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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MIL-HDBK-274A

5.9 Operational grounding overview. This section provides information to understand the need for grounding.  This section discusses the grounding problems and hazards encountered in everyday ground handling of aircraft during maintenance and ordnance handling operations. Descriptions are given of static electricity, energy sources, and grounding effects.  Various aircraft scenarios are presented that involve safety related servicing situations, together with the approved methods of handling such problems.

5.9.1 Operational procedures during ordnance handling. The following paragraphs summarize grounding procedures performed during ordnance handling evolutions.

FIGURE 17.  MIL-DTL-83413/7-1 clamp.

Note:  Ensure that any area that the M83413/7-1 electrical ground connector (clamp type) is clamped to provides a good electrical connection.  This can be obtained by grinding the clamp teeth into the grounding point to ensure the connection is free of paint, corrosion and dirt.  This action enables metal to metal contact.  Connections to composite materials do not provide an acceptable ground.

5.9.1.1 Ordnance handling grounding procedures. The following paragraphs provide grounding considerations and procedures during ordnance handling operations.

5.9.1.1.1 Loading of ordnance.  During the loading/downloading of ordnance, the aircraft should be properly grounded.  Loading/downloading of ordnance cannot be conducted while external power is applied to the aircraft in accordance with the aircraft's applicable NAVAIR weapons/store loading checklist.

5.9.1.1.2 Tie-down chains.  Tie-down chains do not provide an acceptable ground.  A

new tie-down chain can have a resistance less than 0.5 ohm, and used chains have been measured at 5,000,000 ohms.  This is due to excessive corrosion, and this condition is not improved when the installed chain is being subjected to continuous movement when the ship is rolling and the weight of the aircraft is continuously transferring from one chain to another.

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