[DoD seal omitted]

F O R E W O R D

1. This Military Standard is approved for use by all Departments and Agencies of the Department of Defense.

2. This standard is in compliance with the Acquisition Reform Initiatives of Dr. William Perry's memo dated 29 June 1995 (see 6.8).

3. This standard contains two sections, the main body and an appendix. The main body of the standard specifies a baseline set of requirements. The appendix portion provides rationale, guidance, and lessons learned for each requirement to enable the procuring activity to tailor the baseline requirements for a particular application. The appendix also permits government and industry personnel to understand the purpose of the requirements and potential verification methodology for a design. The appendix is not a mandatory part of this document.

4. A joint committee consisting of representatives of the Army, Navy, Air Force, other DoD Agencies, and industry participated in the preparation of this standard.

5. Comments and data which may be of use in improving this document should be addressed to: USAF/Aeronautical Systems Center, ASC/ENSI, 2530 Loop Road West, Wright-Patterson AFB, OH 45433-7101, by using the Standardization Document Improvement Proposal (DD Form 1426) appearing at the end of this document or by letter.

CONTENTS

FOREWORD  ii

1. SCOPE 1

1.1 Purpose 1

1.2 Application 1

2. APPLICABLE DOCUMENTS 1

2.1 General 1

2.2 Government documents 1

2.2.1 Specifications, standards, and handbooks 1

2.2.2 Other Government documents, drawings, and publications 1

2.3 Non-Government publications 2

2.4 Order of precedence 2

3. DEFINITIONS 3

3.1 Acronyms used in this standard 3

3.2 General 3

4. GENERAL REQUIREMENTS 5

4.1 General 5

5. DETAILED REQUIREMENTS 5

5.1 Margins 5

5.2 Intra-system electromagnetic compatibility (EMC) 6

5.2.1 Hull generated intermodulation interference (IMI) 6

5.2.2 Shipboard internal electromagnetic environment (EME) 6

5.2.3 Powerline transients 6

5.2.4 Multipaction 6

5.3 Inter-system EMC 6

5.4 Lightning 8

5.5 Electromagnetic pulse (EMP) 9

5.6 Subsystems and equipment electromagnetic interference (EMI) 11

5.6.1 Non-developmental items (NDI) and commercial items 11

5.6.2 EM spectrum compatibility 11

5.6.3 Shipboard DC magnetic field environment 11

5.7 Electrostatic charge control 11

5.7.1 Vertical lift and in-flight refueling 11

5.7.2 Precipitation static (p-static) 11

5.7.3 Ordnance subsystems 11

5.8 Electromagnetic radiation hazards (EMRADHAZ) 12

5.8.1 Hazards of electromagnetic radiation to personnel (HERP) 12

5.8.2 Hazards of electromagnetic radiation to fuel (HERF) 12

5.8.3 Hazards of electromagnetic radiation to ordnance (HERO) 12

5.9 Life cycle, E3 hardness 12 5.10 Electrical bonding 12

5.10.1 Power current return path 12

5.10.2 Antennas installations 12

5.10.3 Electromagnetic interference (EMI) 13

5.10.4 Shock and fault protection 13

5.11 External grounds 13

5.11.1 Aircraft grounding jacks 13

5.11.2 Servicing and maintenance equipment grounds 13

5.12 TEMPEST 14

5.13 Emission control (EMCON) 14

5.14 Electronic protection (EP) 14

6. NOTES 14

6.1 Intended use 14

6.2 Issue of DoDISS 14

6.3 Associated Data Item Descriptions (DIDs) 14

6.4 Tailoring guidance 15

6.5 Supersession 15

6.6 Subject term (key word) listing 15

6.7 International standardization agreements 15

6.8 Tiering 16

6.9 Technical points of contact 16

TABLES

IA External EME for systems capable of shipboard operations 7

(including topside equipment and aircraft operating from ships) and ordnance

IB External EME for space and launch vehicle systems 7

IC External EME for ground systems 7

ID Baseline external EME for all other applications 8

IIA Lightning indirect effects waveform parameters 8

IIB Electromagnetic fields from near strike lightning (cloud-to-ground) 9

FIGURES

1 Lightning direct effects environment 9

2 Lightning indirect effects environment 10

3 Default free-field EMP environment 10

APPENDIX

A MIL-STD-464 Application Guide 17

CONCLUDING MATERIAL 111

1. SCOPE

1.1 Purpose. This standard establishes electromagnetic environmental effects (E3) interface requirements and verification criteria for airborne, sea, space, and ground systems, including associated ordnance.

1.2 Application. This standard is applicable for complete systems, both new and modified.

2. APPLICABLE DOCUMENTS

2.1 General. The documents listed in this section are referenced in sections 3, 4, and 5 of this standard. This section does not include documents cited in other sections of this standard or recommended for additional information or as examples. While every effort has been made to ensure the completeness of this list, document users are cautioned that they must meet all specified requirements documents cited in Section 4 and 5 of this standard, whether or not they are listed.

2.2 Government documents

2.2.1 Specifications, standards, and handbooks. The following specifications, standards, and handbooks form a part of this document to the extent specified herein. Unless otherwise specified, the issues of these documents are those listed in the issue of the Department of Defense Index of Specifications and Standards (DoDISS) and supplement thereto, cited in the solicitation (see 6.2).

STANDARDS

Department of Defense

MIL-STD-331 Fuze and Fuze Components, Environmental and Performance Tests for

MIL-STD-461 Requirements for the Control of Electromagnetic Interference Emissions and Susceptibility

MIL-STD-462 Measurement of Electromagnetic Interference Characteristics

MIL-STD-1399-070 Interface Standard for Shipboard Systems, D.C. Magnetic Field Environment

(Unless otherwise indicated, copies of federal and military specifications, standards, and handbooks are available from the Standardization Documents Order Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094.)

2.2.2 Other Government documents, drawings, and publications. The following other Government documents, drawings, and publications form a part of this document to the extent specified herein. Unless otherwise specified, the issues are those cited in the solicitation.

PUBLICATIONS

DoDD 4650.1 Management and Use of the Radio Frequency Spectrum

DoDI 6055.11 Protection of DoD Personnel from Exposure to Radio Frequency Radiation and Military Exempt Lasers

NACSEM 5112 NONSTOP Evaluation Techniques

NSTISSAM TEMPEST/1-92 Compromising Emanations Laboratory Test Requirements, Electromagnetics

NTIA Manual of Regulations and Procedures for Federal Radio Frequency Management

(Copies of NTIA Manual are available from the U.S. Government Printing Office, Superintendent of Documents, P.O. Box 371954, Pittsburgh, PA 15250-7954. Copies of DoD documents are available from the Standardization Documents Order Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094. Copies of NACSEM and NSTISSAM documents are available only through the procuring activity.)

2.3 Non-Government publications. The following documents form a part of this document to the extent specified herein. Unless otherwise specified, the issues of the documents which are DoD adopted are those listed in the issue of the DoDISS cited in the solicitation. Unless otherwise specified, the issues of documents not listed in the DoDISS are the issues of the documents cited in the solicitation (see 6.2).

AMERICAN NATIONAL STANDARDS INSTITUTE

ANSI C63.14 Standard Dictionary for Technologies of Electromagnetic Compatibility (EMC), Electromagnetic Pulse (EMP), and Electrostatic Discharge (ESD)

(Application for copies should be addressed to the IEEE Service Center, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331.)

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION

ISO 46 Aircraft - Fuel Nozzle Grounding Plugs and Sockets

(Application for copies should be addressed to ISO, International Organization for Standardization, 3 rue de Varembe, 1211 Geneve 20, Geneve, Switzerland; Phone: 41 22 734 0150).

2.4 Order of precedence. In the event of a conflict between the text of this document and the references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained.

3. DEFINITIONS

3.1 Acronyms used in this standard. The acronyms used in this standard are defined as follows.

E³ electromagnetic environmental effects

EID electrically initiated device

EMC electromagnetic compatibility

EMCON emission control

EME electromagnetic environment

EMI electromagnetic interference

EMP electromagnetic pulse

EMRADHAZ electromagnetic radiation hazards

EP electronic protection

HERF hazards of electromagnetic radiation to fuel

HERO hazards of electromagnetic radiation to ordnance

HERP hazards of electromagnetic radiation to personnel

IMI intermodulation interference

ISO International Standards Organization

MNFS maximum no-fire stimulus

NDI non-developmental item

p-static precipitation static

RF radio frequency

rms root-mean-square

3.2 General. The terms used in this standard are defined in ANSI Standard C63.14. In addition, the following definitions are applicable for the purpose of this standard.

a. Above deck. An area on ships which is not considered to be below deck as defined herein.

b. Below deck. An area on ships which is surrounded by a metallic structure or an area which provides an equivalent attenuation to electromagnetic radiation, such as the metal hull or superstructure of a surface ship, the hull of a submarine and the screened rooms in non-metallic ships.

c. Compromising emanations. Unintentional intelligence-bearing signals which, if intercepted and analyzed, disclose the national security information transmitted, received, handled, or otherwise processed by any classified information processing system.

d. Electrically initiated device. Any component activated through electrical means and having an explosive, pyrotechnic, or a mechanical output resulting from an explosive or pyrotechnic action, and electrothermal devices having a dynamic mechanical, thermal, or electromagnetic output. Examples include bridgewire electroexplosive devices, conductive composition electric primers, semiconductor bridge electroexplosive devices, laser initiators, exploding foil initiators, slapper detonators, burn wires, and fusible links.

e. Electromagnetic environmental effects. The impact of the electromagnetic environment upon the operational capability of military forces, equipment, systems, and platforms. It encompasses all electromagnetic disciplines, including electromagnetic compatibility; electromagnetic interference; electromagnetic vulnerability; electromagnetic pulse; electronic protection; hazards of electromagnetic radiation to personnel, ordnance, and volatile materials; and natural phenomena effects of lightning and p-static.

f. Launch vehicle. A composite of the initial stages, injection stages, space vehicle adapter, and fairing having the capability of launching and injecting a space vehicle or vehicles into orbit.

g. Lightning direct effects. Any physical damage to the system structure and electrical or electronic equipment due to the direct attachment of the lightning channel and current flow. These effects include puncture, tearing, bending, burning, vaporization, or blasting of hardware.

h. Lightning indirect effects. Electrical transients induced by lightning due to coupling of electromagnetic fields.

i. Margins. The difference between the subsystem and equipment electromagnetic strength level, and the subsystem and equipment stress level caused by electromagnetic coupling at the system level. Margins are normally expressed as a ratio in decibels (dB).

j. Maximum no-fire stimulus. The greatest firing stimulus which does not cause initiation within five minutes of more than 0.1% of all electric initiators of a given design at a confidence level of 95%. When determining maximum no-fire stimulus for electric initiators with a delay element or with a response time of more than five minutes, the firing stimulus shall be applied for the time normally required for actuation.

k. Mission critical. Unless otherwise defined in the procurement specification, a term applied to a condition, event, operation, process, or item which if performed improperly, may: 1) prohibit execution of a mission; 2) significantly reduce the operational capability; or 3) significantly increase system vulnerability.

l. Multipaction. Multipaction is an RF effect that occurs only in a high vacuum where RF field accelerates free electrons resulting in collisions with surfaces creating secondary electrons that are accelerated resulting in more electrons and ultimately a major discharge and possible equipment damage.

m. Non-developmental item. Non-developmental item is a broad, generic term that covers material, both hardware and software, available from a wide variety of sources with little or no development effort required by the Government.

n. Ordnance. An explosive or pyrotechnic component or subsystem of an airborne, sea, space, or ground system.

o. Safety critical. Unless otherwise defined in the procurement specification, a term applied to a condition, event, operation, process, or item whose proper recognition, control, performance or tolerance is essential to safe system operation or use; for example, safety critical function, safety critical path, or safety critical component.

p. Space vehicle. A complete, integrated set of subsystems and components capable of supporting an operational role in space. A space vehicle may be an orbiting vehicle, a major portion of an orbiting vehicle, or a payload of an orbiting vehicle which performs it mission while attached to a recoverable launch vehicle. The airborne support equipment which is peculiar to programs utilizing a recoverable launch vehicle is considered a part of the space vehicle being carried by the launch vehicle.

q. System operational performance. A set of minimal acceptable parameters tailored to the platform and reflecting top level capabilities such as range, probability of kill, probability of survival, operational availability, and so forth.

r. TEMPEST. An unclassified, short name referring to the investigation and study of compromising emanations.

4. GENERAL REQUIREMENTS

4.1 General. The system shall be electromagnetically compatible among all subsystems and equipment within the system and with environments caused by electromagnetic effects external to the system. Verification shall be accomplished as specified herein on production representative systems. Safety critical functions shall be verified to be electromagnetically compatible within the system and with external environments prior to use in those environments. Verification shall address all life cycle aspects of the system, including (as applicable) normal in-service operation, checkout, storage, transportation, handling, packaging, loading, unloading, launch, and the normal operating procedures associated with each aspect.

5. DETAILED REQUIREMENTS

5.1 Margins. Margins shall be provided based on system operational performance requirements, tolerances in system hardware, and uncertainties involved in verification of system-level design requirements. Safety critical and mission critical system functions shall have a margin of at least 6 dB. Ordnance shall have a margin of at least 16.5 dB of maximum no-fire stimulus (MNFS) for safety assurances and 6 dB of MNFS for other applications. Compliance shall be verified by test, analysis, or a combination thereof. Instrumentation installed in system components during testing for margins shall capture the maximum system response and shall not adversely affect the normal response characteristics of the component. When environment simulations below specified levels are used, instrumentation responses may be extrapolated to the full environment for components with linear responses (such as hot bridgewire EIDs). When the response is below instrumentation sensitivity, the instrumentation sensitivity shall be used as the basis for extrapolation. For components with non-linear responses (such as semiconductor bridge EIDs), no extrapolation is permitted.

5.2 Intra-system electromagnetic compatibility (EMC). The system shall be electromagnetically compatible within itself such that system operational performance requirements are met. Compliance shall be verified by system-level test, analysis, or a combination thereof.

5.2.1 Hull generated intermodulation interference (IMI). For surface ship applications, the above requirement is considered to be met when the 19th product order and higher of IMI generated by High Frequency (HF) transmitters installed onboard ship are not detectable by antenna-connected receivers onboard ship. Compliance shall be verified by test, analysis, or a combination thereof, through measurement of received levels at system antennas and evaluation of the potential of these levels to degrade receivers.

5.2.2 Shipboard internal electromagnetic environment (EME). For ship applications, electric fields (peak V/m-rms) below deck from intentional onboard transmitters shall not exceed the following levels:

a. Surface ships.

(1). Metallic: 10 V/m from 10 kHz to 18 GHz.

(2). Non-metallic: 10 V/m from 10 kHz to 2 MHz, 50 V/m from 2 MHz to 1 GHz, and 10 V/m from 1 GHz to 18 GHz.

b. Submarines. 5 V/m from 10 kHz to 1 GHz.

Compliance shall be verified by test of electric fields generated below deck with all antennas (above and below decks) radiating.

5.2.3 Powerline transients. For Navy aircraft and Army aircraft applications, electrical transients of less than 50 microseconds in duration shall not exceed +50 percent or -150 percent of the nominal DC voltage or +50 percent of the nominal AC line-to-neutral rms voltage. Compliance shall be verified by test.

5.2.4 Multipaction. For space applications, equipment and subsystems shall be free of multipaction effects. Compliance shall be verified by test and analysis.

5.3 Inter-system EMC. The system shall be electromagnetically compatible with its defined external EME such that its system operational performance requirements are met. For systems capable of shipboard operation, Table IA shall be used. For space and launch vehicle systems applications, Table IB shall be used. For ground systems, Table IC shall be used. For all other applications and if the procuring activity has not defined the EME, Table ID shall be used. Inter-system EMC covers compatibility with, but is not limited to, EME's from like platforms (such as aircraft in formation flying, ship with escort ships, and shelter-to-shelter in ground systems), friendly emitters and hostile emitters. Compliance shall be verified by system, subsystem, and equipment level tests; analysis; or a combination thereof.

TABLE IA. External EME for systems capable of shipboard operations (including topside equipment and aircraft operating from ships) and ordnance

TABLE IB. External EME for space and launch vehicle systems

TABLE IC. External EME for ground systems

TABLE ID. Baseline external EME for all other applications

5.4 Lightning. The system shall meet its operational performance requirements for both direct and indirect effects of lightning. Ordnance shall meet its operational performance requirements after experiencing a near strike in an exposed condition and a direct strike in a stored condition. Ordnance shall remain safe during and after experiencing a direct strike in an exposed condition. Figure 1 shall be used for the direct effects lightning environment. Figure 2 and Table IIA shall be used for the indirect effects lightning environment from a direct strike. Table IIB shall be used for the near lightning strike environment. Compliance shall be verified by system, subsystem, equipment, and component (such as structural coupons and radomes) level tests, analysis, or a combination thereof.

TABLE IIA. Lightning indirect effects waveform parameters

Current Component	Description	i(t) = Io (e-at - e-bt) t is time in seconds (s)
		Io (Amperes)	a (s-1)	b (s-1)
A	Severe stroke	218,810	11,354	647,265
B	Intermediate current	11,300	700	2,000
C	Continuing current	400 for 0.5 s	Not applicable	Not applicable
D	Restrike	109,405	22,708	1,294,530
D/2	Multiple stroke	54,703	22,708	1,294,530
H	Multiple burst	10,572	187,191	19,105,100

TABLE IIB. Electromagnetic fields from near strike lightning (cloud-to-ground)

FIGURE 1. Lightning direct effects environment

5.5 Electromagnetic pulse (EMP). The system shall meet its operational performance requirements after being subjected to the EMP environment. If an EMP environment is not defined by the procuring activity, Figure 3 shall be used. This requirement is not applicable unless otherwise specified by the procuring activity. Compliance shall be verified by system, subsystem, and equipment level tests, analysis, or a combination thereof.

FIGURE 2. Lightning indirect effects environment

FIGURE 3. Default free-field EMP environment

5.6 Subsystems and equipment electromagnetic interference (EMI). Individual subsystems and equipment shall meet interference control requirements (such as the conducted emissions, radiated emissions, conducted susceptibility, and radiated susceptibility requirements of MIL-STD-461) so that the overall system complies with all applicable requirements of this standard. Compliance shall be verified by tests that are consistent with the individual requirement (such as testing to MIL-STD-462 to verify MIL-STD-461 requirements).

5.6.1 Non-developmental items (NDI) and commercial items. NDI and commercial items shall meet EMI interface control requirements suitable for ensuring that system operational performance requirements are met. Compliance shall be verified by test, analysis, or a combination thereof.

5.6.2 EM spectrum compatibility. Subsystems and equipment shall comply with the DoD, national, and international regulations for the use of the electromagnetic spectrum (such as NTIA "Manual of Regulations and Procedures for Radio Frequency Management" and DoDD 4650.1). Compliance shall be verified by test, analysis, or a combination thereof, as appropriate for the equipment development stage.

5.6.3. Shipboard DC magnetic field environment. Subsystems and equipment used aboard ships shall not be degraded when exposed to its operational DC magnetic environment (such as MIL-STD-1399, Section 070). Compliance shall be verified by test.

5.7 Electrostatic charge control. The system shall control and dissipate the build-up of electrostatic charges caused by precipitation static (p-static) effects, fluid flow, air flow, space and launch vehicle charging, and other charge generating mechanisms to avoid fuel ignition and ordnance hazards, to protect personnel from shock hazards, and to prevent performance degradation or damage to electronics. Compliance shall be verified by test, analysis, inspections, or a combination thereof.

5.7.1 Vertical lift and in-flight refueling. The system shall meet its operational performance requirements when subjected to a 300 kilovolt discharge. This requirement is applicable to vertical lift aircraft, in-flight refueling of any aircraft, and systems operated or transported externally by vertical lift aircraft. Compliance shall be verified by test (such as MIL-STD-331 for ordnance), analysis, inspections, or a combination thereof. The test configuration shall include electrostatic discharge in the vertical lift mode and in-flight refueling mode from a simulated aircraft capacitance of 1000 picofarads, through a maximum of one ohm resistance.

5.7.2 Precipitation static (p-static). The system shall control p-static interference to antenna-connected receivers onboard the system or on the host platform such that system operational performance requirements are met. Compliance shall be verified by test, analysis, inspections, or a combination thereof. For Navy aircraft and Army aircraft applications, p-static protection shall be verified by testing that applies charging levels representative of conditions in the operational environment.

5.7.3 Ordnance subsystems. Ordnance subsystems shall not be inadvertently initiated or dudded by a 25 kilovolt electrostatic discharge caused by personnel handling. Compliance shall be verified by test (such as MIL-STD-331), discharging a 500 picofarad capacitor through a 500 ohm resistor to the ordnance subsystem (such as electrical interfaces, enclosures, and handling points.

5.8 Electromagnetic radiation hazards (EMRADHAZ). The system design shall protect personnel, fuels, and ordnance from hazardous effects of electromagnetic radiation. Compliance shall be verified by test, analysis, inspections, or a combination thereof.

5.8.1 Hazards of Electromagnetic Radiation to Personnel (HERP). The system shall comply with current national criteria for the protection of personnel against the effect of electromagnetic radiation. DoD policy is currently found in DoDI 6055.11. Compliance shall be verified by test, analysis, or combination thereof.

5.8.2 Hazards of electromagnetic radiation to fuel (HERF). Fuels shall not be inadvertently ignited by radiated EMEs. The EME includes onboard emitters and the external EME (see 5.3). Compliance shall be verified by test, analysis, inspection, or a combination thereof.

5.8.3 Hazards of electromagnetic radiation to ordnance (HERO). Ordnance with electrically initiated devices (EIDs) shall not be inadvertently ignited during, or experience degraded performance characteristics after, exposure to the external radiated EME of Table IA for either direct RF induced actuation or coupling to the associated firing circuits. Compliance shall be verified by system, subsystem, and equipment level tests and analysis. For EME's in the HF band derived from near field conditions, verification by test shall use transmitting antennas representative of the types present in the installation.

5.9 Life cycle, E3 hardness. The system operational performance and E³ requirements of this standard shall be met throughout the rated life cycle of the system and shall include, but not be limited to, the following: maintenance, repair, surveillance, and corrosion control. Compliance shall be verified by test, analysis, inspections, or a combination thereof, of system design features. Maintainability, accessibility, and testability, and the ability to detect degradations shall be demonstrated.

5.10 Electrical bonding. The system, subsystems, and equipment shall include the necessary electrical bonding to meet the E³ requirements of this standard. Compliance shall be verified by test, analysis, inspections, or a combination thereof, for the particular bonding provision.

5.10.1 Power current return path. For systems using structure for power return currents, bonding provisions shall be provided for current return paths for the electrical power sources such that the total voltage drops between the point of regulation for the power system and the electrical loads are within the tolerances of the applicable power quality standard. Compliance shall be verified by analysis of electrical current paths, electrical current levels, and bonding impedance control levels.

5.10.2 Antenna installations. Antennas shall be bonded to obtain required antenna patterns and meet the performance requirements for the antenna. Compliance shall be verified by test, analysis, inspections, or a combination thereof.

5.10.3 Electromagnetic interference (EMI). The system electrical bonding shall provide electrical continuity across external mechanical interfaces on electrical and electronic equipment, both within the equipment and between the equipment and system structure, for control of E³ such that the system operational performance requirements are met. For Navy aircraft and Army aircraft applications, the EMI bonds shall have an interface direct current (DC) resistance of 2.5 milliohms or less for each faying interface between the subsystem or equipment enclosure and the system ground reference. Compliance shall be verified by test, analysis, inspections, or a combination thereof.

5.10.4 Shock and fault protection. Bonding of all exposed electrically conductive items subject to fault condition potentials shall be provided to control shock hazard voltages and allow proper operation of circuit protection devices. Compliance shall be verified by test, analysis, or a combination thereof.

5.11 External grounds. The system and associated subsystems shall provide external grounding provisions to control electrical current flow and static charging for protection of personnel from shock, prevention of inadvertent ignition of ordnance, fuel and flammable vapors, and protection of hardware from damage. Compliance shall be verified by test, analysis, inspections, or a combination thereof.

5.11.1 Aircraft grounding jacks. Grounding jacks shall be attached to the system to permit connection of grounding cables for fueling, stores management, servicing, maintenance operations and while parked. ISO 46 contains requirements for interface compatibility. Grounding jacks shall be attached to the system ground reference so that the resistance between the mating plug and the system ground reference does not exceed 1.0 ohm DC. The following grounding jacks are required:

a. Fuel nozzle ground. A ground jack shall be installed at each fuel inlet. To satisfy international agreements for interfacing with refueling hardware, the jack shall be located within 1.0 meter of the center of the fuel inlet for fuel nozzle grounding.

b. Servicing grounds. Ground jacks shall be installed at locations convenient for servicing and maintenance. For Navy and Army aircraft applications, a minimum of two grounding jacks shall be required for utility and helicopter aircraft and a minimum of four grounding jacks shall be required for other types of aircraft, in addition to those required for fueling or weapons loading or downloading.

c. Weapon grounds. Grounding jacks shall be installed at locations convenient for use in handling of weapons or other explosive devices.

Compliance shall be verified by test and inspections.

5.11.2 Servicing and maintenance equipment grounds. Servicing and maintenance equipment shall have a permanently attached grounding wire suitable for connection to earth ground. All servicing equipment that handles or processes flammable fuels, fluids, explosives, oxygen, or other potentially hazardous materials shall have a permanently attached grounding wire for connection to the system. Compliance shall be verified by inspection.

5.12 TEMPEST. National security information shall not be compromised by emanations from classified information processing equipment. Compliance shall be verified by test, analysis, inspections or a combination thereof. ( NSTISSAM TEMPEST/1-92 and NACSEM 5112 provide testing methodology for verifying compliance with TEMPEST requirements.)

5.13 Emission control (EMCON). For Army applications, Navy applications, and other systems applications capable of shipboard operation, unintentional electromagnetic radiated emissions shall not exceed -110 dBm/m² at one nautical mile (-105 dBm/m² at one kilometer) in any direction from the system over the frequency range of 500 kHz to 40 GHz. Unless otherwise specified by the procuring activity, EMCON shall be activated by a single control function for aircraft. Compliance shall be verified by test and inspection.

5.14 Electronic protection (EP). For Army aircraft and Navy aircraft applications, intentional and unintentional electromagnetic radiated emissions in excess of the EMCON limits shall preclude the classification and identification of the system such that system operational performance requirements are met. Unless otherwise specified by the procuring activity, EP shall be activated by a single control function. Compliance shall be verified by test, analysis, inspections, or a combination thereof.

6. NOTES

(This section contains information of a general or explanatory nature that may be helpful, but is not mandatory.)

6.1 Intended use. This standard contains electromagnetic environmental effects requirements for systems.

6.2 Issue of DoDISS. When this standard is used in acquisition, the applicable issue of the DoDISS must be cited in the solicitation (see 2.2.1 and 2.3).

6.3 Associated Data Item Descriptions (DIDs). This standard is cited in DoD 5010.12-L, Acquisition Management Systems and Data Requirements Control List (AMSDL), as the source document for the following DIDs. When it is necessary to obtain the data, the applicable DIDs must be listed on the Contract Data Requirements List (DD Form 1423), except where the DoD Federal Acquisition Regulation Supplement exempts the requirement for a DD Form 1423.

The above DIDs were current as of the date of this standard. The current issue of the AMSDL must be researched to ensure that only current and approved DIDs are cited on the DD Form 1423.

6.4 Tailoring guidance. Application specific criteria may be derived from operational and engineering analyses on the system being procured for use in specific environments. When analyses reveal that a requirement in this standard is not appropriate or adequate for that procurement, the requirement should be tailored and incorporated into the appropriate documentation. The appendix of this standard provides guidance for tailoring.

6.5 Supersession. The following documents have been superseded by this standard:

MIL-STD-1818A (4 October 1993)

MIL-E-6051D (7 September 1967)

MIL-B-5087B (15 October 1964)

MIL-STD-1385B (6 August 1986)

6.6 Subject term (key word) listing.

E3

Electrical bonding

EMC

EMCON

EMI

EMP

EP

Electromagnetic compatibility

Electromagnetic environment

Electromagnetic emission

Electromagnetic interference

Electromagnetic radiation hazards

Electromagnetic susceptibility

Electronic protection

Grounding

HERF

HERO

HERP

Inter-system electromagnetic compatibility

Intra-system electromagnetic compatibility

Lightning

Multipaction

RADHAZ

System

TEMPEST

6.7 International standardization agreements. Certain provisions of this standard may be the subject of international standardization agreements. When amendment, revision, or cancellation of this standard is proposed which will modify the international agreement concerned, the preparing activity will take appropriate action through international standardization channels, including departmental standardization offices to change the agreement or make other appropriate accommodation.

6.8 Tiering. The standard is constructed to account for new DoD requirements that only first tier references are contractually binding. Each requirement paragraph begins with at least one stand-alone performance statement which does not reference other documents. Follow-on wording will sometimes reference an appropriate document which is the source of the requirement or contains additional information. The requirements of this standard can be implemented in different ways. The standard can be directly referenced in a procurement specification for a system as a source of E³ requirements. The standard then becomes a first tier reference. Each requirement should be reviewed for applicability and possible need for tailoring. An alternate approach is to extract appropriate paragraphs from the standard, tailor them as necessary, and insert them directly into the procurement specification. Under this approach, direct reference can be made to other documents, including the text of this standard. These references are then first tier and become contractual.

6.9 Technical points of contact. Requests for additional information or assistance on this standard can be obtained from the following:

Air Force
ASC/ENA, Bldg. 560
2530 Loop Road West
Wright Patterson AFB, OH 45433-7101
DSN 785-5078, Commercial (937) 255-5078

Army
Director, AMSAA
AMXSY-RE
APG, MD 21005-5071
DSN 298-6994, Commercial (410) 278-6994

Navy
Commander, Naval Air Systems Command
NAVAIR 4.1.7
Arlington, VA 22243-5120
DSN 664-6060, Ext. 5651, Commercial (703) 604-6060, Ext. 5651

Any information relating to Government contracts must be obtained through contracting officers.

APPENDIX

MIL-STD-464
APPLICATION GUIDE

CONTENTS

A1. SCOPE 20

A1.1 Scope 20

A2. APPLICABLE DOCUMENTS 20

A2.1 Government documents 20

A2.1.1 Specifications, standards, and handbooks 20

A2.1.2 Other Government documents, drawings, and publications 21

A2.2 Non-Government publications 23

A3. ACRONYMS 24

A4. REQUIREMENTS AND VERIFICATION 25

A4.1 General 26

A5. DETAILED REQUIREMENTS 30

A5.1 Margins 30

A5.2 Intra-system electromagnetic compatibility (EMC) 33

A5.2.1 Hull generated intermodulation interference (IMI) 38

A5.2.2 Shipboard internal electromagnetic environment (EME) 39

A5.2.3 Powerline transients 40

A5.2.4 Multipaction 41

A5.3 Inter-system EMC 42

A5.4 Lightning 52

A5.5 Electromagnetic pulse (EMP) 59

A5.6 Subsystems and equipment electromagnetic interference (EMI) 64

A5.6.1 Non-developmental items (NDI) and commercial items 66

A5.6.2 EM spectrum compatibility 69

A5.6.3 Shipboard DC magnetic field environment 72

A5.7 Electrostatic charge control 73

A5.7.1 Vertical lift and in-flight refueling 75

A5.7.2 Precipitation static (P-static) 76

A5.7.3 Ordnance subsystems 78

A5.8 Electromagnetic radiation hazards (EMRADHAZ) 79

A5.8.1 Hazards of electromagnetic radiation to personnel (HERP) 80

A5.8.2 Hazards of electromagnetic radiation to fuel (HERF) 81

A5.8.3 Hazards of electromagnetic radiation to ordnance (HERO) 82

A5.9 Life cycle, E3 hardness 87

A5.10 Electrical bonding 91

A5.10.1 Power current return path 95

A5.10.2 Antennas installations 96

A5.10.3 Electromagnetic interference (EMI) 97

A5.10.4 Shock and fault protection 99

A5.11 External grounds 100

A5.11.1 Aircraft grounding jacks 103

A5.11.2 Servicing and maintenance equipment grounds 104

A5.12 TEMPEST 105

A5.13 Emission control (EMCON) 106

A5.14 Electronic protection (EP) 109

TABLES

Table IA External EME for systems capable of shipboard operations (including topside equipment and aircraft operating from ships) and ordnance 42

Table IB External EME for space and launch vehicle systems 43

Table IC External EME for ground systems 43

Table ID Baseline external EME for all other applications 43

Table IIA Lighting indirect effects waveform parameters 53

Table IIB Electromagnetic fields from near strike lightning (cloud-to-ground) 53

Table AI Lightning indirect effects waveform characteristics 55

Table AII Recommended number of test frequencies 85

FIGURES

Figure 1 Lighting direct effects environment 52

Figure 2 Lighting indirect effects environment 53

Figure A1 Lightning indirect effects waveform parameters 55

Figure 3 Default free-field EMP environment 59

Figure A2 EMP environment (E1, E2, and E3) 60

A1 SCOPE

A1.1 Scope. This appendix provides background information for each requirement in the main body of the standard. The information includes rationale for each requirement, guidance on applying the requirement, and lessons learned related to the requirement. This information should help users understand the intent behind the requirements and adapt them as necessary for a particular application.

A2 APPLICABLE DOCUMENTS

A2.1 Government documents

A2.1.1 Specifications, standards, and handbooks. The following specifications, standards, and handbooks are referenced in this appendix and form a part of this document to the extent specified herein.

SPECIFICATIONS

Military

MIL-I-23659 Initiator, Electric, General Design Specification

MIL-C-83413 Connectors and Assemblies, Electrical, Aircraft Grounding, General

MIL-W-83575 Wiring Harness, Space Vehicle, Design and Testing

STANDARDS

Military

MIL-STD-188-124 Grounding, Bonding and Shielding for Common Long Haul/Tactical Communications Systems Including Ground Based Communication-Electronics Facilities and Equipments

MIL-STD-188-125 High Altitude Electromagnetic Pulse (HEMP) Protection for Ground-Based C⁴I Facilities Performing Critical, Time-Urgent Missions

MIL-STD-331 Fuze and Fuze Components, Environmental and Performance Tests for

MIL-STD-449 Radio Frequency Spectrum Characteristics, Measurement of

MIL-STD-461 Requirements for the Control of Electromagnetic Interference Emissions and Susceptibility

MIL-STD-462 Measurement of Electromagnetic Interference Characteristics

MIL-STD-469 Radar Engineering Design Requirements, Electromagnetic Compatibility

MIL-STD-704 Aircraft Electric Power Characteristics

MIL-STD-1310 Shipboard Bonding, Grounding, and Other Techniques for Electromagnetic Compatibility and Safety

MIL-STD-1399-070 Interface Standard for Shipboard Systems, DC Magnetic Field Environment

MIL-STD-1399-300 Interface Standard for Shipboard Systems, Section 300, Electric Power, Alternating Current

MIL-STD-1542 Electromagnetic Compatibility and Grounding Requirements for Space System Facilities

MIL-STD-1568 Materials and Processes for Corrosion Prevention and Control in Aerospace Weapon Systems

MIL-STD-1576 Electroexplosive Subsystem Safety Requirements and Test Methods for Space Systems

MIL-STD-1605 Procedures for Conducting a Shipboard Electromagnetic Interference (EMI) Survey (Surface Ships)

MIL-STD-1680 (SH) Installation Criteria for Shipboard Secure Electrical Information Processing Systems

MIL-STD-2169 High Altitude Electromagnetic Pulse Environment

HANDBOOKS

MIL-HDBK-235 Electromagnetic (Radiated) Environment Considerations for Design and Procurement of Electrical and Electronic Equipment, Subsystems and Systems

MIL-HDBK-237 Electromagnetic Compatibility Management Guide for Platforms, Systems, and Equipment

MIL-HDBK-419 Grounding, Bonding, and Shielding for Electronic Equipments and Facilities

MIL-HDBK-423 High-Altitude Electromagnetic Pulse (HEMP) Protection for Fixed and Transportable Ground-Based Facilities

MIL-HDBK-454 Electronic Equipment, General Guidelines for

MIL-HDBK-274 Electrical Grounding for Aircraft Grounding

(Unless otherwise indicated, copies of federal and military specifications, standards, and handbooks are available from the Standardization Documents Order Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094. Application for copies of MIL-STD-2169 should be addressed with a need-to-know to: Defense Special Weapons Agency, Electronics Technology Division, 6801 Telegraph Road, Alexandria, VA 22310-3398.)

A2.1.2 Other Government documents, drawings, and publications. The following other Government documents are referenced in this appendix.

Air Force

AFAPL-TR-78-56 Static Electricity Hazards in Aircraft Fuel Systems

AFAPL-TR-78-89 Factors Affecting Electrostatic Hazards

AFWL-TR-85-113 Guidelines for Reducing EMP Induced Stresses in Aircraft LA-5201-MS Response of Airborne Electroexplosive Devices to Electromagnetic Radiation (AD 912 599)

R-3046-AF Techniques for the Analysis of Spectral and Orbital Congestion in Space Systems (DTIC No. ADA140841)

TO 00-25-172 Ground Servicing of Aircraft and Static Grounding/Bonding

TO 31Z-10-4 Electromagnetic Radiation Hazards

Department of Defense (DoD)

DoDI 6055.11 Protection of DoD Personnel from Exposure to Radiofrequency Radiation and Military Exempt Lasers

DoDD 4650.1 Management and Use of the Radio Frequency Spectrum

DoDD 5200.19 Control of Compromising Emanations (Classified)

Federal Aviation Administration (FAA)

AC 20-53 Protection of Aircraft Fuel Systems Against Fuel Vapor Ignition Due to Lightning

AC 20-136 Protection of Aircraft Electrical/Electronic Systems Against the Indirect Effects of Lightning

DOT/FAA/CT-89/2 Aircraft Lightning Handbook

DOT/FAA/CT-86/40 Aircraft Electromagnetic Compatibility

NASA

TP2361 Design Guidelines for Assessing and Controlling Spacecraft Charging Effects

TR 32-1500 Final Report on RF Voltage Breakdown in Coaxial Transmission Lines

Navy

NAWCWPNS Electronic Warfare and Radar Systems Engineering TS 92-78 Handbook

NAVSEA OP 3565/ Electromagnetic Radiation Hazards

NAVAIR 16-1-529/

NAVELEX 0967-

LP-624-6010

OD 30393 Design Principles and Practices for Controlling Hazards of Electromagnetic Radiation to Ordnance (HERO DESIGN GUIDE)

Publications

NACSEM 5112 NONSTOP Evaluation Techniques

NSTISSAM TEMPEST/1-92 Compromising Emanations Laboratory Test Requirements, Electromagnetics

NSTISSAM TEMPEST/1-93 Compromising Emanations Field Test Evaluations

NSTISSAM TEMPEST/2-95 Red/Black Installation Guidelines

NTIA Manual of Regulations and Procedures for Federal Radio Frequency Management

OMB Circular A-11 Preparation and Submission of Budget Estimates

(Copies of FAA publications and military technical reports are available from National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 22161 or the Defense Technical Information Center (DTIC), Bldg. 5, Cameron Station, Alexandria, VA 22304-6145. Air Force Technical Orders are available from Oklahoma City Air Logistics Center (OC-ALC/MMEDT), Tinker AFB, OK 73145-5990. Copies of DoD documents are available from the Standardization Documents Order Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094. Copies of NASA documents are available from NASA Industrial Application Center/USC, 3716 South Hope St. # 200, Los Angeles, CA 90007. Copies of NAVSEA documents available from Commanding Officer, Naval Surface Warfare Center, Port Hueneme Division, Naval Sea Data Support Activity (Code 5700), Department of the Navy, Port Hueneme, CA 93043. Copies of NACSEM, NSTISSAM, and NSA documents are available only through the procuring activity.)

A2.2 Non-Government publications. The following non-Government documents form a part of this standard to the extent specified herein.

International Organization for Standardization

ISO 46 Aircraft - Fuel Nozzle Grounding Plugs and Sockets

(Application for copies should be addressed to ISO, International Organization for Standardization, 3 rue de Varembe, 1211 Geneve 20, Geneve, Switzerland; phone 41 22 734 0150)

Franklin Applied Physics

F-C2560 RF Evaluation of the Single Bridgewire Apollo Standard Initiator

M-C2210-1 Monograph on Computation of RF Hazards

(Application for copies should be addressed to Franklin Applied Physics, P.O. Box 313, Oaks, PA 19456)

National Fire Protection Association (NFPA)

70 National Electrical Code

780 Lightning Protection Code

(Application for copies of the Code should be addressed to the National Fire Protection Association, Batterymarch Park, Quincy, MA 02269-9101.)

North Atlantic Treaty Organization (NATO)

ANEP 45 Electro-Magnetic Compatibility (EMC) in Glass Reinforced Plastic (GRP) Vessels

(Application for copies should be addressed to Central US Registry, The Pentagon, Room 1B889, Washington, DC 20310-3072)

RTCA

DO-160 Environmental Conditions and Test Procedures for Airborne Equipment

(Application for copies of this standard should be addressed to RTCA, 1425 K Street NW, Washington, DC 20005; phone (202) 682-0266.)

Society of Automotive Engineers, Inc.

AE4L-87-3 Protection of Aircraft Electrical/Electronic Systems Against the Indirect Effects of Lightning

ARP 1870 Aerospace Systems Electrical Bonding and Grounding for Electromagnetic Compatibility and Safety

ARP 4242 Electromagnetic Compatibility Control Requirements, Systems

(Application for copies should be addressed to the Society of Automotive Engineers Inc., 400 Commonwealth Drive, Warrendale, PA 15096; phone (412) 776-4841.)

Statistical Research Group

AMP Report Statistical Analysis for a New Procedure in Sensitivity No. 101-1R Experiments (ATI-34558)

SRG-P, No. 40

(Application for copies should be addressed to the Defense Technical Information Center (DTIC), Bldg. 5, Cameron Station, Alexandria, VA 22304-6145)

A3. ACRONYMS.

The acronyms used in this appendix are defined as follows. AAPG antenna inter-antenna propagation with graphics

AGC automatic gain control

AM amplitude modulation

AMITS air management information tracking system

ASEMICAP air systems EMI corrective action program

BIT built-in test

C³I command, control, communications, and intelligence

C⁴I command, control, communications, computers, and intelligence

CTTA certified TEMPEST technical authority

CW continuous wave

E³ electromagnetic environmental effects

ECCM electronic counter counter-measures

ECM electronic counter-measures

EID electrically initiated device

EM electromagnetic

EMC electromagnetic compatibility

EMCON emission control

EME electromagnetic environment

EMI electromagnetic interference

EMP electromagnetic pulse

EMRADHAZ electromagnetic radiation hazards

EMV electromagnetic vulnerability

EP electronic protect

ESD electrostatic discharge

GPS global positioning system

HEMP high altitude electromagnetic pulse

HERF hazards of electromagnetic radiation to fuel

HERO hazards of electromagnetic radiation to ordnance

HERP hazards of electromagnetic radiation to personnel

HIRF high intensity radiated fields

IMI intermodulation interference

MHD magnetohydrodynamic

MNFS maximum no-fire stimulus

NDI non-developmental item

POR point of regulation

p-static precipitation static

RF radio frequency

SEMCIP ship EMC improvement program

TWT traveling wave tube

A4. GENERAL REQUIREMENTS AND VERIFICATION.

In this section, the requirements from the main body are repeated (printed in italics) and are then followed by rationale, guidance, and lessons learned for each interface requirement and rationale, guidance, and lessons learned for each verification requirement. Interface and verification requirement discussions are treated separately because they address different issues. Tables and figures associated with the requirements from the main body are also repeated with their same alphanumeric designations. Tables and figures which are unique to the appendix have alphanumeric designations which are preceded by an "A".

A4.1 General. The system shall be electromagnetically compatible among all subsystems and equipment within the system and with environments caused by electromagnetic effects external to the system. Verification shall be accomplished as specified herein on production representative systems. Safety critical functions shall be verified to be electromagnetically compatible within the system and with external environments prior to use in those environments. Verification shall address all life cycle aspects of the system, including (as applicable) normal in-service operation, checkout, storage, transportation, handling, packaging, loading/unloading, launch, and the normal operating procedures associated with each aspect.

Requirement Rationale (A4.1): The E³ area addresses a number of interfacing issues with environments both external to the system and within the system. External to the system are electromagnetic effects such as lightning, EMP and man-made RF transmissions. Internal to the system are electromagnetic effects such as electronic noise emissions, self-generated RF transmissions from antennas, and cross-coupling of electrical currents. Systems today are complex from a materials usage and electronics standpoint. Many materials being used are non-metallic and have unique electromagnetic properties which require careful consideration. Electronics performing critical functions are common. Wide use of RF transmitters, sensitive receivers, other sensors, and additional electronics creates a potential for problems within the system and from external influences. Increasing use of commercial equipment in unique military operational environments poses special interface considerations. Each system must be compatible with itself, other systems, and external environments to ensure required performance and to prevent costly redesigns for resolution of problems.

Requirement Guidance (A4.1): The system and all associated subsystems and equipment, including ordnance, need to achieve system compatibility. Every effort needs to be made to meet these requirements during initial design rather than on an after-the-fact basis. System E³ Integration and Analysis Reports are used to aid in technical management of programs. These reports describe requirement flowdown from this standard and specific design measures being implemented to meet the requirements of this standard. The other requirements of this standard address specific aspects of the E3 control area. Additional guidance on EMC can be found in MIL-HDBK-237, DOT/FAA/CT-86/40, SAE ARP 4242, and NATO ANEP 45.

An overall integrated EMC design and verification approach for the system must be established. Based on system-level architecture, appropriate hardening requirements are allocated between system design features and subsystems and equipment hardness. Transfer functions from system-level environments to stresses at the subsystem and equipment-level are determined and appropriate electromagnetic interference controls are imposed.

An E3 integration approach can be organized into five activities:

a. Establish the external threat environment against which the system is required to demonstrate compliance of immunity. The external environments (EME, lightning and EMP) to which the system should be designed and verified are addressed in other sections of this appendix.

b. Identify the system electrical and electronic equipment performing functions required for operation during application of the external threat. Normally all functions essential for completing the missions are protected against the external threats.

c. Establish the internal environment caused by external electromagnetic effects for each installed equipment. All of the environments external to the system specified in this standard cause related environments internal to the system. The level of this internal environment will be the result of many factors such as structural details, penetration of apertures and seams, and system and cable resonances. The internal environment for each threat should be established by analysis, similarity to previously tested systems, or testing. The internal environment is usually expressed as the level of electrical current stresses appearing at the interface to the equipment or electromagnetic field quantities. These internal stresses are typically associated with standardized requirements for equipment (for example, MIL-STD-461). Trade-offs need to be made of the degree of hardening to be implemented at the system-level (such as shielded volumes or overbraiding on interconnecting wiring) versus equipment-level (more stringent electromagnetic interference requirements) to establish the most effective approach from performance and cost standpoints.

d. Design the system and equipment protection. System features are then designed as necessary to control the internal environment (including margin considerations) to levels determined from the trade-off studies and appropriate requirements are imposed on the electrical and electronic equipment. The equipment immunity levels must be above the internal environments by necessary margins to account for criticality of the equipment, manufacturing tolerances, and uncertainties in verification. Normally there are design and test requirements in MIL-STD-461 and MIL-STD-462 applicable for each of the external environments, but they may need modification for the particular system application. For example, external environment may result in internal environments above the susceptibility level specified in MIL-STD-461. If so, the limit must be tailored for the particular system, alternative requirements must be imposed or the internal environment must be reduced to an acceptable level. The system E³ design must be viable throughout the system life cycle. This aspect requires an awareness of 1) proper application of corrosion control provisions and 2) issues related to maintenance actions that may affect EMC, such as ensuring electrical bonding provisions are not degraded, maintaining surface treatments in place for E³ control, and considering exposure of electronics to EMEs when access panels are open.

e.Verify the protection adequacy. The system and equipment E3 protection design must be verified as meeting contractual requirements. Verification of the adequacy of the protection design includes demonstrating that the actual levels of the internal environments appearing at the equipment interfaces and enclosures do not exceed the qualification test levels of the equipment for each environment by required margins. All electronic and electrical equipments must have been qualified to their appropriate specification level. Systems-level testing is normally required to minimize the required-margin demonstration. Analysis may be acceptable under some conditions; however, the required margins will typically be larger.

These verification activities need to be documented in detail in verification procedures and verification reports, as applicable. Section 6.3 of the main body provides data item descriptions for documents that are suitable for this purpose.

Requirement Lessons Learned (A4.1): The early implementation of E3 requirements have been instrumental in preventing problems on previous programs. Evolving system designs regarding changing materials and increasing criticality of electronics demand that effective electromagnetic effects controls be implemented.

It is important that all external environments be treated in a single unified approach. Duplication of efforts in different disciplines have occurred in the past. For example, hardening to electromagnetic pulse and lightning-induced transients have been addressed independently rather than as a common threat with different protection measures being implemented for each. This situation is apparently due in part to organizational structures at contractor facilities which place responsibility in different offices for each of the threats.

Verification Rationale (A4.1): Each separate requirement must be verified. The developing activity must demonstrate that the system, subsystem and equipment operate compatibly with the external environments (EME, lightning, and EMP) contained in the system requirements and in accordance with the system contract Statement of Work. The developing activity must also assign verification responsibility to associate contractors for their supplied systems and subsystems to demonstrate compliance with E3 requirements.

Verification Guidance (A4.1): Most of the requirements in this standard are verified at the system-level. Compliance for some requirements is verified at the subsystem, equipment, or component level, such as electromagnetic interference requirements on a subsystem or lightning certification of an airframe component.

The selection of test, analysis, or inspection or some combination to demonstrate a particular requirement is generally dependent on the degree of confidence in the results of the particular method, technical appropriateness, associated costs, and availability of assets. Some of the requirements included in this standard specify the method to be used. For example, verification of subsystem and equipment-level electromagnetic interference requirements must be demonstrated by test, because analysis tools are not available which will produce credible results.

Analysis and testing often supplement each other. Prior to the availability of hardware, analysis will often be the primary tool being used to ensure that the design incorporates adequate provisions. Testing may then be oriented toward validating the accuracy and appropriateness of the models used. If model confidence is high, testing may then be limited. For example, design of an aircraft for protection against EMP or the indirect effects of lightning has to rely heavily on analysis.

E3 requirements need to be verified through an incremental verification process. "Incremental" implies that verification of compliance with E3 requirements is a continuing process of building an argument (audit trail) throughout development that the design satisfies the imposed performance requirements. Initial engineering design must be based on analysis and models. As hardware becomes available, testing of components of the subsystem can be used to validate and supplement the analysis and models. The design evolves as better information is generated. When the system is actually produced, inspection, final testing, and follow-on analysis complete the incremental verification process. It is important to note that testing is often necessary to obtain information that may not be amenable to determination by analysis. However, testing also is often used to determine a few data points with respect to a particular interface requirement with analysis (and associated simulations) filling in the total picture. It should be noted that the guidance sections for individual E3 requirements specified in other sections below generally treat the predominant methods for final verification rather than dealing with the overall philosophy described in this section.

The following list provides guidance on issues which should be addressed for E3 verification:

a. Systems used for verification should be production configuration, preferably the first article.

b. The system should be up-to-date with respect to all approved engineering change proposals (both hardware and software).

c. Electromagnetic interference qualification should be completed on subsystems and equipment.

d. Subsystems and equipment should be placed in modes of operation that will maximize potential indication of interference or susceptibility, consistent with system operational performance requirements.

e. Any external electrical power used for system operation should conform to the power quality standard of the system.

f. Any anomalies found should be evaluated to determine whether they are truly an E3 issue or some other type of malfunction or response.

g. Any system modifications resulting from verification efforts should be validated for effectiveness after they have been engineered.

h. Margins need to be demonstrated wherever they are applicable.

Verification Lessons Learned (A4.1): Historically, failure to adequately verify system performance in an operational EME has resulted in costly delays during system development, mission aborts, and reduced system and equipment operational effectiveness. It is important that assets required for verification of E3 requirements be identified early in the program to ensure their availability when needed.

A5. DETAILED REQUIREMENTS

A5.1 Margins. Margins shall be provided based on system operational performance requirements, tolerances in system hardware, and uncertainties involved in verification of system-level design requirements. Safety critical and mission critical system functions shall have a margin of at least 6 dB. Ordnance shall have a margin of at least 16.5 dB of maximum no-fire stimulus (MNFS) for safety assurances and 6 dB of MNFS for other applications. Compliance shall be verified by test, analysis, or a combination thereof. Instrumentation installed in system components during testing for margins shall capture the maximum system response and shall not adversely affect the normal response characteristics of the component. When environment simulations below specified levels are used, instrumentation responses may be extrapolated to the full environment for components with linear responses (such as hot bridgewire EIDs). When the response is below instrumentation sensitivity, the instrumentation sensitivity shall be used as the basis for extrapolation. For components with non-linear responses (such as semiconductor bridge EIDs), no extrapolation is permitted.

Requirement Rationale (A5.1): Variability exists in system hardware from factors such as differences in cable harness routing and makeup, adequacy of shield terminations, conductivity of finishes on surfaces for electrical bonding, component differences in electronics boxes, and degradation with aging and maintenance. Margins must be included in the design to account for these types of variabilities. In addition, uncertainties are present in the verification process due to the verification method employed, limitations in environment simulation, and accuracy of measured data. The proper application of margins in system and subsystem design provides confidence that all production systems will perform satisfactorily in the operational E3 environments.

Requirement Guidance (A5.1): Margins are generally applicable to all environments external to the system, including lightning (only indirect effects), inter-system EMC, and EMP; to aspects of intra-system EMC associated with any type of coupling to explosive circuits; and with effects caused by RF transmissions. For Navy and Army aircraft, margins are applied to other aspects of intra-system EMC. Generally, margins are not applicable to the section 5.2.3 powerline transient requirement. Verification has been limited to analysis for the other aspects where testing is impractical.

Margins need to be viewed from the proper perspective. The use of margins simply recognizes that there is variability in manufacturing and that requirement verification has uncertainties. The margin ensures that every produced system will meet requirements, not just the particular one undergoing a selected verification technique. Smaller margins are appropriate for situations where production processes are under tighter controls or more accurate and thorough verification techniques are used. Smaller margins are also appropriate if many production systems undergo the same verification process, since the production variability issue is being addressed. Margins are not an increase in the basic defined levels for the various electromagnetic environments. The most common technique is to verify that electromagnetic and electrical stresses induced internal to the system by external environments are below equipment strength by at least the margin. While margins can sometimes be demonstrated by performing verification at a level in excess of the defined requirement, the intent of the margin is not to increase the requirement.

The 16.5 dB margin specified for safety assurance for ordnance is derived from the criterion in MIL-STD-1385 (superseded by this document) that the maximum allowable induced level for electrically initiated devices (EIDs) in required environments is 15% of the maximum no-fire current. The ratio of no-fire to allowable currents in decibels is 20 log (0.15) or - 16.5 dB. The requirement is expressed in decibels so that the requirement can be applied to ordnance designs which do not use conventional hot bridgewire EIDs and where no-fire current may be meaningless. MIL-STD-1385 also indicated a 6 dB margin for ordnance when there are consequences other than safety.

Hot bridgewire EIDs with a one amp/one watt MNFS are often used in ordnance applications to help in meeting safety requirements. As an alternative to using large sample sizes to demonstrate that the statistical criteria contained in the definition of MNFS (no more than 0.1% firing with a confidence level of 95%) is met, the methods of MIL-I-23659 can be used to define a one amp/one watt MNFS.

MNFS values for ordnance are normally specified by manufacturers in terms such as DC currents or energy. Margins are often demonstrated with respect to observed effects (such as the temperature rise of bridgewires) during the application of electromagnetic environments relative to effects observed by applying a stimulus level in the form under which the MNFS is defined (such as DC current level related to the required margin). The space community has elected to use MNFS levels determined using RF rather than DC. This approach is based on Franklin Institute studies, such as report F-C2560. Outside of the space community, the use of DC levels has provided successful results.

Margins are closely linked to both design and verification since the planned verification methodology influences the size of the margin and the resulting impact on the required robustness of the design. The specific margin assigned for a particular design and environment is an engineering judgment. If the margin is too large, then penalties in weight and cost can be inflicted on the design. If the margin is too small, then the likelihood of a undesirable system response becomes unacceptably high.

The size of the margin assigned is inversely proportional to the inherent accuracy of the verification method employed. One method of verifying lightning protection is to expose an operational aircraft to a simulated severe lightning encounter (most severe flashes with worst case attachment points). With this relatively accurate method of verification, a smaller overall margin should be required. Another method of verifying lightning protection is the use of low-level pulsed or continuous-wave (CW) testing with extrapolation of measured induced levels on electrical cabling to a full scale strike. These levels are then either applied to the cables at the system level or compared to laboratory data. This type of approach would typically require an overall margin of 6 dB. Similar margins may be appropriate for pure analysis approaches which produce results which have been shown by previous testing to be consistently conservative for the particular type of system being evaluated.

The least accurate verification method is the use of an analysis which has not been previously verified as yielding "accurate" results for the system type of interest. The term "previously verified" in this case means that the analysis is based on accepted principles (such as previously documented in E3 handbooks) but the particular system configuration presented for certification has not been previously tested to verify the accuracy of the analysis. For this case, margins as large as 30 dB are not unrealistic.

For most approaches, margins typically fall in the range of 6 to 20 dB. For equipment that is not classified as safety critical, mission critical, or ordnance, it may be desirable to use a reduced (possibly zero) margin to conserve program resources.

Requirement Lessons Learned (A5.1): The use of margins in verifying intra-system EMC requirements among subsystems by test has been attempted in the past; however, this practice has largely been abandoned except for electroexplosive circuits. A basic difficulty existed in the lack of available techniques to evaluate how close a circuit is to being upset or degraded. With the numerous circuits on most platforms, it can be a formidable task to evaluate all circuits. One technique that has been used is to identify the circuits through analysis which are potentially the most susceptible. The intentional signal being transmitted across the electrical interface is reduced in amplitude the required number of dB to decrease the relative level of the intentional signal to whatever interference is present. However, there is some controversy in this type of testing since the receiving circuit does not see its normal operating level. Margins for EIDs have been commonly demonstrated using techniques such as electro-optics, infrared, current probes, thermocouples, RF detectors, and temperature sensitive waxes.

Verification Rationale (A5.1): To obtain confidence that the system will perform effectively in the various environments, margins must be verified. In addition to variability in system hardware, test and analysis involve uncertainties which must be taken into account when establishing whether a system has met its design requirements. These uncertainties include instrumentation tolerances, measurement errors, and simulator deficiencies (such as inadequate spectral coverage).

Verification of margins for space and launch vehicles is essential since these items are costly and must meet performance the first and only time. There are no on-orbit repairs.

Verification Guidance (A5.1): Some uncertainties, such as system hardware variations or instrumentation errors, may be known prior to the verification effort. Other uncertainties must be evaluated at the time of a test or as information becomes available to substantiate an analysis. Margins must be considered early in the program so that they may be included in the design. It is apparent that better verification techniques can result in leaner designs, since uncertainties are smaller. Caution must be exercised in establishing margins so that the possible lack of reliable or accurate verification techniques does not unduly burden the design.

During an E3 test, the contribution to uncertainties from the test are either errors or variations. The errors fall into categories of measurement, extrapolation (simulation), and repeatability. Variations are caused by various issues such as system orientation with respect to the incident field, polarization of the incident field, and different system configurations (such as power on/off, refuel, ground alert). The contributions of errors and variations are combined for margin determination. They can be directly added; however, this approach will tend to produce an overly conservative answer. The more common approach is to combine them using the root-sum-square.

Verification Lessons Learned (A5.1): An example of margin demonstration used during verification of lightning indirect effects and electromagnetic pulse protection is the demonstration that the electrical current levels induced in system electrical cables by the particular environment are less than the demonstrated equipment hardness at least by the margin. This verification is generally accomplished by a combination of tests and analyses. The equipment hardness level is generally demonstrated in the laboratory during testing in accordance with MIL-STD-462. Testing can also be performed on individual equipment items at the system-level. There are some concerns with induced transient waveforms determined at the system-level being different than those used during equipment-level testing. Analysis techniques are available for waveform comparison such as norm attributes. Test techniques are available to inject measured current waveforms into electrical cables at amplified levels during a system-level test.

A5.2 Intra-system electromagnetic compatibility (EMC). The system shall be electromagnetically compatible within itself such that system operational performance requirements are met. Compliance shall be verified by system-level test, analysis, or a combination thereof.

Requirement Rationale (A5.2): It is essential within a system that the subsystems and equipment be capable of providing full performance in conjunction with other subsystems and equipment which are required to operate concurrently. EMI generated by a subsystem or other subsystems and equipment must not degrade the overall system effectiveness.

Electromagnetic compatibility among antenna-connected subsystems (termed RF compatibility on some programs) is an essential element of system performance. Inability of an antenna-connected subsystem to properly receive intentional signals can significantly affect mission effectiveness. Achieving compatibility requires careful, strategic planning for the placement of receiver and transmitter antennas on the system and on the interoperability of the subsystems

Requirement Guidance (A5.2): Intra-system EMC is the most basic element of E3 concerns. The various equipment and subsystems are designed and integrated to coexist and to provide the operational performance required by the user. However, varying degrees of functionality are necessary depending upon the operational requirements of individual items during particular missions. Certain equipment may not need to be exercised at the time of operation of other equipment. For this situation, intra-system compatibility requirements do not necessarily apply. The procuring activity and system user should be consulted to determine the required functionality. An example of these circumstances is that it is unlikely that an aircraft instrument landing system needs to be compatible with a radiating electronic warfare jamming subsystem during precision approaches. However, they need to be compatible during other operations such as when BIT is exercised.

Requirement Lessons Learned (A5.2): When appropriate controls are implemented in system design, such as hardening, EMI requirements on subsystems and equipment, and good grounding and bonding practices, there are relatively few intra-system EMC problems found. Most problems that are found involve antenna-connected transmitters and receivers. Receiver performance has been degraded by broadband thermal noise, harmonics, and spurious outputs coupled antenna-to-antenna from transmitters. Microprocessor clock harmonics radiating from system cabling and degrading receivers have been another common problem. Electromagnetic fields radiated from onboard antennas have affected a variety of subsystems on platforms. Typical non-antenna-related problems have been transients coupled cable-to-cable from unsuppressed inductive devices and power frequencies coupling into audio interphone and video signal lines. Problems due to cable-to-cable coupling of steady state noise and direct conduction of transient or steady state noise are usually identified and resolved early in the development of a system.

Generation of broadband EMI on ships from electrical arcing has been a common source of degradation of antenna-connected receivers and must be controlled. Sources of the arcing have been brush noise from electrical machinery and induced voltages and currents between metallic items from antenna transmissions. Intermittent contact of the metallic items due to wind or ship motion is a contributor. MIL-STD-1605 provides guidance on controlling and locating sources of broadband EMI.

An effective software tool for antenna-to-antenna coupling analysis on aircraft available through the Joint Spectrum Center is AAPG (Antenna inter-Antenna Propagation with Graphics). AAPG models the aircraft with a combination of cylinders or truncated cylinders and flat plates to estimate isolation between antennas as a function of free-space loss and shading by the fuselage and wings. Isolation in conjunction with the other parameters allows a first estimate of interference levels between subsystems. AAPG considers all signals as continuous; the program does not account for the effects of pulsed RF. Also, blanking is not considered in AAPG. Limitations of any analysis program must be considered when using the results to draw conclusions.

A common problem in systems occurs when the system uses both ECM (electronic countermeasures) and radar equipment operating at overlapping frequencies. The following measures may be helpful to provide RF compatibility between these types of subsystems: blanking, pulse tagging, utilization of coherent processing dead time, band splitting, and digital feature extraction. A blanking matrix is commonly used to depict the relationship between source and victim pairs.

A relatively new technique to attenuate an interfering signal at a receiver is frequency cancellation. This technique samples the interfering signal separate from the receiver's antenna, performs a phase inversion, and adds the result to the overall received signal. Thus, the interfering signal can be reduced substantially leaving the desired received signal essentially unaffected. The hardware to perform this action is complex and expensive.

Verification Rationale (A5.2): Verification of intra-system electromagnetic compatibility through testing supported by analysis is the most basic element of demonstrating that E3 design efforts have been successful.

Verification of RF compatibility by test is essential to ensure an adequate design which is free from the degradation caused by antenna-to-antenna coupled interference. Prior analysis and equipment-level testing are necessary to assess potential problems and to allow sufficient time for fixing subsystem problems.

Verification Guidance (A5.2): Although analysis is an essential part of the early stages of designing or modifying a system, testing is the only truly accurate way of knowing that a design meets intra-system EMC requirements. An anechoic chamber is usually required for system-level testing to minimize reflections and ambient interference that can degrade the accuracy of the testing and to evaluate modes of operation that are reserved for war or are classified.

The following list provides guidance on issues which should be addressed for intra-system EMC testing:

a. Potential interference source versus victim pairs should be systematically evaluated by exercising the subsystems and equipment onboard the system through their various modes and functions while monitoring the remaining items for degradation. Both one source versus a victim and multiple sources versus a victim conditions need to be considered.

b. A frequency selection plan should be developed for exercising antenna-connected transmitters and receivers. This plan should include:

1). Predicable interactions between transmitters and receivers such as transmitter harmonics, intermodulation products, other spurious responses (such as image frequencies), and cross modulation. The acceptability of certain types of responses will be system dependent.

2). Evaluation of transmitters and receivers across their entire operating frequency range, including emergency frequencies.

3). Evaluation of electromagnetic interference emission and susceptibility issues with individual subsystems.

c. Margins should be demonstrated for explosive subsystems and other relevant subsystems.

d. Operational field evaluation of system responses found in the laboratory environment should be performed (such as flight testing of an aircraft to assess responses found during testing on the ground).

e. Testing should be conducted in an area where the electromagnetic environment does not affect the validity of the test results. The most troublesome aspect of the environment is usually dense utilization of the frequency spectrum, which can hamper efforts to evaluate the performance of antenna-connected receivers with respect to noise emissions of other equipment installed in the system.

f. Testing should include all relevant external system hardware such as weapons, stores, provisioned equipment (items installed in the system by the user), and support equipment.

g. It should be verified that any external electrical power used for system operation conforms with the power quality standard of the system.

Operational testing of systems often begins before a thorough intra-system electromagnetic compatibility test is performed. Also, the system used for initial testing is rarely in a production configuration. The system typically will contain test instrumentation and will be lacking some production electronics. This testing must include the exercising and evaluation of all functions that can affect safety. It is essential that aircraft safety-of-flight testing be done to satisfy safety concerns prior to first flight and any flight thereafter where major electrical and electronic changes are introduced.

A common issue in intra-system EMC verification is the use of instrumentation during the test. The most common approach is to monitor subsystem performance through visual and aural displays and outputs. It is usually undesirable to modify cabling and electronics to monitor signals to assess subsystem performance, since these modifications may change subsystem responses and introduce additional coupling paths. However, there are some areas where instrumentation is important. Demonstration of margins for critical areas normally requires some type of monitoring. For example, EIDs require monitoring for assessment of margins.

Some antenna-connected receivers, such as airborne instrument landing systems and identification of friend or foe, require a baseline input signal (set at required performance levels) for degradation to be effectively evaluated. Other equipment which transmits energy and evaluates the return signal, such as radars or radar altimeters, need an actual or simulated return signal to be thoroughly assessed for potential effects.

The need to evaluate antenna-connected receivers across their operating ranges is important for proper assessment. It has been common in the past to check a few channels of a receiver and conclude that there was no interference. This practice was not unreasonable in the past when much of the potential interference was broadband in nature, such as brush noise from motors. However, with the waveforms associated with modern circuitry such as microprocessor clocks and power supply choppers, the greatest chance for problems is for narrowband spectral components of these signals to interfere with the receivers. Therefore, it is common practice to monitor all antenna-connected outputs with spectrum analysis equipment during an intra-system electromagnetic compatibility test. Analysis of received levels is necessary to determine the potential for degradation of a particular receiver.

Output characteristics of spread spectrum transmitters present unique technical issues which need to be addressed to achieve EMC.

RF compatibility between antenna-connected receivers is an element of intra-system electromagnetic compatibility and demonstration of compliance with that requirement needs to be integrated with these efforts. Any blanking techniques required for EMC should be included.

Verification Lessons Learned (A5.2): Performance degradation of antenna-connected communication receivers cannot be effectively assessed by simply listening to open channels as has been done commonly in the past. Squelch break has often been used as the criteria for failure. There are number of problems with this technique.

The most common receiver degradation being experienced is from microprocessor clock harmonics radiating from cabling. These signals are narrowband and stable in frequency. Considering a receiver designed to receive amplitude modulated (AM) signals, there are several responses that may be observed as discussed below. Similar analysis is applicable to other type receivers.

If an intentional signal above the squelch is present, the type of degradation is dependent on the location of the interfering signal with respect to the carrier. If the interfering signal is within a few hundred hertz of the carrier, the main effect will probably be a change in the automatic gain control (AGC) level of the receiver. If the interfering signal is far enough from the carrier to compete with the sideband energy, much more serious degradation can occur. This condition gives the best example of why squelch break is not an adequate failure criterion. AM receivers are typically evaluated for required performance using a 30%-AM, 1-kHz tone which is considered to have the same intelligibility for a listener as typical 80%-AM voice modulation. The total power in the sidebands is approximately 13 dB below the level of the carrier. Receiver specifications also typically require 10 dB (signal plus noise)-to-noise ratios during sensitivity demonstrations. Therefore, for an interfering signal which competes with the sidebands not to interfere with receiver performance, it must be approximately 23 dB below the carrier. An impact of this conclusion is that an interfering signal which is well below squelch break can cause significant range degradation in a receiver. If squelch break represents the true sensitivity required for mission performance, an interfering signal just below squelch break can cause over a 90% loss in potential range.

If no intentional signal is present and there is insignificant AM on the clock harmonic, the main result is a quieting of the receiver audio output due to AGC action. To an observer, this effect might actually appear to be an improvement in receiver performance. If some AM is present at audio passband frequencies, a signal will be apparent that is dependent on the depth of the AM; however, the degree of receiver degradation cannot be effectively assessed since it is masked by the AGC.

Two acceptable methods of assessing degradation are apparent. A 30% AM signal can be radiated at each channel of interest at an induced level at the receiver which corresponds to the minimum required performance. Changes in intelligibility can be assessed with and without the interference present. Also, the level of the signal source can be varied and the resultant effects evaluated. Due to the large number of channels on many receivers (UHF receivers (225 - 400 MHz) typically have 7000 channels), this technique may often not be practical. An increasingly popular approach is to monitor antenna-induced signal levels with a spectrum analyzer. A preamplifier is usually necessary to improve the noise figure of the analyzer and obtain adequate sensitivity. The received levels can then be easily assessed for potential receiver degradation. This technique has been found to be very effective. Use of a spectrum analyzer is also helpful for RF compatibility assessment.

Other than for EIDs, margin assessment is practical in several areas. Margins can be assessed for antenna-connected receivers using the spectrum analyzer technique described above. Another area where margin evaluation is practical is potential degradation of subsystems due to electrical cable coupling from electromagnetic fields generated by on-board antenna-connected transmitters. Intra-system compatibility problems due to communication transmitters, particularly HF (2-30 MHz), are fairly common. The induced levels present in critical interface cables can be measured and compared to demonstrated hardness levels from laboratory testing in the same manner as described in the appendix under section 5.3 for inter-system EMC.

System-level testing should be a final demonstration that RF compatibility has been obtained. It should not be a starting point to identify areas requiring fixes. Previous analysis and bench testing should resolve compatibility questions beforehand.

Active signal cancellation techniques present a risky approach to EMC and should be rigorously tested before being implemented. This approach is most sensitive to signal phase error and may actually worsen an interference problem by injecting phase noise resulting from a changing multi-path situation (due to aircraft stores load, release, and so forth).

A5.2.1 Hull generated intermodulation interference (IMI). For surface ship applications, the above requirement is considered to be met when the 19th product order and higher of IMI generated by High Frequency (HF) transmitters installed onboard ship are not detectable by antenna-connected receivers onboard ship. Compliance shall be verified by test, analysis, or a combination thereof, through measurement of received levels at system antennas and evaluation of the potential of these levels to degrade receivers.

Requirement Rationale (A5.2.1): In general, control of IMI in systems is covered by the language of section 5.2 requiring intra-system electromagnetic compatibility. Because of difficulty on ships with limiting IMI produced by HF transmitters, only higher order intermodulation products must be controlled to permit effective use of the spectrum. Issues with lower order products are addressed through frequency management.

Requirement Guidance (A5.2.1): The large number of HF transmitters, output power of the transmitters, and construction materials and techniques used on ships make the presence of IMI a reality. Electromagnetic fields from HF transmissions induce current flow in the ships hull. The various currents from different transmitters mix in non-linearities within the hull (termed the "rusty bolt effect") to produce signals at sum and difference frequencies of the fundamental and harmonic frequencies of the incident signals (F3 = + n1F1 n2F2 + ...; n1, n2, ... are integers). The order of the IMI is the sum of the n terms. The mixing of a fundamental with a fourth harmonic produces a fifth order IMI.

Requirement Lessons Learned (A5.2.1): Experience has shown that controlling 19th order and higher IMI provides frequency management personnel with sufficient flexibility to effectively manage the spectrum.

Verification Rationale (A5.2.1): Test and associated analysis are the only effective means to verify IMI requirements.

Verification Guidance (A5.2.1): Guidance on evaluating IMI is available through the Ship EMC Improvement Program (SEMCIP) technical assistance network. Access to the data base can be obtained by contacting the Naval Surface Warfare Center, Code J54, Dahlgren, VA (Commercial phone 540-653-8021, military phone DSN 249-8021).

Verification Lessons Learned (A5.2.1): Testing, supported by analysis, has proven to be an effective tool in evaluating IMI.

A5.2.2 Shipboard internal electromagnetic environment (EME). For ship applications, electric fields (peak V/m-rms) below deck from intentional onboard transmitters shall not exceed the following levels:

a. Surface ships.

(1). Metallic: 10 V/m from 10 kHz to 18 GHz.

(2). Non-metallic: 10 V/m from 10 kHz to 2 MHz, 50 V/m from 2 MHz to 1 GHz, and 10 V/m from 1 GHz to 18 GHz.

b. Submarines. 5 V/m from 10 kHz to 1 GHz.

Compliance shall be verified by test of electric fields generated below deck with all antennas (above and below decks) radiating.

Requirement Rationale (A5.2.2): Specific controls must be imposed to limit internal electromagnetic fields for ship applications to ensure that the variety of electronic equipment used onboard ships will be able to function with limited risk of performance degradation. This approach is partially due to the methodology by which equipment is installed on ships. For system applications other than ships, it is generally the responsibility of the system integrator to ensure that fields internal to the system are controlled to levels consistent with immunity characteristics of installed equipment.

Requirement Guidance (A5.2.2): Many types of electronic equipment are used on ships which have not been designed to be used in higher level electric field environment. Most predominant in this group are NDI and commercial items. Therefore, the EME must be controlled to provide a level of assurance that the equipment will operate properly.

Requirement Lessons Learned (A5.2.2): Compatibility problems have been experienced with electronic equipment due to inadequate control of field coupling below deck.

Verification Rationale (A5.2.2): Testing is the only reliable method to determine the coupled EME to a reasonable level of certainty.

Verification Guidance (A5.2.2): Testing needs to be performed with frequency selective receivers (spectrum analyzer or EMI receiver) and appropriate antennas such as those used in Test Method RE102 of MIL-STD-462. Broadband omnidirectional E-field sensors, such as those used in Test Method RS103 of MIL-STD-462D, can be used to search for areas of higher fields. Since these devices are broadband, they will detect the resultant E-field from all sources present within the bandpass of the device. The dominant source of the reading may not be obvious. Also, since these devices do not use the peak detection function present in spectrum analyzers and EMI receivers, indicated levels may be well below actual peak levels, particularly for pulsed fields.

Verification Lessons Learned (A5.2.2): Measurements of the electric fields below deck is the only means of verifying compliance with the internal EME requirements.

A5.2.3 Powerline transients. For Navy aircraft and Army aircraft applications, electrical transients of less than 50 microseconds in duration shall not exceed +50 percent or -150 percent of the nominal DC voltage or +50 percent of the nominal AC line-to-neutral rms voltage. Compliance shall be verified by test.

Requirement Rationale (A5.2.3): Electrical transient levels produced by utilization equipment on prime power busses need to be maintained below levels required to protect other equipment from potential upset or damage.

Requirement Guidance (A5.2.3): Power quality standards, such as MIL-STD-704 for aircraft and MIL-STD-1399 for ships, control the supply voltage for utilization equipment within specified limits. The voltage is maintained at a monitoring location termed the "point of regulation (POR)" with allocation for allowable voltage drops beyond the POR to the input of utilization equipment. MIL-STD-704 does not include provisions for the control of transients less than 50 microseconds in duration. Also, MIL-STD-461D no longer includes a transient emission requirement. Each equipment using power needs to control transients to levels that will not cause upset or damage to other power users. The requirement applies from the base of the transient on the normal power waveform to the peak of the transient.

Transient requirements for applications other than Navy aircraft and Army aircraft are either covered by other types of control requirements or are considered to be unnecessary. For example, ship requirements are addressed in MIL-STD-1399, Section 300. The Air Force does not impose the above requirement for aircraft because they have not experienced problems from direct conduction of faster transients between subsystems over the power buses and consider the imposed levels to be much too severe for Air Force applications. Power interfaces for avionics are typically quite robust and standard electromagnetic interference requirements impose significant immunity levels on avionics. The only direct conduction problems the Air Force has experienced on power busses is with longer-term, power surges.

Requirement Lessons Learned (A5.2.3): Powerline transients have caused unresettable upsets to the primary attitude reference system of a Navy fighter aircraft degrading weapons control functions and requiring mission abort. Aircraft problems have occurred on Air Force aircraft from coupling of transients from unsuppressed inductive devices onto signal interface lines. However, whenever transient levels on the power buses are investigated, the levels present are often insignificant. The general observation has been that voltage levels on the power waveform near an unsuppressed source may be high, but away from the source and on the power bus side of the switching device, the levels are much lower.

Verification Rationale (A5.2.3): Testing is the only viable approach to determine actual transient levels.

Verification Guidance (A5.2.3): Powerline transients should be measured on each power bus during power-on and power-off sequencing, mode switching of equipment, and power bus switching. These measurements should be performed at a the power distribution point. Due to the high frequency impedance effects and other losses on the power bus, measurements of any significant transients that are detected should be repeated as close to the other utilization equipment as possible to determine if the level at the equipment exceeds the limits.

Verification Lessons Learned (A5.2.3): Not applicable.

A5.2.4 Multipaction. For space applications, equipment and subsystems shall be free of multipaction effects. Compliance shall be verified by test and analysis.

Requirement Rationale (A5.2.4): It is essential that RF transmitting equipment and signals not be degraded by the action of multipaction. It is essential that multipaction not result in spurious signals that interfere with receivers.

Requirement Guidance (A5.2.4): Multipaction is an RF effect that happens strictly in a high vacuum. An RF field accelerates free electrons resulting in collisions with surfaces creating secondary electrons. These are accelerated resulting in more electrons leading to a major discharge and possible equipment damage. The guiding document for multipaction analysis is NASA TR 32-1500.

Requirement Lessons Learned (A5.2.4): Connectors, cables, and antennas have all been involved in multipaction incidents. Sometimes, the application of insulators on antennas or a vent in connectors is sufficient to limit multipaction or damage. In some cases, transmitted signal strength has been severely impacted. Multipaction in RF amplifier circuitry has been implicated in semiconductor and insulator degradation.

Verification Rationale (A5.2.4): Multipaction is a resonant phenomenon in the dimensions of frequency and power. An increase in power may well reduce the probability of multipaction. Analysis is absolutely necessary to determine how margin is shown. Since multipaction can show flaws in machining and dielectrics that no other test will indicate, testing also must be performed.

Verification Guidance (A5.2.4): All components experiencing RF levels in excess of 5V need to be tested for multipaction. The test equipment must provide adequate power and transient levels to show margin with respect to the operating state. VSWR measurements provide a crude method of detecting multipaction; however, it is better to detect free electrons or changes in harmonic emissions.

Verification Lessons Learned (A5.2.4): For multipaction to occur, seed electrons must be present. In space, these electrons are provided by radiation. Some tests at sea level have shown no multipaction on components, while severe multipaction occurred in orbit. It is vital that a source of radiation or electrons be provided to get an accurate test. Some claim that some metals like aluminum are self seeding. However, since the effect is strongly dependent on surface treatment, aluminum should not be depended upon to be self seeding.

A5.3 Inter-system EMC. The system shall be electromagnetically compatible with its defined external EME such that its system operational performance requirements are met. For systems capable of shipboard operation, Table IA shall be used. For space and launch vehicle systems applications, Table IB shall be used. For ground systems, Table IC shall be used. For all other applications and if the procuring activity has not defined the EME, Table ID shall be used. Inter-system EMC covers compatibility with, but is not limited to, EME's from like platforms (such as aircraft in formation flying, ship with escort ships, and shelter-to-shelter in ground systems), friendly emitters and hostile emitters. Compliance shall be verified by system, subsystem, and equipment level tests; analysis; or a combination thereof.

TABLE IA. External EME for systems capable of shipboard operations (including topside equipment and aircraft operating from ships) and ordnance