MIL-HDBK-274 Electrical Grounding For Aircraft SafetyThis handbook has been prepared to provide U.S. Navy and Marine Corps aircraft maintenance and operations personnel with the background and technical details of the different types of aircraft grounds and how they are applied. In addition, this handbook provides background information for aircraft grounding, static electricity theory and how it affects aircraft, and techniques used for measurement of grounding points. This handbook is intended for use by all U.S. Navy and Marine Corps aircraft maintenance and operations personnel for the purposes of ensuring that aircraft are properly and safely grounded. This handbook is for guidance only and cannot be cited as a requirement.

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PARAGRAPH

4.6.3

CONTENTS

Range for reflex actions

PAGE

28

4.6.4

Equipment damage level

28

4.6.5

Summary of damage threshold levels

28

4.7

Analysis

28

4.7.1

Source magnitude and hazard threshold level

29

4.7.2

Time duration consideration

30

4.7.3

Hazards

30

4.7.4

Effects of grounding

31

5.

DETAILED GUIDANCE

31

5.1

Testing and identification of ground points (ashore)

31

5.2

Theoretical background

31

5.2.1

Earth's shell

33

5.2.2

Measuring ground points

33

5.2.3

Resistance of the ground rod

33

5.3

Measurement equipment

33

5.3.1

Null balance Earth tester

33

5.4

Ground point measurement procedures

35

5.4.1

Three-terminal fall of potential method

35

5.4.2

Two-terminal method (direct method)

35

5.5

Schedule for resistance testing of ground points

36

5.6

Identification of ground points

36

5.7

Use of mooring eyes as static ground points

36

5.7.1

Mooring eye installation details

36

5.7.2

Additional tie-down/grounding points

43

5.8

Resistance measurements for alternate grounding points

43

5.8.1

Test method for resistance measurements of alternate grounding points

43

5.9

Operational grounding overview

45

5.9.1

Operational procedures during ordnance handling

45

5.9.2

Temporary grounding

46

5.10

Grounding hardware/receptacle considerations

47

5.10.1

Use of alligator clips or braided panel strap

47

5.10.2

Grounding cable

47

5.11

Aircraft grounding methods

47

5.11.1

Grounding for shore-based and shipboard operations

47

5.11.2

Ordnance loading/downloading

48

5.11.3

Aircraft ground connections

48