DO-160-Section-22-Lightning-Induced-Transient-Susceptibility

RTCA DO-160 Section 22.0 Lightning Induced Transient Susceptibility

The RTCA DO-160 lightning-induced transient susceptibility tests simulate lightning. The standard specifies the transients to be induced on the equipment. The actual testing parameters are specified in the applicable equipment specification. These parameters include the levels and the waveforms. Equipment specification also outlines the pass / fail criteria.

RTCA-DO-160G lightning testing can be conducted in one of two groups. The first group is a damage tolerance test. This is conducted using pin injection. The second test evaluates the functional upset tolerance. This tolerance is evaluated when transients applied to interconnecting cable bundles. There are a number of cable bundle tests. These include single stroke, multiple stroke and multiple burst. These cable bundle susceptibility tests can provide an indication of damage tolerance.

The RTCA/DO-160 test standard defines the various components included in the transient susceptibility testing. Below are some of the definitions included in the RTCA DO-160G susceptibility standard.

  • Cable Bundle is a group of wires and/or cables bound or routed together. This bundle connects a piece of equipment to one or more pieces of equipment comprising the system under test.
  • Calibration Loop is a heavy duty, low self-inductance, low resistance, single turn wire loop. The loop is passed through the injection transformer to form an insulated secondary winding. It should be low enough in impedance to achieve the test level and waveform.
  • Core Wire is an individual wire inside a shield. The individual wire induced voltages/currents are reduced from the driven loop voltages/currents. This occurs by the presence of the shield (i.e. by the shield transfer impedance).
  • Generator is a set of equipment (waveform synthesizer, amplifiers, couplers, etc.) that delivers a voltage or current waveform. This delivery is via direct or indirect coupling to the equipment under test (EUT).
  • Local Ground is defined as any ground strap or conductor less than 1 meter in length that is connected two places. The first connections is to the equipment. The second connection is to the same part of airframe structure to which that equipment is installed. The ground strap or conductor would therefore be bonded to the same ground plane that the equipment is mounted to. During a lightning strike, it would be at the same structural voltage potential as the equipment.
  • Monitor Loop is a close fitting, single turn, wire loop wound through the injection transformer to form an insulated secondary winding. It is used to monitor the induced cable bundle or calibration loop voltage.
  • Multiple Burst Applications are a set of transient waveforms intended to represent the induced effects of the external lightning Multiple Burst Waveform Set in aircraft wiring. The Multiple Burst Application includes an induced transient corresponding to each current pulse in the external environment. Each of the induced transients is the response to the external environment. There are three groups of twenty transients in the Multiple Burst Application.
  • Multiple Stroke Applications are a set of transient waveforms. These waveforms are intended to represent the induced effects of the external lightning Multiple Stroke Waveform Set in aircraft wiring. The Multiple Stroke Application includes an induced transient waveform corresponding to each stroke in the external multiple stroke environment. There are fourteen transients in the Multiple Stroke Application. The first induced transient is the response to first return stroke of the external environment and the following thirteen transients are the response to follow on or multiple return strokes of the external lightning environment.
  • A Shield is a conductor which is grounded to an equipment case or aircraft structure at both ends. It is routed in parallel with and bound within a cable bundle. It is usually a wire braid around some of the wires or cables in the cable bundle. It may also be a metallic conduit, channel or wire grounded at both ends within the cable bundle. The effect of the shield is to provide a low resistance path between equipment so connected.
  • Shielded Cable Bundle is a cable bundle that contains one or more shields. Such cable bundles may include some unshielded wires.
  • Single Stroke Response is a representative wiring response to the most severe external component of a lightning strike to an aircraft.
  • Transfer Impedance is a ratio of the core wire open circuit voltage to the shield current.
  • Unshielded Cable Bundle is a cable bundle that contains no shields.

Keystone Compliance is one of the leading indirect lightning test labs in the country. With seven EMC test chambers a substantial amount of test equipment, we are able to offer shot lead times on scheduling. Our engineers provide communication throughout the entire test program. If challenges arise during the testing, our engineers will provide engineering guidance and problem resolution. Our indirect lightning test lab is 17025 accredited to RTCADO-160 testing. In addition to providing RTCA-DO-160G testing, Keystone is accredited to all previous versions of this military test standard as well.

Our EMC-EMI test lab can accommodate small and large items. Please contact us to see firsthand why so many manufacturers rely on Keystone Compliance to be their RTCA DO-160 test lab.

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Modifications from one Version of RTCA DO-160 to the Next:

Changes from DO-160C Indirect Lightning Testing to DO-160D Indirect Lightning Testing

DO-160D Change No. 3, published December 2002, added additional waveform sets, cable bundle test levels, and the procedures for performing indirect lightning multiple stroke and multiple burst tests using the existing defined test waveforms.  The category designations were modified to allow users to designate categories that indicated that these additional tests had been performed. New Waveform Set designators, G through K, were added to cover the Multiple Burst and Multiple Stroke tests. Another significant addition to Change 3 was setup information on performing pin injection tests with power applied. Several different setup diagrams were added to assist users in performing these tests properly. Improperly connecting the lightning generator to a pin with power applied could result in insufficient stress on the pin.

Changes from DO-160D Indirect Lightning Testing to DO-160E Indirect Lightning Testing

The DO-160E cable bundle test section was modified to include a new section providing guidance for performing cable bundle tests on bundles that normally contain shields, with the shields removed.  This guidance allowed testing of a cable bundle at test levels currently defined in DO-160, but intended to demonstrate compliance to aircraft installation threats that are higher than these standardized levels.  It explicitly stated that the test generator used for cable bundle testing does not need to be capable of producing the voltage or current limit level, provided that the current or voltage test level can be achieved on the cable under test.

Changes from DO-160E Indirect Lightning Testing to DO-160F Indirect Lightning Testing

Section 22 was restructured with additional test requirements moved from notes under figures to the main body of the document, and paragraphs were numbered to provide easy reference to the requirements contained in each paragraph. In the waveform set tables and the test level tables, both the voltage and the current waveform number are now shown to eliminate any ambiguities with how waveforms are related to each other. This section was modified to clarify when a test was successfully completed and when, in the case of reaching a limiting level before a test level, another waveform test was needed.  The cable bundle section now contains a path to follow for every waveform set and criteria for acceptable and unacceptable test limit waveforms that leads the user to successful test completion regardless of the configuration of the cable under test.

Changes from DO-160F Indirect Lightning Testing to DO-160G Indirect Lightning Testing

The most significant change to Section 22 in DO-160G is the addition of a User’s Guide (UG) as an appendix to Section 22.  This appendix removes guidance material from the requirements portion of the section.  This allows for an in-depth discussion on relevant topics without “muddying” the procedures and test level definitions contained in the requirements portion of Section 22.  The UG format is a paragraph by paragraph match with the requirements section for easy references to guidance on specific topics. Where no guidance material was added, the UG paragraph is not populated.  It is expected that the UG will assist equipment designers with design and test considerations as well as improve standardization of testing between test facilities. For example, by providing a detailed discussion on dealing with noise during waveform measurements, labs are more likely to use the same methodology for making measurements, resulting in much more consistency across the industry. The DO-160G Section 22 requirements portion adds the test methods and test levels for performing Waveform 6 Multiple Burst testing.  Voltage limits for Waveform 6 are based on the open circuit voltage level from Waveform3 Pin Injection, as Waveform 6, by definition, does not have a voltage limit.  The Waveform 6 Multiple Burst test resulted in the addition of another waveform set character to identify the waveform used for Multiple Burst testing.  Wave form set ‘L’ is used to identify Waveform3 Multiple Burst and waveform set ‘M’ identifies Waveform 6 Multiple Burst. Due to potential inconsistencies between the two Pin Injection test calibration methods, the resistor method was removed.  The open circuit voltage/short circuit current method is considered the preferred method. As a result of the method elimination, several test setup diagrams were updated to reflect the change. Clarification was added for the use of the ‘Z’ designator when the wave form generator is switched because the generator used did not produce a compliant ‘limit’ waveform.  It is now specified that switching generators requires that the waveform set designation be a ‘Z’, the only exception being where this is done for power line testing only.  Testing of the power line separate from a standard interconnect bundle is the most common way of testing, therefore the exception is allowed providing better representation of the waveform set used for testing on the EUT interconnect bundle.