation, and the system and installation to be certified;
• There are no unresolved in-service system problems related to lightning strikes on the previously certified system; and
• The previously certified system ETDLs were verified by qualification tests.
(2) To use similarity, you must assess differences between the previously certified system and installation and the system and installation to be certified that can adversely affect the system susceptibility. The assessment should cover:
• System interface circuits;
• Wire size, routing, arrangement (whether parallel or twisted wires), connector types, wire shields, and shield terminations;
• Lightning protection devices such as transient suppressors and lightning arrestors;
• Grounding and bonding; and
• System software, firmware, and hardware.
(3) If you are unsure how the differences will affect the systems and installations, you must perform more tests and analyses to resolve the open issues.
(4) You must assess every system, even if it uses equipment and installation techniques that have previous certification approval.
(5) You cannot use similarity for a new aircraft design with new systems.
i. Verify Compliance. You must compare the verified system ETDLs with the aircraft ATLs and determine if acceptable margin exists between the ETDLs and ATLs. Margins account for uncertainty in the verification method. As confidence in the verification method increases, the margin can decrease. An ETDL that exceeds the ATL by a factor of two is an acceptable margin for Level A systems, if this margin is verified by aircraft test or by analysis supported by aircraft tests. For other verification methods, the margin should be agreed upon with the cognizant ACO.
j. Corrective Measures.
(1) When your system fails to meet the certification requirements, you must decide on corrective actions. The changes or modifications you make to the aircraft, system installation or the equipment may require more testing and analysis.
(2) To meet the certification requirements, you may need to repeat equipment qualification testing, or aircraft testing and analysis (in whole or in part). You also may need to modify the equipment or installation to get certification. When significant changes are necessary, update your lightning certification plan accordingly. The updated certification plan should be resubmitted to the cognizant ACO for review.
7. LEVEL B AND C SYSTEM LIGHTNING CERTIFICATION.
a. Identify Level B and C Systems.
(1) Identify your Level B and C systems as described in paragraph 4a.
(2) Define the detailed system performance pass/fail criteria. You should get ACO concurrence on this criteria before you start testing or analyzing your Level B and C systems.
(3) Figure 6 below illustrates a process you can use to show that your Level B and C systems comply with 14 CFR requirements.
Figure 6. Typical Compliance Process for Level B and C Systems
Identify Level B and C Systems
(7.a) Define System ETDLs
(7.b) ETDL Verification Method?
System ETDLs Verified by Qualification Tests
(7.c) System ETDLs Verified by Similarity
(7.d) ETDL Verification Acceptable?
(7.e) Lightning Compliance Demonstrated Yes Modify System Protection
(7.f) No Define System Lightning Protection Features (4.e) Numbers in parenthesis refer to the paragraphs in this AC
b. Establish ETDLs.
(1) You may use the ATLs determined during aircraft tests or analyses performed for Level A systems to establish appropriate ETDLs for Level B and C systems.
(2) Alternatively, you may use the definitions in RTCA/DO-160E, Section 22 to select appropriate ETDLS for your Level B and C systems. The following should be considered when selecting an appropriate level:
• Use RTCA/DO-160E, Section 22 Level 3 for most Level B systems.
• For Level B systems and associated wiring installed in aircraft areas with more severe lightning transients, use RTCA/DO-160E, Section 22 Level 4 or 5 as appropriate to the environment. Examples of aircraft areas with more severe lightning transients are those external to the fuselage, areas with composite structures showing poor shielding effectiveness, and other open areas.
• Use RTCA/DO-160E, Section 22 Level 2 for most Level C systems.
• For Level C systems installed in aircraft areas with more severe lightning transients, use RTCA/DO-160E, Section 22 Level 3. Examples of aircraft areas with more severe lightning transients are those external to the fuselage, areas with composite structures showing poor shielding effectiveness, and other open areas.
• You must provide the cognizant ACO with a description of your aircraft and system installation features to substantiate the RTCA/DO-160E, Section 22 levels selected for your system.
c. Verify System ETDLs Using Equipment Qualification Tests.
(1) Verify the ETDLs using single stroke, multiple stroke, and multiple burst tests on the equipment wire bundles. Use waveform sets and test levels for the defined ETDLs. Show that the equipment operates within the defined pass/fail criteria during these tests. No equipment damage should occur during these system tests or during single stroke pin injection tests using the defined ETDLs. RTCA/DO-160E, Section 22 provides acceptable test procedures and waveform set definitions.
(2) Evaluate any equipment effects observed during the qualification tests to ensure these do not adversely affect the system’s continued performance. The cognizant aircraft certification office must approve your evaluation.
(3) Multiple stroke and multiple burst testing is not required if an analysis shows that the equipment is not susceptible to upset or, the equipment may be susceptible to upset, but a reset capability exists that will recover the function in a timely manner.
d. Verify System ETDLs Using Existing Equipment Data (Similarity).
(1) You may verify ETDLs by similarity to previously certified systems without performing more tests. You may do this when there are:
• Only minor differences between the previously certified system and installation, and the system and installation to be certified;
• There are no unresolved in-service system problems related to lightning strikes on the previously certified system; and
• The previously certified system ETDLs were verified by qualification tests.
(2) To use similarity, you must assess differences between the previously certified system and installation and the system and installation to be certified that can adversely affect the system susceptibility. The assessment should cover:
• Equipment interface circuits;
• Wire size, routing, arrangement (whether parallel or twisted wires), connector types, wire shields, and shield terminations;
• Lightning protection devices such as transient suppressors and lightning arrestors;
• Grounding and bonding; and
• Equipment software, firmware, and hardware.
(3) If you are unsure how the differences will affect the systems and installations, you must perform more tests and analyses to resolve the open issues.
(4) You must assess every system, even if it uses equipment and installation techniques that have previous certification approval.
e. Verify Compliance. You must show that the Level B and C systems meet their defined acceptance criteria during the qualification tests at the selected system ETDLs.
f. Take Corrective Measures. When your system fails to meet the certification requirements, you must decide on corrective actions. If you change or modify the system or installation, you may need to repeat equipment qualification testing. When significant changes are necessary, update your lightning certification plan accordingly. The updated certification plan should be resubmitted to the cognizant ACO for review.
8. MAINTENANCE AND SURVEILLANCE.
a. In the Instructions for Continued Airworthiness (ICA) (for example, 14 CFR § 25.1529), you must identify the minimum maintenance required to support certification. Some systems or equipment in an installation require dedicated protection devices, or specific techniques to protect them. You should define the requirements for periodic and conditional maintenance and surveillance of these devices or techniques, to ensure acceptable protection performance while the system or equipment is in service. Avoid using – or identify when to inspect or replace – Page 18
devices that may degrade with time because of corrosion, fretting, flexing cycles, or other causes.
b. You should define the inspection techniques and intervals needed to ensure that the aircraft and system lightning protection remains effective in service. Also, identify built-in test equipment, resistance measurements, continuity checks of the entire system, or other means to determine your system’s integrity periodically and conditionally.
c. See SAE ARP 5415 for more information on aircraft lightning protection maintenance and surveillance.
Susan J. M. Cabler Acting Manager, Aircraft Engineering Division Page 19
Appendix 1 APPENDIX 1. RELATED DOCUMENTS AND HOW TO GET THEM
1. Title 14 of the Code of Federal Regulations (14 CFR). You can get copies of the following 14 CFR sections from the Superintendent of Documents, Government Printing Office, Washington, D.C. 20402-9325. Telephone 202-512-1800, fax 202-512-2250. You can also get copies from the Government Printing Office (GPO), electronic CFR Internet website at www.access.gpo.gov/ecfr/.
a. Part 23, Airworthiness Standards: Normal, Utility, Acrobatic, and Commuter Category Airplanes:
§ 23.901 Power plant; installation § 23.1301 Function and installation § 23.1309 Equipment, systems, and installations § 23.1529 Instructions for continued airworthiness
b. Part 25, Airworthiness Standards: Transport Category Airplanes:
§ 25.901 Power plant; installation § 25.1301 Function and installation § 25.1309 Equipment, systems, and installations § 25.1316 System lightning protection § 25.1529 Instructions for continued airworthiness
c. Part 27, Airworthiness Standards: Normal Category Rotorcraft:
§ 27.901 Power plant; installation § 27.1301 Function and installation § 27.1309 Equipment, systems, and installations § 27.1529 Instructions for continued airworthiness
d. Part 29, Airworthiness Standards: Transport Category Rotorcraft:
§ 29.901 Power plant; installation § 29.1301 Function and installation § 29.1309 Equipment, systems, and installations § 29.1529 Instructions for continued airworthiness
e. Part 33, Airworthiness Standards: Aircraft Engines:
§ 33.28 Electrical and electronic engine control systems § 33.53 Engine component tests (Reciprocating aircraft engines) § 33.91 Engine component tests (Turbine aircraft engines)
2. FAA Advisory Circulars (AC). You can get copies of the following ACs from the U.S.
Department of Transportation, Subsequent Distribution Office, M-30, Ardmore East Business Center, 3341 Q 75th Avenue, Landover, MD 20795. Telephone 301-322-5377, Page A1-1
Appendix 1 APPENDIX 1. RELATED DOCUMENTS AND HOW TO GET THEM (CONTINUED) fax 301-386-5394. You can also get copies from our Regulatory and Guidance library (RGL) at http://rgl.faa.gov. On the RGL website, select “Advisory Circulars,” then select “By Number.”
a. AC 20-155, SAE Documents to Support Aircraft Lightning Protection Certification.
b. AC 21-16, Radio Technical Commission for Aeronautics Document DO-160E.
c. AC 23.1309-1, System and Equipment Installations in Part 23 Airplanes.
d. AC 25.1309-1, System Design and Analysis.
e. AC 27-1, Certification of Normal Category Rotorcraft.
f. AC 29-2, Certification of Transport Category Rotorcraft.
3. Industry Documents.
a. European Organization for Civil Aviation Equipment (EUROCAE) Documents.
You can get copies of the following documents from EUROCAE, 17 rue Hamelin, 75116 Paris, France. Telephone 33 (0) 1 4505 7188, fax 33 (0) 1 4505 7230, website www.eurocae.org.
(1) EUROCAE ED-14E, Environmental Conditions and Test Procedures for Airborne Equipment, dated March 2005.
(2) EUROCAE ED-105, Aircraft Lightning Test Methods, dated April 2005.
b. RTCA Document. You can get copies of RTCA/DO-160E, Environmental Conditions and Test Procedures for Airborne Equipment, dated December 9, 2004, from RTCA, Inc., 1828 L Street, NW, Suite 805, Washington, DC 20036. Telephone 202-833-9339, fax 202-833-9434, website www.rtca.org. This document is technically equivalent to EUROCAE ED-14.
Anywhere there is a reference to RTCA/DO-160, EUROCAE ED-14 may be used.
c. Society of Automotive Engineers (SAE) Documents. You can get copies of the following documents from SAE World Headquarters, 400 Commonwealth Drive, Warrendale, PA 15096-0001. Telephone 724-776-4970, fax 724-776-0790, website www.sae.org.
(1) Aerospace Recommended Practice (ARP) 4754, Certification Considerations for Highly Integrated or Complex Aircraft Systems, dated November 1996.
(2) ARP 4761, Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment, December 1996
(3) ARP 5415A, User’s Manual for Certification of Aircraft Electrical/Electronic Systems Against the Indirect Effects of Lightning, May 2002.
Page A1-2
Appendix 1 APPENDIX 1. RELATED DOCUMENTS AND HOW TO GET THEM (CONTINUED)
(4) ARP 5416, Aircraft Lightning Test Methods, March 2005. This document is technically equivalent to EUROCAE ED-105. Anywhere there is a reference to ARP 5416, EUROCAE ED-105 may be used.
Page A1-3 (and A1-4)