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

3. DEFINITIONS, ACRONYMS, AND ABBREVIATIONS

3.1 Definitions. For the purpose of this handbook, the following definitions apply. In addition to the terms below, many terms used in this handbook are defined in ANSI C63.14, JCS Pub. 1-02, DoDD 3222.3, DoDI 4650.01, or the DoD 5000 series of documents.

Bond. Any fixed union between two surfaces that result in electrical conductivity between the surfaces. The union occurs either from physical contact between conductive surfaces of the surfaces or from the addition of a firm electrical connection between them. For refueling/defueling purposes the bond is the conductive contact between the refueling apparatus and the aircraft.

Breech. The rear part of the bore of a gun, especially the opening and associated mechanism that permits insertion of a projectile.

Coulomb (C). The charge transported by a steady 1 ampere current in 1 second. Fibrillation. Fibrillation is the rapid, irregular, and unsynchronized contraction of muscle

fibers. An important occurrence is with the heart.

Friction. A force on objects or substances in contact with each other that resists motion of the objects or substances relative to each other.

Induced Charge. Induced charge is one that accumulates on an object when immersed in an electric field.

Lightning Grounds. Lightning grounds are grounds that have resistances lower than 1 ohm and frequently on the order of 2.5 milliohms or less. In, addition lightning grounds must be more robust than Static/ESD grounds so that they may conduct extremely high lightning-induced currents on the order of several thousands of amperes.

Ohm's Law. Ohm's Law states that the current through a conductor between two points is directly proportional to the potential difference (voltage) across the two points, and inversely proportional to the resistance between them.

Ordnance Ground. Ordnance grounds are static grounds typically found in magazines and ordnance handling areas.

Power Grounds. Power grounds are defined as those having resistances of less than 25 ohms referenced to the power system neutral. For further information on power grounds refer to individual system technical manuals and design documents, such as NAVFAC UFC 3-570-01.