Understanding the Role of RTCA DO-160 in the Avionics Certification Process

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1 Donald L Sweeney D.L.S. Electronic Systems, Inc & D.L.S. Conformity Assessment, Inc. Copyright D.L.S. Electronic Systems, Inc 2013, 2014 and 2015 Understanding the Role of RTCA DO-160 in the Avionics Certification Process DISCLAIMER INTRODUCTION About RTCA Background of DO-160 Why use DO 160? Reason for Testing Test Procedure Needed User Guides Sequencing Shared information TABLE OF CONTENTS FROM DO-160G SECTIONS 1-26 Discussed with Comments & Observations of each section CONCLUSION DISCLAIMER Please understand that this chapter is not to be considered a complete collection of DO-160 requirements. You are expected to have a copy of the required version of the RTCA DO-160 Standard for your product to determine the testing required as well as the specific test procedure to be performed. The present version of the D0-160 Standard is more than 300 pages. This chapter is just a small portion of the standard and is taken out of context. The material presented here has been collected by the authors from many sources that are believed to be reliable. However, no expressed or implied warranty can be made as to the accuracy or completeness of the material. No responsibility or liability is assumed by D.L.S. Electronic Systems, Inc., D.L.S. Conformity Assessment, Inc., their employees or the authors of these papers for any conclusions derived from these materials, and their 1

2 presentations here or any designs executed using the information contained in these notes, as a basis. The final determination of the suitability of any information for the use contemplated for a given application remains the sole responsibility of the user. Copies of DO-160 may be obtained from: RTCA, Inc L Street, NW, Suite 805 Washington, DC , USA Telephone: Facsimile: Internet: Please call RTCA for price and ordering information. Bold type has been added throughout this chapter to point out important information which needs to be considered as you proceed. Bold is also used to indicate headings to improve reading. All tables mentioned in this chapter are found in the RTCA DO-160 Standard. Also you will notice many sub-sections of the standard are purposely not included in this chapter. INTRODUCTION About RTCA RTCA, Incorporated is a not-for-profit corporation formed to advance the art and science of aviation and aviation electronic systems for the benefit of the public. The organization functions as a Federal Advisory Committee and develops consensus-based recommendations on contemporary aviation issues. RTCA objectives include but are not limited to: Coalescing (bringing together) aviation system users and providers of technical requirements in a manner that helps government and industry meet their mutual objectives and responsibilities Analyzing and recommending solutions to the system technical issues that aviation faces as it continues to pursue increased safety, system capacity and efficiency Developing consensus on the application of pertinent technology to fulfill user and provider requirements, including development of minimum operational performance standards for electronic systems and equipment that support aviation Assisting in developing the appropriate technical material upon which positions for the International Civil Aviation Organization and the International Telecommunications Union and other appropriate international organizations can be based. The organization s recommendations are often used as the basis for government and private sector decisions as well as the foundation for many Federal Aviation Administration Technical Standard Orders. Since RTCA is not an official agency of the United States Government, its recommendations may not be regarded as statements of official government policy unless so enunciated by the U.S. government organization or agency having statutory jurisdiction over any matters to which the recommendations relate. DO-160 standards are coordinated by RTCA SC-135 with the European Organisation for Civil Aviation Equipment (EUROCAE). EUROCAE concurs with RTCA on the environmental conditions and test procedures set forth herein. When approved by EUROCAE, the document will be identified jointly as RTCA DO-160G/EUROCAE ED-14G. 2

3 Background of DO-160 RTCA DO-160 G Environmental Conditions and Test Procedure for Airborne Equipment was prepared by Special Committee 135 (SC -135) and approved by the RTCA Program Management Committee (PMC) on December 8, It supersedes RTCA DO-160F dated December 6, Please note that there are many versions of DO-160 that are regularly used. It is imperative that you order and use the version required for your particular application. In 2013, testing is rarely done to version D, while E, F and G are regularly used. G is the most recent version and will most likely be used for new systems. You can find the latest version of DO-160 that is currently in effect at along with alerts of anticipated changes and possible errata to the standard and this write up. Why would you not test to the latest version of DO-160? If a plane was certified to an earlier version then you might be required to test to the older version. There are, in some cases, significant changes from one version to another; therefore, testing to the latest version might not meet the intended requirements for the product. Why use DO 160? RTCA DO-160 Environmental testing is required for various components used in an Avionic System to determine their ability to perform as specified by the product s specification defined by the purchaser, manufacturer or governmental agency, such as the FAA. Performance will be of two types: 1) The device must not interfere with other equipment near it, such as Radio Frequency Emission Energy, Section 21. 2) The device must operate as intended when acted upon by environmental effects from nearby equipment, such as Radio Frequency Susceptibility (Radiated and Conducted), Section 20; Shock and Vibration, Sections 7 and 8; Sand and Dust, Section 12; and even the shock and the effects of being involved in a plane crash, Section 7. As you read through this chapter and the DO-160 Standard, you will see how real life environmental effects are used to develop the requirements. The entire goal of these requirements is to make the completed aircraft as safe as is reasonably possible. Reason for Testing Each required test has a specific purpose. DO-160 defines a series of minimum standard environmental test conditions (categories) and applicable test procedures for airborne equipment. The purpose of these tests is to provide a laboratory the means of determining the performance characteristics of airborne equipment in environmental conditions which may be encountered. The standard environmental test conditions and test procedures contained herein may be used in conjunction with applicable equipment performance standards as a minimum specification under environmental conditions, which can ensure a sufficient degree of confidence in performance during operations. Test Procedure Needed In preparation for performing the tests, a Test Procedure should be generated and it should be agreed upon by all parties involved, from the manufacturer/designer to the FAA or the agency granting final approval of the airworthiness of the components or final assembly. If one waits until the final submittal before having the tests approved, there will very likely be discussions which could require that some or all of the testing be performed over. Any retesting will add cost, and even worse, delay the overall project. 3

4 User Guides You will find User Guides at the end of various sections within DO-160. They provide background information for the associated test procedures and requirements described in the main body of that section. This information includes rationale for requirements, guidance in applying the requirements, commentary, possible troubleshooting techniques and lessons learned from previous laboratory experience. (See Section 1.2 for more information). An example of a User s Guide is shown in Section 9 of this chapter. The User s Guides follow a parallel format to the main body of that section for easy cross reference. Paragraph numbers correspond to each paragraph in the section and in the User s Guide. Sequencing Often it is very important to consider the sequence of the test. Sequencing may require one test to be performed before another in order not to interfere or bias the results of the next test with residual effects from a previous test. (See Section 3.2 for more details on Sequencing.) Shared information There are parts of the DO-160 Standard that are stated in one section yet could relate to many or all sections. For example, many sections comment that information contained in this section is pertinent to all test procedures described in the other sections of this document. However this information may not be stated in the other sections. For example, Appendix A identifies environmental tests that may need to be performed in other sections. TABLE OF CONTENTS FROM DO-160G The following table of contents is taken from the latest standard. In the body of this chapter, different names are used for some of the sections. That is the way the standard is written. Foreword...i Table of Contents... iii Section 1.0 Purpose and Applicability Section 2.0 Definitions of Terms - General Section 3.0 Conditions of Tests Section 4.0 Temperature and Altitude Section 5.0 Temperature Variation Section 6.0 Humidity Section 7.0 Operational Shocks and Crash Safety Section 8.0 Vibration Section 9.0 Explosion Proofness Section 10.0 Water Proofness Section 11.0 Fluids Susceptibility Section 12.0 Sand and Dust Section 13.0 Fungus Resistance Section 14.0 Salt Spray Section 15.0 Magnetic Effect Section 16.0 Power Input Section 17.0 Voltage Spike Section 18.0 Audio Frequency Conducted Susceptibility - Power Inputs Section 19.0 Induced Signal Susceptibility Section 20.0 Radio Frequency Susceptibility (Radiated and Conducted) Section 21.0 Emission of Radio Frequency Energy Section 22.0 Lightning Induced Transient Susceptibility 4

5 Section 23.0 Section 24.0 Section 25.0 Section 26.0 Appendix A Lightning Direct Effects Icing Electrostatic Discharge Fire, Flammability Environmental Test Identification Note: A detailed table of contents appears on the inside of most sections. The following is a review of each section of DO-160 and is intended as an introduction and overview of the standard, not a substitute for having a copy of the official standard. SECTION 1 - PURPOSE AND APPLICABILITY The document defines a series of minimum standard environmental test conditions (categories) and applicable test procedures for airborne equipment. The purpose of these tests is to provide a laboratory means of determining the performance characteristics of airborne equipment in environmental conditions representative of those, which may be encountered in airborne operation of the equipment. The standard environmental test conditions and test procedures contained in DO-160 may be used in conjunction with applicable equipment performance standards as a minimum specification under environmental conditions, which can ensure a sufficient degree of confidence in performance during operations. Note: In each of the test procedures contained in DO-160, the following phrase will be seen several times: DETERMINE COMPLIANCE WITH APPLICABLE EQUIPMENT PERFORMANCE STANDARDS. The applicable equipment performance standards referred to are either: a. EUROCAE Minimum Operational Performance Specifications (formerly Requirements) (MOPS/MOPR). b. RTCA Minimum Performance Standards (MPS) and/or RTCA Minimum Operational Performance Standards (MOPS). c. The manufacturer s equipment specification(s), where applicable. Some of the environmental conditions and test procedures contained in DO-160 are not necessarily applicable to all airborne equipment. The selection of the appropriate and/or additional environmental conditions and test procedures is the responsibility of the writers (authors) of the performance standards for the specific airborne equipment. Notes: a. There are several additional environmental conditions (categories) that specific airborne equipment may need to be evaluated against that have not been included in DO-160. These include, but are not limited to: hail, acceleration and acoustic vibration. b. The procedures for testing airborne equipment for special environmental conditions that are uniquely related to that specific type of airborne equipment should be the responsibility of the writer (author) of the performance standard for that specific equipment. c. The International System of Units is usually used throughout the document as the primary value. In certain instances, however, when the primary values were derived in U.S. units, the U.S. units are used as the primary values. d. Subject to the provisions of Subsection 3.2, it is permissible to use more than one test article. 5

6 The words airborne equipment, as used within in DO-160, has direct applicability to most airborne equipment. It is the responsibility of those who wish to apply the test conditions and procedures contained in DO-160 to determine the applicability of these test conditions and procedures to a specific equipment intended for installation on, or within, a specific or general class or type of aircraft. a. You will need to read each section of DO-160 and base your decisions on who is buying the device and what their specification calls out. b. Will the device require final FAA approval? c. Generally, a test procedure should be written and approved before beginning the testing. d. Where will it be installed on and/or in the aircraft? Will it be internal or external to the aircraft? If internal, will it be in the cockpit, avionic bay or main cabin? e. These will help you determine the category of testing required. f. The aircraft manufacturer has the right to massage, manipulate or add to the standard. a. Since there are many versions of DO-160; using the latest version is not necessarily acceptable. For example, if the device you are testing is a retro fit, you may be required to use the older version of DO-160 to which the system was originally certified. b. The older version may not be compatible with the most recent version, nor the most recent version compatible with the older versions. Minimum operational performance standards (MOPS) prepared by RTCA, Inc. for airborne equipment contain requirements that the equipment must meet to ensure reliable operation in actual aeronautical installations. These equipment requirements must be verified in ambient and stressed environmental conditions. The MOPS typically contain recommended bench test procedures for ambient conditions, and refer to RTCA Document DO-160, Environmental Conditions and Test Procedures for Airborne Equipment for the stressed environmental testing. The test categories defined in DO-160 are intended to encompass the full spectrum of environmental conditions that airborne equipment may experience from benign to very hostile. The environmental conditions and test procedures defined in DO-160 are intended to determine only the performance of the airborne equipment under the stated environmental conditions and are not intended to be used as a measure of service life of the airborne equipment subjected to these tests. Any regulatory application of DO-160 is the sole responsibility of appropriate governmental (regulatory) agencies. 1.1 Historical Note and General Guidance to Users DO-160 (or its precursor, DO-138) has been used as a standard for environmental qualification testing since It has been referenced in Minimum Operational Performance Specifications (MOPS) for specific equipment designs, and is referenced in FAA Advisory Circulars as a means of environmental qualifications for Technical Standard Order (TSO) authorization. It has been subjected to a continuous process of upgrade and revision as new needs arise within the aviation community, as improved test techniques have emerged, and as the realities of equipment operation under actual environmental conditions has become better understood. Environmental stresses can result from natural forces or manmade effects and may be mitigated by details of the equipment installation. The categories that have been developed over time reflect a reasonably mature understanding as to the severity of the stresses, the degrees of mitigation 6

7 achievable in the design of an installation, and the robustness that must be designed into equipment in order to perform under the resultant stress. In order to fully reap the advantages of the maturity of this document, it is incumbent upon the designers of the installed equipment, as well as the designers of the host installation, to consider the categories defined herein as early in their programs as feasible. The categories defined within each environmental test procedure have proved to be a practical set of boundary conditions between the requirements of real world installations and the performance of installed equipment. Effective dialogue between the airframe and equipment designers is essential to ensure that correct categories are utilized. 1.2 DO-160 User Guides Various sections within DO-160 now contain User Guide material. This material appears at the end of the respective section. The User Guides provide background information for the associated test procedures and requirements in the main body of DO-160. This information includes rationale for requirements, guidance in applying the requirements, commentary, possible troubleshooting techniques and lessons learned from previous laboratory experience. This information is intended to help users understand the intent behind the requirements, and to help users develop detailed test procedures based on the general test procedures in this document. These User Guides are provided for guidance purposes. The User Guides do not contain requirements. Only the procedures in the body of each section are required to be applied to the EUT. The User Guides follow the same general format as the main body of the section. Main body paragraph numbers are repeated in the User Guide. SECTION - 2 DEFINITION OF TERMS, GENERAL This section contains the definitions of general terms that are utilized throughout this document. The definition of terms specific to a particular section may be found in the appropriate section. a. You will always want to use the DO-160 definition of terms. a. Individual sections might have their own definition of terms. 2.1 Equipment Temperature Stabilization a. Not Operating The equipment is considered temperature stabilized when the temperature of the functioning parts of the test item considered to have the longest thermal lag are within three degrees Celsius of the specified test temperature. b. Operating The equipment is considered temperature stabilized when the functioning parts of the test item considered to have the longest thermal lag do not vary by more than two degrees Celsius per hour. When temperature measurement of the largest internal mass is not practical, the minimum time considered applicable for temperature stabilization shall be two hours. 2.2 Maximum Duty Cycle When operation of equipment is periodic, the maximum duty cycle is the relationship between the maximum length of time for which the equipment is designed to operate at its rated capacity and the length of time during which the equipment is not operating; or when the operating capacity is at a defined minimum. The maximum duty cycle shall be established by the equipment specification. 7

8 2.3 Not Operating Not operating is that condition wherein no power is applied to the equipment unless otherwise defined in the individual equipment specification. 2.4 Controlled or Partially Controlled Temperature Locations A controlled or partially controlled temperature location is a space within an aircraft in which the temperature of the air is maintained by an environmental control system (see Table 4-1 of applicable category). 2.5 Total Excursion Total excursion means the total displacement from positive maximum to negative maximum. 2.6 Equipment The term equipment includes the test items and all of the components or units necessary (as determined by the equipment manufacturer) for the equipment to properly perform its intended function(s). The equipment shall be representative of the production standard that will be utilized in service. 2.7 Altitude Altitude represents the environmental pressure relative to sea level to which the equipment is exposed during the tests. 2.8 Category of Tests and Declarations For each environmental condition addressed in this document, the equipment supplier should select, from categories defined within the particular sections, a category which best represents the most severe environment to which the equipment is expected to be regularly exposed during its service life. An exception to this rule is the use of Category X as explained below. The selected categories are to be tabulated on the Environmental Qualification Form in accordance with the guidelines presented in Appendix A, which can be found at the end of the standard. For any category listed on the Environmental Qualification Form, it can be derived that the equipment would also be able to perform its intended function(s) when exposed to categories that can be assessed as being less severe. Use of Category X on the environmental qualification form in association with any environmental test procedure of DO-160 is reserved for the case where the equipment supplier wishes to indicate that compliance with equipment performance standards has not been demonstrated under the environmental conditions addressed by that particular procedure. If any category listed on the Environmental Qualification Form is not sufficient for a specific aircraft certification, then additional testing may be required. When the statement DETERMINE COMPLIANCE WITH APPLICABLE EQUIPMENT PERFORMANCE STANDARDS is found at the end of or during the test procedures, it should be understood that performance compliance and verification is considered to be the requirement that allows the equipment to be certified as to its ability to perform its intended function(s) during and/or after a specific test category. 2.9 Applicability of Test Results The results of the testing using these procedures are only valid for the test configuration (test set up, external configuration and internal configuration) used during the qualification tests. Any change from this configuration, either externally or internally (such as: PCB lay-out, component change inside the unit, installation wiring, etc.) must be assessed to ensure that the test results are still applicable. If an assessment cannot show that the results are still applicable, re-testing is required. 8

9 SECTION 3 CONDITIONS OF TESTS 3.1 Connection and Orientation of Equipment Unless otherwise stated, connect and orient the equipment (e.g. mechanically and electrically) as recommended by the equipment manufacturer for normal service installation, including any cooling provisions (see Photo 1). Where not specified, power leads shall be 1.0M ±10cm and interconnecting cables shall be at least 3.3M. Any inputs or outputs to or from other equipment normally associated with the equipment under test shall be connected or adequately simulated. Note: Paragraphs 19.3 and 20.3, if applicable, will require an interconnecting cable longer than these minimums (see Photo 2). a. This is an introduction to how the equipment might be configured during the test. b. Sometimes the order of the testing must be considered. For example when should salt spray testing be done? This will be referred to as sequencing in this chapter or sequence in the standard. c. Sequencing: Save destructive tests for last. d. Generally start with radiated emissions then conducted emissions. Problems found here when mitigated will make other tests more likely to pass. e. Additional lengths may be required in some sections. f. If installation is known, use the actual cable lengths for testing. Cooling provisions during testing (Photo 1) Complete wiring harness from an aircraft (Photo 2) g. In general you will want to set up the testing for the worst case cable length to avoid resetting the system multiple times. h. Safety of Flight: Minimum tests you have to pass before the aircraft can fly test flights. i. Companies have the right to require the test procedures be followed in the order they wish except where dictated by the standard, e.g. fungus test must be before Salt Spray and Sand and Dust. j. You are expected to test the worst case. k. If products will be sold both with and without shielded cables, the unshielded cable must be tested. You may want to test both cases as it is possible that the shielded cable might be the worst case. l. The test setup is aircraft specific in some cases, such as direct lightning. a. If testing is allowed on multiple units, then the order of the test might not be important. 3.2 Order of Tests (Sequence), Multiple Test Articles It is the responsibility of the equipment manufacturer to determine any requirements for cumulative or combined testing, and to reflect these requirements in the Equipment Specification and Test Procedure. Insofar as any such requirements are not compromised, multiple test articles may be used, 9

10 tests may be performed in any order, and separate test articles may be used for demonstrating compliance with the separate tests. Note: In cases where cumulative testing is required, or multiple tests are to be performed upon a single test article, the following provisions shall apply: a. The salt fog test shall not be conducted prior to the fungus resistance test. b. The sand and dust test shall not be conducted prior to the fungus resistance, salt fog, or humidity tests. c. The explosive atmosphere tests shall not be conducted prior to any other DO-160 tests. d. The flammability tests shall not be conducted prior to any other DO-160 tests. 3.3 Combining Tests It is acceptable to employ alternate procedures developed as combinations of the procedures described herein, provided it can be demonstrated that all applicable environmental conditions specified in the original procedures are duplicated or exceeded in the combined procedure. If alternate procedures are used, appropriate information should be provided along with the Environmental Qualification Form, (see Appendix A). 3.7 Test Equipment All stimulus and measurement equipment used in the performance of the tests should be identified by make, model, serial number and the calibration expiration date and/or the valid period of calibration where appropriate. When appropriate, all test equipment calibration standards should be traceable to national and/or international standards. 3.8 Multiple Unit Equipment If the equipment to be tested consists of several separate units, these units may be tested separately, provided the functional aspects are maintained as defined in the relevant equipment specification. 3.9 EUT Configuration for Susceptibility Tests During any environmental test of electrical and electronic equipment (for example, susceptibility test) conducted per DO-160, the equipment under test shall be configured in the most sensitive functioning mode that could be encountered during its normal operation in the field. When the equipment is embedded with basic and/or application software, it must be tested with software functions operating (or simulated) to exhibit the maximum sensitivity to the test environment. The description and the justification for the functional configuration, including software, shall be reported or referenced in the test report. Unless otherwise specified in the applicable minimum performance standard, special purpose test firmware/software is acceptable provided that the hardware and interfaces are comprehensively exercised and yield good test coverage based on validated requirements, and that the configuration is controlled. The special purpose test firmware/software, when used, should be capable of thoroughly exercising the hardware functions. From this point on specific tests are described in more detail for each Section.. SECTION 4 TEMPERATURE AND ALTITUDE 4.1 Purpose of the Tests These tests determine the performance characteristics of equipment in the applicable categories for the temperatures and altitudes specified in Table 4-1 and at the pressures defined in Table

11 a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. Depending on the category of equipment, the temperatures and pressure values (to achieve altitudes per application) shall be stabilized and controlled per specification. c. Operational periods of the EUT shall be monitored per design and specification. a. Be aware of time, temperature and pressure tolerances. Section 4 Temperature and Altitude b. Be sure to document any conversion of unit systems when collecting and interpreting data. c. Higher pressures require added safety measures to prevent injury and damage to test equipment and personnel. 4.2 General Several temperature and altitude test procedures are defined, each to be selected according to the category and use for which the equipment is designed (see Subsection 4.3 and Table 4-1). 4.3 Equipment Categories are described and cover the wide range of environments known to exist in the majority of aircraft types and installation locations. It should be recognized that not all possible combinations of temperatures and altitude limits are covered in these equipment categories. 4.4 Definitions of Terms are given to aid in determining the correct testing required. In-Flight Loss of Cooling - This condition represents the failure of the external or internal system that normally provides dedicated cooling for the equipment. Certain equipment must survive for a limited time with the absence of cooling. Test requirements for this type of equipment shall be specified in the equipment performance specification. 4.5 Temperature Tests Ground Survival Low Temperature Test and Short Time Operating Low Temperature Test This test simulates temperature conditions that may be encountered by equipment while the aircraft is on the ground. 4.6 Altitude, Decompression and Overpressure Tests Refer to Table 4-1 for altitude and to Table 4-2 for pressure values. SECTION 5 TEMPERATURE VARIATION 5.1 Purpose of the Test This test determines performance characteristics of the equipment during temperature variations between high and low operating temperature extremes. Note: The test is not intended to verify the behavior of the equipment in wet or icing conditions. In conducting this test, the test chamber may incorporate the capability of controlling or altering humidity to the extent that condensation is minimized or does not occur. 11

12 a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. Depending on the category of the EUT s use, specified ramp rates apply. 1. These ramp rates can affect the total test cycle time. 2. Faster ramp rates (>10C/min) are considered Temperature Shocks and specific requirements are to be followed. c. The EUT has specified periods of operation/powered events which must be considered. a. These tests take a considerable amount of time. Often they will be run unattended, depending on the length of test cycle; the ambient conditions and EUT operational requirements can be maintained between cycles to allow the test to be carried out when personnel are available to operate test equipment. b. The 2-minute non-operational/unpowered segment is a critical requirement and programming/operation of test equipment should be given careful attention Test Procedure for Various Categories are given Section 5 Temperature Variation SECTION 6 - HUMIDITY 6.1 Purpose of the Test This test determines the ability of the equipment to withstand either natural or induced humid atmospheres. The main adverse effects to be anticipated are: a. Corrosion. b. Change of equipment characteristics resulting from the absorption of humidity. For example: Mechanical (metals) Electrical (conductors and insulators) Chemical (hygroscopic elements) Thermal (insulators) a. Determination of category and test type is specified by the standard and is dependent on the EUT s location of use. b. After the EUT is removed from humidity conditioning, a particular time frame is specified Section 6 Humidity for functionality acceptance. c. EUTs that do not have power applications (mechanical systems) can be post-conditioned thermally per the test procedure. 12

13 a. Most tests are un-powered during exposure, but spot-checks (powered and operating) can be performed at specified times during cycling and for limited durations. b. Sealing interfaces on powered EUTs with the appropriate cable/plug are recommended if available. The use of clay, silicone plugs and butyl rubber tapes provide a weather tight seal for orifices. This sealing is for the support equipment not the EUT. 6.2 Equipment Categories are given 6.3 Test Procedures Subject the equipment to an atmosphere in which the relative humidity (RH) is required for the specific category Conducting Spot Checks For conducting spot checks on the performance of the equipment under test, the equipment may be operated at the end of each of the 6 or 10 cycles as appropriate for a period not to exceed 15 minutes. If the equipment is removed from the test chamber to conduct a spot check, the period of removal shall not exceed 20 minutes, and the equipment shall not be operated for more than 15 minutes of this 20 - minute period Other Specified Checks If the applicable performance standard requires that other checks be made to determine compliance, these shall also be performed during this test. SECTION 7 OPERATIONAL SHOCKS AND CRASH SAFETY 7.1 Purpose of the Tests The operational shock test verifies that the equipment will continue to function within performance standards after exposure to shocks experienced during normal aircraft operations. These shocks may occur during taxiing, landing or when the aircraft encounters sudden gusts in flight. This test applies to all equipment installed on fixed-wing aircraft and helicopters. The crash safety test verifies that certain equipment will not detach from its mountings or separate in a manner that presents a hazard during an emergency landing. NOTE: For fixed-wing aircraft: a complete installation demonstration, i.e. including aircraft acceleration loads (such as flight maneuvering, gust and landing) in addition to the crash safety loads, may be accomplished by using the "Unknown or Random" orientations for the "sustained" test procedure. Section 7 Crash Safety Sustained a. Determination of category and test type is specified by the standard and is dependent on the EUT s location of use. b. Operational shocks have requirements for the EUT s functionality during the applied shocks. c. Crash Safety shocks do not require operation during applied shocks. 1. The EUT s functionality criteria can be evaluated after testing. d. Shocks are applied in 3 orthogonal axes, in both positive and negative directions. 1. The number of shocks and severity are category dependent. 13

14 2. The severities of the shocks are specified by time (ms) and acceleration (g). e. Sustained level shocks are applied as in step d above, but are performed with the use of a centrifuge. a. Some EUT applications require operation/power during Crash Safety Shock levels. b. EUTs can be operated/powered during sustained acceleration on a centrifuge. c. Single accelerometer control is utilized when performing testing. 1. Response accelerometers on the EUT are not required, but can be used if called out in the test procedure. 7.3 Crash Safety If the crash safety test is applicable, both the impulse and sustained test procedures shall be performed Test Procedure 1 (Impulse) Alternate Test Procedure (Impulse) Test Procedure 2 (Sustained) SECTION 8 - VIBRATION 8.1 Purpose of the Tests These tests demonstrate that the equipment complies with the applicable equipment performance standards (including durability requirements) when subjected to vibration levels specified for the appropriate installation. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. The type of vibration is dependent on the category of the EUT. 1. Sinusoidal vibration, random vibration and sine on random categories are specified. c. Sine vibration can identify design characteristics over a frequency band. 1. Resonant frequencies are defined as acceleration of 2x the input acceleration. d. Random vibration simulates real world excitation per application. e. Sine on random tests combines characteristics for robust excitations frequently seen on helicopters. f. The EUT is tested in 3 orthogonal axes (if applicable). Section 8 Vibration g. Response accelerometers are attached to the EUT to verify forces applied during the test. h. The EUT is operational/powered during the test to ensure functionality. a. Proper fixturing is required to measure the EUT s response characteristics during the test. 1. Fixturing should mimic the EUT s mounting application to simulate its in-use characteristics. 2. Fixturing can also rigidly isolate the EUT for durability during product screening. 14

15 b. Averaging control can eliminate off-axis crosstalk that could induce transient forces into the EUT. 8.2 Applicability The vibration tests described below apply to equipment installed on fixed-wing propeller aircraft, fixedwing turbojet, turbofan, and propfan aircraft and helicopters Vibration Test Category Definitions The appropriate category (or categories) should be based upon the level of assurance required for the equipment s demonstration of performance. CAUTION: A full analysis of vibration levels related to some specific engine imbalance conditions has not been evaluated against these limits. Therefore this test alone may not be sufficient for some applications without additional tests or analysis Test Description The data in Table 8-0 provides a brief description of the test for each of the test categories. See the procedures for a more detailed description. Table 8-0 Test Description 8.3 Vibration Test Requirements The testing set-up is given along with details of sinusoidal random and high-level, short duration vibration testing. 15

16 During this vibration period, also perform an APSD analysis of the vibration response measurements on the equipment. Specific testing procedures for helicopters are also outlined SECTION 9 EXPLOSIVE ATMOSPHERE 9.1 Purpose of the Test This test specifies requirements and procedures for aircraft equipment that may come into contact with flammable fluids and vapors such as those specified in the standard. It also refers to normal and fault conditions that could occur in areas that are or may be subjected to flammable fluids and vapors during flight operations. The flammable test fluids, vapors or gases referred to in this section simulate those normally used in conventional aircraft and that require oxygen for combustion [e.g., monofuels (containing an oxidizer) are not included]. These standards do not relate to potentially dangerous environments occurring as a result of leakage from goods carried on the aircraft as baggage or cargo. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. The containment chamber is designed such that the explosion is contained within the chamber so that only the EUT is affected. 1. The fuel mixture is specified and ignition source is controlled. 2. The explosiveness (concentration) of the mixture is to be measured. c. The EUT operation can, depending on the category, ignite the explosive atmosphere or it can be ignited from an external source. d. The EUT can, depending on the category, be required to survive the ignited explosive atmosphere and remain functional. a. The EUT case can be opened or altered to allow circulation of the explosive mixture. b. The EUT can be operated/powered and monitored externally during testing. c. The chamber can be equipped with a sight glass or video monitoring system to collect visual data. Sequencing, Note: The explosive atmosphere tests shall not be conducted prior to any other DO-160/EUROCAE ED-14 tests except flammability test (see Subsection 3.2, Order of Tests ). 9.3 Equipment Categories are listed Details of Fuel Mixtures are given Failure Criteria is discussed User s Guide, Appendix 9 (this is contained in part as an example of a User s Guide) Section 9 defines the environment, test procedures and requirements. In order to properly interpret the procedures and requirements outlined in Section 9, a User s Guide is provided in Appendix 9. The User s Guide includes rationale, guidance and background information for the environment, test procedures and requirements, guidance in applying the requirements, and lessons learned from aircraft and laboratory experience. This information should help users understand the intent behind the requirements, aid in tailoring (making adjustments to the test procedure, which deviates from the 16

17 standard) the requirements as necessary for particular applications and should help user s develop detailed test procedures based on the general test procedures in Section 9. The User s Guide follows a parallel format to the main body of Section 9 for easy cross reference. Paragraph numbers corresponding to each paragraph in Section 9 are included in the User s Guide. Where there is no additional information provided in the User s Guide, the paragraph header is provided but the following paragraph is left blank. 9.A.1 Purpose of the Test This section of DO-160 is intended to provide test procedures and test levels that can be used to test equipment for explosive atmosphere. It is the responsibility of the installer to make sure the test results satisfy the certification requirements of the proposed installation. This User s Guide does not contain requirements; it is intended to provide background information and considerations that improve the likelihood of successful test results. 9.A.2 Explosion Proof Aircraft Zone Definitions and Equipment Requirements are called out. 9.A.5 Equipment Design and Installation Information is explained 9.A.6 Test Procedures is defined in detail 9.A Failure Criteria is explained SECTION 10 WATER PROOFNESS 10.1 Purpose of the Test These tests determine whether the equipment can withstand the effects of liquid water being sprayed or falling on the equipment or the effects of condensation. These tests are not intended to verify performance of hermetically sealed equipment. Therefore, hermetically sealed equipment may be considered to have met all water proofness requirements without further testing. Equipment shall be considered hermetically sealed when the seal is permanent and airtight. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. Procedures include: 1. Condensing Water Proof Test - EUT operational last 10 minutes of exposure. 2. Drip Proof Test - EUT non-operational during test. 3. Spray Proof Test - EUT operational during test. 4. Continuous Stream Proof Test - EUT nonoperational during test. Section 10 Waterproofness a. Perform calibration runs of flow rates/drip fallout (collected moisture) prior to testing the EUT. b. Ensure measurements are verified with calibrated equipment. c. Temperature controlled water supply is necessary for Continuous Stream Proof Test. 17

18 d. The specified drip tray mounted level delivers the uniform drip rate across the EUT Equipment Categories are listed. SECTION 11 FLUIDS SUSCEPTIBILITY 11.1 Purpose of the Test These tests determine whether the materials used in the construction of the equipment can withstand the effects of aircraft fluid exposure Precautions Since many contaminants may have flash points within the test temperature range, care should be taken to ensure that adequate safety measures are taken to limit the possibility of fire or explosion. Some contaminants may themselves, or in combination with other contaminants, or with the test sample, be toxic. Due consideration should be given to this possibility before commencing the tests. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. Depending on the EUT s category, fluid susceptibility is administered via spray or immersed. c. EUTs subjected to fluid testing are to operate per specification. d. This test is used to determine the adverse affects which might occur if the EUT is exposed to various fluids. Section 11 Fluids Susceptibility a. Spay Test is cycled between fluid applications and a drying period. b. Three 24-hour cycles per fluid type. c. 8 hours of spray and 16 hours 65 C. 1. During the last 10 minutes of the 3 rd cycle of spray, the EUT is operated. 2. The EUT shall operate for 30 minutes after the 3 rd drying cycle, but only after ambient stabilization of the EUT has occurred. i. The above procedure is to be repeated for each fluid tested. d. Immersion testing requires an EUT to be completely immersed in a specified fluid. 1. The EUT is immersed for 24 hours. 2. The EUT is to operate at the completion of 24 hours for 10 minutes while completely immersed. 3. The EUT is placed in a constant temperature of 65 C for 160 hours. 4. The EUT is to return to ambient temperature and operate for 2 hours. e. The above procedure is to be repeated for each fluid tested Equipment Categories Category F is equipment that has passed the tests covered in this section. Details of the test fluids involved and the methods used shall be provided in the Environmental Qualification Form (See Appendix-A). 18

19 Note: Section 11.0 covers seven general classes of other contaminating fluids. In addition there are 25 specific fluids that are used to test these classes. Table 11-1 contains the class of fluids, the specific fluids and the temperatures required in these tests. Testing of all 25 fluids or all 7 general classes of contaminated fluids is not required to claim Category F. It is required to specify fluids used, test method and temperature of exposure in the test procedure and in the Environmental Qualification Form Test Procedures Spray Test Immersion Test 11.5 Use of Material Specimens The material specimen tests may be used in place of equipment tests. The results of these tests shall assure that the material will protect the equipment from harmful effects after being exposed to the relevant fluid in the manner defined in the equipment test procedures. SECTION 12 - SAND AND DUST 12.1 Purpose of the Test This test determines the resistance of the equipment to the effects of blowing sand and dust where carried by air movement at moderate speeds. The main adverse effects to be anticipated are: a. Penetration into cracks, crevices, bearings and joints, causing fouling and/or clogging of moving parts, relays, filters, etc. b. Formation of electrically conductive bridges. c. Action as nucleus for the collection of water vapor, including secondary effects of possible corrosion. d. Pollution of fluids. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. Dust testing 1. Chamber temperature and relative humidity is monitored and controlled. 2. EUTs are exposed for 1 hour along each orthogonal axis. c. Sand Testing 1. Sand concentrations vary depending on the EUT s intended use and location. 2. The EUT should be 3 meters from the sand injection point. 3. Wind velocity should range between ~ 40 to 60 miles per hour. 4. Chamber temperature and relative humidity is monitored and controlled. b. EUTs may be operated/powered during the test. Section 12 Sand and Dust 19

20 c. Verify EUTs visually after each axis. Sequencing NOTE: Consideration must be given in determining where in the sequence of environmental tests to apply this test procedure, as dust residue from this test procedure, combined with other environmental synergistic effects may corrode or cause mold growth on the test item and adversely influence the outcome of succeeding test procedures. Sand abrasion may also influence the results of the salt spray, fungus or humidity test procedures Categories of Equipment are listed 12.3 Agents Dust Dust used in a suitable test chamber shall be raised and maintained at a concentration of 3.5 to 8.8 g/m3 and shall be 97% to 99% silicon dioxide. The dust characteristics are detailed Sand (1) If sand concentration data is available for the worst-case field environment the equipment is expected to properly function in, then test to that sand concentration level. (2) Material likely to be used close to helicopters operating over unpaved surfaces is defined. (3) Material never used or exposed in the vicinity of operating aircraft, but which may be used or stored unprotected near operating surface vehicles is defined. (4) Material that will be subjected only to natural conditions is defined. Section 12 Dust Test 12.4 Dust Test Procedure The equipment shall be submitted to the dust test along each direction of each major orthogonal axis in succession. Note 1: Unless otherwise required in the relevant specification, the equipment is not required to operate during the exposure period. Note 2: Health and safety regulations regarding the use of dust should be observed Sand Test Procedure The test item shall be submitted to the sand test at wind velocities ranging from m/second, with the exposed surface positioned 3m from the sand injection point to allow sand particles to reach terminal wind velocities before impacting the test item. If the test item will not directly see wind velocities of this magnitude during normal service life (cockpit screen displays) then the test item shall be submitted to air velocities of 0.5 and 2.4 m/second. Note 1: Unless otherwise required in the relevant specification, the equipment is not required to operate during the exposure period. Section 12 Sand Test At the end of this exposure period, the equipment shall be removed from the chamber and cooled to room temperature. Externally accumulated sand only on surfaces of the equipment required to verify 20

21 proper operation (e.g. displays, connectors, keyboards, test ports etc.) shall be removed by brushing, wiping, or shaking with care being taken to avoid introducing additional sand into the equipment. Under no circumstances shall sand be removed by either air blast or vacuum cleaning. SECTION 13 FUNGUS RESISTANCE 13.1 Purpose of the Test These tests determine whether equipment material is adversely affected by fungi under conditions favorable for their development, namely, high humidity, warm atmosphere and presence of inorganic salts. Notes: A. Fungi proximity to other materials, exposure to daily susceptible contaminants such as fluids during routine operation and maintenance, or equipment exposure to solar actinic effects may break molecular bonds and reduce the item to sub-compositions which may be fungus nutrients. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. Equipment that is installed in an environment where it will be exposed to severe fungus contamination is identified as Category F and shall be subjected to the fungus resistance test. c. This test is to determine if any adverse affects will occur if the material is exposed to a fungus. d. This test shall not be conducted after Salt Spray or Sand and Dust. A heavy concentration of salt may affect the fungal growth, and sand and dust can provide nutrients, which could compromise the validity of this test. e. Materials can be directly and indirectly attacked by fungus. 1. Most susceptible to attack are mineral based materials. i. Natural materials (carbon based), cellulose materials (wood, paper, fiber textiles, cordage), animal and vegetable-based adhesives, grease, oils, hydrocarbons and leather are prone to attack. ii. Synthetic materials, PVC formulations, polyurethanes, plastics, paints and varnishes also can be attacked by fungus. f. This test can be performed on a non-functioning device or component. g. A specified fungi is grown to specifications and applied to control and test items. 1. The controls and test items are incubated per the standard. 2. Items are evaluated for type of fungal growth and their effect on the test items. a. The fungal growth on a test item is analyzed to determine the species, and if the growth is on the test item material(s) or on contaminants. 1. Fungal growth on test item materials is examined for the extent of growth. 2. The extent of growth on susceptible components or materials must be completely described e.g. i. The immediate effect that the growth has on the physical characteristics of the material ii. The long-range effect that the growth could have on the material iii. The specific material [nutrient(s)] supporting the growth b. The evaluation of human factor effects (including health risks) should also be performed. 21

22 B. Sequence - This test shall not be conducted after Salt Spray or Sand and Dust. A heavy concentration of salt may affect the fungal growth, and sand and dust can provide nutrients which could compromise the validity of this test Categories of Equipment Category F: equipment that is installed in an environment where it will be exposed to severe fungus contamination Apparatus The apparatus required to conduct this test consists of chambers or cabinets together with auxiliary instrumentation capable of maintaining the specified condition of temperature and humidity. Provisions shall be made to prevent condensation from dripping on the test item. There shall be free circulation of air around the test item and the contact area of fixtures supporting the test item shall be kept to a minimum. When forced air is employed, the flow should not exceed one meter per second over the surface of the test specimen. SECTION 14 - SALT FOG 14.1 Purpose of the Test This test determines the effects on the equipment of prolonged exposure to a salt atmosphere or to salt fog experienced in normal operations. The main adverse effects to be anticipated are: a. Corrosion of metals. b. Clogging or binding of moving parts as a result of salt deposits. c. Insulation fault. d. Damage to contacts and uncoated wiring. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. A salt solution of 5% by weight of sodium iodine and distilled or demineralized water is atomized at 35 C. a. EUT should be positioned inside the chamber so that there is no overlapping or test Section 14 Salt Fog apparatuses that will shield or cause run off onto the EUT. b. Place the EUT s top most surface parallel to the top of the fog-emitting nozzle. c. Collection receptacles (2) shall be placed within the chamber; 1 placed at the perimeter edge of the EUT nearest to the nozzle and another at the perimeter of the EUT but at the farthest d. point from the nozzle. Sequencing, Note: The salt fog test shall not be conducted prior to the fungus resistance test, see Sequence Subsection 3.2, Order of Tests 14.2 Categories of Equipment are described 14.3 Apparatus 22

23 SECTION 15 - MAGNETIC EFFECT 15.1 Purpose of the Test This test determines the magnetic effect of the equipment and is mainly intended for finding or proving the closest distance to compasses or compass sensors (flux gates) at which that unit is allowed to be installed. This test ensures that equipment can operate properly without interference which may affect nearby equipment, determining equipment compliance with the applicable equipment performance standard or assisting the installer in choosing the proper location of the equipment in the aircraft Test Procedure is given a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. Tests should be performed away from any sources of magnetic field. c. You might want to perform the test outside of the shield room. d. Mode of operation can affect magnetic emissions of the EUT. e. Do not deviate from general RTCA set up. f. To improve testing efficiency, perform Section 15 Magnetic Effect Section 15 first or last to prevent excessive set up time. g. The test requires 14.4 amps/meter +/-10% which is the minimum ambient you must be below. h. Background magnetic field reading can be found at local airports. a. You are moving the compass not the EUT during this test to determine the distance where deflection occurs. SECTION 16 - POWER INPUT 16.1 Purpose of the Test This section defines test conditions and procedures for ac and dc electrical power applied to the terminals of the equipment under test. This is the equivalent of power quality issues being applied to the power input to the equipment. It covers the following electrical power supplies: 14 V dc, 28 V dc and 270 V dc 115 V rms ac and 230 V rms ac at either a nominal 400 Hz frequency or over a variable frequency range which includes 400 Hz. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. 23

24 b. This tests power quality issues which might be experienced by the EUT in an installation from the power feeding the EUT. c. This test is intended to simulate everything a device in an airplane might see during operation, such as: 1. When the aircraft is sitting at the terminal receiving terminal power 2. The possible voltage sags from starting the engines when disconnected from outside power sources Section 16 Power Input 3. The inductive kick from another system inside the aircraft, or any systems which might come on line during normal operation. d. The phenomena used are based on threats observed as well as speculated. They include normal, abnormal, and emergency operation running on ATU, auxiliary generators, batteries, battery packs, etc. which might include over voltages, under voltages, disruptions of power, as well as harmonic content. e. An oscilloscope should be present to verify proper application of test waveforms. f. Power line transients for ac powered equipment can be difficult to capture effectively on an oscilloscope. g. Various levels of severity are used depending on the category. a. Care needs to be taken to ensure proper wiring to the Section 16 programmable power supply, specifically reverse polarity with dc power equipment. b. Solution to problems might relate to sense and cut off circuits, over voltage clamps, MOV, protection diodes or something that clamps to the rail voltage. c. Do not use crowbars circuits, as they would shut the power down. d. When you have a voltage dropout, you may need to bridge the voltage with large capacitors to supply the voltage. SECTION 17 - VOLTAGE SPIKE 17.1 Purpose of the Test This test determines whether the equipment can withstand the effects of voltage spikes arriving at the equipment on its power leads, either ac or dc. The main adverse effects to be anticipated are: a. Permanent damage, component failure, insulation breakdown. b. Susceptibility degradation or changes in equipment performance. a. Determination of category is specified by the standard and is dependent on the Section 17 Voltage Spike 24

25 EUT s location of use. b. 2 levels: Category A-600 volts and Category B Double Line voltage. c. To protect against voltage spikes you might use transient diodes, Transient Voltage Suppressive (TVS) device and MOVs. a. Can be permanently destructive since the level can be up to 600V. b. To protect against voltage spikes you might use transient diodes, Transient Voltage Suppressive (TVS) devices and MOVs Equipment Categories are listed 17.3 Test Setup and Apparatus The transient generator used shall produce the waveforms shown in the section Test Procedure With the equipment under test disconnected, the transient wave shape shall be verified. NOTE: If performance is measured during the application of this test, then the performance requirements contained in the applicable equipment performance standard apply. SECTION 18 AUDIO FREQUENCY CONDUCTED SUSCEPTIBILITY 18.1 Purpose of the Test This test determines whether the equipment will accept frequency components of a magnitude normally expected when the equipment is installed in the aircraft. These frequency components are normally harmonically related to the power source fundamental frequency. Section 18 Audio Frequency CS a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. DC testing starts at 30 Hz; AC starts at the 2 nd harmonic. c. You may be able to remedy problems with capacitors or a filter. d. Care must be taken when designing the EUT and setting the over voltage and under voltage sensing. Since the test is ripple riding on the normal power, sometimes just changing the sense level will solve any problems. a. For each test you have to dwell for 1 minute at each frequency making this a long test. b. This test is meant to simulate fluctuations & harmonics from the mains ac and dc power buses Equipment Categories - Test designation for equipment consists of various categories and are detailed. 25

26 18.3 Test Procedures Unless otherwise specified, the EUT shall be supplied at the nominal input voltage during performance of the tests. Section 18 User s Guide is supplied SECTION 19 - INDUCED SIGNAL SUSCEPTIBILITY 19.1 Purpose of the Test This test determines whether the equipment interconnect circuit configuration will accept a level of induced voltages caused by the installation environment. This section relates specifically to interfering signals related to the power frequency and its harmonics, audio frequency signals, and electrical transients that are generated by other on-board equipment or systems and coupled to sensitive circuits within the EUT through its interconnecting wiring. Power leads tested under Section 18 are exempt from this test. Section Induced Signal Susceptibility a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. There are 4 tests for DO-160 before Rev G and 1 additional test added for DO-160G. These tests are Electric fields into cables, magnetic fields to the EUT and to cables, spikes into cables. c. The fifth test is electric fields to the EUT, on a wire swept across the equipment surfaces. d. Electric field on a wire up to 5400V/m coupled to cable bundle. The term per meter is based on a wire one-meter wire length with the required voltage applied. e. 400 Hz electric field is tested to 170 V rms to the EUT only. A 20cm long wire is swept across the equipment faces spaced 1 cm away from the surface. f. Problems are often fixed by shielding. g. Some aircraft now have variable frequency systems because of direct drive, so 400Hz is not the only frequency required to be tested. h. Today testing is done from 350 Hz lowest frequency, to 800 Hz highest frequency for RTCA and to 900 Hz for Airbus. i. During , safety shall be considered due to high voltages present from the output transformer. j. Test level for interconnecting cable. Tests are determined by length of the wire exposed to the radiating wire, e.g. a 5 meter cable would require a 5 meter test wire. a. Electronic signals/digital signals are more susceptible to chattering relay whereas analog signals are more susceptible to magnetic field & electric field induced signals Equipment Categories are described in detail Magnetic Fields Induced Into the Equipment Electric Fields Induced Into the Equipment 26

27 Magnetic Fields Induced Into Interconnecting Electric Fields Induced Into Interconnecting Spikes Induced Into Interconnecting Cables SECTION 20 - RADIO FREQUENCY SUSCEPTIBILITY (Radiated and Conducted) 20.1 Purpose of the Test These tests determine whether equipment will operate within performance specifications when the equipment and its interconnecting wiring are exposed to a level of RF modulated power, either by a radiated RF field or by injection probe induction onto the power lines and interface circuit wiring. Entire aircraft wire harness ready to test Section 20 Reverberation Chamber a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. In this test electric fields are generated and exposed to circuits, cables and systems. The fields can be picked up by the wires which create unwanted signals. These unwanted signals can cause a device, circuit or system to malfunction. c. Very often it is the modulation which is combined with the RF field that enters a circuit via the original RF. The modulation is stripped off through a diode somewhere in the device causing an analog level to shift creating a failure. d. Electric fields vary from 5 V/m to 7200 V/m (HIRF levels) and are pulsed at 4 and 10 µs. e. Remove EUT to calibrate the field; this is called substitution. This is different from the way MIL STD 461 tests, where the field is monitored and leveled during the test. f. Reverb is an alternate procedure. a. Shielding with proper terminations of the shield, combined with possible filtering might be used here to remove the unwanted effects Equipment Categories are given in detail 20.3 General Test Requirements 27

28 Equipment Under Test The EUT shall be set up on a ground plane (test bench) and configured in accordance with the criteria list involving: (1) Ground (2) Shock and Vibration (3) Electrical Bonding (4) External Ground Terminal (5) Interconnecting Wiring/Cables unless otherwise specified in the aircraft installation specification. Data Required in Test Report is also given User Guide to Section 20 Radio Frequency Susceptibility (Radiated and Conducted) Pass/Fail Criteria 20.4 Conducted Susceptibility (CS) Test 20.5 Radiated Susceptibility (RS) Test In the User Guide there is a discussion of the use of Reverberation Chambers (RC). These chambers are an alternate means of generating high-level fields. It should always be noted that there is a great difference in using this method and only limits defined as RC limits should be used. SECTION 21 EMISSION OF RADIO FREQUENCY ENERGY 21.1 Purpose of the Test These tests determine that the equipment does not emit undesired RF noise in excess of the levels specified in the standard. The notches specified in the radiated emissions limits are included to protect aircraft RF sensors operating frequencies Equipment Categories are defined. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. Many electronic devices generate harmonic frequencies of the normal frequencies being processed. These harmonics can be hundreds of times Setting up Emissions Testing greater than the original frequencies. c. A good rule to consider is keeping in mind the path of the intentional energy and then determining what the return path is. d. Cables may require shielding with proper terminations. a. Frequencies from power switching such as motor controls and lighting controls might be at low frequencies but the harmonics can be found at 100s of MHz. b. All measurements are done in the peak mode during testing. DO-160 A-C have both narrow band as well as broad band while DO-160 D-G measure only narrow band. 28

29 c. Radiated emission requirements from up to & including Rev F starts at 30 MHz while Rev G starts at 100 MHz. d. Conducted emissions stop at 30 MHz for Rev F and below; with Rev G, conducted emissions are measured to 100MHz. e. Conducted testing measurements are done as a current not a voltage test. f. Conducted emissions measurements are done at the EUT not the LISN. g. Limits might be much lower in the aircraft communication bands for some categories. h. There is a specific statement in the standard for which you might have to adjust your sweep, your dwell, and scan times according to what the product does, how it behaves and its mode of operation so you will capture all the worst case emissions. You may need to scan multiple times to capture the cycling of the equipment under test General Requirements This section does not measure or control spurious signals conducted out of the antenna terminals of receivers or transmitters. For emission measurements, the entire frequency range for each applicable test shall be scanned. Minimum measurement time for analog measurement receivers during emission testing shall be as specified in Table 1. Synthesized measurement receivers shall step in one-half bandwidth increments or less, and the measurement dwell time shall be as specified in Table 1. User Guide to Section 21 Emission of Radio Frequency Energy Section 21 defines limits, test procedures and requirements. In order to properly interpret the procedures and requirements outlined in Section 21, a User's Guide is provided as an Appendix. The User's Guide includes rationale, guidance and background information for the environment, test procedures and requirements, guidance in applying the requirements, and lessons learned from aircraft and laboratory experience. This information should help users understand the intent behind the requirements, should aid in tailoring requirements as necessary for particular applications and should help user's develop detailed test procedures based on the general test procedures in Section 21. SECTION 22 - LIGHTNING INDUCED TRANSIENT SUSCEPTIBILITY 22.1 Purpose of Tests These test methods and procedures are provided to verify the capability of equipment to withstand a selection of test transients defined in this section which are intended to represent the induced effects of lightning. The waveforms and levels, and the pass/fail criteria for equipment performance during the test shall be listed in the applicable equipment test procedure. Two groups of tests may be used for equipment qualification. The first is a damage tolerance test performed using pin injection as described in paragraph The second group, as described in paragraph , evaluates the functional upset tolerance of equipment when transients are Induced Lightning Testing applied to interconnecting cable bundles. Cable bundle tests include single stroke, multiple stroke, and multiple burst response tests. Cable bundle tests can also provide an indication of damage tolerance. Note: These tests may not cover all aspects of lightning induced interaction and effects on equipment. Additional tests such as tests of the equipment in a complete system may be required to achieve certification of a specific installation, depending upon the 29

30 functions performed. For externally mounted equipment, direct effects tests may also be required. These tests are covered in Section 23 of this document. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. Whenever high energy is exposed to an aircraft there will be some energy which penetrates into the aircraft. This test is an attempt to simulate these effects and determine if the EUT malfunctions. c. Whenever these high energy levels flow, it will be imperative to make sure the grounding is correct and representative of the aircraft ground. d. Most products pass levels up to level 3. Products begin to fail at levels 4 & 5. e. The pin injection test is more of a dielectric break down test. f. Shielding works well for bundle injection but pin injection requires filtering right at the pin. g. Powered pin injection testing may require custom blocking devices. a. This test can be destructive so it needs to be considered ahead of time. b. TVS diodes and MOVs are used to protect the device. c. Depending on what you are protecting against, shielding works well for bundle injection where filtering at the pin itself is required for pin injection Definitions of terms are given User s Guide Appendix 22 Lightning Induced Transient Susceptibility SECTION 23 LIGHTNING DIRECT EFFECTS 23.1 Purpose of Tests The tests described in this section are intended to determine the ability of externally mounted equipment to withstand the direct effects of a lightning strike externally to the main skin of the aircraft and include all such equipment that is covered only by a dielectric skin or fairing that is an integral part of the equipment. This section also includes connecting cables and associated terminal equipment furnished by the equipment manufacturer as a part of the equipment. a. Determination of category is specified by the Section 23 Lightning Direct Effects standard and is dependent on the EUT s location of use. b. These are very high energy levels. Current levels can reach 200,000 amps & testing to 100s of thousands of volts. c. It has the potential to crack glass, damage housing and can even melt metal. d. The test relates to a limited number of devices which might be mounted externally to the aircraft. e. The EUT is usually powered. f. Must have actual fasteners, gaskets, etc. that are used on the aircraft. 30

31 a. This test can be destructive and needs to be considered ahead of time. SECTION 24 - ICING 24.1 Purpose of the Test These tests determine performance characteristics for equipment that must operate when exposed to icing conditions that would be encountered under conditions of rapid changes in temperature, altitude and humidity. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. a. Moving a EUT between a (cold) temperature chamber and a warm, humid chamber to form condensation and re-freezing of condensation requires 2 chambers relatively close together. Section 24 Icing 1. Monitoring the surface temperature of the EUT is critical to determine at what temperature it is ready to be cycled back into the cold chamber for freezing of condensation. b. Category B requires the use of a chamber that can control temperature, humidity and altitude (pressure). c. Category C requires the application of clear, hard ice (glazed ice) on the EUT applied by a chilled water spray in a chilled chamber to a specified accumulation General Three icing test procedures are specified according to the category for which the equipment is designed to be used and installed in the aircraft (see Subsection 24.3). Note: The selection of icing category depends on equipment location in (or on) the aircraft and the type of icing conditions expected. These conditions must be considered by the equipment designer in evaluating these requirements, which are determined by the end application and use of the equipment. These tests generally apply to equipment mounted on external surfaces or in non - temperature controlled areas of the aircraft where rapid changes in temperature, altitude and humidity are generally encountered Equipment Categories are detailed 24.4 Test Procedure General Mount the equipment under test in a manner representative of the normal installation in the aircraft. Remove all non-representative contaminants, such as oil, grease and dirt, which would affect adhesion between ice and the surfaces of the equipment under test, before beginning the appropriate tests. Operation of equipment that generates heat shall be limited to only that period of time necessary to determine compliance. Note: This test is designed to expose the equipment alternately to cold dry and warm moist environments. The use of separate chambers representing these two distinct environments is 31

32 recommended. Note: If multiple tests with increasing thickness of ice formation are required, a series of separate tests shall be performed with each thickness level formed in a continuous operation. SECTION 25 - ELECTROSTATIC DISCHARGE (ESD) 25.1 Scope The Electrostatic Discharge (ESD) test relates to airborne equipment which may be involved in static electricity discharges from human contact. Some factors contributing to an ESD event may be: low relative humidity, temperature, use of low conductivity (artificial fiber) carpets, vinyl seats and plastic structures which may exist in all locations within an aircraft. This test is applicable for all equipment and surfaces, which are accessible during normal operation and/or maintenance of the aircraft. This test is not applicable to connector pins Purpose of the Test Section 25 Electrostatic Discharge (ESD) The electrostatic discharge test is designed to determine the immunity or the ability of equipment to perform its intended function without permanent degradation of performance as a result of an air discharged electrostatic pulse. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. Care should be taken to discharge at the proper point on the EUT. c. ESD grounding strap should be kept away from the EUT to prevent secondary effect caused d. by the current affecting the EUT. e. Levels of 15,000 volts air discharge. f. ESD discharge tip is 150pf and 330 Ohms. g. ESD testing is not done to pins unless required by the test procedure. h. Only testing to the 15,000 volt level is required, unlike the European Community where you test to multiple levels. i. This is one of the last tests to perform since it might be destructive. a. EUT construction and grounding can impact ESD results Test Description The immunity to electrostatic discharge shall be determined by the ability of the equipment under test (EUT) to withstand a series of electrostatic discharge pulses at a test level of 15,000 volts, directed at specific human contact locations on the EUT Equipment Categories Category A - Electronic equipment that is installed or operated during normal operation and/or maintenance of the aircraft. 32

33 25.5 Test Procedure With the equipment powered and operated in the required mode, the electrostatic discharge test will be performed under the specified conditions ESD Generator details are given EUT Test Modes EUT test modes shall include software (if applicable) chosen to exercise all normal modes of operation of the EUT. Note: If monitoring equipment is required, it should be decoupled in order to reduce the possibility of erroneous failure indications. SECTION 26 FIRE, FLAMMABILITY 26.1 Purpose This section defines test conditions and procedures for Flammability and Fire resistance. a. Determination of category is specified by the standard and is dependent on the EUT s location of use. b. The use of burners, flame temperature, application and intensity are specified for each. Section 26 Flammability a. Fireproof: With the EUT operating, the normal flame is applied for 15 minutes. 1. Only the first 5 minutes of the test determine compliance with applicable equipment per performance standards. 2. After an additional 10 minutes, the EUT shall be inspected and show no evidence of continued combustion or flame propagation and be self-extinguishing. b. Fire Resistant: With the EUT operating, the flame is applied for 5 minutes. 1. The equipment shall be inspected and show no structural default or evidence of continued combustion or flame propagation and should self-extinguish. 2. Any leakage or continued burning of the EUT at the end of the 5 minutes would be considered a test failure unless it can be shown that there is not a significant increase in the overall fire hazard. c. Flammability: Depending on the component, specified methods are conducted. 1. Test items are conditioned at 21 C and 50% RH for 24 hours prior to testing. 2. Monitor and record flammability criteria as specified Applicability Flammability and fire tests apply to equipment installed on fixed wing propeller driven aircraft, fixedwing turbojet aircraft, turbofan aircraft, prop fan aircraft, and helicopters. These tests are applicable for equipment mounted in pressurized zones, in fire zones, in non-pressurized and non-fire zones Equipment Categories are detailed Note: If all materials used in the construction of the equipment can be shown to meet the equivalent 33