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

4.4.3 Summary. In summary, the levels of electrostatic and power electrical energy sources considered are given in Table II.

TABLE II.  Summary of electrical energy sources.

4.5 Airframe/personnel electrical parameters. When energy sources are considered in terms of voltage or current, the electrical characteristics, for example, tire resistance to ground and airframe capacitance to ground are used to establish time duration and other parametric relationships.  Airframe electrical parameters interact with charge generation mechanisms and thereby establish the actual hazard levels and time duration for these hazards.  Airframe capacitance to Earth and airframe resistance to Earth are most relevant.  Capacitance establishes the total charge stored due to a particular potential and the time factor needed to dissipate the charge from a surface through a particular resistance.  Resistance establishes the voltage associated with known current flows and the time factor for charge reduction when the capacitance is known.  Resistance was found to be the more variable parameter.

4.5.l Electrostatic charge storage.  The ability of a body to store electrostatic charge is determined by the capacitance of that body.  The amount of charge that can be stored in a capacitor is expressed by the equation:

Equation:                                                                                                                                (6) Q = C·V

Where:

Q = amount of charge (in Coulombs)

C = capacitance of the body (in Farads)

V = voltage (in Volts) developed between the plates of the capacitor

The electrical resistance, R (in ohms), determines the rate at which the capacitor charges or discharges.

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